The aim of the study was to test the effect of rumen-inert fat supplements of different chemical forms or containing different unsaturated/saturated (U/S) fatty acid contents on milk production, milk composition and liver and blood metabolic variables of high-yielding dairy cows in the peripartal period. Thirty Holstein-Friesian dairy cows were divided into three equal groups and fed a corn silage-based diet, without fat supplementation (control) or supplemented with 11·75 MJ NEl per day of calcium soaps of palm oil fatty acids (CAS; U/S=61/39) or with 11·75 MJ NEl per day of hydrogenated palm oil triglyceride (HTG; U/S=6/94). Each diet was fed from 25±2 d prior to the expected calving to 100±5 d post partum. Compared with the control, both CAS and HTG supplementation resulted in an increase of the average milk yield. Milk fat content and fat-corrected milk yield were higher in the HTG group but lower in the CAS group than in the control group. In all groups liver triglyceride concentrations (TGL) increased from 15 d prepartum to 5 d post partum, and then decreased thereafter. At 5 d TGL was lower in the HTG group than control or CAS cows. No significant differences were detected in TGL among dietary treatments at 15 d prepartum and 25 d post partum. Higher plasma glucose and insulin and lower non-esterified fattay acids and β-hydroxybutyrate concentrations and aspartate aminotransferase activity were measured in the HTG group than in the control or CAS groups at 5 d or 25 d post partum. Our results show that HTG may provide a better energy supply for high-yielding dairy cows in negative energy balance than CAS around calving.
Effects of feeding sainfoin proanthocyanidins to lactating ewes on intake, milk production and plasma metabolites
