Submitted to: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2006
Publication Date: 4/3/2006
Citation: Soder, K.J., Saporito, L.S., Stout, W.L. 2006. Effect of gypsum application level to grass pasture, grass hay, and corn silage on fermentation by rumen microorganisms in continuous culture. Animal Feed Science And Technology. 132:331-340. Interpretive Summary: Gypsum is used as a soil amendment to decrease phosphorus leaching but increases plant sulfur concentrations, potentially causing health problems in grazing ruminants from a ruminal fermentation standpoint as well as mineral imbalances. A study was designed to determine the effects of gypsum application level to corn, pasture, and hay on ruminal fermentation using continuous-culture fermenters. Ruminal fermentation was not compromised when gypsum was applied to grass pasture, grass hay, or corn silage at rates up to 90 t/ha. Implications of sulfur levels greater than the 0.40% recommended by the National Research Council in the grass hay should be investigated further at the whole-animal level. Gypsum application to pastures and crops shows promise as an economical soil amendment to increase soil pH, decrease soil acidity, thereby decreasing soil leaching of phosphorus without impairing rumen function, although implications at the whole-animal level should be evaluated.
Technical Abstract: A dual-flow continuous culture fermenter system was used to investigate ruminal fermentation in response to increased gypsum application of three forages in a completely randomized design. The treatments were: 1) 0 t/ha gypsum, 2) 22 t/ha gypsum, 3) 45 t/ha gypsum, and 4) 90 t/ha gypsum applied to grass, and 0, 22, and 45 t/ha gypsum applied to corn plots. Forage was harvested to represent grass pasture (GP), grass hay (GH), and corn silage (CS). Forage was dried and ground and fed to fermenters at 0700, 1030, 1430, and 2030 h at a rate of 60 g DM/d. Each forage was fermented in separate runs, therefore cross-forage analyses were not conducted. Digestibility of DM, OM and NDF were not affected by gypsum application rate. Rumen pH, VFA production and N metabolism were not affected by gypsum application rate. The GH had greater S content (0.44 to 0.48%) than recommended as the maximum tolerable level by the National Research Council (0.40%); further research is needed to evaluate whole-animal effects of the excess S if GH is fed as the sole feed and not diluted with other feeds. The results of this study indicate that ruminal fermentation was not compromised when gypsum was applied to GP, GH, or CS at rates up to 90 t/ha. Gypsum application to pastures and crops shows promise as an economical soil amendment to increase soil pH, decrease soil acidity, thereby decreasing soil leaching or phosphorus into ground and surface waters.