engleski

The effect of seasonal thermal stress on lipid mobilisation, antioxidant status and reproductive performance in dairy cows

Heat stress is a major factor contributing to low fertility of dairy cows with a great economic impact in dairy industry. Heat stressed dairy cows usually have reduced nutrient intake resulting in a higher degree of negative energy balance (NEB). The aim of this study was to investigate the seasonal thermal effect on lipid metabolism, antioxidant activity and reproductive performance in dairy cows. Thirty two healthy dairy heifers were included in the study. According to the ambient temperature animals were divided in two groups: winter (N=14) and summer season (N=18). Metabolic parameters and PON1 activity and total antioxidative status (TAS) were monitored at the time of insemination (basal values) and from 1 week before until 8 weeks after calving. Number of services per conception and calving to conception (CC) interval were calculated from the farm recording data. Serum triglycerides, NEFA and BHB concentrations were significantly increased after calving in summer compared to winter indicating higher degree of NEB in cows during summer. PON1 activity was significantly decreased after calving in both summer and winter group. TAS concentration was significantly lower in summer than in winter. A significantly higher number of services were needed for conception in summer compared to winter and CC interval was significantly longer in summer than in winter as well. Additionally, reproductive performance significantly correlated with the severity of NEB suggesting that lipid mobilisation and lower antioxidant status contributed to poor reproduction ability in dairy cows during hot months.

energy metabolism; oxidative stress; calving to conception interval

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