Clinical mastitis in buffaloes: Bacterial etiology, antimicrobial susceptibility and associated milk loss in a hospital-based study

Introduction

Mastitis is an inflammatory disease of the mammary gland and is one of the major causes of economic loss in dairy production (Ibeagha-Awemu et al., 2025) [1] . Its consequences include reduction in milk production, changes in milk quality, treatment expenditure and removal of unproductive animals from the herd (Yadav et al., 2024a) [2] . The disease occurs in both clinical and subclinical forms; clinical mastitis is associated with visible abnormalities of milk or the udder, whereas subclinical mastitis may occur without obvious clinical changes (Fonseca et al., 2025) [3] . The etiological spectrum of bovine mastitis is broad. Frequently encountered bacterial agents include Staphylococcus aureus, Escherichia coli, Streptococcus spp., Klebsiella spp. and other bacterial organisms (Zhang et al., 2025) [4] . Recent literature also demonstrates that the relative contribution of mastitis-associated bacteria can vary between geographical areas and production systems, with environmental and opportunistic organisms contributing substantially in some dairy populations (Sizana et al., 2026) [5] . Antimicrobial treatment remains an important component of mastitis management; however, antimicrobial resistance complicates treatment and has implications for animal health, food production and public health (Askari et al., 2025) [6] . Studies of mastitis-associated bacteria have documented variable antimicrobial susceptibility profiles and the occurrence of multidrug-resistant isolates (Yadav et al., 2024a; Yadav et al., 2024b; Islam et al., 2025; Sizana et al., 2026) [7,5,2,8] . Consequently, area-specific antimicrobial susceptibility information is relevant to rational mastitis management. The economic consequences of mastitis extend beyond the immediate cost of treatment. Reduced milk yield, discarded milk, animal removal and other productivity losses can contribute substantially to the overall disease burden (Mumba et al., 2026) [9] . Fetrow et al. (2000) [10] similarly emphasized the economic impor tance of mastitis in dairy systems. This study specifically addressed this production component by evaluating milk loss per buffalo and the corresponding economic loss.

Although larger epidemiological studies have evaluated mastitis occurrence and antimicrobial susceptibility in Haryana and other regions, hospital-based information can provide a practical description of the organisms recovered from clinically affected animals and the associated production loss.

Objectives

• To study the hospital-based occurrence of mastitis in buffaloes over a period of three months.

• To determine the bacterial etiology of mastitis and antimicrobial susceptibility of the bacterial isolates.

• To evaluate milk loss per animal and the associated economic loss due to mastitis.

Materials and methods

Study design and source of data

The study was based on analysis of mastitis buffaloes reported at the Veterinary Clinical Complex, Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, Haryana, over a three-month period. Culture reports, antimicrobial susceptibility testing reports, and milk-loss information were used.

Bacterial etiology

Bacterial etiology was described from the culture reports available for mastitis-positive cases. It includes Streptococcus spp., Staphylococcus spp., E. coli, other bacteria and Klebsiella spp. Mixed infections (defined as the presence of more than one bacterium), were reported from most positive milk samples.

Antimicrobial susceptibility

Antimicrobial susceptibility was taken from cases and culture reports reported clinics by farmers. The antibiotics displayed were enrofloxacin, moxifloxacin, gentamicin, cefoperazone, cefoquinome, ceftriaxone, chloramphenicol, amoxicillin, amikacin and streptomycin.

Assessment of milk loss and economic loss

Milk yield before mastitis, milk yield after mastitis and milk loss per animal were presented using a box-and-whisker plot. There were milk-loss range of 1-10 kg/animal/day, an average loss of 6 kg/animal/day and an estimated economic loss of ₹360/animal/day.

Results

The study showed the highest occurrence of mastitis in buffaloes of fourth or higher parity (41%), followed by buffaloes in the second and third lactations (32%) and first lactation (27%). The study therefore identified higher parity as the category with the greatest reported occurrence within the hospital-based dataset. Among the antibiotics the highest antimicrobial susceptibility value was for enrofloxacin (35.60%), followed by cefoperazone (31.70%) and gentamicin and ceftriaxone (25.70% each). The lowest value shown was for streptomycin (9%). These values are presented exactly as reported and are not interpreted as resistance percentages. Mastitis was associated with a marked reduction in milk production. The reported milk yield decreased from 13.23 kg/animal/day before mastitis to 7.06 kg/animal/day after mastitis, corresponding to a milk loss of 6.16 kg/animal/day. The reported milk-loss range was 1-10 kg/animal/day, with an average loss of 6 kg/animal/day. The estimated economic loss associated with reduced milk production was ₹360 per animal per day.

Milk loss and economic loss

Discussion

Pattern of mastitis in relation to parity

The present hospital-based study showed the highest reported occurrence of mastitis in buffaloes of fourth or higher parity (41%). This finding is consistent with the general epidemiological importance of animal age or lactation history in mastitis occurrence. In a separate buffalo study from Haryana, Yadav et al. (2024b) [8] reported a significant effect of age on mastitis prevalence and noted the highest occurrence in the old-age group, followed by young and middle age groups. The same study also reported an association between lactation stage and mastitis occurrence. The agreement between the two studies supports the relevance of parity or age-related differences when describing mastitis in buffaloes, although the categories and study designs were not identical.

Bacterial profile

The predominance of Staphylococcus spp. and Streptococcus spp. in the present study is compatible with published observations that Gram-positive bacteria, particularly staphylococci and streptococci, are important mastitis pathogens. Yadav et al. (2024b) [8] , studying buffalo milk in Haryana, reported Gram-positive bacteria in 54.16% of culture-positive samples and identified Staphylococcus spp. and Streptococcus spp. among the important isolates. The same study described E. coli and Klebsiella spp. among Gram-negative organisms. Similarly, Yadav et al. (2024a) [2] reported substantial contributions of both Gram-positive and Gram-negative bacteria among mastitispositive samples from different districts of Haryana. The dominance of staphylococci in the present study also has relevance to contemporary mastitis literature. Islam et al. (2025) [7] described S. aureus as an important bovine mastitis pathogen and highlighted the role of antimicrobial resistance and virulence-associated characteristics in persistent intramammary infection. However, the present study did not contain molecular characterization or virulencegene data; therefore, no such conclusions are drawn. The observation of mixed infections in most positive milk samples is also important when interpreting the bacterial findings. Mixed bacterial involvement means that the clinical and therapeutic context cannot necessarily be reduced to a single organism.

Antimicrobial susceptibility

The Antimicrobial susceptibility study showed the highest reported susceptibility for enrofloxacin (35.60%), with lower values for the other antibiotics displayed. This pattern differs from the results of the broader buffalo study of Yadav et al. (2024b) [8] , in which chloramphenicol was reported as the most sensitive antibiotic overall, followed by enrofloxacin, amikacin, levofloxacin, moxifloxacin and gentamicin. The difference illustrates the importance of local and study-specific antimicrobial susceptibility data rather than assuming a uniform susceptibility profile across buffalo populations. Yadav et al. (2024a) [2] similarly reported variation in susceptibility across Haryana and identified gentamicin as the most sensitive antibiotic in that study, while penicillin showed high resistance. Recent studies further emphasize the variability of antimicrobial resistance among mastitis pathogens. Islam et al. (2025) [7] reported substantial resistance among S. aureus isolates and identified multidrug-resistant isolates as well as the mecA gene in a subset of isolates. Sizana et al. (2026) [5] also reported antimicrobial resistance among mastitis-associated bacteria and emphasized the need for improved hygiene and antimicrobial stewardship. The present study, however, provides susceptibility percentages rather than a molecular resistance profile; consequently, the findings should be interpreted as an antibiogram description rather than evidence of specific resistance genes or mechanisms.

Milk production loss and economic implications

The production-loss component is a major strength of the study because it connects mastitis with a directly relevant farm-output measure. The study reported milk loss of 1-10 kg per animal per day, an average loss of 6 kg per animal per day and an estimated economic loss of ₹360 per animal per day. This is consistent with the broader literature describing reduced milk yield as a major pathway through which mastitis generates economic loss. Yadav et al. (2024a) [2] identified decreased milk production and treatment costs as major economic consequences of mastitis, while Mumba et al. (2026) [9] demonstrated that mastitis-related economic burden can involve both direct health expenditures and indirect productivity losses such as discarded milk and animal removal. The milk-loss findings also have practical relevance in a hospital setting because animals presented for clinical disease may have already experienced a substantial decline in productive performance. Fetrow et al. (2000) [10] emphasized the economic dimension of mastitis management, supporting the inclusion of production loss when con-sidering the importance of the disease. In the present study, the reported ₹360 per animal per day loss provides a simple productionbased economic indicator from the hospital dataset; no additional cost components were estimated because they were not provided in the study.

Relationship between the present findings and published literature

Taken together, the study data and the published studies showed 3 main common findings: mastitis affects productive performance; bacterial etiology is heterogeneous but commonly includes staphylococci, streptococci and enteric Gram-negative organisms; and antimicrobial susceptibility varies among bacterial populations and geographical settings. The present hospital-based study adds a specific clinical perspective by combining bacterial findings, an antibiogram and quantified milk loss in buffaloes.

Conclusion

Bovine clinical mastitis in the hospital-based buffalo study was associated with a higher reported occurrence in animals of fourth or higher parity, predominance of Staphylococcus spp. and Streptococcus spp., frequent mixed bacterial involvement, variable antimicrobial susceptibility and substantial milk production loss. The study reported an average milk loss of 6 kg per animal per day and an economic loss of ₹360 per animal per day. The findings support the clinical and economic importance of mastitis in buffaloes and the value of combining bacteriological investigation, antimicrobial susceptibility testing and production-loss assessment.

References

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