The live weight of replacement heifers on commercial dairy farms in comparison to breed guidelines.

Replacement heifer rearing is often neglected on dairy farms because for farmers the cost of rearing heifers apparently outweighs the advantage of well grown-out heifers. These advantages manifest in early conception and milk yield. To investigate trends in heifer raising, weights for age as a measure of heifer feeding programs were studied in the Western Cape.

In the study the weight for age of replacement heifers on five commercial dairy farms was recorded with the aim to derive descriptive growth curves for breeds and to compare the observed weights to literature guidelines. All replacement heifers on one Ayrshire, one Holstein and three Jersey dairy herds were weighed once a month over a three year period. Heifers weighed varied in age from day-old to 36 months of age. The recorded weight of the heifers was regressed on age in days using suitable growth functions. The growth curves of the heifers for the different breeds could best be described by quadratic instead of linear equations, confirming the well-known observation that growth does not follow a linear pattern. The average daily gain of Holstein, Ayrshire and Jersey heifers from birth to 24 months of age was 0.45, 0.42 and 0.38 kg per day respectively. In comparison to literature guidelines the observed growth rates for Holstein and Ayrshire heifers were low. This resulted in them being much smaller than recommended weight for age targets. According to standard North American guidelines the minimum weight gains for Holstein, Ayrshire and Jersey heifers should be 0.70, 0.55 and 0.40 kg/day respectively. However, since the study was conducted on only five farms, for Holstein and Ayrshire being only one farm each, the results are not necessarily representative of the breeds in the Western Cape. It nevertheless raises concern. It should also be recognized that North American guidelines do not necessarily simulate South African conditions well, and therefore it is important that studies should be conducted locally to determine optimum growth rates and weights for age of heifers for dairy breeds in different regions and feeding systems. Such studies should also go further, by determining the effect of a poor growth rate on the milk yield of the heifers themselves and the probable total yield loss of the herd.

Reference

Muller, C.J.C., Burger, W.J. & Lamont, M.M.C., 2013. The live weight of replacement heifers on commercial dairy farms in comparison to breed guidelines. SASAS Congress 2013, Salt Rock, KZN.