|SANS-FERNANDEZ, VICTORIA - Iowa State University|
|JOHNSON, JAY - Iowa State University|
|ABUAJAMIEH, MUHAD - Iowa State University|
|STOAKES, STEVEN - Iowa State University|
|SEIBERT, JACOB - Iowa State University|
|Kahl, Stanislaw - Stass|
|ROSS, JASON - Iowa State University|
|RHOADS, ROBERT - Virginia Tech|
|BAUMGARD, LANCE - Iowa State University|
Submitted to: Physiological Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2015
Publication Date: 2/25/2015
Citation: Sans-Fernandez, V.M., Johnson, J.S., Abuajamieh, M., Stoakes, S.K., Seibert, J.T., Kahl, S., Elsasser, T.H., Ross, J.W., Rhoads, R.P., Baumgard, L. 2015. Effects of heat stress on carbohydrate and lipid metabolism in growing pigs. Physiological Reports. 3(2):1-17.
Interpretive Summary: Heat stress confounds the efficiency of pig production by decreasing the rate of gain of heat challenged pigs and prolonging the grow out period. In order to better understand why this occurs, information of the basic effect of heat stress on metabolism is needed. More specifically, information useful to advisors of the pig industry in formulating strategies to mitigate heat stress effects on growth might be ascertained if a better understanding of how the hormones that regulate nutrient use, hormones like those of the insulin and thyroid axis, are affected by heat stress. We applied a controlled, uniform heat stress to pigs that simulated the ambient environmental temperatures attained in the southeast U.S. in summer. Our metabolic data indicated that effects beyond the obvious decrease in feed intake accompanied the decrease in growth rate as impacted by heat stress. Overall, the usual metabolic responses that reflect rapid weight gain were compromised by heat stress including glucose utilization, insulin functions, fatty acid metabolism and thyroid status at both the levels of the thyroid gland and the peripheral tissues. Based on these data, diets may be formulated to contain nutrients better metabolized by pigs under conditions of heat stress.
Technical Abstract: Heat stress (HS) jeopardizes human and animal health and reduces animal agriculture productivity; however, its pathophysiology is not well understood. Study objectives were to evaluate the effects of HS on basal and stimulated energetic metabolism. Crossbred female pigs (57±5 kg body weight) were subjected to two experimental periods. During period 1, all pigs remained in thermoneutral conditions (TN; 20°C) and were ad libitum fed. During period 2, pigs were exposed to: 1) constant HS conditions (32°C) and ad libitum feeding (n=7), or 2) pair-feeding in TN conditions (PFTN; n=10) to eliminate the confounding effects of dissimilar feed intake. All pigs received an intravenous glucose tolerance test (GTT) on d2 of period 1, and d1 and 6 of period 2; and an epinephrine challenge (EC) on d3 of period 1, and d2 and 7 of period 2. After 8 d of environmental exposure, all pigs were sacrificed and tissue samples were collected. Despite a similar reduction in feed intake (39%), HS pigs tended to have decreased circulating non-esterified fatty acids (NEFA; 20%) and a blunted NEFA response (71%) to the EC compared to PFTN pigs. During early exposure, HS increased basal circulating C-peptide (55%) and the basal C-peptide to glucose ratio (54%), but decreased the insulin to glucose ratio (45%) in response to the GTT compared to PFTN conditions. Heat stress further compromised the conversion of T4 to T3. In summary, HS markedly alters both lipid and carbohydrate metabolism independently of nutrient intake.