We studied the relationship between the intake of branched chain AA and the production of lactating dairy cows. A meta-analysis of 274 studies and 1036 treatment means from published dairy cow experiments was conducted using a Bayesian hierarchical modeling approach. Response variables were: milk yield (MY; kg/d), energy-corrected milk (ECM; kg/d), milk protein yield (kg/d) and milk fat yield (kg/d). Three levels of models were developed. Level 1 included the diet variables dry matter intake (DMI; kg/d), rumen degradable protein (RDP; % DM), rumen undegradable protein (RUP; % DM), starch (% DM), neutral detergent fiber (NDF; % DM), fatty acids (FA; % DM), and ratio of acid detergent fiber and NDF (ADF/NDF). Level 2 variables included variables in level 1 + Leu (% DM), Ile (%DM), and Val (% DM). Level 3 included level 1 and 2 variables + rumen NH3-N (mg/dl), rumen pH (pH), rumen isovalerate (Ival, % of VFA), and rumen isobutyrate (Ibut, % of VFA). Initially, we used an all possible models selection approach using linear mixed effects models with the random effect of study. The model with the lowest Akaike Information Criterion was then fitted as a Bayesian hierarchical model with minimally informative priors. Models were evaluated using 5-fold cross validation and variance inflation factors. In general, level 2 models always improved compared with level 1 models. For instance, the MY model (CCC = 0.61), predicts MY = 1.78 + 0.891(DMI) + 0.857(RUP) – 0.0415(RUP²) – 0.0744(NDF) + 0.449(FA) + 16.4(Ile) – 12.3(Ile²) + 2.73(Val). MY had a positive response to Ival and Ibut in the level 3. Likewise, the model for ECM (CCC = 0.68), predicted responses as ECM = – 4.26 + 1.02(DMI) + 1.16(RUP) – 0.0606(RUP²) + 4.67(ADF/NDF) + 15.4(Ile) – 8.51(Ile²). Due to high correlation between RDP and RUP they were interchangeable in model selection without much change the response of BCAA. For MY and ECM RUP yielded a better model. Overall, utilizing the diet branched chain AA as predictors improved models over other diet variables. Ile was present in all the models with a positive coefficient at a decreasing rate, suggesting an important role of Ile for dairy production.