by John Hibma The author is a dairy nutrition consultant for Central Connecticut Cooperative Farmers in Hartford, Conn. He previously managed large dairies in California and Hawaii. How do you get cows to make more milk? Feed better hay? Feed them grain? Air condition the free stalls and send them on an annual visit to the hoof trimmer? Those will all work, but certainly the most important thing to remember is to get them to eat as much as possible. Dry matter intakes is still the key to high milk production, and a significant part of our focus on dairy nutrition is to get cows to digest feed as quickly and efficiently as possible. Direct-fed microbials (DFMs) and enzymes have been shown to help cows increase dry matter consumption. Direct fed microbials (also known as probiotics) are yeasts and bacteria. They, along with enzymes, have come on the feeding scene quickly in recent years and have brought with them a bit of a mystery as to how they work. The reason for using direct-fed microbials and enzymes in dairy rations is to help cows and heifers produce more milk, increase growth rates, and/or make them healthier through improved immune function. Newness brings caution . . . If you've been in the dairy industry long enough you're probably pretty comfortable with feeding hay, silages, and grains and have had enough exposure to the feed industry to understand what works and what doesn't when it comes to milk production in your herd. Direct-fed microbials and enzymes are a different story, though. They don't grow in the ground like most things we feed cows. They come in bags and boxes and in gels or liquids, and with them comes some skepticism. I recently decided to refinance my home to take advantage of lower interest rates. This is not my area of expertise, so I soon found myself in territory I don't know much about. I had to take the time to study the subject and get some professional opinions and then trust that my decision would be the right one. I've learned that's how a lot of dairy producers feel about probiotics they don't know much about them or how they work, and it's difficult to decide which ones are good or if they pay. Yeast The direct-fed microbial we are most familiar with is yeast. Yeast supplements have been around for a couple of decades now, and there are many suppliers of the product. Some are marketed as "live," some are not. There has been extensive research conducted on the value and efficacy of yeast in dairy diets, and there is a mountain of data that both supports its use as well as finds its use questionable. Several strains of the species saccharomyces cerevisiae are marketed throughout the U.S. Each supplier claims its product is the best, and that adds to the confusion of selecting a brand of yeast. The truth of the matter is there's still a lot of discussion as to just how yeast works in the rumen and what strains are the most beneficial. Many studies and feed trials have shown yeast will increase dry matter intakes in cows. Again, the reason for why this happens is not totally understood. It is believed that yeast competes with other bacteria in the rumen for lactic acid the main culprit causing lactic acidosis. With lower lactic acid levels rumen pH will remain at a higher level that's more appropriate for the bacteria needed to ferment and digest fiber in the rumen. As fiber is more rapidly digested it will pass out of the rumen, allowing the cow to increase dry matter consumption and overall energy intake. Yeast in and of itself does not appear to have any nutritional value for the rumen microbial population, such as an energy or protein source. Its benefit is its ability to alter the rumen environment so it will grow more good bugs. The use of yeast in a milk cow diet seems to have the greatest effectiveness in rations that contain high levels of starch and rapidly fermentable sugars those diets that have the propensity to create higher levels of lactic acid. An increase in dry matter intake is crucial for close-up and transition cows. There's good data that supports the use of yeast in transition cow diets to encourage increased feed consumption during early lactation as the fresh cow receives a high grain diet. From an economic point of view there's less reason to use yeast in a ration high in forages. The greatest economic advantage to using yeast is in herds that can be separated into two or more production groups. Higher-producing cows will usually have a higher concentrate-to-forage ratio and will benefit more with the addition of yeast in their diet. Of course, herds with 25,000+ pound production averages would benefit from yeast throughout the entire lactation and dry period. Bacterial DFMs More recently there has been a lot of interest in bacterial direct-fed microbials which supply beneficial microorganisms to the intestinal tract of dairy cows and heifers. Again, there's a lot of conflicting data as to the efficacy of these products. The most widely used species is Lactobacillus of which there are a number of strains. It is believed that by introducing sufficient quantities of these microbials into the small intestine they will assist in maintaining a pH level that will discourage the existence of more harmful bacteria such as E. coli. The purpose of incorporating bacterial direct-fed microbials into the diet is to bolster the immune system. These microbials were originally introduced to prevent intestinal disorders in calves. Bacterial direct-fed microbials have been administered to calves fed milk as well as weaned calves for many years with the belief that the immature guts of these animals would benefit from the beneficial micro-organisms. They are now being used in milk cow diets and, here again, animals that could gain the most benefit from them are transition and high-producing cows that may be under the most stress. Enzymes Enzymes are specialized proteins that act as catalysts in the digestion of starches and fiber in the rumen. Amylase is the enzyme that helps digest starch in the rumen, and cellulase and xylanase are two of the enzymes that work on fiber digestion. All three enzymes are commercially available to dairy producers. The inclusion of additional fibrolytic enzymes in the ration serves to more completely break down NDF fiber in the feed which will allow for a more complete digestion. Similarly, with starch being the major source of energy in the dairy diet, the inclusion of amylase has been shown to improve energy availability for the cow. Quality control is vital . . . Dairy producers need to realize that all probiotics are manufactured. Quality control is extremely important in the manufacture, handling, and shipping of yeasts, bacteria, and enzymes. This is one of those situations where you really have to trust the reputation of a well-established company that's been in the market for many years and has a proven track record for a particular product. You also need to be confident that the supplier of the probiotics is handling them correctly by not letting them set in a warehouse for extended periods of time or exposing them to the elements. Probiotics have a shelf life, after which they will not be effective. The cost of using a probiotic in a typical lactation diet will run from as little as 5 cents per cow per day to over 25 cents. I am not in any way discouraging the use of direct-fed microbials and enzymes in dairy diets because there is enough evidence that supports their use. Enzymes and bacterial direct-fed microbials have been used in the monogastric species for many years. Their use in milk cow rations is still somewhat experimental. You also need to know that different feeding programs and different feedstuffs in a ration will influence the results you will see from probiotics. The physiology of the rumen and microbial population in the small intestine is complex, and there is a lot more research that needs to be done to match specific strains of direct fed microbials to specific diets. Consider them as tools that can be used to increase dry matter intake and milk production. Used judiciously, direct-fed microbials and enzymes will result in a good return on investment.
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