Abstract
The aim of this paper was to determine the microclimatic conditions (ambient temperature and relative humidity) in dairy farm, as well as to evaluate the effect and significance of temperature - humidity index (THI) values on the daily milk yield. The observation of microclimatic parameters was conducted in the period from 9.03.2012 to 6.05.2012. The study included 136 Holstein Friesian cows. The estimation of the effect of THI on daily production of dairy cows was defined by applying fixed-effect statistical model. Average ambient temperature during measuring months amounted to 15.6?C (ranging from 7.2? C to 24.6?C), while the average value of relative humidity was 56.33% (ranging from 40.30% to 81.80%). During the study, the mean value of THI was 58.93 (ranging from 47.08 to 70.13) and didn?t exceed the critical comfort level of 72. All tested fixed-factors were statistically affected the daily milk yield (p <0.01). For each unit of increase in the value of the THI, the amount of milk decreased by 0.05344 kg. This confirmed the importance of regular recording of THI values and microclimatic conditions as a unique indicator of thermal stress in dairy farm.
Highlights
Heat stress can have a very negative impact on milk production, reproduction and general health of cows (Kadzere et al, 2002; West, 2003; Hansen, 2007)
In regard to heat stress, the most important factors are classified as ambient temperature and relative humidity (Ravagnolo and Misztral, 2000; Bouraoui et al, 2002; Correa - Calderon et al, 2004)
Based on the research of microclimate conditions as well as the effect of temperature-humidity index values on the daily production of dairy cattle, it could be emphasized that there were no conditions for the occurrence of heat stress during the experiment period because temperature humidity index (THI) didn’t exceed the critical comfort level of 72
Summary
Heat stress can have a very negative impact on milk production, reproduction and general health of cows (Kadzere et al, 2002; West, 2003; Hansen, 2007). In regard to heat stress, the most important factors are classified as ambient temperature and relative humidity (Ravagnolo and Misztral, 2000; Bouraoui et al, 2002; Correa - Calderon et al, 2004). Yielding dairy cattle in lactation show the most sensitivity to heat stress (Cincović, 2010). Influence of negative climatic factors may cause a decrease in milk production of lactating cows from 3% to 10% (Hristov et al, 2007). Acording to West (2003), when the ambiental temperature is 35°C, milk production decreases by 33%, and when the temperature is 40°C, milk production reduces to 50%. Thermoregulatory capabilities of cattle mostly depend on the ambient relative humidity level and temperature. A unique indicator for environmental thermal stress was created, the temperature humidity index (THI) (Mc Dowel et al, 1976)
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