Complementary use of N-acetyl-β-D-glucosaminidase and somatic cell count for detecting experimental and naturally occurring mastitis in dairy goats

<title>Abstract</title> <p> Mastitis is an inflammatory condition of the mammary gland that can lead to several changes, including significant alterations in glandular enzymatic activity, depending on the causative pathogen. <italic>Staphylococcus</italic> is frequently associated with intramammary mastitis in goats, with coagulase-negative <italic>Staphylococcus</italic> being the most prevalent group of pathogens responsible for subclinical mastitis in production animals. The diagnosis of mastitis in goats often relies on standardized tests designed for cattle, primarily the somatic cell count (SCC) test; however, the application of these techniques in goats is limited due to their biological differences. This study aimed to investigate the performance of the enzyme N-acetyl-β-D-glucosaminidase (NAGase) in 112 milk samples from animals experimentally infected with <italic>S. warneri</italic> , a coagulase-negative <italic>Staphylococcus</italic> species. Additionally, 49 milk samples from naturally infected animals at various stages of mastitis were analyzed. The NAGase activity was assessed using the fluorometric method. At the same time, SCC and Total Bacterial Count were determined using flow cytometry, with these tests serving as parameters for monitoring mastitis progression and infection. The results indicated that NAGase activity was significantly elevated in the milk of goats experimentally infected with <italic>S. warneri</italic> , with the enzyme reaching its peak two days after inoculation. The combined interpretation of NAGase and SCC improved differentiation between healthy and mastitic animals in naturally infected goats. In conclusion, this study demonstrates that NAGase activity can serve as an indicator of mastitis in goats, even in the early stages of infection, suggesting its potential utility as an adjunct biomarker for monitoring caprine mastitis when interpreted together with SCC. </p>