Determination of digestible isoleucine: lysine ratio in diets for laying hens aged 42-58 weeks

Abstract

Two hundred and fifty-two Hy-Line W36 laying hens were allotted in a completely randomized design with 6 treatments, 7 replicates and 6 hens per experimental unit in order to determine the ideal ratio of isoleucine (Ile) in relation to lysine (Lys) to laying hens aged 42-58 weeks. Experimental diets contained digestible Ile at different levels, resulting in different Ile:Lys ratios (0.73:1; 0.78:1; 0.83:1; 0.88:1; 0.93:1 and 0.98:1). A basal diet was formulated to provide Isoleucine in levels below recommendations. This diet was supplemented with L-isoleucine to make up the 6 diets. Each diet was made isonitrogenous by varying the dietary contents of glutamic acid and isocaloric by adjusting the contents of cornstarch. All essential amino acids were provided proportionally to lysine. Egg production, egg weight, egg mass, feed conversion ratio, albumen, yolk and eggshell contents were recorded and compiled at every 28-day period. No differences were observed in the performance over a wide range of dietary isoleucine concentrations from 5.76 to 7.73 g/kg corresponding to 0.73:1 to 0.98:1 Ile:Lys ratios. The lowest Ile:Lys ratio (0.73:1) was sufficient to ensure satisfactory performance of birds, corresponding to the consumption of 534 mg of isoleucine and 731 mg of lysine/day

Tryptophan, threonine and isoleucine supplementation in low-protein diets for commercial laying hens

“…This is because these AA share the same transportation systems through the cell membrane and are degraded by the same enzyme -dehydrogenase of branchedchain α-keto acids (HARRIS et al, 2001). Harms and Ivey (1993), and more recently Mello et al (2012), did not find any improvement in the productive parameters for laying hens supplemented with Ile. The imbalance among branched-chain AA may have been the reason those authors did not find positive responses on bird performance.…”

“…Therefore, Ile industrial supplementation is essential in these diets (MELLO et al, 2012). However, this supplementation must be performed with caution, as there is a narrow margin between the requirements and excess amounts of this AA for laying hens (PEGANOVA; EDER, 2002).…”

Egg production and quality responses to increasing isoleucine supplementation in Shaver white hens fed a low crude protein corn-soybean meal diet fortified with synthetic amino acids between 20 and 46 weeks of age

“…(2013) found the optimal SID Ile:Lys ratio for laying hens aged 24 to 40 wk was between 82 and 84%. The same laboratory conducted a similar study in older hens aged 42 to 58 wk and concluded that the lowest ratio tested of 73% was sufficient for satisfactory performance, though performance was numerically improved as Ile level increased ( Mello et al., 2012 ). The diets in the later study were not analyzed for CP content or AA profile; therefore, it is possible that Ile was not limiting.…”

Digestible threonine-to-lysine ideal ratio for laying hens fed with low-protein diets from 24 to 40 weeks of age

“…Methionine + cysteine, tryptophan, isoleucine and valine-to lysine ratios were met in 103% of those recommended by BRUMANO et al (2010), CALDERANO et al (2012), MELLO et al (2012) and ALMEIDA (2014) respectively. Ratios of the other essential amino acids with lysine in digestible basis were supplied, at least, 3% above the recommended by ROSTAGNO et al (2011).…”