Effect of different digestible isoleucine/lysine ratios for broiler chickens

Abstract

Two experiments were conducted to evaluate different digestible isoleucine/lysine ratios on diets for broiler chickens in the starter (7 to 21 days) and finishing (30 to 43 days) phases. For the tests, the experimental design was of randomized blocks with seven treatments (six different digestible isoleucine/lysine ratios and a control treatment) and eight repetitions of 25 and 20 birds (COBB males) per experimental unit in the starter and finishing phases, respectively. The diets met the requirements, except for isoleucine and lysine. To avoid excess lysine in the experimental diets, the digestible lysine content was calculated to be 87% and 89% of the recommended for the starter and finishing phases, respectively. The control treatment was adequate in lysine and isoleucine. Feed intake, weight gain, feed conversion and carcass yield in the two phases were evaluated. There was quadratic effect of different ratios on feed intake in the finishing phase and on weight gain and feed conversion rate in both phases. There was quadratic effect on breast meat yield and breast fillets in the starter phase, but there was no significant effect on carcass yield in the finishing phase. The digestible isoleucine/lysine ratio recommended for broilers in the starter phase (7 to 21 days) is 66% and for the finishing phase (30 to 43 days), it is 68%

<b>Digestible isoleucine requirements for 22- and 42-day-old broilers

“…Current analysis shows that the isoleucine requirement for the carcass parameters assessed at 42 days is lower than the requirement for performance. These results agreeing with findings by Corzo et al (2008) who tested 0.58; 0.66 and 0.68% of digestible isoleucine levels in broilers' diets and Tavernari et al (2012) who evaluated different digestible isoleucine/lysine ratios (58.0; 62.0; 66.0; 70.0; 74.0 and 78.0%) on diets for broilers in the finishing (30 to 43 days) phase. Berres et al (2010) likewise evaluated broilers fed on diets with increased Val-and Ile-to-Lys ratios from 14 to 35 days and registered no differences in the treatment for carcass evaluation at 35 days.…”

“…Campos et al (2012) analyzed the effect of isoleucine: lysine ratio on broiler performance and observed that 69% isoleucine: lysine ratio was recommended for maximum performance of broilers from 28 to 40 days old. According to Tavernari et al (2012), the best isoleucine: lysine ratios for feed intake, weight gain and feed conversion were 64, 68 and 72%, respectively.…”

“…According to Tavernari et al (2012), the recommendation for the digestible isoleucine/lysine ratio which meets the main productive parameters for broilers in the phase from 30 to 43 days is 68%. It is actually the same value recommended by Rostagno et al (2005).…”

Impact of second line limiting amino acids’ deficiency in broilers fed low protein diets with rapeseed meal and de-oiled rice bran

“…The deficiency of SLAA resulted in significantly lower absolute intake of valine and isoleucine (in T 2 ) and additionally tryptophan (in T 3 ; Table-6 ) which perhaps impeded protein accretion and hence the growth performance of broilers, since AA have been revealed to influence the myogenic gene expression in broilers [ 16 ]. The growth retardation as a consequence to SLAA deficiency is well noticed in previous studies with deficiencies of valine alone in young broilers [ 17 , 18 ], valine and isoleucine [ 1 , 19 ], isoleucine, tryptophan and arginine [ 20 ], isoleucine alone [ 21 , 22 ] and arginine, valine, isoleucine and tryptophan [ 23 ]. With marginal SLAA deficiency in the finisher phase, birds could compensate to the SLAA intake at this time period (data not shown) and as a consequence, birds could grow on par with control which is suggestive of the compensatory growth during this period due to moderate but not for high SLAA deficiency.…”

Standardized ileal digestible isoleucine requirement for broilers

“…It was observed that for trial 1 (study of Tavernari et al 2012), the estimated SID-ILE requirement for BWG was substantially lower than would be expected from a visual interpretation of the curve. This overestimation of the SID-ILE requirement in trial 1 could be avoided by removing the last observation leaving still some 5 observations on which the curve fitting could be carried out.…”