Optimal Calcium Propionate Supplementation in Early-Lactation Dairy Cows Improves Milk Yield and Alters Milk Composition

Calcium propionate serves as an effective feed additive for preventing hypocalcemia and ketosis in early-lactation dairy cows. This study investigated the effects of dietary calcium propionate levels (0, 200, 350, and 500 g/d) on productive performance, milk minerals, and fatty acid profiles in 32 Holstein cows. Productive performance was monitored daily through the peak of lactation (36–125 days in milk, DIM), with milk samples collected on 7, 21, and 35 DIM for mineral and fatty acid analysis. Results showed that calcium propionate supplementation tended to increase peak lactation milk yield, with the highest value (53.67 kg/d) observed in the 350 g/d group. The milk K concentration exhibited a quadratic increased response, with greater values in the 200 g/d and 350 g/d groups. Conversely, milk Mg and P concentrations and the proportions of short-chain fatty acids (C6:0, C8:0, and C12:0) decreased linearly with increasing calcium propionate supplementation levels. Furthermore, the proportions of C18:2 cis-9,12 and the sum of polyunsaturated fatty acids exhibited a quadratic decreased response, being lowest in the 350 g/d group. In conclusion, supplementing 350 g/d of calcium propionate optimally improved lactation performance and altered milk mineral and fatty acid profiles, suggesting its value in early-lactation management.