Nitrogen fertilization is a major input cost of forage production, and alternatives that maintain yield and nutritive value would be advantageous. A 3‐yr study was conducted to evaluate forage nutritive value and clover proportion when N fertilizer was replaced partially with interseeded clovers (Trifolium spp.) or protein supplements for stocker cattle grazing annual ryegrass (Lolium multiflorum Lam.). Nitrogen delivery methods with or without monensin included annual ryegrass fertilized with 112 kg N ha−1 in split application (NFERT), and other methods that received 56 kg N ha−1, including annual ryegrass interseeded with crimson clover (CC, Trifolium incarnatum L.) or arrowleaf clover (AC, Trifolium vesiculosum Savi), or grazing cattle supplemented with distillers dried grains plus solubles at a rate of 0.65% body weight daily (DDGS) or whole cottonseed (Gossypium hirsutum L.) at the rate of 0.65% body weight daily (WCS). Clover proportion was greater (P = 0.003) for CC than AC across all 3 yr of the study, and CC was more (P = 0.003) abundant when monensin was fed. Year affected forage in vitro true digestibility (IVTD, P < 0.001) and crude protein (CP, P < 0.001) concentration such that IVTD and CP were greatest in Year 3, intermediate in Year 2, and least in Year 1. Forage degradable intake protein (DIP) concentration was affected by N delivery method (P < 0.001) and year (P < 0.001) such that CC was less than NFERT, DDGS, WCS, and AC, and Year 1 was greatest, Year 2 was intermediate, and Year 3 was the least. Results are interpreted to mean that year affected forage nutritive value more than did N delivery method.

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A 2-yr grazing experiment was conducted to evaluate efficacy of nitrogen (N) fertilization, interseeded legumes and protein supplementation for N delivery to stocker cattle grazing annual ryegrass (Lolium multiflorum). Each yr, 90 steers (initial BW, 241 ± 13 kg) were assigned to the following N-delivery methods, with or without monensin fed in a free-choice mineral supplement as a 5 x 2 factorial arrangement of treatments: 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 distillers dried grains with solubles (DDGS) supplemented at 0.65% BW daily; and ryegrass plus whole cottonseed (WCS) supplemented at 0.65% BW daily. Pastures within the interseeded-clover and protein-supplementation treatments were fertilized with 56 kg N/ha at time of establishment. Steers were weighed every 28 d, and forage mass (FM, kg DM/ha) was measured concurrently using the destructive harvest/disk meter double-sampling method. Each of 30 0.81-ha paddocks was stocked initially with 3 ‘tester’ steers, and stocking density (steers/ha) was adjusted using ‘put-and-take steers’ based on changes in FM and steer BW in order to maintain a uniform forage allowance (FA) of 1 kg DM/kg steer BW. Grazing was discontinued on May 11, 2016 in Yr 1 and May 10, 2017 in Yr 2 following 140 and 84 d of grazing, respectively. Data were analyzed as a completely randomized design with repeated measures for which pasture (n = 3) was the experimental unit. Ionophore inclusion did not affect (P &gt; 0.10) any variable measured. Mean FM differed (P &lt; 0.0001) between yr and among N-delivery methods (P &lt; 0.10), and mean FA differed (P = 0.005) among N-delivery methods. Steer ADG differed among N-delivery methods (P = 0.02) and between yr (P &lt; 0.001), whereas total gain/ha differed (P &lt; 0.0008) among N-delivery methods, but not between yr (P = 0.78). Stocking density differed among N-delivery methods (P = 0.02) and between yr (P &lt; 0.0001), and grazing-days/ha differed between yr (P &lt; 0.0001) and among N-delivery methods (P = 0.001). Results indicate that supplementation with a high-protein by-product feed for cattle grazing annual ryegrass maintained ADG, total gain/ha and grazing-days/ha compared with N-fertilized annual ryegrass, and increased ADG, total gain/ha and grazing-days over interseeded legumes.