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Escape protein, rumen degradable protein, or energy as the first limiting nutrient of nursing calves grazing native sandhills range
Abstract
Grazing trials were conducted to determine the (1) first limiting nutrient in nursing calves grazing native range, (2) forage intake and diet selectivity of cow/calf pairs, and (3) rumen degradable protein (RDP) requirement of gestating cows on winter range. In Trial 1, spring-born nursing calves were individually fed: (1) escape protein (EP; heat treated SBM:feather meal); (2) protected fat and soyhulls (PF); or (3) no supplement (NS). Steer calves were finished for 200 d. Escape protein improved gains (P $<$.10) over PF and NS. Forage intake, cow ADG, finishing gains, and carcass characteristics were unaffected by treatment. In Trial 2, fall-born calves were individually fed: (1) PF; (2) wheat gluten and soyhulls (RDP); (3) EP (heat treated SBM:corn gluten meal); or (4) NS. The EP and PF gains were similar but EP improved gains over RDP and NS. Forage intakes and cow condition score (CS) were unaffected by treatment. Escape protein was more limiting than energy or RDP. Two trials were conducted to determine forage intake and diet selectivity of pairs grazing native range. In both trials, forage intake by nursing calves increased. Milk intake remained constant in Trial 1 and decreased in Trial 2. Forage intake of the dams ranged from 11.0 to 12.3 kg OM/d. Crude and EP were higher in calf than in cow diets while RDP, ADF, and IVOMD were similar. Forage intake of nursing calves increased to comprise the majority of the diet long before weaning. Two trials were conducted to determine the RDP requirement of gestating cows grazing winter range. In Trial 1, 80 crossbred cows (522 kg) were randomly assigned to: (1) 50%, (2) 75%, (3) 100%, or (4) 125% of the supplemental RDP requirement. In Trial 2, 80 crossbred cows (529 kg) were assigned to (1) 29%, (2) 65%, (3) 100%, (4) 139% of the supplemental RDP requirement. In Trial 1, ADG and CS were not different among treatments. In Trial 2, the 65% level increased gain over the 29%, 100%, and 139% levels (quadratic P $<$.01). CS was maintained at 65% and lost at 29%, 100%, and 139% (cubic effect; P $<$ 0.1). Forage intake was similar among treatments. Forage RDP intake was 322 g/d (Trial 1) and 279 g/d (Trial 2). Gestating cows grazing winter range need 62 to 140 g/d of supplemental RDP to meet the 340 to 430 g/d requirement.
Subject Area
Livestock
Recommended Citation
Hollingsworth-Jenkins, Karla Jean, "Escape protein, rumen degradable protein, or energy as the first limiting nutrient of nursing calves grazing native sandhills range" (1994). ETD collection for University of Nebraska-Lincoln. AAI9516582.
https://digitalcommons.unl.edu/dissertations/AAI9516582