Abstract

Replacement heifers need to reach specific target live weights (LW) to ensure they calve as two year olds, and subsequently achieve high milk yields and good fertility. Currently, different LW targets are recommended for heifers based on their expected mature LW according to appearance or breed. However, the mature LW is difficult to estimate without knowledge of the animals. genetic potential for LW. The objective of this paper is to develop and validate a growth model which uses estimated breeding values for LW (EBV LW) of individual heifers of any breed to calculate target LW from birth to maturity. Predicted live weights are presented for a range of four EBV LW, from –40 to 100 kg. These values were very similar to other published target values. Data from the Dexcel Holstein Friesian Strain Trial was used to validate the model with respect to LW and age at puberty. For LW at puberty the predicted values were significantly correlated (P<0.05), but were marginally higher (3-5%) than the actual values. A report can be formulated to enable farmers to identify individual heifers which are below (or above) their target LW at any date

JR, Bryant, CW Holmes, N Lopez-Villalobos, LR McNaughton, IM Brookes, GA Verkerk, and JE Pryce

Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 118-121, 2004