Feed additives

A survey of commonly used feed additives in dairy rations

1. Buffers:

Buffers help to reduce the rumen acidity that commonly results from feeding diets designed for high milk production. They can increase dry matter intake, rumen microbial protein production, and fiber digestion, resulting in increased milk production and milkfat production.

Sodium bicarbonate (bicarb) is the most common ruminal buffer. Church & Dwight Co. (Princeton, NJ, USA) and Bioproducts (Fairlawn, OH, USA) are two primary manufacturers. It is a standard procedure in the U.S. to feed 6-8 oz. (0.17 to 0.22 kg) of buffer in diets formulated for greater than 80 pounds (36 kg) of milk per day. In addition, many farmers with free-stall housing offer buffer to cows on a free-choice basis in plastic tubs. Researchers in Pennsylvania concluded that when milk was priced at $12.75/cwt ($0.28/kg) and feed was priced at $136 per ton ($0.15/kg), a type one error (using bicarb when a response is not expected) would cost $0.04 per cow per day. A type two error (not using bicarb when a response is expected) would cost $0.30 per cow per day.

Sodium sesquicarbonate (S-carb) is sold by FMC Agricultural Chemical Group. It contains a blend of sodium bicarbonate and sodium carbonate. Its price is typically lower than bicarb but often it is fed at higher levels (up to 0.75 pounds (0.34 kg)/cow/day).

2. Magnesium Oxide

Magnesium oxide helps to raise rumen pH, increase uptake of plasma acetate and fat by the udder, and increase milkfat percentage. It is typically fed at a rate of 1.5-3 oz. (45-90 grams) per cow per day. Magnesium oxide is rarely recommended in place of sodium bicarbonate but often is fed in addition to it. Some studies have found an additive effect of sodium bicarbonate with magnesium oxide. It is sometimes recommended at a ratio of 2-3 parts sodium bicarbonate to 1 part magnesium oxide. Dietary magnesium should not exceed 0.5% or cows are likely to get black diarrhea.

3. Niacin (B3, nicotinic acid, nicotinamide) :

Niacin is a B vitamin produced by the rumen microbes and, therefore, not traditionally considered to be a required nutrient in ruminant diets. Niacin is used for many different body functions. It is known for its use in the metabolism of body fat in early lactation cows, reducing the incidence of ketosis. Niacin may also improve milk protein yield from cows fed large amounts of dietary fat. It has been suggested that supplemental niacin (6-12 g/cow/day) in addition to the niacin produced in the rumen is beneficial for early lactation cows. New Hampshire researchers suggested a 6:1 benefit to cost ratio for niacin.

4. Rumen-Protected Choline :

Choline is a water-soluble vitamin that, like niacin, is produced by the rumen microbes. As with niacin, researchers now believe that the rumen microbes may not make enough choline to supply all of the cows needs, especially during the transition period. Choline makes up part of the structure of body cells, especially cell membranes. Choline may have a methionine-sparing effect since about 30% of absorbed methionine is used for making choline.

Choline is involved in the use of fats and their transport out of the liver in the form of very low density lipoproteins (VLDL). Of course, it is especially critical during the transition period for the cow to be able to clear the liver of accumulating fat in order to avoid fatty liver syndrome. In studies where supplemental choline as choline chloride was infused directly into the abomasum or was fed in a rumen-protected form, it was determined that the average milk response was 4.2 pounds (1.9 kg) /cow/day with 31 to 45 grams of supplemental choline/cow/day.

Rumen bacteria degrade most of the dietary choline consumed by the cow. So, supplemental choline must be fed in a rumen-protected form. Reashure® from Balchem Corporation ( Slate Hill, NY,USA) is a commercial source of encapsulated choline that is designed to pass through the rumen for subsequent absorption in the cow’s small intestine. It is fed at a rate of 2 oz. (57 grams) per cow per day costing about $0.30/cow/day.

5. Methionine Hydroxy Analog (MHA)

Methionine Hydroxy Analog is often included in buffer packages for lactating cows because of research showing that it increases milkfat production. Researchers have suggested that the rumen microbes, especially the fiber digestors, positively respond to the extra methionine or to the carbon skeleton (isoacid) provided by the methionine. MHA might also be used by the rumen microbes for choline synthesis.

Intestinally absorbed MHA is converted by the cow’s body to L-methionine. MHA is commonly used as a supplemental methionine source in poultry and pig diets. Alimet® is a liquid MHA currently being marketed by Novus International, Inc. as a source of rumen bypass methionine. Canadian research indicated that 40% of liquid MHA escaped the rumen when it was fed as a large single dose. Other researchers have fed smaller amounts of MHA over a period of time (as would be more typical of a commercial dairy) and found that most of the MHA (99%) was degraded in the rumen. It has been difficult to show consistent increases in plasma methionine levels and milk protein production when liquid MHA is fed. Dr. Chuck Schwab from the University of New Hampshire concluded in his presentation at the 1998 California Animal Nutrition Conference, Fresno, CA that liquid MHA has its primary influence in the rumen and that more research is needed to prove its efficacy as a source of post-ruminal methionine.

6. Ionophores

Monensin (brand-name Rumensin, Elanco, Indianapolis, IN) and lasalocid (brand-name Bovatec, Hoffman-LaRoche Inc., Nutley, NJ) are antibiotics which act as ionophores in the rumen. Currently, these products are approved only for feeding heifers in the United States. The U.S. Food and Drug Administration is reviewing the use of monensin in lactating dairy cattle. Ionophores are legal to be fed to heifers and to lactating dairy cattle in Canada and New Zealand.

Ionophores change the balance between sodium and potassium within gram-positive rumen bacteria cells, resulting in increased cell acidity and growth inhibition. Gram-positive bacteria in the rumen include those that produce methane, ferment protein, and produce lactate (a very strong acid). Consequently, when the growth of these bacteria is slowed, less rumen available energy is wasted as methane, more protein escapes the rumen, and rumen pH is increased. The resulting animal response is more efficient use of energy and protein leading to increased growth rate. Pennsylvania studies found that heifers fed ionophores calved 38 days earlier and the benefit to cost ratio was 12:1. Both monensin and lasalocid are also approved as coccidiostats. This added benefit for young calves leads most feed companies to routinely include either monensin or lasalocid in their dairy heifer feeds.

Ionophores increase the ratio of propionate to acetate in the rumen. Propionate is needed for lactose (milk sugar) synthesis and is a primary driver of milk production. Propionate is also important in the liver of transition cows to reduce ketosis. Ionophore studies with lactating cows have shown inconsistent milk responses depending on diet. Ionophores usually reduce ketosis and cause milkfat depression.

7. Decoquinate (Deccox®)

Decoquinate is added to milk, milk replacer and calf starter to aid in the prevention of coccidiosis. It is fed at a rate of 22.7 mg per 100 pounds (45.45 kg) of body weight. It costs about $0.02 per head per day.

8. Yeast Products

Two types of yeast products are primarily on the market: live yeast products and yeast culture. Their inclusion in dairy cattle diets, especially in early lactation, may increase dry matter intake, increase milk and milk component production, stabilize the rumen fermentation, and increase rumen microbial growth. Studies with yeast products have shown as much as an 8:1 return on investment. Unfortunately, responses are inconsistent, partly due to differences between the many commercial products on the market. Despite their lack of predictability, it was estimated in 1997 that 30% of dairy herds in the U.S. used yeast products.

Live yeast products contain viable yeast (such as, Saccharomyces cerevisiae) and the media on which the yeast is grown. Yea-Sacc1026 (Alltech Inc, Nicholasville, KY, USA) and Biomate Yeast Plus (10 grams/cow/day) (Chr. Hansen BioSystems, Milwaukee, WI,USA) are examples of live yeast products. The products are dried so that the activity of the yeast cells is preserved. Studies have shown that these products can increase the amount of lactate-utilizing bacteria, perhaps because of their malic acid content. The result of this situation is a stabilization of rumen pH and enhancement of microbial growth. Furthermore, companies who sell these products believe that the live yeast cells provide co-factors such as B-vitamins, enzymes, and isoacids that stimulate the rumen bacteria, especially the fiber-digesters. The live yeast cells may also use up any oxygen present in the rumen, thereby stimulating the predominant population of anaerobic bacteria.

Yeast culture, such as Diamond V “XP” Yeast Culture (2 oz. (60 grams)/cow/day) (Diamond V Corporation, Cedar Rapids, IA, USA), contains the media in which the yeast was grown, the metabolites made by the live yeast cell during the manufacturer’s fermentation process, and dead yeast cells. Manufacturers of yeast culture believe that live yeast cells cannot grow in the rumen because of competition from the rumen bacteria, the slow growth rate of the yeast cells, and the relatively fast turnover of rumen contents. For this reason, these manufacturers don’t attempt to preserve live cells and rely exclusively on the impact of the yeast’s metabolites in the rumen. Yeast culture stimulates the rumen fermentation and increases bacteria growth, especially the growth of the fiber-digesters, in a manner similar to live yeast culture.

9. Direct-Fed Microbials (Probiotics)

Direct-Fed Microbials approved by the U.S. Food and Drug Administration include: Bacillus, Bifidobacterium, Streptococcus, Bacteroides , Lactobacillus, and Pediococcus. These are live bacteria designed to improve the animal’s balance of intestinal bacteria. Direct-Fed Microbials can reduce the growth of undesirable bacteria such as, E. coli and Salmonella, by producing organic acids and lowering intestinal pH and the oxidation/reduction potential. Direct-Fed Microbials may also produce antibiotics and other compounds that directly inhibit the growth of intestinal pathogens. Beneficial bacteria may also simply out-compete the undesirable bacteria in their rate of digestion and extent of adhesion to the intestinal villi. Some Lactobacillus organisms change the form of bile into a deconjugated form that is better at inhibiting the growth of pathogens. Lactobacillus bacteria have also been found to reduce the level of amines. Amines are made by other intestinal microbes and can irritate the intestinal tract and cause diarrhea. Direct-Fed Microbials are often used to enhance the performance of young calves that do not receive adequate colostrum or are exposed to pathogen-infested environments.

Direct-Fed Microbials have been shown to reduce the incidence of “overeating disease”. Clostridium perfringens normally grow and divide slowly in the intestine. When there is a sudden change of diet or a large amount of carbohydrate reaches the intestine, “overeating disease” can result. With this condition, the Clostridium perfringens grows rapidly and releases a toxin into the bloodstream causing death in only one or two hours. Calves consuming a high-grain diet are very susceptible to “overeating disease”. I have had one personal experience with “overeating disease” in a well-managed, 250-cow dairy that produced an average of 88 pounds (40 kg) of milk/cow/day and had an average dry matter intake of more than 55 pounds (25 kg). It was hypothesized that even though the diet was well-balanced and the cows showed few signs of rumen acidosis, large amounts of starch were flowing to the intestine of these cows because of the high dry matter intake. Direct-Fed Microbials were added to the ration and the “overeating disease” which had been causing the death of at least 1 cow every other month, was stopped.

Some Direct-Fed Microbials, such as Bacillus, produce enzymes that assist in digesting feed. Many dairy farmers have used Direct-Fed Microbials when they were feeding mature, hard-kernel corn silage and have observed fewer corn kernels in the manure and significant responses in milk production.

In order to achieve their objective, Direct-Fed Microbials must be viable, fast growing, and able to survive in acid. These products are manufactured in many forms, including powders, boluses, pastes, and liquids. In the United States, there are many suppliers of Direct-Fed Microbials. Some are good and many are not so good. Direct-Fed Microbials are not regulated by the FDA but they are required to have AFFCO label registration so they must guarantee the levels of bacteria which exist at the time of manufacture. Reputable manufacturers are concerned about the levels of bacteria at the time of use and they take great care in stabilizing and packaging their products. Direct-Fed Microbials are generally affected by air, moisture and storage time. A reputable manufacturer will also have ISO-9000 certification that means the product was produced in compliance with the rigid standards of the international ISO governing organization. Alltech, Inc. (Nicholasville, KY, USA) and Chr. Hansen BioSystems (Milwaukee, WI,USA) are two well-known manufacturers of Direct-Fed Microbials.

10. Enzymes

Enzymes are natural catalysts produced by the body to aid in the digestion of feed proteins, starches, and fiber. Commercial forms of enzymes are made from the fermentation extracts of bacteria, such as Bacillus subtilus, Trichoderma longibrachiatum, and Aspergillus oryzae. Enzymes are included at 0.01 to 1% of the diet. The benefits of adding additional commercial enzymes to the diets of dairy cattle may include increased feed digestion, increased efficiency of feed utilization, and better animal performance. Manufacturers of enzymes recommend them for calves who often produce marginal amounts of enzymes for feed digestion, for cattle under stress who reduce production of natural enzymes, and for high-producing dairy cattle with high levels of dry matter intake who will greatly respond to additional nutrient digestion. Inconsistent responses to enzymes are probably caused by differences in diet composition, type of enzyme, level of enzyme provided, enzyme activity level, the length of time between enzyme application and feeding, and the stability of the enzyme in the rumen. One study conducted by Stokes and Zheng (1995) reported a 10.7% increase in dry matter intake and a 14.8% increase in milk yield when a fibrolytic enzyme was added to a mixed diet containing alfalfa hay, alfalfa silage, and barley. Use of enzymes on commercial dairy farms in the U.S. is very limited. This is probably due to the variability in responses that have been seen and the relatively high cost of enzymes when compared to other feed additives. Further research is needed.

11. Yucca Extract (Deodorase®, Micro-Aid®)

Yucca extract contains urease inhibitors and is added to the diet with the idea of reducing blood and milk urea nitrogen levels in dairy cows. Urea (from saliva and dietary urea and dietary protein) is broken down in the rumen by enzymes (urease) to ammonia. The microbes then combine the ammonia with byproducts from the fermentation of carbohydrates to form amino acids that are then combined in chains to form microbial protein. The rumen microbes need the urea to be converted to ammonia so that they can use it. The problem nutritionists often face is that the urea is broken down too fast (too much soluble protein). The microbes can’t work fast enough and don’t have enough carbohydrate available at the right time to utilize all of the ammonia before it is absorbed out of the rumen. His situation creates high blood and milk urea nitrogen levels in the cow.

Yucca extract might aid in the reduction of ammonia coming from manure in certain confinement facilities but whether or not it produces a noticeable increase in milk yield or reproductive performance by its effect in the rumen has not been sufficiently demonstrated. A better method for controlling BUN and MUN levels is by controlling the degradable protein fractions (SIP and DIP) and providing a blend of rapidly and slowly fermentable starches and sugars in the diet.

12. Organic Acids

Dr. Scott Martin from the University of Georgia has shown that organic acids, specifically DL-malate, can increase use of lactate by the rumen microbe, Selenomonas ruminantium. Malate may be converted to oxaloacetate and help to reduce its deficiency associated with gluconeogenesis. It may also provide an electron sink for hydrogen, allowing lactate usage. Dairy cow diets containing large amounts of fermentable carbohydrate and marginal amounts of effective fiber may produce significant amounts of lactate in the rumen. Lactate is a very strong acid and its accumulation can result in rumen acidosis, reduced fiber digestibility, reduced dry matter intake, low milkfat production, reduced milk production and laminitis. Studies with cannulated steers have shown that the addition of 2.8 oz. (80 grams)/day of DL-malate can increase rumen pH and increase the production of acetate (the major VFA associated with fiber digestion and milkfat synthesis). The cost of supplementing malate is between 9 and 19 cents per day. Dr. Martin has suggested that the malate requirement may also be met by selecting for dietary forages that are higher in malate, such as alfalfa or less-mature grasses. More research is needed.

13. Biotin

Biotin is a water-soluble B-complex vitamin. The rumen microbes manufacture all of the water-soluble B-complex vitamins, including niacin, thiamin and riboflavin. In the past, nutritionists believed that a sufficient amount of biotin was made in the rumen to supply all of the cow’s needs. It was difficult to create a clinical biotin deficiency in cows. New studies have shown that rumen biotin production decreases as the level of grain in the diet increases above 35% in the ration. The rumen makes only 2 to 4 mg of biotin per day. Typically, diets that aren’t supplemented with biotin will supply 4 to 10 mg of biotin per day and the biotin found in feeds is generally not as available to the cow as microbial biotin. Cows fed 20 mg of supplemental biotin per day have had blood serum concentrations that were twice as high as control cows and milk concentrations two or three times as high.

Recent research has shown that biotin supplements can improve hoof health. Hooves are made of very strong, keratinized tissue. They require special nutrients to grow and function, including biotin, copper, zinc, calcium, phosphorus, magnesium, vitamins A and D, and the two sulfur amino acids (cystine and methionine). If the cow receives a limited supply of any of these nutrients either due to a limited concentration in the blood or when blood circulation is disrupted (as in laminitis), the hoof horn will weaken and the cow will be more likely to get hoof lesions. Researchers have created biotin deficiencies in calves. The signs of biotin deficiency include soft, crumbly hooves, hair loss, and skin lesions.

More than 10 controlled research trials have been completed in which veterinarians carefully evaluated hoof health. For most studies, biotin was fed at 20 mg per cow per day. The average time of response was 8 to 12 months because hooves grow so slowly. In all of the studies, there were significant reductions in at least one type of hoof disorder (sole ulcers or heel erosion, heel warts, claw lesions, and sand cracks).

At the American Dairy Science Association Meetings in 1999, the results of a controlled 12-month field trial in state of Washington were presented. Half of the cows on a 150-cow dairy farm were supplemented with 20 mg per day of biotin and the other half were not supplemented. The cows were housed in a freestall barn, fed a high corn silage ration, and averaged 72 pounds (32.7 kg) of milk. Feet were trimmed every 6 months. At the final foot trimming, 20 of 40 control cows (50%) and 10 of 42 biotin-fed cows (24%) had sole hemorrhages. The difference was statistically significant. The percentages of control cows having double soles, ridges, and heel horn erosion were 28%, 43%, and 53% and for biotin-fed cows 31%, 24%, and 52%, respectively. Those differences weren’t statistically significant. Unfortunately, this study didn’t evaluate heel warts. In general, there is less data on heel warts. However, there are two German studies with small numbers of animals showing a reduction in heel warts with biotin supplementation.

Biotin is a needed co-factor that enables enzymes to work in many chemical reactions in the body. Biotin is needed for the body to process amino acids, to make glucose from the propionate produced in the rumen, and to make fat from the acetate produced in the rumen. Of course, as the cow makes more milk, she needs more biotin for these functions. Biotin is also required by some of the rumen bacteria, especially the fiber-digesting bacteria. In the test tube, added biotin has increased fiber digestibility but in the cow, this effect hasn’t been studied. Biotin is also needed for the rumen microbes to produce propionate.

Only a few trials have been conducted to look at the effect of biotin on milk production.

In the Washington trial previously described, milk production for the lactation was 1931 pounds (878 kg) higher for the biotin-fed cows. OhioStateUniversity research found that cows fed 20 mg of supplemental biotin per day from two weeks before calving to 100 DIM produced 6.4 pounds (2.9 kg) more milk/day than cows that were not supplemented. The control cows averaged 81.2 pounds (36.9 kg) of milk/day and the treated cows averaged 87.6 pounds (39.8 kg) of milk/day. There were 15 cows per treatment. Dry matter intake was the same for all cows (44 pounds (20 kg) per day). Because intake did not increase and the milk response was immediate, the researchers did not attribute the response from biotin to an improvement in hoof health. They suspected that the supplemental biotin helped cows to produce more glucose from the propionate produced in the rumen. This would increase the production of lactose (milk sugar) and drive milk production. More research is needed to fully understand how the cow responds metabolically to supplemental biotin.

Biotin is recommended at 20 mg/day throughout lactation and 10-20 mg/day during the dry period. Heifers should begin getting 10-20 mg/day of biotin at 15 months of age. Add biotin as part of a good hoof health program along with attention to dietary effective fiber levels, ration carbohydrates, hoof trimming, and cow comfort .

14. Calcium Propionate

Inclusion of 0.25 pound (0.11 kg) of calcium propionate (or equivalent commercial supplement) in pre-fresh diets provides an extra daily dose of propionate that reduces both sub-clinical and clinical ketosis. Propionate is used at the liver to convert acetate (from mobilized fat) to energy rather than the acetate being converted into ketones.

15. Mycotoxin Binders

There are currently no additives approved in the U.S. for removing toxins from feed. Aluminosilicate and bentonite products are sold as flavoring agents, anticaking agents, or pellet binders. They are not guaranteed to prevent the problems associated with mycotoxins however, most nutritionists generally advise their use for binding toxins and taking them out of the cow’s system. Sodium Bentonite can be fed in the form of a fine powder (200 mesh) and fed at a rate of 8 oz. per cow per day (227 grams). In the U.S. the regulated upper limit for sodium bentonite inclusion in a ration is 2%. Other commercial binders exist, including Zarmin® and Diabond®. These contain sodium aluminosilicate and are fed at a rate of 4 oz. per cow per day (114 grams). It is not recommended that binders be fed continuously as a preventative against mycotoxin problems because they may bind some minerals, especially trace minerals, making them unavailable to the animal.

16. Zinc Methionine (Zinpro®)

Zinc methionine is an organic mineral source. Zinc is combined with methionine (an amino acid) making the zinc easier for the cow to absorb. Zinc is a part of many different enzymes that perform a variety of functions in the body. Nutrient metabolism, reproduction, immune function, and hoof integrity are all dependent upon zinc. Zinc methionine is fed at a rate of 9 grams per cow per day in the form of Zinpro 40®. It has been shown to improve immune response, harden hooves, and decrease somatic cell counts.

Signs of zinc deficiency include reduced intake, reduced growth, poor hoof integrity, swollen hocks, and skin perakeratosis. The NRC (2001) zinc requirement for a Holstein cow producing 99 lbs (45 kg) of milk and consuming 59.2 pounds (26.9 kg) of dry matter per day is 52 ppm (mg/kg). The maximum tolerable concentration of zinc is between 300 and 1000 ppm (mg/kg) (NRC, 2001). At this level, zinc interferes with copper absorption. So, toxicity symptoms are related to copper deficiency.

17. Anionic Products

Hormones normally work to mobilize calcium from the cow’s bones and to increase the efficiency of dietary calcium absorption at calving time. The hormones keep blood calcium at normal levels (9-10 mg/dl). Unfortunately, these hormones are inhibited when diets high in potassium or sodium are fed. These minerals are cations. They alkalinize the blood making its pH higher. High potassium will also decrease the availability of dietary magnesium. Low blood magnesium will prevent the cow’s system from recognizing low blood calcium levels; further decreasing hormone production, calcium mobilization, and calcium absorption.

One way to make the cow’s blood acidic is by adding anionic products to the diet during the last three weeks before calving. This method should be used when no low potassium forages are available. In the past, sulfates such as ammonium sulfate, calcium sulfate (gypsum), and magnesium sulfate were used as anionic sources. Now, chlorides such as calcium chloride, magnesium chloride, and ammonium chloride are recommended over sulfates because they have been shown to be more effective. There are also commercial anionic products, for example, Bio-Chlor® and Soy-Chlor®.

To effectively use anionic products, first analyze forages for calcium, magnesium, sodium, potassium, chloride, sulfur, and phosphorus. Adjust the diet so that the dietary cation-anion difference (DCAD) is –5 to –10 mEq/100 g (-23 to –45 mEq/lb). DCAD is calculated as [(Potassium (K) + Sodium (Na) – (Chloride (Cl) + Sulfur (S))]. Most diets will need 0.6 to 0.8% chloride to significantly decrease DCAD. When using anionic products, maintain diet calcium at 1-1.5%. Dietary magnesium should be at 0.40%, phosphorus at 0.35%, and sulfur at 0.45%.

The goal when lowering DCAD is to make the cow’s blood more acidic. Urine pH can be used to monitor blood pH. Average urine pH during the last week before calving should be between 6.0 and 6.5 for Holsteins and for Jerseys, 5.8 to 6.2. If the average urine pH falls below 5.5, the cow’s blood is too acidic and dry matter intake will drop. It is best to measure urine pH about 4 to 6 hours after feeding. Increase or decrease dietary chloride according to the urine pH.


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Mary Beth de Ondarza

Mary Beth de Ondarza
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Nutritional consultant for the dairy feed industry at Paradox Nutrition, LLC.

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Dr. de Ondarza received her Ph. D. from Michigan State University and her Masters Degree from Cornell University, both in the field of Dairy Nutrition.

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Paradox Nutrition

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