Determination of digestible valine requirements in male and female Cobb 500 broilers

Valine and isoleucine deficiency in necrotic enteritis challenge impact growth performance, intestinal health, and muscle growth in broilers

Necrotic enteritis (NE), an enteric disease caused by Clostridium perfringens, and antagonistic effects due to dietary branched-chain amino acid (BCAA) imbalance are key factors that negatively affect chicken growth. The current study was conducted to investigate the effects of valine and isoleucine deficiency in NE challenged broilers. A total of 336 seven-d-old male Cobb 500 were allotted to four treatments with six replicates. The four treatments were as follows: (1) non-challenged control (NC; leucine:lysine = 1.31, valine:lysine = 0.73, and isoleucine:lysine = 0.63), (2) NE-challenged group (NE), (3) NE-challenged with 85 % valine deficiency group (NE-VAL; valine:lysine = 0.62), and (4) NE-challenged with 85 % isoleucine deficiency group (NE-ILE; isoleucine:lysine = 0.54). E. maxima and C. perfringens were administered on d 14 and 18, respectively, and the experiment lasted until d 21. The NE-VAL group had the lowest growth performance measurements compared to the other groups (P < 0.001). All NE-challenged groups had significantly reduced overall growth performance measurements compared to the NC group (P < 0.001). The NE-ILE group showed no difference in any of the measurements compared to the NE group. On d 21, the NE group had significantly increased intestinal permeability, jejunal lesion scores, C. perfringens colony counts, and jejunal chemokine and cytokine gene expression levels, along with decreased intestinal morphology compared to the NC group (P < 0.05). The NE-VAL group had significantly decreased breast muscle yield, reduced lean and total tissue weight, and increased expression levels of mechanistic target of rapamycin pathway and BCAA catabolism-related genes compared to the NE group (P < 0.05). This may explain why the NE-VAL group had the lowest growth performance, as the two negative effects of NE infection and valine deficiency are separated. In conclusion, the negative effects of NE challenge and valine deficiency were independent; valine deficiency showed a similar response to that exhibited by high leucine levels, despite reduced feed intake caused by NE challenge.

Valine deficiency has a greater impact on broiler growth and bone health than isoleucine deficiency

Valine and isoleucine are not only two of the indispensable amino acids (AAs) in chickens but also have special mechanisms with leucine within the branched-chain AA (BCAA) category. Therefore, we aimed to investigate how valine or isoleucine deficiency could specifically affect growth performance in broilers through various analyses. A total of 252 seven-day (d)-old male Cobb 500 broilers were allotted to three treatments with six replicates and reared until d 21. The three treatments were as follows: (1) Control group (CON; 1.31 leucine:lysine ratio), (2) valine deficiency group (-VAL; 0.62 valine:lysine ratio and 85% valine level compared to the CON group), and (3) isoleucine deficiency group (-ILE; 0.54 isoleucine:lysine ratio and 85% isoleucine level compared to the CON group). The -VAL group had significantly decreased d 7, 14, and 21 body weight (BW), BW gain (BWG), feed intake (FI), and feed efficiency from d 7 to 21 compared to the CON and -ILE groups (P < 0.001). The -ILE group showed no difference in d 14 and 18 BW; however, they showed significantly reduced BW and BWG at d 21 and feed efficiency from d 7 to 21 compared to the CON group (P < 0.001). Daily FI in the -VAL group significantly decreased from the beginning compared to the two groups, and this gap further expanded until d 21. The -VAL group also had significantly decreased breast muscle weight, total tissue weight, bone mineral density, bone mineral content, and walking ability (P < 0.01). The expression levels of mechanistic target of rapamycin and BCAA catabolism-related genes were highest in the -VAL group (P < 0.05), whereas the -ILE group did not show any difference compared to the CON group (P > 0.05). In conclusion, about 85% valine deficiency is accompanied by a substantial reduction in chicken growth, which has a much greater effect than isoleucine. Valine deficiency can also lead to increased utilization of leucine, which may result in BCAA antagonism.

Dietary branched-chain amino acid assessment in broilers from 22 to 35 days of age

Background

Valine and isoleucine are similar in chemical structure and their limitation in broiler chicken diets. To evaluate their limitation and interactive effects, multivariate assessment nutrition studies for the branched-chain amino acids (BCAA) are needed. A three level (− 1, 0, + 1), three-factor Box-Behnken design study was conducted to assess dietary BCAA ratios to lysine of 65, 75, and 85 for valine, 58, 66, and 74 for isoleucine, and 110, 130, and 150 for leucine in male and female Lohman Indian River broilers from 22 to 35 d of age.

Results

Live performance of male broilers was not affected by BCAA level. However, male broilers fed increasing isoleucine had improved (P = 0.07) carcass yield as leucine and valine were reduced. Female broilers had improved body weight gain (P = 0.05) and feed conversion (P = 0.003) when leucine and isoleucine were at their lowest levels, independent of valine, but increasing leucine impaired live performance and warranted concomitant increases in isoleucine to restore responses. Increasing dietary isoleucine and valine in female broilers increased breast meat yield (P = 0.05), but increasing leucine tended to diminish the response.

Conclusion

The female Lohman Indian River broiler is more sensitive to BCAA diet manipulation than males. Specifically, as dietary leucine is increased in female broilers, dietary isoleucine increases were needed to offset the negative effects. Both increases in dietary valine and isoleucine improved breast meat yield in female broilers, but only when birds were fed the lowest dietary leucine.