The effect of micronutrients on rumen fermentation and microbial diversity has been studied by previous studies focusing on macronutrients. However, Penn State University and Ohio State University have studied the effects of micronutrients on microbial fermentation.
The Penn State University study found that VFA production was increased when organic trace minerals (protein salts and yeast) were added to the back-up cattle diet compared with sulfate. The Ohio State University study found that adding hydroxy minerals to Dairy Cattle Diets increased NDF digestibility compared to sulfate. The mechanism behind these results is not clear, but rumen microorganisms need trace minerals.
However, in vitro studies have shown that supplementation of trace minerals from sulfate sources is toxic to microbial flora, especially cellulolytic bacteria. Protein acid salts or hydroxyl minerals are more easily digested and utilized by microorganisms, thus increasing their growth and reproduction. However, protein salts or hydroxyl minerals can reduce the concentration of soluble minerals in the rumen and their interaction with rumen microorganisms.
Other non nutritive factors affecting rumen microbial fermentation included feed particle size, picky eating and overeating. The decrease of feed particle size can increase the attached surface area of microorganism and improve rumen fermentation. However, as mentioned earlier, smaller particle size reduces the residence time of feed in the rumen and inhibits fermentation. Picky or binge feeding can lead to sharp fluctuation of rumen pH value and change microbial activity, growth and reproduction. It is important to balance fiber and carbohydrate content to maximize microbial fermentation and cow performance.