Effect of differing forages on the early growth and behaviour development of dairy heifers during pre- and post weaning periods : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
The objective of this study was to evaluate the effects of different forage diets fed to young calves on early growth, behaviour development and long term milk performance. In experiment 1, 60 calves were randomly allocated to one of three diets, fed starter diet with no forage (PS), PS with additional moist alfalfa (PSA) or PS with additional pasture hay (PSH). In experiment 2, 108 calves were randomly allocated to one of three diets, PSH, PS with low (LF) or high (HF) moist alfalfa based total mixed rations. In Experiment 1, greater dry matter intake and liveweights were observed in PSH followed by PSA and then PS during the pre- and post-weaning periods. Longer time eating and ruminating behaviours were observed in PSA and PSH than PS during pre- and post-weaning periods. In Experiment 2, greater dry matter intake and liveweights were observed in PSH than LF and HF diets during the pre- and post-weaning periods. Greater numbers of incidents of allo-grooming were observed in the HF and PSH diets and calves spent longer time eating than LF calves. During post-weaning period, HF and PSH fed calves spent more time lying than LF fed calves. After turning out to pasture, no behaviour differences were observed among treatments in both experiments. While monitoring long term performance, no differences were observed in animals from Experiment 1 in terms of liveweight, milk yield, protein or fat production. From Experiment 2, greater liveweight gains were observed in HF and PSH fed animals than LF fed animals till first lactation. During first lactation, greater milk yield was observed in HF fed animals than PSH or LF fed animals. Greater fat production was observed in LF fed animals than HF or PSH fed animals during third lactation. The effects of diets on the long term performance of the animals should be repeated with sufficient animal numbers per treatment.