Reproductive performance of Brown Swiss, Holstein and their crosses under subtropical environmental conditions.

Selection has been emphasized for increasing production traits with ignoring the fertility traits, which leads to a general loss of reproductive fitness. The aim of this study was to evaluate the reproductive performance of the pure Brown Swiss (BS), Holstein (HO), their first-generation crossbred (F1), and backcross (BC) cows under subtropical Egyptian conditions. The reproductive performance and health traits were measured in the pure BS, HO, their F1, and BC crossbred, in addition to investigating the impact of temperature-humidity index level (THI) on reproductive traits. Brown Swiss and her F1 had a better reproductive efficiency and health traits than in HO and BC. They possess a higher conception (34.1% and 36.9%, respectively) and pregnancy rates (32.8% and 31.1%, respectively), a shorter calving interval (401 and 420 days, respectively), and a lower average insemination per parturition (3.18 and 3.45, respectively), with a lower incidence of metritis (14.1% and 14.6%, respectively). Moreover, no difference has been detected in the fertility of BS with different THI levels, whereas F1 was slightly affected by increasing THI, especially for conception rate which declined from 43.1% at low to 24.1% at high THI. But the pregnancy rate did not change with different levels of THI. Our results indicate that BS and her F1 have a better reproductive performance and adaptability than pure HO and BC under subtropical Egyptian conditions. Furthermore, milk yield of the F1 crossbred is comparable to that of the pure HO cows.