







































10.11648.j.ijhnm.20160201.11


 

 

 

 

 

    ISSN : 2693 6356 

2021 | Vol 4 | Issue 5 
 

 

 Prevalence of Bovine Mastitis and Assessment of 
Risk Factors in and Around Wolayta Sodo, Ethiopia 

Dr. Sachin Dangal Patil 
Associate Professor  

Homoeopathic Medical College & Hospital, Jalgaon 

 

 

Abstract: The purpose of this cross-sectional study was to estimate the prevalence of mastitis and to assess the associated 

risk factors in dairy breeds (jersey, indigenous zebu, and high grade Holstein) in the Woliata Soddo area and surrounding areas 

from November 2013 to May 2014 at the Soddo regional veterinary laboratory. A clinical examination and Californian Mastitis 

Test (CMT) were conducted on 386 nursing cows, including 216 indigenous zebu, 88 jersey, and 82 high grade Holsteins. The 

patients who tested positive for both clinical and subclinical mastitis were then tested for bacteria. Among the 134 animals 

tested, 34.7% tested positive for clinical mastitis and 61.19 percent tested positive for subclinical mastitis. A total of 21.94 

percent of the 966 quarters tested positive for mastitis. Mastitis was much more common in high grade Holstein cows (54.8%), 

jersey cows (44.3%), and indigenous zebus (23.1%) compared to other breeds (P< 0.000). Regarding quarters, however, no 

discernible variation existed between breeds. Mastitis was most common between 1 and 120 days into early lactation (43.8%), 

between 120 and 240 days into mid-lactation (32.8%), and beyond 240 days into end-lactation (23.8%). Additionally, the 

difference between lactation was statistically significant (P<0.000). There was a positive correlation between parity and 

mastitis prevalence (r=0.8), with the greatest incidence occurring at lactation stage 6 and thereafter. Microbiologic analysis was 

performed on 134 udder quarter samples; 111 (82.8%) were found to be culturally positive, whereas 23 (17.2%) were found to 

be negative. Out of the 124 bacteria that were recovered in positive samples, 43.54% were Staphylococcus, 28.89% were 

Streptococcus, and 19.35% were Coliform. Findings informed calls for further education of dairy cow owners and calls for 

additional research into financial losses. 

Keywords: Woliata Soddo, Bovine Mastitis, Prevalence, CMT, Bacteriological Examination, Risk Factors 

 

1. Introduction 
Injurious substances such as pathogenic microbes, 

trauma, and chemical irritants may cause 

mammary gland inflammation, which is known as 

masttitis. Mastitis in dairy cows is always caused 

by microorganisms, most often bacteria but 

sometimes yeast, mycoplasma, and, on rare 

occasions, algae. Staphylococci, Streptococci, and 

a few other gram-negative bacteria are the most 

common infecting microorganisms. The teat end 

may get infected with infectious bacteria that are 

found in the environment, such as coliforms and 

some streptococci species [1].  

 
Although moderate or severe clinical 

manifestations are possible, masttitis is often 

subclinical in character. Host, agent, and 

environmental factors all play intricate roles in 

illness etiology and progression [1, 2]. 

Economically significant decreases in output and 

productivity are caused by masttitis. Mastitis milk 

may cause significant financial losses because of  

 

the risks associated with treating the infection, 

throwing out antibiotic-treated milk, decreasing 

the market value of milk, and even mortality from 

inflammations [1, 3].  

Food poisoning, disruption of production 

processes, and the transmission of zoonotic 

diseases including TB, brucellosis, and 

streptococcal sore throat are all possible outcomes 

of milk produced by mastitic animals. Also, the 

public health issue of antibiotic residue infections 

and mastitis-treated  

 

animals' milk is a problem [1]. In Ethiopia, the 
limited information available [8] indicates that 

bacteria mastitis is one of the major facing all 

dairy farms in the Country. Moreover, 

Mohammed [9] in his study on the bacterial 

causes of bovine mastitis in Zebu, Holstein dairy 

caws of Wondogenet all of southern Ethiopia 

found a quarter infection rate of 16% by 

potentially pathogenic bacteria however, 

economic losses due to mastitis in Ethiopia are not 



known. According to [10] in their assessment of 

10 state dairy caws more than 10% of caws in 

most farms in Ethiopia have at least one blind 

quarter. In addition, [11] in their assessment of 10 

state dairy farms near Addis Ababa point out that 

mastitis accounts for major economic losses. In 

general, regarding the occurrence and distribution 

of major causative agents of the disease, in 

Ethiopia in general, and in southern regions in 

particular, is inadequate, moreover, not enough 

investigations have been carried out to ascertain 

the effects of different risk factors on the 

prevalence of mastitis. Therefore, by considering 

all the above information this study set out the 

following objectives: to estimate the prevalence of 

bovine mastitis in Woliata Soddo; to isolate and 

identify major potentially pathogenic bacteria that 

cause bovine mastitis and to recommend the 

appropriate control and prevention methods that 

are applicable in the study areas. 

 

 

 

2. Materials and Methods 

2.1. Study Area 

2.2. From November 2013 to May 2014, 

researchers at the regional veterinary 

laboratory in Woliata Soddo town conducted 

the study. Situated in the SNNPR, about 383 

kilometers from Addis Ababa, lies the town 

of Woliata Soddo. Damot gale woreda forms 

the northern boundary, Humbo Woreda the 

southern one, Damotwoide the eastern one, 

and Damotsore the western one. It gets 100–

1200 mm of rain each year and 25–35°C in 

temperature, and its height spans from 1650–

2980 m.a.s.1. The Woliata Soddo zone is 

located in a woinadega (mid altitude) region 

with an elevation below 1600 meters. The 

animal population in this area includes 

around 128,919 cattle, 29,191 sheep, 4,606 

horses, and 55,272 chickens [12].Study 

Population and Their Management System 

Here, we studied indigenous zebus from 

around Sodo, jersey cows from Sodo dairy farm, 

and high grades Holstein Frisian from the dairy 

farm in the sodo area and in the Sodo town. 

Indigenous zebu animals in peasant farm are 

reared mainly for meat, milk production, and the 

generation of cash income and the provision of 

draft power. They are not supplemented except 

during dry season when farmers offer their 

animals straw of various crops and pasture 

grasses in a cut, and carry form. They usually 

graze on communal pastures where transmission 

of contagious disease is facilitated. The dairy 

farm at Soddo had relatively improved 

management system; jersey cows were housed 

in a free stall in which each animal was tide by 

chain. Pregnant cow were transferred to a 

maternity house a few days before parturition, 

generally without any preparation. Calves aging 

up to 6 months were penned separately. Cows 

were allowed to graze on native or improved 

pastures or both growth on the faced grazing 

land of the farm and watered with hay or 

concentrates mainly during the dry season. 

Generally, problem associated with inadequate 

nutrition were uncommon, milking was 

conducted twice a day 

2.3. Study Methodology 

2.3.1. Study Design 

A cross sectional study design was conducted 

from November 2011 to May 2012. 

2.3.2. Sample Size Determination and Sampling 

Technique 

A total of 386 cows, of which 216 indigenous 

zebu, 88 jerseys and 82 high grade Holstein 

Friesian were sampled using the formula on 

[13]. The cattle were grouped into lactating 

cow (in milk), breed as indigenous zebu, jersey 

and high grade Holstein Friesian, lactation stage 

into early lactation (1-120 days) mid lactation 

(121-240 days) late lactation (above 240 days) 

and parity number as 1
st
, 2

nd
, 3

rd
, 4

th
 5

th
, 6

th
 and 

above 6. Milking sample was collected 

hygienically after each quarter was washed with 

clean water and soap and then cleaned with a 

swap dipped in 70% alcohol while extruding 

the external sphincter by pressure to ensure that 

dirt and wax were removed from the orifice. 

Ten ml of milk were collected in a test tube and 

held in oblique manner to prevent 

contamination of samples by falling particles. 

2.4. Data Collection 

During the sampling of animals for the 

present study, the breed, parity number, status 

of mammary gland, stage of lactation or 

lactation period were noted, and so were 

clinical findings (e.g., palpable and visible 

abnormalities of the udder, nature and 

appearance of milk secretion). 

Questionnaire: A preliminary survey was 

conducted in the specified study areas and 

adjoining localities during initial period of the 



study. The questionnaire targeted mainly dairy 

farms and livestock owners; it was aimed at 

generating basic information on livestock 

management system, nutrition, hygienic 

practices, disease detection, housing, 

prevention and control measures. 

Diagnosis of mastitis: Although mastitis in an 

individual cow may be obvious, it is more often 

a sub clinical case or disease and clinical. 

Therefore tests for the detection of changes in 

the udder or the milk caused by mastitis are 

necessary. In this study criteria for the detection 

of mastitis included: 1) Physical examination of 

udder quarter for signs of inflammation by a 

thorough clinical inspection and palpation; and 

2) Detection of high level of leukocytes in milk 

using the Californian mastitis test (CMT). 

Microbiological procedure: All positive 

samples were analyzed microbiologically by 

CMT and clinical examination according to 

[14]. Samples from individual quarter where 

centrifuged at 3000 revolution for 15 minutes 

and supernatant was discarded. Standard loop 

full of 0.01ml of milk was then removed from 

the sediment and cultured on 

 

blood agar plates containing 7% of sheep blood, 

Maconkey agar plates or Edward’s agar plates. 

Inoculation of plates performed with a 0.01 ml 

wire loop. The original milk samples were also 

incubated at the same temperature and cultured 

similarly 24 hours after bacterial growth was 

identified and recorded, at 24 and 48 hours of 

incubation. 

At the end of this period, identification of 

isolated bacterial was made on the basis of 

morphology, color and size of the colonies, 

presence or absence of hemolysis and gram 

stain. The identification of bacterial isolates up 

to the species level was made by sub culturing a 

single pure colony and conducting the following 

tests: 

Staphylococcus species and micrococci were 

identified and differentiated by gram staning, 

colony morphology, catalase test, tube 

coagulase test using human plasma, ability to 

produce hemolysis, ability to ferment maltose, 

and manitol. 

Streptococcus species were identified and 

differentiated by colony morphology catalase 

test, growth characteristic on Edward’s media, 

ability to produce hemolysis CAMP test. 

Coliform species were identified and 

differentiated by colony morphology on the 

Maconkey agar; gram staining, motility test, 

indole test, triple sugar iron agar for the detection 

of lactose and glucose fermentation and hydrogen 

gas production. 

2.5. Statistical Analysis 

The data collected was filled into microsoft 

excel and then analyzed with Chi-square and P- 

value using SPSS vergin 20. 

 

3. Result 

3.1. Questionnaire 

3.2. In the farms included in this study no 

strip cup was used and dry therapy and post 

milk disinfection were not practiced. Clinically 

detected cases of mastitis have been treated by 

parental injection of locally available drug, 

most of the time by pencilline, streptomycin, 

and oxytetracyclines. Animal at the Soddo 

dairy farms and in farmers hand had high tick 

infestation, despite regular treatment with 

steladone. As regards nutrition, almost all dairy 

cows, especially those in peasant’s farms, were 

kept on dry roughage except during rainy 

season when green feeds are available. Type of 

housing ranged from open kraals to free stalls 

in which cow were tied with chains. 

3.3. Clinical Examination 

Of the total 386 cows examined, 134 (34.7%) 

were found to be positive for mastitis: 52 

(38.8%) clinical and 82 (61.1%) sub clinical 

mastitis. Out of 966 quarters, 212 (21.94%) 

were found to be affected: 83 (39.15%) 

clinically and 139 (65.56%) sub clinically 

affected. In the clinical cases, 12 blood tinged 

milk with sign of inflammation in the affected 

quarter, 20 had watery without sign of 

inflammation in the quarters, 13 milk contained 

pus with swollen quarter mostly. Seven animals 

had acute mastitis with signs of inflammation in 

the quarter and severe inflammation. Among all 

animal examined, 105 blind quarters were 

found and those that had an indurate mass due to 

fibrosis were common in most cows. 

3.4. Prevalence of Mastitis 

Clinical examination and screening test 

results indicate an overall prevalence rate of 

34.7%. The prevalence rate differed 



significantly among breeds (p<0.05). 



 

 

 

Table 1. Prevalence of mastitis by breed in and around Wolaita Soddo. 
 

Breed No of animal examined No. of affected No. of not affected prevalence 

Indigenous zebu 216 50 166 23.1% 

Jersey 88 39 49 44.3% 

High-grade Holstein 82 45 37 54.8% 

Total 386 134 252 34.7% 

X2 = 31.04; P= 0.000 

 

Quarter prevalence of mastitis is found to be 25% in high grade Holstien and 20.82% in indigenous zebu with no significant 

difference among quarters of the three breeds. 
 

Table 2. Quarter prevalence of mastitis by breed. 
 

Breed No. of quarter examined Noof affected No of not affected prevalence 

Indigenous zebu 485 101 384 20.82% 

Jersey 281 61 220 21.70% 

High grade holstien 200 50 150 25% 

Total 966 212 754 21.94% 

X2= 1.43; P=0.49 

 

The highest prevalence is seen in early lactation (1-120 days) in which out of 228 animal examined 100 (43.85%) were 

found positive and the lowest prevalence is seen in end lactation (<240 days) 23%. 

 
Table 3. Prevalence of mastitis in different lactation stage. 

 

Stage of lactation No. of examined No. of affected No. of not affected Total 

Beginning (1-120 days 228 100 (43.85%) 128 (56.14%) 228 

Middle (120-240days 137 44 (32.25%) 93 (68.19%) 137 

End (<240 days) 21 5 (23.80%) 16 (76.19%) 21 

Total 386 149 237 386 

X2= 7.03; P= 0.000 

 

The highest prevalence (64.51%) is observed at a parity number 6 and above and the lowest prevalence (26.08%.) observed 

at first parity number which is the prevalence raised with an increase in parity number (r= 0.8). 
 

Table 4. Prevalence of mastitis in various parity groups. 
 

Parity number No. of cowexamined no. of mastitic animal None mastitc animal Prevalence % 

1 115 30 85 26.08% 

2 93 17 76 39.54% 

3 75 29 46 38.66% 

4 54 28 26 51.85% 

5 18 10 8 55.55% 

6 and above 31 20 11 64.51% 

 

The prevalence of 41.66% was seen in animals with lesions and/or tick infestation on teat and /or udder skin as compared to 

animals without lesions and/or tick infestation, in which the prevalence was 25.88%. 

Table 5. Prevalence of mastitis in relation to predisposing factors. 

 

Cow Infected animal None-infected Total 

With lesion and /or tick on skin or udder 90 (41.66%) 126 (58.33) 216 

Without lesion and tick infestation on skin /teat or udder 44 (25.88%) 126 (74.11) 170 

Total 134 252 386 

X2= 12.52; P= 0.02 

 

In the present study, the highest prevalence was seen in housed animals as compared to pastured cows. 
 

Table 6. Prevalence of mastitis by management system. 
 

Management Animals examined No. of affected None affected Prevalence 

Pastured 216 50 166 23.14% 



Housed 170 84 86 49.41% 

Total 386 134 252 34.7% 
 

X2= 35.42; P= 0.000 

 

3.5. Milk Bacteriology Results 

Bacteriological examination was carried out on all CMT and clinically positive udder quarter samples to identify the causative 

organism involved in the disease. The organisms were identified based on colony morphology, gram stain, heomolysis 

andbiochemical test for species identification. The differentiation of microorganisms was carried out according to [14]. 

Out of 134 positive animals, 52 were clinically infected while 82 were sub-clinically infected. From 134 positive animals 

only 111 is culturally positive. 

Table 7. Prevalence of clinical and sub clinical mastitis. 
 

Infection status Clinical mastitis Sub clinical Total 

Infected 52 (38.15%) 82 (61.1%) 134 

None-infected 126 (32.64) 126 (32.64%) 252 

Total 178 208 386 

 

Of all culturally positive animals, 46 were from clinical and 65 from subclinical cases. 
 

Table 8. Staphylococcus identification. 
 

hemolysis Catalase Tube cougaluse Manitol test 0-F test Frequency of isolation Species of bacteria isolated 

+ve +ve +ve +ve F 54 S. aureous 

-ve +ve +ve -ve F 2 S. hyicus 

-ve +ve -ve -ve F 3 S. epidermides 

+ve=positive;-ve=negative; F= fermentation; CMT= Californian mastitis test O-F= oxidation fermentation test; S=staphylococcus 



 

 

Table 9. Streptococcus species identification and differentiation results. 
 

Hemolysis Catalase CAMP test Hydrolysisof aesculin on Edward media frequency of isolation Species of streptococcus identified 

Alpha -ve +ve -ve 10 Strep. agalactiae 

Beta -ve +ve -ve 6 Strep. agalactiae 

Gamma -ve -ve +ve 7 Strep. dysagalactiae 

Beta -ve -ve +ve 4 Strep. dysagalactiae 

-ve= negative+ve=positivestrep= streptococcus 

 
Table 10. Genera of bacteria isolated from clinical and sub clinical mastitis. 

 

Cases Staphylococcus Streptococcus Coliform 

Clinical 15 7 7 

Sub-clinical 25 12 8 

Total 40 19 15 
 

Out of all clinical cases, 15 were caused by staphlococcus, 7 were caused by Streptococcus, and 7 by coliform species. Out of 

all subclinical cases, 25 were by Staphylococcus, 12 by Streptococcus and 8 by coliform species. 

 

4. Discussion 
The purpose of the research was to find out how common bovine mastitis is in the town of Woliata Soddo in southern Ethiopia. 

The overall frequency of the illness in cows was 34.7% and in quarters it was 21.94%. This result is in line with the overall claim 

made by [1], who states that the incidence rate in cows is 40% and in quarters 25% in most nations, regardless of the source. 

Results from [4] and [15] showing a prevalence of 45.8% in Sudan and 45.5% in Ethiopia, respectively, are in agreement with the 

infection rate in cows. Compared to the results of [4], which indicated a quarter infection rate of 38.8% in Sudan, this was lower. 

Factors including the environment, the agent, and the host may contribute to the variance in the general prevalence of mastit is. 

According to this research, an unclean milking process and ineffective management might lead to a higher infection rate. One 

possible explanation for the observed variation is that management styles change from one location to another. 

Zebu, jersey, and high grade Holstein cows had significantly different incidence rates (P<0.05). In contrast to Jersey-holstien 

crosses, those involving the Holstein Frisian or Hariana breeds were more likely to have subclinical mastitis, according to several 

writers [16]. In addition, researchers in Kombolcha, Ethiopia, discovered that the prevalence rate of zebu holstien crosses is much 

greater than that of the zebu breed [18]. The impact of milk output on mastitis incidence may account for this variance. Also, 

according to [1], high-yielding cows are more likely to be affected. The high milk output stress that may upset the animals' 

defense system and the ease with which injuries may be incurred in huge udders, which provide foci for the entry of viruses, 

might be the reasons for this. Due to the lack of interaction between the two breeds during milking, the local zebu, whose 

prevalence rate was much lower than that of Jersey and Holstein, were at danger of mastitis.  

 

 

Relative to other breeds, there was a higher incidence of sanitary procedures, lesions, and tick infestations on the surface of the 

udder and teats.  

Prevalence rates of sub-clinical mastitis were 61.19% and clinical mastitis was 38.80% in this research. The yearly incidence rate 

of 41.2% in England's dairy herds is consistent with the severity of clinical cases. According to studies conducted in Sudan [5] 

and Ghana [20], there is a 46% difference between sub-clinical and clinical mastitis, whereas in Ghana it is 20% and 41.67%, 

respectively. Mastitis prevalence was shown to be 43.85% during early lactation (1-120 days), substantially greater than 32.25% 

during mid-lactation (121-240 days) and 23.25% at the end of lactation, when the influence of lactation stage was evaluated (P< 

0.05). Consistent with previous research, this data supports the high prevalence seen in early lactation sahiwal cows in India 

(reference 21).  

Multiple forms of physiological stress, including early breastfeeding, may lower immunity and lead to an upsurge in mammary 

gland infections, as stated in [22]. According to [23], acute mastitis is common during breastfeeding because neutrophils in the 

mammary glands have a delayed diapedesis, which reduces their resistance. The increased prevalence rate seen in early lactation 

in this research may be explained by this fact. Animals without this lesion and/or tick infestation on udderand/or teat skin had a 

prevalence rate of 41.66% compared to animals without these variables at 25.88%. This was done in order to determine the effects 

of these factors on the prevalence of mastitis. This result was in line with previous reports from [18], [20], [24], and [3]. 

Staphylococci and, to a lesser degree, streptococcus colonized the teat lesions in this population of animals, which may explain 

the high occurrence.  

Mastitis prevalence was found to be 49.41% in housed cows and 23.14% in pastured cows as a result of the management 

approach. Because the organisms may be easily transmitted from infected to healthy animals, our results are in agreement with 

those of [25], who also discovered a much higher incidence rate in housed animals. After conducting a thorough microbiological 

examination of the sample, it was found that out of the 124 organisms identified, staphylococcus aurous constituted 43.54% of the 

total.  

 

This finding was consistent with those of [6], [26], all of whom found Staphylococcus aureus as predominant isolates from 

bovine mastitis. 

The predominance of Staphylococcus aurous could attribute to the wide ecological distribution of the organism on intra 

mammary and skin of the udder and frequent colonization of the eroded and injured skin on the teat and/or udder of the cows. 



[1] The bacterium is able to thrive in the udder and may cause a mild illness that lasts for a long time. It can then spread to 

healthy animals via milk, which happens mostly when milking is not done properly. Possible causes of the high isolation rate 

include unsanitary living quarters, insufficient dry treatment, insufficient milking teat dipping, and a low rate of culling for 

animals who suffer from mastitis. The isolation rate for Staphylococcus epidermidis was 2.41% and for Staphylococcus hyicus 

it was 1.61%. The researchers in this investigation identified S. epidermides and S. hyicus as cougalase negative 

Staphylococcus.  

A recovery rate of 16.12% for Escherchia coli was observed; this finding is in agreement with [27], which reported an isolation 

rate of 11.5%; however, Demelash's reported rate was 3.14%, and Klebsiella aerogenes occurred at a rate of 3.23%. The most 

common source of these coliform organisms in dairy cow environments is manure [3]. According to popular belief, these 

viruses may live and reproduce in non-mammary areas more effectively than other prevalent mastitis infections. Additionally, 

no one control approach has been shown to be efficient in laboratory settings. 

Isolation rates of Streptococcus agalactiae were 13%, 10%, and 13.5 percent, respectively, in previous studies [28], [29], and 

[27]. Although 38% and 37% were lower than the results in [30], they were still below the average. Possible causes for the 

relatively high isolate of this organism in this research include improper hygiene during milking, not dipping the teats after each 

milking, not treating animals who were clinically infected, not using dry period therapy, and not culling cows that didn't react to 

dry period therapy. Among the isolates, 8.87% were Streptococcus dysagalactiae and 4% were Streptococcusuberis.  

 

Because most of the illnesses were not severe enough to warrant treatment, many of them spread to other cows in the herd and 

eventually became clinical. While farmers and herd managers may be aware of the symptoms of mastitis, they may not realize 

how common the illness is or how much money it costs. Antibiotics can help with mastitis control in dairy cows, but they aren't 

a panacea. What's more, overusing antibiotics like penicillin and streptomycin could lead to the rise of bacteria that are resistant 

to both drugs. Hence, according on these comments, the following suggestions are made: When it comes to milking, dairy farms 

should adhere to strict sanitary procedures; Chronically sick cows, whether they have blind quarters or not, should be 

slaughtered to eliminate a possible vector for disease.  

 

be eradicated; additional research should be conducted, focusing on the factors that put farmers at risk of financial losses due to 

the disease, in order to raise awareness among farmers about the disease and its impact on dairy production; and short-term 

training, extension workers, and model farmers should be employed to educate farmers about the disease.  

Author Contribution 

JSh: conception of the research idea, designing data collection, interpretation of the results and drafting the manuscript. IT: 

data collection and drafting the manuscript. The authors read and approved the final manuscript. 

 

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[25] In Their Anatomy of the Mammary Gland: Anatomy and Physiology of the Fifth Edition (Lea and 
Febiger, Philadelphia, 1992: 466-473), Frandos and Spurgeon provide the following information.  
[26] In Low Southern Western Veterinarian, December 1960, 13: 114–118, Fred, C. N. discusses 
chloranphinicol as a therapy for staphylococcal mastitis.  
[27] Tiruneh, Z.: A DVM thesis completed in 1996 at the Faculty of Veterinary Medicine at Addis Abeba 
University examined the frequency of subclinical mastitis in Asella dairy farms.  
[28] inOdongo, M. O., and Ambani AIA: 1989, Veterinary Diagnostic Laboratory in Kebete, Kenya, Isolated 
Microorganisms from Bovine Milk Samples.  
[29]Gezahegn, S.: Subclinical mastitis in Freisian-indigenous zebu crosses in Bahirdar: prevalence and cause. 
DVM thesis. Graduated from the University of Addis Abeba's veterinary medical program in 1996.  
[30]In a 1990 article published in the Journal of the South African Association, Bryson and Thomson 
discussed the methods used in the lab and in the field to reduce clinical mastitis in dairy cows in the Bulawayo 
area. 


