WATER
Water, is the most critical nutrient that we consciously
supply to birds, yet in most instances, it is taken completely for
granted and often receives attention only when mechanical
problems occur. Water is by far the largest single constituent of
the body, and represents about 70% of total body weight. Of this
body water, about 70% is inside the cells of the body and 30% is
in the fluid surrounding the cells and in the blood. The water
content of the body is associated with muscle and other proteins.
This means that as a bird ages, and its body fat content
increases, then its body water content expressed as a percent of
body weight will decrease. The bird obtains its water by
drinking, from the feed and by catabolism of body tissues which
is a normal part of growth and development.
a. Water intake
Water intake of a bird increases with age, although it
decreases per unit of body weight. Drinking behaviour is closely
associated with feed intake, and so most factors affecting feed
intake will indirectly influence water intake. At moderate
temperatures, birds will consume almost twice as much water by
weight as they eat as feed. Any nutrients that increase mineral
excretion by the kidney will influence water intake. For
example, salt, or an ingredient high in sodium, will increase
water intake.
Similarly, feeding an ingredient high in potassium such as
molasses or soybean meal, or calcium/phosphorus sources
contaminated with magnesium, will result in increased water
intake. Such increases in water intake are of no major concern to
the bird itself, but obviously result in increased water excretion
and so wetter manure. Table 2.29 indicates average water
consumption of various poultry species maintained at 20 or
32ºC. These figures indicate approximate water usage values
and will vary with the stage of production, health and feed
composition. As a generalization, for any bird up to 8 weeks of
age, an approximation of water needs can be calculated by
multiplying age in days x 6 (e.g.42 d = 252 ml/d).
In calculating the water needs of egg producing stock, it
should be realized that water intake is not constant throughout
the day, rather it varies depending upon the stage of egg
formation (Fig 2.2). These data clearly show a peak in water
consumption immediately following egg laying, and again, at
the time just prior to the end of a normal light cycle. This means
that water needs must be accommodated during these peak times
(around 10 – 11 a.m. and 6 – 8 p.m.) within a 6 a.m. – 8 p.m.
light cycle, because most birds will be in the same stage of egg
formation as directed by the light program.
Fig. 2.2 Water consumption of laying hens in relation to time of
viposition. (from Mongin and Sauveur, 1974)
Table 2.29 Daily ad-lib water consumption of poultry (liters per
1,000 birds)
20ºC
Leghorn pullet
Laying hen
4 wk
50
75
12 wk
115
180
18 wk
140
200
50% prod.
150
250
90% prod.
180
300
120
200
4 wk
75
120
12 wk
140
220
18 wk
180
300
50% prod
180
300
80% prod
210
360
Non-laying hen
Broiler breeder pullet
Broiler breeder hen
32ºC
Broiler chicken
1 wk
24
40
3 wk
100
190
6 wk
240
500
9 wk
300
600
1 wk
24
50
4 wk
110
200
12 wk
320
600
18 wk
450
850
Turkey breeder hen
500
900
Turkey breeder tom
500
1100
1 wk
28
50
4 wk
120
230
8 wk
300
600
240
500
1 wk
28
50
4 wk
250
450
12 wk
350
600
350
600
Turkey
Duck
Duck breeder
Goose
Goose breeder
These figures indicate approximate water usage values and will vary with the stage of
production, health and feed consumption.
The contribution of feed is not usually considered in
calculating water balance, yet most feeds will contain around
10% of free water. Other bound water may become available
during digestion and metabolism, such that 7 – 8% of total
requirements can originate from the feed.
Water is created in the body as a by-product of general
metabolism. If fats are broken down, then about 1.2 g of water
are produced from each gram of fat. Likewise protein and
carbohydrate will yield about 0.6 and 0.5 g per gram
respectively. Total metabolic water can be more easily estimated
from the bird’s energy intake because on average 0.14 g of
water is produced for each kcal of energy metabolized. This
means that for a laying hen, consuming 280 kcal ME/day, about
39 g of metabolic water will be produced. Feed and metabolic
water together therefore account for about 20% of total water
needs, and so are very important in the calculation of water
balance.
b. Water output
The quantities of water excreted in the feces and urine are
dependent on water intake. Broiler chickens produce excreta
containing about 60 – 70% moisture, while that produced by the
laying hen contains about 80% moisture. For the laying hen at
least, the quantity of water excreted in the feces is about four
times that excreted as urine. Undoubtedly, this loss is subject to
considerable variation with the amount and nature of undigested
feed.
Evaporation is one of four physical routes by which poultry
can control their body temperature. Due to its molecular
structure and bonding, water has an unusually high latent heat of
vaporization. Some 0.5 kcals of heat are required to vaporize
one gram of water. Evaporative heat loss takes place mainly
through the respiratory tract. The fowl has no sweat glands,
consequently evaporation via the skin is minimal. Evaporation
overwhelmingly occurs via the moist surface layer of the
respiratory tract to the inspired air which is ‘saturated’ with
water vapor at body temperature. Evaporation rate is therefore
proportional to respiratory rate. Heat loss through evaporation
represents only about 12% of total heat loss in the broiler
chicken housed at 10ºC, but this increases dramatically through
26 – 35ºC where it may contribute as much as 50% of total heat
loss from the body. At high temperatures, evaporative water loss
will approximate water intake and so this obviously imposes
major demands on the ventilation systems.
c. Water balance and dehydration
Under normal physiological conditions for adult birds,
water intake and output are controlled to maintain a constant
level of water in the body. A positive water balance is found in
the growing bird to accommodate growth. With drinking water
being supplied ad libitum under most commercial conditions,
dehydration due to lack of drinking water should not occur. The
adverse effects of short term reduced water intake are often a
result of a concomitant reduction in feed intake.
The turkey poult is most susceptible to dehydration
resulting from drinking water deprivation, and mortality occurs
when drinking water is re-introduced to the poults. Poults 11
days of age, subjected to a 48-hour period of water deprivation,
showed 83% mortality following reintroduction of ad libitum
cold water, and in most cases death occurred within 30 minutes.
Poults 18 days of age showed less mortality which was
somewhat delayed (2 –34 hours) while older turkeys subjected
to the same conditions showed no mortality. The exact reason
for this mortality is not fully understood. Poults deprived of
water show reduced body temperature, and when water is
introduced, body temperature continues to decrease for 30
minutes or so. Poults often drink large amounts of water
following dehydration, and it has been suggested that the
problem relates to simple water intoxication and associated
dilution of electrolytes in the body. If young poults are
dehydrated for whatever reason, then administration of
electrolytes in the water may be beneficial. This problem does
not seem to occur with chickens.
d. Drinking water temperature
Water offered to birds is usually at ambient temperature.
This means that for laying birds housed under controlled
environmental conditions, the temperature of drinking water is
held fairly constant, while for broiler chickens, water
temperature decreases with age corresponding to a reduction in
brooding temperature. It is only for the first few days of a
chick’s life that drinking water temperature is specified, where
traditional management recommendations suggest the use of
‘warm’ water. However, there is little documented evidence
supporting this recommendation. Birds drink more water at
higher environmental temperatures, yet the cooling of water
may result in even higher intakes. Table 2.30 outlines the results
of a small scale study conducted with layers housed at 33ºC.
Table 2.30 Layer performance at 33ºC with hot vs cold drinking water
Water temperature
33ºC
2ºC
Feed/bird/day (g)
63.8
75.8
Egg production(%)
81.0
93.0
Egg weight (g)
49.0
48.5
When birds received cool water for a 4-week period, they
were able to maintain peak egg production, possibly due to
higher feed intake. Under commercial conditions, with long runs
of water pipe, it is obviously very difficult to duplicate these
conditions. However, it does show the importance of trying to
keep the water as cool as possible, and in this regard, the usual
practice of placing water tanks on high towers in direct sunlight
should be seriously questioned.
e. Water restriction
Most birds should have continuous access to water. Some
breeders recommend water restriction of laying hens as a means
of preventing wet manure, especially in hot climates, although
serious consideration should be given to other preventative
measures prior to this last resort. Production may drop as much
as 30% when hens are deprived of water for 24 hours, and it
may take as long as 25 to 30 days before production returns to
normal. Similar results have been reported for broilers where
decreases in water supply have resulted in marked depressions
in weight gain. Table 2.31 shows the results of a controlled test
where water restriction was imposed on broilers. There was a
marked drop in feed intake with the greatest reduction occurring
with the first 10% reduction in water intake, causing a 10%
decline in feed intake.
Table 2.31 Effect of water restriction on relative weekly feed
consumption of broilers
Age (weeks)
Degree of water restriction (%)
0
10
20
30
40
50
2
100
84
84
75
84
71
4
100
99
102
90
85
80
6
100
88
81
78
73
71
8
100
86
83
79
74
67
Total
100
90
87
81
71
73
* All birds receive water ad libitum for first week (Data from Kellerup et al. 1971)
The effect of an accidental 48-hour cut in water supply to
layers is shown in Fig. 2.3. Production dropped off very quickly
to virtually 0%, although interestingly a few birds maintained
normal production. Most birds that resumed production within
28 d achieved normal output for their age, and there was an
indication of improved shell quality.
For certain classes of stock, intentional water restriction is
used as a management tool. To date, this is most common with
broiler breeders fed on a skip-a-day program. Water restriction
may occur on both feed-days and off-feed days. Restriction on
off-feed days is done because it is assumed that birds will overconsume water on these days due to hunger or boredom.
However, it seems as though breeders do not drink that much
water on an off-feed day (Table 2.32).
Table 2.32 Water intake of 13 week-old broiler breeders
(ml/bird/day)
Water restricted
each
only on
Ad-lib
day
feed days
water
Feeding day
175
182
270
Non-feed day
108
109
36
Average
141
145
153
All birds drank the same average amount of water over a 2
day feeding schedule regardless of water treatment. When birds
are given free-choice water, they obviously over-consume on a
feed-day, but drink little on an off-feed day. These data suggest
the need for water restriction of skip-a-day fed birds, although
special attention on feed-days rather than off-feed days will be
most advantageous in preventing wet litter.
Fig. 2.3 Effect of a 48-hour period of water deprivation on
egg numbers.
f. Water quality
Water quality should be monitored with assays conducted at
least each 6 months. Chemical contaminants are the most
serious problem affecting water quality. However, poultry
usually adjust to high levels of certain minerals after a period of
time, and so only in a relatively small number of cases does the
mineral content of water significantly affect the performance of
a flock. There are certain areas where water salinity is high
enough to adversely affect flock performance. In such cases, it
may be necessary to remove some of the supplemental salt from
the diet. However, this should be done only after careful
consideration to ensure that there will be a sufficient salt intake
because performance can be severely reduced if salt intake is too
low.
Any bacterial contamination of water is an indication that
surface water is entering the water supply and steps should be
taken to correct the situation. Alternatively, the water may be
chlorinated to eliminate contamination. Another problem that
can exist with water is a build-up of nitrates or nitrites. Such
contamination is usually an indication of run-off from animal
wastes or fertilizers leaching into the water system. Although
the standard for human water supply is 10 to 20 ppm of nitrate
nitrogen, higher levels can usually be tolerated by animals.
Levels beyond 50 ppm need to be present before water is
suspected as a factor in the poor performance of poultry. As
nitrites are 10 times more toxic than nitrates, and because
bacteria in the intestinal tract and in the water supply can
convert nitrates to nitrites, levels of these two contaminants in
the water supply must be kept to a minimum. Superchlorination
of the water will quickly oxidize nitrites to nitrates thereby
reducing their toxicity. Before initiating a superchlorination
program, check with a local pathologist to ensure a proper level
of chlorination in order not to interfere with the performance or
efficiency of vaccines or other drugs.
Table 2.33 Concentration of water minerals above which
problems may occur with poultry (ppm)
Total soluble salts (hardness)
1500
Chloride
500
Sulphate
1000
Iron
50
Magnesium
200
Potassium
500
Sodium
500
Nitrate
50
Arsenic
0.01
6.0 – 8.5
pH
Table 2.33 outlines standards for drinking water in terms of
mineral levels. Toxicity and loss of performance will vary
dependent upon bird age and class of stock, but in general these
values can be used as guidelines to indicate the possibility of
toxicity with birds consuming such water over prolonged
periods.
In the last few years, there has been an interest in the
treatment of water for poultry. In large part, this is carried out in
an attempt to prevent problems of mineral deposits occurring in
pipelines, boilers and automatic waterers, rather than preventing
toxicity
problems
per
se.
Such
treatments
involves
orthophosphates, which sequester calcium and magnesium,
thereby preventing precipitation in the water supply. In most
situations, these systems will not unduly alter the water
composition in terms of the bird’s nutritional requirements. As a
last resort, some producers use water softeners, and in these
situations, there is some cause for concern, regarding the bird’s
health. These softeners contain an active column of resin, that
has the ability to exchange one ion (mineral) for another. Over
time, the resin column becomes saturated with the absorbed
minerals (usually calcium and magnesium salts) that are
extracted from the water, and so it must be flushed and
recharged with the donor mineral. In most softeners, this
recharging process involves sodium from NaCl. This means that
sodium is replacing other minerals in the water, because sodium
salts readily dissolve, and will not leave mineral scale in the
equipment. The amount of sodium that is pumped into the water
supply is therefore in direct proportion to the hard minerals
extracted from the water. In areas of very hard water, one can
expect higher levels of sodium in water reaching the birds, and
vice-versa in areas of lower water hardness. Problems in water
sodium will likely occur if softener salt use exceeds 40
kg/40,000 litres of water.
g. General management considerations with water
Where continuous flow water troughs are used for caged birds,
one must be sure that birds at the end of the trough obtain
sufficient water. A rise in house temperature will result in
increased water consumption, and unless the water supply can
be adjusted accordingly, shortages of water may result for the
birds at the far end of the line. It has also been demonstrated that
poorly beak-trimmed birds may not be able to drink sufficient
water to sustain maximum production. When the lower beak of
the bird is too long, up to 20% loss in egg production can occur,
compared with properly beak-trimmed birds. When disease or
stress occur, a decrease in water consumption is usually noted a
day or two before a decrease in feed consumption. For this
reason, managers should consider installing water meters on all
water lines to each pen or cage row and have the attendant keep
a daily record of water consumption. Such records can give
early warning of potential problems with the flock.