TY - JOUR
T1 - Shade effects on performance, carcass traits, physiology, and behavior of heat-stressed feedlot heifers
AU - Mitlöhner, F. M.
AU - Galyean, M. L.
AU - McGlone, J. J.
PY - 2002/8
Y1 - 2002/8
N2 - To determine whether shade influences performance, carcass traits, immunology, respiration rate, and behavior of cattle under conditions similar to those in commercial feedlots, we used 168 heifers in 12 soil-surfaced pens. Six pens were shaded with a galvanized steel-roofed shade (approximately 4 m high), allowing for 2.12 m2 of shade/heifer, and six pens served as the unshaded control. Heifers were fed a 90% concentrate diet during the 121-d trial that began in mid-June, performance variables (DMI, BW, ADG, gain:feed) were measured, and dietary concentrations of NEm and NEg calculated from performance data. A blood sample was collected to assess immune measures. Respiration rates and behaviors (feeding, drinking, walking, standing, lying, agonistic, and bulling) also were measured during the study. Carcass data (yield grade, kidney, pelvic, and heart fat, longissimus muscle area, hot carcass weight, quality grade, liver abscess rate, and incidence of dark-cutting beef) were collected at slaughter. Shaded heifers had higher (P < 0.05) DMI, ADG, and final BW than unshaded heifers. The gain:feed ratio and calculated dietary NEm and NEg concentrations did not differ (P > 0.26) between treatments. Most carcass traits did not differ between treatments, but more (P < 0.02) carcasses of heifers in shaded pens graded USDA Choice than those in unshaded pens, which resulted primarily from the incidence of dark cutters being decreased (P < 0.04) by approximately half in carcasses from shaded compared with unshaded heifers. Respiration rate and percentage of circulating neutrophils were decreased (P < 0.01) for shaded compared with unshaded heifers. The treatment x time of day effect was significant (P < 0.05) for all behavioral measurements. Shaded heifers spent more time laying down (0800, 1200, and 1500, P < 0.05) and less time standing (1200 and 1500, P < 0.05) than unshaded heifers. Agonistic behavior was less (P < 0.05) for shaded than for unshaded heifers at 1900 and 2000, and bulling was less (P < 0.05) for shaded than unshaded heifers at 2100. Results suggest that shade improved performance and altered behavior by feedlot heifers during the summer-time in West Texas.
AB - To determine whether shade influences performance, carcass traits, immunology, respiration rate, and behavior of cattle under conditions similar to those in commercial feedlots, we used 168 heifers in 12 soil-surfaced pens. Six pens were shaded with a galvanized steel-roofed shade (approximately 4 m high), allowing for 2.12 m2 of shade/heifer, and six pens served as the unshaded control. Heifers were fed a 90% concentrate diet during the 121-d trial that began in mid-June, performance variables (DMI, BW, ADG, gain:feed) were measured, and dietary concentrations of NEm and NEg calculated from performance data. A blood sample was collected to assess immune measures. Respiration rates and behaviors (feeding, drinking, walking, standing, lying, agonistic, and bulling) also were measured during the study. Carcass data (yield grade, kidney, pelvic, and heart fat, longissimus muscle area, hot carcass weight, quality grade, liver abscess rate, and incidence of dark-cutting beef) were collected at slaughter. Shaded heifers had higher (P < 0.05) DMI, ADG, and final BW than unshaded heifers. The gain:feed ratio and calculated dietary NEm and NEg concentrations did not differ (P > 0.26) between treatments. Most carcass traits did not differ between treatments, but more (P < 0.02) carcasses of heifers in shaded pens graded USDA Choice than those in unshaded pens, which resulted primarily from the incidence of dark cutters being decreased (P < 0.04) by approximately half in carcasses from shaded compared with unshaded heifers. Respiration rate and percentage of circulating neutrophils were decreased (P < 0.01) for shaded compared with unshaded heifers. The treatment x time of day effect was significant (P < 0.05) for all behavioral measurements. Shaded heifers spent more time laying down (0800, 1200, and 1500, P < 0.05) and less time standing (1200 and 1500, P < 0.05) than unshaded heifers. Agonistic behavior was less (P < 0.05) for shaded than for unshaded heifers at 1900 and 2000, and bulling was less (P < 0.05) for shaded than unshaded heifers at 2100. Results suggest that shade improved performance and altered behavior by feedlot heifers during the summer-time in West Texas.
KW - Behavior
KW - Feedlots
KW - Heat Stress
KW - Performance
KW - Physiology
KW - Shade
UR - http://www.scopus.com/inward/record.url?scp=0036689603&partnerID=8YFLogxK
U2 - 10.1093/ansci/80.8.2043
DO - 10.1093/ansci/80.8.2043
M3 - Article
C2 - 12211371
AN - SCOPUS:0036689603
VL - 80
SP - 2043
EP - 2050
JO - Journal of Animal Science
JF - Journal of Animal Science
SN - 0021-8812
IS - 8
ER -