County Line Dairies consist of two adjacent 2200 cow in southeast New Mexico. Both dairies are drylot, double 25 herringbone parlors with separate employees. They share breeders, feedstuffs, and generally share management philosophy. The dairy has never used rBST due to marketing agreements between processors and co-op. Both dairies milk twice daily, with throughput of approximately 250 cows per hour using 3 man milking crews. The seasonal extremes are summer time heat with rain and relatively mild, dry winters. Non AI pens are crowded to a maximum of 25 cows over. All replacement heifers are purchased from various sources. All cows and heifers are vaccinated 3 times with J5 vaccine. Cull rates averaged 28-30% for the last year. Monthly somatic cell counts (SCC) ranged from 120,000 to 220,000. Standard plate counts typically remain below 5000 cfu/ml, coliforms are typically less than 20 cfu/ml, and LPC are less than 150 cfu/ml. The greatest difficulty maintaining low SCC is in the summer when the majority of the annual rainfall occurs. There are no extraordinary efforts to prevent contagious pathogens from entering the herd, nor is routine use of intramammary drycow therapy used. The dairy is Strep agalactia and Mycoplasma free. However, there is a low prevalence of Staph aureus infections.

The dairy and its Co-op, Select Milk Producers, are committed to quality milk production. The Co-op offers quality milk bonuses and penalizes for milk that fails to meet quality standards. Select Milk Producers in conjunction with County Line Dairies has also developed the first FDA approved cold, unpasteurized milk ultrafiltration plant. Ultrafiltration concentrates milk protein, fat and bacteria approximately three fold. Somatic cell counts increase 2.2 fold. FDA approval requires the concentrated product meet the same quality standards as unpasteurized whole milk. Therefore the maintenance of overall milk quality is imperative.

The mastitis and milk quality control programs at County Line Dairies are aimed at maintaining overall milk quality through aggressive maintenance of cow comfort and cleanliness, milking procedure and machine function, and aggressive recognition and treatment of clinical cases. Monitoring and recognition of problems relies heavily on bulk tank analysis. Rapid response and correction of deviations allows maintenance of milk quality without excessive culling.

Maintaining Control
Cow Environment: The primary deterrent to receiving milk quality bonuses are elevated SCC due to environmental pathogens during the summer rains. To combat this, corrals are scraped or raked every other day. Manure is removed as needed, however always leaving enough to maintain cow comfort. Wash pen sprinklers are checked at least weekly. High quality post milking teat dips are used to maintain healthy teat skin.

Milking Procedure and Machine Function: Generally accepted guidelines for machine milking are used. Vacuum is set at 12.6-12.8 inches Hg and milking is at 60 BPM and 60:40 milk rest ratio. Pulsators are checked weekly, and the entire system checked monthly. Milkers occasionally clean and dry soiled teats with individual paper towels. All cows are primed prior to machine attachment. Predipping is typically avoided due to labor and time expense. Seasonal predipping and drying with moist cloth towels has been used with apparent success, however this has only been initiated under poor environmental conditions and elevated SCC.

Employee Responsibility - in the parlor: Milkers are trained to have zero tolerance for abnormal milk. They are not required nor allowed to treat cows. Milkers are required to pay attention. Every cow with abnormal milk or inflammation is placed in the hospital for herdsman evaluation.

Employee Responsibility - in the hospital: Herdsmen evaluate all cows pulled from the milking strings for mastitis. Generally this is visual confirmation, and occasionally CMT confirmation. If they agree the cow does have abnormal milk, then a quarter sample is frozen for a minimum of seven days for potential culture. Unless the cow's record indicates that the quarter is chronic and unresponsive, then all abnormal but not inflamed quarters are milked out with oxytocin and treated with approved IM therapy. If there is inflammation or watery milk typical of coliform infection, then animals are treated with systemic antibiotics and antiinflamatories after milkout with oxytocin. Cows with chronic garget, cut teats, or blind quarters are permanently leg banded and quarters are no longer milked. All mastitis cases are recorded on the cows record. The total number of daily mastitis cases are recorded on a day sheet, and in a spreadsheet.

Monitoring Bulk Tank Milk: The dairy is fortunate to have a dedicated milk quality lab nearby that provides rapid results. Every tanker load of milk is cultured for Standard Plate Count, Coliform Count and Lab Pasteurized Count, and Somatic Cells are counted. Mycoplasma cultures are run on one tanker load daily. Deviations from expected normal elicit management responses.

Mycoplasma positive: Culture results are received as early as 3 days post-culture. When notified of a positive culture, string drip samples and frozen clinical mastitis samples are cultured. Typically the offending cow (usually a heifer) is in the fresh string or has a frozen clinical sample. These cows are beefed immediately or moved to a non-milking pen for later beef if residues are at volatile levels.

High SPC: All bulk tank milk with greater than 10,000 SPC is cultured for identification of pathogens. Generally environmental coliforms, streps, and staphs are cultured. A high SPC, in the absence of contagious pathogens, elicits a notification to the herdsman and milkers. Generally, this results in several cows pulled for clinical mastitis the following day, and a drop in SPC.

High Coliform count: It is not unusual to have a coliform spike for 1 or 2 loads of milk, without a readily identifiable cause. Persistent high counts are typically indicative of a dirty cows. Generally the problem is correctable ( broken sprinkler pen). Predipping and drying with moist cloth towels has been used to control environmental pathogens when problems appears to be related to uncontrollable environmental conditions. This requires the addition of a fourth milker.

High LPC: Always a cleanup problem.

High number of mastitis cases: Typically, increased mastitis pulls are associated with environmental changes. However, if causes and effects typically associated with environmental pathogens are not apparent, then all frozen samples are cultured. Occasionally these samples will reveal a Staph aureus, but generally there is a high percentage of no growth, followed by coliforms, and environmental streps and staphs.

Avoiding Contagious Pathogens
No extraordinary efforts are made to avoid contagious pathogens from entering the herd. Bulk tank cultures are used to identify the presence of contagious pathogens. Mycoplasma cows are removed from milking strings immediately and culled as soon as antibiotic residues are eliminated. If Strep. agalactia were ever identified in the bulk tank, then string samples and cultures of frozen clinical mastitis samples would be utilized to identify positive cows, similar to a positive Mycoplasma. Fortunately, Strep ag. has never been identified. If Staph aureus were to be a consistent isolate with a concurrent increase in SCC then a more aggressive staph control program would be instigated. We have occasionally isolated staph aureus but never for more than 2 consecutive bulk tank loads. Those cows with Staph aureus are beefed if milk production is marginal, or moved to the last milking string and identified in her record.

Other Management Actions Used to Achieve Milk Quality Goals
1. Culling: Occasionally high SCC cows are culled, but they are usually marginal milk producers. There are high SCC cows maintained in the herd in order to maintain maximum capacity. Aggressive culling measures to control milk quality have not been utilized due do low beef prices and high replacement costs.

2. PostDipping: Post milking teat dips with high quality emollients are used. Lessor quality teat dips have been tried, but with an empirical impression of increased SCC, decreased teat condition, and increased number of clinical mastitis cases.

3. PreDipping: Seasonal predipping and drying with moist cloth towels has been used to control environmental pathogens. This effort requires additional labor and tends to be eliminated when SCC are well under 180,000 to avoid labor costs. Also, a maximum of 300 towels are used and washed on site at least every two hours.

4. Leg Banding cows with three teats. This is especially important with new milkers. Not all blind quarters are apparent. When machines are placed on blind teats with secretions, there appears to be a substantial decrease in milk quality.

5. Replacement Heifers: County Line Dairies has yet to develop a closed herd, and subsequently all replacements are purchased. Purchasing of cows is avoided. A small herd of milking cows was purchased in 1996, but these were placed in the last milking string until string and bulk tank cultures and individual somatic cell counts indicated the cows were not harboring contagious pathogens.

Common Practices Not Implemented
1. Aggressive culling of chronic mastitis cows or chronic high SCC. There is a 6-7% prevalence of cows over 400,000 SCC for 3 consecutive test periods. These cows have predominantly no growth or coagulase negative Staph spp. They are maintained in the herd due to their high milk production and to the high marginal difference between beef price and replacement cost.

2. Removing udder hair. Caking of manure on the udder is not a grossly apparent problem, however, this will be implemented by this summer.

3. Tail docking: The tail switch is removed at freshening of all cows to avoid spreading manure to the udder, however the idea of docking 5000 adult cows is unappealing and has less compelling benefits in a drylot dairy.

4. Routine drycow therapy: This is perpetually the area of highest criticism. Routinely dry treatment has been eschewed to avoid residue problems. Although, routine dry cow therapy is often considered the cornerstone of a good mastitis control program, it is not always imperative. We remain skeptical that no dry cow therapy is the right thing to do, but have yet to prove a cost effective advantage to routine dry treating. The last comparison study the dairy made found only a decrease in SCC in the first 30 DIM only.

Summary
The goals at County Line Dairy are to maintain year round SCC of less than 180,000, SPC less than 5000 cfu/ml, Coliform counts less than 100 cfu/ml, and LPC less than 180 cfu/ml. Although milk produced at the dairy well exceeds industry standards, there has not been year round success in maintaining self imposed high standards. The heavy reliance upon bulk tank cultures at County Line Dairy, while not without some theoretical risk, has been relatively effective in controlling contagious mastitis. Strep ag. either has not been introduced into the dairy, or the intolerance of abnormal milk has allowed treatment and cure of infections before evidence is apparent in the bulk tank milk. Mycoplasma has been detected and eliminated without apparent spread to other cows, and with a minimum of individual cow cultures. Staph aureus is somewhat tolerated, but does not appear to be a serious problem. Environmental pathogens are the most difficult pathogens to control.

As in any commercial dairy, the ultimate goal is to make the highest profit. County Line Dairy's approach to maintenance of milk quality allows for an efficient work force, minimal individual cow cultures, and management of pens with emphasis on production and reproduction. Although year round excellence is unrealized, the accomplished success in maintaining milk quality is not a result of high culling rates, large drug bills, or time spent culturing individual cows. Success is due to attention to detail, and a rapid response to deviations from high standards.