2. BOVINE MASTITIS. Bovine mastitis is a worldwide phenomenon with integrated economic

Transcription

1 BOVINE MASTITIS

2 2. BOVINE MASTITIS 2.1 Introduction Bovine mastitis is a worldwide phenomenon with integrated economic component for the past century. This scientific mystery has been continually pursued to understand the pathobiology in order to unravel the control and preventive mechanisms. Though the causative pathogenic micro-organisms were identified in 1887, the major pathogens were established during 1940s. Albeit anti microbial therapy was made available by 1945, it was not effective for all mastitis pathogens. The recognition of the multi-factorial etiology of bovine mastitis in the 1960s paved way for further research in mastitis. Despite improvements in the breeding of disease resistant cows, mastitis continues to be a costly disease and the major economic issue for dairy farmers. In India the economic loss due to mastitis is about 57.5 crore per annum which can be ascertained from the estimation that mastitis reduces milk by 21% and butter fat by 25%. In addition to the economic loss, the consumption of mastitis affected milk is harmful to man hence, a major public health hazard to the whole humanity. 2.2 Review of Literature Milk production, economics and Mastitis India is the second largest milk producer in the world, but the per capita availability of milk still remains half of the world average, demanding strategic intervention (Table 2.1 and 2.2 a and b). One of the reasons for low productivity is poor animal health, particularly, infectious diseases like mastitis. In India, the contribution of Livestock sub-sector to the Agricultural GDP increased from

3 13.9% in 1980 to 33.6% in 2002 indicating the importance of livestock sub- sector in the growth of the agricultural sector. Table 2.1: World Top 10 Cow's Milk Producing Countries in 2009 (Tonnes) USA 84,189,067 86,159,600 85,859,400 India 43,481,000 44,100,000* 45,140,000 China 35,574,326 35,873,607 35,509,831 Russian Federation 31,914,914 32,099,700 32,325,800 Brazil 26,944,064 27,579,400* 29,112,000 Germany 28,402,772 28,656,300 27,938,000 France 24,373,700 24,516,300 23,341,000 New Zealand 15,618,288 15,216,800 15,400,000 UK 14,023,000 13,719,000 13,236,500 Poland 12,096,005 12,425,300 12,447,200 World 571,403, ,428, ,401,740

4 Table 2.2: a. Milk production and b. GDP contribution by live stock sector in India a. b. Year Producti on (Million Tonnes) Per Capita Availabi lity (gms/da y) Year GDP GDP (Agriculture) GDP (Livestock Sector) Rs. % Share Rs. % Share ,971,46 476, ,389, , , ,952, , , ,581,422 16, , ,282, , , ,133, , , Bovine industry is more specialized and most dairy cattle have been bred for production of large volumes of milk. Domestic cows can live up to 20 years 9

5 and after certain age the cow is culled and marketed in meat industry. With milk production of about 78 million tons during , India is positioned as the second largest milk producing country. Of late market for milk products is showing a steady increase, hence, the dairy sector offers a good opportunity to entrepreneurs in India. Milk production alone involves more than 70 millio n producers, each raising one or two cows/ buffaloes primarily for milk and milk products. Mastitis is single, largest problem in dairy animal in terms of economic losses in India The Mammary Gland System In order to understand mastitis pathobiology, the mammary gland has been studied with respect to its anatomy, physiology, and the genomics (Ogorevc et al., 2009). The cow, sheep and goat have the simplest mammary gland system. Development of the mammary gland in the sheep and goat is identical to that of the cow. The interior of each quarter is composed of a teat cistern, gland cistern, milk ducts and glandular tissue (Fig 2.1a). The secretary portion known as the glandular tissue contains millions of microscopic sacs called alveoli (Fig-2.1b). Each alveolus is lined with milk- producing epithelial cells and is surrounded by muscle cells which contract and squeeze milk from the alveolus during milking. Blood vessels bring nutrients to each alveolus where the epithelial cells convert them into milk. Milk accumulates in the alveolar spaces, milk ducts and cisterns between milkings. It is through the teat ducts that the accumulated fluid is removed during milking (Seffner and Pfutzner, 1980). 10

6 a b Fig 2.1: Structure of the mammary gland showing teat and gland cisterns, milk ducts and glandular tissue (a). Glandular tissue, (b). Millions of alveoli within each mammary gland Classification of Mastitis Mastitis, caused by different organisms, is classified under two major groups namely Contagious and Environmental Mastitis. A. Contagious mastitis Contagious mastitis is caused by bacteria present in teat canal and udder, is transmitted from infected cow to uninfected cow while milking (Tikofsky, 2004). There is further sub classification of contagious mastitis Clinical mastitis Clinical mastitis is presented with five gross signs of udder inflammation namely redness, heat, swelling, pain, and clots or discoloration of milk (Fig 2.2). The general symptoms are the increased body temperature (> 39.5ºC) and loss of appetite. 11

7 Fig 2.2: The udder of a cow presented with clinical mastitis. Sub clinical mastitis Subclinical mastitis is characterized by change in milk composition with no sign of gross inflammation or milk abnormalities. It is recognized by laboratory examination of milk or by animal side tests hence, Hidden is the term given to this type of mastitis. Special screening tests such as the California mastitis test, (CMT), Wisconsin mastitis test (WMT), and the catalase test, detect changes in milk. The magnitude of subclinical mastitis towards the economic loss is conspicuous from the fact that in USA, it is responsible for 60 to 70 % of total economic losses associated with all mastitis infections (Galton et al., 1988). Chronic Mastitis Chronic mastitis is an inflammatory process that exists for months and may persist from one lactation to another. It exists for the most part as subclinical and may flare-up periodically as sub- acute or acute form for a short period of time. The results are hard lumps in the udder from the walling off of 12

8 bacteria and the forming of connective tissue (Rabello et al., 2005; Taverna et al., 2007). B. Environmental Mastitis Some organisms such as Escherichia coli do not normally live on the skin or in the udder but they enter the teat canal when the cow comes in contact with the environment which is highly contaminated. The pathogens are generally found in feces, bedding materials and feed. The pathogens in the contaminated environment get the earliest opportunity to invade the udder when the teat orifice is open at or soon after milking or after teat damage. These environmental pathogens are, thus, described as opportunistic invaders of the mammary gland. It is noted that environmental mastitis cases are only about 10% of the total mastitis cases in the herds Pathogenesis and the Microorganism Diversity Disease causing bacteria, referred to as pathogens are a multitude of microorganisms on and in cow udders (Fig 2.3.). Watts and co workers identified 137 species and subspecies of microbes associated with the mammary gland of cows (Watts et al., 1984). Several of these microbes do not cause mastitis. The most common microorganisms that cause about 90% of mastitis infection are given below: The most common bacteria: Staphylococcus aureus. Streptococcus agalactiae. Streptococcus pyogen, Corynebacterium pyogens etc. 13

9 The virulent viruses: Vesicular Stomatitis, Infectious bovine Rhinotrachitis, Bovine herpis virus etc Fungi: Tricosporium spp, Aspergillus spp, Candida spp. Mycoplasma: M. bovis, M. bovigenetelium, etc. The general micro organisms causing mastitis are Pseudomonas aeruginosa, S. aureus, S. epidermidis, Str. agalactiae, Brucella melitensis, Corynebacterium bovis, Mycoplasma, E. coli, Klebsiella pneumonia, Klebsiella oxytoca, Enterobacter aerogenes, Pasteurella spp, Arcanobacterium pyogenes, Proteus spp, Prototheca zopfii (achlorophyllic algae) and Prototheca wickerhamii (achlorophyllic algae). Fig 2.3: The pathogenesis of mastitis by Staphylococcus spp. 14

10 The other predisposing factors to mastitis are age, breed, nutrition, shed management, stage of lactation, and ROP. Buffalo is as susceptible to mastitis as cow and the causative organisms of mastitis in the herd are Staphylococci, Streptococci, E. coli, Pseudomonas spp, Corynebacterium, Mycoplasma, Str. dysgalactia, and Mycobacterium tuberculosis. Among the contagious pathogens the most common are Staphylococcus aureus, Str. dysgalactia and Str. agalactiae of which, S. aureusis the predominant organism (Osman et al., 2009). The major environmental pathogens are the Enterobacteriacae particularly E.coli and Str.uberis S. aureus infection remains the largest mastitis problem of dairy animals. (Allore et al., 1997) reviewed the incidence of mastitis in buffaloes and cows and concluded that the contagious organisms are responsible for most of the clinical cases and S. aureus is at the top of the list in both the species of the animals. Cure rate with antibiotic therapy during lactation is very low and infected cows that become chronic cases and are to be culled. Table 2.3: Microorganisms involved in mammary infection, their living condition and preventive treatment. Species Main Source Living Conditions Preventive Treatment Streptococcus agalactiae Infected cows Infected quarter and Wash udders after milking: udder only reduces problem by 50% Staphylococcus aureus Infected cows On abnormal udder and teat, milkers, Cull infected cows 15

11 vagina, tonsils Streptococcus dysgalactiae Infected cows Infected injuries quarter, Wash teats only, dry well with Streptococcus Contaminated On cow's skin, mouth, disposable paper towels for each cow uberis environment ground Supply generous bedding Escherischia cold Contaminated environment Ground, (sawdust shavings), water bedding and manure, Wash teats only, dry well with disposable paper towels for each cow Supply generous bedding Corynebacterium pyrogenes Certain insects Humid wooded areas valleys, Patterns of infection The mode of infection by different pathogens causing Mastitis varies in the mechanism and the resulting clinical subtypes. There are, as such, three patterns of infection. 1. The first mode of infection is the most common pattern caused by Str. agalactiae, S. aureus and Str. dysgalactiae. These infections usually continue as subclinical infections hence, control measures take many years to reduce the proportion of infected quarters. Prevention of infection can be achieved by sound milking methods, teat disinfection by dipping or spraying, thus reducing exposure to pathogens. 16

12 2. The second type of infection is found mainly in housed or closely corralled cattle. The classification of this type is acute clinical mastitis in early lactation. The main pathogens are Str. uberis and E. coli. Control methods mainly followed are reducing the exposure to pathogens by moving cattle regularly to clean corrals or daily cleaning the bedding. 3. The third type of infection is found in non-lactating cows. This type of infection is common in the early part of the dry period particularly with Str. uberis and continues as clinical mastitis in the following lactation. This is summer or heifer mastitis and its etiology is the exposure to vector based pathogens carried by a species of fly. This type of infection is controlled by drying off therapy and fly control Diagnosis of Mastitis In the past many methods that have been developed for the diagnosis of mastitis include Visual method, Direct method, Indirect method, CMT method, SCC method, Simplified Resazurin Rennet Test, Stir cup test, Surf filled mastitis test, Bromothymol Blue (BTB) test, Modified Whiteside test, Wisconsin Mastitis test, Electrical Conductivity test and Culture method test Visualization and Palpation of the udder Regular examination of the udder especially during milking is the primary step in preventing mastitis. With one or two episodes of mastitis, the animal attendant would be able to monitor the physical changes due to mastitis or any other infection. In clinical mastitis, visually the udder may turn red, hard and hot to touch. Udder may be painful to the cow at the time of palpation (Fig 2.4 a and b). These symptoms show the changes in vascularity and blood flow of the 17

13 gland when inflamed. On collection of the sample, the presence of pathogen is screened. a. b. Fig 2.4: a. Palpating the udder to check for mastitis. b. Brown Swiss heifer with swollen rear gland with mastitis Visualization of Milk At the time of milking, gross changes in the milk such as the presence of flakes, clots or serous, blood and watery secretions may be observed. In clinical mastitis this is the common means of detection. Flakes or clots in the milk are detected by stripping the first few squirts of milk from each quarter into a strip cup at the beginning of milking. The freshly drawn milk is, at first, examined by the naked eye of a dairy man for the visible abnormalities in the milk. Milk turns very much watery during dry period and also changes in milk composition is observed (Table 2.4). In advanced cases of chronic mastitis, the appearance of udder secretion is 18

14 usually abnormal at intervals. The secretion becomes grossly altered in case of acute mastitis. Table 2.4: Changes in the milk constituents associated with high SCC Constituents (%) Normal Milk Milk Weighed SCC Fat Lactose Total protein Total casein Whey protein Serum albumin Lactoferrin Immunoglobulins Sodium Chloride Potassium Calcium California Mastitis Test The California Mastitis Test (CMT) is not only an easily applicable test at the site but also the only reliable screening test for sub clinical mastitis (Fig 2.5.). The CMT has been developed to test milk from individual quarter and also bulk milk samples. Using the CMT, fresh, unrefrigerated milk can be tested for up to 12 hours and refrigerated milk can be tested for up to 36 hours to get 19

15 reliable readings. In this test, one teaspoonful milk (2ml) is drawn from each quarter and an equal amount of CMT solution added to each cup in the paddle. The CMT paddle is rotated in circular motion to mix the contents thoroughly. The CMT reaction must be scored within 15 seconds of mixing because exceeding that time weak reactions will disappear. The reagent used in the CMT is a detergent and bromoserol purple as an indicator of ph. The degree of reaction between the detergent and the DNA of cell nuclei determines the number of somatic cells in milk. Fig 2.5: California Mastitis Test (CMT) paddle and the reagent Table 2.5: T (trace) reference range for subclinical mastitis. CMT Score N (Negative) T (Trace) Somatic Cell Range 0 200, , , ,000 1,200,000 1,200,000 5,000,000 Over 5,000,000 Interpretation Healthy Quarter Subclinical Mastitis Subclinical Mastitis Serious Mastitis Infection Serious Mastitis Infection 20

16 This CMT helps us to assess the level of infection in each quarter rather than to an overall udder result. The result shows only whether the cell count is high or low. Therefore there is no numerical result. The CMT shows only changes in cell count above 3, 00, Somatic Cell Count Somatic cells are normal constituent of milk. In mastitis analysis cell and leucocyte counts in milk have been used for over a century. In 1910, Scientists used the term body cells for the reason that research at that time suggested that the cells in milk were detached epithelial cells. Cells found in normal bovine milk from non infected glands are inclusive of neutrophils (1-11%) macrophages (66-88%), lymphocytes (10-27%) and epithelial cells (0-7%) (Paape et al., 2000). Problem arises only when the somatic cells become excessive in milk. When there is infection or injury, leucocytes (up to 75%) and epithelial cells (up to 25%) are increased in milk. In infected glands more than 90% of SCC are composed of neutrophils and a SCC of greater than 2,00,000 cells/ ml is an indicator of mastitis. The severity of mastitis is determined by the number of somatic cells which is expressed as cells/ml of milk (Middleton et al., 2004). SCC is generally used to predict intramammary infection (IMI) at either quarter of the udder. Cows with SCC of less than 2,00,000 are not generally considered to have mastitis. But Cows with SCC above 3,00,000 are likely to be infected with pathogens. Varying degrees of subclinical mastitis will be present in herds with bulk tank SCC above 2,00,000. There are some problems with using composite milk SCC to identify infected cows because of the dilution of SCC values with milk from uninfected quarters. 21

17 Fig 2.6: Milk leukocytes (PMN) stained and observed under a microscope In mammary gland the presence of cell in milk is to protect the mammary gland from infections and to conduct surveillance function in the infected gland (Paape et al., 2000). Macrophages and PMN are phagocytic cells and they swallow and kill bacteria (Fig 2.6.). The lymphocytes consist of both B-cells and T- cells and they play important role in immune reactions in response to initial infection. When bacteria enter the mammary gland through the teat canal and multiply in milk, an inflammatory response (mastitis) takes place. Bacteria affect the function of the mammary ephithelium and also interact with the cells in milk, particularly macrophages and stimulate the production of many mediators inflammation (Zecconi et al., 1997). Some of the mediators are complement components, prostaglandins, leukotrienes, histamine, serotonin, interleukins, tumor necrosis factor, interferon and other cytokines (Anderson and Heneghan, 1979). Some symptoms of inflammation are vascular permeability, vasodilation, edema, increased blood flow, pain and fever. The influx of PMN leucocytes into the mammary tissue is a major line of defense for the udder (Paape et al., 2000). Over 90% of the cells present in milk early in inflammation may be PMN. The 22

18 speed of the influx of PMN is a key factor in the resolution of an infection and the severity of the disease Simplified Resazurin Rennet Test This test is simple and useful in practical in the detection of bovine mastitis. In this test, a sterile test tube is placed with a tablet of resazurin and rennet. Milk (10 ml) is directly added from teat into the test tube and incubated for 1 hr at 37ºC. The change in resazurin colour and the time required for coagulation are observed Strip Cup Test This test is generally used in determining the presence of clinical mastitis by the detection of visible particles of milk (Fig 2.7.). Strip cup method was first used by Moak. Any lay man can make use of this strip cup. In this test an enamel plate divided in four strip cups is used and the bottom of the plate is black in colour so that the milk flakes are easily observed by tilting the cups at an angle. Fig 2.7: Strip cup test 23

19 Surf Field Mastitis Test The handy readily available household surf (detergent) is used as reagent. This test is easy and cheap besides adequately sensitive to detect all cases of sub clinical mastitis (Muhammad et al., 1995). The surf (Surf T Excel 3%) solution is mixed in equal quantities with milk drawn from quarter in petri dishes separately for each quarter. The reaction of somatic cell s DNA with detergent (surf) and the resultant formation of gel in different degree are observed. The formation of gel indicates positive mastitis samples Wisconsin Mastitis Test This is a simple screening cow-side test on producer s milk. When WMT reagent is added to milk, the number of inflammatory cells rises high and results in development of a gel. The aim of WMT test is to maintain a bulk tank reading of less than 3,00,000 cells/ml. If the WMT score is more than 8,55,000 cells/ml the milk is not considered for human consumption (Ruegg, 2009) Bromothymol blue test This test indicates the ph value of milk that has been widely used in the diagnosis of mastitis. When bromothymol blue is added to milk, different colours are developed due to changes in ph of milk. The normal ph of milk is 6.4 to 6.8 and isotonic with blood plasma. The disadvantage is that this BTB test may give false positive reaction, when the cow is in later stages of lactation Electronic Somatic Cell Count This is automated electronic cell count equipment used by Dairy Herd Improvement Associations. Periodical report of the udder health of individual cows as well as the entire herd can be obtained by this test. The limitation is that 24

20 the Electronic Somatic Cell Count equipment is more expensive and constant monitoring is needed Electrical conductivity test This test can be easily done in the herd on- site. The increase in electrical conductivity in milk caused by the changes in levels of ions such as sodium, potassium, calcium, magnesium and chloride during inflammation is measured in this test. Changes in conductivity can be detected by hand-held or in-milk line instrumentation. EC is affected by the change in ph and decrease of fat. Electrical conductivity measuring can be converted into readable signal (Pyorala and Pyorala, 1997). Some variations not related to mastitis may be present in electrical conductivity and this will give rise to problem in the diagnosis of mastitis Economic losses due to Mastitis Mastitis is the most costly disease of dairy cows and the economic loss is due to discarded milk, early culling, drug costs, veterinary costs, increased labour and primarily decreased quantity and quality of milk and manufactured milk products (DeGraves and Fetrow, 1991). The loss of milk production due to mastitis is estimated in many different ways and one of the most important methods is based on milk SCC (Seegers et al., 2003). About 75% of the production losses due to subclinical mastitis is attributed to decreased milk production (Moniri et al., 2007). On economic parlance, subclinical mastitis is considered more important than clinical mastitis for the reason that losses associated with subclinical infection are widespread and overwhelming. In quarters affected with subclinical mastitis, total milk loss 25

21 is on an average %. Mastitis cannot be eradicated from a herd and no complete recovery is forecast for a quarter affected with clinical mastitis and added to this it gives rise to a carryover loss. The economic loss due to decreased milk production, increased milk replacement cost, discarded milk, drug costs, veterinary fees and labour cost aggregates to more or less 10% of total value of milk sales. The estimates of the cost of clinical mastitis is $107 US per clinical prevalence of which, 70% of the cost is connected with decreased milk production and milk withheld from the market, over 20% with drugs, veterinary costs and replacement cost and with labour (Ahl et al., 1989; Halasa et al., 2007). In India, annual loss due to mastitis is around Rs. 16,702 million. Subclinical mastitis is prevalent in India varying from 10 50% in cows, and 5-20 % in buffaloes as compared with clinical mastitis 1-10 %. The susceptibility of this infection is highest in purebred Holesteins and Jerseys and lowest in local cattle and buffaloes. Prevalence of subclinical mastitis is more widespread in monsoon season than in summer or winter. The following factors played important role in affecting incidence of subclinical mastitis: herd size, agro climatic conditions of the area, differences in socio- cultural practices, milk marketing, owner s literacy level, feeding system and management General treatment for Mastitis Treatment of mastitis is difficult but still certain measures are available to prevent as well as cure mastitis. Peter Schneider evaluated the treatment based on the work of the German Professor Dr.Gunther Enderlein. The features of isopathic and homeopathic regulatory treatment are isopathic remedies, haptene preparations, immunomodulators and medicines to improve cell respiration. S. 26

22 aureus is endowed with enzymatic provision. It enables S. aureus to migrate deep into the tissue of the udder. It is with great difficulty that any medication can reach such a deeper level. In cases of chronic S. aureus infection, an additional isopathic-homoeopathic treatment becomes necessary at the end of lactation or soon after. In the treatment of mastitis, it is more difficult to get at the Environmental germs than at the classical micro-organisms. In order to effectively control mastitis,the use of isopathic-homoeopathic remedies is certainly advantageous. Enderlein postulated that, millions of years ago the strains of fungi Mucor racemosus Fresen and Aspergillus niger van Tieghem inhabited the body of human beings and all mammals. He gave the name Endobiont to these microorganisms which pass through three basic developmental stages: colloidbacterium-fungus. If an endobiont climbs up higher the evolutionary scale, its potential to do damage becomes greater. Such bacterial forms develop in the tissue of the udder and also in the other tissues of the body. The defensive power of the tissue in the udder is mainly weaker. According to Enderlein, Isotherapy means that the more highly developed pathogenic forms must be reduced back to their lower, non-pathogenic forms and then eliminated from the body. Isothermic remedies are not directed against illness but they support the body s own regenerative ability to heal the illness. Schneider classified the treatment of bovine mastitis rests on four strategies (Schneider, 2000): 1. Removal of blockages in reaction and improvement of cell respiration 2. Modulation of the immune system 27

23 3. Isopathic deconstruction of the mastitis-triggering organism back to a non-pathogenic form 4. Cleansing of the bacteriological soil. 28

24 2.3 Materials and Methods Sample Collection Contact with the district veterinary hospital and six veterinary rural health centers in Salem and Krishnagiri Districts, Tamil Nadu, India was established and a preliminary field survey was conducted on mastitis incidence. The farmers were contacted through local veterinary hospitals and advised to notify about the cows with mastitis disease conditions. Within the study period from August 2007 to November 2010, three hundred and twenty milk samples were collected from cows affected with mastitis. The samples were collected afresh, before initiating antibiotic therapy. There were many incidences wherein the milk samples could not be collected since the therapy was initiated before sample collection. Fresh milk samples of one hundred and forty normal cows were collected from the locations of mastitis incidence. Before collecting the samples, the status of the animal as normal cow or clinically positive for mastitis was confirmed by a veterinary physician. On clinical examination, each animal was classified under clinical/ sub-clinical/ environmental mastitis. The udder was cleaned with water then 70% ethanol prior to sample collection. After 5 min, the milk was drawn manually into a sterile Falcon tube (50 ml) and labeled. Each collection was assigned with a code number and related to the farmer/owner of the cow. The condition of the environment wherein the animal was kept was also recorded. The collected samples were transported in a box filled with ice packs to the lab within three to four hours and stored at -80º C until use. The age and number of calving and the previous episodes of mastitis were noted down. The pictures of the cow, udder and the cow shed were documented. The following animal-side tests were conducted. 29

25 2.3.2 Visual examination of the milk samples During the sample collection, the milk drawn in the falcon tube was visually examined. The analysis was performed for every quarter of the udder per animal. The normal viscosity and any change by way of watery conditions were noted down. While the color of the milk was from pale to dark pink, presence of blood was recorded Strip cup test The status of the animal can be judged by performing certain tests on field by a veterinary physician. Since strip cup test is simple, cost effective and rapid to detect Clinical Mastitis, it was performed on Mastitis suspected cows, before collection of sample in falcon tube. The milk (2ml) was added onto a black colored plate/cup and observed for milk flakes by tilting the plates at an angle Surf Field Mastitis test In order to differentiate clinical and subclinical mastitis at the animal side itself, surf field mastitis test were conducted during every sample collection. Two milliliters of surf (surf excel 3%) solution was mixed in petri dish with equal quantity of milk drawn from every quarter. This was mixed by rotation and examined for clot formation. 30

26 2.4 Results Sample collection A total of 320 milk samples were collected from the cows with clinical and sub-clinical mastitis from Salem and Krishnagiri Districts, Tamil Nadu, India. Normal milk samples from 140 cows without any disease were collected from the locations wherein mastitis samples were collected. The breed and disease status of the cows are provided in Table 2.6. Of the different breeds present in Tamil Nadu the majority are HF, Jersey and Kangayam (Fig.2.8), in general the HF breed is the preferred cow by the farmers as well as promoted by the animal husbandry division. The daily yield of milk from HF breed ranged from 15 to 25 liters based on the feed, calving and climate conditions. The yield for Jersey was within a range of 8 to 15 liters while that of Kangayam was from 3 to 7 liters. The extent of the disease varied from mild to moderate to severe (Fig. 2.9). On examination, the cow exhibited clinical symptoms was classified as clinical and subclinical mastitis. Out of 189 HF animals, 138 (73%) were identified as clinical and 51 (27%) as subclinical mastitis. In case of Jersey breed, 79 (84%) out of 94 were classified as clinical and the rest was subclinical mastitis. Of 37 cows of Kangayam breed, majority of them (34, 91%) were with clinical mastitis. 31

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29 Table 2.6: Clinical and demographical details of normal and mastitis cows S.No Description No. of animals Clinical Subclinical Mastitis cow HF Jersey 189 (59%) 138 (73%) 51 (27%) Kangayam 94 (29%) 79 (84%) 15 (16%) Normal cow 37 (12%) 34 (91%) 3 (9%) 2 HF 140 Jersey 67 (48%) 0 0 Kangayam 58 (41%) (11%) Visual examination of the milk samples During the sample collection, the results obtained from the visual examination of the milk drawn in the falcon tube are represented in Table 2.7. The analysis performed for every quarter of the udder per animal on the viscosity and watery condition and presence of blood indicated that majority of the samples (38% to 41%) contained flakes / clots. About 16% to 22% of the samples exhibited watery condition while blood was observed in less number (11% to 15%). On average 30% of the samples did not have any visual changes during sample collection. 32

30 Table 2.7: Visual examination of milk samples from mastitis and normal cows Group Breed No. of animals Flakes / Clots Blood Watery No visual change n % n % n % n % Mastitis HF % 28 15% 31 16% 57 30% Jersey % 13 14% 17 18% 25 27% Kangayam % 4 11% 8 22% 11 30% Normal HF % 2 3% 6 9% 55 82% Jersey % 1 2% 4 7% 51 88% Kangayam % 0 0% 2 13% 12 80% Strip cup and Surf Field tests on mastitis and normal milk samples To establish a simple test to be conducted on animal side, the strip cut and surf field tests were evaluated. The comparative results obtained on both the tests are presented in Table 2.8. By strip cup test 50% to 60% of the samples from clinical mastitis could be identified with flake / clots. With regard to subclinical mastitis, the detection was up to 20% only, since, the physical changes of milk are minimal at subclinical level. The surf field test was more reliable in identifying above 80% of the subclinical mastitis samples. Though this test was useful in detecting clinical mastitis, only about 48% of the samples from Jersey breed could be identified. With regard to normal milk samples, 2% to 6% of them were positive. This was considered to be normal under veterinary conditions due to unknown etiology. In general, alterations in the conditions of milk samples from Kangayam native breed were minimal or absent. The incidence of physical and visual changes was higher with HF followed by Jersey. The observations made to 33

31 establish a basic protocol for routine milk examination with respect different breeds. Employing a common protocol may not help since, milk constitution varies among the cattle breeds Table 2.8: Strip cup and Surf Field test on milk samples from mastitis and normal cows Group Breed Diagnosis No. of animals Strip cup test Surf Field Test n % N % Mastitis HF Clinical Sub clinical % 14% % 80% Jersey Clinical Sub clinical % 20% % 80% Normal Kangayam HF Jersey Kangayam Clinical % 29 85% Sub clinical 3 0 0% 3 100% % 2 3% % 1 2% % 0 0% 34

32 2.2.6 Discussion Agricultural livestock is the widely contributing sector to India s gross capital income. During , the gross value of output of livestock in the State is Rs. 20,940 crores. Livestock sector contributes about 2.74% of Tamil Nadu s Gross State Domestic Product (GSDP) and that to the agriculture and allied activities is 36.45%. The cattle population of lakhs accounts for 36.38% of total livestock ( lakhs) in the Tamil Nadu State. The cow is one of the remarkable domestic animals in the world, adapted to live in arid and semi-arid conditions. In India, cow is inherently associated with the culture, religion and social life of the most of the communities. Cow is used for production of milk, meat, as well as for transportation of both people and goods. The exotic, crossbred, indigenous and native pure breeds account for 0.44%, 55.79%, 6.01% and 37.76% respectively. Though native breeds are more disease resistance, the limited milk yield prompted alternate solutions. As part of white revolution, to increase the milk production, exotic cattle breeds were promoted. The purebred Holstein-Friesian (HF) cattle with its distinctive large black and white colour markings originate from Holland and Friesland in the Netherlands. The HF heifers yield more than 25 litres of milk a day. In addition, Jersey cross breed was also of preference. Such exotic and crossbred animals, though on selective breeding, are new to temperate conditions hence more susceptible to infection. Under unhygienic conditions, the opportunistic micro organisms invade the udder through the teat canal and colonize around the teat duct and epithelial cells causing massive inflammation of udder resulting in cattle mastitis. The heavy loss of milk production by bovine mastitis has economic impact in the management of dairy farms. 35

33 In this present study as detailed in Table 2.1 it was obvious that among the 320 study animals, the incidence of mastitis was higher among the HF breed (59%) followed by Jersey (29%). The disease among Kangayam breed (12%) was limited, could be related to disease tolerance and over all availability of the animal with the farmers. Most of the episodes of mastitis happened wherein the animals were maintained in poor hygienic conditions, later improved due to awareness created by mastitis infection. Mastitis is categorized into clinical, sub clinical and environmental mastitis. Clinical and subclinical mastitis are with known etiology of host factors while environmental mastitis is related to the ambient environment. Hence environmental mastitis can easily be controlled by maintaining proper hygienic conditions like clearing the feaces, changing bedding material at regular time and also clearing feed after every meal. Differentiation of mastitis affected population from that of normal ones is very important and thus various identification tests are developed till date. The common tests suggested by different researchers are California Mastitis Test (CMT), Somatic Cell Count (SCC), Strip Cup test, Surf Field Mastitis test and Wisconsin Mastitis test. In order to differentiate the three categories of the disease, animal side tests were conducted. The visual examination of the milk was able to confirm up to 70% of the mastitis conditions. About 30% of the cases, it was difficult to make a decision by visual examination. Of the two simple analytical tests performed, strip cup test could identify 50% to 60% of the clinical and 20% of the subclinical mastitis while surf field test could detect around 80% of the subclinical mastitis. As a routine monitoring of the milk collections, these tests could suffice to certain extent in identifying mastitis conditions. Yet, practicing regular udder examination and milk evaluation for 36

34 the presence of flake / density / blood would keep a watch on the disease and help in prevention to a larger extent. In case of disease manifestation, further microbial and biochemical tests need to be performed for identifying the infectious and causative agent of mastitis and also the mechanism involved. 37