Effect of Maturity at Harvest of Small Grain Grasses on the Nutritional Composition of Forage and Ration Formulation.

Abstract

We hypothesized that, relative to harvesting small grain grasses at the soft-dough stage (SDS) of maturity, harvesting small grain grasses at the boot stage (BS) of maturity would result in cheaper dairy rations when commodities' prices are high but not when commodities' prices are low. Small plots of small grains were planted during the fall of 2020 and 2021 in Blacksburg, Blackstone, and Orange, Virginia. In each year and location, 2 varieties of barley, 2 varieties of rye, and 4 varieties of triticale were planted in plots replicated 6 times, yielding 288 plots. Within each year and location, we harvested half of the plots at the BS of maturity and the other half at the SDS of maturity. For each of the 6 small grain grasses, we formulated 8 rations according to 8 different scenarios using the least-cost optimizer. The scenarios included high and low commodities' prices, high and low dietary forage (60 and 40% forage, respectively), and the inclusion of small grain grasses harvested at the BS or SDS of maturity. Harvesting at the SDS of maturity yielded 107% to 205% more DM than harvesting at the BS of maturity. Relative to BS, small grain grasses harvested at the SDS of maturity had greater concentrations of OM, NDF, ADF, ADL, and starch but lower concentrations of CP. Relative to BS, small grain grasses harvested at the SDS of maturity also had a greater concentration of uNDF (NDF basis). Species had minimal impact on the nutritional quality of small grain grasses for silage. Under a low-price scenario, the ration formulation system ignored all 6 small grain grass silages and included corn silage as the only forage source when we did not limit its inclusion. Under a high-price scenario, the ration formulation system included all 6 small grain grass silages when formulating low-forage diets with unlimited corn silage. However, a preference between BS and SDS stages did not exist with the optimizer not consistently selecting a specific maturity stage. After evaluating the yields, the chemical composition, and the impacts on ration formulation in this study, future studies should aim to evaluate the impact of maturity at harvest of small grain grasses on cow performance and environmental impacts.