PSXIII-1 Effects of supplementation of probiotic Lacticaseibacillus rhamnosus on growth performance, rectal temperature, respiratory rate, and blood parameters of heat-stressed growing pigs.

Abstract This study was conducted to investigate the effects of probiotic Lacticaseibacillus rhamnosus on growth performance, rectal temperature, respiratory rate, and blood parameters of heat-stressed growing pigs. Twenty-four growing pigs [(Landrace × Yorkshire) × Duroc; initial average body weight (BW) = 25.46 ± 0.94 kg] were individually housed, blocked by initial BW, and randomly assigned to 2×2 factorial design of environmental treatment [thermoneutral conditions (TN; temperature, 23–24℃; humidity, 35%) or heat stress conditions (HS; temperature, temperature, 32–33℃; humidity, 80%)] and dietary treatment [basal diet based on corn and soybean meal (CON) or CON + 0.02% dietary probiotic Lacticaseibacillus rhamnosus (PRO)] for 14 days. Growth performance was measured weekly and rectal temperature and respiratory rate were recorded daily. Blood samples were collected from each pig on day 7 and 14 to determine blood count, immune responses, and biochemical analysis. Data were analyzed using the PROC MIXED of SAS. The experimental unit was a pig. The model included environmental treatment (TN or HS), dietary treatment (CON or HS), and the interactive effects as fixed effects and block as a random effect. Pigs under HS conditions had decreased (P < 0.05) average daily gain and average daily feed intake during the entire experimental period compared with those under TN conditions. There were no probiotic or interaction effects on growth performance. Pigs under HS conditions had increased (P < 0.05) rectal temperature and respiratory rate during the entire experimental period compared with those under TN conditions. Pigs fed PRO had decreased (P < 0.05) rectal temperature on day 11 and 12 compared with those fed CON. Pigs under HS conditions tended to have higher (P < 0.10) number of red blood cells and hematocrit level on day 7 than those under TN conditions, but tended to have lower (P < 0.10) number of white blood cells on day 14. Pigs under HS conditions had higher (P < 0.05) serum tumor necrosis factor-α on day 14 than those under TN conditions, but serum interleukin-6 on day 14 was lower (P < 0.05). There were no probiotic or interaction effects on whole blood count and serum immune responses. Pigs under HS conditions had higher (P < 0.05) levels of serum albumin and creatinine on day 7 than those under TN conditions. Pigs under HS conditions had lower (P < 0.05) serum calcium level on day 14 than those under TN conditions, but serum creatinine on day 14 was higher (P < 0.05). There was an interaction (P < 0.10) on levels of serum total cholesterol and glucose on day 14. In conclusion, this study suggests that heat stress conditions had a negative impact on growth performance and altered blood parameters of growing pigs.