Effects of pre- and postpartum dietary fat sources (soybean oil versus linseed oil) on lactation performance and blood metabolites in transition dairy cows

This study investigated the effects of supplementation with two calcium salt fatty acid sources (soybean oil (CaSO) and linseed oil (CaLN)) before and after parturition on lactation performance and blood metabolite profiles in dairy cows. A study was conducted with twenty-four multiparous Holstein cows (parity = 3.12 +/- 0.9 and Backfat thickness = 21.77 +/- 1.98) that were divided into a 2 x 2 factorial design 21 days before expected calving. The aim was to investigate the interplay between prepartum (CaSO or CaLN, at 2 % of dry matter) and postpartum (at 1.4 % of dry matter) fat supplementation on lactation performance and blood metabolite profiles. Initially, cows were grouped according to the source of prepartum fat (either CaSO or CaLN, with 12 cows in each group). Postpartum, these groups were further subdivided according to whether the fat source was administered continuously (LN-LN, SO-SO) or alternately (LN-SO, SO-LN) over a 28-day period. This resulted in four different treatment groups, each with six cows. The fat supplements contained 84 % fat and 9 % Ca. No statistically significant differences were found in dry matter intake (DMI), colostrum yield or most concentrations of blood metabolites (insulin, cholesterol, glucose, triglycerides, total protein, albumin, beta-hydroxybutyric acid (BHB), non-esterified fatty acids (NEFA), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and urea-N). However, cows fed CaSO prepartum had a significantly higher plasma concentration of insulin-like growth factor-1 (IGF-1) than cows fed CaLN. Cows fed CaSO had higher backfat thickness (BFT) from day -21-0 than those fed CaLN (P = 0.05). Notably, cows in the SO-SO group lost the most weight, while cows in the SO-LN group lost the least, especially on days 21 and 28 postpartum (P = 0.05). Switching from soybean oil prepartum to linseed oil postpartum (SO-LN) significantly increased milk production in the first 28 days of lactation compared to other diets. In addition, the fat content in milk was influenced by the type of fat supplementation prepartum, with cows receiving CaSO having a lower milk fat percentage than those receiving CaLN (P < 0.05). The results on blood parameters suggest potential benefits of the SO-LN diet for postpartum cows, as emphasized by stable BHB concentrations and the highest IGF-1 concentrations, especially without the elevated BHB concentrations typically associated with the SO-SO diet. The blood concentrations of total protein, urea-N, triglycerides and NEFA were not affected by the treatments. Also, the dietary change did not adversely affect liver function, as shown by unchanged AST and ALT concentrations. Therefore, the results suggest that a dietary intervention involving the administration of soybean oil prepartum and switching to linseed oil postpartum (SO-LN strategy) has the potential to improve milk yield during the early lactation period.