Impact of Nutrition on the Health and
Fertility of Dairy Cows
Martin J Green
BVSc DCHP MRCVS
RCVS Specialist Cattle Health and Production
Orchard Veterinary Group, Glastonbury / University of Warwick
This paper discusses general issues surrounding nutrition and dairy cow health, and
outlines important nutritional influences on health and fertility.
Introduction
Food sustains life and the adage ‘we are what we eat’ is certainly true to some extent.
Indeed it becomes increasingly apparent from nutritional research that the
composition of our diet probably influences the quality and quantity of the lives we
lead.
All body systems are driven by biochemical processes and many of these require a
balance of dietary components for adequate function. When physiological processes
are pushed towards the extremes, as occurs in high yielding dairy cows and fast
growing beef cattle, nutrition becomes even more critical to maintain optimal health
and productivity. In these circumstances there is simply less margin for error.
Although many health disorders in dairy cows are multi-factorial, nutritional elements
are increasingly recognised to play an important role. Some dietary factors have been
characterised and documented, such as the role of energy in ketosis and calcium in
hypocalcaemia. Other aspects of nutrition are being elucidated, for example,
nutritional effects on immune function and dietary cation-anion balance. However, it
is also essential to remember that nutrition is only one factor influencing health, and a
holistic approach to preventive medicine needs to consider all factors, including farm
management and the epidemiology of any micro-organisms involved.
The basic principle of dairy cow nutrition is to match supply to demand. Feed
components are often divided into fractions of energy, protein, fibre, minerals and
vitamins, and calculations made of the requirements of a cow at a particular level of
productivity. A significant problem faced by nutritionists is that genetics,
management procedures and increasing output change over time and therefore the
‘supply – demand’ equation is not static. The demands of a 10,000 kg per annum
modern Holstein cow are clearly very different to an historic 5,000 kg Friesian.
Understanding the exact nutritional requirements of cows under huge physiological
demand is one of the challenges to those conducting research in this area. The more
accurately requirements are understood, the easier it is to supply rations that maximise
health and productivity and therefore improve welfare and profitability on dairy
farms. Fully unlocking the secrets of dietary influences on health, production and
reproduction would be great progress indeed.
The Nutritionalist and the Vet!
Although nutrition has an important influence on cow health, it is by no means the
only influence. Because of this several problems tend to arise:
1. We as vets tend to focus on our strengths, e.g.
 The organism(s)
 Preventive treatments
 Some management issues
 Sometimes poor understanding of nutritional elements
2. Nutritional advisors tend to concentrate on their strengths, and this can result in
 Over-emphasis on nutrition at the expense of other aspects
 Sometimes bizarre claims, and lack of perspective!
 Furthermore, there is sometimes a lack of science surrounding some claims.
3. Vets and nutritionalists don’t share their expertise well enough!
Main health topics in dairy cows
Infertility, Mastitis, Lameness, Metabolic disease
Infertility
 Important to keep perspective on factors causing infertility e.g: stockman (Heat
detection, DIYAI), environment, semen / bull, disease (direct and indirect).
Energy is the over-riding influence. The effects of negative energy balance (NEB) is
far reaching and an example from one research project is shown below:
% pregnant
Days open
NEB
Cyst
Serv/conc.
Clin.
ketosis
Mastitis
Lameness
There are broadly 2 modes of action of NEB on fertility
1. Long term (60-80 days prior to ovulation)
2. Short term (1-2 weeks prior to ovulation)
Cull
Long term energy affect:
Energy deficit 60-80 days before ovulation may
 Affect subsequent viability of egg
 Influence likelihood of abnormal oestrus cycles in the next lactation
 Energy deficit in the late dry period results in compromised hepatic function and
this influences fertility
Fat mobilisation and fatty infiltration of the liver are associated with
 milk fever
 mastitis
 endo/metritis
 displaced abomasum syndrome
 retained placenta
 infertility
 sub-optimal production
Shorter term energy affect:
Theories for this include
 Negative energy balance causes a suppression of pulsatile GnRH and LH
secretion
 Negative energy balance reduces luteal function (lower progesterone
concentrations) in 2nd and 3rd luteal phases.
 Effects on growth hormone and insulin leading to insulin-like growth factors
productn (liver) and possible effect on: hypothalamic-pituitary system, ovary,
reproductive tract and embryo.
Monitoring energy balance is important and methods to do this include:
 DMI (Are they eating what you think)
 Production (Milk protein, yield)
 Fertility (Pregnancy rates, oestrus intervals = clues)
 Condition scoring***
 Metabolic profiles
 Dung events
Dietary Protein and Infertility
 Links not absolutely clear.
 Possible problems with excess EDRP in relation to FME
 Never exceed 19% CP in lactating diet?
Minerals / Vitamins and Infertility
Often over-rated as a cause of infertility
 Molybdenum (Cu) – important in a few specific geographical areas
 I (stillbirths, retained placenta, and subsequent reproductive problems)
 Se / Vit E (periparturient problems)
 Ca (indirect via hypocalcaemia)
+ nearly all others suggested (but generally unimportant), including
 Phosphorus




Beta-carotene
Vit A
Cobalt
Manganese
Mastitis and Somatic Cell Counts
PERSPECTIVE needed here because many factors are more important than nutrition
in influencing mastitis. UK research has indicated, however, that trigger factors for
mastitis may be important. Research suggests that the most important nutritional
triggers are negative energy balance, vitamin E and selenium. Other less probable
candidates include copper, zinc, vit A.
Lameness
Another highly complicated and multi-factorial disease, that cannot be solved solely
through nutrition. Nutritional components are not all clear cut;






Subclinical acidosis / lack of buffering?
Changes around calving?
Sudden changes of diet?
Biotin clinically shown to reduce white line disease
? Zinc
High carbohydrate (acute laminitis) - rarely an issue in dairy cows
Metabolic disease
a. Hypocalcaemia
A primary nutritional disease but not only important for the clinical syndrome.
Subclinical hypocalcaemia is associated with;
 Slow calvings
 Poor uterine function post partum
 Poor rumen function and DMI
Prevention of hypocalcaemia, 2 basic methods;
 Calcium restriction (< 50g Ca and Mg ~ 50g)
? problems if K very high
 True DCAB diet
mEq (Na+ + K+) - (Cl- + S2- )
Add anions to make ~ -50 to -200 Meq/kgDM
Add Ca above to 80g – 150g?
Measuring urine pH is essential to monitor the DCAB system.
b. Displaced abomasa (DA)
Risk factors (including nutrition) are poorly determined. Most likely nutritional
elements are NDF and long chop fibre.
Summary
Nutrition is clearly important for dairy cow health, but needs to be seen in perspective
with other risk factors for disease. Some nutritional claims would benefit from more
substantial evidence and peer-reviewed research offers the best route to provide this
evidence. Vets and nutritional advisors should work closely together to achieve best
results for dairy cow health.