Adding direct-fed microbials to milk or milk replacer may support calf intestinal integrity and overall health. Most research has reported little effect of direct-fed microbials on animal growth or feed efficiency. Rather, improved intestinal bacterial flora may reduce the risk of diarrhea, particularly when animals are exposed to significant immunological, environmental or other stressors.

The Bovine Alliance on Management & Nutrition (BAMN) has a new publication on direct-fed microbials. Read the full publication here.

BAMN considerations for using direct-fed microbials in calves:

  • Strain selection. Most published research has been conducted with well defined individual strains or limited combinations of bacteria. Most modern direct-fed microbial products are combinations of several bacteria, and sometimes yeast, which make it difficult to determine what organism, if any, contributes to an improved response. Further, different strains of specific organisms (e.g., Lactobacillus acidophilus) may respond differently to other strains in the intestinal environment. Companies marketing direct-fed microbial products should research specific organism(s) in the product.
  • Storage. All direct-fed microbial products contain living organisms. Therefore, the manner in which products are manufactured, shipped, stored, and handled is very important. Conditions that can kill direct-fed microbials include storage for long periods, high temperatures, low temperatures, direct sun, high humidity, oxygen, presence of mineral premixes, and others. Over time, organisms will die and product effectiveness will be lost. Be sure to follow the manufacturer’s recommendations for storing direct-fed microbial products. Many commercial laboratories test for total counts of viable organisms; however, monitoring growth of specific species of bacteria is more difficult.
  • Water. Chlorination, temperature and mineral content of water may affect viability of direct-fed microbials.
  • Mixing with milk replacer. Be sure to follow the manufacturer’s recommendations on including in milk replacer, since high water temperatures used with some milk-replacer formulations (particularly those used in the veal industry) may kill some direct-fed microbial products.
  • Antimicrobials. Antimicrobials in milk replacer or waste milk may interfere with the action of direct-fed microbial products. In addition, use of ionophores (Bovatec® or Rumensin®) may interfere with the action of some direct-fed microbial products.
  • Pasteurization. All direct-fed microbial products should be added to waste milk only after pasteurization and after the milk has cooled to feeding temperature.
  • Quality assurance. It is difficult to determine whether or not the bacterial products you are purchasing are viable (alive). Private laboratories conduct total-plate counts for bacteria and yeast/molds, which may not accurately reflect viable bacteria counts. Many direct-fed microbial products contain several types of organisms, some of which are more sensitive to storage conditions than others. Therefore, it is difficult to determine which organisms are alive in a sample of direct-fed microbials tested for total cell counts.
  • Cost Benefit. Since there is wide variation in the cost of direct-fed microbials, a cost-benefit analysis is recommended when deciding to introduce direct-fed microbials as a feed additive.