نوع مقاله : مقاله پژوهشی
نویسندگان
1 نویسنده مسئول، گروه علوم دامی، گرایش تغذیه نشخوارکنندگان، دانشکده کشاورزی، دانشگاه صنعتی اصفهان، اصفهان، ایران. رایانامه: rajaeerad@iut.ac.ir
2 گروه علوم دامی، گرایش تغذیه نشخوارکنندگان، دانشکده کشاورزی، دانشگاه صنعتی اصفهان، اصفهان، ایران. رایانامه : ghorbani@iut.ac.ir
3 گروه علوم دامی، گرایش فیزیولوژی دام، دانشکده کشاورزی، دانشگاه صنعتی اصفهان، اصفهان، ایران. رایانامه: m.choupani@ag.iut.ac.ir
4 گروه علوم دامی، گرایش ژنتیک و اصلاح نژاد، دانشکده کشاورزی، دانشگاه صنعتی اصفهان، اصفهان، ایران. رایانامه: ali.jabar1121@gmail.com
کلیدواژهها
عنوان مقاله English
نویسندگان English
Objective: Heat stress in dairy cows is a common problem that affects metabolic balance, transition period management indices, and postpartum health, particularly in hot and dry areas, such as Isfahan province, Iran. This study aimed to evaluate the effects of season (summer vs. winter) and the severity of heat stress on calving-related management indices, body condition, metabolic disorders, serum calcium status, and reproductive outcomes in Holstein dairy herds in Isfahan province.
Method: The study was conducted as a completely randomized design in four industrial Holstein dairy herds in Isfahan Province, Iran, during summer and winter seasons, with 855 dairy cows. Daily meteorological data were recorded to calculate the temperature–humidity index (THI). Body condition score (BCS) at calving, gestation length, dry period length, colostrum yield, incidence of metabolic disorders (retained placenta, metritis, hypocalcemia, and ketosis), culling rate up to 60 days postpartum, and conception rate at first AI were recorded. Serum calcium concentration was measured at calving and on day 3 postpartum, and serum beta-hydroxybutyrate concentration was measured on day 10 postpartum. The data were analyzed with appropriate statistical models, considering the effect of season, herd, parity, and their interactions. All statistical assumptions including normality of residuals and homogeneity of variances were tested and confirmed before final analysis.
Results: THI values ranged from 74 to 82 during the summer, suggesting moderate to severe heat stress. Gestation length was shorter in primiparous cows than in multiparous cow within each herd (P<0.05). Body condition score at calving was influenced by herd management (P<0.05). Colostrum yield was lower in multiparous cows compared to primiparous cows (P<0.05), and tended to decrease during the summer season (P=0.07). Dry period length also decreased during the summer (P<0.05). The incidence of retained placenta and metritis was influenced by season, herd, and parity, with the highest incidence in the winter season (P<0.05). While dystocia was higher in summer (P<0.05), serum calcium concentration was lower in summer than in winter (P<0.05). The prevalence of hypocalcemia and ketosis, especially in multiparous cows, was also higher in summer (P<0.05). The culling rate up to 60 days postpartum was higher in Herd C during both seasons.
Conclusion: Findings of this study showed that herd management and lactation parity differences were significant factors in the occurrence of metabolic disorders and calving-related factors; heat stress reduced the occurrence of retained placenta and metritis, but limited dry period length and colostrum yield in dairy cows.
کلیدواژهها English
