Effects of Urea and Isoacids on in vitro Fermentation of Diets Containing Formaldehyde-Treated or Untreated Soybean Meal

Effects on microbial fermentation were determined when buffer containing urea, branched-chain volatile fatty acids, a combination of these infusates or buffer only was infused into fermenters fed diets containing soybean meal treated with .3% formaldehyde or untreated. Fermentations were conducted at a solids retention time of 16 h and a liquid dilution rate of 12%/h. When buffer only was infused, the diet containing formaldehyde-treated soybean meal depressed digestibilities of NDF and ADF and fat-free organic matter compared with diets containing untreated soybean meal. In cultures fed treated soybean meal, digestibilities were partially restored by either infusion of urea or branched-chain acids and were increased to control levels by the combined infusates. Nitrogen digestion (35 vs. 69%) and microbial protein production (1.27 vs. 1.60 g/d) were depressed in fermenters fed the treated soybean meal, and neither was improved by the infusions. The data suggest microbial growth 5 have been impaired by a wide ratio of nonstructural carbohydrate to degradable protein when the formaldehyde-treated protein was fed.