Environmental effects on growing swine performance and immune status with comparisons between predicted and actual growth

The effects of environmental conditions on performance of growing pigs (30–50 kg) were studied over a four week period. Pigs were exposed to naturally occurring diurnal temperatures and a constant 32°C ambient temperature during normally hot weather conditions and constant 21 and 10°C ambient temperature conditions during cold weather. For each temperature treatment, pigs were divided into single, 9 and 18 head per pen groups. The constant 32°C ambient temperature had a significant (p \u3c 0.05) effect on average daily gain and feed intake. The 10°C cold weather treatment had no significant (p \u3e 0.05) effects on overall pig performance. The 9 and 18 pigs per pen group size had no significant effect on pig performance in any of the temperature treatments. Pig and floor surface temperatures were significantly affected by temperature and group size. Pig performance simulations generated from three growth models (NCPIG, SwineGro™ and NRC) were compared to actual pig performance data. Inputs that each model would accept for each environmental treatment in the evaluations were used. There were variations in the predicted average daily gain and feed intake between each of the models and actual data. Prediction variation increased when environmental conditions were out of the pig\u27s thermoneutral zone. The effects of environmental conditions and group size on the immune system of growing pigs (30–50 kg) were studied using T and B cell proliferation counts. Concancavalin A (ConA), Phytohemagglutinin (PHA) and Staphylococcal enterotoxin B (SEB) mitogens were used to determine T cell activation over time. Pokeweed (PWM), Lipopolysaccharide (LPS) and Salmonella typhimurium mitogen (STM) mitogens were used to determine B cell proliferation over time. ConA tests revealed significant (p \u3c 0.01) increases in T cell proliferation over time for both temperature treatments during hot weather. Significant (p \u3c 0.01) reductions in B cell activation were noted for all pigs in the cold weather trials. T and B cell proliferation comparisons for group size at all temperature treatments were non-significant