Effects of Reduced Dietary Protein at High Temperature in Summer on Growth Performance and Carcass Quality of Finishing Pigs

SIMPLE SUMMARY: It has been well documented that the energy intake and associated energy retention of pigs will decline as the result of heat stress when the ambient temperature increases beyond thermoneutrality. The development of nutritional interventions to alleviate the negative effects of heat stress could be beneficial to pork producers. Studies have shown that reduced protein diets decrease the energy loss related to the excretion of excess N in urine and the energy loss associated with heat production. In conclusion, we provided a new nutritional strategy of decreasing dietary crude protein percentage from 12% to 10% in finishing pigs in summer, which had no negative effects on growth performance and carcass quality. ABSTRACT: The objective of this experiment was to investigate the effects of reduced dietary protein at natural high temperature in summer on the growth performance and carcass quality of finishing pigs. A total of 72 crossbreed pigs (Duroc × Landrace × Yorkshire) at an average body weight (BW) of 77 ± 5.7 kg were randomly assigned to two treatments, based on BW and sex, in six replicates per treatment, with six pigs per pen, using a randomized complete block design. The dietary crude protein (CP) level of the normal protein diet (NP) and the reduced protein diet (LP) were 12% and 10%, respectively. The growth performance and serum biochemical parameters of the pigs were analyzed for a 28-day experimental period. At the end of the experiment, 12 pigs were harvested to measure carcass characteristics and pork quality. The average highest ambient temperature during the experiment period was about 32.4 °C. There was a trend for the average daily feed intake (ADFI) to be lower in the pigs on the reduced protein diet compared to the control (p < 0.10) in the 0–28 day period. The serum urea nitrogen was lower (p < 0.05) for pigs fed the reduced protein diets only on day 14. The carcass characteristics and pork quality were not affected by dietary treatments. In conclusion, decreasing dietary crude protein percentage from 12% to 10% in finishing pigs in summer may have no negative effects on growth performance and carcass quality.