Valine needs in starting and growing Cobb (500) broilers

Abstract

Two independent experiments were conducted with male Cobb × Cobb 500 broilers to determine the optimal valine-to-digestible-lysine ratio for broiler development. We conducted a randomized block experiment with 7 treatments, each with 8 replicates of 25 starter birds (8 to 21 d of age) and 20 finisher (30 to 43 d of age) birds. To prevent any excess of digestible lysine, 93% of the recommended level of digestible lysine was used to evaluate the valine-to-lysine ratio. The utilized levels of dietary digestible lysine were 10.7 and 9.40 g/kg for the starting and growing phases, respectively. A control diet with 100% of the recommended level of lysine and an adequate valine-to-lysine ratio was also used. The feed intake, weight gain, feed conversion ratio, and carcass parameters were evaluated. The treatments had no significant effect on the feed intakes or carcass parameters in the starter and finisher phases. However, during both of the studied phases, we observed a quadratic effect on weight gain and the feed conversion ratio. The broilers of both phases that were fed test diets with the lower valine-to-lysine (Val/Lys) ratio had poorer performance compared with those broilers fed control diets. However, when higher Val/Lys ratios were used for the starting and growing broilers that were fed test diets, the 2 groups had similar performance. During the starting phase, in broilers that were fed a higher Val/Lys ratio, weight gain, and the feed conversion ratio improved by 5.5% compared with broilers fed the basal diets. The broilers in the growing phase also had improved performance (by 7 to 8%) when the test diets had higher Val/Lys ratios. Based on the analysis of the starter phase data, we concluded that the optimal digestible Val/Lys ratio for Cobb × Cobb 500 broilers is 77%, whereas for birds in the finisher phase (30 to 43 d of age), a digestible Val/Lys ratio of 76% is suggested.

<b>Digestible lysine for broilers from different commercial strains in the final phase

“…Accordingly, when evaluating lysine levels for broilers at different stages of creation, it is essential to consider its relationship with other essential amino acids. Among these, it is possible to highlight the methionine, threonine and valine, which are respectively the first, the third and the fourth limiting amino acid for broilers in diets formulated on vegetable ingredients (Corzo, Loar, & Kidd, 2009;Tavernari et al, 2013). In addition, when there is a non-balance of essential amino acids provided in the feed, even the non-essential amino acids may become limiting to the maximum expression of the birds genetic potential (Oliveira Neto & Oliveira, 2009).…”

Digestible Valine Requirements in Low-Protein Diets for Broilers Chicks

“…Valine is a branchedchain amino acid that is mainly metabolized in the skeletal muscle, and it is responsible for body protein balance (Rogero & Tirapegui, 2008). Considering previous findings (Berres et al, 2011;Tavernari et al, 2013), it may be concluded that valine requirements for protein accretion are lower than those required for feed conversion in broilers. Therefore, the TID Val levels estimated for feed conversion ratio are recommended to be applied in broiler feed formulation, as they are (Table 4).…”

“…However, there was a quadratic effect (p≤0.05) of TID Val levels on breast yield, with the highest value estimated at 0.826% of TID Val ( Figure 5). Tavernari et al (2013) estimated 0.730% TID Val for 30-to 43-old broilers fed diets containing animal by products in order to obtain maximum breast yield. The higher estimated level of TID Val the present (0.826%) compared with that of Tavernari et al (2013) may be ascribed to the dietary inclusion of only plant-derived products, which may increase valine requirements in reduced-protein diets (Berres et al, 2010).…”

“…High dietary leucine level increases the requirements of valine and isoleucine (D'Mello & Lewis, 1970), and therefore, the lower TID Leu level did not require valine supplementation. The TID Val levels estimated for the grower phase (21 to 42 days) was 0.853% for feed conversion ratio in the 16.5% crude protein diet, differently that recommended by Tavernari et al (2013), who estimated 0.790% TID Valin diets with 18.2% CP for 30-to 42-d-old broilers. Despite the small difference in crude protein levels (16.5 and 18.2%), the difference in the requirement estimates is probably due to the inclusion of animal byproducts in the study of Tavernari et al (2013), which reduces valine requirement.…”

“…Corn and soybean meal proteins contain more leucine than valine and isoleucine, which may increase the requirement of the last two amino acids in broiler diets, particularly during the grower phase (Berres et al, 2010) and when reduced-protein diets are fed to broilers. Valine is more susceptible than isoleucine to the increase in dietary leucine levels (D'Mello, 2003), and it is considered the fourth limiting amino acid in broilers diets based on corn and soybean meal with no inclusion of animal feedstuffs (Thornton et al, 2006;Tavernari et al, 2013). Valine requirements increase with broiler age, when dietary crude protein content is reduced (Corzo et al, 2007;Corzo et al, 2010;Duarte et al, 2014).…”