title: Digestion in steers and lactational performance of Jersey cows fed diets varying in natural protein level continuously or on alternate days.
abstract: Five crossbred beef steers (515 kg) were used in a Latin square experiment and 36 lactating Jersey cows (12 primiparous, 310 kg; 24 multiparous, 365 kg) were used in a completely randomized design study to determine effects on characteristics of digestion and lactational performance of daily alternation of the dietary level of natural protein (NP). In Experiment 1, steers were fed diets of 50% bermudagrass hay and 50% concentrate. Concentrate was approximately 18% crude protein (CP), formulated to be 60, 80 or 100% NP (varying proportions of soybean meal, urea and ground corn), and was fed at 1.5% body weight (dry matter basis). These concentrates were fed daily or ones with 60 and 100% NP were fed on alternate days. Alternate day feeding did not markedly affect characteristics of digestion, including ruminal escape of feed protein, and NP level of concentrate fed continuously had no effects either. In Experiment 2, cows were subjected to treatments similar to those in Experiment 1, and performance on d 20-40 of lactation was measured. Concentrate was given at 1 kg (as fed)/2.15 kg milk produced, yielding a dietary concentrate level of approximately 40% (dry matter basis). Alternate feeding depressed (P less than 0.05) overall milk fat percentage. Alternate feeding increased production of milk and protein and body weight of primiparous cows but caused little change with multiparous cows. Besides increasing the dietary level of concentrate, perhaps alternate feeding regimes have utility to lower milk fat level without impairing milk production. Level of NP in concentrate fed continuously did not affect performance by multiparous cows though primiparous cow performance was generally enhanced, possibly because CP intake was adequate for multiparous cows but marginal for primiparous cows. However, overall, efficiency of production of solids-corrected milk rose slightly with increasing NP.
authors.affiliation: University of Arkansas, Fayetteville 72701.
authors.forename: D S
authors.initials: DS
authors.lastname: Hubbell
authors.forename: A L
authors.initials: AL
authors.lastname: Goetsch
authors.forename: K F
authors.initials: KF
authors.lastname: Harrison
authors.forename: D L
authors.initials: DL
authors.lastname: Galloway
authors.forename: L A
authors.initials: LA
authors.lastname: Forster
authors.forename: W
authors.initials: W
authors.lastname: Sun
mesh_terms: D000641:Ammonia / Q000032:analysis; D000821:Animal Feed; D000818:Animals; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D004044:Dietary Proteins / Q000008:administration & dosage*; D004063:Digestion; D004435:Eating; D005260:Female; D006863:Hydrogen-Ion Concentration; D007774:Lactation; D007785:Lactose / Q000032:analysis; D008055:Lipids / Q000032:analysis; D008297:Male; D008892:Milk / Q000032:analysis; D008894:Milk Proteins / Q000032:analysis; D010298:Parity; D011897:Random Allocation; D012417:Rumen / Q000737:chemistry / Q000502:physiology
chemical_list: D004044:Dietary Proteins; D008055:Lipids; D008894:Milk Proteins; D000641:Ammonia; D007785:Lactose