Aim: A cross-sectional study was conducted to estimate the prevalence and associated risk factors of mastitis in dairy cows.

Materials and Methods: A total of 302 dairy cows were selected from all volunteer dairy farms in Ambo district of West Shewa Zone, Oromia region. Thorough clinical examination was made on all lactating cows for evidence of signs of clinical mastitis followed by collection of milk sample for examination of gross changes of milk secretion and California mastitis test.

Results: About 126 (41.7%) cows had mastitis, of which 9.9% (30/302) were clinical and 32.8% (96/302) were subclinical mastitis cases. The quarter level prevalence was 44.4% (536/1208), comprising 9.3% (112/1208), clinical and 32.8% (396/1208) subclinical forms of mastitis. In addition, 5.5% (66/1208) of teats were found to be blind on the clinical examination of udder and teat. The Chi-square analysis of intrinsic risk factors revealed significantly (p<0.05) higher prevalence of mastitis in crossbred cattle (47.2%) than indigenous (15.4%), in cattle above 7 years (75%) than less than 2-6 years of age (28%) and cows given more than 4 calves (81.3%) than those with less than 4 calves (31.1%) irrespective to their lactation stage. There was also significantly (p<0.05) higher mastitis prevalence in larger (46.6%) than smaller herds (24.2%) and among the farming systems in semi-intensive (47.1%) and intensive (42.3%) than extensive (8.1%) management system.

Conclusion: This study indicated a higher prevalence of mastitis linked with several risk factors. Thus, early diagnosis and regular screening of cows for subclinical mastitis together with proper therapeutic management of clinical cases are of paramount importance. Moreover, control and prevention strategies should be designed and implemented with great emphasis given to risk factors to reduce bovine mastitis and its impact on milk production and food security.

Keywords: Ambo district, California mastitis test, dairy cows, mastitis, prevalence, risk factors.

1. Radostits, O.M., Gay, C.C., Hinchcliff, K.W. and Constable, P.D. (2007) Mastitis. In: Veterinary Medicine: A Text Book of Disease of Cattle, Sheep, Pigs, Goats, and Horses. 10th ed. Bailliere Tindall, London. p674-762.

2. Eriskine, R.J. (2001) Intramuscular administration of ceftiofur sodium versus intra-mammary infusion of penicillin/novobiocin for treatment of Streptococcus agalactiae mastitis in dairy cows. J. Am. Vet. Med. Assoc., 208: 258-260.

3. Bartlet, P., Joust, V.W., Devid, J.W. and Charles, D.G. (1991) Temporal patterns of lost milk production following clinical mastitis in a large Michigan Holstein herd. J. Dairy Sci., 74: 1561-1572. [Crossref]

4. Brinda, M., Moga-Manzat, R., Brezovan, D. and Toth, E. (2009) Study on correlation between different diagnosis and tests in bovine mastitis. Lucrari Stiinlifice Med. Vet., 12(1): 257-262.

5. Lidet, G.M., Benti, D., Feyissa, B. and Abebe, M. (2013) Study on prevalence of bovine mastitis in lactating cows and associated risk factors in and around Areka town, Southern of Ethiopia. Afr. J. Microbiol. Res., 7(43): 5051-5056. [Crossref]

6. Fufa, A., Gemechis, F., Bekele, M. and Alemayehu, R. (2013) Bovine mastitis: Prevalence, risk factors and bacterial isolation in small-holder dairy farms in addis Ababa City, Ethiopia. Glob. Vet., 10(6): 647-652.

7. Tadesse, T., Mulisa, M.K. and Teka, F. (2014) Bovine mastitis: Prevalence and isolation of major pathogens in dairy farms of selected sites in Addis Ababa, Ethiopia. Appl. J. Hyg., 3(3): 31-37.

8. Endale, M., Eyob, E., Addisu, A. and Naod, T. (2016) A study on the prevalence of bovine mastitis and associated risk factors in and the surrounding areas of sodo Town, Wolaita Zone, Ethiopia. Glob. J. Sci. Front. Res. D Agric. Vet., 16(2), 1-9.

9. GOE, LMP, (2007) Government of Ethiopia, The Livestock Master Plan Study Report. International Livestock Research Institute (ILRI), Addis Ababa Ethiopia.

10. CSA, (Central Statistics Agency). (2003) Agricultural Sample Survey 2001/2. Report on Area and Production for Major Crops (Private Peasant Holdings, Meher Season) Addis Ababa, Ethiopia.

11. Thrusfield, M. (2005) Veterinary Epidemiology. 3rd ed. Black Well Science, Singapore. p181-189.

12. Tesfahewot, Z., Aya, T. and Bayecha, R. (2013) Study on prevalence, bacterial pathogens and associated risk factors of bovine mastitis in small holder dairy farms in and around Addis Ababa, Ethiopia. J. Anim. Plant Sci., 23(1): 50-55.

13. Biffa, D., Debela, E. and Beyne, F. (2005) Prevalence and risk factors of mastitis in lactating cows in Southern Ethiopia. Int. J. Appl. Res. Vet. Med., 3: 189-198.

14. Quinn, P.J., Carter, M.E., Markey, B. and Carter, G.R. (1999) Clinical Veterinary Microbiology. Moshy, London, UK. p21-66. [PubMed]

15. Delelesse, G.D. (2010) Study on prevalence of bovine mastitis on cross breed dairy cow around Holeta areas, West Shoa zone of Oromia, Ethiopia. Glob. Vet., 5(6): 318-323.

16. Abera, M., Demsie, B., Aragaw, K., Regassa, F. and Regassa, A. (2013) Isolation and identification of Staphylococcus aureus from bovine mastitic milk and their drug resistance pattern in Adama town, Ethiopia. Afr. J. Dairy Farming Milk Prod., 1(2): 19-23.

17. Mekibib, B., Furgasa, M., Abunna, F., Megersa, B. and Regasa, A. (2010) Bovine mastitis: Prevalence, risk factors and major pathogens in dairy farms of Holeta town, Central Ethiopia. Vet. World, 3: 9. [Crossref]

18. Haftu, R., Taddele, H., Gugsa, G. and Kalayou, S. (2012) Prevalence and bacterial cause, and antimicrobial susceptibility profile of mastitis isolates from cows in large-scale dairy farms of Northern Ethiopia. Trop. Anim. Health Prod., 44: 1765-1771. [Crossref] [PubMed]

19. Tafa, F., Terefe, Y., Tamerat, N. and Zewdu, E. (2015) Isolation, identification and antimicrobial susceptibility pattern of coagulase positive Staphylococcus from subclinical mastitic dairy cattle in and around Haramaya university, Ethiop. Vet. J., 19(2): 41-53. [Crossref]

20. Duguma, A., Tolesa, T. and Yohannes, A. (2014) Prevalence of clinical and subclinical mastitis on cross bred dairy cows at Holleta Agricultural Research Center, Central Ethiopia. J. Vet. Med. Anim. Health, 6: 13-17. [Crossref]

21. Jha, A.K., Hoque, M.N., Kamal, M.M., Rahman, M.M., Bhuiyan, M.M.U. and Shamsuddin, M. (2010) Prevalence of mastitis and efficacy of different treatment regimens on clinical mastitis income. SAAR J. Agric., 8(1): 79-89.