Submitted to: Animal Feed Science And Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/9/2014
Publication Date: 3/4/2014
Publication URL: http://handle.nal.usda.gov/10113/58534
Citation: McMurphy, C.P., Sexten, A.J., Mourer, G.L., Sharman, E.D., Trojan, S.J., Rincker, M.J., Coblentz, W.K., Lalman, D.L. 2014. Effects of including saponins (Micro-aid®) on intake, rumen fermentation, and digestibility in steers fed low-quality prairie hay. Animal Feed Science And Technology. 190:47-58. Interpretive Summary: It is a common practice to supply additional protein to cattle consuming low-quality forage and this practice is thought to be effective when the crude protein content of forage is less than 7%. In the Southern Great Plains, standing native range pastures reach this crude protein minimum during late July. Supplying additional protein to cattle has resulted in improvements in intake and digestibility but rising costs of supplemental protein, and an environmental policy that encourages the reduction of greenhouse gases in animal production systems, has led to more research designed to improve supplementation efficiency. Saponins are believed to reduce ruminal protozoa which may improve ruminal protein conservation, decrease production of methane, and shift production of ruminal fatty acids towards propionate, all of which improve overall animal efficiency. Micro-Aid® is a saponin extract derived from the yucca plant. In two experiments steers were offered a low-quality prairie hay, with or without protein supplements. Micro-Aid® was added at two rates to fortify the protein supplement. Protein supplementation to cattle consuming low-quality prairie hay improved hay intake and digestibility, as well as nitrogen balance. The inclusion of Micro-Aid® in the protein supplement improved ruminal dry matter and fiber digestibility by decreasing the rate that particles flow through the rumen, but it was not successful at improving total digestibilities throughout the entire digestive tract. This saponin product successfully altered rumen fermentation and suppressed protozoa numbers, which might prove to be beneficial to those ruminants with greater protein requirements. However, more research is needed to determine its effects on animal performance.
Technical Abstract: Sixteen ruminally-cannulated crossbred steers (529 ± 45 kg initial body weight, BW) were used to evaluate in situ dry matter (DM), neutral detergent fiber (aNDF), and N degradation characteristics of low quality prairie hay, blood urea nitrogen (BUN) and rumen fermentation parameters in steers provided a protein supplement with or without Micro-Aid® (MA; plant derived saponin). Steers were allowed ad libitum access to chopped prairie hay (49 g crude protein (CP)/kg DM and 738 g aNDF/kg DM) and randomly assigned to one of four treatments : 1) no supplement (C), 2) cottonseed meal and wheat middlings: 920 g DM/d (PC; positive control), 3) MA added to PC to supply 1 g MA/d (MA1), and 4) MA added to PC to supply 2 g MA/d (MA2). Steers were individually supplemented 920 g DM once daily at 08:00 along with a vitamin and mineral mix to ensure requirements were met. Orthogonal contrasts were used to determine the effects of protein supplementation, addition of MA and level of MA inclusion. During in situ phase, forage samples were incubated for a 96 h period. Protein supplementation increased DM intake (DMI), particulate passage rate (Kp), and rumen digestibility of DM and NDF (P<0.001), but there was no effect on rumen nitrogen degradability. The inclusion of MA did not impact DMI in either phase. Compared to PC, MA decreased Kp (27.8 and 22.7 g DM/kg/h, respectively; P=0.02), resulting in an increase in rumen aNDF and DM digestibility (P<0.001). However, there was no influence of MA on apparent total tract digestibility in the metabolism phase. Rumen protozoa concentrations were suppressed (P=0.01) with MA inclusion while lactate concentrations and microbial crude protein (MCP) flow to the small intestine were increased (P=0.05). There was no impact on BUN, rumen ammonia, pH, volatile fatty acid (VFA) concentrations or nitrogen balance for MA compared to PC diets. Supplementation improved nitrogen balance, MCP synthesis and increased total concentrations of VFA and independent acetate and propionate concentrations. In conclusion, including MA in protein supplements increased rumen DM and NDF digestibility of forage, reduced protozoa concentrations and increased daily outflow of MCP. This is indicative of increased rumen fermentation rate and may ultimately impact animal performance via increased energy and amino acid supply to the small intestine. However, more research is needed to validate this potential impact on animal performance.