106407 Nutrient Cycling through Livestock Excreta in N-Fertilized or Grass-Legume Pastures.
Poster Number 404
Wednesday, October 25, 2017
Tampa Convention Center, East Exhibit Hall
The objective was to assess nutrient cycling by measuring total fecal output in cattle grazing three forage systems. The experiment was conducted from January to October 2016 in a grazing trial at the University of Florida, North Florida Research and Education Center. Treatments consisted of three forage systems as follows: 1) N-fertilized bahiagrass (Paspalum notatum Flügge) pastures (113 kg N ha-1) during the warm season, overseeded with a mixture (45 kg ha-1 of each) of ‘FL 401’ cereal rye (Secale cereale L.) and ‘RAM’ oat (Avena sativa L.) during the cool season (BHF); 2) rhizoma peanut (Arachis glabrata Benth.)-bahiagrass pastures during the warm season, overseeded with the rye-oat mixture fertilized with 34 kg N ha-1 plus a mixture of clovers (Trifolium sp.) during the cool season (BHR); and 3) unfertilized bahiagrass pastures during the warm season, overseeded with the rye-oat-clover mixture + 34 kg N ha-1 during the cool season (BH). Dry matter intake (DMI) was determined by measuring total fecal output with the marker dilution technique (Cr2O3 and TiO2 as markers) and in vitro digestibility from composited hand-plucked samples from each pasture during the days of marker dosing. Cattle DMI, either as kg hd-1 d-1 or as percentage of body weight, did not differ (P > 0.10) among treatments in either the cool or the warm season. Fecal OM output was similar across treatments in the cool season (P = 0.14). In the warm season, BHR steers had decreased (P < 0.05) fecal OM output when compared to BHF (1.80 vs. 2.8 kg hd-1 d-1). Excretion of P, K, Ca, and Mg was similar across treatments in both seasons (P > 0.10). In conclusion, similar intake and decreased fecal output in BHR may indicate a greater digestibility of legume-containing pastures in the warm season when rhizoma peanut is present.