Drying off nutrition
It is important to realise that the heavily pregnant cow is unlikely to put on more than half a condition score over the last two months of pregnancy.
In addition to this the weather is at its worst and the temperatures are at their lowest over winter, so the cow's maintenance is at its maximum. The cow's condition at calving is important not only for its milk production over the coming season but also its reproduction.
The key to feeding cows at this time of the year is to enable the farmer to get the maximum production over the last few months of lactation and be able to dry them off as quickly as possible to reduce the effect on weight loss. This involves feeding dairy cows on good quality pasture with or without the addition of silages. Maize silage is particularly good for putting on weight. This should ensure production is maximised with the additional energy going into body condition.
Cows have a high demand for trace elements and this does not stop because they are dried off. Check on your herd's trace element status by either having the works take liver samples from cull cows or your vet taking liver biopsies from around ten cows in the herd. In this area copper and selenium deficiencies are common and to a lesser extent Vitamin B12 (cobalt).
The high demand times for copper are late lactation when the calf demands a large amount from the cow, calving, peak lactation, mating and for optimum growth in young stock.
Ideally selenium levels should be high at the time of calving to ensure uterine involution is rapid and complete and to produce a healthy viable calf. Rapid uterine involution should minimise chances of even sub-clinical uterine infection and speed return to oestrus.
As well as trace elements, the availability of macro elements is also extremely important (particularly magnesium, calcium and phosphate). All cows must have good levels of these to avoid the risk of metabolic disease. Magnesium levels should be monitored and corrected if low over the dry period. Low magnesium, while predisposing cows to clinical staggers, more frequently is associated with milk fever or ketosis at calving time. There are no large stores of magnesium in the body (unlike calcium stores in the bones) so regular intake is necessary. Soil levels appear to have fallen in recent years throughout New Zealand and on individual farms will be affected by fertiliser practices, especially by potash and lime application, and also by pasture composition.
The other major concern is mastitis or, more correctly put, the herd's somatic cell count. You should use your herd testing results throughout the season, including the last herd test to determine who needs dry cow treatment. We are keen to assist farmers in this area and during your dry-cow consultation will discuss all these points.
Many trials have been done and the results conclusively show that dry-cow therapy (DCT) is more effective than milking-cow therapy in curing existing infections, particularly those that have become sub clinical or chronic. The preventative nature of DCT has been shown to reduce the incidence of dry-cow mastitis and the level of new infections over the early spring period. The use of teat seal may also be appropriate especially it you have a number of cows coming in with mastitis, but you should seek professional advice before going ahead.