Publikationsdatenbank

The influence of heat load in dairy cows housed in naturally ventilated barns in different climate zones (2020)

Art

Hochschulschrift

Autor

Pinto, Severino (WE 10)

Quelle

Mensch und Buch Verlag, 2020 — 62 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/26367

Kontakt

Institut für Tier- und Umwelthygiene

Robert-von-Ostertag-Str. 7-13
14169 Berlin
+49 30 838 51845
tierhygiene@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Due to their sensitivity to high temperatures, heat stress effects are prevalent in highyielding dairy cows. To reduce uncertainty in the influence of heat stress, detailed representative and individual animal measurements should be considered. Therefore, the overall objective of this study was to investigate the influence of heat load on the respiration rate (RR) of lactating dairy cows housed in naturally ventilated barns under different climatic conditions and management systems. In the first part of the study, the RR of lactating dairy cows in Germany was investigated hourly, with the aim of evaluating the effects of the temperature-humidity index (THI) on the cows’ responses considering the differences between standing and lying cows and daily milk yield as covariables in the analysis. The consideration of cow-related factors provided evidence for reducing the uncertainty in the heat stress assessment of dairy cows. In detail, with THI below 80, the RR in lying cows tended to be 8 bpm higher than that in standing cows, and the RR in high-yielding cows increased one bpm for each additional kilogram of milk produced per day. Although the first paper showed evidence of cow-related factors influencing RR in cows housed in naturally ventilated barns in a moderate climate, it remained unclear whether the same effect would be observed in high-yielding dairy cows housed under hot climate and high humidity conditions but supplied with cooling management systems for body stabilization. Therefore, in a second part of the study, the aim was to investigate the RR responses of high-yielding dairy cows cooled at two different frequencies per day (3 cooling sessions vs. 8 cooling sessions) and analyze the differences in the RR according to body posture (standing vs. lying), daily milk yield and coat color (black, mixed and white). As noted in the first part of the study, hourly RR measurements were also applied to the second study, which was conducted in Israel during the summer season. The results of this study demonstrated that heat-stressed cows receiving eight cooling sessions per day showed an average RR 14 bpm less than that of cows that received three cooling sessions. Additionally, the cows cooled eight times per day demonstrated a heat accumulation delay of approximately two hours in their RR response. Unlike the experiment in Germany, the Israeli experiment, which was conducted in a hot and humid climatic region, showed a RR 9 bpm higher in standing cows than in lying cows. Daily milk yield also appeared to be an influencing factor on the RR, whereby the cows tended to increase their RR by one bpm per every five kilograms of additional milk produced per day. In addition, the RR (in bpm) in early-lactation cows was 17% higher than that in late-lactation cows. Overall, this study demonstrated that hourly RR measurements improve the reliability of heat stress assessments in dairy cows. Future research should consider the efficiency of evaporative cooling in dairy husbandry considering energy consumption, labor expenditure, animal management and welfare. In addition, other cow-related factors should be evaluated in further research to verify influences on the physiological responses of lactating dairy cows under heat stress conditions and in different cooling strategies.