Abstract
Background and Aim:Metabolism and environment are closely related. Under high ambient temperature (HTa), dairy cows may have different energy metabolism during summer and winter. The present study was carried out to investigate the effect of HTa on the milk yield and blood concentration of beta-hydroxybutyrate (BHBA) and glucose at the herd level.Materials and Methods:One large dairy farm in Thailand with more than 100 crossbred Holstein cows milked each month was selected. The first experiment was performed on non-lactating cows to determine the normal daily concentrations of blood BHBA and glucose. Under the HTa condition, there was no significant change in blood BHBA and glucose concentrations. The second experiment was performed using a prospective cohort clinical design to demonstrate the seasonal effect on milk yield and blood BHBA as an indication of energy metabolism at the herd level.Results:The temperature and humidity index for the winter (78.1±0.5) and summer (83.4±0.7) periods differ significantly. The average milk yield during the winter period was 17.8% higher than during the summer period. The reduction of body condition score (BCS) during early lactation was significant in the winter cows. Both higher milk yield and lower BCS in the winter cows suggested a state of negative energy balance. However, there was no difference in blood BHBA and glucose concentrations between winter and summer cows. The effect of HTa on insulin signaling appeared to be a counterbalancing factor for the ketogenic status. Based on the present results, it would be interesting to further investigate the incidence of subclinical and clinical ketosis in a dairy farm under tropical conditions.Conclusion:The present experiment revealed that HTa during summer decreased milk yield in dairy cows fed under tropical conditions. Higher milk yield in winter caused a greater reduction of BCS and suggested a greater negative energy balance. However, there was no seasonal effect on blood BHBA and glucose concentrations.
Highlights
The main climate of Thailand is tropical savannah based on the Köppen–Geiger climate classification [1]
The reduction of body condition score (BCS) during early lactation was significant in the winter cows
The present experiment revealed that high ambient temperature (HTa) during summer decreased milk yield in dairy cows fed under tropical conditions
Summary
The main climate of Thailand is tropical savannah based on the Köppen–Geiger climate classification [1]. There are generally three main seasons in Thailand [2]: Rainy season (mid-May to mid-October), winter season (mid-October to mid-February), and summer season (mid-February to mid-May). We had previously demonstrated that milk yield per day from dairy cows during summer was 16% lower than during winter [3]. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Under high ambient temperature (HTa), dairy cows may have different energy metabolism during summer and winter. The present study was carried out to investigate the effect of HTa on the milk yield and blood concentration of beta-hydroxybutyrate (BHBA) and glucose at the herd level
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