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Effects of Mefluidide Treatment, Nitrogen Fertilization and Tall Fescue Variety on Nutrient Metabolism by Growing Sheep Fed Fall-Harvested Silages

U.S. Department of Agriculture^,4, Beltsville, MD 20705 and University of Maryland, College Park 20742

Abstract

The objective was to evaluate effects of mefluidide treatment, N fertilization and tall fescue variety on silage composition and nutrient use by growing wethers. Kenhy and Gl-306 tall fescue varieties were not treated or treated with mefluidide (a plant growth regulator) and fertilized with either 56 or 168 kg of N/ha on September 1. Gl-306 is an experimental line of tall fescue that has a high concentration of the alkaloid perloline. Accumulated herbages were direct-cut harvested on October 29, ensiled in duplicate silos and fed to 16 growing Suffolk x Rambouillet wethers in digestion trials in a completely randomized, single crossover design. Treatment with mefluidide reduced (P<.01) silage neutral detergent fiber, acid detergent fiber and cellulose compared with nontreated silage. Silage dry matter was lower, and total N and insoluble N higher (P<.1), with high N fertilization than with low N fertilization. Gl-306 silage was higher (P<.1) in insoluble N than Kenhy. Mefluidide treatment decreased (P<.1) silo recovery of gross energy, neutral detergent fiber and acid detergent fiber. Daily dry matter intake did not vary due to mefluidide treatment, N fertilization or variety and averaged 68.2 g/kg_.75. Silage dry matter and energy digestibilities were higher (P<.05) for mefluidide-treated silages than nontreated silages. Mefluidide treatment of Gl-306 resulted in increased urinary N and decreased N retention. Mefluidide treatment of Kenhy resulted in reduced urinary N and increased N retention. Spring-applied mefluidide treatment of fescue resulted in increased dry matter digestibility of fall-harvested silage, but reduced silo recoveries of dry matter and energy. The data are interpreted to indicate that, in spite of improved silage quality, spring application of mefluidide to temperate grasses harvested for silage in the fall may not be warranted.

¹ Research Animal Scientist, USDA, Agr. Res. Serv., Beltsville Agr. Res. Center, Anim. Sci. Insti., Ruminant Nutr. Lab., Beltsville, MD.

² The authors appreciate the contributions of J. Clary for his help in herbage preparation; L. Colbert for his excellent coordination and conduct of the ensiling, metabolism and laboratory work; J. Smiley for her able laboratory work and C. Hanna for typing this manuscript.

³ Associate Professor, Dept. of Agron., Univ. of Maryland, College Park.

⁴ Agric. Res. Serv. Mention of a trade name, proprietary product or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply its approval to the exclusion of other products that may be suitable.