title: Ruminal digestion and fermentation of high-producing dairy cows with three different feeding systems combining pasture and total mixed rations.
abstract: Six multiparous Holstein cows fitted with rumen cannulas were used to study the effect of three feeding systems combining pasture and total mixed rations (TMR) on ruminal digestion in a 21-wk repeated measures experiment. The three treatments were: 1) pasture plus concentrate (PC), 2) pasture plus partial TMR (pTMR), and 3) TMR (nonpasture). Ruminal NH3-N concentration was lower on both the pTMR and TMR treatments (10.2 +/- 0.5 mg/dL) than on the PC treatment (19.9 +/- 0.5 mg/dL). Ruminal pH was not affected by treatments and averaged 5.87. Neither total volatile fatty acid concentration (137.5 mmol/L) nor individual volatile fatty acid proportions (63.1,20.6, and 12.0 mol/ 100 mol for acetate, propionate, and butyrate, respectively) differed among treatments. The pTMR treatment reduced the total potentially degradable fraction of dry matter (85.5 vs. 82.3%) and the potentially digestible fraction of neutral detergent fiber (82.1 vs. 74.9%) of pasture compared to the PC treatment. Ruminal NH3-N losses were reduced when combining pasture and TMR; however this combination decreased the ruminal digestion of pasture, indicating the presence of associative effects in the rumen.
authors.affiliation: Department of Dairy and Animal Science, The Pennsylvania State University, University Park 16802, USA. fbargo@dns.ans.com
authors.forename: F
authors.initials: F
authors.lastname: Bargo
authors.forename: L D
authors.initials: LD
authors.lastname: Muller
authors.forename: G A
authors.initials: GA
authors.lastname: Varga
authors.forename: J E
authors.initials: JE
authors.lastname: Delahoy
authors.forename: T W
authors.initials: TW
authors.lastname: Cassidy
mesh_terms: D000641:Ammonia / Q000032:analysis; D000821:Animal Feed; D000822:Animal Husbandry / Q000379:methods; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000254:growth & development / Q000502:physiology*; D003902:Detergents; D004043:Dietary Fiber / Q000008:administration & dosage / Q000378:metabolism; D004063:Digestion; D002149:Energy Intake; D005223:Fats / Q000032:analysis; D005232:Fatty Acids, Volatile / Q000032:analysis; D005260:Female; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007774:Lactation / Q000502:physiology*; D008892:Milk / Q000737:chemistry / Q000378:metabolism; D008894:Milk Proteins / Q000032:analysis; D006109:Poaceae; D012417:Rumen / Q000737:chemistry / Q000378:metabolism* / Q000382:microbiology
chemical_list: D003902:Detergents; D004043:Dietary Fiber; D005223:Fats; D005232:Fatty Acids, Volatile; D008894:Milk Proteins; D000641:Ammonia