Effects of protease enzyme supplementation and varying levels of amino acid inclusion on productive performance, egg quality, amino acid digestibility, and economics of egg production in Hy-Line W-36 laying hen from 50 to 70 wk of age

This study evaluated the effects of reducing total amino acid (AA) & crude protein (CP) level and supplementation of protease on egg production, egg quality, AA digestibility and economics of egg production in W-36 laying hens from 50-70 wk of age. Five hundred seventy-six Hy-Line W-36 hens were housed in 192 cages consisting of 12 reps of 2 side-by side cages containing 3 hens. Each replicate was fed one of 8 diets in a 4 × 2 factorial arrangement of AA&CP levels (85, 90, 95, and 100% of the breeder recommendations) and protease (exclusion or inclusion). Protease was incorporated into the feed at the dosage recommended by the manufacturer, which is 60 grams per metric ton. Corn and soybean meal-based diets were formulated to meet 100% of the breeder's recommendations for the standardized ileal digestibility of Lys, Met, Thr, Trp, TSAA, Ile, and Val. Our study explored the effects of varying levels of AA&CP set at 85, 90, 95, and 100% of the recommendations for the ileal digestibility of Lys, Thr, Trp, TSAA, Ile, and Val, in diets with and without protease supplementation. All diets were supplemented with phytase at 500 phytase units/kg. Data were analyzed using PROC GLM of SAS 9.4 (2019) and the means were separated using Tukey's multiple comparison tests (P < 0.05). Overall, an interaction was observed between AA&CP level and protease supplementation on egg weight (EW; P = 0.003). The main effect of AA&CP level was observed on haugh unit (HU; P < 0.001) and feed cost (P < 0.001) where higher values were observed in 100 and 95% CP level diets as compared to 90 and 85% CP level diets. Similarly, a decrease in the AA&CP level increased the apparent ileal digestibility (AID) of CP (P < 0.001), Lys (P < 0.001), Met (P < 0.001), Thr (P < 0.001), Trp (P < 0.001), Ile (P < 0.001), and Val (P < 0.001). Protease supplementation increased the AID of CP (P = 0.003), Lys (P = 0.001), Thr (P = 0.009), Ile (P < 0.001), and Val (P < 0.001). In conclusion, lower levels of AA&CP supplemented with protease did not negatively affect the egg production, albumen quality and the cost of production in low AA&CP corn and soybean meal-based diets in the Hy-Line W-36 laying hen.