The negative impacts of fescue toxicosis caused by a fungal endophyte are well documented. Signs of toxicosis induced by fescue include rough hair coats; elevated body temperatures; severe heat stress; and a reduced prolactin hormone concentration, which reduces milk yield from nursing cows.
The consumption of the ergot alkaloids produced by the fungal endophyte reduce dry matter intake of grazing cattle resulting in lower average daily gains (ADG) for weaned calves. For this reason, profitable stocker cattle gains are challenging on pure fescue pastures.
Glen Aiken, research animal scientist at the USDA-ARS Forage-Animal Production Research Unit in Louisville, Ky., notes that technologies have been developed to help overcome or moderate the impacts of fescue toxicosis. These include planting novel nontoxic endophyte varieties, overseeding legumes to help dilute the ergot alkaloids in the diet, using chemical seedhead suppression, and the supplementation of feed by-products.
Aiken and his coworkers conducted a two-year grazing study with crossbred steers to evaluate the effects of feeding soybean hulls (SBH) in combination with fescue pastures. The 500-pound steers were subject to the following treatments:
2. Ear implanted with an estradiol-progesterone implant
3. Ear implanted and fed 5 pounds of SBH per head per day
4. No implant or feeding of SBH (control)
Steers receiving the implant-only treatment gained 1.78 pounds per steer per day, 12 percent better than the control animals. The steers given only SBH had an ADG of 2.09 pounds, 31 percent greater than the control steers. Animals that received both the implant and SBH gained 2.71 pounds per steer per day. This was 70 percent greater than the control animals.
In summarizing the study, Aiken says, "The implant-only treatment increased ADG without reducing the severity of toxicosis, but the SBH treatment, with and without implantation, had two-times greater prolactin concentrations and a higher percentage of sleek hair coats than those on the control treatment."
The researcher noted that the increased cost for steers receiving the combined implant and SBH were below the break-even cost over a wide range of SBH costs and cattle markets.