The performance of Uruguayan Holstein (UH) and UH x New Zealand Holstein Friesian first cross (UHNZHF) cows was investigated over 1 year using 62 cows offered predominantly native pasture. Accumulated 305 day yields of milk, fat, protein and milksolids (fat+protein) were not affected by the strain. The UH cows produced 0.5 L/d more milk than UH-NZHF cows at Day 240 of lactation (P <0.05). Fat and lactose percentages were greater in UH-NZHF cows (3.72 vs 3.44% and 5.02 vs 4.94%, respectively, P <0.0001). Protein percentages tended to be greater in UH-NZHF cows (3.31 vs 3.27%, P = 0.08). The UH cows were 49 kg heavier (569 vs 520 kg, P <0.001) and required a greater energy requirement for maintenance. The UHNZHF cows produced more milksolids per kg of BW0.75, (P <0.01). Pregnancy rates tended to be greater in UH-NZHF cows (87 % vs 71%, P = 0.08) and were greater when the first 40 days of service were considered (61 vs 35%, P = 0.04), which may be related to a differential energy partitioning according to strains.
Proceedings of the New Zealand Society of Animal Production, Volume 70, Palmerston North, 306-310, 2010
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