RESUMO
The aim of this study was to compare the reproductive performance, milk production, live weight, and body condition loss during early lactation of purebred Holstein (H) cows to Jersey x H (J x H) crossbred cows in 4 Victorian herds. Cows of H and J x H breeding were managed together within each herd, and all herds had a seasonally concentrated calving pattern that commenced in early spring (July). All crossbred cows included in the study were 25, 50, or 75% H and were considered collectively as J x H regardless of the sire and dam breeds used to reach those percentages. Each herd owner provided records of reproductive performance and milk production. Compared with H cows, J x H cows had higher first-service conception rates (52 vs. 42%), higher percentages confirmed pregnant by 6 (68 vs. 54%) and 14 wk (86 vs. 78%) after the first day of inseminating, and lower final not-in-calf rates (11 vs. 16%); however, these differences were not observed in all herds. A random selection of H and J x H cows had body condition assessed on 3 occasions between the start of calving and the first day of the artificial insemination program. The selected cows were also weighed on the final occasion. Overall, body condition scores were slightly higher for J x H cows than for H cows, but changes in body condition score between calving and the start of inseminating were similar between breed groups. The H cows were 40 kg heavier than J x H cows and had daily milk yields in early lactation that were 2.2 kg higher. Daily yields of milk fat and protein did not differ between H and J x H cows during the study period. The improved reproductive performance of J x H cows compared with H cows may render them more suitable for use in dairy herds with seasonally concentrated calving patterns. Their improved reproductive performance was not associated with differences in condition loss in early lactation.
