PROTEIN SUPPLEMENTATION OF BRANGUS STOCKER CALVES GRAZING WINTER TALLGRASS PRAIRIE

Authors: APPEDDU, LISA - SW OKLA. STATE UNIVEREWSS; Brown, Michael

Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/23/2003
Publication Date: 6/15/2003
Citation: Appeddu, L.A., Brown, M.A. 2003. Protein supplementation of Brangus stocker calves grazing winter tallgrass prairie [abstract]. Western Section of Animal Science Proceedings. 81(1):33.

Interpretive Summary: In the Southern Great Plains, producers can utilize annual winter wheat as both a pasture resource and grain crop. During most years, this system provides readily available nutrients that support high rates of inexpensive gain in stocker calves or in replacement heifers. However, fall weather conditions are not always favorable for early seeding and (or) sufficient growth of wheat pasture to support late-fall or winter grazing. Producers who commit to retaining or receiving calves in the fall must have cost-effective alternatives. Results from research at the USDA-ARS Grazinglands Research Laboratory suggest Brangus calves can be wintered on lower quality tallgrass prairie pasture with modest levels of protein supplementation when annual cool season forages are not available. Calculations revealed an estimated 454 g of protein per day would have to be provided to ensure maintenance of calf gain. Protein supplementation using fish meal improved heifer utilization of dormant tallgrass prairie compared to supplementation with only cottonseed meal. However, improvements in weight gains might not justify the higher cost of the fish meal in the protein supplement.

Technical Abstract: In years when growing conditions are not favorable for establishment of fall wheat pasture in the Southern Great Plains, producers need cost-effective grazing alternatives for calves until spring wheat pasture is available. The objective of this research was to evaluate the potential of wintering Brangus calves on dormant perennial tallgrass prairie and offering limited amounts of a cottonseed meal (CSM, 70.2% cottonseed meal) or fish meal (FM, 50% cottonseed meal, 20% fish meal) protein supplement. Two weeks after weaning in October 2000, 90 calves were sorted by sex and placed on one of four pastures (big bluestem, little bluestem, dropseed, downy brome; avg 49.5% ADF and 5.5% CP). Calves were initially supplemented by pasture with CSM (20 steers and 25 heifers) or FM (20 steers and 25 heifers) for 90 d at 908 g/hd/d. Measures included calf weights, hip height, serum metabolites and ADF digestibility using acid detergent insoluble ash as an internal marker. Supplements had 42% CP and similar in situ digestibilities. Calves lost weight during the first 40 d on pasture (-0.21 kg/d); therefore, daily supplement amounts were increased to 1362 g/hd/d. No differences in gain were detected between steer groups over the last 50 d (0.44 +/- 0.038 kg/d), but heifers fed FM gained more (P < 0.001) than those fed CSM (0.42 vs 0.26 +/- 0.034 kg/d). Calves fed FM vs CSM had a greater increase (P < 0.05) in hip height (3.3 vs 2.8 +/- 0.23 cm). Steers had lower (P < 0.001) serum urea nitrogen levels than heifers (15 vs 21 +/- 0.9 mg/dl). Serum glucose levels tended to be lower for steers fed CSM than FM (62 vs 73 +/- 2.2 mg/dl), but similar between heifer groups (82 +/- 2.0 mg/dl). By day 90, a higher ADF digestibility was found for heifers fed FM as compared to heifers fed CSM and steers fed CSM or FM (66 vs 56, 55, 51 +/- 2.5%). Although supplying FM improve heifer utilization of dormant tallgrass prairie, no differences were detected for subsequent 60 d gains (1.2 +/- 0.06 kg/d) or pregnancy rates (66%) when heifers were placed on spring wheat pasture. Results suggest Brangus calves can be wintered on lower quality tallgrass prairie pasture with modest levels of protein supplementation when annual cool season forages are not available.