|Chaffin, Roxanne -|
|Spiers, Donald -|
Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: November 4, 2011
Publication Date: June 25, 2012
Citation: Sanchez, N.C., Chaffin, R., Carroll, J.A., Chase, C.C., Coleman, S.W., Spiers, D.E. 2012. Heat stress decreases the metabolic response of Angus but not Romosinuano heifers to an LPS challenge. Journal of Animal Science. 90:22(E-Suppl. 1). Technical Abstract: Differential metabolic responses between heat tolerant and heat sensitive Bos taurus breeds to lipopolysaccharide (LPS) when housed at different ambient temperatures (Ta) was studied. Angus (AG; n=11; 306+/-26 kg body weight) and Romosinuano (RO; n=10; 313+/-32 kg body weight) heifers were transported from Florida to Missouri where they were housed in stanchions in four temperature-controlled environmental chambers. Initially, Ta in all four chambers was cycling at thermoneutrality (TN; 18.5 to 23.5C) for a 1-week adjustment period, followed by an increase in two chambers to cycling heat stress (HS; 18.5 to 38C) for 2 weeks. On day 19, heifers were fitted with jugular catheters. On day 20, heifers were challenged with LPS (0.5 microgram/kilogram body weight; 0 hr) and blood samples were collected from -2 to 8 hr and at 24 hr relative to LPS challenge at 0 hr. Serum was isolated and stored at -80C until analysis for glucose, insulin, and non-esterified fatty acid (NEFA) concentrations. Pre-challenge glucose concentrations were greater in RO (P=0.01) heifers and greater in heifers housed in TN (P=0.02). Post-challenge glucose initially increased before decreasing below baseline concentrations (P<0.01) in all heifers. There was a breed x Ta interaction such that AG heifers in HS had the lesser post-LPS glucose concentration (P<0.01) compared to RO heifers and AG heifers at TN, which did not differ (P>0.88). Pre-LPS NEFA concentrations were not affected by breed (P=0.37) or Ta (P=0.60), but did decrease over time (P<0.01). Post-LPS NEFA concentration was also not affected by Ta (P=0.78), but there tended to be a breed x Ta interaction (P=0.07) such that NEFA was greater in RO than AG at HS (P=0.01), while NEFA in heifers at TN did not differ from each other (P=0.89) or from heifers at HS (P>0.12). Pre-LPS insulin concentration was not affected by Ta, but was greater in RO than AG (P<0.01). Post-LPS insulin increased (P<0.01), with RO producing a greater insulin response than AG (P<0.01). These data suggest that HS decreases the metabolic response of AG heifers in response to LPS challenge, thus providing physiological evidence that may explain differences between heat sensitive and heat tolerant cattle breeds.