The following problems are associated with cows that are too fat during the dry period.
Long period of low intakes and negative energy after calving.
Increased chances of milk fever, fatty liver, ketosis, difficult calving, retained placenta and displaced abomasum.
30% lower feed intake in early lactation
Based on these findings, there is obviously no alternative to having dry cows at the correct condition score (CS).
Ideally, cows should be dried off around CS 3-3.25, and be maintained at that condition until calving. Loss of condition between calving and breeding has a major effect on fertility. Large scale Moorepark farm trials indicate that cows which lose a half CS or more have a much lower conception rate than those losing only a quarter.
Transition feeding of a few kgs of properly balanced concentrates for a few weeks prior to calving is successful in many herds, because it minimises the reduction in intake before calving and conditions the rumen for higher levels of concentrates after calving. This is particularly important in high yielding autumn calving herds, where high levels of concentrates are fed after calving.
A sudden change in diet after calving can potentially lead to acidosis, if high levels of concentrates are fed. Concentrates should be introduced gradually, especially where transition feeding is not practiced.
Rumen pH samples from sample herds tested by UCD indicated that a quarter of herds may suffer from sub-acute acidosis (in other words, it may not be obvious). This often leads to laminitis, reduces feed intake, causes negative energy balance and excess loss of body condition in early lactation, and reduces mounting behaviour.
Sub Clinical Milk Fever
About five to seven per cent of cows get clinical milk fever (hypocalcaemia), where they may go down and require veterinary treatment. However, 20% to 39% of cows can be affected by sub-clinical hypocalcaemia around calving and later in the lactation, with the following symptoms — slow calving, retained placenta, low feed intakes after calving, reduced immune system, delayed ovulation after calving, reduced fertility and low blood calcium for up to 45 days after calving.
It is likely that sub-clinical hypocalcaemia causes many unexplained problems. Where problems are suspected, they should be thoroughly investigated with blood tests, etc.
Dry cow diets should be properly supplemented with high quality minerals and trace elements (Teagasc formulations), especially for six weeks before calving. They should have sufficient bulk in their diet, and concentrates should be introduced to their diets a few weeks before calving. This reduces the period of inadequate intake before and after calving.
Every farmer should have a milk fever control strategy. This should include regular body condition scoring, ensuring magnesium supplement is fed (0.4% of diet), and limiting access to high-K and high-N forage. Average Irish silage has 2.3% K, but forage should ideally have less than 1.8% K.
Even though high quality grass is and will remain the most important aspect of dairy cow nutrition, it is equally important to have cows in proper condition and properly supplemented throughout the whole year, especially the dry period. Ideally, silage should be tested to formulate proper dietary requirements for all stock. Silage quality is not as good as expected this winter on some farms.
Global research is ongoing with feed additives to improve the health and fertility of dairy cows and get more milk from the same amount of feed. While good husbandry and maintaining cows in the correct CS at critical times will always be a priority, proper balancing of diets and feed additives have an important role to play in optimising profitability from herds. In the meantime, farmers should use the EBI information to breed more fertile and productive cows, have a good herd health programme in operation and use the maximum amount of high quality grass in the diet. The future of dairying depends on matching progress in genetics with progress in nutrition and health care and that is not generally happening on Irish dairy farms at present.
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