Abstract
Two-hundred sixteen white laying hens were used to assess the ideal ratio of digestible threonine:lysine in diets for laying hens at 24 to 40 weeks of age. Birds were assigned to a randomized block design, with six treatments, six replicates per treatment and six birds per experimental unit. The cage was used as the blocking criterion. Experimental diets contained different digestible threonine:digestible lysine ratios (65, 70, 75, 80, 85 and 90%) with 142 g/kg of crude protein. Experimental diets were formulated to be isonitrogenous and isocaloric with different contents of L-glutamic acid. Feed intake (g/hen/d), egg production (%), egg weight (g), egg mass (g/hen/d), feed conversion ratio (kg/dozen and kg/kg egg), eggshell weight (g), albumen weight (g), yolk weight (g) and body weight gain (g) were assessed. The maximum egg production was observed at 78% digestible threonine:digestible lysine ratio, while the best values of feed conversion ratio (kg/dozen egg) and feed conversion ratio (kg/kg of egg) were observed at 77.6% and 75%, respectively. Feed intake, egg mass and egg contents (yolk, albumen and eggshell) were not affected by treatments. The estimated digestible threonine:digestible lysine ratio of Hy-Line W36 laying hens at 24 to 40 weeks of age is 78%, corresponding to 5.70 g/kg of dietary digestible threonine.
Highlights
The Brazilian egg production has increased in the past few years
Formulation of diets based on the concept of ideal protein is very important, as the nitrogen excretion is reduced when laying hens are fed a profile of amino acids closer to their nutritional requirements
Digestible threonine:digestible lysine ratios had no effect on feed intake by laying hens (Table 2)
Summary
The Brazilian egg production has increased in the past few years. According to UBABEF (2013), the Brazilian egg production in 2012 was approximately 31 billion units and per capita consumption of 161.53 units/year.The increase in egg production has been possible due the studies of the daily requirement of indispensable amino acids for laying hens. This study was conducted to determine the ideal ratio of digestible threonine to lysine in diets for Hy-Line W36 laying hens at 24 to 40 weeks of age. Before the experimental diets were provided, laying hens were individually weighed and randomly allotted to pens so that all pens had approximately the same average body weight (1,328 g) and egg production.
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