Impact of Calcium Propionate Supplementation on the Lactation Curve and Milk Metabolomic Analysis on Rambouillet Ewes

In lactating ewes, energy demand increases for milk production, reserve mobilizations, and body weight maintenance. For reconversion to energy, ruminants require ruminal propionate production because it is the most predominant substrate for gluconeogenesis and one of the most relevant pathways since it allows an adequate supply of glucose. Calcium propionate supplementation is an alternative to increase glucose production by an external additive. Thus, the objective was to evaluate the effect of calcium propionate (CaPr) on milk production and milk metabolomic profile on lactating ewes. Sixteen Rambouillet (65.3 ± 6.2 kg BW; three years old) were randomly assigned one of two experimental treatments: (a) basal diet without supplementation (CP/0S) and (b) basal diet + 30 g d^-1 of CaPr (CP/30S). The experimental period was from parturition day until day 60 (baby lamb weaning). A completely randomized design was used and analyzed with a mixed model. Initial and final lactating weight and milk production differed statistically (p < 0.05) between treatments. CP/30S led to differential changes (p < 0.05) in the lactation curve, showing significant milk production over eight-week measurements. Lactation peak (mL), maximum production (mL), and lactational persistency (d) were superior (p < 0.05) for supplemented ewes. An 11.4% variability was shown in a principal component analysis between treatments. For CP/0S, 63 bioactive compounds were detected, and 55 for CP/30S treatment. The metabolites detected in CP/0S showed that only fatty acid biosynthesis, biosynthesis of unsaturated fatty acids, and fatty acid elongation pathways were affected (p < 0.05) in milk. However, for CP/30S, metabolic pathways related (p < 0.05) were fatty acid biosynthesis, biosynthesis of unsaturated fatty acids, fatty acid elongation, phenylalanine metabolism, and steroid metabolism in milk samples. Calcium propionate supplementation increases milk performance and lactation persistency-induced changes in specific metabolic milk production pathways.