title: Composition and functional capacity of blood mononuclear leukocyte populations from neonatal calves on standard and intensified milk replacer diets.
abstract: Effects of increased dietary energy and protein on the composition and functional capacities of blood mononuclear leukocyte populations from milk replacer-fed calves were investigated. Holstein bull calves (average age: 4.2 d; n = 19) were assigned randomly to one of two treatment groups. Treatment 1 calves (n = 9) were fed a 20% crude protein, 20% fat milk replacer at a rate of 1.4% body weight of dry matter/d for 8 wk, whereas treatment 2 calves (n = 10) were fed a 30% crude protein, 20% fat milk replacer at a rate of 2.5% body weight of dry matter per day. Composition and functional capacities of mononuclear leukocyte populations from blood samples collected at 4, 18, 32, 46, and 60 d of age were characterized by flow cytometry and ex vivo cell function assays. From 11 to 60 d of age, the mean daily weight gain of treatment 2 calves (1.20 kg/d) was greater than daily weight gain of treatment 1 calves (0.55 kg/d). At 60 d of age, the mean body weight of treatment two calves was 53% (39 kg) greater than the mean body weight of treatment 1 calves. Total numbers of blood leukocytes and the composition of the mononuclear leukocyte population were unaffected by the plane of nutrition. Mitogen-induced DNA-synthesis and immunoglobulin M secretion also were unaffected by dietary treatment. Blood mononuclear leukocytes from calves on intensified diets, however, produced less interferon-gamma and more inducible nitric oxide, suggesting that increased dietary energy and protein affects specific aspects of leukocyte function associated with cell-mediated immunity. The impact of altered interferon-gamma and NO production on the calf s susceptibility to infectious disease are not known. Mononuclear leukocyte populations from all calves also demonstrated age-related changes in composition and functional capacity, likely reflecting natural exposure to infectious agents and maturation of the calfs immune system.
authors.affiliation: Periparturient Diseases of Cattle Research Unit, USDA, ARS, National Animal Disease Center, Ames 50010, USA. bnonneck@nadc.ars.usda.gov
authors.forename: B J
authors.initials: BJ
authors.lastname: Nonnecke
authors.forename: M R
authors.initials: MR
authors.lastname: Foote
authors.forename: J M
authors.initials: JM
authors.lastname: Smith
authors.forename: B A
authors.initials: BA
authors.lastname: Pesch
authors.forename: M E
authors.initials: ME
authors.lastname: Van Amburgh
mesh_terms: D000375:Aging / Q000097:blood / Q000276:immunology; D000818:Animals; D000831:Animals, Newborn / Q000097:blood / Q000254:growth & development / Q000276:immunology*; D002417:Cattle / Q000097:blood / Q000254:growth & development / Q000276:immunology*; D004041:Dietary Fats / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005434:Flow Cytometry / Q000662:veterinary; D005526:Food, Formulated; D007111:Immunity, Cellular / Q000502:physiology; D007963:Leukocytes, Mononuclear / Q000276:immunology* / Q000502:physiology; D008297:Male; D011897:Random Allocation; D015430:Weight Gain / Q000502:physiology
chemical_list: D004041:Dietary Fats; D004044:Dietary Proteins