Milk production, peripartal liver triglyceride concentration and plasma metabolites of dairy cows fed diets supplemented with calcium soaps or hydrogenated triglycerides of palm oil.

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 fatty acids and beta-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.