Effects of abomasal infusion of essential fatty acids together with conjugated linoleic acid in late and early lactation on performance, milk and body composition, and plasma metabolites in dairy cows

摘要

Rations including high amounts of corn silage arecurrently very common in dairy production. Diets withcorn silage as forage source result in a low supply ofessential fatty acids, such as α-linolenic acid, and maylead to low conjugated linoleic acid (CLA) production.The present study investigated the effects of abomasalinfusion of essential fatty acids, especially α-linolenicacid, and CLA in dairy cows fed a corn silage–baseddiet on performance, milk composition, including fattyacid (FA) pattern, and lipid metabolism from late toearly lactation. Rumen-cannulated Holstein cows (n =40) were studied from wk 9 antepartum to wk 9 postpartumand dried off 6 wk before calving. The cows wereassigned to 1 of 4 treatment groups. Cows were abomasallysupplemented with coconut oil (CTRL, 76 g/d),linseed and safflower oil (EFA, 78 and 4 g/d; linseed/safflower oil ratio = 19.5:1; n-6-3 FA ratio = 1:3), Lutalin(CLA, 38 g/d; BASF SE, Ludwigshafen, Germany;isomers cis-9,trans-11 and trans-10,cis-12 each 10 g/d)or EFA+CLA. Milk composition was analyzed weekly,and blood samples were taken several times before andafter parturition to determine plasma concentrations ofmetabolites related to lipid metabolism. Liver sampleswere obtained by biopsy on d 63 and 21 antepartum andon d 1, 28, and 63 postpartum to measure triglycerideconcentration. Body composition was determined afterslaughter. Supplementation of CLA reduced milk fatconcentration, increased body fat mass, and improvedenergy balance (EB) in late and early lactation, butEB was lowest during late lactation in the EFA group.Cows with CLA treatment alone showed an elevatedmilk citrate concentration in early lactation, whereasEFA+CLA did not reveal higher milk citrate but didhave increased acetone. Milk protein was increased inlate lactation but was decreased in wk 1 postpartum inCLA and EFA+CLA. Milk urea was reduced by CLAtreatment during the whole period. After calving, theincrease of nonesterified fatty acids in plasma was lessin CLA groups; liver triglycerides were raised lowestat d 28 in CLA groups. Our data confirm an improvedmetabolic status with CLA but not with exclusive EFAsupplementation during early lactation. Increased milkcitrate concentration in CLA cows points to reducedde novo FA synthesis in the mammary gland, but milkcitrate was less affected in EFA+CLA cows, indicatingthat EFA supplementation may influence changes inmammary gland FA metabolism achieved by CLA.