Influence of seasonal thermal stress on lipid mobilisation and oxidative stress results in diminished reproductive performance in dairy cows
2019
Zrim?ek, Petra | Mrkun, Janko | Podpe?an, O?balt | Turk, Romana | Mirilovi?, Milorad
Environmental heat stress compromises efficient animal production including reproductive performance in dairy cows. Dairy cows in early postpartum period experience a rapid increase in milk yield, whereas animal feed consumption ability rises slowly and cannot follow increased needs for nutrients. The negative effects of heat stress on reproduction are thought to be a consequence of poor appetite and reduced nutrient intake resulting in a negative energy balance (NEB). The results indicate that fat to protein ratio in milk (FPR) can be used in predicting of prolonged calving to conception interval in dairy cows. In our study we confirmed that lipid mobilisation during NEB is associated with an oxidative stress. We also showed that seasonal thermal stress affects the lipid metabolism, antioxidant activity and reproductive performance in dairy cows. Heat-stressed cows inseminated during hot months in comparison to winter had lower fertility rate (lower conception rate and prolonged calving to conception interval) coupled by a higher degree of NEB confirmed with lipid mobilisation (increased non-esterified fatty acids (NEFA) and beta hydroxybutyrate (BHB)) and lower antioxidant status (decrease in total antioxidant status (TAS) and paroxonase-1 (PON1) activity).
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