This study investigated the effects of pre-calving live weight on milk production in first lactation New Zealand dairy heifers. Heifers were classified into five breed groups; Holstein-Friesian (F), Holstein-Friesian crossbred (FX), Jersey (J), Jersey crossbred (JX) and Holstein-Friesian-Jersey crossbred (FJ). There was a curvilinear relationship between live weight at 21 months of age and protein and fat yields for all breed groups. The relationship between live weight and milk yields was curvilinear for all breed groups apart from J which had a linear relationship only. At most live weights, F heifers produced more than J heifers, however, all breed groups produced similar yields when heifers were lighter (260 – 325 kg) at 21 months of age. For lighter heifers the response to a one kg increase in live weight was greater compared with heavier heifers, indicating there could be greater benefits of preferentially feeding lighter heifers to attain heavier pre-calving live weights. Within the live weight range studied (260 – 600 kg) there was no live weight at which maximum milk or protein yields was achieved. An increase in live weight was also associated with an increase in milk and protein yields for all breed groups. For fat yield, the maximum production was achieved by J heifers that were 497 kg. For all other breed groups, the maximum yields were predicted to be at live weights greater than 658 kg; beyond the live weight range studied. These results show the potential to increase first lactation milk production of New Zealand dairy heifers by increasing pre-calving live weight. Keywords: live weight, milk yield, dairy heifer, growth
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Biology & Species - Bovine (dairy) 1, , 126, 2018
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