engleski

The variability in persistency of heat stress effect in dairy cattle due to breed and breeding region

Aiming determination of the variability in persistency of heat stress effect in dairy cattle regarding the breed and region test-day records provided by the Croatian Agricultural Agency were analysed. Only cows with detected statistically significant decrease in daily milk yield at set temperature-humidity index (THI) threshold value (68, and 72) were included in the further analyses. The persistency of heat stress effect was determined as absolute drop in daily milk yield in the subsequent milk recordings (1st and 2nd). The results of this research indicate high variability in persistency of heat stress effect in dairy cattle due to breed (Simmental, and Holstein), breeding region (Eastern, Central and Mediterranean Croatia), and individual’s susceptibility to heat stress (animals heat stressed at lower or higher THI (68 / 72) value. Since the genetic evaluation and selection of animals that are more resistant to heat stress is only long-term method to mitigate the impact of climate change, these factors should be taken into account in the models for genetic evaluation.

heat stress; persistency; dairy cattle; breeding region; breed

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