David Baker Symposium
DAVID BAKER SYMPOSIUM
Excess of a branched-chain amino acid (BCAA), particularly Leu, may result in increased degradation of the others due to common catabolic steps. Moreover, large neutral amino acids (LNAA) and BCAA have common brain transporters. Therefore, excessive BCAA may decrease the absorption of AA that serve as precursors of neurotransmitters. We hypothesize that practical diets with high levels of feed-grade AA can potentially create BCAA imbalances and impact performance. A meta-regression was conducted to evaluate the effects of BCAA and their interactions with LNAA to develop prediction equations for ADG, ADFI, and G:F. Data from 25 papers for a total of 44 trials were recorded in a database. Diets were reformulated using NRC (2012) nutrient values. Amino acids were expressed on standardized ileal digestible basis. A step-wise manual forward selection was used to evaluate predictor variables. Predictors had to be significant (P < 0.05) as a single variable predictor and provide a BIC improvement of at least 2 points to be included in the model. Observations were weighted using the inverse of the squared SEM. The resulting predictor equations were: ADG, g = – 985.94 + (15.2499 × average BW (kg)) – (0.08885 × average BW × average BW) + (1.063 × Leu:Lys) + (20.2659 × Ile:Lys) – (0.1479 × Ile:Lys × Ile:Lys) + (9.2243 × (Ile+Val):Leu) – (0.03321 × (Ile+Val):Leu × (Ile+Val):Leu) – (0.4413 × Ile:Trp); G:F = 648.3 – (6.2974 × average BW (kg)) + (0.02051 × average BW × average BW) + (0.5396 × Ile:Lys) + (1.7284 × Val:Lys) – (0.00795 × Val:Lys × Val:Lys) – (1.7594 × Met:Lys); and ADFI, kg = predicted ADG/predicted G:F. The equations suggest that increasing Leu:Lys negatively affects ADG due to a reduction in ADFI and G:F. The addition of Val, Ile, and Trp, alone or in combination, has the potential to counteract the negative effects of high Leu on growth performance.