title: Performance and nitrogen use efficiency in mid-lactation dairy cows fed timothy cut in the afternoon or morning.
abstract: Shifting cutting from morning to afternoon has been shown to increase the concentration of nonstructural carbohydrates in forages. We hypothesized that, compared with a total mixed ration containing timothy baleage and silage cut in the morning (a.m.-cut TIM), a total mixed ration containing timothy baleage and silage cut in the afternoon (p.m.-cut TIM) would improve animal performance and N use efficiency in mid-lactation Holstein cows due to enhanced supply of ruminal fermentable energy. The objective of this study was to compare the effects of p.m.- versus a.m.-cut TIM on milk yield, concentrations and yields of milk components, ruminal metabolism, and plasma concentrations of AA in mid-lactation Holstein cows. Ten (6 ruminally cannulated) primiparous cows averaging 139±13 d in milk and 550±56 kg of body weight, and 6 (2 ruminally cannulated) multiparous cows averaging 128±11 d in milk and 632±57 kg of body weight at the beginning of the experiment, were used in a crossover design. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. The concentration of nonstructural carbohydrates (water-soluble carbohydrates plus starch) was numerically greater in the p.m.- versus the a.m.-cut TIM and averaged 13.2±1.06% and 12.2±1.13%, respectively. Treatment × parity effects were observed for milk urea N, feed efficiency, and milk N efficiency, whereas parity effects were observed for nutrient intake, milk yield, and plasma concentration of several essential and nonessential AA. Intakes of dry matter (19.3 versus 18.6 kg/d) and nonstructural carbohydrates (2.56 versus 2.31 kg/d), and yields of 4% fat-corrected milk (23.1 versus 22.2 kg/d), energy-corrected milk (25.0 versus 24.1 kg/d), milk fat (0.91 versus 0.88 kg/d), and milk protein (0.77 versus 0.73 kg/d) were all greatest with feeding p.m.-cut TIM. Milk yield (23.5 versus 22.7 kg/d) tended to increase in cows fed p.m.-cut TIM. The ruminal fermentation profiles and plasma concentrations of AA were mostly unaffected by treatments. However, ruminal valerate (1.01 versus 1.17 mol/100 mol) and plasma Gly (172 versus 188 µM) were lowest with feeding p.m.-cut TIM. Overall, feeding mid-lactation dairy cows a total mixed ration that consisted of p.m.-cut timothy baleage and silage significantly increased dry matter intake and yields of milk, milk fat, and milk protein.
authors.affiliation: Department of Biological Sciences, University of New Hampshire, Durham 03824.
authors.forename: A F
authors.initials: AF
authors.lastname: Brito
authors.affiliation: Soils and Crops Research and Development Centre, Agriculture and Agri-Food Canada, Québec City, QC, Canada G1V 2J3.
authors.forename: G F
authors.initials: GF
authors.lastname: Tremblay
authors.affiliation: Soils and Crops Research and Development Centre, Agriculture and Agri-Food Canada, Québec City, QC, Canada G1V 2J3.
authors.forename: A
authors.initials: A
authors.lastname: Bertrand
authors.affiliation: Soils and Crops Research and Development Centre, Agriculture and Agri-Food Canada, Québec City, QC, Canada G1V 2J3.
authors.forename: Y
authors.initials: Y
authors.lastname: Castonguay
authors.affiliation: Soils and Crops Research and Development Centre, Agriculture and Agri-Food Canada, Québec City, QC, Canada G1V 2J3.
authors.forename: G
authors.initials: G
authors.lastname: Bélanger
authors.affiliation: Soils and Crops Research and Development Centre, Agriculture and Agri-Food Canada, Québec City, QC, Canada G1V 2J3.
authors.forename: R
authors.initials: R
authors.lastname: Michaud
authors.affiliation: Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, QC, Canada J9X 5E4.
authors.forename: C
authors.initials: C
authors.lastname: Lafrenière
authors.affiliation: Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, QC, Canada J1M 1Z3.
authors.forename: R
authors.initials: R
authors.lastname: Martineau
authors.affiliation: Valacta, Dairy Production Centre of Expertise Québec-Atlantic, Sainte-Anne-de-Bellevue, QC, Canada H9X 3R4. Electronic address: rberthiaume@valacta.com.
authors.forename: R
authors.initials: R
authors.lastname: Berthiaume
mesh_terms: D000596:Amino Acids / Q000097:blood; D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D003612:Dairying; D004032:Diet / Q000662:veterinary; D004063:Digestion; D004734:Energy Metabolism; D005247:Feeding Behavior; D005260:Female; D005285:Fermentation; D005511:Food Handling / Q000379:methods; D007774:Lactation / Q000378:metabolism*; D008892:Milk / Q000737:chemistry; D008894:Milk Proteins / Q000032:analysis; D009584:Nitrogen / Q000378:metabolism*; D010298:Parity; D031784:Phleum / Q000378:metabolism*; D012417:Rumen / Q000378:metabolism; D012820:Silage
chemical_list: D000596:Amino Acids; D008894:Milk Proteins; D009584:Nitrogen
keywords: dairy cow; milk yield; nonstructural carbohydrates; timothy