Effects of Direct-Fed Microbials on Feed Intake, Milk Yield, Milk Composition, Feed Conversion, and Health Condition of Dairy Cows

Direct-fed microbials (DFMs) are dietary supplementations for ruminants that alter rumen fermentation, improve the microbe balance, and limit nutritional disorders such as subacute ruminal acidosis. Many microorganisms may be fed as DFMs including Lactobacillus, Bifidobacterium, Enterococcus, Streptococcus, Bacillus, Saccharomyces, Aspergillus, and Propionibacterium. To further understand the mechanisms of microorganisms, species can further be split into subgroups based on mode of action within the rumen and if traditionally found within the rumen or outside, which include: lactic acid producing, lactic acid utilizing, fungi, yeast, and bacterial spores. Including DFMs in the diets of calves and dairy cows has been reported to positively influence animal performance, milk components, feed conversion, reduction in methane emission, improvements in general animal and human health, reductions in nutritional disorders, and stimulation of the immune system. While initially inclusion of DFMs in the diet may be monetary cost preventative for some herds, the possible return on investment of feeding one or more microorganisms to dairy cows is beneficial for both the producer and the animal, helping to recover the inclusion cost and improve animal health. Within this chapter, recent research studies will highlight the great potential benefit of adding DFMs into the diet.