114 Monitoring the impact of shade and housing on physiological response in finishing beef cattle during the summer months in the Southeastern United States.

A study was conducted to evaluate the effect of heat stress on blood-gas parameters of beef steers finished with or without shade in the Southeastern United States. Thirty-two steers (BW 453kg +/-4 kg) were assigned to one of four treatment groups including: inside with fans (CWF), inside no fans (CNF), outside with shade (SHADE), and outside without shade (OUT). All animals were placed into their treatment on d-10 and were given 10 days to acclimate. Animals were fed individually and served as the experimental unit. Animals were weighed and arterial blood was collected on d-10, 0, and 50. Data were analyzed in a completely randomized designed utilizing a one-way ANOVA. Initial (d-10) pCO2 values were similar for all treatments (P >0.05). On d0, covered treatments (SHADE, CWF, and CNF) pCO2 values were greater than d-10 (P< 0.01), OUT values did not differ from d-10 to d0 (P = 0.95). The change in pCO2 values between d-10 to d0 values were similar for covered groups (P >0.14) and greater than OUT (P < 0.02). On d50 all treatment pCO2 values returned to baseline values (P = 0.50), and the change in pCO2 from d0 to d50 was greater for covered groups than the OUT group (P < 0.04) Initial d-10 pO2 values were similar for all treatments (P >0.05). On d0, covered treatments (SHADE, CWF, and CNF) pO2 values were less than d-10 (P < 0.01), OUT values did not differ from d-10 to d0 (P = 0.75). pCO2 values between d-10 to d0 were similar across all groups (P = 0.38). On d50 SHADE and CNF pO2 values were less than base line (P < 0.02). d50 pO2 values for OUT and CWF returned to baseline values (P >0.20). The change in O2 from d0 to d50 was similar across all groups (P = 0.84). These results suggest that there is a physiological difference between beef steers fed with cover versus beef steers outside. [ABSTRACT FROM AUTHOR]