PHYSICAL AND ETHOLOGICAL FACTORS
Needs of the calfThe famous animal phytotherapist Juliette De Baïracli-Levy6 believes that preventing cows from benefitting from the pleasure and stimulation of nursing their calves is one of the principal causes of mastitis. With suckling calves, Levy makes a distinction between the "psychological" and physical factors.
It is often observed that cows separated from their calves shortly after calving look and call for them. The question of course is whether cows experience a difficult "emotion". If this hypothesis is accepted, however, it would suggest that cows who find the separation more difficult develop mastitis more easily.
On a physical level, the frequency of calf suckling is greater than cow milking. Microorganisms that invade a quarter have very little time to develop. Should cows therefore be milked more often at the beginning of lactation? Slavic researchers47 have observed that the duration and frequency of mastitis was lower during the first two months following calving with cows that nursed their calves for six to ten days as opposed to one hour, two days or four days.
Herd hierarchy
With loose housing or pasturing, a hierarchy is created within the herd, a phenomenon that is even more apparent in goats than in cows. It is possible that the least dominant members of the herd, who are often harassed by the others, have a greater tendency to develop diseases. The advantage of loose housing is that the hierarchical relationships between members is clear. Cows in tied housing can be quite stressed when they find themselves in an exercise yard where relationships between cows are not clear.
Uterus-mammary glands
It has been demonstrated that cows who retain their placentas have mastitis more often that those who do not14. The risk of developing mastitis is increased threefold42. According to German researchers55, mastitis is clearly associated with placenta retention when caused by Actinomyces pyogenes . This type of mastitis represents 17% of cases in Germany. Mastitis that appears within the two months following calving is often linked to uteruses that are not cleaned properly. Discharges of purulent matter dirties the tail and rear end of the animal, and the ground, which favours environmental and, subsequently, udder contamination. Some veterinarians venture further by saying that the reproductive organs may serve as reservoirs of infection. The pathogens thus travel through the blood to the mammary glands. At any rate, beware of placenta retentions!
Rumen-mammary glands
The rumen is a very important organ of the cow, and the health of the other organs often depends on it. When acidosis occurs in the rumen (too much grain in rations for instance), it creates conditions that foster bacteria like Streptococcus bovis and eventually yeasts like Candida albicans. Therefore, although rare, the toxins from these substances can travel throughout the system and favor gram-positive bacteria that attack the udder54.
HUMAN FACTORS
The approach of most laboratory studies is to consider factors in an isolated manner. In mastitis research, there are numerous studies based on farm practices. These studies rely on questionnaires addressed to farmers, analysis results, etc. One such study that was particularly original was conducted in eastern Ireland46, and integrated human factors with herd management factors. The results are given in the table below. It should be noted that the farmer's age and teat washing did not emerge as determining factors in the incidence of mastitis during the study.Table 3 - Human factors and milk production
| Characteristic | Associated factors |
| Low somatic cell count | Geographical position of the farm, treatment of dry cows, replacement cows produced on the farm, positive attitude towards milking, family enterprise. |
| High somatic cell count | Small herd, irregular maintenance of milking equipment, lack of bedding on cement floor, udder washing of dirty cows only, little ambition. |
| Low bacterial count | Treatment of dry cows. |
| High bacterial count | Tied housing, obsolete milking equipment, short withdrawal period after antibiotic treatment, limited inclination to seek out information. |
| High milk yield | Average herd, treatment of dry cows, average inclination to seek out information, elimination of cows that are too susceptible. |
| Low milk yield | Lack of hot water at milking, use of one cloth only for all cows, infrequent meetings with other farmers, strong will to continue traditional family farming, no vacation. |
DIAGNOSIS
To diagnose mastitis, it is necessary to learn how to distinguish between the symptoms of the various types of mastitis infection (see Tables 1 and 2 on page XX and XX respectively). The key points to remember are as follows:Since these symptoms are often absent, particularly in cases of subclinical, subacute or chronic mastitis, only half of all mastitis infections, at best, can be detected through observation. Some tests may therefore also be useful, notably cell counts, bacterial identification and the California Mastitis Test (CMT).
SOMATIC CELL COUNT
All producers registered in a dairy record of performance are familiar with somatic cell counts. Sometimes wrongly referred to as white cell counts, this type of test includes all somatic cells, including white cells (or leucocytes) and epithelial cells. When swelling occurs, the cow's immune system reacts by sending leucocytes to destroy the foreign bodies. The somatic cell count in the milk may thus indicate if a cow is fighting infection.Cell counting came into use largely to ensure that milk from a given herd was fit for human consumption. It is also a highly useful test for mastitis detection, albeit lacking in certain respects.
First, cell counts do not distinguish between leucocytic and epithelial cells. For example, for normal milk with a cell count of 50,000 cells per ml, there may by 20% leucocytes and 80% epithelial cells, whereas mastitis infected milk with a cell count of over 500,000 cells per ml, contains 90 to 95% leucocytic cells. It would be easier to determine if a cow was fighting infection if only the leucocytic cells could be counted. Since the count does not make the distinction, it is difficult to interpret the results of a count, especially with average numbers. With high cell counts, the so-called "millionaire" cows, the diagnosis is clearer and is indicative of mastitis.
Second, there is tremendous variation between the number of somatic cells with or without mastitis. The number of somatic cells in milk is generally higher in summer months, higher at the beginning and end of lactation and increases with the age of the cow. It also depends upon the genetic history of the cow and bull13. Moreover, an increase in somatic cells may be linked to a functional disorder of the reproductive organs. Even with a sampling and count that are properly carried out, a difference of 25% from one day to another can be expected without the circumstances of the herd having changed29.
Third, cows in one herd react differently to infection than cows from another herd. For example, Natzke29 reports that the average cell count of milk from quarters infected by Staphylococcus aureus was 6,700,000 in one herd and 900,000 in another. In the same study, the non-infected quarters had a cell count of 600,000 in one herd and 150,000 in the other.
Finally, when a cell count is high, the animal or the milk generally shows obvious symptoms of mastitis. The test therefore tells us nothing more than our attention to symptoms.
Despite these shortcomings, the somatic cell count remains an important and practical tool for measuring the general health of a herd or individuals. Natzke29 believes that cell counting is particularly useful for evaluating the long-term health of a herd. Observing cell count trends from one year to the next serves to evaluate if any progress has been made, or if the situation is stable or deteriorating.
BACTERIAL IDENTIFICATION AND COUNTING
In several states and provinces, bacterial counting in milk is done monthly for all dairy farms. It consists of evaluating the size of populations of different microorganisms in milk samples.The identification of microorganisms present in the milk is sometimes useful on the farm to determine exactly what species of bacteria are responsible for the infection. This is the case for example when several cows have the same symptoms. These tests are done at government pathology laboratories.
PREVENTIVE MEASURES
MILKING PROCEDURES
Sanitary milking habits are important to avoid the spreading of germs or their proliferation. The purpose of hygiene is to prevent the transmission of germs from one teat to another on one cow or from one cow to another.There is no need to get overly excited about germs... but why provoke them?
Pasteur admitted at the end of his life that "the terrain is everything, the microbe is nothing", meaning that pathogenic microorganisms could not cause disease in a healthy animal or plant (well fed, etc.). Although optimum health is always the ultimate goal, it is not always easy in to attain in herd management. Therefore, in the meantime, a little hygiene can't hurt!
Udder washing
Washing the udder is hygienic and has a stimulating effect on milk flow. Adequate washing is especially important to prevent environmental mastitis, caused by coliforms and other microbes from contaminated environments. Badly washed udders contribute to the transmission of microbes rather than to their destruction.
According to Pankey33, the lowest bacterial count in milk is obtained by washing the udder in the following fashion:
Note that teat dipping before milking in addition to drying off does not give better results than drying alone, and it increases the risks of contamination of the milk by disinfectants.
Udder washing
This is a recipe for washing udders used by Daniel Lapointe, an organic dairyman from Quebec. Although the antiseptic value of this formula has never been scientifically tested, he has been using it for many years with good results. It consists of mixing 13 litres of hot water, 1 drop of pine oil, 1 capful of peroxide and 1 ounce of clay.
Foremilking
Removing a little milk by hand before machine milking serves to stimulate milk letdown and to obtain a milk sample containing a high microbial count. A filter cup is used to detect abnormal looking milk (lumpy, etc.).
Milking sequence
It is important to milk infected cows last. If possible, milking sequence should be as follows: first lactation cows, normal cows, cows with a high cell count and then infected cows.
Other measures during milking
It is important to milk completely. With modern milkers, as long as they are well adjusted, the risks of forcing the entry of microbes at the end of milking greatly diminish. The chances of bacteria entering the udder can be reduced by diminishing the amplitude of the vacuum changes and the vacuum change speed on the teats12. To do so, a good vacuum reserve and appropriate piping are necessary. Furthermore, the milker must not slip on the teats and the milkers must be removed carefully.
Risk of infection may be diminished if milking is finished by hand, although not realistic for an entire herd. De Baïracli-Levy6 even suggests massaging the udder after milking and hitting it up and down in the same way that calves do.
It is important to milk twice a day, even with cows that do not produce a lot. The longer the milk remains in the udder, the greater the risk of infection. The first squirts of milk must not go on the ground as this will contaminate the bedding and floor.
Postmilking teat dipping
Using a disinfectant teat dip after each milking is a means of diminishing by about 50% the risk of infection by contagious microorganisms like Streptococcus agalactiae and Staphylococcus aureus. Teat dipping prevents populations of these microbes from developing sufficiently between milkings. Teat dipping also discourages flies.
It is important that the teat dip contain up to 10% of emollients to increase the suppleness of the teats: oils, glycerine, lanoline. Healthy supple skin is an extra insurance against entry of bacteria to the udder. Staphylococcus aureus does not persist on healthy skin.
Teat Dip
This is another recipe by organic dairyman Daniel Lapointe. You simply mix four litres of water, 5 ml of lavender oil, 5 ml pine oil, 2 ml eucalyptus oil, 12 ml cottonseed oil (available in drugstores) and 5 ml methylene blue.
Cleaning equipment after milking
It is obviously important to clean and disinfect equipment after milking. Cider or corn vinegar and peroxide are used by some producers as alternatives to phosphoric acid and chlorine
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