Prevalence of bovine subclinical mastitis in Gondar town and surrounding areas, Ethiopia

G Almaw, W Molla and A Melaku*

Faculty of Veterinary Medicine, University of Gondar, P.O.Box 196, Gondar, Ethiopia
tiwawyedegera@yahoo.com
* Faculty of Veterinary Medicine, Putra University, Malaysia

Abstract

This cross-sectional study was conducted during the periods of August 2005 to January 2006 in Gondar town and surrounding districts to determine the prevalence of subclinical mastitis.

Based on California Mastitis Test (CMT) of the 337 cows examined, 85 (25.22%) had subclinical mastitis. And among the 1330 quarters examined 140 (10.52%) were CMT positive and 18(1.4%) blind. Of the study areas Dabat has got the highest prevalence (40%) and the lowest was at Debark (10%).

Crossbred cows were found to be affected significantly (p-value < 0.05) by the disease compared to locals.

Key words: crossbreds, local zebu, prevalence

Introduction

Despite Ethiopia is the most populous country in cattle than any African country; up to 1997 the per capita milk consumption was 16 kg, which was lower than other countries in the region (Asfaw 1997). In the livestock development policy to improve the per capita milk consumption, improvement of the genetic potential of the indigenous zebu through breeding with high-grade exotics was included (Asfaw 1997). And in the years to come a significant percentage of dairy cattle population in Ethiopia would be improved breeds, which are susceptible to most diseases including mastitis. According to Lemma et al (2001) of the major diseases of crossbred cows in Addis Ababa milk shed mastitis was the second most frequent disease next to reproductive diseases. Mungube et al (2005) estimated the economic losses from mastitis in the urban and periurban areas of Addis Ababa, Ethiopia, to be US $ 58 per cow per lactation. The prevalence of clinical and sub clinical mastitis in Ethiopia range from 1.2 to 21.5% and 19 to 46.6%, respectively (Hussein et al 1997, Bishi 1998, Kassa et al 1999, Lemma et al 2001, Workineh et al 2002, Kerro and Tareke 2003). However, most of these studies were carried out in Addis Ababa and its surroundings, capital of the country and fail to represent the occurrence of mastitis under different management and environmental situations in other regions of the country.

To the authors’ knowledge, in Amhara Regional State, mastitis is not a disease that is well considered, despite its economic and public health importance. An Austrian assisted project named Integrated Livestock Development Project (ILDP) is working in the region since 1998 to improve farmers’ livelihood. This project provides crossbred heifers to poor farmers and organized these smallholder farmers to form cooperatives. These cooperatives supply milk to Fasil milk plant provided to them by the project. And these farmers were in need of knowing the udder health status of their cows. This study was therefore primarily conducted to determine the prevalence of subclinical mastitis in these smallholder farms coordinated by ILDP.

Materials and methods

Study area

This study was conducted in Gondar town and surrounding districts (ILDP sites) including Debark, Dabat, Kolladba and Tsion. The cattle population in that order was 5375, 74636, 92188, 174516 and147443. Gondar town is 780 km north of the capital city Addis Ababa and is 2220m a.s.l, with 1172mm mean annual rainfall and 19.7^oC average annual temperature. Its area is 257 km². Dabat and Debark are 70 and 100km away from Gondar town, respectively.  The total surface area of Dabat is 1223.26 km² and Debark has got 1478.77 km². Kolladba is 35 km from Gondar town and has got a hot climate and because of this tick bite was a challenge in the area.  It has a total surface area of 1286.18 km^2. Tsion is 42 km from Gondar town on the way to Addis Ababa (Gondar Town Agricultural Office 2006, CSA 2008).

Study animals and husbandry

The study animals were lactating local zebu and Holstein x Zebu crossbred cows in the study area. Grazing and crop residue feeding were widely practiced but farmers provide special treatment to crossbred cows both in feeding (concentrate feeding) and housing. Cows were mainly kept in open shelters with floors made by arranged stones. In Gondar town concrete flower was provided to most cows. The milking system in local zebu was 100% restricted suckling (RS) where calves were allowed to stimulate milk letdown and then restrained until milking was completed. After milking calves were allowed to suckle and spend some time with their mothers (for 30 minutes to one hour) and then separated. In crossbreds they practiced non suckling milking system but in some areas, they adopted the local zebu milking system (restricted suckling). In this non suckling milking system (artificial calf rearing, AR) calves were separated from their dams within a few days after birth and fed with whole milk.

Study design

Sample size determination and sampling strategy

The study was a cross-sectional study conducted during August 2005 to January 2006. Prevalence of subclinical mastitis was determined cross sectionally in Gondar town and surrounding districts at cow and quarter level based on indirect test (California Mastitis Test, CMT). Prevalence was calculated according to the formula given in Thrusfield (2005).

Prevalence = No. of animals with the disease/No. of animals at risk

Sample size was determined at 95% confidence interval, 5% precision and 34% expected prevalence from previous studies (Almaw et al 2008) and found to be 344 animals. From previous experience getting list of lactating cows (sampling frame) was difficult, as farmers do not keep records. Therefore, the households list was recorded by employing data collectors and was taken as a sampling frame. The number of households to be selected was determined by dividing sample size with herd size, in this case 344/2=172, since the average herd size was two. Simple random sampling was considered to select the study animals, assuming the difference in clusters (households in this study) was minimal when the herd size is so small. All lactating cows in the selected household were included in the study. And finally 337 cows were used for the study. 

Sample collection and CMT test

The udders and especially teats were cleaned and dried before sample collection. Each teat end was scrubbed with cotton moistened with 70%ethyl alcohol. A squirt of milk, about 2 ml from each quarter was placed in each of four shallow cups in CMT paddle. And then an equal amount of the CMT reagent was added to each cup. A gentle circular motion was applied to the mixtures in a horizontal plane for 15 seconds. A cow or a quarter was considered to have subclinical mastitis if CMT score is 1, 2 or 3 and the California Mastitis Test (CMT) was carried out according to the method described by Quinn et al (1999).

Data analysis

Confidence interval for prevalence was calculated according to the formula given in Thrusfield (2005). And breed as a risk factor for mastitis was tested using X²-test

Results and discussion 

Prevalence

Out of 337 cows examined, 85(25.22%) had subclinical mastitis. Among the study areas Dabat has got the highest prevalence (40%) and the lowest was at Debark (10%) (Table 1). And among the 1330 quarters examined 140 (10.52%) were CMT positive and 18(1.4%) blind. The occurrence of mastitis was higher (Table 1) in crossbreds compared to the local zebu and the difference was statistically significant (p-value < 0.05).

The overall prevalence of subclinical mastitis in the present study (25.22%) was relatively lower than previous studies in Ethiopia. Bishi (1998), Workineh et al (2002), and Almaw et al (2008) reported 34.30, 38.2 and 34.4%, respectively. However, in Dabat, one of the study sites in the present study a higher prevalence (40%) was found. In a study carried out in Tanzania in a similar herd structure as high as 90.3% (Kivaria et al 2004) subclinical mastitis prevalence was reported. Mastitis is a complex disease and the difference in results could be due to difference in management system between the farms. The lower occurrence of mastitis in local breeds in addition to genetic factors could be attributed to RS milking practice. Previous and recent works support the importance of suckling both in the calf and cow including udder health (Mejia et al 1998, Fröberg et al 2008). These days even in developed countries there is a rising consumer demand for production systems that comply with the animals’ natural behavior.

In most studies the majority of the cases of mastitis were subclinical compared to clinical mastitis in both breeds (Kassa et al 1999; Hussein 1999; Workineh et al 2002; Kerro and Tareke 2003).  In Ethiopia, the subclinical form of mastitis received little attention and efforts have been concentrated on the treatment of clinical cases (Hussein et al 1997). According to Mungube et al (2005) losses associated with subclinical mastitis (SCM) in crossbred dairy cows in the central highlands of Ethiopia was found to be US$38 for each cow per lactation. Ethiopian farmers specially smallholders were unaware of the invisible loss from subclinical mastitis (Hussein 1999) and were also true in Tanzanian and Ugandan farmers (Kivaria et al 2004, Byarugaba et al 2008). In this study too All of the farmers practice hand milking and their knowledge about mastitis was only on clinical mastitis; none of them new about subclinical mastitis. They were surprised during our field work when they saw CMT positive milk reaction while it appeared to them normal milk before the test was conducted.

Extensions packages that increase farmers’ awareness on subclinical mastitis would be helpful in mastitis control and improve farmers’ income. Bacteriological studies which would help to identify contagious and environmentsl pathoges, important information in mastitis control would also benefit these low income farmers.

Conclusion  

• Although the overall prevalence of subclinical mastitis in the present study (25.22%) was relatively lower than previous studies in Ethiopia, given the farmers unawareness on subclinical mastitis it can be said mastitis is still a disease that would threaten the growing dairy industry. And this figure, a prevalence of 25.22% is not in the acceptable limit. Therefore, to reduce the prevalence the disease different epidemiological factors that interplay in mastitis occurrence should be studied.
   

Acknowledgement  

The authors’ gratefully acknowledge the Research and Publication Office of University of Gondar, and Integrated Livestock Development project (ILDP) for funding the research project. We are also grateful to farmers for their all round participation.

References 

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Received 3 January 2009; Accepted 8 April 2009; Published 1 July 2009

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