75 EAMR, Vol. 1, Issue 1 - July, 2011 INTRODUCTION Mastitis is a multifaceted disease with varied etiology, damaging the dairy economy, worldwide. Hence, the importance of timely diagnosis of this disease is represented well in saying, "A day lost is quarter lost"! Focus was to investigate the etio- prevalence of sub clinical mastitis (SCM) in Holstein x Haryana crossbred cattle. The relationship between somatic cell count (SCC) and cultural examination and efficiency of California mastitis test (CMT) and Chloride test in detecting SCM under field condition were also assessed. MATERIALSAND METHODS Milk samples were collected aseptically from 176 apparently healthy Holstein x Haryana crossbred (F1) cattle with no history of mastitis from organized dairy farms. Initial screening of crossbred cattle was performed by CMT and Chloride test. CMT was performed by the method of Pandit and Mehta (1969) and Chloride test by the procedure described in the laboratory manual of milk industry foundation (2005). The animals showing either CMT or Chloride test positive for a single udder was examined culturally in 5% ovine blood agar media for all the udders. The percent sensitivity, specificity were calculated by the formulae of Thrusfield (2005) and percent accuracy by the formula of Reddy et al. (2001). The identification of bacteria was done on the basis of colony characteristics, morphology and Gram's reaction (Tuteja et al., 2001). The SCC was done microscopically (Schalm et al. 1971). RESULTS AND DISCUSSION From 702 milk samples from 176 cows, 255 ETIO-PREVALENCE OF SUB CLINICAL MASTITIS IN HOLSTEIN X HARYANA CROSSBRED CATTLE Anirban Guha 1 and Sandeep Gera 2 1= Assistant Professor, Deptt. Of Vety. Physiology & Biochemistry, B.S. College of Veterinary Medicine & Research Centre, Jhunjhunu, Rajasthan, 2= , Professor and Head, Deptt. Of Vety. Biochemistry, College of Vety Sciences, Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana ABSTRACT : The purpose of the investigation was to evaluate the efficacy of Somatic cell count (SCC), California mastitis test (CMT) and Chloride test in detecting SCM and study its etioprevalence in Holstein X Haryana cattle. SCC prevalence for SCM, latent infected quarters and non-specific infected quarters were found to be 28.63%, 8.63% and 6.67%, respectively, when divided on the basis of International Dairy Federation criteria. Staphylococcus sp. (47.37%) and Streptococcus sp. (33.68%) was most prevalent bacterial agent. The present study revealed that CMT in conjunction with SCC is better to diagnose SCM than alone. Key words : Sub clinical mastitis, etio-prevalence, Somatic cell count, California mastitis test and Chloride test.