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Abstract
Interseeding alfalfa (Medicago sativa) into bermudagrass (Cynodon spp.) can offset nitrogen fertilization requirements, improve forage quality, extend bermudagrass grazing days, and increase economic returns. Previous research demonstrated an optimal harvest management strategy, cut-and-graze, produces high quality stored feed and has potential to fill a regional grazeable forage deficit during the summer to fall transition. The objectives of this research were to evaluate three- and four-year-old alfalfa-bermudagrass (ABG) mixtures under a cut-and-graze harvest management system to: 1) evaluate if preservative and inoculant application would improve ABG baleage nutritive value, 2) evaluate stocker calf and forage performance during the summer to fall forage transition when rotationally grazing two bermudagrass cultivars (Russell and Tifton-85) interseeded with alfalfa as part of a strategic management system, 3) evaluate in vitro mixed ruminal microorganisms fermentation parameters when a microbial-based forage preservative was applied at mowing in ABG mixtures harvested as baleage. Forage preservative and inoculant application did not improve forage nutritive value; however, the ABG baleage had over 200 g·kg-1 crude protein and 630 g·kg-1 total digestible nutrients. ABG mixtures were grazed for 57 and 62 days during the summer to fall forage transition (September to November) and supported stocker calf average daily gains from 0.4 to 1.2 kg·hd-1·day-1. Higher overall animal and system performance attained during grazing in 2023 suggests that targeting 28 to 35 days of rest between the previous baleage harvest and grazing initiation would increase forage quality and animal gains. The addition of microbial-based forage preservative at mowing did not improve ruminal fermentation for ABG mixtures when evaluated in vitro. Ruminal fermentation parameters primarily differed between forage type (sampled pre-ensiling or post-ensiling). These evaluations demonstrate that ABG mixtures are productive into the third and fourth year after alfalfa establishment. Harvesting ABG as baleage allows producers to harvest their own stored feed resource, but the application of forage preservatives and/or inoculants may not improve nutritive value or ruminal fermentation. Additionally, ABG mixtures, under cut-and-graze management, have potential to fill the summer to fall forage transition with a high-quality grazeable forage.