128
Effect of dietary supplementation of the osmolyte betaine on growing pig performance and metabolic status during thermo-neutral and heat-stressed conditions
The present study was designed to evaluate the effects of dietary supplementation of natural betaine on pig performance and metabolic status during thermo-neutral and heat-stressed conditions. Pigs (n=64; BW 39.0±1.5) were assigned within weight blocks and sex to 1 of 8 treatments and housed in individual pens. Treatments consisted of 2 environmental temperatures (thermo-neutral conditions or heat-stressed) and 4 levels of betaine (0, 0.10, 0.15, and 0.20%). Room temperatures followed a daily pattern with a low of 14 and a high of 21°C for the thermo-neutral environment and a low of 28 and high of 35°C for the heat-stressed environment. Diets were corn-DDGS-soybean meal based (2.96 g SID lysine/Mcal ME) and were fed for 7 d (constant 21°C) prior to imposing temperature treatments. Respiration rate and rectal temperature were measured on d 1, 2, 3, 7, 14, 21 and 28. Data were analyzed as a split plot design with weight block within temperature environment as whole plot and diet as split plot. Repeated measures were analyzed as a split-split plot. Heat stress reduced ADG (0.710 vs. 0.822 kg/d, P=0.005) for the 28-d period. During d 1 to 14, ADFI was decreased in pigs exposed to heat (1.718 vs. 2.250 kg/d, P<0.001). During d 15 to 28, there was a quadratic effect of betaine on ADFI (1.998, 2.035, 2.160 and 1.964 kg/d for 0, 0.10, 0.15, and 0.20% betaine, respectively; P = 0.034), and ADFI was greater under heat-stressed conditions (2.093 vs. 1.985 kg/d, P = 0.044). Gain:feed was greater under heat-stressed conditions during d 1 to 14 (0.433 vs. 0.382, P= 0.018) and lower during d 15 to 28 (0.338 vs. 0.416, P=0.02). Heat stress increased respiration rate and rectal temperature throughout the study (22 vs. 49 breaths/30 s, P≤0.001; and 38.93 vs. 39.51°C, P=0.015). Heat stress increased creatine phosphokinase (CPK), creatinine, hemoglobin, and hematocrit on d 3 and reduced urea N, BUN/creatinine ratio, P, Mg, amylase, monocytes, and eosinophils (P<0.05). On d 28, heat stress increased globulin, CPK, creatine, Mg, amylase, monocytes and eosinophils and reduced albumin/globulin ratio, hemoglobin, and hematocrit (P<0.05). Betaine fed at 0.15% decreased CPK in pigs experiencing heat stress on d 3, but not d 28 (27.8, 12.6, 5.7, 23.6 U/mL; P = 0.04). Heat stress affected growth and blood chemistry, but betaine had minimal impact on alleviating heat stress with the possible exception of early days of heat exposure.
Keywords: pigs, betaine, heat-stress