Mastitis is defined as an inflammatory reaction of the parenchyma of the mammary gland which brings huge economic loss to dairy farmers because of the reduced milk production, expenses of treatment, labour costs, discarding of milk following treatment due to the deleterious effects on the chemical and cytological composition of milk, premature culling and sometimes death (Yang et al., 2012). Mastitis can occur in clinical and subclinical forms based on severity, nature of exudate, duration and primary cause. Clinical mastitis is the symptomatic form and characterized by physical, chemical and bacteriological changes in milk such as presence of blood, water, flakes and pus having clots as well as pathological changes evident in the glandular tissue of udder. According to its severity, rapid onset and duration, clinical form is further classified into peracute, acute, subacute and chronic forms (Fagiolo et al., 2007). Progressive fibrosis accompanied by enlargement, and in severe cases, atrophy of mammary gland is seen in chronic form. While in subclinical mastitis, somatic cell count increases with normal appearance of udder and milk. So, it can be detected by screening tests such as California Mastitis test, detection of bacterial agents and electrical conductivity. Mastitis incidence is largely influenced by management practices, interaction between a variety of microbial infections and host responses in the udder (Fagiolo et al., 2007). Moreover, mastitis being multifactorial in nature, no proper control measures are evident to contain the disease (Kavitha et al., 2009).
India is the highest milk producing country in the world with a total milk production of 209.96 million tonnes and with a population of 109.85 million (Livestock Census, 2019), nearly 45% of the total milk production of India is contributed by buffaloes (Annual Report, 2021-22), and it is twice as rich in fat and other constituents of milk as compared to the cow milk (Kumar et al., 2017). Bovine mastitis poses a significant impact on dairy farm economy. The first comprehensive report on economic loss caused by mastitis in India was published in 1962 reporting an annual loss of Rs. 52.9 crores (Dandha & Sethi, 1962). However, later on with the upcoming of Operation flood milk yield of bovine population increased tremendously which came up with many fold increment in economic loss too. Reshi et al. (2015) reported the annual economic losses due to bovine mastitis to be Rs. 7165.51 crores in India.
Although buffaloes are less susceptible to mastitis than cattle because of thicker streak canal epithelium (Uppal et al., 1994) but a high mortality rate of the calves is seen in the first three months of life due to maternal mastitis, which further leads to decline in buffalo productivity (Akhtar and Ali, 1994). The incidence of clinical mastitis varies as per the physiological status of animal and more predominantly with the environment. The environment factors include the non-genetic factors such as season of calving, period of calving, parity, feeding regime, milk production levels, etc. that significantly affect the incidence of mastitis in dairy herds. A number of researchers have reported significant effect of different non-genetic factors like season of calving (Joshi and Shrestha, 1995; Taraphder et al., 2006), period of calving (Chand et al., 1995), parity (Chand et al., 1995; Joshi and Shrestha, 1995; Taraphder et al., 2006; Sharma et al., 2013; Jingar et al., 2014) on incidence of clinical mastitis in buffaloes. Taraphder et al. (2006) reported 8.75% incidence of clinical mastitis in winter season while 16.28% in rainy season and they also observed a consistent increase in mastitis incidence with increase in parity. Jingar et al. (2014) reported that incidence of mastitis increased from 22.78% (first parity) to 32.89% (fourth parity) during different parities. For bringing out increased milk production, the phenotypic selection is done which predisposes the milch animals for environmental influences subsequently causing mastitis infection (Sinha et al., 2021). So, the present study was carried out to investigate the effect of season of calving, period of calving, parity and levels of milk production on the incidence of clinical mastitis in Murrah buffaloes.