Effects of dairy products on intestinal integrity in heat-stressed pigs

Abstract

Heat stress compromises intestinal integrity which may partially explain its negative effects on animal health and productivity. Research suggests that challenged intestinal barrier function improves with dietary dairy products in various models. Thus, the study objective was to evaluate the effects of bovine milk whey protein (WP) and colostral whey protein (CWP) on intestinal integrity in heat-stressed pigs. Crossbred gilts (39 ± 3 kg body weight) were fed 1 of 4 diets (n = 8 pigs/diet): control (Ct), control diet containing an 80% WP and 20% CWP product (WP80), control diet containing a 98% WP and 2% CWP product (WP98), and control diet containing a 100% WP product (WP100). After 7d on experimental diets, pigs were exposed to constant heat stress conditions (32 °C) for 24h. There were no treatment differences in growth or body temperature indices prior to heat stress. During heat exposure, both rectal temperature and respiration rate increased (+0.85 °C and 3-fold, respectively; P < 0.01), and feed intake and body weight decreased (44% and -0.5kg, respectively; P < 0.01), but neither variable was affected by dietary treatments. Plasma L-lactate and D-lactate concentrations increased (36%; P < 0.01) and tended to increase (19%; P = 0.09) with heat stress. After 24h of heat exposure, WP100-fed pigs had lower plasma D-lactate relative to Ct-fed pigs. Ileal transepithelial electrical resistance was decreased (37%; P = 0.02) in WP80 pigs, compared with controls. No differences were detected in other intestinal integrity ex vivo measurements. These data demonstrate that dietary WP and CWP did not mitigate intestinal integrity dysfunction during severe heat stress.

Keywords: dairy products; heat stress; intestinal integrity; pigs.

Figure 1. Effects of feeding diets containing no test product (Ct), or 80% milk whey protein (WP) + 20% colostral whey protein (CWP; WP80), 98% WP + 2% CWP (WP98), 100% WP (WP100) test products on (A) rectal temperature and (B) respiratory rate of pigs exposed to constant heat stress conditions (32 °C) for 24 h. ^a,b,c Represent differences between hours of heat stress (P ≤ 0.05). *Represents the average values during period 1.

Figure 2. Effects of feeding diets containing no test product (Ct), or 80% milk whey protein (WP) + 20% colostral whey protein (CWP; WP80), 98% WP + 2% CWP (WP98), 100% WP (WP100) test products on plasma (A) L-lactate, (B) D-lactate, and (C) lipopolysaccharide binding protein (LBP) concentrations of pigs during period 1 (P1; thermoneutral conditions: 19 °C; ~46% humidity) and at the end of period 2 (P2; heat stress conditions for 24 h: 32 °C; ~26% humidity). *Represents differences between treatments during period 2 with period 1 as a covariate.