Effect of steroidal sapogenins on ruminal fermentation and on production of lactating dairy cows.

Supplementation of dairy rations with steroidal sapogenins was evaluated in an in vitro, an in situ, and a production trial. Sixteen in vitro semicontinuous rumen cultures were supplied a 55:45 concentrate to roughage substrate with Sarsaponin concentrations of 0, 33, 55, and 77 ppm of air-dry feed for 22 d. Supplementation decreased protozoa numbers and increased bacterial numbers and acid detergent fiber digestion. Digestion of feed nitrogen tended to be lowest at the highest concentration of Sarsaponin, whereas microbial nitrogen output was similar for all concentrations. In rumen-cannulated animals fed a typical dairy ration, in situ rate of disappearance of organic matter, acid detergent fiber, and nitrogen of a complete ration substrate tended to be lower with 77 ppm added Sarsaponin. In a production trial, 16 primiparous dairy cows 6 to 10 wk postpartum were fed rations containing either 0 or 77 ppm Sarsaponin. Sarsaponin did not alter dry matter intake, digestibility, body weight change, or milk production and composition. Supplementation had no significant effect on ruminal fermentation in vivo as reflected by concentrations of ruminal ammonia nitrogen, blood urea, or molar ratios and concentrations of ruminal volatile fatty acids.