No abstract

The aim of this study was to evaluate the heat stress influence of milk production from primiparous and multiparous Holstein Friesian cows and to estimate economic losses associated with the decrease in the farm’s milk yield. The cows selected for the study were in the middle phase of the 1st, 2nd, and 3rd lactation and were characterised by similar daily milk production. Additionally, the animals were kept in the same conditions and fed with the same feeds throughout the season. The analysis covered two 30-day periods – ‘cold’ (April), in which no days with THI >70 were noted, and ‘hot’ (July), in which THI was above 70 for 90% of the days (74.4 on average). The average daily drop in milk production noted in the hot period was 1.25 kg/cow for multiparous cows and 2.78 kg/cow for primiparous cows. The average daily financial loss resulting from a drop in milk production was €0.55/day/cow in primiparous and €0.46/day/cow in multiparous animals. The calculated daily loss in the profit on production of 1 kg of milk was €0.27/day/kg for primiparous and €0.24/day/kg for multiparous animals. Based on test results, economic losses were simulated depending on the daily milk yield and the size of the primary cattle herd. For the multiparous cows, the estimated losses ranged from €6.07/day (farm sizes 25 cows and average daily milk yield 25kg) to nearly €219/day (900cows/ 25kg). In larger facilities (900 cows) with an average daily milk yield of 55 kg, the daily loss will be about €481. The obtained results confirmed the assumptions made that with a change in microclimate conditions in the barn, a decrease in the daily production and changes in the milk chemical composition were noted, and the economic efficiency of the studied activity decreased.