TDK conference 2017

The aim of our research was to investigate the underlying relationship between calving and different weather condition parameters, in a selected dairy farm, from Hungary. In our study we processed the data of calvings from a year long period of time (altogether 501 cow calvings, 242 first-calf heifers, from wich 387 were female, and 331 were male calves). The average lenght of gestation was 278,4+-4,5 days on this specific farm. Based on our collected data, we could identify two associations independent from weather parameters. First, that the length of pregancy is significantly (p<0.05) shorter in first-calf heifers, than in cows (278,4±4,3 vs. 277,4±4,9), and secondly that female calves are born after a significantly (p<0.05) shorter gestation period, than the male ones (279,4±4,7 vs. 277,5±4,4). We based our statistical analyses on the further parameters: the type of calving (cow or heifer calving, heifer or bull calf) compared to different weather parameters, (temperature and temperature humidity index, or THI), and to cathegories compiled from these parameters.In this study we found, that if the change in the temperature was higher than 20°C in a 24h long period before the calving, the length of pregnancy was significantly shorter in cows (3.4-4.2 days), compared to the cathegories where no such extreme change in temperature was observed. We also identified that if during the 72 hours before the calving in cows, the difference between the minimum and the maximum values of temperature was higher than 12°C, the length of pregancy was significantly shorter again, compared to the group of cows who calved after moderate temperature changes. We furthermore examined the effect of difference between the temperature extremities (more than 14°C) during the 168 hours before the calving, and we found that the same negative correlation occured between the lenght pregnancy and the temperature changes. We also conducted analyses on the group of bull calvings regarding the corrations between the gestation period and the temperature changes. We found that if the difference in temperature extremities were higher than 35°C, but under 40°C, the pregnancy was significantly longer, compared to the group, where the same temperature changes were under 35°C. Regarding the THI values in cows, before 72 hours, and also before 168 hours calving, the lenght of gestation was significantly shorter in both groups, if the maximum THI values were above 73, compared to the group of cows with lower THI values. The THI values showed no further significant correlations with any of our cathegories created. Based on all these results, our hypothesis, that weather conditions can influence the pregnancy in dairy cattle is correct. We found that weather parameters have significant correlations with the length of gestation under certain circumstances. The results of our present study could provide an excellent basis for any future researches in this topic.