A Study of Selected Environmental Factors on Feed Intake of Performance-Tested Beef Bulls

摘要

Feed intake data from 52 140-d feeding trials and selected environmental data were analyzed to define more precisely the relationship between environmental factors and feed intake of performance-tested beef bulls. Feed intake data originated from bulls (n = 2,002) in University of Arkansas Cooperative Bull Tests at Fayetteville, Hope and Monticello from 1978 to 1990. Bulls were given a 21-d adjustment period, then individually full-fed a total mixed ration (TMR) twice daily in the same stall for 140d. Initial age and weights were recorded at the beginning of each test and at 28-d intervals. Environmental data were obtained from the National Climatic Data Center (Asheville, N.C.). Data were pooled, divided into five 28-d periods with each period analyzed separately. Feed intake was influenced by initial age in all periods (P< 0.01) and initial weight in periods 3 through 5 (P < 0.01). Initial weight x breed interactions (P < 0.01) were present in periods 1 and 2. Thermal Heat Index (THI) x breed interactions (P < 0.01) were evident in all periods. Relative humidity from 0600 to 1000 h (RH6-10) influenced intake (P < 0.01) in period 2, with RH6-10 x breed interactions (P < 0.01) evident during periods 3 and 4. A rainfall x breed interaction (P < 0.01) also existed during period 4. Results suggest that environmental effects on feed intake are strongly influenced by breed, and that initial age and weight of cattle when placed on feed affect intake throughout the feeding period.