Impacts of rumen fluid modified by feeding Yucca schidigera to lactating dairy cows on in vitro gas production of 11 common dairy feedstuffs, as well as animal performance

The objective was to determine effects of feeding increasing levels of a Yucca schidigera extract (YSE) to dairy cows on 24h in vitro gas production and 27h in vitro neutral detergent fibre (aNDFom) digestion of 11 common dairy feedstuffs, as well as in vivo rumen fermentation and performance of the cows to which the YSE was fed. The principle was to use YSE to potentially modify the rumen microbial population in vivo and measure subsequent impacts of the adapted rumen fluid on feedstuff fermentation in vitro. Four rumen cannulated late lactation Holstein cows (810±54.7kg body weight) were used in a 4x4 Latin Square design experiment with 14d periods. Cows were housed in pens with individual feeding gates and had ad libitum access to water while fed a total mixed ration (TMR) of alfalfa hay, corn grain, barley grain, dried distillers grains, whole cottonseed, beet pulp, soybean meal, almond hulls, rumen inert fat and a mineral/salt mixture. Based upon sarsaponin assay of four commercial YSE products, Monterey Sarsaponin 15® was selected and added to the TMR to provide 0, 5, 10 or 15g of sarsaponin/cow/d. Rumen fluid from each cow in each period was utilized for in vitro gas determinations to measure gas production and aNDFom digestion from the test feeds. There was a strong linear effect (P=0.002), at an increasing rate (quadratic P=0.08), to increased extent of gas production with increased feeding of YSE. There was a quadratic effect to maximum rate of gas production (P=0.01) at the 5g sarsaponin level. At 4h of fermentation, gas production increased linearly (P<0.05), at an increasing rate (P<0.002), for almond hulls, barley grain and soybean meal with increasing levels of YSE. Gas production from barley grain had a quadratic effect (P<0.01), suggesting a maximum at about the 5g sarsaponin feeding level. Gas production at 24h of fermentation increased linearly (P=0.03), at a decreasing rate (P<0.03), but only soybean meal had a quadratic tendency (P=0.08) to minimum gas production at about the 5g level of sarsaponin. In vitro fermentation of aNDFom at 27h was not impacted by treatment. In vivo rumen pH, concentrations of total volatile fatty acids and rumen protozoal counts were not impacted by YSE feeding level, as were milk production, milk components and net energy (NE) balance. However, correlations between NE output and the proportional increases in 4h gas production with increasing levels of YSE in the diet suggest that this measure may be predictive of animal responses to this YSE. Finally, multivariate analysis, used to create equations to predict impacts of the nutrients in the 11 feedstuffs on their proportional increase in 4h gas production, suggests that the increase in 4h gas production of any feed may be predicted from its organic nutrient profile, offering the potential to determine the optimal feeding level of sarsaponin in any TMR based on its nutrient profile.