Introduction

The dairy industry from a rural perspective is massive and of major importance in rural economic growth. The performance of dairy industry is driven by rising rural employment, ease of access to technology input, increased demand for products from animal and better buying power in urban center. Despite the rapid expansion of dairy sector, quantity and quality of milk will solely depends upon the bacterial quality of the milk. Indian Dairy Industry chronically suffered by mastitis and a total monetary loss of over Rs.6000 crore per year (Ranjan et al., 2008). Mastitis which significantly reduces the milk production and performance of dairy sector and many studies have clearly shown that subclinical mastitis (SCM) is more important economically than clinical mastitis (Mdegela et al., 2009).

California mastitis test (CMT), pH and Somatic cell count tests are preferred for subclinical mastitis due to their ease of use and ability to yield rapid and satisfactory results (Alebachew and Alemu 2015).In western part of Tamil Nadu, subclinical mastitis screening is not regular schedule in the dairy farming practices. Detection of subclinical mastitis at a early stage will not only reduce the risk in conversion as clinical mastitis but also improves the quality of milk in turn fetch higher value.

Location of the Research Area

The present research work was carried out during the period between May 2016 and December 2016 in the north western part of Tamil Nadu. Between latitude and longitude of Coimbatore is 11.0168° N, 76.9558° E, latitude and longitude of Erode 11.3410° N, 77.7172° E, latitude and longitude of Karur is 10.8855° N, 78.1564° E and latitude and longitude of Tirupur is 11.1085° N, 77.3411° E.The attitude of the zone ranges from 160 to 2700 m above mean sea level. A list of all small holder dairy farms (herd size ranging from 5to 125 cows) in western zone of Tamil Nadu was selected by using a random number table and 13 dairy farms were selected. 77 lactating dairy cows of different age group, parity and lactation stages were sampled proportion to the size of the dairy farms.

California Mastitis Test (CMT)

The California Mastitis Test was done at farm level following the guidelines of the National Mastitis Council, 1999 with MastiCheck^TM reagent.

Statistical Analysis

The association between risk factors with CMT positivity was determined by binary logistic regression model using SPSS statistical package version 20 and 95% was taken as the confidence interval.

Results

Prevalence of Subclinical Mastitis at Individual Cow and Quarter Level

Out of 77 lactating cow examined, 110 representing 68.8% were CMT positive (at least one CMT-positive quarter) for subclinical mastitis in the study area. At the quarter level of 308 active quarters tested for subclinical mastitis, 121 (39.2%) were positive (Table1).

Table 1: Subclinical mastitis at individual cow and quarter level in western part of Tamil Nadu by CMT

The highest prevalence (100%) of subclinical mastitis (at cow level) was observed in 75 % cross bred Holstein Friesian,(HF) 36.3, 22 and 7% of CMT positive cases were recorded in 62.5% HF cross bred,50% Holstein Friesian and Jersey cross bred respectively (Table 2). Analysis of association logistic regression model showed that parity, left fore (LF), left hind (LH) and right hind (RH) quarters had significant influence on the prevalence of subclinical mastitis both at the cow and quarter level. Prevalence of subclinical mastitis was shown to increase lactation stage (late lactation) showing a higher prevalence (80.9%) than mid lactation which had 52.1%.

Cows in late lactation stage (>180 days) had a significant higher prevalence of subclinical mastitis (80.9% compared to cows in mid lactation (90-180 days) and early lactation stage (<90days) (Table 2). Pluriparous cows had a higher prevalence of SCM (69.3%) than primiparous cows. Right side quarter had higher sub clinical mastitis (42.8%) than left side quarter (33.7%). In the view of Pregnancy status, pregnant animal had higher prevalence rate (70.5%) than non pregnant animals (69.5%).

Table 2: Variables in the equation of risk factors in sub clinical mastitis

Table 3: Observed groups and predicted probabilities in sub clinical mastitis

Discussion

Mastitis is a major infectious disease affecting high yielding dairy cows causing a massive economic loss despite advanced research and innovative package of practices were taken in the past decades (Sakemi et al., 2011; Siddiquee et al., 2013).This cross sectional study revealed that overall prevalence of subclinical mastitis was 68.8 % in lactating cows in western zone of Tamil Nadu. The prevalence of subclinical mastitis in dairy cows of India varied from 15 to 75 %, whereas the involvement of quarters varied between 5 and 40 % (Cynthia, 2005). Five states, namely Punjab, Haryana, Uttar Pradesh, Madhya Pradesh, and Maharashtra had estimates of 53.52%, 51.18%, 39.58 %, 62.49 % and 35.11 % respectively. Meta-analysis of state-wise prevalence data showed that Punjab and Haryana had harmonized prevalence of subclinical mastitis on cow-basis (Banger et al., 2014). The variation in cow level prevalence probably may be due to differences in cow level factors (genetic makeup of crossbreds, parity, and stage of lactation), agroclimatic conditions, and farm managemental practices (Joshi and Gokhale, 2006). The results of showed high variation in quarter-level prevalence of subclinical mastitis (Banger et al., 2014), which may be due to differences in animal factors (udder position, teat-end shape, level of milk production) and herd level factors (type of floor, type of milking, and farm practices). De (2011) observed that low prevalence was due to effective farm practices like hygienic milking, teat dipping, dry cow therapy, good managemental practices, and prompt therapeutic measures.

In this study, Holstein Frisian with 75 % purity shows the highest prevalence of 100%. This study agrees with Alebachew and Alemu (2015) who reported breed had a significant influence on prevalence of mastitis. At the quarter level Jersey had the highest prevalence of SCM of 66.6 % which agrees with the finding by (Alebachew and Alemu 2015). In our study pregnancy status had no/less significance influence on the prevalence of subclinical mastitis. Pluriparous cows had a higher prevalence of SCM (69.3%) than primiparous cows. Under binary logistic regression model showed that pairty had significant influence on subclinical mastitis at 0.05% leve. Several studies agreed with the present findings of higher prevalence of subclinical mastitis with the advancing parity (Rahman et al., 2009, Mekibib et al., 2010 and Abrahmsén et al., 2014). The prevalence of SCM at quarter level was significantly higher in multiparous animal as compared to primiparous animals. This could be explained that the teat canal in older animals is more dilated and or it remains partially open permanently due to years of repeated milking (Madut et al., 2009). In terms of parity, the prevalence of SCM was significantly (p<0.005) higher in cows of above second parity in comparison to first parity (Table 2). This observation supports with the reports of Joshi and Gokhale (2006), Byarugaba et al. (2008) and Rabbani and Samad (2010). The increase in the number of parity is associated with the corresponding increase in the prevalence of SCM (Sudhan et al., 2005, Islam et al., 2010). The higher prevalence of SCM in cows with the parity may be explained by the fact that disease resistance of cows might have lower with progression of parity (Byarugaba et al., 2008). This association was significant at animal level also. This study also witnessed that right side quarter had higher degree of subclinical Mastitis than left side. The reason behind this might be due to uneasiness of milking of right side udder.

In our study lactation stage had an influence on prevalence of mastitis with > 180 days having the highest prevalence of 80.9%. These animals were at declining milk production stage. This may be due to continuous damage of the secretary mammary tissues and poor or low udder immunity because of unmatched feeding pattern at this stage.

Conclusions

• There was a high prevalence of subclinical mastitis in smallholder dairy farms in north western zone of Tamil Nadu.
• The findings suggest that higher the age group more will be the prevalence of mastitis.
• At cow level Holstein Frisian with 75% purity and at quarter level Jersey cross ranks first in the prevalence of mastitis.
• Right side quarter had higher rate of mastitis than left side quarter.

Acknowledgement

The authors are grateful to the dairy farmers for approving to take part in this study.

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