Productive and reproductive performance of Uruguayan Holstein and Uruguayan Holstein x New Zealand Holstein Friesian cows in a predominantly pasture-based system

摘要

The performance of Uruguayan Holstein (UH) and UH x New Zealand Holstein Friesian first cross (UH-NZHF) 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 O.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 UH-NZHF cows produced more milksolids per kg of BW~(0.75), (P O.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.