title: Glucose metabolism in crossbred Holstein cattle feeding on two types of roughage at different stages of lactation.
abstract: An experiment was performed to study the glucose kinetics of crossbred Holstein cattle feeding on either hay or 5% urea-treated rice straw during early lactation (30 days post partum), mid-lactation (120 days post partum) and late lactation (210 days post partum). Two breeds: Holstein FriesianxRed Sindhi (50:50 = 50% HF) and Holstein FriesianxRed Sindhi (87.5:12.5 = 87.5% HF) were used. In early lactating 87.5% HF animals feeding on either hay or urea-treated rice straw, the high milk yields and lactose secretion were related to glucose uptake by the udder and udder blood flow as compared with those of 50% HF animals. Marked decreases in udder blood flow, glucose uptake, lactose secretion and milk yield were apparent in mid- and late lactation of both groups of 87.5% HF animals. In contrast, both groups of 50% HF animals showed no significant changes in udder blood flow, udder glucose uptake, lactose secretion and milk yields throughout the course of lactation. Total glucose entry rate using 3-[3H] glucose infusion, recycling of glucose carbon and plasma glucose clearance significantly increased during late lactation for 50 and 87.5% HF animals feeding on urea-treated rice straw. The utilization rates of glucose using [U-(14)C] glucose infusion were not significantly different among groups of animals and periods of lactation. It can be concluded that 87.5% HF animals have the genetic potential for a higher milk yield, but a shorter peak yield and poorer persistence in comparison with 50% HF animals. Changes in the utilization of glucose by the mammary gland for milk production in both groups of crossbred animals during feeding on either hay or urea-treated rice straw would be dependent on intramammary changes.
authors.affiliation: Department of Physiology, Faculty of Veterinary Science, Chulalongkorn University, Henri Dunant Road, Patumwan, Bangkok, Thailand. narongsak.c@chula.ac.th
authors.forename: N
authors.initials: N
authors.lastname: Chaiyabutr
authors.forename: S
authors.initials: S
authors.lastname: Preuksagorn
authors.forename: S
authors.initials: S
authors.lastname: Komolvanich
authors.forename: S
authors.initials: S
authors.lastname: Chanpongsang
mesh_terms: D000821:Animal Feed; D000822:Animal Husbandry; D000818:Animals; D002417:Cattle / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D003433:Crosses, Genetic; D005260:Female; D005947:Glucose / Q000378:metabolism*; D007774:Lactation / Q000378:metabolism* / Q000502:physiology; D007785:Lactose / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000098:blood supply / Q000378:metabolism; D008892:Milk / Q000378:metabolism; D011247:Pregnancy; D013997:Time Factors
chemical_list: D005947:Glucose; D007785:Lactose