ANSC Feeds Practice Exam

What happens to acetic acid concentrations as grain proportion in a diet decreases?

1. They remain unchanged

2. They increase

3. They decrease

4. They fluctuate unpredictably

The correct answer is: They increase

When the proportion of grain in a diet decreases, the concentration of acetic acid typically decreases as well. Grains are rich in fermentable carbohydrates that are broken down by gut microbes into various short-chain fatty acids, including acetic acid. As the amount of grain decreases, there is less fermentable substrate available for microbial fermentation, resulting in lower production of acetic acid. The fermentation process that produces acetic acid is largely driven by the availability of carbohydrates that can be easily fermented. In diets with a higher grain proportion, high levels of fermentable carbohydrates encourage a robust fermentation process, leading to increased acetic acid concentrations. Conversely, when the grain content is reduced, the overall fermentable carbohydrate content drops, which in turn reduces acetic acid production. In summary, the decrease in grain proportion leads to a reduced substrate for fermentation, contributing to lower acetic acid levels in the diet. This relationship is important in animal nutrition, especially when formulating diets for livestock, as it impacts energy metabolism and overall health.