Assessing the performance response of laying hens to intake levels of digestible balanced protein from 27 to 66 wk of age

Laying hens continue to improve in egg production (EP) and feed efficiency (FE), and therefore, it is relevant to re-examine their digestible balanced protein (BP) requirements. From 27 to 66 wk of age, hens (Lohmann-LSL Lite) were fed diets designed to provide 550, 625, 700, 775, or 850 mg hen(-1) d(-1) of amino acid balanced digestible lysine (Dlys). Response criteria included EP, egg weight (EW), feed intake (FI), mortality, egg mass (EM), egg size classifications, FE (kg feed kg(-1) EM), and lysine efficiency (LE; mg Dlys g(-1) EM). The experiment was a completely randomized design, and data were analyzed using regression analysis. Differences were considered significant if P <= 0.05. Hen-day (HD) EP, EW, EM, FI, and LE increased and FE and mortality decreased in a quadratic fashion with increasing Dlys intake, while the proportion of cracked eggs increased linearly. Egg size classifications increased linearly (jumbo, extra-large) and quadratically (large) or decreased in a quadratic manner (medium, small) with increasing Dlys intake. Maximum HDEP, EW, and EM, and minimum FE were achieved at 769, 903, 836, and 839 mg hen(-1) d(-1) intake of Dlys, respectively. In conclusion, the digestible BP requirement of laying hens varies with response criteria.