Volatile fatty acids are produced by fermentation primarily of which type of substrate?

Volatile fatty acids (VFAs) are primarily produced through the fermentation of carbohydrates, with cellulose being a significant contributor among the various types of substrates. Cellulose is a complex carbohydrate found in the cell walls of plants, and it is not easily digestible by many animals. However, certain microorganisms, particularly those found in the gastrointestinal tracts of herbivores, have the ability to break down cellulose through fermentation. This process results in the production of VFAs, such as acetate, propionate, and butyrate, which serve as an essential energy source for ruminants and play various roles in metabolism.

Fats, while they can be metabolized for energy, are not the primary substrate for VFA production through fermentation. Similarly, minerals do not undergo fermentation and do not contribute to VFA production. Proteins can also be broken down and fermented, leading to different end products, but the production of VFAs is more closely associated with the fermentation of carbohydrates, particularly cellulose. Thus, cellulose stands out as the correct answer, emphasizing its vital role in the production of volatile fatty acids in various animal species, especially those that rely on fermentative digestion.