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P. A. Gunter, R. W. Peacock, R. B. Muntifering, M. K. Mullenix, 052 Evaluation of Nitrogen Delivery Methods for Stocker Cattle Grazing Annual Ryegrass, Journal of Animal Science, Volume 95, Issue suppl_1, December 2016, Page 26, https://doi.org/10.2527/ssasas2017.052
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Abstract
A 140-d grazing experiment was conducted to evaluate efficacy of replacing N fertilizer with either interseeded legumes or protein supplementation for stocker cattle grazing annual ryegrass (Lolium multiflorum). Ninety steers (initial BW, 225 ± 10 kg) were assigned to the following N-delivery methods, with or without monensin fed in a free-choice mineral supplement: ryegrass fertilized with 112 kg N/ha (NFERT); ryegrass interseeded with crimson clover (CC, Trifolium incarnatum); ryegrass interseeded with arrowleaf clover (AC, Trifolium vesiculosum); ryegrass plus dried distillers grains plus solubles (DDGS) supplemented at 0.65% BW daily; and ryegrass plus whole cottonseed (WCS) supplemented at 0.65% BW daily. Steers were weighed every 28 d, and forage mass (FM) was measured concurrently using the destructive harvest/disk meter double-sampling method. Each of thirty 0.81-ha paddocks was stocked initially with 3 steers, and stocking density was adjusted using put-and-take steers based on changes in FM and steer BW in order to maintain a forage allowance (FA) of 1 kg DM/kg steer BW. Grazing was discontinued on May 11, 2016. Data were analyzed by PROC MIXED for a completely randomized design with pasture (n = 3/treatment) as the experimental unit. Overall mean FM (kg DM/ha) was greatest (P < 0.001) for NFERT (1,012), intermediate for CC (924), DDGS (964) and WCS (935), and least (P < 0.001) for AC (741). Monthly mean FM decreased (P < 0.001) from December (1,068) to March (540), and increased (P < 0.001) from April (874) to May (1,237). Average daily gain (kg/d) of DDGS-supplemented cattle (1.37) was greater than (P = 0.10) CC (1.09) and AC (1.11), and tended (P = 0.11) to be greater than NFERT (1.19) and WCS (1.20). Stocking density (steers/ha) was greater (P = 0.005) for NFERT (6.7), DDGS (6.4) and WCS (6.4) than CC (5.7) and AC (5.6). Grazing days/ha for NFERT (444), DDGS (433) and WCS (433) were greater (P < 0.01) than CC (341) and AC (329). Total gain (kg/ha) tended (P = 0.14) to be greater for DDGS-supplemented cattle (599) than NFERT (489), CC (467) and AC (426), but not WCS (516). Monensin increased (P = 0.07) total gain by 80 kg (540 vs 460 kg/ha). Results are interpreted to mean that annual ryegrass pasture supplemented with either DDGS or WCS supported ADG, stocking densities, grazing days/ha and total gain/ha that were similar to or greater than annual ryegrass amended with N fertilizer or interseeded with annual legumes.
