PSI-29 Enhancing growth performance and reducing environmental impact with dietary protease supplementation in growing pigs fed high- and low-density diets

Exogenous protease has emerged as a promising solution for enhancing protein digestion and utilization in animal diets, offering potential benefits for both animal performance and environmental impact mitigation in pig farming. In a 6-wk trial involving 140 growing pigs [initial body weight (BW) = 24.10 ± 1.66 kg], the effects of dietary protease supplementation on growth performance, nutrient digestibility, and noxious gas emission were investigated. Pigs were randomly assigned to one of four dietary treatments in a 2 x 2 factorial design with two levels of nutrient density and 0 or 125 g/ton supplementation of protease. The pigs were blocked by BW and housed in 28 pens with each pen consisting of 5 pigs (3 barrows and 2 gilts). The experimental design employed a randomized complete block design with 7 replicate pens per treatment. The data were analyzed using two-way ANOVA, with differences between means assessed using Tukey’s test (P < 0.05). Results revealed no significant interaction (P > 0.05) between nutrient density and protease supplementation concerning growth performance, nutrient digestibility, and noxious gas emission. Pigs subjected to high-density diets exhibited greater (P < 0.05) average daily gain (ADG) and gain-to-feed ratio (G:F) compared with those on low-density diets. While protease supplementation did not impact ADG and average daily feed intake (ADFI), there was a tendency towards reduced (P = 0.08) G:F throughout the 6-wk period. Pigs fed high-density diets demonstrated significantly greater (P < 0.05) apparent total tract digestibility (ATTD) of gross energy (GE) compared with their counterparts on low-density diets. Furthermore, the inclusion of protease significantly increased (P < 0.05) ATTD of GE. However, no discernible differences were noted among diets regarding the ATTD of dry matter and nitrogen. Regarding noxious gas emission, protease supplementation did not significantly affect total mercaptans and hydrogen sulfide (H2S) emission. Nonetheless, there was a notable trend towards reduced (P = 0.06) ammonia gas (NH3) emission with protease inclusion. Similarly, nutrient density did not exhibit a significant effect (P > 0.05) on noxious gas emission. In conclusion, the results of the study underscore the importance of nutrient density and protease supplementation in optimizing pig performance and environmental sustainability in swine production systems. Further research is warranted to elucidate the underlying mechanisms a