Status of mastitis in lactating goats at Sokoine University of agriculture and neighbouring smallholder farms in Morogoro Municipality, Tanzania

Small ruminants play an important role in the nutrition and income of people worldwide. It has been estimated that there are more than 460 million goats worldwide producing about 4.50 million tons of milk and 1.20 million tons of meat annually (Hansen and Perry 1994). These animals serve primarily as sources of meat, but also provide milk, skins and manure. Sheep and goats produce about 16% of the world's meat and similar figures for milk and skin. Small ruminants in Africa produce only 14.0% of the world's milk and 15.0% of the world's skin.

In Africa both goats and sheep are widely distributed extending from arid and semi desert to humid rain forest regions and represent 20.2% and 28.9% of the total population of ruminants in Sub-Saharan Africa. In the subsistence sector, pastoralists and agro-pastoralists depend on them for their livelihood.

The commonest breed of goats in Tanzania is the Small East African goat. There was introduction of exotic breeds of goats in late 1980’s in Tanzania and these included Norwegian Landrace, Toggenburg, Anglonubian and Saanen for milk production; Kamorai and Boer goats for meat production and the dual purpose Blended goats (Das and Sendalo 1989).

Several traditional systems of small ruminant production have been described in Sub-Saharan Africa (Matthewman 1980; Wilson 1986; Devendra 1986) and Tanzania (Mtenga et al 1986). Wilson (1986) grouped small ruminant production systems into two major categories, that is, traditional and modern systems. According to Njombe (1986) the three main types of traditional management of small ruminant production practiced in Tanzania are extensive (pastoral), semi-extensive (agropastoral), and intensive (agricultural or village) systems. The modern small ruminant production system has been practiced mainly in governments and research institutions (Adu and Lakpin 1988) due to high capital requirement. In Tanzania, modern large scale small ruminant units are found in some research and training institutions.

There are about 11.6 million goats in Tanzania compared to 15.0 million cattle and 3.50 million sheep (Ministry of Agriculture and Cooperative 2001). Sheep and goats play an important role in the nutrition and income of small holder farmers in Tanzania (Mtenga et al 1986; Connor et al 1990). They provide meat, milk, skins, manure and they also serve as an investment that can be easily converted into cash when needs arise (Njombe 1993). In addition to these functions, goats can also be used for research purposes.

Constraints affecting the productivity of goats in smallholder farms include diseases, theft, land scarcity, labour shortage and, lack of veterinary extension services and capital. The major breeds of goats in the wo disease syndromes reported in Tanzania include helminthosis, pneumonia, orf ectoparasites, diarrhoea, contagious caprine pleuropneumonia and these have been responsible for significant morbidity and mortality (Kusiluka et al 1996). Although mastitis is not consided to be major disease of economic importance in Tanzania because of the introduction exotic dairy breeds of goats in country the disease could be of economical importance in the goat production. This study was, therefore, carried out to establish the status of mastitis and to identify the microbial flora associated with mastitis in goats kept at SUA and neighbouring smallholder farms in Morogoro municipality, Tanzania.

Methodology

This study was conducted between November 2004 and April 2005 at Sokoine University of Agriculture goat units (Magadu and Animal Research Unit). Smallholder farms at Mng’ongo, Visegese and Mzingwi villages located on the slopes of Uluguru mountains east of SUA were also involved in the study. Magadu dairy farm had a total of 57 goats and, 22 lactating does were used for the present study. Animals that were used for the study were crosses of Norwegian Landrace dairy goats with the Small East African goats. Animals are usually herded throughout the day and lactating does are given maize bran mixed with cotton seed cake as supplements during milking. At night, animals are kept in the houses with concrete floor. The does were milked once per day during morning hours. Before milking the udder was washed using warm water and only one towel was used to dry the teats for all the animals. The animal research unit (ARU) keeps the indigenous Small East African goats that are also herded. At night, they are kept in house with a raised wooden slatted floor. The total number of goats at the time of study was 44 and only four lactating goats were available for the study. The smallholder farmers in Mng’ongo, Visegese and Mzingwi villages kept about two to seven crosses of Saanen with Small East Africa goats per household. The animals were kept in houses with wooden floor and fed under the zero grazing system. Indigenous goats were herded and kept in houses with earth floor. During milking, the udder was washed with cold water and the animal was given maize bran as a supplement. A total of 12 Saanen does and five SEA goats were screened for mastitis in the smallholder farms.

Data collection

The following data were collected and recorded for each farm

Farm data

Visit date, owner’s/farm name, farm type (institution i.e. SUA or smallholder farm), housing (ground floor or raised floor houses), feeding system (herding/free range or zero grazing);

Animal data

Animal identification, breed, Kidding date, CMT scores, Laboratory findings

All lactating does in the visited farms were screened for subclinical mastitis using CMT as described by Schalm and Noorlander (1957). Briefly, each teat was cleaned with alcohol 70.0% and small amount of milk was squirted from each teat into the separate compartments of a plastic paddle that has shallow cups marked A, B, C and D. An equal amount of CMT reagent was added to the milk in each cup. The paddle was gently rotated to mix the contents. The reaction was read within 10 seconds, while continuing to rotate the paddle because the reaction disappears within 20 seconds. A total of 43 does were screened (i.e. 85 gland halves because one of the does had a blind teat). The CMT reaction was scored and recorded for each half gland (teat) according to the chart of grading (Ikram 1997) as shown in Table 1.

For bacteriological examination milk samples were taken from all lactating does after washing the udder with 70.0% alcohol. The first fore milk stream was discarded and about 10.0 ml of milk from each teat was squirted into a well-labeled bijou bottle. The sample was transported to the laboratory at the Faculty of Veterinary Medicine, SUA and immediately inoculated on MacConkey and blood agar and incubated at 37.0oC for 24 to 48 hours. After 24 – 48 hrs representative bacterial colonies were selected and subcultured into MacConkey and blood agar for 24 hours. Colonial morphology was used as the first identification step for the bacterial isolates. The bacterial isolates were then identified by the Gram staining and biochemical characterization according to standard procedures (Carter et al 1991)

Collected data were entered in Epi-info database (Coulombier et al 2001) and statistical differences between proportions were determined using Epi info 6 Epitable program with the critical probability of p=0.05. The following were considered as outcome variables, CMT positivity and bacterial growth, where as exposure variables were farm type, post kidding period and breed.

Results

Status of subclinical mastitis in goats at SUA and smallholder farms is shown in Figure 1. Overall, the CMT positivity in goats in all farms was 76.7%. Subclinical mastitis as reflected by CMT positivity was detected in 92.3% of the goats at SUA farm and 52.9% of the goats in smallholder farms. There was a significant difference in status of subclinical mastitis in goats at SUA and smallholder farms (p<0.05)

Figure 1.  CMT positivity in goats at SUA and smallholder farms in Morogoro municipality, Tanzania

The status of subclinical mastitis in the 43 screened does as reflected by CMT positivity is shown in Figure 2. Overall, the CMT positivity was highest in Norwegian Landrace goats at SUA farm and the indigenous SEA goats had the lowest CMT positivity.

Figure 2.  CMT positivity in SEA, Norwegian and Saanen crosses screened at SUA and smallholder farms in Morogoro municipality, Tanzania

When a comparison was made between the dairy crosses (i.e. Norwegian and Saanen crosses with SEA) and pure SEA goats, CMT positivity was highest in crossbred goats (p<0.05) (Figure 3).

Figure 3.  CMT positivity of crossbred and indigenous goats at SUA and smallholder farms in Morogoro municipality, Tanzania

When CMT positivity at half gland level was analysed with respect to interval from kidding to the date of screening, it was observed that animals in late lactation were significantly more CMT positive than animals in early lactation (p<0.05) (Table 2).

Out of the 85 milk samples examined for bacterial growth only five samples (5.90%) were positive (Table 3). The positive samples were among the 23 samples collected from Saanen crossbred goats from smallholder farms in Visegese (3) and Mng’ongo (2) villages. Three sample and two samples were from animals at three-month and six-month post-kidding categories, respectively. Bacterial isolates were Staphylococcus epidermis (4) and coagulase negative Staphylococcus (1). The latter was not identified to species level.

The present study has demonstrated that goats at SUA and neighbouring smallholder farms had subclinical mastitis as reflected by the high level of CMT positivity (above 75%). These results correspond with those observed in cattle and goats in the same area in which 67.6% of the screened cows were reported to be CMT positive (Mosha 1993) and 72.8% of the screened does from Norwegian, Toggenburg, AngloNubian, French Alpine and Saanen crosses were CMT positive (Moshi 1998). Mdegela et al 2004 also demonstrated that 74.5% of the cattle in smallholder farm in Morogoro municipality had subclinical mastitis. The higher level of subclinical mastitis may be a reflection of the poor milking hygiene in the farms (Blowey and Edmondson 2000). It has been well demonstrated that mastitis is a disease associated with poor hygiene (Shekimweri 1992). The predisposing factors for mastitis such as dirty houses and poor milking hygiene (such as using same towel for all teats and hand washing with cold water) were also evident in the SUA farm and might have contributed to the high level of subclinical mastitis.

The observation that over 90% of animals with subclinical mastitis were in the nine and above months category probably reflect a persistent and cumulative effect of exposure to mastitis pathogens and predisposing factors for udder infection. On the other hand, this observation may indicates that there is a low level of somatic cell in the early lactation period as supported by observations by Pettersen (1981) who reported that somatic cell counts increase with length of post kidding period. The present study has also demonstrated some differences in CMT positivity among the different breeds of animals with high percentage of positive animals being crossbred animals (Norwegian and Saanen) than SEA. This probably indicates that dairy breeds are more susceptible to mastitis than indigenous breeds.

The CMT test is based on the reaction between the CMT reagent and DNA in the somatic cells and high concentration of somatic cells leads to a higher CMT score. The somatic cell count indicates the number of neutrophils, which are directly related to grandular irritation (Smith and Rouguinsky 1977; Pettersen 1981; Sheldrake et al 1981; Dulin et al 1983; Poutrel and Lerondelle 1983). However, Wilson et al 1995 found that 90% of the differences in the goats’ SCC was not due to infection but was caused by increased days in milking, parity and reduced milk production. The fact that only one of the examined goats had clinical mastitis probably indicates that the CMT positivity was not directly related to infection in the goats. This is also supported by the fact that most of the milk samples were bacteriologically negative.

In this study the isolated bacteria were Staphylococcus epidermis and coagulase negative staphylococcus. The bacterial isolation rate in this study was lower than those reported in other studies (Manser 1986; Maisi 1990; Guha et al 1989). The low bacterial isolation rate could be explained by the following reasons;- sampling of animal at the stage where the causative bacteria have been cleared off; presence of fastidious bacteria which require special media for isolation and that were not used in this study; presence of mastitis due to non-infectious causes as reported by others (Wilson et al 1995); non mastitic goats have high somatic sell as opposed to cow (Dulin et al1983; Poutrel and Lerondelle 1983) and this could contribute to CMT reaction and; animals being treated with antibiotics prior to sampling although none of the sampled animal had a history of being treated.

 

Conclusions

• It can be concluded from this study that on the basis of CMT results, the majority of the screened animals had subclinical mastitis.
  
  
• Crosses of dairy goats appeared to be more susceptible than indigenous ones, presupposing existence of breed resistance to mastitis.
  
  
• Farmers should observe good hygiene, check their animals for mastitis using California Mastitis Test and all the positive cases should be treat in order to control and prevent the spreading of this disease to other goats, for chronic cases culling should be done.
  
  
• Farmers are encouraged to keep crosses of dairy goat which shows resistance not only to mastitis but also to other diseases.
  

I would like to thank the Government of Tanzania through the Ministry of Science, Technology and Higher Education for sponsoring this study which was in partial requirement for the bachelor of veterinary medicine (BVM). My sincere gratitude goes to Dr L J M Kusiluka and Dr E Karimuribo, lecturers in the Department of Veterinary Medicine and Public Health for their supervision during this study. Also I like to acknowledge Mr A S Kitime and Mr P Mkuchu, laboratory technicians in the Department of Veterinary Medicine and Public Health for their assistance in the laboratory work. Lastly but not least, I acknowledge all those who in one way or the other assisted in the completion of this work.