title: Cholecystokinin mediates depression of feed intake in dairy cattle fed high fat diets.
abstract: Two experiments were conducted to investigate the effects of 1) different concentrations of dietary fat and 2) i.v. administration of a cholecystokinin receptor antagonist (MK-329) on feed intake and plasma concentrations of hormones and metabolites in dairy cattle. In Experiment 1, 4 lactating Holstein cows were used in a 4 x 4 Latin square design. Treatments were diets with 1) no fat added, 2) 30 g fat/kg feed (calcium salts of long-chain fatty acids as fat supplement), 3) 60 g fat/kg, and 4) 90 g fat/kg added. Cows were fed once daily a diet of concentrate, corn silage, alfalfa haylage, and alfalfa pellets. Dry matter intake decreased linearly with increasing concentrations of dietary fat (P < 0.0001). Overall plasma concentrations of nonesterified fatty acids (P < 0.0001), triacylglycerol (P < 0.0006), and cholecystokinin (P < 0.02), increased linearly with each level of dietary fat, but there was a linear decrease in plasma insulin (P < 0.0008). In Experiment 2, 4 nonpregnant and nonlactating Holstein heifers were used in a cross-over design in a 2 x 2 factorial arrangement of treatments. Treatments were diet (fatty acids, 27 g/kg vs 103 g/kg diet dry matter) and i.v. injections (MK-329 vs vehicle). Heifers were fed once daily a total mixed ration of corn silage, cracked corn and soybean meal with or without fat supplement. Diets were switched by period and either MK-329 (70 microg/kg body weight) or its vehicle was injected i.v. at 2 hr postfeeding. Daily dry matter intake was decreased by feeding the high fat diet (P < 0.02) but was not affected by injections. Injection of MK-329, however, increased dry matter intake by 92% in heifers fed the high fat diet during the first 2 hr postinjection compared to vehicle injection. Plasma pancreatic polypeptide concentration was increased by the high fat diet at 2 hr postfeeding (P < 0.02) but was lowered by MK-329 at 1 hr postinjection (P < 0.001). Plasma insulin was lowered by the high fat diet (P < 0.01) but was not affected by injections. The elevated plasma cholecystokinin concentration may have mediated depressed feed intake of dairy cattle fed the high fat diets.
authors.affiliation: Department of Animal Sciences, Ohio Agric. Res. And Develop. Ctr., The Ohio State University, 1680 Madison Avenue, Wooster, OH 44691-4096, USA.
authors.forename: B R
authors.initials: BR
authors.lastname: Choi
authors.forename: D L
authors.initials: DL
authors.lastname: Palmquist
authors.forename: M S
authors.initials: MS
authors.lastname: Allen
mesh_terms: D000818:Animals; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D002766:Cholecystokinin / Q000097:blood / Q000502:physiology*; D018592:Cross-Over Studies; D020109:Devazepide / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage*; D004435:Eating; D005227:Fatty Acids / Q000008:administration & dosage / Q000097:blood; D005260:Female; D006727:Hormone Antagonists / Q000008:administration & dosage; D007328:Insulin / Q000032:analysis; D007774:Lactation; D010191:Pancreatic Polypeptide / Q000097:blood; D011863:Radioimmunoassay / Q000662:veterinary; D014280:Triglycerides / Q000097:blood
chemical_list: D004041:Dietary Fats; D005227:Fatty Acids; D006727:Hormone Antagonists; D007328:Insulin; D014280:Triglycerides; D010191:Pancreatic Polypeptide; D002766:Cholecystokinin; D020109:Devazepide