Hypothesis
Adding leucine-isoleucine-valine blends to normal- or low-protein starter diets would improve broiler growth and breast yield under hot summer conditions.
What failed
In a 2×3 factorial trial with 768 Ross 308 chicks at about 33 °C, body weight, feed conversion and carcass weight were unaffected by protein level, BCAA blend or their interaction. One blend (4L:1I:1V) actually reduced breast yield versus no supplement.
Broken assumption
Supplementing branched-chain amino acids helps heat-stressed broiler chicks grow faster or yield more breast meat.
Why
The abstract gives no mechanism; it concludes the blends failed to improve performance because birds on all diets reached similar weight and feed conversion.
From the published paper: Bozbay et al. Animal Bioscience, 2020. ↗CC BY