Exogenous protease supplementation may help to improve amino acid (AA) utilization in low crude protein (CP) diets. This study was conducted to determine the effects of reducing CP/AA in diets with or without a commercially available protease on performance and egg quality of laying hens in peak production. A 20-week study was conducted using 30 wk old 768 Hy-Line W-36 laying hens that were equally and randomly placed into one of 96 experimental units (raised-wire cages). There were 12 replications per treatment and the stocking density was 7.62 hens/m2. Each replicate pen (8 hens) was fed one of 8 diets from the 4 AA level (100, 95, 90 and 85% of breeder recommendation) x 2 protease inclusion (0 or 0.012%). The adequate (100%) diet was based on corn and soybean meal and formulated on the basis of dig. Lys: dig. AAs (Met, Thr, Trp, TSAA, Ile and Val) to meet 100% of Hy-Line W-36 breed recommendation. Variations in CP/AA (95, 90, and 85% diets) were accomplished by reducing the 100% diet by 5, 10 and 15%, respectively. Data were subjected to statistical analyzes of variance (PROC GLM procedure, SAS 9.4). There was an AA levels x protease interaction for hen day egg pro- duction (HDEP; P=0.0120). Inclusion of protease in 100, 95, and 90% diets improved HDEP, whereas HDEP decreased at 85% AA + protease. Hens fed the 95% diet had the highest HDEP and those fed 85% diet without protease had the lowest HDEP. The average feed conversion ratio (FCR; kg feed/dozen eggs) was lower in 85% diets (1.57) compared to others (P=0.0019). Egg weight (EW) was significantly lower in hens that were fed the 85% AA diets (P<0.0001). Percent of defective eggs were significantly lower in hens fed 90% AA diet (P=0.0244) compared to all other AA levels. Throughout the experiment, there were no significant differences between any treatments for feed intake, Haugh unit, albumen weight, albumen %, yolk weight and yolk %.
These data demonstrate that AA level impacts EW and % of unsaleable eggs, while inclusion of the tested protease does not. More research should be done to determine the practical application and economics of this protease inclusion. Future research can include investigating AA digestibility and feeding protease for a longer experimental period.