Total tract digestibility of nitrogen in pigs exposed to high environmental temperatures

The effect of environmental heat stress on N metabolism was studied using 7 gilts (50.5 ± 1.7 kg initial BW). Pigs were housed in metabolism cages in a climate-controlled room. After a 4-d adaptation, two 14-d experimental periods followed during which the animals were exposed to thermo-neutral temperature (NT; 20.61 ± 0.1°C) or high environmental temperature (HT; 30.41 ± 0.4°C). In each experimental period, two 24-h balance periods were carried out to collect feces and urine (via bladder catheters) for N analysis. Based on N intake and N excretion, N balance was calculated. At HT conditions, N intake was lower (P = 0.028), urinary N excretion increased (P = 0.040), and N retention decreased (P = 0.001) in comparison with NT conditions. Exposure of pigs to HT tended to reduce (P = 0.070) digestibility of N as compared to NT conditions. When pigs are exposed long term to continuous HT, N retention decreases presumably due to decreased use of ME during respiration.