Prevalence of Sub-Clinical Mastitis in Cattle and Effect on Milk Quality

The pH of milk was found to be 6.7±0.1 in normal and 7.0±0.1 in SCM positive cases. The Direct Microscopic Somatic Cell Count (DMSCC) for negative animals on CMT was 0.3-0.5 million per mL and 0.6-1.5 million SCC per mL for SCM positive milk (Figure 2). The fat per cent was 3.5±0.1 in normal milk and 3.4±0.1 in SCM positive cases. The Solids Not Fat (SNF) content was 8.8±0.1 in normal milk and 8.6±0.1in SCM positive cases (Table 1).

Figure 2: Microscopic image of Somatic cell count showing epithelial cells and neutrophils and monocytes

India is self-reliant with milk production in terms of quantity but quality is inferior as per international standards.The need of the hour is to improve the quality of milk and in terms of Somatic cell count and bacteriological parameters. The Sub-clinical mastitis affected milk doesn’t pose any apparent physical changes but microscopically, bacteriological and chemical analysis shows significant variation with normal milk (Pleguezuelos et al., 2015). The increased DMSCC and reduced milk quality parameters are evident in the result of present investigation. The degradation of proteins and fats in milk will often produce off color and odor making the acceptance rate low. The increased SCC denotes increased leucocytes and epithelial cell of bovine origin. Its consumption in human is objectionable on safety of human. The enzymatic action of SCC can also add synergistically for milk spoilage (Sharma et al., 2011).

Milk acts as a vehicle for transmission of many pathogenic organism/disease to man known as milk borne zoonotic diseases. The interrupted cold chain during transport increases the number of pathogenic and spoilage causing organisms in milk and initiates the spoilage, lowering the keeping quality of milk. Bacterial invasion occurs mostly during the dry period, particularly during late gestation, and leads to glandular damage in parenchymatous tissue. The glandular tissue damage leads to increased SCC and reduced milk production (Hillerton et al., 1995). The prevalence of SCM is nearly four times more in CB cattle in comparison to ND cattle.

The increased bacterial concentration is more common in un-hygienically milking practices such as compromised udder and hind quarters cleaning, cow nutrition, pre- and post-milking teat disinfection, and clean milk parlor (Santman-Berends et al., 2016; Nigel and Douglas, 2007). The compromised floor and shed sanitation increases the chances of bacterial invasion to teat cannel (Gordon et al., 2013). The climatic factors also contribute to prevalence of SCM in cattle by increasing SCC and crossbred cattle prevalence is more since its high milk yield and low inherent factors of immunity. Similarly inherent genetic capacity and adaptation to local environment by desi cattle is more. The CB cattle are more susceptible to environment and production stress is considerably high (Saravanan et al., 2015).

The diagnosis of sub-clinical mastitis is simple with California mastitis test (CMT), mastrip test and milk pH estimation which are cow side tests and confirmation by enumeration of DMSCC using simple compound microscope. The increased SCC proportionately decreases the milk quality suggesting increased damage to udder health. The effective management of SCM in bovine reduces the zoonotic disease transmission, increases milk yield, improvement in keeping quality of milk and physico-chemical characteristics of milk. The clean milk production promotion among the farmers helps decrease the prevalence of SCM in dairy animals and improve the animal health and welfare.

Authors thank the Dean of Veterinary College, Hassan, KVAFSU for the support, suggestion and providing necessary facilities to carry out the research.

The authors declare no conflict of interest.

Jagadeesh DS contributed for plan of research, manuscript preparation, sampling and experimentation. Puttamallappa RK planned the research, prepared, corrected and revised the manuscript. Keregallokoppalu HG and Lakshminarasimhiah L contributed for sample collection and experimentation.