Performance of Beef Steers Fed Grain Diets in a Tropical Climate. 1. Climatic Factors

摘要

An increasing number of beef and dairy animals are being fed high energy diets in confinement in an attempt to increase animal performance and consistency of supply and products. Maintaining high levels of performance is difficult under conditions ofhigh temperature and high relative humidity which adversely affect animal performance. High ambient temperatures have been shown to decrease the net energy of a diet (Armstrong et at, 1959) and result in an increase in rectal temperature, body temperature, and respiratory rate (Kibler et al., 1949; Ol-brich et al, 1973). Cattle respond to heat stress by either reducing feed intake which also lowers performance (Blaxter and Wainman, 1961; Thompson et al., 1954) consuming a diet lower in fiber to reduce body heat production (Bond and McDowell, 1972; Cummings, 1992), or increasing water intake (Johnson et al., 1963; Lofgreen et al, 1975). Animals also attempt to reduce heat stress by heat dissipation which is dependent on wind movement and relative humidity. Heat stress in animals is a combination of factors that includes temperature and relative humidity (Armstrong, 1994). Animals are able to withstand high temperatures provided that the relative humidity is low. The objectives of this study were to evaluate the effects of random climatic variables on the performance of steers fed high energy diets in confinement.