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Somatic cell count

Reducing Somatic Cell Count in Dairy Cattle

Published: February 27, 2012
By: Dr. Michael Looper (University of Arkansas)
Somatic cell count (SCC) is the total number of cells per milliliter in milk. Primarily, SCC is composed of leukocytes, or white blood cells, that are produced by the cow´s immune system to fight an inflammation in the mammary gland, or mastitis. Since leukocytes in the udder increase as the inflammation worsens, SCC provides an indication of the degree of mastitis in an individual cow or in the herd if bulk tank milk is monitored.
An inflammation of the mammary gland may result in clinical mastitis with varying degrees of visible signs of the disease or subclinical mastitis where no visible symptoms occur. Pathogenic bacteria entering the udder via the teat orifice move into the teat canal and cause an infectious response. Contagious bacteria (Streptococcus agalactiae and Staphylococcus aureus) are more difficult to control than environmental pathogens such as coliform. The goal of a sound mastitis control program is to minimize bacteria that enter the udder plus minimize the growth of bacteria in the udder.
Monitoring SCC is especially critical in diagnosing cows with subclinical mastitis since no visible signs of an inflammation are observed by the dairy producer. Culturing bacteria in the milk of an individual cow may be used to determine bacteria causing mastitis if a more specific diagnosis is needed. Bacteria are sensitive to specific antibiotics, which also may be indicated by the culture.
Methods to Monitor SCC
The most common methods of monitoring SCC in bulk tank milk are actual SCC from the health depart­ment or milk plant and the Wisconsin Mastitis Test (WMT). In an individual cow, the actual SCC or linear SCC score from Dairy Herd Improvement (DHI) records and cow-side tests such as the California Mastitis Test (CMT) indicate SCC. Also, some milk process­ing plants will measure SCC on samples of milk from individual cows. Table 1 shows that all methods can indicate SCC. However, the CMT is a subjective measure and may vary from dairy producer to dairy producer.
Importance of Decreasing SCC
Federal law allows milk to be sold only if the bulk tank has a SCC of less than 750,000/ml. The primary reason for dairy producers to reduce SCC is because SCC relates to milk losses due to mastitis (see Table 1). If they can reduce their SCC from 600,000 to 200,000 cells/ml, they can decrease milk production losses by 600 pounds per cow per year. In a 100-cow herd, these losses amount to $7,500/year if milk is valued at $12.50/cwt.
Milk processors want a decreased SCC because it reflects increased cheese yield and keeping quality of the milk. Marketing agencies now pay premiums for milk with low SCC. If a premium of $0.25/cwt is paid for decreasing SCC from 600,000 to below 300,000 cells/ml, this premium totals 15 cents per cow per day for a herd averaging 60 pounds milk/day or $5,475/year in a 100-cow herd.
Reducing Somatic Cell Count in Dairy Cattle - Image 1
Methods to Reduce SCC
There are two methods of reducing SCC. The first method, culling cows, is a short-term solution which can quickly reduce SCC in the bulk tank. The second method, controlling mastitis, is a long-term solution which should be the basis of a sound management program. The most economical method to determine SCC is testing monthly milk samples from each cow.
Culling Cows
Cows with a very high SCC that do not respond to antibiotic therapy or that have chronic mastitis may have to be culled from the herd. Usually, cows with high SCC have mastitis that is caused by contagious bacteria, primarily Staphylococcus aureus but also Streptococcus agalactiae. The most common source of contagious bacteria is other infected cows; whereas, environmental pathogens are most com­monly isolated from recently calved and dry cows. These bacteria, especially Staphylococcus aureus, often do not respond to routine antibiotics and should be cultured to determine a more appropriate antibiotic. If the cow then does not decrease in SCC after more extensive treatment, she should be culled.
Culling 5 percent or fewer of the cows in your herd can markedly decrease SCC in the bulk tank if these cows have very high SCC. For example, if the bulk tank average is 1,000,000 cells/ml and one average-producing cow with a SCC of 10,000,000  cells/ml is culled from a 100-cow herd, the bulk tank average decreases to 909,000 cells/ml. If five cows with an average SCC of 7,500,000 cells/ml are culled from a 100-cow herd, the SCC in the bulk tank decreases to 658,000 cells/ml.
The critical decision in culling cows to reduce SCC in the bulk tank is to determine the individual cows that have the high SCC. For most producers, DHI records can provide this information in the most efficient and economical manner.
Prevention Through Nutrition
Increasing a cow´s resistance to mastitis pathogens on the teat-end is an important component of immunity in the dairy cow. Nutrition is involved in maintaining immunity. Inadequate energy or defi­ciencies affect resistance. Diets may be deficient in nutrients that are related to immunocompetence. A balanced ration with proper amounts of minerals and vitamins improves the ability of a cow to ward off bacterial challenges. Recent research does show selenium and vitamin E are related to healthy tissue in the mammary gland.
Prevention Through Sanitation and Management 
Improving sanitation to decrease mastitis is simply keeping the udder clean and free of pathogenic bacteria that cause mastitis. Major teat contamina­tion can be avoided by eliminating mud and preventing wading in ponds.
Bedding must be dry at all times. Straw and sand are the beddings of choice. Avoid green wood sawdust. Clean sod or new bedding is essential for all springing heifers and dry cows as well as milk cows. The grass sod in the pasture or drylot should be free of mud and objects such as sticks that damage the udder.
Special care must be exercised with heifer management. Calves should be reared in separate pens to avoid nursing. The fly population must be controlled to decrease the spread of mastitis-causing bacteria. Springing heifers should be separated from cows.
Dry Cows and Springing Heifers
Risk of intra-mammary infections is greatest during the early and late dry period when pathogens are not flushed out on a day-to-day basis. Infection rate in dry cows is directly related to the bacterial population on the teat-end. Protective sealant dips are beneficial for teat protection and should be used after treating dry cows. Extreme care must be taken to prevent contamination before sealing teats.
Dry cow treatment of all quarters of all cows is recommended, but the largest danger with any intra­mammary infusion is recontamination. The teat-end must be cleaned and sterilized with a pre-dip before insertion of the dry-treatment tube. Insertion of the tube through a drop of pre-dip to a maximum depth of 3/8 inch reduces bacterial contamination entering the teat canal and minimizes damage to the keratin teat plug at the end of the teat. Dry cow treatment helps eliminate and prevent new infection during the dry period. During the late dry period, be careful to guard against new infection. This springing period is a vulnerable time as dry cow therapy has dissipated and mammary tissue is in a growing phase without antibiotic protection. Colostrum is an ideal medium for growth of patho­genic bacteria.
Springing cows may be retreated if needed, but caution must be taken to prevent contamination. Monitoring dry cows for inflammation after treatment is necessary. Regenerating udder tissue must be monitored for swelling and inflammation. Prior to calving, dry cow teats may be cleaned and dipped as needed. The seal at the end of the teat should not be broken during the teat cleaning.
Lactating Cows
Monitor each cow monthly with SCC from DHI records for a mastitis prevention program. Follow proper and sanitary milking procedure with proper equipment. The procedure is:
1. Wash teats and dry.
2. Pre-dip for 30 seconds to kill bacteria on the teats.
3. Dry teats. 
4. Squirt first milk which is highest in bacterial count.
5. Check and record abnormal milk.
6. Apply milking units.
7. Remove units at completion of milking.
8. Post-dip.
9. Allow teats to dry in cold weather.
10. Feed immediately after milking to keep cows standing to allow the sphincter muscle to close the opening at the end of the teat.
11. Separate cows in heat from the herd so that udders of cows are not injured while mounting other cows.
To minimize contamination of milk with drug residue, use only legal medication. Properly mark all cows treated with any medication for milk with hold­ing. Follow withdrawal time required. Test treated and fresh cows before allowing milk into tank. Call the milk fieldman to test milk for antibiotics if you may have accidentally put contaminated milk in the bulk tank.
Stray Voltage
Stray voltage is damaging electricity from many sources in milking parlors that can be grounded through a cow. A small voltage can cause production of epinephrine, which blocks the effect of oxytocin that is required for milk letdown. Normal mechanism of milk letdown allows most of the milk to be removed. Incomplete removal of milk causes mastitis due to rapid bacterial growth. Frequent milking has been used to wash out pathogenic bacteria. When abnormal bacteria are observed, stray voltage should be checked by an electrician and the power-company representative. Common causes are 120-volt motors, static electricity, off-farm voltage leak and ungrounded motors. New construction should have a grid installed beneath the floor to prevent stray voltage from grounding through the cow. Use wellgrounded 220-volt motors in all areas where possible to keep both 110 legs of the incoming service balanced and reduce the likelihood of voltage drift. Sheet iron roofing generates more static electricity during windy conditions.
Summary
Producing milk with low somatic cell counts is a necessary and profitable management tool. Maintain­ing healthy cows through proper nutrition is the first requirement. Practices contributing the most to decreasing SCC are controlling mastitis and culling cows with a high SCC count. Records maintained by DHI with SCC contribute to profit by monitoring results of management procedures that decrease exposure of teat-ends to pathogens.
Proper milking practices including teat dipping, sanitary management and dry cow therapy based on cultures of individual quarters are the most impor­tant components of a mastitis control program. Lowering somatic cell count from 600,000 to 300,000 increases milk sales by $50 per cow per year, which is a small fraction of the total benefit. Some milk processors have incentive payments for lowering SCC in milk.
Always use legal medication to treat cows with mastitis and then withdraw the milk from market for the required time.
This article was originally published in The University of Arkansas´ Division of Agriculture´s website. Engormix.com thanks the author and the university for this huge contribution. 
Related topics:
Authors:
Dr. Michael Looper
University of Arkansas (USA)
University of Arkansas (USA)
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Alfredo J. Escribano
Orffa Excentials
16 de abril de 2015
Dear all, From the animal nutrition side, the use of Copper and Zinc (preferably chelated with methionine or glycine) have shown to reduce SCC dramatically. The company NOREL Animal Nutrition (www.norel.es) counts with really good chelated minerals with methionine and or glycine. Regards, Alfredo.
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Jasmer Singh
23 de junio de 2014
Hi Drs Viswanath and Reddy, Please go through our article on" Pathobiology, etiology and treatment of ...mastitis" which appeared in this forum . It explains most of the problems of mastitis and its control. Jasmer
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Viswanatha Reddy
29 de noviembre de 2012

In India hand milker usually uses cold water to wash the teats and also fails to scrub the teat pore before milking. Milker is supposed to use warm water to wash the teat and rub the teat pore to dislodge any dirt accumulated. Many milkers knuckle the thumb and strip out the milk, if the teat is not lengthy especially first calver the milking is done by stripping the teat from base of teat to the tip of the teat especially in the later situation too much accumulation of blood at the teat pore causes the callus formation. When a machine is used for milking over milking or creeping up of liners can also result in such callus formation a predisposing factor for sub-clinical or clinical mastitis. In majority of milking machines it is not possible to turn off the vacuum for individual teat when the milk out flow has stopped and in few instances even without proper turning off the vacuum the cluster is removed and possibility of entry of air in to the teat cistern can be a factor to increase somatic cell count. All teat dips are not 100 percent efficient in their antiseptic properties. If a spray is used the milker may not spray 100 per cent efficiently for this reason teat dip is preferred by the dairy mangers. In India there is no suitable intramammary infusion to do DRY COW THERAPY and if the organisms can enter in to the teat cistern on the last day of milking they can remain in the udder up to 200 days (information from Hoard's dairyman) and when the resistance of the animal comes down they can cause sub clinical or clinical form of mastitis.
In India there is no suitable intramammary infusion to do DRY COW THERAPY and if the organisms can enter in to the teat cistern on the last day of milking they can remain in the udder up to 200 days (information from Hoard's dairyman) and when the resistance of the animal comes down they can cause sub clinical or clinical form of mastitis.
All these predisposing factors have to be managed to reduce somatic cell count. The other nutritional factors and stimulating the immunity system are required to reduce somatic cell count. Vaccinations unless they are done in late pregnancy followed by booster vaccination dose and at specified subsequent intervals it is not worth.
Estrogen is required for the muscular strength of myoepithelial contraction and for the milk ducts while progesterone has a role on the secretary tissue of udder. Estrogen is required for the muscular tissue of uterus especially in pregnancy for the hypertrophy of muscular fibers and progesterone for the uterine endometrial secretions. Clinically it is well documented when the uterus is infected there is a drop in milk production. In sub clinical and chronic clinical mastitis condition animals do become repeat breeders. The flux of these two hormones may have a role in somatic cell count.

Best Regards,
V.N.Viswanatha Reddy

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Jasmer Singh
13 de noviembre de 2012

Hi Leona, This salt is usually available with the firms dealing with chemicals ( NOT MEDICINS AS CHEMISTS DO). This salt should be used @ 30gms dissolved in about 250ml of tap water and given once daily as a drench. Usually the recovery depends on the severity of the disease and is resolved in 3-5 days. However, in acute and or/recurrent cases of mastitis the preferable treatment is through I/V initially as 5% solution in sterille normal saline @ 50ml morning and evening and then followed by oral dose, if required, for one or two days for complete cure. I would rquest you to please contact me after giving this treatment to your animals for my information.

Regards Jasmer

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Jasmer Singh
6 de noviembre de 2012

Hi,
The increase in SCC of milk is directly responsible for the increase in the pH of milk in the udder ( normal pH of udder milk is ~6.5 while that of mastitic milk usually ranges from 7.0-9.0). The modus operandi of SCC has already been explained in our article  Pathobiology, etiology and treatment of mastitis in Engormix.com. Administration of tri-Sodium citrate @ 30gm daily orally in water or a 5% sterille solution of this salt in normal saline I/V clears the infection from the udder and the SCC is lowered automatically. This happens due to the equiliberation of the Ca++ and H+ in the udder due to citrate administeration which regulates the normal pH (~6.5) of udder and scavenges off the infectious agents due to acidic medium.

Therefore, always check the pH of udder milk as a routine to monitor the SCC and proceeed for its control. The pH can be easily and economocally checked on the spot by graded pH papers or by a simple pen-pH meter. Furthermore, the Citrate content of udder milk (range 130-180 mg /100ml) should be determined regularly at times from animals at the farm and replenished whenever required. 

K S Dhillon and Jasmer Singh

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Praful Kumar
2 de noviembre de 2012

Excellent article with comprehensive analysis. we have tried a different approach to reduce somatic cell count in milk during advance subclinical / clinical mastitis. We know that conventional treatment using systemic and intra-mammary antibiotics have some limitations. like risk of antibiotic residues and withdrawal period. We have used therapy that activates and strengthens "Natural Defense Mechanism" of the udder system using Non-antibiotic polyherbal gel "Mastilep" with Anti-inflammatory, Analgesic, Antimicrobial actions with Boosting of local immunity. Recently 5 dairy cow wereTested using this polyherbal gel just by two times topical application on the udder. they after 5 days report came that stiffness and congelation (+++) became very normal. After few days when they cheked the Somatic Cell count it was 1.4 X 10^5 where as earlier it was more than 6X 10^5. Please note that in Japan milk having less than 3X10^5 SCC will fetch premium price where as farmers have to give penalty when SCC is more than 3.

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Viswanatha Reddy
1 de noviembre de 2012

This is with reference to Peter James Lester comment:

The balance of electrolytes is main componant, conjugated with protein and energy requirement to reduce SSC. When a group of animals are subjected we have to group animals on their growth (in first calvers), production and reproduction status. All nutrients have to come in to feed or fodder through soil. We suppliment to few animals Vitamin E and Selenium or bypass fat and get good results (experimentally not possible to include large number of animals). How much it costs per animal? We have to adopt for all stages of milking animals and looking in to the economics of an agricultural farmer who maintains 1 to 4 animals (he is the major contributor for milk production in India) our purpose gets defeated as he says it is not economical and the buyer is not accepting milk on SSC basis. Our knowledge we will be of use for future generations when a buyer demands for the quality milk towards that we do research, keeping in mind the health of the animal.

Our dairy farmers are not getting analysis of soil, feed stuffs and fodders (their composition may vary from season to season). As Dr. Peter James Lester said by adopting a feed amalgamation computer program, and carry out our experiments and the resluts are conveyed from lab to land we will be helping an average dairy farmer of India.

It is a request to Dr.Peter James Lester to inform the cost of the program he has developed so that we can inform the interested large dairy farmers, sheep farmers, veterinary colleges, Livestock research institutions in India for future course of action.
V.N.Viswanatha reddy,
Former Professor of Animal Reproduction,
Veterinary college, Bangalore, INDIA

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Jasmer Singh
28 de febrero de 2012

Dr Micheal
The objective of the article is good and well explained to get maximum benefit out of milk production units. However, the modus operandi of rising SCC in milk is of great concern and needs some more explaination as to why this rise occurs and degrades the quality of milk? First of all we should know why the influx of leukocytes into milk is triggred. I would like to unravel the situation of this mechanism breifly as below:

During lactation the tight junctions between blood and milk remain closed thus there is no migration of constituents of milk and blood from either side. The normal pH of milk is ~6.50 and that of blood is 7.40 in dairy animals(cow and buffalo). The normal pH of milk in udder is maintained by Citrate through its buffering effect by equiliberating the Ca2+ and H+ throughout lactation. The other function of citrate in udder is sequestration of Ca++ which prevents its clumping and preserves the fluidity of milk. Whenever there is any disturbance in the synthesis of citrate in the udder the whole system goes haywire and calcium forms flakes which behave like Lime and injures the secretory epithelium. Due to injury thus inflicted by calcium there is swelling of the sorrounding areas of the udder resulting in leaky tight junctions. This leakage prompts the exchange of ions as Na, K, Cl, Hco3, Ctrate etc., between milk and blood bringing the pH of milk equal to that of blood i.e., alkaline(7.20 or even higher). The lesion in the udder created by calcium and alkaline pH of milk provides most conducive environments for the estabilishment of environmental organisms setting-up infetioous mastitis. Thereafter, the body defense is triggered driving inflammatory cells to the site of infection through compromised leaky tight junctions and an explosive inflammatory reaction ensues with involvement of immunological events. This whole mechanism occurs very fast culminating into varying degrees of mastitis which manifest as high SCC in milk. The other biomarkers of this episode are high milk pH with relative lowered cocentration of Citrate along with other clinical signs of Mastitis.
We have cured such cases of mastitis in cows and buffaloes effectively with the replenishment of Citrate deficiency by administering tri-Sodium citrate orally or I/V(For details See our article " Pathobiology, etiology and treatment of mastatis in buffalo by KS Dhillon and Jasmer Singh in Technical articles of ergonomix.com).On the basis of our research and by many others on this subject some Pharmaceuticals have marketed their products with tri-Sodium citrate as the main ingredient for the prevention and treatment of mastitis in dairy animals and currently being used most succesfuly in the field.


KS Dhillon and Jasmer Singh (Rtd. Profs. PAU Ludhiana).

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Tariq Mirza
20 de octubre de 2014
Hi , Can any body share the role of Lauric Acids and Glycerol in reducing the Level of SCC in milk ?
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Dr shivaji Mehatre
23 de junio de 2014
Dear Sir, What is the formula for the SSC . Some author count average cell count X microscopic factor X 8000 or 50000. Please advise correct formula for the SSC. Thanks and regards. Dr Mehatre S N
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