بررسي بعضي عوامل محيطي بر عملكرد توليد مثل در گاوهاي هلشتاين استان گيلان

Study of the effects of environmental factors on reproduction performance in Holstein cows of Guilan province

In this research, 8760 records of dairy cattle of a farm (with two herds) in Guilan province were studied. Effects of season, year, sex of calf, lactation number, herd, milk yield (first 150-day) and age of cow on reproduction performance were evaluated. Means of days to first service (DFS), days open (DO), service per conception (SIC) and calving interval (CE) were 86.64±0.34 days, 124.57±0.63 days, 2.17±0.02 time and 409±0.71 days, respectively. Effect of season on reproductive factors was significant (P<0.01). Reproductive performance in autumn and spring was maximum and minimum, respectively; also the year effect was significant (P<0.01). Effect of lactation number on reproductive factor was significant (P<0.05). Effect of age was significant on DO, DFS and Cl (P<0.01), However its effect on SIC was not significant (P>0.05). Effect of milk yield on DFS and SIC was significant (P<0.01). Effect of sex of calf on reproductive performance was not significant (P>0.01). The results of this study suggest that, Holstein cows of Guilan province have the most suitable reproductive condition in lactation number 3 and autumn calving. Also milk yield (first 150-day) has significant effect on days to first service and service per conception.