Dissertation: Mastitis management in urban and peri-urban dairy herds of North-Western Ethiopia

Mastitis is an important disease worldwide that causes economic losses by affecting the health of dairy cows and milk quality. Moreover, mastitis has an effect on animal welfare and may threatenpublic health because of the shedding of antimicrobial residues and resistant bacteria in milk. In Ethiopia, mastitis is one of the most prevalent diseases of dairy cows and reduces the efficiency of milk production. The overall objective of this PhD thesis was to contribute to the knowledge on mastitis in Holstein Friesian × Zebu breed market-oriented dairy farms in North-Western Ethiopia.

In a study on 510 cows, 33% of the quarters and 62% of the cows had subclinical mastitis (SCM). Coagulase negative staphylococci (CNS) and Staphylococcus aureus were the pathogens most frequently isolated. A number of risk factors for mastitis were identified, such as a history of clinical mastitis (CM), checking the udder for CM and Holstein Friesian blood level.The genetic relatedness of the S. aureusisolates was studied using spa-typing. Although twenty different spatypes were identified, almost 70% belonged to the same cluster, suggesting within and between farm transmission. In addition, these isolates were found to be mostly resistant to penicillin/ampicillin (86%) and tetracycline (54%).

A normative bio-economic simulation model estimated the total costs of mastitis under Ethiopian circumstances to be 6,709 Ethiopian birr (ETB) (1 ETB = 0.0449 USD) per farm per year with considerable variation between farms. The average costs of a case of CM and SCM were 3,631 ETB and 147 ETB, respectively. A related studybased on empirical data estimated the average total failure costs of mastitis to be a little lower, at 4,765 ETB per farm per year, of which54% was due to SCM. The average total failure costs per lactating cow per year were 1,961 ETB, again with large variation in costs between farms. Milk production losses (particularly due to SCM) and culling are the main cost factors of mastitis.

Successful implementation of udder health programs requires strategies that enhance farmers' motivation to improve udder health in their herds. A study was conducted to identify determinants of motivation of Ethiopian dairy farmers towards controlling mastitis. The majority of dairy farmers (93%) had a positive intention to implement measures to control mastitis. When asked about specific mastitis control measures (improving cleaning of the udder, stall hygiene, feeding of cows and foremilk stripping), a smaller majority of farmers said to have a positive intention to implement these. To increase the intention of dairy farmers to implement mastitis control measures, interventions directed at changing their attitude and their subjective norms are expected to give the largest improvement in mastitis control behavior in North-Western Ethiopian dairy farmers.

The practical knowledge generated in this thesis in combination with the motivational factors of the farmers give valuable handles on improving udder health in Ethiopian dairy cattle. This will contribute to increase sustainability and food security of the communities around these small dairy farmers.