title: High-concentrate diets based on forages harvested at different maturity stages affect ruminal synthesis of B vitamins in lactating dairy cows.
abstract: Effects of plant maturity on apparent ruminal synthesis and post-ruminal supply of B vitamins were evaluated in two feeding trials. Diets containing alfalfa (Trial 1) or orchardgrass (Trial 2) silages harvested either (1) early cut, less mature (EC) or (2) late cut, more mature (LC) as the sole forage were offered to ruminally and duodenally cannulated lactating Holstein cows in crossover design experiments. In Trial 1, conducted with 16 cows (569±43 kg of empty BW (ruminal content removed) and 43.7±8.6 kg/day of 3.5% fat-corrected milk yield; mean±SD) in two 17-day treatment periods, both diets provided ~22% forage NDF and 27% total NDF, and the forage-to-concentrate ratios were 53 : 47 and 42 : 58 for EC and LC, respectively. In Trial 2, conducted with 13 cows (588±55 kg of empty BW and 43.7±7.7 kg/day of 3.5% fat-corrected milk yield; mean±SD) in two 18-day treatment periods, both diets provided ~25% forage NDF and 31% total NDF; the forage-to-concentrate ratios were 58 : 42 and 46 : 54 for EC and LC, respectively. Thiamin, riboflavin, niacin, vitamin B6, folates and vitamin B12 were measured in feed and duodenal content. Apparent ruminal synthesis was calculated as the duodenal flow minus the intake. Diets based on EC alfalfa decreased the amounts of thiamin, niacin and folates reaching the duodenum, whereas diets based on EC orchardgrass increased riboflavin duodenal flow. Daily apparent ruminal synthesis of thiamin, riboflavin, niacin and vitamin B6 were correlated negatively with their intake, suggesting a microbial regulation of their concentration in the rumen. Vitamin B12 apparent ruminal synthesis was correlated negatively with total volatile fatty acids concentration, but positively with ruminal pH and microbial N duodenal flow.
authors: 1Agriculture and Agri-Food Canada,Sherbrooke Research and Development Centre,2000 College,Sherbrooke,QC,CanadaJ1M 0C8.
authors: D S
authors: DS
authors: Castagnino
authors: 3Department of Animal Science,Michigan State University,East Lansing,MI 48824-1225,USA.
authors: K L
authors: KL
authors: Kammes
authors: 3Department of Animal Science,Michigan State University,East Lansing,MI 48824-1225,USA.
authors: M S
authors: MS
authors: Allen
authors: 2Département des sciences animales,Université Laval,2425 rue de l'Agriculture,Québec,QC,CanadaG1V 0A6.
authors: R
authors: R
authors: Gervais
authors: 2Département des sciences animales,Université Laval,2425 rue de l'Agriculture,Québec,QC,CanadaG1V 0A6.
authors: P Y
authors: PY
authors: Chouinard
authors: 1Agriculture and Agri-Food Canada,Sherbrooke Research and Development Centre,2000 College,Sherbrooke,QC,CanadaJ1M 0C8.
authors: C L
authors: CL
authors: Girard
mesh_terms: D000824:Animal Nutritional Physiological Phenomena / Q000187:drug effects; D000818:Animals; D002417:Cattle / Q000502:physiology*; D031745:Dactylis / Q000737:chemistry*; D004032:Diet / Q000662:veterinary; D005260:Female; D007774:Lactation; D000455:Medicago sativa / Q000737:chemistry*; D012417:Rumen / Q000502:physiology*; D012820:Silage / Q000032:analysis; D014803:Vitamin B Complex / Q000096:biosynthesis*
chemical_list: D014803:Vitamin B Complex
keywords: B vitamin; dairy cow; forage maturity; ruminal synthesis