Folate metabolism and application of folic acid in ruminant production

Folic acid, also known as vitamin B9, is a water-soluble vitamin from the B group that plays a pivotal role (as the carrier of one-carbon units) in the regulation of early development and nutrient metabolism in animals. Traditional animal nutrition posits that rumen microorganisms can synthesize folate, thereby meeting the growth, development, and production needs of ruminants. However, the quantity of synthesized folate is subject to variations in dietary composition, genetic enhancements, increased production performance, and changes in feeding systems. These factors may result in the folate synthesized by rumen microorganisms not reaching the optimal production potential of the animals. Despite a significant proportion of dietary folic acid/folate being degraded in the rumen, studies have shown that supplementing folic acid (or combined with vitamin B12, methionine, etc.) in the diet can enhance rumen fermentation, increase the folate level in ruminant tissues (such as the liver and blood), regulate nutrient metabolism, and improve milk yield and quality to a certain extent. Further research is required to assess the impact of dietary folic acid levels on rumen microbial metabolism, folate distribution among different tissues and organs, and the demand for folate at various developmental stages, as well as the interaction between folic acid and other nutrients which are involved in one-carbon metabolism process. This will help to optimize the nutritional supply for ruminants and fully exploit their production performance potential.