The first of a series of three free webinars called “A veterinary view on cattle nutrition”, organised by Elanco Animal Health, was held on 3rd September, led by Dr Finbar Mulligan, a member of the Dairy Herd Health Group based at the veterinary school at Dublin.
Dr Mulligan gave the 500 vets registered for the series a superb in-depth talk at this first webinar, explaining where vets had a vital role to play in this area of herd health management. He covered the direct disease consequences of inappropriate transition cow nutrition and the indirect consequences that extend well into the following lactation, discussing the practical approach to vets’ involvement in planning nutrition and the key parameters of disease and nutrition to monitor.
Importance of the period
The reason the transition period is of such importance is because the majority of dairy cattle disease occurs in the periparturient period, or are associated with it, e.g. retained foetal membranes, milk fever, displaced abomasum, laminitis.
A study in Danish dairy cattle involving over 93,000 cows, demonstrated that the total disease incidence (cases per 100 cows) peaked between calving and the first 10-15 days post-calving.1 Appropriate nutrition in the transition period can prevent disease and in the speaker’s opinion, is a beneficial strategy.
The main objective of a transition cow nutrition programme should be to achieve a healthy transition period and a productive, fertile next lactation.
Parameters to consider
Finbar explained that the most important aspects of nutrition for vets to consider were:
- managing body condition score (BCS);
- major minerals and calcium status;
- trace elements and antioxidants
- attention to detail in the close-up period with regard to energy balance depressions, rumen fill and dietary changes, from a dry cow to a lactating cow diet.
Managing BCS is the single most important aspect of transition cow nutrition. The speaker said that large animal vets must be capable of advising on BCS and this could be incorporated into fertility visits, pre-breeding examinations or at pregnancy scanning. The most progressive farmers are already beginning to expect this service. Finbar gave the recommended target BCS for key stages of the lactation cycle (see Table 1).
A high BCS at calving can have several deleterious consequences such as ketosis (which is often missed), infertility, suppression of the immune system, difficult calving and milk fever, amongst other diseases.
A low BCS at calving of 2.5 or less can cause subsequent fertility problems, as observed by the UCD Dairy Herd Health Group. They found that low BCS at calving can cause anoestrus as well as a reduced milk yield.
The Dairy Herd Health Group encourages farmers to measure and record BCS at key times. They also train farmers to measure BCS by palpation, not just by visual judgement, and to calculate the number of cows that are off-target.
Ideally, there should be 90% or more of cows with the correct BCS. Changes in BCS can be made by adding more energy than needed or restriction diets. BCS changes will happen slowly and any diet restriction in the dry period must begin at drying off and end 2-3 weeks before calving.
Restriction diets still need to provide 85% of daily energy requirements. Thin late-lactation cows may be dried off a few weeks early, given extra feed or only milked once a day.
Major minerals
As most cattle vets are aware, 5-10% of dairy cows succumb to clinical milk fever.2 However, another 20-39% will get subclinical hypocalcaemia around calving time and later in lactation.
Subclinical hypocalcaemia is associated with reduced immune system function3 and reduced fertility by delaying the first ovulation after calving.4 The risk factors for milk fever and subclinical hypocalcaemia include a low feed intake at calving, a high BCS at calving, older cows, Jersey cows and Jersey crosses and ingestion of forages high in either potassium or sodium or low in magnesium.
Vets should liaise with nutritionists to look at the levels of dietary potassium, sodium, chloride and sulphur on each farm and to review farm specific grass silage analysis, e.g. the DCAD (dietary cation and anion difference) strategy. The aim is to get the DCAD figure negative, between -150 and zero on the full DCAD strategy or between zero and +150 on the partial DCAD system. Dietary magnesium levels also need to be assessed and should be 0.4%.
Anti-oxidants
Anti-oxidants, particularly vitamin E, selenium, beta-carotene, vitamin A, copper, zinc and chromium, are important for the function of the immune system peripartum. There is often a deficiency of them in the forage so they will usually need to be supplemented.
The last two weeks before calving is the time when it is extremely important to avoid a drop in feed intake and energy balance, because of the association with an increased risk of displaced abomasum and immune system suppression. Around calving a dip in immune function is expected but if the cow also has a depression in energy balance, the immune system will function at a much lower level than cows without such an energy deficit.
Reasons for a drop in food intake at this time can be due to a variety of husbandry issues such as availability of food, or forage quality. The speaker emphasised the importance of avoiding any drop in feed intake or any additional stress for the cows in these two weeks. The feeding environment must be optimal and cows not subject to stressful changes such as transport.
Reduced food intake is also associated with a big increase in the risk of developing a displaced abomasum. Ninety per cent of left displaced abomasums (LDA) occur within one month of calving, and 50-86% occur within two weeks of calving, essentially because the drop in food intake reduces rumen fill and predisposes to displacement of the abomasum.
Low forage diets also increase the risk for the same reason. High levels of rumen fill are important at calving, so the cows need a good intake of a high forage diet at this time.
Change of diet from dry to lactating cow
Abrupt changes of diet at calving from a low net energy to a high net energy one are associated with rumen acidosis and increased hoof damage, according to research with confined herds diets.5
The speaker said that studies at UCD with grazing cows also show that dairy cows should be gradually changed over to the new diet rather than abruptly switched. For example, newlycalved cows can be turned out to graze immediately but it’s better from a nutritional point of view to keep them in at night for the first week, or longer for high yielders.
Summary
The speaker summed up the webinar with the following key points:
- The correct BCS is important at calving, and the vet must be able to advise on this and encourage the farmer to measure and record BCS values.
- Dietary magnesium and potassium are the most important factors to maintain an optimal calcium metabolism.
- Adequate anti-oxidants are required for immune system function (selenium and vitamin E especially).
- Attention to detail in the last two weeks before calving, particularly regarding: optimal cow comfort and husbandry for good food intake; avoiding depressions in energy balance; ensuring sufficient rumen fill; ensuring gradual changes in diet at calving.
1. Ingvartsen et al (2003) On the relationship between lactational performance and health: is it yield or metabolic imbalance that cause production diseases in dairy cattle? A position paper. Livestock Production Science 83 (2-3): 277-308. (www.sciencedirect.com/science/… S0301622603001106)
2. Houe et al (2001) Milk fever and subclinical hypocalcaemia – an evaluation of parameters on incidence risk, diagnosis, risk factors and biological effects as input for a decision support system for disease control. Acta Veterinaria Scandinavica 42 (1): 1-29 (http:// europepmc.org/abstract/MED/11455889)
3. Goff, J. P. (2006) Major Advances in Our Understanding of Nutritional Influences on Bovine Health. Journal of Dairy Science 89 (4): 1,292-1,301. (www.sciencedirect.com/science/… S002203020672197X)
4. Jonsson, N., Pepper, P. M., Daniel, R. C., McGowan, M. R. and Fulkerson, W. J. (1999) Association between non-parturient postpartum hypocalcaemia and the interval from calving to first ovulation in Holstein-Friesian cows. Animal Science 69 (2): 377-383. (http://espace.library.uq.edu.a… 43645)
5. Donovan, G. A., Risco, C. A. et al (2004) Influence of Transition Diets on Occurrence of Subclinical Laminitis in Holstein Dairy Cows. Journal of Dairy Science 87 (1): 73-84.
