Calving at 24 months for optimum economic and lifetime performance
February 16, 2021
In order to maintain dairy herd size it is necessary to have a good supply of quality heifers to replace animals that have to be culled. Gavin Duffy, CAFRE Dairying Adviser, states “age at first calving and the herd replacement rate are two of the main factors which determine how many heifers are required in any given year.”
Rearing dairy heifer replacements to the point of calving is an expensive investment on most dairy farms. The rearing period is the financially non-productive part of the animal’s life and it has a direct effect on both the total cost of rearing and the time taken for each individual heifer to pay this investment back. The Royal Veterinary College investigated in detail on-farm heifer rearing costs in 2017. They estimated that it took on average one and a half lactations for the heifer to repay her investment in the rearing period but this ranged from one to six lactations. The repayment period is not only influenced by the cost of rearing but also by the farm milk price, the production output, variable costs and, to some extent, herd fertility.
Calving at 24 months has been shown to be the optimum for economic and lifetime performance but it is important that heifers meet key targets at critical stages in the rearing programme. Gavin highlights a number of recent CAFRE calf webinars which discussed good management practices in the birth to weaning period to get the heifer off to a good start and included the importance of nutrition, health and the calf’s environment.
Management of the herd in the close up dry period needs careful attention to ensure the cow or heifer gives birth to a healthy calf and has an adequate supply of good quality colostrum. Recent research shows that improved performance in the early calf stage can have positive benefits throughout the heifer’s productive life time. The calf has the potential to grow extremely quickly during this period so there is an opportunity to capitalise on accelerated growth by paying more attention to feed management and in particular milk feeding.
In addition to the improved liveweight performance, Gavin says “research evidence also suggests that by increasing milk or milk replacer intake early in life, the calf’s genetics are somehow altered, known as epigenetic programming, which has a positive effect on the heifer’s subsequent milk yield. However, this early period is also a time when the calves are most vulnerable to disease so paying close attention to calf health and its environment will help realise these gains.”
Although that first 100 days of the calf’s life is only a small proportion of the total heifer rearing period, management in these early days has been shown to have a significant influence on the lifetime performance of the dairy replacement. In conclusion Gavin suggests that by taking a whole life approach to heifer rearing there is potential on most dairy farms to make small improvements in their heifer rearing enterprise that will pay financial dividends in the longer term.
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