title: Fatty acid metabolism in liver of dairy cows fed supplemental fat and nicotinic acid during an entire lactation.
abstract: Liver biopsies from 38 multiparous Holstein cows were used to determine rates of peroxisomal beta-oxidation and total beta-oxidation of palmitate in liver homogenates and contents of total lipid, triglyceride, and glycogen during the lactation cycle. Cows were assigned to one of four diets from wk 4 through wk 42 of lactation: control, control plus nicotinic acid (12 g/d), supplemental fat, or supplemental fat plus nicotinic acid. Liver biopsies were obtained at wk 3 (covariate), 6, 12, 24, and 42 of lactation. Neither supplemental fat nor nicotinic acid affected palmitate oxidation in liver homogenates or liver composition. Peroxisomal beta-oxidation capacity and the ratio of peroxisomal to total beta-oxidation decreased from wk 3 to 12 and then increased at wk 42. Contents of total lipid and triglyceride decreased, and content of glycogen increased, from wk 3 to 12. Total oxidation capacity in liver homogenates was correlated negatively with total lipid and triglyceride in liver, yields of milk and solids-corrected milk (SCM), and plasma nonesterified fatty acids (NEFA), and was correlated positively with liver glycogen, dry matter intake (DMI), energy balance, and plasma glucose. Peroxisomal beta-oxidation was correlated negatively with yields of milk and SCM. The ratio of peroxisomal to total beta-oxidation was correlated positively with liver total lipid, liver TG, and plasma NEFA and negatively with DMI and energy balance. When only data from wk 3 postpartum were considered, both total and peroxisomal beta-oxidation were correlated negatively with hepatic concentrations of total lipid and TG. Peroxisomal beta-oxidation in liver of dairy cows is not affected by feeding supplemental fat or nicotinic acid during wk 4 to 42 of lactation but may be a part of the hepatic adaptations to negative energy balance.
authors.affiliation: Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Grum
authors.forename: J K
authors.initials: JK
authors.lastname: Drackley
authors.forename: J H
authors.initials: JH
authors.lastname: Clark
mesh_terms: D000818:Animals; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D004041:Dietary Fats / Q000008:administration & dosage* / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D006003:Glycogen / Q000378:metabolism; D007774:Lactation; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D008892:Milk / Q000737:chemistry / Q000378:metabolism; D009525:Niacin / Q000008:administration & dosage* / Q000378:metabolism; D010084:Oxidation-Reduction; D010168:Palmitates / Q000378:metabolism*; D020675:Peroxisomes / Q000378:metabolism; D011897:Random Allocation; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism
chemical_list: D004041:Dietary Fats; D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D010168:Palmitates; D014280:Triglycerides; D009525:Niacin; D006003:Glycogen