Animal Health

• The ABCs of Teat Dipping by Paul E. Johnson, DVM, Enterprise, Alabama

• Prevention of Milk FeverWith Anionic Salts by Dennis A. Daugherty, PhD, Turlock, California

Teat dipping can be proven money-maker as part of your mastitis-control program. Knowing how to select and apply dips properly can give more punch to your mastitis strategy.

Dips are most often selected on price alone. Other factors influencing choice: high pressure sales tactics, magazine testimonials and industry-sponsored meetings. Cost should examined, but it shouldn't be the sole determining factor. The teat dip you use should match the facilities, environmental factors and mastitis pathogens present on the dairy.

Dips have one common goal--to kill mastitis causing bacteria. How a teat dip kills bacteria is what distinguishes it from others. Active ingredients include iodine, chlorhexidine, lactic acid and ammonium salts. Dips may also contain emollients, skin conditioners, barriers and skin dyes that can enhance their performance.

Unlike pharmaceuticals that must undergo rigorous testing for effectiveness by government officials. The government only requires a label indicating the active ingredient, its concentration, the name and address of manufacturer, the lot number, and expiration date.

So don't assume that a dip effective simply because it is on the market. There is discussion within FDA to start investigating teat dips for efficacy. For now, teat dips are regulated by the industry itself that produces and uses these chemicals. There are a series of standardized tests, established by the National Mastitis Council and voluntarily used by manufacturers to evaluate dips. These protocols test under both lab and field conditions.

A dip labeled under Protocol C, for instance, means that the product has been tested under actual farm conditions and proved effective in controlling mastitis pathogens. I only recommend Protocol C-tested dips to clients since many times laboratory results (Protocol A or Protocol B) don't hold up in the farm environment.

Make sure the Protocol C test was done recently. Some companies still rely on data from the 1960s, when many environmental bugs were not yet being tested. And make sure the Protocol C was performed for the specific way you're going to use it--pre or post-dip.

Proper usage is the second half of the one-two punch you deliver to mastitis bugs when you use teat dips. The greatest problems I have seen with dips have been application errors, improper storage and the use of the wrong dip for the job intended.

A teat dip is used either as a pre-dip or a post-dip. Each procedure is designed to attack and kill a certain class of mastitis bacteria. Pre-dipping helps control environmental bacteria, while post-dipping works against contagious pathogens.

Pre-dipping will be less successful if you use dips that are slow to kill bacteria--contact time with the skin is under one minute in most pre-milking hygiene procedures. A common mistake I encounter is diluting a concentrated iodine pre-dip to 0.5% or 0.1%. Some low-iodine dips release iodine from its bound state at a faster rate than the higher-concentration dips. Simply diluting a more concentrated dip cannot duplicate this process.

Incomplete dipping is another common problem. Spraying with hand bottles or vacuum-operated systems rarely ensures total coverage of the teat. Partial application can lead to both environmental and contagious mastitis problems. When the Teat is only partially dipped, you can only expect partial success in controlling mastitis.

These spray systems can be convenient to use, but they may not always ensure total coverage of the teat surface. Before you change methods, make sure your employees are using equipment properly.

There can also be application problems when dip cups are used. If the well of the cup is not deep enough to fully submerge the teat, then mastitis problems can occur.

Other Application Hints:

• Exposing dips to air can dissipate the active ingredient in the dip.
  
• Chemical reactions between different dips used in pre-and post-dipping programs can lead to chemical burns of the teat skin, which can lead to mastitis.
  
• When mixing concentrated dips, make sure you use good water. Water high in total dissolved solids may have to be treated before use.
  
• Be aware of storage conditions. Do not let teat dips freeze, since freezing can render some dips ineffective.

Paul Johnson, D.V.M., Enterprise, Alabama. Paul has a consultation veterinary service to dairy farms in Alabama, Georgia, Florida, Texas, Puerto Rico & Mississippi. Approximately 45,000 cows are currently being serviced by his practice. Consultation services to allied dairy industries in the United States, Japan, U.S., Virgin Islands, Dominican Republic, Brazil and Australia. Paul lectures all over the world. He was awarded the 1993 American Association of Bovine Practitioners Award for Excellence in Dairy Preventive Medicine.

Milk fever continues to be a disease of major economic importance to the dairy industry. Basically, milk fever is a temporary imbalance between calcium intake and calcium requirement. Resulting low blood calcium levels lead to classic downer cow symptoms within 72 hours of calving, but occasionally before, during or several months after calving.

Incidence of milk fever is estimated to be between 7 and 10% of 2nd plus lactation cows and increases with cow age. Economic losses due to treatment drugs, veterinary services, increased culling, death loss, and reduced production exceed $300 per cow. Increased incidence of secondary diseases, such as mastitis, retained placenta, limb injuries, and pneumonia can further inflate losses.

The standard treatment for milk fever is intravenous injection of calcium gluconate. Depending on severity of milk fever, secondary complications, age of cow, and timeliness of treatment, 75 to 80% of cows will recover within 2 hours of treatment. However, up to 30% of responding cows may relapse and require additional treatment. Death loss from milk fever is generally less than 5% of treated cows, but an additional 10% of affected cows may be culled due to incomplete recovery.

The economic losses from milk fever demonstrate the importance of prevention as opposed to treatment. The traditional method of preventing milk fever is to restrict calcium intake during the dry period. A diet low in calcium leads to low blood calcium thereby triggering an increased ability to absorb dietary calcium and increased mobilization of stored calcium from bones. Ability to mobilize calcium from bones is critical at the onset of lactation as dietary absorption of calcium is insufficient to meet requirements. This process, controlled by hormonal change, requires a minimum of 10 to 14 days of low calcium intake.

Traditional recommendations are to feed approximately 100 grams/day of calcium to far-off dry cows and then reduce calcium to less than 70 grams/day 2 to 3 weeks before expected calving date. Phosphorus levels should be maintained at 35 to 40 grams/day throughout the dry period. Unfortunately, restricting calcium intake is not always successful in preventing milk fever.

Research and practical applications over the last 10 years has shown that balancing dry cow rations for positive and negative electrical charge of macro minerals is more related to incidence of milk fever than calcium intake. Minerals with a negative charge are termed anions and minerals with a positive charge are termed cations.

Macro Minerals of Concern in Dry Cow Rations:

• Analyze all forages available for close-up rations for Na, K, Cl and S. Do not rely on table values. Set aside low potassium roughages for close-up cows.
• Select forages relatively low in Na & K compared to Cl & S. Corn silage is favored over oat-wheat silage.
• Avoid large amounts of concentrates high in Na or K. (beet molasses, whey products, soybean hulls)
• Formulate basal ration to meet requirements for protein, energy, vitamins and non-"DCAD formula" minerals.
• Formulate for calcium intakes of 150 to 180 grams/day. High levels of low potassium alfalfa hay is very cost effective.
• Formulate for phosphorus intakes of 45 to 50 grams/day.
• Add anionic salts to lower DCAD to -10 to -15 mEq/100 grams ration dry matter.
• Add sulfate salts (calcium, magnesium, ammonium) to achieve ration requirement of 0.4% of dry matter. Calcium sulfate is a desirable first addition as it contributes to calcium requirement and is very cost effective. Magnesium sulfate is fairly palatable and can be used to help meet magnesium requirement of 0.4% of ration dry matter. Excessive magnesium sulfate is very laxative.
• Add chloride salts (calcium, ammonium, magnesium) as needed to bring DCAD to -10 to -15 mEq/100 grams ration dry matter. Magnesium chloride is very expensive and seldom used.
• Limit the use of ammonium salts. Crude protein equivalent from non-protein nitrogen should not exceed 3.0% of ration dry matter.

• Be sure cows are on close-up rations a minimum of 2 weeks and a maximum of 4 weeks. Too long on a negative DCAD rations is not desirable as bones may demineralize too much.
• Check urine pH of close-up cows. A -10 to -15 mEq/100 gram DCAD should result in pH's of 6.0 to 6.99.
• High pH's ( > 7.0 ) suggest a positive DCAD. Resample forages, supplemental mineral and possibly a TMR for DCAD formula minerals. Be sure anionic mineral is consistently added.
• Variable pH's ( high and low ) suggest poor feed mixing or selective eating by cows. Examine mixing order, time of mixing and consistency of TMR. Premixing concentrates is desirable. Analyze samples of TMR and any feed refusals. Palatability may be a problem.
• Low pH's ( < 6.0 ) may also be a problem. DCAD is too negative resulting in metabolic acidosis. Decrease level of anionic salts.
• Desired pH's ( 6.0 - 6.99 ) but still having metabolic disease. Usually when this occurs, rations are deficient in available calcium. Examine total ration calcium levels. Remember calcium should be elevated to 150-180 grams/day.

In summary, balancing close-up rations for a negative DCAD can be very effective in controlling metabolic disease. However, you must commit yourself to testing forages, maintaining ration consistency and monitoring urine pHs.

Dennis A. Daugherty, Ph.D.
Pine Creek Nutrition Services

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