Threonine-to-lysine ratio in laying hens: physiological parameters and organ weight

ABSTRACT. The objective of this study was to evaluate the effect of threonine:digestible lysine ratio in the diet on the physiological variables and weight of organs of light laying hens. Two hundred and ten 47 week-old Dekalb White laying hens were distributed in a completely randomized design, with five levels of threonine (0.507; 0.552; 0.597; 0.642 and 0.677%) and seven replicates of six birds each. The experimental period was 10 weeks, totaling 62 days and more eight days for the animals to adapt. The physiological parameters of cloacal temperature (CT), respiratory rate (RR) and average surface temperature (AST) were recorded weekly (7:00 am, 10:00 am, 1:00 pm, 4:00 pm, and 7:00 pm); after solid and water fasting, the birds were slaughtered to assess the absolute weight of the organs. The time of day influenced (p