The study was conducted in urban, peri urban and rural areas (Instructional Dairy Farm, Laxman Bag Gaushala, Mahajantola Farm, Kamdhenu Dairy Farm, Kuthulia, Bichhiya, Maidani, Silpara, Amilki, Gangapur, Govindgarh etc) of Rewa district of Madhya Pradesh (India) located between 24° 18’ and 25° 12’ north latitudes and 81° 2’ and 82° 18’. Land area of Rewa district is 6,240 km². It has a humid subtropical climate, with cold, misty winters, hot summer and a humid monsoon season. This district has been naturally bestowed with immensely rich domestic livestock diversity. Livestock provides livelihood to the rural community and this also provide employment for the people in this region.

Epidemiology of SCM in cattle was studied in lactating dairy cows of different risk factor. The standard questionnaire was prepared to collect the information from the organized/ unorganized farms/village taking different parameters, about individual animals, breed of cattle, age, lactation number (parity), season and breed. The milk samples were collected from 944 quarters of 242 cows during June 2018 to July 2019.

The dairy farms were physically inspected for cleanness, handling, milking procedures and other factors associated with mastitis. The udder and every individual teat was examined clinically, using visual and through manual palpation. The glands were palpated for indurations and asymmetry. Teat ends were observed for alterations such as scars, wounds, patent teat orifice and ease of milking. The udder was also examined to ascertain the abnormality in the form of inflammatory swelling, fibrosis etc. Milk was grossly examined for discoloration, clots or flakes, pus, blood staining and consistency (Quinn et al., 2002).

Modified California Mastitis Test (mCMT) was used for screening of lactating dairy cattle as cow side test on the spot to confirm the positive SCM milk samples. In brief mCMT, a plastic paddle with four chambers or shallow cups was used to perform this test. About 3 ml of milk was directly striped into the labeled cups as Left Fore (LF), Left Hind (LH), Right Fore (RF) and Right Hind (RH), from the respective four quarters. Then approximately equal quantity of the test reagent (3% Sodium Lauryl Sulphate/ CMT reagent) was added to each cup. The mixture of the milk and reagent was shaken gently in a rotating manner of the paddle in the horizontal plane. The paddle cups contained milk and reagent was rotated for 10 seconds and results were recorded. For the interpretation of severity of mastitis, different scoring system for mCMT was considered during present study. Based on the thickness of the gel formed by mCMT reagent-milk mixture, test results were scored as 0 (negative), + trace ++ (weak positive), +++ (distinct positive) and ++++ (strong positive) (David et al., 2005; Sharma et al., 2018).

The milk sample was collected from each teat of cow indicating mCMT positive for SCM. The udder and teats were cleaned and washed with potassium permanganate 0.01% then wiped with clean cloth. First few streams of foremilk was discarded and then about 25ml of milk from each affected quarter was collected in fresh, sterile, labeled screw cap test tubes and brought to the laboratory for further examination.

In the present study, cows were screened by mCMT, milk pH, ER and SCC. The mean value of milk pH, ER and SCC was 6.57±0.04, 356.67±13.33 and 1.52±0.12 × 105 cells/ml, respectively in apparently healthy cows, while the corresponding values changed significantly (p<0.05) with 7.55±0.04, 315.00±19.45 and 17.22±3.12 × 105 cells/ml SCM infected cow (Table 1). These findings are close in accordance with the results of Ogola et al. (2007), Galfi et al. (2015), Panchal et al. (2016) and Mourya et al. (2020).

The present study was conducted on a total of 242 milking cows, out of these 76 lactating cows were mCMT positive. The overall prevalence of SCM was found to be 31.40% on the basis of animal (Table 2). These findings are in close agreements with the reports of Maheshwari et al. (2016), Swami et al. (2017), Constable et al. (2019) and Shaikh et al. (2019) who have recorded prevalence of SCM to be 27.81%, 35.00%, 31.21% and 33%, respectively. However, higher prevalence was reported by Mir et al. (2014), Mekonnen et al. (2017) and Ndahetuye et al. (2019) as 57.80%, 37.20%, 62.00%, and 76.25%, respectively. Sharma et al. (2018) also recorded SCM occurrence rate to be higher at unorganized farms (65.08%) than at organized ones (51.82%) in the of Jammu region of J & K.

A total of 76 quarters from 968 quarters were positive to mCMT. The overall quarter wise prevalence of SCM was 7.85% (Table 2). There was a variation of mCMT score even in different quarters of individual lactating cow. The higher prevalence of 23.00% and 31.55% was reported by Patel and Trivedi (2015) and Mourya et al. (2020), respectively in the infected quarters of cows. Most important concern was about 2.48% of permanent functional loss of teats (blind teats) in cows (Table 2). Sharma et al. (2018) have recorded 9.00% blind teats in cows. Hence, the variation in prevalence of SCM in different studies may be attributed to various risk factors responsible for development of mastitis. These factors are present at both cow and quarter level. It might be due to the fact that the farmers could not maintain proper hygiene at dairy farm due to non-scientific rearing of animals. Ergun et al. (2004) stated factors like herd size, milking method practice, agro climatic conditions of the region, variations in socio-cultural practices, milk marketing, literacy level of the animal owner and feeding practices were affecting the prevalence of SCM.

On quarter basis prevalence of SCM in cows, hind quarters (10.54%) were mostly affected as compared to fore quarters (5.17%). In addition, the individual quarter wise prevalence was found to be highest in left hind quarter (15.70%) followed by left fore quarter (5.78%), right hind quarter (5.37%) and right fore quarter (4.54%) (Table 3). Mourya et al. (2020) reported the highest prevalence 22.14% in right fore quarter followed by 21.08% in right hind quarter, 19.32% in left fore quarter and the lowest prevalence of 18.18% in left hind quarter of cattle with SCM. Qadri (2015) and Maheshwari et al. (2016) also reported higher prevalence of 11.23%, 9.03%, and 32.25%, 27.25% in right and left side quarters, respectively. While, Srinivasan et al. (2013) reported the quarter-wise prevalence in left fore, left hind, right fore and right hind quarters to be 11.11%, 46.30%, 5.50% and 37.04%, respectively. Singh et al. (2010) opined that the incidence of SCM occurs higher in hind quarters as compared to fore quarters and this could be attributed to greater exposure of the hind quarters to contamination with dung and urine. This might be due to the fact that hind quarters are highly prone to contamination with dirty and large amount of milk is produced from hindquarters and as a result, the pressure on teat canal forces the canals to be opened widely, which allow entrance of microbes. Akhtar et al. (2012) added that more involvement of hind quarters might be due to more frequent exposure to dung and urine, large capacity and mass, greater vulnerability to direct trauma and relatively more closeness to the floor as compared to fore quarters.

The lactation stage was divided into early lactation (1 to 3 months), mid lactation (3 to 6 months) and late lactation (6 months onwards) till drying off. The prevalence of SCM in relation to stage of lactation in cattle revealed highest (36.54%) in early stage of lactation followed by late stage of lactation (34.38%) and mid stages of lactation (27.78%) (Table 4). This observation supports the findings of Pal and Verma (1991), Islam et al. (2011) and Maheshwari et al. (2016). The high rate of SCM during the early stage of lactation may be due to the fact that high yielding cattle with enlarged status of udder are highly prone to infection and inflammatory process. The higher incidence of SCM is more common in early lactation phase which could be due to physiological stress of lactation and alterations in homeostasis mechanisms (Rassol et al., 1985). In contrast, higher prevalence of SCM in late stage of lactation was recorded by Islam et al. (2019) and Sinha et al. (2011) in Bangladesh. Sharma et al. (2011) reported that dairy cows seemed to have more oxidative stress and low antioxidant defense during early lactation or just after parturition than advanced pregnant and this appears to be the reason for their increased susceptibility to production diseases and other health problems.

The status of SCM in cow having different lactation numbers ranging from 1^st to 7^th and more parity numbers was observed. The variable prevalence of SCM was observed at different parity. The highest prevalence was 66.67% in 2^nd parity, followed by 43.33% in 1^st parity, 40.75% in 4^th parity, 19.44% in 5^th parity, 13.04% in 5^th parity and lowest (8.57%) in 7^th and above lactation (Table 4). Similar findings of higher prevalence of SCM in 2^nd parity were recorded by Nauriyal and Verma (2009) in cattle. Whereas, higher prevalence in 4^th parity were recorded by Islam et al. (2011), Maheshwari et al. (2016) and Mourya et al. (2020). The highest prevalence of SCM was found in 3^rd parity by Sinha et al. (2011) and Bhuiyan et al. (2020). This observation also supported the reports of Rasool et al. (1985) and Devi et al. (1997) who reported an increasing incidence of SCM with advancing age (parity) and lactations.

Tiwari et al. (2008) opined that incidence of mastitis increases as the lactation progresses and it attains a highest proportion during third and fourth lactation when the cows produce more milk and the udder becomes pendulous and more prone to infection. In addition, the increased prevalence of SCM in pleuriparous lactating cows might be due to increase in teat patency and frequency of previous exposure (Ayano et al., 2013). It has been proposed that incidence of infected quarter increases with the age and parities (Sharma et al., 2007; Sharma and Maiti, 2010). Multiple studies have also indicated that increasing parity increased the risk of mastitis in cows (Tiwari et al., 2008; Tufani et al., 2012).