A study to evaluate herd records related with the effect of heat stress on reproductive criteria and relation with milk yield

Heat stress is a serious problem in dairy farming. It results in lower milk yield, disturbances in reproduction, health problems and economic loss. Milk yields are a product of animal genetic and environmental interactions. Milk yield for a specific genotype, especially in tropical environments or ecosystems, is a function of climate and its interactive influences on the quantity and quality of feed, the presence of disease and parasites and the utilization of technology to alleviate nutritional, thermal and health limitations. In this study, in 30 year period (1973-2003) data were avaible from Black and White (BW), Israel Black and White (D3W) and South Anatolian Red (Kilis) cattle breeds and their crossbreeds kept at Research and Production Unit of the University Çukurova Faculty of Agricullture. In the study, 3683 parturation, 7813 breeding and 2321 lactation records were analysed and the results were discussed to asses the effect of heat stress on reproduction and milk production traits for Çukurova region. Average age at first breeding, age first calving and service period were calculated as 594±6, 895±6 and 135±3 days respectively. Calving intervals, days in calf and longevity were determined as 404±3, 277±0, respectively. Lactation period, lactation yield, 305- days lactation yield and length dry period were determined as 299±2 days, 4917±50 kg. 4885±46 kg and 77±2 days respectively. The differences betweeen month of calving were statistically significant (PO.01) for days open, calving interval, lacatation period, lactation milk yield, 305-days milk yield and length dry period for Black and White cattle under Çukurova regional conditions. This effect was determined statisticaly significant (PO.05) for age at first breeding. But the differences between the other characteristics were not statistically significant. Keywords: Heat stress, dairy cattle, progeny yield, milk yield.