Part II. Production systems, welfare and product quality
Dairy cattle
J. Praks, V. Poikalainen, I. Veermäe
In Europe the main feed for dairy cattle is largely based on grass and stored forages, whereas in summer pasturing is used. At least a part of the year cattle are housed day and night. The indoor period lasts for 4 –8 months of the year depending on the geographic location. There is an increasing trend of housing cattle all-year-round.
Housing systems have an important role in the welfare of dairy cattle. The environment of livestock housing is devised and maintained by Man. Animals have little opportunity to control their environment. The impact of housing on the welfare of the cattle is versatile:
1) predisposition to different diseases in connection with different risk factors of indoor environment,
2) the impact of housing on behaviour (changes in social behaviour connected with closer contact, development of abnormal behaviour connected with inadequate space), restriction of movement etc.,
3) development of stress, caused by inadequate conditions of microclimate, housing, behaviour of the herdsperson etc.
To facilitate adaptation Man must create in the cowshed conditions suitable for animals (Phillips, 2002). Cattle can adapt to a variety of housing systems, e.g. they will tolerate being tethered individually, or existence in small or large groups. Proper housing and management promote adaptation and guarantee good welfare status for animals and provide an economic workable environment for stockpersons. Many types of housing systems are used for the milking herds. The two most common types are tied types and loose housing types of cowsheds.
Tied housing
Each cow stands in an individual stall and is fastened by a neck chain, milking and feeding (of roughage and concentrate) take place at the stall, grazing during the summer (Fig. 1). During the grazing period cows are brought into the stalls and tied for milking. After housing in autumn cows are tethered 24hr per day until turn-out in spring, which significantly restricts their freedom of movement and social contact.
Advantages of tied housing:
1) allows more individual attention to each cow,
2) easier to observe and treat each cow,
3) reduced spreading of certain infectious diseases such as Mortellaro,
4) reduced pain from lameness.

Disadvantages of the tied housing:
1) restriction of movement and behaviour (social contacts, body care etc.),
2) more labour and time needed,
3) more bedding needed. (Anonymous…, 2001)
Figure 1. Tied housing cowshed (Photo A. Nõmmeots)
In general cows are active during the daytime and rest at night. Their behaviour is synchronized. The behaviour of cows in tied housing cowsheds is determined by feeding and milking times. This regime forms noticeably disjunct behavioural patterns.
Daytime and night do not differ so clearly. Animals lay also in the daytime and it rarely happens that all cows are in the lying state at the same time.
In a typical large tied housing cowshed the difference between daytime and night-time, considering the cows’ resting behaviour and its synchronicity, is comparatively small (Aland et al.,
1999). The number of occurrences of conflicts and sympathy between neighbouring cows increased before the resting period, when animals were competing for places to recline (especially when the stalls partitions are fail). There were also more conflicts at the end of the eating period, when animals were competing for the remains of the feed. The “redistribution” of resources, contingent upon the hierarchy points to the incompleteness of the technology. The inadequacy of the tie-stall is reflected in the frequent occurrence of stereotypical activities (e.g., bar-biting, tongue-rolling), which disappear when the animals are transferred to loose housing or pasture (Kohn,1994).
Stalls in cowsheds are arranged in two or four rows. Stall design is very important, as dairy cows spend more than 50% of the day lying down. Stall design should take into

consideration the size of the animals. Critical factors, affecting the degree of comfort, are
1) the size of the stall,
2) the type and quality of the flooring,
3) the position and dimension of manger, tethers, drinkers, partitions.
The size of stalls must allow the cow to perform her natural movements when getting up and lying down so as to reduce the chance of injury. Inappropriate stall dimensions can reduce the cow’s lying time, which can predispose to lameness and teat damages. A comfortable stall permits the cow to stand normally with all four feet on the stall bed. There should be a downward slope from the front to the back (2 –
6%), which encourages the cow to lay head uphill. Recommended stall dimensions are brought in table 1. It is discussible whether these dimensions will allow optimum comfort. Allowing the cow too much space may result in problems of cleanliness.
Table 1 Recommended stall dimensions (Luts, 2002)
Young cattle
Body weight, kg
Age
(months)
Stall Walking area, m length, m width, m Dehorned
2 with horns
Cows
<200
300
400
>400
550
650
750
>6
9…12
12…18
>18
1.2 0.7
1.3 0.8
1.45 0.9
1.55
–1.65 1.0
–1.10
1.78 1.18
1.85
1.91
1.20
1.22
4
5
6
7
8
8
8
4
6
8
10
12
12
12
Optimal flooring should provide
1) adequate thermal insulation,
2) appropriate degree of softness,
3) appropriate degree of friction,
4) a low risk of abrasion,
5) be easy to maintain and clean (Nilsson, 1992).
Quite often the stall flooring is concrete. To improve the stall flooring quality, different bedding materials are used: geotextile and rubber-based mattresses, sawdust, straw.
Bedding makes the stall comfortable, decreasing stall refusal and reducing the potential for injuries.
The position and dimensions of mangers, tethers, drinkers and partitions can also affect cow comfort. These details of stalls must allow the cows to perform their natural behavioural patterns as standing up and laying down, eating, drinking etc.
The feed and water must be easy reach of the cow. Mangers that are flush with the floor of the stall increase the pressure that the cow exerts to the floor and on the bars when eating. Raising the bottom of the manger 20-25 cm above the floor level can halve the pressure (Rushen and de Passillé, 1999).

The purpose of stall partitions is to keep the animals perpendicular to the manger as much as possible and thus increase the possibilities to keep the cow clean, to avoid movements into the neighbouring stall and thus avoid disturbing each other but at the same time do not prevent the cow from performing normal standing up and laying down behaviour. There are wooden, plastic or metal partitions of different shapes and measurements taken in use. In the Swedish University of Agricultural Sciences the experiment was carried out with two types of partitions (I and λ types) (Fig. 2), made from elastic nylon straps and fixed to the ceiling and floor between the animals
(Aland, 19 96). It is concluded that these kinds of partitions (especially λ type) are more suitable for animals than iron or wooden ones because they are soft, and thus do not cause injuries while the animals are lying or standing against them, or when there are interactions between animals. They are also very easy to remove when removal of the partition is necessary.
Figure 2. I (A) and λ (B) type of partitions (Aland, 1996)
Loose housing
The trend towards fewer but larger herds, and to silage as the main forage, has led to the predominance of loose housing systems (loose housing on deep bedding, cubicle system or free stall cowshed). Cubicle systems are now the most common type of loose housing. As the cattle are protected from cold stress by the genesis of considerable amount of heat during digestion and metabolism, even in the Nordic countries uninsulated or so-called cold cowsheds have been built. Cold cowsheds are the ones where the internal temperature follows the outdoor temperature, depending on it, and varying by just a few degrees (MWPS-33, 1989). In loose housing cowsheds there are special areas for feeding and resting of animals. A free stall cowshed is a loose housing system in which stalls are provided for the cows but cows are not fastened in the stalls. They may enter and leave the stalls whenever they want to. The stalls are located in the resting area.
It is unclear what the maximum group size should be for dairy cow management systems. Herds of over 150 cows are often divided into groups of 50 –100 animals during indoor keeping. Dairy cattle quickly establish a social hierarchy within a group.

It is mostly linear, although it is usual for some triangles of dominance to occur within.
It is important that the herd is stable, because any interchange of cows between groups will upset the social hierarchy (Management and Welfare of Farm Animals,
1999). More popular feeding method is feeding a complete ration or totally mixed ration (TMR). It contains roughages and concentrates combined to meet the energy, protein, mineral, vitamin and crude fibre needs of the cows. The feed is available freely. In smaller cowsheds (up to 100 cows) quite often feeding of roughage takes place at feeding gate and concentrates at the milking parlour or in the automated concentrate feeder. Milking takes place in the milking parlour, no grazing in large cowsheds (more than 300 cows) (Fig.3).
Figure 3. Uninsulated free stall cowshed (Photo A. Nõmmeots)
No grazing at all may imply reduced welfare, as grazing is known to benefit claw health (less severe disorders and better recovery) and to reduce stereotypes and aggression in the herd. Cows may also prefer to rest in the pasture as compared to resting in cubicles. Solid concrete and slatted floors, especially when they are slippery, dirty, and wet, create a serious risk of injuries (Anonymous …, 2001).
Advantages:
1) low quantity of bedding required,
2) opportunity to use alternative bedding materials and mats which can further reduce usage of straw,
3) lower risk of environmental mastitis.
Disadvantages:
1) passageways and cubicle bases contaminated with slurry,
2) higher risk of lameness and leg damage (FAWC Report).

Cubicles should be as comfortable as possible to encourage maximum lying time.
Cows should lie in their stalls for 9-14 hours each day. Recommended dimensions for cubicles in loose housing system are given in table 2. When cows find their stalls uncomfortable, they show this in their behaviour:
1) cows sleep in the concrete alleys or in front of the feeders,
2) cows stand with only their front legs in the stall,
3) changes in the cow’s daily pattern of rest/activity, especially an increase in the amount of time spent standing inactive,
4) how the cows get up and lay down,
5) frequent hesitation before lying down, usually sniffing the ground.
(Rushen and de Passillé, 1999)
Table 2 Recommended dimensions for cubicles in loose housing system (Dairy
Housing, 1996)
Body weight, kg
360…540
540…680
>680
Width, m
1.06
1.14
1.21 side lunge, m
Length forward
1.98
2.13
2.28 lunge, m
2.28…2.43
2.43…2.59
2.59…2.74
Neck rail height, m
0.93
1.01
1.06
Brisket board, distance from curb
1.57
1.67
1.80
A longitudinal slope of two to six percent is recommended to encourage the cows to rest toward the rear of the stall (Feddes et al. Building for Cow Comfort). Stall alley should be 3.75 m, a feed and stall alley 4.25 m wide. Narrow alleys are an important cause of social confrontation. Concrete surfaces of alleys must be provided with grooves 1 cm deep to diminish slipperiness. A hexagonal pattern of grooves is better than parallel pattern. The accumulation of slurry in the passageways can predispose to foot problems. It is important to minimise the amount of slurry by scraping out at least twice a day.
Recommendations concerning access to water vary greatly (from 3 cm tank perimeter to 9.1 cm per cow).Typically, water is provided at each crossover in free stall cowsheds (Smith et al., 2002).
Loose housing cowshed on deep bedding
Characteristic traits for loose housing cowshed on deep bedding: more or less stable groups, straw-bedded lying area, milking in milking parlour, feeding roughage at feeding gate, concentrate in milking parlour or in automated concentrate feeder, grazing during summer, outdoor in winter.
Cows do not have an individual cubicle for lie, but they may lie everywhere on the rest area (Fig. 4). Straw yard system enables to handle manure in a solid form and to store it until spreading. But the straw requirement is high (5 –10 kg straw/per cow/per day). Using this system regular hoof wear is needed to prevent overgrowing. Space allowances per cow of bedded area depends of the animals’ size: for cows with body weight of 550 kg–5.6 m 2 , 650 kg –
6.1 m 2 , 750 kg –6.5 m 2 (Luts, 2002).

Figure 4. Loose housing cowshed on deep bedding (Photo V. Poikalainen)
Swedish investigations proved that the lowest total incidence of disease and injury occurred in the loose housing systems with soft bedding in the lying area and access to outdoors. The incidence of trampled teats and traumatic injuries of the udder was the lowest when the animals had soft bedding and maximum freedom of getting up and lying down (Ekesbo, 1966).
Advantages:
1) relatively low incidence of lameness,
2) less risk of damage to knees, hips and hocks.
Disadvantages:
1) large quantity of bedding required,
2) relatively high level of management,
3) higher risk of environmental mastitis,
4) feeding and loafing passageways contaminated with slurry (FAWC Report).

Aerial environment in animal housing
For housed animals the quality of air is very important because the animal’s organism is in continuous contact with the surrounding air in the cowshed. Ventilating system is used to control the microclimate in animals’ rooms. In cowsheds most often natural ventilation systems are used. Ventilating systems affect:
1) air temperature,
2) moisture level,
3) air speed,
4) gas concentrations,
5) airborne dust and pathogens level.
The effect of temperature on dairy cows
Farm animals try to maintain a constant body temperature. Air temperature, relative humidity and air velocity are important factors of animal heat exchange. Cattle are more temperature tolerant than other farm animals. Their thermoneutral zone is generally wide, and often extends to much lower temperatures. Exceptions are neonate and young animals, sick or underfed animals, animals exposed to high air speeds or which have wet coats (Fig. 5, Table 3). The range of thermal neutrality is variable between breeds and between cows with different productivity .
Figure 5 Simplified schematic representation of co ws’ thermoregulation and zones of environmental temperature (Hafez, 1968; Poikalainen, 1999)
RA – zone of homeothermy, OP – zone of thermal comfort, KZ – zone of thermoneutralty, CS – cold stress, HS – heat stress, HO – hypothermia, HR – hyperthermia, T
1
- lower limit of zone of homeothermy, T
2
– lower critical

temperature of the thermoneutral zone, T
3
- upper critical temperature of the thermoneutral zone, T
4
- upper limit of zone of homeothermy)
When environmental temperatures move out of the thermoneutral zone (or comfort zone) dairy cattle begin to experience either heat stress or cold stress. Either stress requires the cow to increase the amount of energy used to maintain the body temperature and there is less energy available to produce milk. Thermoneutral zone is the range of environmental temperatures where normal body temperature is maintained and heat production is at the basal level. The ranges of thermoneutral zone are from lower critical temperature (LCT) to upper critical temperature (UCT).
LCT is the environmental temperature at which an animal needs to increase metabolic heat production to maintain body temperature. UCT is the environmental temperature at which the animal increases heat production as a consequence of a rise in body temperature resulting for inadequate evaporative heat loss (Yousef,
1985). Thermoneutral zone depends on the age, breed, feed intake, diet composition, previous state of temperature acclimatization, production, housing and stall conditions, tissue (fat, skin) insulation and external (coat) insulation, and the behaviour of the animal. UCT is given as 2526 ºC, LCT as a range from -16 to -37
ºC for dairy cows (Berman et al., 1985; Hamada, 1971). LCT for newborn calves is
10 ºC in dry and draught-free environment. LCT decreases to 0 ºC by the time the calf is 1 month old.
Factors affecting the lower critical temperature:
1. The rate of heat production (feed intake, digestibility of the feed, the level of production, the efficiency of utilization of ME), the amount of activity and locomotion.
2. The rate of heat loss. Heat loss is affected by coat thickness, coat thermal insulation, tissue insulation, the minimal rate of evaporative heat loss, irradiative environment. Coat insulation is affected by wetness and air speed.
(Wathes and Charles, 1994).
According to Radostits and Blood (1985), critical temperatures for cattle are:
1) calf (4 l milk per day) LCT 13 ˚C, UCT 26 ˚C,
2) calf (50 –200kg) –5˚C …26 ˚C,
3) cow (dry and pregnant) –14 ˚C…25 ˚C,
4) cow (peak lactation) –25 ˚C …25 ˚C.
The common opinion is that the neutral air temperature for European breeds of dairy cows is about –5 ˚C...25 ˚C (Management and Welfare of Farm Animals, 1999). The recommended relative humidity in cowsheds is 70

10%.

Table 3.
Influence of air speed on lower critical temperature (LCT) and heat production of cattle (Webster, 1981)
Heat LCT ˚C
Animals Body weight production
W/m 2
V=0.2 m/s
V=2.0m/s
Newborn calves
Pre-ruminant
(1m) calves
35
50
100
120
9
0
17
9
Calves
Heifers
Beef cows
Dairy cows
100
250
450
500
154
157
107
154
-14
-32
-17
-26
-1
-20
-9
-13
Temperature-humidity index (THI) could be used as an indicator of thermal climatic conditions. THI is determined by equation from the relative humidity and the air temperature and is calculated for a particular day according to the following formula
(Kadzere et al., 2002):
THI=0.72 (W+D) +40.6
Where W – wet bulb temperature ºC
D – dry bulb temperature ºC
The principle of THI is that as the relative humidity at any temperature increases, it becomes progressively more difficult for the animal to cool itself. (RCI Technical
Information. The influence of temperature humidity index on cow performance). THI values of 70 or less are considered comfortable, 75 – 78 stressful, values greater than 78 cause extreme stress.
Heat stress
Heat stress for the dairy cow can be understood to indicate all high temperaturerelated forces that induce adjustments occurring from the sub-cellular to the whole animal level to help the cow avoid physiological dysfunction and for it to better fit its environment (Kadzere et al., 2002).
Signs of heat stress
1. Restlessness;
2. Crowding under shade or at water tanks;
3. Panting (open-mouthed breathing);
4. Increased salivation;
5. Increased respiration rate (gasping);
6. Rates of gut and ruminal motility are reduced;
7. Lethargy;
8. Decreased activity;
9. Reduced feed intake.

Under continuous heat stress lactating cows begin to show a decline in the intake at
2527 ºC with a marked decline of 40% above 30 ºC (RCI Heat stress in dairy cattle).
Increased sweating
In dairy cows two types of sweating can be distinguished: both are involved in heat dissipation. The first type is insensible sweating or perspiration that leaves the body at all times, unless the relative humidity is 100%. The other type, thermal sweating, occurs as the principle evaporative cooling mechanism of the cow when the ambient temperature rises.
Rise of rectal temperature
Rectal temperature is an indicator of thermal balance and may be used to assess the adversity of the thermal environment. In severe cases of heat stress rectal temperature rises. The effect is increased when the relative humidity is greater than
50%. A rise of 1 ºC or less is enough to reduce performance in most livestock species (McDowell et al., 1976).
Reduced heart rate
Initial increase in heart rates slows down when the heat stress persists. Reduced heart rate is more typical in heat-stressed cows as it is associated with the reduced rate of heat production as a response to high environmental temperatures.
Declined feed intake
Feed intake in lactating cows begins to decline at the ambient temperatures of 25-26
ºC and drops more rapidly at above 30 ºC. At 40 ºC, dietary intake may decline by as much as 40% (National Research Council, 1989). Heat stress in high producing lactating dairy cows results in considerable reductions in roughage intake and rumination. The reduction in appetite under heat stress is a result of elevated body temperature and may be related to gut fill (Silanikove, 1992).
Increased water intake
Heat stress increases water consumption by at least five times the normal level in temperate zones. Water and macro-mineral needs, influenced heavily by demands to maintain homeostasis and homeothermy, are altered for lactating dairy cows during heat stress. Milk is about 87% water, and contains large concentrations of the electrolytes Na, K, and CI. Therefore, lactating dairy cows have large turnover of water and these electrolytes (Shalit et al., 1991).
Drop in daily milk production
It is accepted that heat stress is the major cause of lost production in dairy cattle in hostile regions. Some authors reported decline in the production of milk and fat as a

direct result of high environmental temperatures. This may be explained by the negative effects the heat stress has on the secretory function of the udder
(Silanikove, 1992). Some authors suggested that milk production is reduced 15%, accompanied by a 35% decrease in the efficiency of energy utilization for productive purposes, when a lactating Holstein cow is transferred from an air temperature of 18 to 30 ºC. Milk fat, solids-not-fat, and milk protein percentage decreased 39.7, 18.9 and 16.9% respectively (quoted by Kadzere et al., 2002).
Metabolic responses
Under heat stress metabolism is reduced, which is associated with reduced thyroid hormone secretion and gut motility, resulting in increased gut fill. Plasma growth hormone concentration and secretion rate declines with hot temperature (35 ºC).
Ruminal pH is typically lower in heat stressed cattle (quoted by Kadzere et al., 2002).
There are great changes in dietary electrolyte balance and acid/base balance associated with heat stress. The major electrolytes involved in dietary electrolyte balance are Na + , K + , CL ¯ and the buffer HCO
3
¯ . S ¯ is not considered so critical in the equation of dairy cattle. Na + , K + , CL
¯ are the main ions involved in sweat.
The effects of heat stress on dietary electrolyte balance may be summarised as:
1. Appetite is depressed, there is some indigestibility of feed and gut motility is slowed down;
2. Milk yield - at 35 ºC there is up to 33 % depression and at 40 ºC, as much as
50% ;
3. Loss in milk quality - fat and protein content declines ;
4. Loss in body weight;
5. Incidence of milk fever increases;
6. Metritis is more widespread ;
7. Uterine prolapse is more common;
8. Mammary gland infections increase;
9. Uterine infections increase;
10. Udder oedema is more severe;
11. Laminitis is more frequent;
12. Keto-acidosis is a recurring problem;
13. Fertility is lowered - insemination success rate falls, embryo mortality increases;
14. Calves are often premature and small;
15. Growing animals have markedly reduced weight gains;
16. Drinking water intake increases;
17. Nutrient deficiencies occur in marginally adequate diets;
(RCI Heat stress in dairy cattle).

Water metabolism
The total body water is estimated to range between 75 and 81% of the body weight for lactating dairy cows. Temperature is among the most important environmental factors controlling water intake in lactating dairy cows. Heat stress simultaneously influences both energy and water metabolism ( Silanikove, 1992 ). Under thermal stress cows tend to have increased water content in the rumen as a result of an accelerated water turnover rate. Water loss from an animal is a continuous process; taking place all the time and increasing during the heat stress because of additional evaporative water loss. Water intake of a dairy cow under heat stress increases significantly.
Steps to reduce heat stress
There are two main management practices that have been proposed to ameliorate the effects of heat stress: physical protection and nutritional dietary manipulation.
Physical protection
Natural shade
Trees are an excellent natural source of shade on the pasture. Trees are not effective blockers of solar radiation but the evaporation of moisture from the leaf surface cools the surrounding air. Solar radiation is a major factor in heat stress.
Blocking its effects through the use of properly constructed shade structures alone increases milk production remarkably. Two options are available: permanent shade structures and portable shade structures (Shearer et al., 2005). Major design parameters for permanent shade structures (orientation, floor space, height, ventilation, roof construction, feeding and water facilities, waste management system) depend on climate conditions. In hot and humid climates the alignment of the long-axis in an east-west direction achieves the maximum amount of shade and is the preferred orientation for tied animals, whereas north-south orientation is better where cows are free to move. Space requirements are essentially doubled in hot climate. Natural air movement under the permanent shade structure is affected by its height and width, the slope of the roof, the size of the ridge opening etc. Painting metal roofs white and adding insulation directly beneath the roof will reflect and insulate solar radiation and reduce thermal radiation on cows. Portable shades offer some advantages in their ability to be moved to a new area in different pastures.
Portable shade cloth, as well as light roofing material, may be used on the temporary shades
Cooling by reducing ambient air temperature
Air temperature of micro-environment can be lowered by air conditioning or refrigeration but the expense of such types of air cooling make these impractical.

The evaporative cooling pad (corrugated cardboard or similar material) and a fan system that uses the energy of air to evaporate water is a more economically feasible method to cool the micro-environment. Fine mist injection apparatus – recent design of micro-environmental evaporative cooling systems. This apparatus injects water under high pressure into a stream of air blown downward from above.
Coolers are positioned in the roof of the shade structures or cowsheds and air is pulled through the cooler at very high rates. This system is effective in arid climates.
High pressure foggers disperse very fine droplets of water which quickly evaporate, cooling the surrounding air and raising the relative humidity. The typical design incorporates a ring of fogger nozzles attached to the exhaust side of the fan. As fog droplets are emitted they are immediately dispersed into the fan's air stream where they soon evaporate. Animals are cooled as the cooled air is blown over their body and as they inspire the cooled air.
Misters. A mist droplet is larger than a fog droplet but cools air by the same principle.
These systems do not work well in windy conditions or in combination with fans in humid environments, where mist droplets are too large to fully evaporate before setting to the ground. The consequence is wet bedding and feed.
Enhancing the cow's natural mechanism of heat loss
Cooling in hot and humid climates emphasizes shade, wetting the skin, and moving air to enhance the cow's major mechanism for the dissipation of heat – evaporative cooling from the skin.
Sprinkler and fan cooling systems (Direct evaporative cooling)
Sprinkling uses large water droplet size to wet the hair coat to the skin. Cooling is accomplished as water evaporates from the hair and skin. Upper body sprinkling followed by forced-air ventilation reduces body temperature, increases feed intake and milk yield.
Sprayers in parlour exit lanes
Exit lane sprayers are designed to automatically spray water onto the cows as they pass through.
Nutritional dietary manipulation
Evaporative heat loss through sweating and panting is the primary mechanism for heat loss at high environmental temperatures. As a result of water loss from sweating at high temperatures thirst is increased and the huge waterflux resulting from increased water consumption also causes heavy loss of electrolytes (K + and
Na + ).

In high temperature there is panting respiration (an important reaction to cool the body by evaporative cooling). The rapid loss of C0
2
results in respiratory alkalosis.
Cows compensate by increasing urinary output of HC0
3
. Constant replacement of this ion is critical to the management of blood chemistry. Heat stress increases dietary requirements for the key electrolytes, Na+, K+ and HC03 .
Management of the dietary electrolyte balance is based on adding essential body salts and electrolytes to the drinking water and feed. It stabilises the dietary electrolyte balance, promotes homeostasis, assists the osmoregulation of body fluids, stimulates appetite, ensures normal skeletal development etc. (RCI Heat
Stress in Dairy Cattle).
Cold stress
European cattle tend to be tolerant to cold. It is the reason why the impact of cold stress on nutrient utilization and animal performance in cattle has received less research attention. Dairy cattle are housed in the cowsheds that minimize the impact of environmental temperature fluctuations on the animals. During the last decade uninsulated loose housing cowsheds for dairy cattle have become common also in northern countries. The temperature in the cowshed is only a few degrees higher than the temperature outside the cowshed. This trend in dairy cattle keeping increases the importance of cold stress investigations.
The effects of cold stress on metabolic and physiological adaptation
The next systemic reactions take place in animals suffering from cold stress:
1. Increased dry matter intake;
2. Increased rumination;
3. Increased gastrointestinal tract motility;
4. Increased rate of passage of feed and liquid in the rumen and digestive tract;
5. Increased basal metabolic rate and maintenance energy requirements;
6. Increased body oxygen consumption;
7. Increased cardiac output;
8. Increased adrenalin, cortisol and growth hormone levels;
9. Increased lipolysis, glyconeogenesis, glycogenolysis;
10. Increased hepatic glycose output;
11. Decreased rumen volume;
12. Decreased dry matter digestibility;
13. Decreased insulin response to a glucose infusion;
14. Decreased temperature of skin, ears, legs.
There are a number of factors that alter the effects of cold temperatures on animals: wind, hair depth, hair coat conditions etc. It is important to emphasize the value of a clean, dry hair coat and clean, dry environment with minimal wind for animals exposed to low temperatures. For the dairy cows cold should be considered as a local problem. Direct chilling of the udder depends as much on the thermal properties of the floor as on the temperature.

To avoid potential problems in cold weather:
1. Make sure the waterers or water tanks are not frozen.
2. Cold weather increases feed needs of cows. Hay provides more heat during digestion than concentrate feeds.
3. Do not close eave inlets. This will restrict the ventilation rate and create wet, damp conditions.
4. Prevent draught. Cows need dry, draught-free resting area.
5. Use ample amount of good, dry bedding.
6. Having dry teats when the cow leaves the parlour is important. One way to lessen the risk is to dip the teats, allow the dip of about 30 seconds and then blot dry using a paper towel.
(University of Minnesota Extension Service, 2004.)
Air quality
Atmospheric air contains 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and smaller amounts of other gases. Livestock in buildings changes air composition. Breathing uses oxygen and releases carbon dioxide. Odours are given off from respiration, animals' skin, urine and manure. Anaerobic decomposition of manure releases additional noxious gases. Without enough fresh air, toxic gases and dust in enclosed livestock buildings can harm animals and operators.
Main gases in livestock buildings that may affect animal health are ammonia, carbon dioxide, carbon monoxide, hydrogen sulphide and methane. Decomposing wastes give off odorous gases such as amines, amides, mercaptans, sulphides, and disulphides. In a properly designed and managed naturally ventilated building, noxious gases usually do not reach harmful concentrations. Low levels of these gases could be contributed to chronic diseases.
Ammonia (NH
3
) is released during anaerobic decomposition of urine. Anaerobic decomposition of nitrogen containing compounds in manure is also possible.
Ammonia levels tend to be high in buildings with litter, solid floors, or scrapers because manure spread over the floor area increases ammonia release.
Concentrations above 30 ppm may increase the incidence rate of respiratory diseases. The threshold limit for NH
3
is 20 ppm, in some countries 10 ppm. To reduce ammonia volatilisation in practice the following techniques, depending on building design are recommended:
1) sloping floor with scraper and urine gutter,
2) sloping floor with scraper under the slats,
3) flushing system above or under slats,
4) flushing system on solid floor,
5) mechanical lock on storage of manure,
6) reducing contact surface between manure and air,
7) use of extra straw in the building.

Carbon dioxide (CO
2
) is mainly from animal respiration and manure decomposition.
C0
2
concentration in well-ventilated rooms may be 2000 ppm (0.2%). Without ventilation in a closed building, the level can rise rapidly. Carbon dioxide triggers breathing, but at high concentrations contributes to oxygen deficiency. The threshold limit for CO
2
is 3000 ppm.
Hydrogen sulphide (H
2
S) is the most toxic gas from liquid manure storage.
Hydrogen sulphide is produced by anaerobic decomposition of organic wastes.
Concentrations are usually negligible in well-ventilated buildings except during agitation and pumping of liquid wastes. High ventilating rates can help reduce dangerous conditions during agitation and pumping of stored manure. At low concentration, hydrogen sulphide smells like rotten egg. H
2
S can rapidly destroy the sense of smell; lack of H
2
S odour is not an adequate warning. CIGR-report (1984) recommendations for threshold limit were 0.5 ppm.
Methane (CH
4
). Ruminant animals exhale a little methane, but most come from manure decomposition. Methane is lighter than air. It dissipates rapidly with some ventilation. Methane is not usually considered toxic. Accumulations in stagnant areas can be asphyxiating. Methane is explosive at concentrations of 5% –15% in the air.
Carbon monoxide (CO) can be produced from incomplete combustion of fuels inside buildings (for example, if a tractor is used for feeding and manure removing).
The gas is toxic for humans and animals. The threshold limit for CO is 10ppm.
(MWPS-33, 1989; CIGR No 94.1, 1994)
Air supply
There are two ventilation requirements:
1. The maximum requirement is the amount of air necessary to keep the relative humidity in the allowed level (80 –85%) in the humid season
(autumn).
2. The minimum requirement is the amount of air required to provide oxygen and to remove carbon dioxide, ammonia, dust and pathogens.
For the cowsheds the minimum ventilation rate is 1.4 m 3 /minute/animal, the maximum 10 times more (Dairy Housing, 1996). Minimal air volume per milking and dry cows is 18 m 3 , heifers 16 m 3 and calf (<12 weeks) 5 –8 m 3 (Hilliger, 1990).
Lighting
Light is necessary for the cattle to perform their normal behaviour, but light has also special physiological influence on the organism via the pineal, hypothalamus and pituitary glands. A cowshed is normally lit using a combination of natural light and artificial light. Natural light will enter the building through windows, wall openings, doors, roof lights etc. Artificial light is considered to provide a low level of background lighting (<20 lux) to allow animals to move confidently and to provide a higher intensity of light for animal inspection and movement of machinery (300 lux). Lighting

the rooms is particularly important in Northern countries. For example in Estonia the length of day in winter solstice is about six hours and the sun arises about 8˚ above the horizon.
Photoperiod may affect feed intake, milk production, growth rate and coat growth in cattle. A physiological response of cattle similar to a long day when a six hour day is supplemented with a burst of light for 15 to 60 minutes in the middle of the dark period. The light-dark cycle influences the diurnal rhythms. Extending day length diminishes aggression and locomotion in animal group.
The recommended light period extension for dairy cows is 16 hours, working light intensity 100 lux, orientation light 25 lux, night light 5 lux (Phillips, C., 2002; Danish
Standards DS=700). The optimum visual of cattle is at a light intensity 120 lux
(Dannanmann et al., 1985).
Milking
One source of potential injury to the dairy cow is the extreme distension of udder during the milk production process. The udder produces milk all the time. As pressure from produced milk increases, the rate of production slows down. High producing cows will stop the synthesis of milk after about 8 –10 hours. Regular milking is important to maintain high production.
In loose housing cowsheds the milking parlours are in use. In dairy husbandry two times milking a day is widespread. Milking three times a day at regular intervals will decrease udder distension and increase milk production from 6 to 20%. Milk fat percent will decrease slightly. However, in free-stall cowsheds this increases by 30 –
50% the time each cow has to stand in a collecting yard and shorten the time available for feeding and rest. The development of milking robots and spread in dairy husbandry permit to work out automated technologies and design special stations, which cows may visit freely without prolonged waiting to feed concentrates and be milked as necessary.
Reducing stress on cows in the milking parlour is very important. Milking should be organised so that the cows return to feed and water in the shortest time possible.

Dairy cattle welfare
Cow comfort can be regarded as the degree of stress or lack of it as related to the environment in which the animal is confined. The term may be applied to
1) climatic conditions,
2) physical discomfort,
3) social discomfort (absence of contacts, confrontation with other cows etc.),
4) changes in behaviour resulting from managemental practices or housing facilities.
Cow comfort affects animals’ health, milk production, eating habits, feed intake, fertility and longevity.
Signs of good welfare
There are no major welfare problems when the herd is characterised by
1) minimum mortality,
2) low morbidity,
3) little or no risk of injury,
4) good body condition (sustaining adequate production and reproduction),
5) the ability to perform species-specific activities (including social interactions, exploration, and play),
6) the absence of abnormal behaviour and physiological signs of stress, including suppression of immune responses (Anonymous, 2001).
Signs of welfare problems
Environmental conditions that significantly depart from an animal’s needs can be the source of welfare problems, the extent of which depends on their prevalence, duration and intensity and on the animal’s ability to adjust to them.
Signs of trouble
1. Injuries. Cows have abrasions or other injuries to hocks, knees, or stifles, or bumps over the top line or rib cage.
2. Reluctance. Cows do not like to use stalls or move slowly in and out of the milking parlour.
3. Hesitation. Cows stand uncertainly in a stall for several minutes before lying down, or lie for a long time before standing up.Poor positioning. Cows lie partially in the stall and partially in the alley, or choose to lie in the alley.
5. Inappropriate behaviour. Cows rise like horses, back into stalls, paw bedding out of stalls, or show abnormal behaviour at feed bunks or around water.
6. Trouble with feed or water. Cows lap at water or chew on water bowls, toss feed, or fling water when drinking.

7. Lack of oestrus. In barns with slippery floors or those with short tie chains and electric trainers, cows may protest silently by not showing signs of oestrus.
8. Physical ailments. Cows show problems such as sore feet, mastitis, and metabolic diseases (Anderson N. Candid Camera on Cow Comfort).
Cows in unsafe facilities exhibit fear - feelings of alarm or disquiet caused by the expectation of danger, pain, or disaster.
Signs of fear
1. Increased defecation and urination;
2. Standing with front feet in the stalls and rear feet in the alleys;
3. Increased standing and less lying;
4. Increased lying time and less frequent standing and re-positioning;
5. Refusal to use stalls and lying in alleys or partially in stalls;
6. The hesitation waltz - apprehensive behaviour before lying in stalls;
7. Unusual actions when rising or trying to rest in stalls;
8. Lapping at water;
9. Reaching over walls to drink rather than stand in passageways where waterers are located;
10. Unusual and unexpected approaches to eating or drinking;
11. Unusual walking actions;
12. Reluctance to cross gutters or enter some areas of the barn;
(Anderson N. The ancient cow contract – ergonomics, health and welfare issues in dairy cattle housing. http://www.nmconline.org/articles/ergo.pdf
)
An attempt has made to put some of the most important performance criteria for the assessment of the impact of housing and management on dairy cattle welfare (table
4) in certain order (Anonymous..., 2001).
Table 4. Performance criteria for welfare
Rank Performance criteria Reasons
1.
2.
Lameness
Mastitis
Pain, reduced feed intake and production; may be chronic
May give pain and reduced production; may be chronic; relatively high
3.
4.
Behavioural restrictions (sexual, social, resting, getting up, and lying down, body care)
Other health problems
(metabolic disorders, fertility, incidence
May cause frustration; permanent; all animals
May be severe; may be chronic; usually incidental, more prevalent in highlongevity) yielding cows a Explanation of the ranking of the performance criterion in terms of intensity, duration, and incidence separated by semicolons. The term chronic indicates conditions that might last several weeks or more.

The assessment of welfare
Welfare analysis is multidimensional including different parameters and many welfare assessment indicators.
1) Production characteristics (performance, yield).
2) Physiological indicators.
3) Ethological criteria.
4) Pathological indicators (morbidity and mortality disease, lesions to the coat.
Most of these indicators require expensive and varied investigations. To make an assessment tool practical, it is necessary to reduce the number of indicators to be used. Robust protocols are needed for assessing the welfare of animals. Such assessments must be simple but comprehensive. They should consider both the provision of resources, management and stockmanship that contribute to good husbandry and the elements that contribute to the desired outcome — good animal welfare. The first essential stage in this process is to explore and program in detail the procedures necessary to establish the welfare state of animals. This requires the following:
1) Identification of practical, robust methods for assessing the important elements for the husbandry and welfare of animals.
2) Testing the efficacy of these practical measures against established, more searching indices of animal welfare established under experimental conditions.
3) Development of protocols for the assessment of husbandry and welfare
(Webster, 2003).
Cattle welfare can be assessed in a scientific way using different parameters and a combination of methods. It is possible to divide parameters characterising animal welfare into two groups:
1) environmental parameters(features of the environment and management),
2) animal based parameters (animals’ reactions to environment: behaviour, health, physiology).
Examples of the environmental parameters: length of stalls, space allowance, quality and amount of bedding, access to pasture, etc. Environmental parameters are relatively easy and quick to record and serve a good basis for problem solving. The
Animal Needs Index (ANI) (Bartussek,2000) lays the main emphasis on environmental parameters. The ANI considers five aspects of the animal’s environment:
1) the possibility of mobility,
2) social contact,
3) condition of flooring for lying, standing and walking,
4) climatisation (including ventilation, light and noise),
5) the intensity or quality of human care.

Within each field, several species-specific criteria are graded by points. The overall sum of the points gives the ANI-value. Poor conditions within one area can be compensated for by a better situation within another field.
Examples of animal based parameters: level of stress hormones, abnormal behaviour, symptoms of disease, etc. Recording of animal based parameters demands considerable resources, results may be difficult to interpret . A nimal based parameters can be used in the e.g. on-farm assessment of dairy cows welfare
(Capdeville and Veissier, 2001). Assessment is based on the following parameters:
1) health (diseases, infertility, number of stillborn calves, and culling),
2) injuries,
3) behaviour (various aspects of movement),
4) position in cubicle,
5) social conflicts between animals,
6) relationship between the farmer and animals,
7) environment (the existence of frightening events and the possibility of cows having contacts between themselves.
The assessment is presented in terms of five freedoms. For example, welfare may be interpreted as satisfactory with respect to expression of normal behaviour and insufficient with respect to level of injuries. The methods for the assessment of farm animal welfare are presented in table 5.
Table 5. The methods for farm animal welfare assessment ( Johnsen et al, 2001)
Animal based parameters
Environmental parameters
TGI 35L Ethical accounting
Animal Needs
Index (ANI)
The impact of housing systems on welfare in dairy cattle
On-farm assessment of dairy cows’ welfare
TGI 200 Decision Support System
The Bristol Welfare Assurance Programme (BWAP) aims to incorporate existing animal based welfare assessment techniques into conventional and organic farming certification systems http://www.vetschool.bris.ac.uk/animalwelfare/ ).
Delphi technique was used to gather the opinions of animal welfare experts on the most appropriate measures for welfare assessment of farm animals (Whay et al.,
2003). The respondents suggested measures based upon observations of health status, behaviour, and examination of records. These measures reflect the animal`s welfare state - in other words, how the animal is coping within the environment and husbandry system in which it lives. The measures for cattle were categorised into 22 aspects with the highest ranking of importance being given to the observation of lameness.

The selection of parameters for cattle from welfare research, from assessment protocols and from the literature established three groups of parameters (Winckler et al., 2003):
1) Parameters which can readily be included, such as lameness, injuries, body condition score, cleanliness, getting up/lying down behaviour, agonistic social behaviour, oral abnormal behaviours, human behaviour toward the animals and measures of the animal – human relationship;
2) Parameters, which require more information on reliability, such as indicators of good welfare and housing factors;
3) Parameters that are regarded as important but so far lack reliability in most countries, such as the incidence of clinical diseases and mortality.
So far, no scientifically based welfare assessment tool has found widespread acceptance.There is a growing agreement that welfare should be recorded at animal level, using direct measures. Housing conditions and production results are only indirect measures. Instead, physiology, behaviour and disease occurrence are key elements of welfare assessment. (Keeling, 2001; Hultgren, 2003).
Dairy Farm Risk Analysis
Incidence of diseases among the farm animals is often caused by mistakes made by man or deficiency of knowledge. In modern animal husbandry most frequent diseases are related with keeping conditions (keeping technology, microclimate, organisation of labour) (Ekesbo, 1988). It means that the vulnerability of animals depends on keeping conditions.
Herd health is important both for the financial loss resulting from deaths, culling, lower milk productivity, from the cost of treatment, and the suffering it may cause to the animal. For example, in the Netherlands the economic losses caused by diseases of dairy cows are 182-227 EUR per cow (Dijkihuizen et al., 1997). The expenses caused by most prevalent diseases of the herds for 100 cows (mastitis, metritis, ovulatory dysfunction, retained placenta, dystocia etc.) fall between 1200 –
13600 £ (average 6300 £) per year in the UK (Kossaibati et al, 1998). For this reason different herd health monitoring programs have been created and put into practice (Diesch, 1988; Ekesbo et al., 1994; Saloniemi, 1991; Sviland and Vaage,
2002).
Key elements in such a programme include:
1) a strengths –weaknesses assessment and priority settings at the start,
2) clinical animal inspection,
3) farm inspection,
4) data monitoring,
5) herd problem analysis,
6) the interpretation of collected information including putative risk factors for disease occurrence,
7) the development and application of preventive procedures and the critical monitoring of their implementation (Noordhuizen and Collins, 2002).

Monitoring means making routine observations on health, productivity and environmental factors and recording and transmitting these observations (Thrusfield,
2001).
Health monitoring makes it possible to determine the risk factors (Frei et al.,
1997). Risk factor is a factor which characterizes an animal or environment and which existence increases the probability of appearance of diseases in the herd
(Waldner, 2001). Risk factors are usually divided into two groups:
1) risk factors of a herd (external or environmental risk factor). These factors such as physical, chemical and biological impacts, keeping technology, organisation of work, dealing with animals etc. originate from environment and influence all animals in the herd (Ekesbo et al., 1994).
2) risk factors of a single animal (individual or internal risk factors) like age, breed, reproduction cycle, productivity, genetic predisposition etc. (Ekesbo and
Oltenacu, 1994).
To evaluate the effect of these risk factors different descriptive and theoretical methods of epidemiology are used. Usually the next parameters are used for the characterization of health state and risk factors in the herd: disease prevalence rate, disease incidence, incidence rate, cumulative incidence rate, confounding factor, relative risk, adjusted relative risk (Noordhuizen et al., 2001; Thrusfield, 2001).
Quite often in the case of disease the next causal chain exists: environmental factor

change of behaviour
 disease A
 disease B (Ekesbo, 1991; Hartung,
1994). For the prevention of multifactorial diseases is very important to ascertain the existence of causal chain and to determine their hierarchy of harmfulness of each risk factor in the process of disease. It helps to work out an effective program for the prevention of diseases in concrete herds and to organise effective prophylaxis
(Osteras and Leslie, 1997, Gröhn and Rajala-Schultz,2000).
For example multifactorial are also the most prominent group of diseases of dairy cows – udder diseases. Among them the most frequently is diagnosed mastitis, which causes the greatest economical losses for farmers in dairy cattle farming. By
Saloniemi et al. (1986) more than 40% of mastitis cases in high producing herds are induced by environmental risk factors. The more important environmental risk factors of mastitis are microclimate, type of cowshed, constructions, stalls, mangers, type and amount of bedding, manure removal, milking (aggregates, technique, hygiene), nutrition, working personnel, size of herd, keeping technology (Ekesbo, 1966;
Saloniemi, 1980; Oltenacu et al., 1990; Faye et al., 1997; Østerås and Leslie, 1997;
Valde et al., 1997; Whitakier et al., 2000; Sviland and Waage, 2002; Hultgren, 2002).
An attempt has made to arrange the housing systems for cattle according the level of welfare of animals (table 6).

Table 6. Typical housing systems for cattle ranked from low to potentially high welfare
Rank Housing system
Brief description a Performance criteria b
1 Tie stall Cows are tethered, gutter or partly metal grid (hind legs), cow trainers,
Behavioral restrictions
(e. g., movements, milking and feeding (of roughage and concentrate) at the stall, grazing during the summer social contact), lameness, mastitis
2 Cubicle house c
Group housing, more or less stable groups, concrete solid or slatted floor, milking parlour, roughage at feeding gate, concentrate mixed with roughage or fed in individual feeder, grazing during summer
Group housing, more or less stable
Lameness, behavioural floor mastitis, restrictions due to slipperiness of the
3 Deep litter groups, straw- bedded lying area, milking parlour, roughage at feeding gate, concentrate mixed with roughage or fed in individual feeder, grazing during summer
Mastitis (hygiene) a The main design criteria that account for the ranking of the housing system are underlined.
b Lists the main animal-based welfare indicators c Indicates the most common system at present (Anonymous , 2001).
It is difficult to be categorical about differences between housing systems in the level of cow comfort, since the level of welfare within each system can vary greatly depending on the details of the system (Rushen and Passillé, 1999).
Raw milk quality requirements
Milk and milk products have been produced for thousands of years. Cow milk comprises 90.8% of world milk production.
The quality of raw milk is determined by many aspects of composition and hygiene.
The main criteria of raw milk of high hygienic value are the low number of saprophytic micro-organisms, absence or very low number of pathogenic microorganisms, avoidance of residues and contaminants (Heeschen, 1996). For the member states of the EU, the legal situation concerning raw milk is given in the
Regulation (EC) No 853/2004 of the European Parliament and of the Council of 29
April 2004 – hereafter Hygiene Rules for Food (Table 7). In accordance with the
Hygiene Rules for Food, each member state lays down national requirements for the milk collected from production holdings.

Table 7. Regulation (EC) No 853/2004 Hygiene Rules for Food
Section IX, Chapter I. Raw milk −primary production
I. Health requirements for raw milk production (Animal health requirement for raw milk)
II. Hygiene on milk production holdings
A. Requirements for premises and equipment
B. Hygiene during milking, collection and transport
C. Staff hygiene
III. Criteria for raw milk
1. Following the criteria for raw milk supply pending the establishment of standards in the context of more specific legislation on the quality of milk and dairy products.
2. A representative number of samples of raw milk collected from milk production holdings taken by random sampling must be checked for compliance with point 3 and 4.
3. 3. Food business operators must initiate procedures to ensure that the raw co cows’ milk meets the following criteria:
Plate count 30 ºC (per ml) ≤ 100000*
Somatic Cell Count (per ml) ≤ 400000**
4. 4. Without prejudice to Directive 96/23/EC, food business operators must initiate procedures to ensure that raw milk is not placed on the market if either: a) a) it contains antibiotic residues in a quantity, that, in respect of any on one of the substances referred to A exes I and III to regulation (EE C)
No2377/9, exceeds the levels authorised under that Regulation; a) b) b) the combined total residues of antibiotic substances exceed any
maximum permitted value.
5. When raw milk fails to comply with point 3 or 4, the food business operator must inform the competent authority and take measures to correct the situation.
* Rolling geometric average over a two-month period, with at least two samples per month
** Rolling geometric average over a three-month period, within at least one sample per month, unless the competent authority specifies another methodology to take account of seasonal variations in production levels.
Milk quality parameters.
Standard plate count (SPC)
Standard plate count in raw milk is the most frequently used hygienic criteria of milk quality and production hygiene. Bacterial contamination can generally occur from three main sources: from the udder tissue, from the udder skin and from the surface of milk-handling and storage equipment. (McKinnon et al ., 1990).
Somatic cell count
Somatic cell count in raw milk indicates udder health as infection of udder is always accompanied with the rapid increase of somatic cell count. Mastitis is one of the most widespread, complicated and costly dairy cow diseases. Economic loss resulted from mastitis primarily affects the milk producer, but the decrease of milk

quality, especially changes in milk composition, result in economic losses in dairy industry as well.
Milk freezing point
Dairy industry uses freezing point, one of the most stable physical properties of milk, mainly to detect and prevent adulteration of raw milk. Extraneous water in milk leads to economic loss, decrease of the quality of milk products and a risk on consumers’ safety.
Content of colostrum residues
The standards for collected milk in most countries prescribe that milk may not contain colostrum residues. Due to high content of immunoglobulins, the residues of colostrum in raw milk result in many problems for dairy industries, such as a decrease in the output of milk products (cheese, curd), flavour faults, increase of the thermostability of milk, scorch on the surface of plate-heat exchanger etc. (Milk
Quality Improvement Ltd., 1991).
Milk safety for the consumer
Chemical and microbiological contamination of milk is a potential reason for foodborne disease outbreaks. Motarjemi and Käferstein (1999) have pointed out the areas, the changes of which are mostly connected to food-borne disease outbreaks.
1. Food provision system. Mass production and distribution brings about the possibility of extensive disease outbreaks. In the conditions of intensive agricultural production and animal farming, the possibility of contamination of raw material with the residues of pesticides and veterinary drugs is higher. As a result of urbanisation, food chains are becoming longer and this in turn affects contamination possibilities. Regarding demographic situation, the increasing percentage of elderly people and of those belonging to risk groups
(immunocompromised) in the population of developed countries, affects the frequency of incidence rate.
2. Social situation, habits and lifestyle. People travel more frequently, consume food outside home, consume semi-manufactured products and prepared food.
Many food-borne disease outbreaks are resulted from mistakes made in food production, preparation or from inadequate fulfilling of individual hygiene requirements by food handlers. Increasing consumption of prepared foods and the increased number of food service establishments have made the role of food handlers’ knowledge about hygiene and the practice of good hygiene habits very important.
3. Healthcare system and infrastructure. The number of food-processing plants increase more rapidly than state resources for carrying out inspection and control.

4. Environmental conditions. Contamination of environment and the change of climate bring about new hazards.
European Commission has created Rapid Alert System for Food and Feed (RASFF) in order to defend the consumer against food- and feed-borne hazards. European
Commission ( http://europa.eu.int/comm/food/index_en.htm
), European Food Safety
Authority ( http://europa.eu.int/comm/food/efsa_en.htm
) and the member states belong to the system.
Microbiological hazards associated with milk and milk products
Milk and milk products are a nutrient medium where microorganisms have all conditions necessary for life. Milk of healthy cow, milked in hygienic conditions, contains comparatively few microorganisms but in the stages of handling milk contaminates due to human activity The most wide-spread microorganisms which are considered to cause milk-borne diseases, are Staphylococcus aureus,
Salmonella typhii/typhimurium, Escherichia coli, Yersinia enterocolitica,
Campylobacter jejuni, Clostridia spp. Bacillus cereus, Listeria monocytogenes
(Robinson, 1990). Non-spore forming pathogens in milk are destroyed by pasteurization. Commonly milk products are cooled in order to avoid spoilage but many milk products preserve due to factors hindering development of microorganisms (decreasing water content, addition of salts, pH).
De Buyser et al. (2001) analysed the percentage of disease outbreaks implicating milk and milk products among incidences with known food vehicle in France and other countries since 1980s. Attention was paid to Salmonella spp., Staphylococcus aureus, Listeria monocytogenes and pathogenic Escherichia coli . Annual statistics of food-borne incidences for seven countries revealed that milk and milk products were associated with 1 to 5% of bacterial outbreaks.
Chemical hazards in milk and milk products
The main chemical hazards in milk and milk products are compounds, which have got into milk from agricultural production, environment, animal treatment, cleaning of equipment and utensils, and disinfection. These compounds get into milk in different direct or indirect ways. Frequently it is difficult to avoid the contamination of milk with them (Fischer et al., 2003). Major contaminants:
1) pesticides,
2) veterinary remedies,
3) hormones,
4) cleaning and disinfecting agents,
5) dioxins,
6) polychloride biphenyls (PCBs),
7) heavy metals,
8) mycotoxins.

Milk allergy
People may be hypersensitive to milk proteins.
Lactose intolerance
Lactose intolerance is the deficiency of lactose degrading enzyme lactase, which is found in the mucous membrane of the small intestine of humans. Hypolactasia may be primary, recessively hereditary (23 to 24% of adult Estonians), or secondary, the result of small intestine diseases. In the case of hypolactasia, the consumption of milk results in digestive disorders.
There are several possibilities to produce safe milk products, avoid contamination and reduce economic losses and expenses. They are:
1. Improvement of food hygiene and milk quality at farm level by guaranteeing good 0conditions for animal welfare.
2. Training of food handlers involved in milk production, primary handling, collecting and processing.
3. Application of effective technological measures. The use of pasteurization, sterilization or acidification in technological processes prolongs the product shelf life and decreases or eliminates pathogens in milk and milk products.
4. Legislation. Legislation has a significant effect on food industry making it to pay great attention to food safety and fulfil its requirements and directives.
5. Application of measures ensuring food safety and quality (Good
Manufacturing Practice, HACCP) (Noordhuizen and Metz, 2005).
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