Abstract: To see the relation between somatic cell count (SCC) and intensity of Chemical reaction on White Side Test (WST), Bromothymol Blue Test (BTBT) and Chloride Test (CLT), a total of 785 milk samples were chemically tested using all three tests. Out of 785 samples 109, 155 and 124 showed positive reactions on WST, BTBT and CLT respectively. The positive samples were graded as +(4), + + (8), + + + (12) and + + + + (16) according to the severity of reaction and their relative somatic cells were counted. The results revealed direct relation between SCC and intensity of chemical reaction. Ninety one percent of samples with positive reactions on all three tests had SCC over 200x103 which indicates that a SCC below 200x103 may be regarded as normal in buffalo.
Introduction
The diagnosis is essential for the control and prevention of sub-clinical mastitis. Various indirect tests have been described to detect the sub-clinical mastitis (Schalm et al., 1971). As evident from its definition, the mastitis is characterized by physical and bacteriological changes in milk causing an inevitable rise in somatic cell count (Blood and Radostitis, 1989).
In addition to the SCC examined under light microscope some screening tests are also commonly used for the detection of sub-clinical mastitis. These includes Bromothymol Blue Test (BTBT), Chloride Test (CLT) and White Side Tests (WST). WST is considered as dependant upon SCC (Blood and Radostitis 1989), where as BTBT detects changes in pH (Schalm et al., 1971). Somatic cell count is regarded as the most reliable indicator for detection of sub-clinical mastitis .
A SCC count of less than 250x103/ml of milk is considered as normal in Cow (Blood and Radostitis, 1989). However studies conducted by various scientists on buffalo milk have reported a SCC ranging from 100x103 to < 300X103 to be normal (Silva and Silva, 1994; Dhakal et al., 1991; Disenhaus, 1985; Serieys, 1985).
Materials and Methods
A total of 785 milk samples were collected from 200 buffaloes by the method described by Coles (1968). The samples were than transported to the laboratory of Veterinary Physiology and Biochemistry, Sindh Agriculture University Tandojam. 4 percent NaOH, 0.13 percent silver nitrate and 10 percent potassium chromate and BTBT solutions were used in WST, BTBT and CLT respectively. The procedures were used as described by Schalm et al. (1971) and Coles (1968). Milk film was prepared and stained with Wrights-Leishman stain by method of Schalm et al. (1971).
The SCC were counted by field method i.e multiplying the number of cells in the fields (20) with working factor (30712.5) (Richardson, 1985). To facilitate statistical analysis the positive samples on chemical tests were classified as + (4), + + (8), + + + (12) and + + + + (16).
Results and Discussion
Most cases of the clinical mastitis are proceeded by sub-clinical type of mastitis. It is therefore important to detect mastitis at an early phase of development in order to make any mastitis control program successful. Some commonly used screening tests for the detecting of sub-clinical mastitis are WST, BTBT and CLT. Any physical and bacteriological change in milk causes, an inevitable rise in SCC (Blood and Radostitis, 1989). The relation between intensity of reaction of milk on indirect screening tests with their SCC is recorded in this study as to suggest most reliable and easy tests for used under field conditions. The comparison of positive samples on WST, BTBT and CLT with their relative percentage of different ranges of 5CC are shown in Table 1.
The results reveal direct relationship between SCC and severity of infection. Similar findings were described by Schalm et al. (1971). Table 2 shows percent of samples positive on all the three tests and their relative SCC. As shown 91 percent of samples showing positive reaction had SCC over 200x103/ml. In this study a SCC of less than 200x103/ml is considered normal. The findings of this study is in close agreement with that of Blood and Radostitis (1989), Dhakal et al. (1991) and Silva and Silva (1994).
This study revealed a good agreement between test scores of positive samples on three chemical test and SCC.
| Table 1: | Comparison of the Test Scores of Positive Samples on WST, BTBT and CLT with Their Relative Somatic Cell Count |
| Table 2: | Percent of the Samples showing Positive Reaction on All Three Tests SCC < 200x103 and over 200x103 |
Thus it is concluded that any of three chemical tests can be used with reasonable reliability for the early detection of mastitis. However BTBT was found to be more sensitive.