Prediction of milk essential fatty acid concentrations in dairy goats: A meta-analysis approach based on individual data

This study aimed to predict milk essential fatty acid (EFA) [alpha-linolenic acid (ALA) and linoleic acid (LA)] concentration from their intake through a meta-analysis approach using data from individual goats. The database consisted of 718 measurements obtained from 13 trials in experimental farms. We predicted milk concentrations of ALA and LA from dietary concentrations of these fatty acids (FA) and other dietary- or animal-related variables. The model to predict milk ALA (% of milk FA; R 2 = 0.75; RMSE = 0.19) included quadratic effect of dietary ALA (% of total FA) as well as basal forage (grass and legumes silage or hay vs. corn silage), lipid supplementation type (no EFA supplementation vs. supplementation with oil vs. seed) and the fixed effect of trial. Corn silage had a negative coefficient (-0.08%) on milk ALA concentration prediction. Oil supplementation had a negative coefficient (-0.19%), whereas seed supplementation had a positive coefficient (+0.25%) on milk ALA concentration. The model to predict milk LA (% of total milk FA; R 2 = 0.53; RMSE = 0.48) included linear effect of dietary LA concentration (% of total FA) as well as lipid supplementation type (no EFA supplementation vs. supplementation with oil vs. seed) and the fixed effect of trial. Oil supplementation had a positive coefficient (+0.23%) on milk LA concentration. Regression between ALA or LA transfer efficiencies and dietary concentrations of these FA (% of dry matter) had a R 2 of 0.72 and 0.64, respectively. Transfer efficiencies of both EFA were correlated (R 2 = 0.66; P < 0.01). Even after the inclusion of the main explanatory factors in the models, a great inter-individual variability persisted in milk EFA concentrations. Lipid supplementation led to a greater increase in milk EFA with goats than what has been previously observed in cows, especially for ALA.