title: The effect of concentrate supplementation on nutrient flow to the omasum in dairy cows receiving freshly cut grass.
abstract: An experiment was carried out to determine the effect of increasing the amount of grain-based concentrate (0, 3, or 6 kg/d) on nutrient flow to the omasum, rumen fermentation pattern, milk yield, and nutrient use of dairy cows. Harvested timothy-meadow fescue grass was fed individually 3 times daily to 6 rumen-cannulated Holstein-Friesian cows in a duplicated 3 x 3 Latin square experiment. Grass was offered as 6 equal meals daily, and concentrates were fed as 2 equal meals daily. Nitrogen, microbial N, and neutral detergent fiber (NDF) flow from the rumen were measured using an omasal sampling technique in combination with a triple marker method [CoEDTA, Yb, and indigestible NDF (INDF) as markers]. Concentrate supplementation linearly decreased ruminal pH, N degradability, ammonia N concentration, and molar proportion of acetate and increased the molar proportion of butyrate. Supplementation of grass with concentrates linearly increased dry matter intake (DMI), microbial N synthesis, N, and NDF flow to the omasum, and ruminal and total tract NDF digestibility decreased linearly. Decreases in NDF digestibility in response to concentrates was primarily related to a decrease in the rate of digestion. Increased DMI overcame the negative effects of concentrate on NDF digestion, resulting in a linear increase in total metabolizable energy intake and milk production. Physical constraints were found not to limit grass DMI. Concentrate supplementation increased the apparent use of dietary N for milk production because of a reduction in N intake, rather than thorough improvements in N capture in the rumen.
authors.affiliation: MTT Agrifood Research Finland, North Savo Research Station, FIN-71750 Maaninka, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Sairanen
authors.forename: H
authors.initials: H
authors.lastname: Khalili
authors.forename: J I
authors.initials: JI
authors.lastname: Nousiainen
authors.forename: S
authors.initials: S
authors.lastname: Ahvenjärvi
authors.forename: P
authors.initials: P
authors.lastname: Huhtanen
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D004043:Dietary Fiber / Q000008:administration & dosage / Q000378:metabolism; D019587:Dietary Supplements; D004063:Digestion; D004435:Eating; D005232:Fatty Acids, Volatile / Q000032:analysis / Q000378:metabolism; D005260:Female; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007774:Lactation / Q000378:metabolism; D008892:Milk / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D009851:Omasum / Q000737:chemistry / Q000378:metabolism*; D006109:Poaceae; D011897:Random Allocation; D012417:Rumen / Q000737:chemistry / Q000378:metabolism* / Q000382:microbiology
chemical_list: D004043:Dietary Fiber; D005232:Fatty Acids, Volatile; D009584:Nitrogen