|Briggs, Robert - Bob|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2001
Publication Date: 7/28/2001
Technical Abstract: Environmental stressors are frequently encountered in confined animal feeding operations. An experiment was conducted to determine the effect of Micotil and feedyard dust exposure on ADG, serum vitamins A (Vit A) and E (Vit E) concentrations, and rate of bovine respiratory disease (BRD) of feeder steers. One hundred and twenty crossbred feeder steers (average BW 185 kg) were purchased in Morristown, TN, and transported to Bushland, TX. One half of the steers received Micotil (1 ml/30 kg BW s.c.) in TN. Simulated dust storm was produced by having steers in an enclosed canvas tent. Calves were allotted randomly into 3 dust exposure groups: 1) Control (not exposed to tent or dust), 2) Tent (enclosed in tent without dust), and 3) Dust (exposed to dust suspension inside tent) and nested within Micotil treatments. There were four dust application events each lasting 4 h. Calves were weighed and blood samples taken in Morristown (d-3), arrival (d 0) and every 7 d for 28 d. The data were subjected to the analysis of variance using the General Linear Models procedure of SAS. Transportation stress reduced (P<0.001) serum Vit E concentrations from 7.10 to 1.95 ug/ml. There was no interaction (P>0.05) between the antibiotic and dust treatments. On d-28, the mean ADG of tent and dust groups was lower (P<0.02) than the controls (0.77 vs 1.26 kg/d). Similarly, the mean serum Vit E concentration of these steers was also lower (P<0.05) than the controls (1.88 vs 2.11 ug/ml). Micotil treatment sustained (P<0.001) serum Vit A and E concentrations of steers. As incidence of BRD increased (0 to 6), serum Vit A and E concentrations decreased (P<0.001) as well as ADG. These results suggest that environmental stressors decrease serum antioxidants corresponding with decreases in ADG.