Put focus on calf rearing
Get farm conditions right to keep mortality low
Spring is one of the busiest times of year on a dairy farm. Cows are calving, heifers need to be trained into the parlour and calves have to be looked after. Although it is an extremely busy time of year, it is still worth putting a big effort into rearing your calves to the best of your ability. After all, the calves you rear today will be the herd of 2013.
If replacement heifer calves are to reach the specified critical weight targets throughout the rearing process, you need to start aiming to achieve these weights from the day the calf is born. Of course, it is also essential to minimise mortality and illness levels on the farm. This will give greater scope to cull more cows from the milking herd in two years' time or will allow expansion and growth of the herd, but ultimately it will reduce costs incurred due to illness.
At birth, a calf's immune system is not fully developed. Colostrum (biestings) contains antibodies and growth factors, and is superior in nutritional value when compared with whole milk. Colostrum imparts passive immunity from the dam to the newborn calf via intestinal absorption of antibodies and should be fed for the first three days after birth.
Calves are dependent on adequate consumption of good-quality colostrum to boost initial levels of vitamins such as A, D and E. Most of the essential minerals and vitamins are substantially more concentrated in colostrum than in milk. For example, colostrum usually contains 6-10 times the amount of vitamin D present in ordinary milk. Inadequate feeding, or quality, of colostrum is a primary cause of low immunity in calves. In addition, deficiency of trace elements and vitamin E in the diet of the cow in late pregnancy can compromise the immune system of the young calf. This may increase susceptibility to scour, pneumonia, navel-ill, joint-ill, etc.
On farms, colostrum management is the single most important factor in determining calf health and survival. A failure of passive transfer of antibodies from colostrum contributes to excessively high pre-weaning mortality rates and other short- and long- term losses associated with animal health, welfare, and productivity. A successful colostrum management programme requires farmers to consistently provide calves with a sufficient volume of clean, high-quality colostrum within the first few hours of life.
As time from birth increases, the ability of the calf to absorb antibodies is reduced. Absorption is greatest in the first few hours of life and starts to decline progressively after four to six hours, and ceases after 24 hours from birth. Therefore, it is critical to feed colostrum as soon as possible after calving to ensure maximum immunity is acquired, as the most critical time in a calf's life is during the first few days, when morbidity and mortality are greatest.
The ideal source of colostrum is the calf's dam, for two main reasons. The first is centred on concerns about the potential spread of Johne's Disease, while the second is that by drinking its mother's milk, the calf will acquire immunity to fight pathogenic organisms encountered on the home farm.
Ideally calves should be given 2-3 litres of colostrum by oesophageal tube or by nipple feeding within four hours of birth, with a total of four litres within 12 hours of birth. Leaving calves to suckle colostrum from their dam is not recommended as there is no guarantee that they will have a sufficient intake. The amount of colostrum that calves drink voluntarily does not change within the first four hours after birth, so there is no benefit in delaying first feeding.