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The objective was to evaluate how dietary fat sources enriched with oleic, trans-octadecenoic, linoleic, or linolenic acids affected the plasma and liver fatty acid profiles of Holstein heifers (n = 22) and cows (n = 32) during the summer season. Fat supplements were the following: 1) sunflower oil (SFO - Trisun, Humko Oil, 80% C18:1), 2) Ca salt of trans-octadecenoic acids (TRANS- EnerG TR, Virtus Nutrition, 57% trans 6-12), 3) Ca salt of vegetable oils (MEGRMegalac- R, Church & Dwight Co, 30% C18:2), and 4) linseed oil (LSO- Archer Daniels Midland, 56% C18:3 and 16% C18:2). Supplemental fats were fed at 1.35% of dietary DM beginning at 29 d prior to expected calving date. After calving, fats were fed at 1.5% (oils) and 1.75% (Ca salts) of dietary DM for 15 wk. Three blood samples collected on a Monday-Wednesday-Friday schedule between 21 and 28 DIM were analyzed for fatty acids using gas chromatography. Liver samples were taken via biopsy on 2, 14±2, and 28±2 DIM, immediately frozen in liquid nitrogen and kept at -800C for fatty acid analysis. Feeding high oleic sunflower oil did not affect the C18:1 concentrations of plasma (12.35%) or liver (21.8%). Cows fed TRANS fats had greater concentrations of plasma C18:1 trans isomers in liver tissue (1.0, 1.4, 1.0, and 1.0% for diets 1, 2, 3, and 4, respectively). Concentrations of C18:2 were greater in cows fed MEGR (44.4%) compared to cows fed LSO (41.8%) but were not different from that of cows fed SFO (43.4%) or TRANS (45.2%). Cis-9, trans-11 CLA was greater in plasma (0.13, 0.13, 0.16, and 0.14%) and liver (0.41, 0.43, 0.50, and 0.47%) of cows fed MEGR compared to those fed SFO or TRANS. Cows fed LSO had greater concentrations of C18:3 (2.4, 2.5, 2.3, and 4.9%; 0.9, 0.9, 1.0, and 1.4%) and C20:5 (0.5, 0.5, 0.5, and 0.7%; 0.6, 0.6, 0.5, and 0.9%) in plasma and liver, respectively. Feeding dietary fats enriched with particular fatty acids resulted in increased concentrations of those fatty acids in the plasma and liver. [ABSTRACT FROM AUTHOR]

The objective was to evaluate how dietary fat sources of oleic, transoctadecenoic, linoleic, or linolenic acids affected bST, IGF-1, and PGF metabolite (PGFM) concentrations in plasma of Holstein heifers (n = 22) and cows (n = 32) during the summer season. Fat supplements were the following: 1) sunflower oil (SFO; Trisun, Humko Oil, 80% C18:1), 2) Ca salt of trans-octadecenoic acids (TRANS; EnerG TR, Virtus Nutrition, 57% trans 6-12 C18:1), 3) Ca salt of vegetable oils (MEGR; Megalac-R, Church & Dwight Co, 30% C18:2), and 4) linseed oil (LSO- Archer Daniels Midland, 56% C18:3 and 16% C18:2). Supplemental fats were fed at 1.35% of dietary DM beginning at 29 d prior to expected calving date. After calving, fats were fed at 1.5% (oils) and 1.75% (Ca salts) of dietary DM for 15 wk. Blood samples were taken thrice weekly during 7 wk for measurement of IGF-1 and bST and for the first 14 DIM for PGFM. Mean concentrations of plasma IGF-1 tended to be greater (P = 0.08) in heifers compared to cows (135 vs. 124 ng/ml) but did not differ among treatment groups (122, 135, 124, and 137 ng/ml for diets 1, 2, 3, and 4 respectively). Concentrations of IGF-1 increased at a faster rate for animals fed polyunsaturated fats compared to those fed monounsaturated fats. Mean concentrations of bST were not different among treatments. Plasma concentrations of bST decreased from 7.0 to 4.1 ng/ml over DIM for primiparous cows except those fed MEGR, which increased from 7.3 to 8.3 ng/ml. For multiparous cows, bST concentrations also decreased over time but those fed MEGR decreased at a faster rate (treatment by parity by DIM interaction). Cows fed TRANS had a higher initial plasma concentration of PGFM (4065 vs. 2408 ng/ml) and decreased at a faster rate than cows fed SFO but both reached baseline by 9 DIM. The PGFM concentrations of cows fed MEGR decreased at a slower rate compared to cows fed LSO, reaching baseline 2 d later. Dietary fatty acids alter hormonal status of lactating dairy cows. [ABSTRACT FROM AUTHOR]