Cortisol and blood urea nitrogen profiles in fertile and repeat-breeder holstein-friesian crossbred cows

Abstract

Background and Objective: Repeat breeding, in which conception fails after repeated inseminations is a major problem in the dairy industry that leads to economic losses. To examine the role of stress under this condition, this study was conducted to evaluate cortisol and blood urea nitrogen (BUN) levels in fertile and repeat-breeder Holstein-friesian crossbred cows in smallholder farms. Materials and Methods: Thirty cows were divided into two groups: Fertile and repeat-breeder cows, with 15 cows per group. Blood samples were collected from the caudal vein at night, 8 h after feeding, once in the oestrus phase during two oestrus cycles and cortisol levels were analyzed by using an enzyme-linked immunosorbent assay with a commercial kit. The BUN was analyzed by the urease and glutamate dehydrogenase method. Results: Significant differences in cortisol and BUN levels were observed between fertile and repeat-breeder cows. Cortisol levels were higher in the repeat-breeder group (6.860±1.427 ng mL-1) compared to those in the fertile group (3.145±1.103 ng mL-1). Furthermore, BUN levels were also higher in repeat-breeder cows (31.45±4.70 mg dL-1) than in fertile cows (27.30±2.69 mg dL-1). Conclusion: Cortisol and BUN levels above the normal range may contribute to repeat breeding in Holstein-friesian crossbred cows.