Most devastating disease-Mastitis is inflammation of the mammary gland caused by microorganisms. The mammary gland is damaged due to toxins released by the bacteria. White blood cells (leukocytes) are released into the mammary gland in response to bacterial infection in the mammary tissue. Mastitis occur by chemical, mechanical or thermal injury to mammary gland. It causes massive economic losses with a low incidence of clinical mastitis. Mostly clinical mastitis cases occur in the first trimester of lactation. Here, stress, negative energy status and metabolic disorders are important risk factors.
Pathogens causing mastitis include Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus agalactiae, Streptococcus uberis, Brucella melitensis, Corynebacterium bovis, Mycoplasma spp, Escherichia coli (E. coli), Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter aerogenes, Pasteurella spp, Trueperella pyogenes, Proteus spp.
- Contagious mastitis
- Environmental mastitis
Mastitis is often transmitted by regular contact with the milking machine and through contaminated hands or materials, bedding and feeding in same feeder.Environment influences the numbers of bacteria that areexposed to cows. Cows have udderinfection at different ages and stages of the lactation cycle. Therefore,the cow plays an active role in the development of mastitis.
Source: NDSU Extension Service publications in the mastitis control programs series
Mastitis may be classified as clinical mastitis, sub-clinical mastitis, per acute mastitis, acute mastitis, sub-acute mastitis and chronic mastitis according to the clinical symptoms or depending on the mode of transmission. Clinical symptoms of disease can be identified by abnormalities in the udder such as swelling, heat, redness, hardness, or pain. Other indications of mastitis may be abnormalities in milk such as a watery appearance, flakes, or clots. In subclinical mastitis, no any visible signs of infection or abnormalities seen.
Somatic cells are indicator of both resistance and susceptibility of cows to mastitis. The milk somatic cells include 75% leucocytes, i.e. neutrophils, macrophages, lymphocytes, erythrocytes, and 25% epithelial cells. Erythrocytes can be found at concentrations ranging from 0 to 1.51×106 /ml. Mainly somatic cells are milksecreting epithelial cells that enter in the mammary gland in response to injury or infection caused by bacteria. Somatic cell count (SCC) should be optimum viz. more than 2 ×105/ml of milk but not 5×105/ml of milk which indicates sub-clinical infection. Low SCC may be predisposingfactor for udders for infection particularly by coliforms. Initial low somatic cell counts(SCCS) indicate udder immunity in dormant phage.
High yielder in a herd have great chances of genetic vulnerability to mastitis. The pure breeds and cross breed heavy yielders are genetically more vulnerable than the local medium yielder. Multiparous cows are more vulnerable to intra-mammary infection due to immune incompetence. Mastitis are lower in Jerseyas compared to Holstein cattle. Genetic factors for mastitis are also seen in higher amount onrelative individuals than the general populations. The risk of mastitis increases with the increase in parity, attributable to mammary immune comptonization, high milk yield and peak stage of lactation.Deep and drooping morphology of udders are also associated with more incidence of mastitis in cows.
Stress is one of the potential risk factor for mastitis. Nutritional, parturition or lactation stress, all affectthe udder health by declining local and systemic resistance to infections. Stress often decline udder defense mechanism for intra-mammary infections. Nutritional stress occurs especially due to deficiency of micronutrients such as trace minerals (copper, zinc, selenium, cobalt, chromium, iron) and antioxidant vitamins (A, C, E, β- Carotene), amino acids (L-histidine, lysine). Certain bioactive ingredients (Lactoferrin, Probiotics) decline the udder immunity both at cellular and humoral level in cows during lactation. Normal zinc level is essentially needed for optimum cell mediated immune responses. Staphylococcal mastitis occurs due to deficiency of trace mineral like copper, zinc and iron. An optimum level of macro elements such as calcium is also essential for udder immunity during parturition and lactation stress. Deficiency of ascorbic acid concentration causes mammary tissue lipid peroxidation(bovine mastitis). Vitamin A and E supplementation in diets improve mammary gland host defense and effective neutrophil recruitment. Humoral and cellular factors are important for inhibiting bacterial growthof species likestreptococci, staphylococci and coliform organisms. Lactoferrin, immunoglobulin and transferrin like soluble factors in milk prevent bacterial multiplication. Lactoferrin is bacteriostatic for a variety of bacteria with its iron chelating ability. The main function of immunoglobulins is foropsonization of microorganisms during phagocytosisin the bovine mammary gland. Opsonization is the process by which a pathogen is marked for ingestion and eliminated by a phagocyte. Opsonization involves the binding of an opsonin(antibody) to an epitope on an antigen. After opsonin binds to the members, phagocytes are attracted to the pathogen.They also play a role as antitoxin. Intercurrent diseases, stress and malnutrition reduces the defensive response of these bioactive components in affected dairy herds.
Poor quality silage negatively affects the immune system of animal. Pseudomonas and Proteus cansurvive the high temperatures in silage. Silage contaminated with these microbes may be a source of mastitis. The mold formation during hay preservationas well as mycotoxinsin feed also affect mammary glanddefense mechanism against bacteria.
Prevention and Control Strategy
Treatment is possible with long-acting antibiotics, but milk from such cows is not marketable until drug residues in milk. Antibiotics may be systemic (injected into the body), or forced upwards into the teat through the teat canal (intra-mammary infusion). Depending on the severity of the condition, pathogens can reoccur infections; they should be used in conjunction with a mastitis prevention and control program (MPCP).
Good nutrition, proper milking hygiene, and culling of chronic infected cows should be done as control measures. Cleaning cows and dry bedding decrease the risk of infection and transmission. Daily routine hygienic practice should be adopted in dairy farm. Dairy workers should wear rubber gloves and milking machines should be cleaned to decrease the incidence of disease. Usually teats dipping or spraying such as an iodine spray and wiping teats dry should be adopted as good management practice. Mastitis can occur after milking because the teat holes close after 15 minutes and the cow sits in a dirty place contaminated with dung and urine.After milking, teats must be dipped with iodine propylene glycol that acts as a barrier between the opening of teats and the bacteria in the air. The milking machine should properly synchronize with vacuum pressure of milking machine.
Role of Nutrition in Mastitis
Nutritional supplements prevent mastitis via modulation of immune system of cows. At the onset of lactation; nutritional management, metabolic stress, a protein or energy deficient heifer may suffer from poor defense mechanism in specific situations. Antioxidants and trace minerals influence the immune function and health status in transition dairy cows. Cows are more resistance to mastitis infections by dietary supplementation of vitamin E, vitamin A and minerals like selenium, copper, and zinc. Lactating cows are more prone to mastitis during calving. Keratin plug in the teat breaks down. Vitamin A and Zinc affect the health ofepithelial tissues, physical defense barriers of the udder and alter the quality and quantity of keratin plug. Copper, zinc, selenium, and vitamins A and E influence the phagocytic cells functions in cattle. The killing ability of immune cells is increased by nutritional supplementation with Vitamin E, which improve neutrophil function in dairy cows.
Likewise, copper deficiency in dairy cow may result in deficiency of white blood cellswhich impair the immune system to defense against disease. Further, copper is also an important part of superoxide dismutase, that protects cells from the toxic effects of oxygen metabolites released during phagocytosis.
Mastitis is a multi-factorial disease in dairy farm. Cow itself, bacteria, management and the surrounding environment all collectively play a role in development of mastitis. Subclinical mastitis (SCM) is of great economic importance to dairy farmers because it results in reductions in milk yield and undesirable changes in the milk composition.Mastitis control programs, particularly teat dipping, dry cow therapy and effective treatment of clinical mastitis must be practiced to reduce the high incidence of mastitis in dairy herds. Rations should be formulated to meet the NRC requirements for better body immune.