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Effects of dietary chromium propionate during heat stress on finishing pigs
Study objectives were to determine the effects of chromium (Cr) propionate (Kemin Industries, Des Moines, IA) on growth performance and biomarkers of metabolism and health in heat stress (HS) and nutrient-restricted pigs. Crossbred barrows (n=96; 122 ± 1 kg BW) were enlisted in a 2x3 factorial experiment with two replicates, blocked by initial BW and randomly assigned to one of six dietary-environmental treatments: 1) thermoneutral (TN) conditions and fed ad-libitum a control diet (TNCtl), 2) TN conditions and fed ad-libitum a Cr diet (TNCr), 3) TN and pair-fed a control diet (PFCtl), 4) TN and pair-fed a Cr diet (PFCr), 5) HS and ad-libitum fed a control diet (HSCtl), and 6) HS and ad-libitum fed Cr a diet (HSCr). Pair-fed animals were fed to match intake of their HS counterparts in order to eliminate the confounding effect of dissimilar feed intake. The Cr diet contained 0.5g/kg of feed to deliver 200 ppb Cr/d. The study consisted of three experimental periods (P). During P0 (5 d), all pigs were exposed to TN conditions (21.3 ± 0.1 ºC, 56.8 ± 0.3% RH) and fed the control diet ad libitum. During P1 (5 d), pigs were fed their respective dietary treatments ad-libitum and kept in TN conditions. During P3 (35 d), HSCtl and HSCr pigs were fed ad-libitum and exposed to progressive cyclical HS conditions (27 to 31ºC, 50 ± 0.3% RH) while TNCtl, TNCr, PFCtl and PFCr pigs remained in TN conditions and were fed ad-libitum or pair-fed to their HSCtl and HSCr counterparts. Overall, pigs exposed to HS had increased (P< 0.01) rectal temperature, skin temperature and respiration rate (0.40ºC, 3.8ºC, 32 bpm, respectively). HS decreased (P < 0.01) ADFI (20%), and ADG (21%) compared to TN controls. Final BW was increased in HSCr (2.00 kg, P=0.03) compared to HSCtl pigs, and ADFI tended to be increased in HSCr during P2 relative to HSCtl treatment (0.78 vs. 0.72 kg/d; P=0.08). During TN conditions there were no effects of Cr on most production parameters, but ADFI tended to be increased in Cr relative to Ctl-fed pigs (3.29 vs. 3.09 kg/d; P=0.08). No effects of Cr supplementation were detected on circulating blood glucose, insulin, NEFA, cholesterol, triglycerides and LPS binding protein. However, blood neutrophils were increased in HSCr (38%; P=0.02) relative to HSCtl pigs. In summary, these findings suggest chromium supplementation may be beneficial to growth performance and health during HS.
Keywords:
Growth performance, biomarkers of metabolism, pair-fed animals