Milk fat response to calcium salts of palm or soybean in a normal or milk fat depression scenario in dairy ewes

A limited number of studies in lactating sheep have compared milk fat responses to calcium salts (Ca-salts) differing in fatty acid (FA) composition and their interactions with different dietary conditions. The objective of this study was to evaluate the effects of Ca-salts of palm or soybean FA on milk fat under Normal and CLA-induced milk fat depression (MFD) scenarios in lactating dairy ewes. Thirty-eight Lacaune and thirty-seven East Friesian multiparous ewes were used in a 2 × 2 factorial design. The main factor consisted of two diets designed to create two distinct scenarios: Normal and CLA-induced MFD (CLA-MFD, 30 g/d of CLA 29.9% trans−10, cis−12 CLA as methyl ester). The subfactor was supplementation of Normal or CLA-MFD scenarios with 27 g/d of Ca-salts of palm FA, or 30 g/d of Ca-salts of soybean FA, resulting in four treatments: 1) Normal + Ca-Palm, 2) Normal + Ca-Soy, 3) CLA-MFD + Ca-Palm, and 4) CLA-MFD + Ca-Soy. Overall, the CLA-MFD scenario decreased milk fat concentration by 1.64% units and decreased milk fat yield by 17.3 g/d. Ewes that received Ca-Palm had overall 0.29% units higher milk fat concentration, and 13.4% greater milk fat concentration when fed the CLA-MFD diet. Ca-Soy increased trans−10 C18:1 (131.0%), trans-11 C18:1 (30.4%), and cis-9, trans-11 CLA (21.1%) in the CLA-MFD diet. In conclusion, supplementation with Ca-Palm resulted in overall greater milk fat concentration. In a MFD scenario, supplementation with Ca-Soy increased concentration of milk trans FA linked to altered rumen biohydrogenation and further aggravated MFD.