Fig. 4

Effects of increasing linoleic (a) and α-linolenic acid (b) supplementation to lactation diets on the balance (net uptake minus output in milk) of essential fatty acids during lactation. Symbols represent the estimated EFA balance using results reported in 6 studies published from 1977 to 2015 [26, 37, 52–55]. Observations with response means greater than 2 standard deviations from the mean were considered outliers and excluded from the analysis. Linear and non-linear (quadratic, cubic) models were compared using goodness-of-fit tests. Minimum Bayesian information criterion (BIC), minimum root mean square error (RMSE), and maximum coefficient of determination (R²) techniques were used to select the best-fit model. Weighted models were constructed with sample size (n = 3 to 33 sows per data point) as weight