224 Comparing the in vitro fermentation characteristics of ruminal and cecal contents from feedlot cattle

Abstract

The objective was to compare the in vitro fermentation characteristics of ruminal and cecal contents from feedlot cattle after slaughter. Evaluating ruminal and cecal fermentation can further develop an understanding of nutrient digestibility and microbial activity that are critical to cattle health and nutrition. Historically, ruminal fermentation has been studied more in depth compared with the cecum. Ruminal and cecal contents were collected from eight cattle within thirty minutes of slaughter at the University of Illinois Meat Science Laboratory. Ruminal and cecal contents were strained through two layers of cheesecloth and stored in a pre-warmed thermos for transportation to the laboratory. Four flasks (2 ruminal and 2 cecal) for each animal contained 1.5 g DM substrate (70% dry corn, 15% corn silage, and 15% modified wet distillers grains with solubles) and 150 mL of inoculum (2 McDougall’s buffer: 1 fluid ratio). Four sealed F57 Ankom bags containing 0.25 g DM substrate were added to an individual flask to measure in vitro dry matter disappearance (IVDMD). Flasks were placed in a 39°C water bath to stimulate the ruminal environment for 30 hours. Sample aliquots were collected at hours 0, 4, 8, 16, and 30 to determine pH, volatile fatty acids, and ammonia. Data were analyzed using the MIXED procedure of SAS 9.4. No interactions between collection site and time were observed (P > 0.10). There were no differences between ruminal and cecal pH (P = 0.15); however, there was a time effect (P < 0.01) as pH peaked at hour 4 and then decreased over time. Ammonia levels of cecal contents were greater (P < 0.01) compared with ruminal contents. Ammonia levels also increased (P < 0.01) over time. A greater IVDMD was observed (P < 0.01) for the ruminal contents compared with cecal contents (55.0 versus 51.7%, respectively). Cecal contents had a greater (P < 0.01) concentration of total volatile fatty acids, a greater (P < 0.01) molar proportion of acetate, a lesser (P < 0.01) molar proportion of propionate, and a greater (P < 0.01) molar proportion of butyrate. In conclusion, there were important differences observed in the in vitro fermentation characteristics of ruminal and cecal contents from feedlot cattle collected after slaughter.