title: Wheat straw or alfalfa hay in diets with 30% neutral detergent fiber for lactating Holstein cows.
abstract: Twenty-four Holstein cows near peak lactation were fed diets formulated to contain 30% NDF with forage NDF from chopped wheat straw or chopped alfalfa hay in proportions of 0:3, 1:2, 2:1, and 3:0 in an 8-wk trial to evaluate effects of fiber source on lactational performance. Concentrate was based on highly degradable carbohydrate in steam-flaked sorghum grain. Forage to concentrate ratio decreased from 49:51 to 28:72 when straw was substituted for alfalfa hay. Milk yield (38.4 kg/d) and DMI (23.1 kg/d) were not influenced by forage source. Milk fat percentage decreased and milk protein percentage increased linearly with increasing straw. Yields of 3.5% FCM and fat showed linear and quadratic responses, because they appeared to be reduced only on the 0:3 diet, and protein yield showed a quadratic response and was highest for the 1:2 diet. Digestibility of NDF averaged 43.5, 45.4, 40.7, and 31.2%, and acetate to propionate ratio was 3.0, 2.4, 2.2, and 1.9 with increasing dietary straw. Passage rates were not influenced by diet and averaged 9.3, 7.6, 6.1, and 4.7%/h for fluid, grain, alfalfa hay, and wheat straw, respectively. It is suggested that the ratio of forage NDF to ruminally degradable starch be maintained greater than or equal to 1:1 when diets based on low quality forage are fed to cows in early lactation.
authors.affiliation: Department of Animal Science, University of Arizona, Tucson 85721.
authors.forename: M H
authors.initials: MH
authors.lastname: Poore
authors.forename: J A
authors.initials: JA
authors.lastname: Moore
authors.forename: R S
authors.initials: RS
authors.lastname: Swingle
authors.forename: T P
authors.initials: TP
authors.lastname: Eck
authors.forename: W H
authors.initials: WH
authors.lastname: Brown
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004043:Dietary Fiber / Q000008:administration & dosage*; D004063:Digestion; D005232:Fatty Acids, Volatile / Q000032:analysis; D005260:Female; D007774:Lactation; D008055:Lipids / Q000032:analysis; D000455:Medicago sativa; D008892:Milk / Q000032:analysis / Q000378:metabolism; D008894:Milk Proteins / Q000032:analysis; D012417:Rumen / Q000737:chemistry / Q000502:physiology; D014908:Triticum
chemical_list: D004043:Dietary Fiber; D005232:Fatty Acids, Volatile; D008055:Lipids; D008894:Milk Proteins