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In swine production, dietary protein is the most important nutrient because it provides essential amino acids and affects the total cost of production. When dietary protein exceeds the requirements of pigs, the surplus is excreted either in urine or in feces, affecting production economy and the environment. This study aimed to evaluate the effect of a low-protein diet on growth performance, carcass traits, nutrient digestibility, blood profiles, and odor emissions in growing-finishing pigs.
Methods: A total of 126 crossbred pigs ([Yorkshire×Landrace]×Duroc) with an average body weight of 38.56±0.53 kg were used for a 14-week feeding trial. Experimental pigs were allotted to one of 6 treatments in 3 replicates of 7 pigs per pen in a randomized complete block design. Pigs were fed each treatment diet with different levels of crude protein (CP). Phase 1 (early growing): 14%, 15%, 16%, 17%, 18%, 19%; phase 2 (late growing): 13%, 14%, 15%, 16%, 17%, 18%; phase 3 (early finishing): 12%, 13%, 14%, 15%, 16%, 17%; phase 4 (late finishing): 11%, 12%, 13%, 14%, 15%, 16%. All experimental diets in each phase were contained the same concentration of lysine, methionine, threonine, and tryptophan.
Results: Over the entire experimental period, there was no significant difference in body weight, average daily feed intake, and gain-to-feed ratio among all treatments, but a quadratic effect was observed in average daily gain during the late finishing phase with higher average daily gain in Group D. Blood urea nitrogen concentration linearly increased with an increase in dietary CP levels. Regarding nutrient digestibility, excreted nitrogen in urine and feces and nitrogen retention linearly increased as the CP level increased. A linear effect was observed with increasing CP levels in amines, ammonia, and hydrogen sulfide in odor emissions. No significant effects were observed in the measurements of carcass traits and meat characteristics.
Conclusion: In conclusion, reducing dietary CP levels had no detrimental effect on the parameters of growth performance, carcass traits, and nutrient digestibility, but BUN and excreted N linearly increased with increasing dietary CP levels. According to present results, the CP level to 14% in early-growing pigs, 13% in late-growing pigs, 12% in early-finishing pigs, and 11% in late-finishing pigs is recommended.
Niyonsaba A, Jin XH, Kim YY. Effect of reducing dietary crude protein level on growth performance, blood profiles, nutrient digestibility, carcass traits, and odor emissions in growing-finishing pigs. Animal Bioscience. 2023; 36(10): 1584. https://doi.org/10.5713/ab.23.0155