title: Effects of dietary nitrogen levels and carbohydrate sources on apparent ruminal synthesis of some B vitamins in dairy cows.
abstract: Effects of nitrogen level and carbohydrate source on apparent ruminal synthesis (ARS) of thiamin, riboflavin, niacin, vitamin B6, folates, and vitamin B12 were evaluated using 4 lactating Holstein cows distributed in a 4 × 4 Latin square design with treatments following a 2 × 2 factorial arrangement. Cows were fitted with cannulas in the rumen and proximal duodenum. The treatments were 2 N levels and 2 carbohydrate sources. The diet with the high N level provided 14% crude protein, calculated to meet 110% of the protein requirements and an adequate supply in rumen-degradable protein, whereas the diet with the low N level contained 11% crude protein, calculated to meet 80% of the protein requirements with a shortage in rumen-degradable protein. Carbohydrate source treatments differed by their nature (i.e., high in starch from barley, corn, and wheat, or high in fiber from soybean hulls and dehydrated beet pulp). All 4 diets were isoenergetic, based on corn silage, and had the same forage-to-concentrate ratio (60:40, dry matter basis). Duodenal flow was determined using YbCl3 as a marker. Each B-vitamin ARS was calculated as duodenal flow minus daily intake. The intake of several B vitamins varied among treatments, but because the animals consumed a similar amount of feed every day (average of 20 kg of dry matter/d) the difference was mostly due to vitamin content of each ingredient and their relative proportion in the diets. Decreasing N concentration in the diet reduced vitamin B6 duodenal flow and increased its apparent ruminal degradation. It also decreased duodenal flow and ARS of folates. The high-starch diets increased duodenal flow and ruminal balance of riboflavin, vitamin B6, and folates, whereas the high-fiber diets increased vitamin B12 ARS and duodenal flow. These effects on apparent synthesis are possibly due to changes in ruminal fermentation.
authors: Agriculture and Agri-Food Canada, Dairy and Swine Research and Development Centre, Sherbrooke, Québec, J1M 0C8, Canada; Département des sciences animales, Université Laval, Québec, Québec, G1V 0A6, Canada.
authors: V
authors: V
authors: Beaudet
authors: Département des sciences animales, Université Laval, Québec, Québec, G1V 0A6, Canada.
authors: R
authors: R
authors: Gervais
authors: INRA-VetagroSup, UMR1213 Herbivores, F-63122 Saint-Genès-Champanelle, France.
authors: B
authors: B
authors: Graulet
authors: INRA-VetagroSup, UMR1213 Herbivores, F-63122 Saint-Genès-Champanelle, France.
authors: P
authors: P
authors: Nozière
authors: INRA-VetagroSup, UMR1213 Herbivores, F-63122 Saint-Genès-Champanelle, France.
authors: M
authors: M
authors: Doreau
authors: INRA, UR143 Unité de Recherches Zootechniques, F-97170 Petit-Bourg, Guadeloupe, France.
authors: A
authors: A
authors: Fanchone
authors: Agriculture and Agri-Food Canada, Dairy and Swine Research and Development Centre, Sherbrooke, Québec, J1M 0C8, Canada; Département des sciences animales, Université Laval, Québec, Québec, G1V 0A6, Canada.
authors: D D S
authors: DDS
authors: Castagnino
authors: Agriculture and Agri-Food Canada, Dairy and Swine Research and Development Centre, Sherbrooke, Québec, J1M 0C8, Canada. Electronic address: Christiane.Girard@agr.gc.ca.
authors: C L
authors: CL
authors: Girard
mesh_terms: D000818:Animals; D002417:Cattle; D004032:Diet / Q000662:veterinary*; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004043:Dietary Fiber / Q000378:metabolism; D005260:Female; D005285:Fermentation; D001467:Hordeum / Q000378:metabolism; D007774:Lactation; D009584:Nitrogen / Q000378:metabolism*; D012417:Rumen / Q000378:metabolism*; D012820:Silage / Q000592:standards; D013213:Starch / Q000378:metabolism; D014908:Triticum / Q000378:metabolism; D014805:Vitamin B 12 / Q000494:pharmacology; D014803:Vitamin B Complex / Q000096:biosynthesis*; D003313:Zea mays / Q000378:metabolism
chemical_list: D004040:Dietary Carbohydrates; D004043:Dietary Fiber; D014803:Vitamin B Complex; D013213:Starch; D009584:Nitrogen; D014805:Vitamin B 12
keywords: B-vitamin ruminal synthesis; carbohydrate source; dairy cow; nitrogen