Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2006
Publication Date: 6/20/2006
Citation: Laspius, J.P., Farmer, C., Ku, P.K., Zanella, A., Kerr, B.J., Trottier, N.L. 2006. Insulin, glucose, cortisol, growth hormone and prolactin responses to oral l-arginine supplementation to lactating sows under heat stress. Journal of Animal Science. 86:373-377. Interpretive Summary: The amino acid arginine is essential for growing mammals because the rate of endogenous arginine synthesis cannot meet the arginine needs for optimal growth and health. Although endogenous arginine synthesis rate is sufficient to meet requirements for maintenance and gestation in the sow, it is unknown whether it is adequate to maximize milk synthesis during lactation in heat-stressed sows. Impaired lactation performance such as increased body weight loss and decreased milk production has been well documented in sows exposed to high ambient temperatures. Excessive loss of body weight during lactation results in extended weaning to estrous interval and potentially impairs subsequent reproductive performance. Any reduction in reproductive performance has a subsequent impact on feed nutrient utilization, and consequently on the impact of pork production on the environment. The objective of this study was to determine whether increasing dietary arginine intake may modify endocrine function in heat-stressed sows to improve reproductive performance. The data show that plasma insulin and prolactin concentrations did not differ due to environmental temperature. Plasma growth hormone and glucose concentrations, however, were higher and salivary cortisol lower in sows maintained in the hot environment versus the thremoneutral environment. Arginine supplementation increased plasma insulin concentration but decreased plasma growth hormone concentration. Dietary arginine had no effect on plasma prolactin and glucose, or salivary cortisol. In summary, arginine may mediate the reduced sow weight loss and increased feed efficiency by regulating both insulin and growth hormone metabolism. Research results described in this report provides nutritionists at universities and feed companies data indicating that dietary concentrations of arginine may need to be considered in diets fed to lactating sows for optimization of reproductive performance, and ultimately to minimize nitrogen excretion.
Technical Abstract: The objective of the study was to determine whether dietary arginine (Arg) decreases weight loss of lactating sows via regulation of key metabolic hormones. Sows were exposed to a thermoneutral (TN = 20º C) or hot (HT = 29.4º C) environment and fed one of three dietary treatments in a 2 x 3 factorial design. Dietary treatments were corn-soybean meal based diets formulated to contain 0.96%, 1.34%, and 1.73% Arg for control (C), medium (ME), and high (HI) dietary treatments, respectively. Blood samples were obtained 2 h post-meal on day 7, 14, and 21 of lactation. Plasma insulin and prolactin concentrations did not differ (P < 0.10) in HT sows when compared to TN sows. Plasma growth hormone (P < 0.05) and glucose (P < 0.01) concentrations were higher and salivary cortisol lower (P < 0.05) in HT sows compared to TN sows. Arginine supplementation increased plasma insulin concentration (P < 0.05) in sows fed the HI and ME diet compared to C in both environments. Growth hormone concentration in plasma decreased in sows fed the ME and HI diets compared to C diet in both environments (P < 0.05). Plasma prolactin and glucose, and salivary cortisol did not differ (P < 0.10) between C, ME, and HI diets. Arginine may mediate improvement in nutrient utilization by regulating both insulin and growth hormone metabolism.