Influence of Heat Stress on Milk Production in Fraternal Twins

The aim of this study was the evaluation heat stress in milk production dairy cows (daily yield; 1st lactation). comparison performed between fraternal twins (full sisters), produced on same farm and parity. One a hot period whereas her sister cooler period. Also, there can be differences twins. Therefore, second group also created that without stress. Databases were analysed using PROC GLM analysis Statistica® with selected effects. In conclusion, negative effect found. There an obvious tendency (in some cases insignificant) for worse during both daily yield days lactation started season. Fat content %) lower but insignificant. On other hand, found very low (and components) season