The effects of dietary chromium(III) picolinate on growth performance, blood measurements, and respiratory rate in pigs kept in high and low ambient temperature

Three experiments were conducted to investigate the effects of thermal stress and dietary Cr on growth performance and physiological variables in weanling pigs. In Exp. 1, a total of 54 pigs (BW of 5.95 [+ or -] 0.84 kg) were allotted to a 2 x 3 factorial arrangement using 2 ambient temperatures (23.7 or 40.5[degrees]C during d 14 to 28 postweaning) and 3 dietary concentrations of Cr (0, 1,000, or 2,000 [micro]g/kg) as Cr(III) picolinate. In Exp. 2, a total of 54 pigs (BW of 5.94 [+ or -] 1.29 kg) were allotted in the same treatment arrangement but with different ambient temperatures (26.5 or 16.0[degrees]C during d 14 to 26 postweaning). In Exp. 3, a total of 36 pigs (BW of 6.40 [+ or -] 0.72 kg) were allotted in the same treatment arrangement with ambient temperatures of 25.9 or 13.8[degrees]C during d 14 to 28 postweaning. During d 0 to 14 of all experiments, a neutral ambient temperature (NT) was maintained. In Exp. 1, pigs in high ambient temperature (HT) gained less BW (575 vs. 663 g/d; P < 0.001) and consumed less feed (926 vs. 1,074 g/d; P = 0.001) than pigs in NT during d 14 to 28. However, G:F was not affected by ambient temperature (0.623 vs. 0.618 g/g; P = 0.702). Dietary Cr had no effect on growth performance. Pigs in HT had less plasma cortisol (42.0 vs. 53.7 ng/mL; P = 0.012) and glucose (6.68 vs. 6.96 ng/mL; P = 0.018). Respiratory rate of pigs in HT was greater compared with the pigs in NT (114.6 vs. 65.0 breaths/min; P < 0.001) on d 27. In Exp. 2 and 3 (pooled), pigs in low ambient temperature (LT) had decreased G:F (0.636 vs. 0.663 g/g; P < 0.01) associated with a tendency toward a greater ADFI (1,026 vs. 942 g; P = 0.079) during d 14 to 26 (28). Ambient temperature or dietary Cr supplementation had no effect on blood measurements. In Exp. 3, the respiratory rate measured on d 22 and 27 was less (43.2 vs. 54.2 breaths/min and 42.2 vs. 57.0 breaths/min, respectively; P < 0.001) in the pigs in LT than the pigs in NT with no effects of dietary Cr supplementation. These results indicate that growth performance is affected by thermal stress and plasma cortisol is decreased by heat stress, but these effects are not moderated by dietary Cr. Key words: chromium, pig, thermal stress