The Effect of High Summer Temperatures on Reproduction in Holstein and Czech Fleckvieh

Abstract

The aim of this study was to evaluate the effect of the hot summer season on the length of service period (number of days from calving to the next conception). For the analysis was created two databases of twins. Twins had the same sire and dam and the first and second lactations took place on the same farm. In the first database (105 pairs) one of the twins was calved (and had the following service period) during the summer months and the second of the twin was calved in the cooler months. To compare the difference in service period between twins in the hot and cool seasons, it was made also second group of twin pairs with reproduction only during the cool period of the year (cool vs. cool season; 58 pairs). The data were analysed using PROC GLM of Statistica®. In addition to season, the effect of breed (Holstein, Czech Fleckvieh), milk production at 1st lactation and calving year were also taken into consideration. The results showed a significantly longer service period in the summer (133.8 days) than in the cool months (114.7 days). In the case of twins with reproduction in the cool months of the year, the difference between length of service period was shorter and insignificant (113.6 vs. 119.4 days).

Keywords

• heat stress
• service period