292 Study on the seasonal changes in average daily gain, feed value, forage productivity, and grazing intensity in native pasture grazed by Korean native goat (Capra hircus coreanae)

Abstract

Forage ephedra (Ephedra nevadensis; ephedra) is well adapted and grazed by sheep and cattle in the Western United States; however, its nutritional value has not been well established. The objective of this study was to determine ruminal digesti-bility, ruminal microbial fermentation, and bacterial N synthesis of ephedra as compared with cheatgrass (Bromus tectorum; CG) and orchardgrass hay (Dactylis glomerata L.; OGH). Diets were randomly assigned to 6 fermenters in a dual-flow continuous culture system in a 3 × 3 Latin square design with three 10-d experimental periods consisted of 7 d for diet adaptation and 3 d for sample collection. Fermenters were fed a total of 72 g of DM/d equally divided into 2 portions per day. Diets were 1) 100% air-dried ephedra, 2) 100% air-dried CG, and 3) 100% air-dried OGH. Liquid and solid dilution rates were adjusted daily to 10 and 5%/h, respectively. A 500-mL sample was taken on 8, 9, and 10 d and analyzed for nutrient digesti-bility and microbial growth. Two 10-mL subsamples were filtered through 2 layers of cheesecloth and preserved with 0.2 mL of 50% sulfuric acid and 2 mL of metaphosphoric acid for subsequent ruminal NH 3-N and VFA analyses, respectively. Statistical analysis was performed using PROC GLIMMIX of SAS. Partial data are presented in Table 293. The NH 3-N concentration was greater for CG followed by ephedra and lowest for OGH (P < 0.01). Ruminal pH was greater for ephe-dra (P < 0.01), whereas total VFA was the lowest (P < 0.01). Ephedra had greater acetate molar proportion, which resulted in the greatest acetate:propionate ratio (P < 0.01). Ephedra also had the lowest propionate molar proportion. Results from this study indicate that ephedra should not be used as the main forage in cattle diets due to its poor fermentation as evidenced by the lowest total VFA and propionate molar proportion.