title: Supplementation of growing cattle grazing warm-season grass with proteins of various ruminal degradabilities.
abstract: This study was conducted to determine in situ ruminal protein degradation and animal responses to ruminally degraded and escape protein supplementation of warm-season grass. Cattle grazed a mixed stand of primarily big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) with some indiangrass (Sorghastrum nutans [L.] Nash) from the 1st wk of June to the 3rd wk of August. In 1987, 72 yearling steers (286 kg) were allotted randomly to three treatments: energy control (cornstarch-molasses mixture) or energy control plus .1 or .2 kg.animal-1.d-1 of escape protein. The total amount of a supplement fed per day was 1 kg. In 1988, 90 yearling heifers (240 kg) were allotted to five treatments: negative control (no supplement), energy control, energy control plus .14 kg.animal-1.d-1 of escape protein, energy control plus .18 kg.animal-1.d-1 of ruminally degraded protein, or .36 kg.animal-1.d-1 of protein supplied by a combination of the two protein sources. The total amount of a supplement fed per day was 1.7 kg. During 1987, the .2-kg level of escape protein produced the greatest gains (P < .10). In 1988, gains did not differ between the control and escape protein treatments. Ruminally degraded protein tended (P = .12) to increase gains (.09 kg/d) compared with the energy control. The combination treatment supported .13 kg/d more ADG (P < .10) than the negative and energy controls and the escape protein treatment. Ruminal ammonia concentrations in unsupplemented steers were low, with few values > 5 mg/dL. Based on in situ measurements, 42 to 54% of the forage protein escaped ruminal degradation.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Agronomy, University of Nebraska, Lincoln 68588.
authors.forename: J L
authors.initials: JL
authors.lastname: Hafley
authors.forename: B E
authors.initials: BE
authors.lastname: Anderson
authors.forename: T J
authors.initials: TJ
authors.lastname: Klopfenstein
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000254:growth & development* / Q000502:physiology; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D005260:Female; D005527:Food, Fortified; D008297:Male; D006109:Poaceae; D011897:Random Allocation; D012417:Rumen / Q000378:metabolism*; D015430:Weight Gain
chemical_list: D004044:Dietary Proteins