Effect of Replacement of Soybean meal by Dried Tomato Pomace on Rumen Fermentation and Nitrogen Metabolism in Beef Cattle

Problem statement: Dried tomato pomace may be considered as an alternative feedstuff in ruminant nutrition. The limited literature data that are available so far may be interpreted as indirect and suggestive evidence for diminished ruminal fermentation and bacterial synthesis after substitution of dried tomato pomace for soybean meal. Approach: Rumen-fistulated beef steers were used to address the questions whether the replacement of soybean meal by dried tomato pomace would affect feed intake, rumen fermentation and nitrogen metabolism. In a feeding trial with Latin-square design, the steers were fed total mixed rations containing either 3.2, 8.0 or 11.2% dried tomato pomace. Results: The replacement of dietary soybean meal by dried tomato pomace did not affect feed intake, but was found to change various indices of rumen fermentation. Increasing intakes of dried tomato pomace caused increasing ruminal pH values and ammonia concentrations in a dose-dependent fashion, but concentrations of volatile fatty acids and number of ruminal bacteria were left unchanged. Higher dietary inclusion levels of tomato pomace produced a linear, dose-related increase in blood urea concentrations. Apparent, total gastro-intestinal tract digestibilities of neutral and acid-detergent fiber were not influenced by tomato pomace. The feeding of tomato pomace raised fecal nitrogen excretion and lowered urinary nitrogen excretion. Conclusion: Substitution of tomato pomace for soybean meal influences rumen fermentation and nitrogen metabolism in beef cattle, but the impact on practical ruminant production cannot yet be assessed.