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FULL TEXT PAPER
Strategic Use of Feed Additives in Dairy Cattle Nutrition
by Michael F. Hutjens


While nutritionist and dairy farmers place major emphasis on dry matter intake, protein, fat, fiber, and energy needs; additives can be important to improove milk production, herd health, and reproduction. Supplementing additives to dairy rations present several challenges.

  1. The amount needed may be related to milk yield while other are directly related to dry matter intake (such as buffers).
  2. Stage of gestation can significantly increase the recommended amounts (for example anionic salt).
  3. Additives can be expensive to add to the ration.
  4. If one ration is fed, the type, number, and amount of additives selected must carefully considered as the feed costs can be significantly increased.
  5. Cows in certain stage of lactation and gestation may respond to an additive economically, yet all cows fed the ration receive the additive (for example, niacin fed to fresh cows results in an economic response, but cows after 100 days postpartum may not).

FEED ADDITIVE APPLICATIONS

Feed additives are feed ingredients that produce a desirable animal response in a non-nutrient role (such as a change in the rumen environment with buffers or shifts in metabolism using niacin). Farmers and nutritionist must consider:

  1. Why the additive is needed (reduce ketosis or higher dry matter intake for example)
  2. Which cows will respond
  3. if the response is economical (Table 2)
  4. how will farm response be measured (milk yield, milk components, somatic cell count change, or health changes).

Table 3 outlines dairy cow additives listing their function, recommended level, benefit to cost ratio (based on U.S. research and costs), feeding strategies, and current recommendation. The following recommendation classifications were used based on research and on farm results.

  • Recommended: Use as needed
  • Experimental: More research is needed
  • Evaluative: Monitor results on individual farms
  • Not recommended: Lack of economic response at this time

Effects of buffers

The dairy cow has a complex acid-base regulatory system with the rumen varying in pH from 5.5 to 6.8. If the rumen pH is not optimal, microbial yield and efficiency drops, dry matter intake declines, and metabolic disorders can increase. A buffers is a combination of weak acid and its salt which resists changes in pH or hydrogen ion concentration. An ideal rumen buffer should tie up hydrogen ions (equivalence point or pKa) near the desired rumen pH. An alkalinizing or neutralizing product increases the pH in the rumen fluid. Several products can be incorporated in buffer packs (Table 5). Recommended levels must be fed to have impact in the rumen.

  • Sodium bicarbonate (bicarb) is the standard buffering agent with a pka at 6.25. Bicarb has been extensive studied, buffers at a pH 6.25, increases rumen osmolarity, and shifts rumen VFA (volatile fatty acids) patterns.
  • Sodium sesquicarbonate contains a mixture of sodium bicar-bonate (buffer) and sodium carbonate (alkalinizer). The pH of a one percent solution is 9.9. Research results indicate it is an effective buffering agent.
  • Magnesium oxide is a source of magnesium (54 percent by weight) and functions as an alkalinizer. It can increase uptake of milk fat precursors by the mammary gland. Solubility and particle size can affect rumen action.
  • Calcium carbonate has little if any buffering action in the rumen. It can increase fecal pH when high starch diets are consumed by increasing starch digestion in the lower digestive tract.
  • Sodium bentonite is a clay mineral used as a pellet binding agent. It can swell in the rumen, shift rates of passage, and adsorb minerals. It does not have buffering capacity.
  • Potassium carbonate is an effective buffering agent which also provides added potassium needed under heat stress conditions. Research results are limited, but favorable. Cost is typically higher than bicarb for comparable levels of buffering capacity.

Add .75 percent of the total ration dry matter as sodium bicar-bonate or sodium sesquicarbonate ( 25 kg D.M. X .0075 = 187 grams/ cow/day). A ratio of 2 to 3 part bicarb equivalence to one part magnesium oxide is recommended. Supplement a buffer under the following conditions:

  • Total ration ADF below 19 percent
  • Total ration NDF below 28 percent
  • Forage NDF below 21 percent
  • Feeding more than 3 kg of grain per meal
  • Feeding more than 2 percent of cow's body weight as forage

When a buffer pack is added, monitor dry matter intake to assess effectiveness (one kg/cow/day increase in total ration dry matter is good response).

Table 2. Required increase in milk yield to recover various additive costs with different milk prices.

Additive Cost Milk Price ($/cwt)
20 16 14
lb milk/cow/day
.02 0.1 0.1 0.2
.06 0.3 0.4 0.4
.10 0.5 0.6 0.7
.30 1.5 1.7 2.1

Table 3. Feed additive guidelines for dairy cows.

ASPERGILLUS ORYZAE (AO products)

  1. Function: Stimulate fiber digesting bacteria, stabilize rumen pH, and reduce heat stress
  2. Level: 3 g per day
  3. Benefit to Cost Ratio: 6:1
  4. Feeding Strategy: High grain diets, low rumen pH conditions, and under heat stress cows
  5. Status: Evaluative

BETA-CAROTENE

  1. Function: Improve reproductive performance, immune response, and mastitis prevention
  2. Level: 200 to 300 mg per day
  3. Benefit to Cost Ratio: Not available
  4. Feeding Strategy: In early lactation and during mastitis prone time periods
  5. Status: Not recommended

CHOLINE

  1. Function: A methyl donor used to minimize fatty liver formation and to improve fat mobilization
  2. Level: 30 g per day
  3. Benefit to Cost Ratio: 4:1 (when protected)
  4. Feeding Strategy: Feed dry cows two weeks prepartum and to cows experiencing ketosis and weight loss
  5. Status: Not recommended until rumen protected source is commercially available

MAGNESIUM OXIDE

  1. Function: Alkalinizer (raises rumen pH) and increases uptake of blood metabolites by the mammary gland raising fat test
  2. Level: 45 to 90 g per day
  3. Benefit to Cost Ratio: Not available
  4. Feeding Strategy: With bicarbonate-based buffers
  5. Status: Recommended

METHIONINE HYDROXY ANALOG

  1. Function: Minimize fatty liver formation, control ketosis, and improve milk fat test
  2. Level: 30 g
  3. Benefit to Cost Ratio: 2:1
  4. Feeding Strategy: Feed to cows in early lactation fed high levels of concentrate low in protein
  5. Status: Not recommended

NIACIN (B3, nicotinic acid, and nicotinamide)

  1. Function: Coenzyme system in biological reactions, improve energy balance in early lactation cows, minimize ketosis, and stimulate rumen protozoa
  2. Level: 6 g per cow (preventive and prepartum) 12 g per cow (treatment and postpartum)
  3. Benefit to Cost Ratio: 6:1 (6 g level)
  4. Feeding Strategy: High producing cows in negative energy balance, heavy dry cows, and ketotic-prone cows fed two weeks prepartum to peak dry matter intake (10-12 weeks)
  5. Status: Recommended

PROBIOTICS (Bacterial direct-fed microbes)

  1. Function: Produce metabolic compounds that destroy undesirable organism, provide enzymes improving nutrient availability, detoxify harmful metabolites, and stimulate dry matter intake (calves and cows off feed)
  2. Level: Not clearly defined
  3. Benefit to Cost Ratio: Not available
  4. Feeding Strategy: To cows at calving and during stress conditions
  5. Status: Experimental

SODIUM BENTONITE

  1. Function: A clay mineral used as a binder, shifts VFA patterns, slows rate of passage, and exchanges mineral
  2. Level: 450 to 700 g per day (rumen effect)
  3. Benefit to Cost Ratio: Not available
  4. Feeding Strategy: With high grain diets, loose stool conditions, low fat test, and dirt eating
  5. Status: Evaluative

SODIUM BICARBONATE/SODIUM SESQUICARBONATE (BUFFER)

  1. Function: Increase dry matter intake and stabilize rumen pH
  2. Level: .75 percent of total ration dry matter intake
  3. Benefit to Cost Ratio: 4:1
  4. Feeding Strategy: Feed 120 days postpartum with diets that are high in corn silage (over 50%), wet rations (over 45% moisture), lower fiber ration (<19% ADF), little hay (< 2.2 kg), finely chopped forage, pelleted grain, slug feeding, and heat stress conditions
  5. Status: Recommended

YEAST CULTURE

  1. Function: Stimulate fiber digesting bacteria, stabilize rumen environment, and utilize lactic acid.
  2. Level: 10 to 120 g depending on yeast culture concentration
  3. Benefit to Cost Ratio: 4:1
  4. Feeding Strategy: Two weeks prepartum to two weeks postpartum and during off-feed conditions and stress
  5. Status: Recommended

ZINC METHIONINE

  1. Function: Improve immune response, harden hooves, and lower somatic cell counts.
  2. Level: 9 g per day (Zinpro 40 product)
  3. Benefit to Cost Ratio: 14:1
  4. Feeding Strategy: To cows experiencing foot disorders
  5. Status: Recommended

Table 5. Feeding recommendations for products used as buffers for lactating cows.

  Product Level (grams/day)
Sodium bicarbonate 110 to 225
Sodium sesquicarbonate 110 to 225
Magnesium oxide 50 to 90
Sodium bentonite 225 to 454
Calcium carbonate 115 to 180
Potassium carbonate 270 to 410






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