Mitigating Forage Shortage due to Seasonal Yield Distribution
There is no single all-season forage resource that supplies year-round grazing to livestock. In Missouri we are fortunate to be in a climatic zone where we can produce both warm and cool season species. The majority of our forage-livestock systems are dominated by a cool-season grass, tall fescue, that produces 2/3 of its annual growth during the spring and 1/3 during the fall. Tall fescue forage production and nutritive value are poor during summer months, resulting in a forage shortage from July-September. Using warm-season species can mitigate forage shortages due to the decline of cool season tall fescue during summer.
I seek to identify a novel warm season legume to provide increased nutritive value and yield in fescue-based forage production systems. The tropical legume sunn hemp grows to heights of 6 feet or more in as few as 60 days. My research suggests sunn hemp to be a highly productive forage crop with excellent nutritive value that complements tall fescue-based systems.
I have determined that yield and nutritive value were optimized when sunn hemp is harvested between 35 and 45 days after planting and when harvested again following 21 days of regrowth. I have also researched interseeding sunn hemp directly into tall fescue pasture and have determined that sunn hemp can be planted directly into tall fescue following stand suppression by grazing with no compromise to yield or nutritive value.
Leaf and stem maturity also impact sunn hemp yield and nutritive value. Nutritive value of leaves is greater than that of stems and both decrease with maturity. However, fiber digestibility of stems remains unexpectedly high at each stage of maturity evaluated.
Understanding how sunn hemp performs in a tall fescue grazing system is vital to its success and adoption. I am currently studying the contribution of nitrogen fixation, yield and nutritive value by sunn hemp to tall fescue-based grazing systems. To date, I have observed that growing cattle gained 1.7 lbs. per day from July to October on tall fescue interseeded with sunn hemp.
Using stored forages (hay and silage) to mitigate forage shortage during winter is important to feeding livestock in Missouri. We evaluated sunn hemp baleage as a winter feed for growing steers and determined that sunn hemp is also a viable option for winter feeding.
Using native and introduced warm-season grasses in tall fescue-based systems is also promising. A concern in our systems is lack of cold tolerance of introduced species. I am studying the role of saturated and unsaturated fatty acids in bermudagrass genotypes selected for forage yield and nutritive value and have observed that long- and very-long-chain saturated fatty acids, as well as the polyunsaturated fatty acids C18:3n3 and C20:5n3 are important factors contributing to thermal acclimation in forage bermudagrass. This work led to collaboration between MU and Florida to determine the variation in thermal sensitivity and tolerance of bermudagrass grown across a climatic gradient and to determine the role of fatty acid and non-fatty acid lipid compounds in bermudagrass thermal acclimation.
Native warm-season grasses (NWSG) provide numerous ecosystem services, some of which include forage for livestock and pollinator and wildlife habitat. However, NWSG are challenging to establish. In addition, little is known about managing NWSG as part of cool season forage-livestock systems. I have begun researching 1) NWSG as part of tall fescue rotational grazing systems, 2) proper management of NWSG for hay production, and 3) establishment and persistence of NWSG in silvopasture systems. Results from this research will provide forage-livestock producers with valuable information related to expanding their forage resource throughout the grazing season.
Missouri currently ranks among the leading beef cow-calf producing states. My research in this area has expanded forage crop options and led to proper management prescriptions for extending the grazing season through the summer months, when our cool-season pastures lack productivity and nutritive value.