How does a beef x dairy calving affect the dairy cow’s following lactation period?

Abstract: In dairy x beef breeding, much of the research has focused on the performance of the crossbred calves, yet little focus has been given to the subsequent performance of the cow itself. This study aimed to evaluate the performance of dairy cows for milk yield, fertility, and survival traits after giving birth to crossbred calves, and to compare this to the performance of dairy cows after giving birth to purebred dairy calves. Phenotypic records from 4,980,886 calving events distributed in 4,509 herds from 1997 to 2020 were collected from the Swedish milk recording system from cows of the dairy breeds Swedish Red and Swedish Holstein. A total of 13 performance traits were defined and grouped in three large complexes as follows; cumulative and 305-day milk, fat, and protein yield as milk yield traits; calving to first insemination interval, calving to last insemination interval, first to last insemination interval, calving interval, and number of inseminations as fertility traits; and survival to next calving and last day in milk as survival traits. The data were analyzed for all traits for first and later parities separately using mixed linear models, with a focus on the estimates of sire breed by dam breed combinations. All traits were adjusted for previous milk yield for parities 2-3 based on the expectation that low-yielding cows would more likely be inseminated with beef semen. Overall, milk yield was lower after mating beef x dairy compared to the purebred matings. The largest decrease was about 400 kg for cumulative milk yield when breeding Charolais sires with purebred SR or SH dams. As for fertility traits, for most breed combinations, the effects were not large enough to be significant. Conversely, all sire-dam breed combinations showed significantly lower results for survival traits, suggesting that cows inseminated with beef semen have a lower probability to survive to the next lactation.