High Environmental Temperature Induces Oxidative Stress, Reduced Sow Productivity and Increased Piglet Mortality

Abstract

Heat stress is a limiting factor for livestock productivity in many countries. This study was designed to evaluate the influence of exposure of exotic pigs to high environmental temperatures on physiology, oxidative stress biomarkers and productivity. Multiparous sows (n = 40) in two equal groups (Groups N and H) were investigated. The pen temperature, relative humidity and Temperature-Humidity Index (THI) were measured for 30 days. The skin temperature, respiratory rate and rectal temperature were measured weekly. Haematology, serum biochemistry and oxidative biomarkers were also evaluated. The production records, including farrowing events (NFE), number of piglets at birth (NPB), number of piglets at weaning (NPW) and piglet mortality (NPM) were obtained per sow for the preceding 24 months. Data were analyzed using descriptive statistics and a student T-test at P<0.05. Pen indoor temperature was significantly higher and relative humidity significantly lower in Group H (30.23+0.99 0 C, 48.90+7.94 %) compared to Group N (25.21+0.94 0 C, 58.97+6.21 %). The THI was higher in Group H (78.40+1.99). There was a significant increase in skin surface temperature and respiratory rate in Group H (37.70+1.40 0 C and 39.70+4.28 bpm) with a slight increase in rectal temperature compared to Group N (33.86+0.95 0 C and 35.79+2.89 bpm). There was a slight increase in PCV, blood urea nitrogen and a decrease in the levels of sodium, chloride, and bicarbonate in sows in Group H. There was a significant increase in hydrogen peroxide generation, nitric oxide contents and malondialdehyde levels, with a decrease in superoxide dismutase activity and glutathione content in Group H when compared to Group N. There was a reduction in farrowing events (N = 3.45+0.20; H = 3.00+ 0.19), number of piglets at birth (N = 29.15+1.92; H = 27.95+ 2.44), the number of piglets at weaning (N = 27.65+1.89; H = 25.90+ 2.25), and an increase in piglet mortality (N = 1.5+0.21; H = 2.05+0.42) in sows exposed to higher temperatures. The orientation of the pig housing in the northsouth direction reduced its effectiveness. Exotic sows exposed to heat stress had altered physiology, experienced oxidative stress, were prone to renal and hepatic injury, and had reduced productivity. Adequate thermal comfort should be ensured in pig husbandry in the tropics for optimal health and productivity.