Field diagnostic of mastitis in dairy cows: application of udder ultrasound and blood gas analysis

Mastitis, the inflammation of the mammary gland, represents one of the main pathologies in dairy cattle farm. It leads to severe economic losses and drug administration, representing a relevant problem for animals, farmers, and public health. Diagnosis mainly consists in analysis on milk, such as microbial culture, PCR and somatic cell count. Considering the vitally importance of a fast and reliable diagnosis, the aim of this research is to evaluate ultrasound mammary examination and blood gas analysis as on-farm tools able to timely detect and characterize quarters affected by mastitis. For this purpose, a total of 83 Holstein-Friesian cows from a single farm in Veneto Region (Italy) have been enrolled. For each animal, clinical examination, ultrasound examination of the mammary gland, blood gas analysis and milk sampling of single quarter have been performed. For the first trial, 39 primiparous and multiparous dairy cattle have been divided into four groups based on symptoms, microbial culture and somatic cell count. Specifically, CTR” (control, having no clinical signs, negative microbial culture and SCC< 200.000 cells/ml), “IMI” (Intramammary infection, having no clinical signs, positive microbial culture and SCC <200.000 cells/ml), “SUB” (subclinical, having no clinical signs, positive microbial culture and SCC ≥200.000 cells/ml) and “CL” (clinical, having clinical signs, positive microbial culture and SCC ≥200.000 cells/ml). An ultrasound classification of the echogenicity of the content of the mammary gland cistern has been proposed from 0 (completely anechoic cistern), to 3 (completely echogenic cistern). For the second trial 83 Holstein-Friesian cows have been divided into three groups: healthy controls (CTR), cows positive to CNS with low somatic cell counts (CNS_LOW), animals positive to CNS with high counts (CNS_HIGH). Blood gas and biochemical parameters were assessed at diagnosis (T0) and seven days later (T1). Results show significant differences between groups of SCC and ultrasound score (US). Moreover, SCC values were significantly different also considering US. Significant differences were also observed among groups for parameters including pH, pCO₂, HCO₃⁻, base excess, K⁺, lactate, BUN, urea, and creatinine. Notably, CNS infections were associated with mild metabolic acidosis, altered renal biomarkers, and increased lactate levels, indicating systemic involvement even in subclinical cases. Even though further studies are needed in order to validate and deepen these techniques, results suggest a possible application of ultrasound examination and blood gas analysis as valuable field diagnostic tools for monitoring systemic effects of mild clinical mastitis, supporting targeted therapeutic strategies and improving detection of mastitis.