Ultrasound evaluation of mammary gland cistern in Holstein-Friesian cows affected by clinical mastitis

The objective of this study is to assess ultrasound mammary gland evaluation as a reliable on field diagnostic tool for mastitis in dairy cows.This study was carried out within Agritech National Research Center. During a period of 10 months, 356 mammary quarters of 89 primiparous and multiparous Holstein Friesian dairy cows from a single farm were evaluated. Animals treated in the same lactation with antibiotic, or presenting other diseases differing from mastitis were excluded. Animal care and procedures were in accordance with the European directive 2010/63/EU and the national law D.L.2014/26. During this study, sterile milk pool samples were examined for antimicrobial analysis and somatic cell count(SCC); clinical examination of all animals was performed. Based on the results, animals were divided into 3 groups: “healthy”(11), having negative microbial analysis and SCC< 100.000 cells/ml; “subclinical”(55), having at least either positive microbial culture or SCC>100.000 cells/ml; “clinical”(23), having positive microbiological culture and clinical signs of mastitis. After 6 hours from milking, B-mode mammary ultrasound evaluation was performed. Based on the echogenic aspect of the mammary cistern, a possible grading has been proposed. 0 anechoic, 1 little echogenic spots, 2 massive echogenic spots, 3 widely echogenic. Statistical analysis was performed through R software. Shapiro Wilk test showed non-normal distribution of data. Chi-squared test, Kruskal-Wallis test and Spearmanʼs correlation test have been performed. P-value<0,05 was considered significant.From microbiological culture, the majority of animals were positive to coagulase-negative staphylococci, Streptococcus uberis and Escherichia coli. From ultrasound images, 144 quarters were classified as 0, 143 as 1, 51 as 2 and 16 as 3. Considering the distribution of gradings within the 3 groups, Chi-squared test was performed, highlighting significant difference within groups. Subsequently, a media per animal of the 4 quartersʼ grading has been calculated. Kruskal-Wallis test confirmed a significant difference of the media between groups, with the highest value in clinical animals and the lowest in healthy subjects. Finally, Spearmanʼs correlation between SCC and grading media has been applied. The test showed a Spearman correlation of 0,59 and significant p-value.Ultrasonography of the normal udder parenchyma shows homogenous hypoechogenic parenchyma with interspersed anechoic blood vessel, milk alveoli and lactiferous duct. The gland cisterns appear instead as a large homogenous anechoic area. Several studies previously assessed ultrasonographic changes in parenchyma structure and possible gradings based on them has already been proposed[1,2]. Our study focused on the gland cistern instead. The statistical analysis highlighted a significantly higher echogenicity of gland cistern affected by clinical mastitis, in accordance with previous articles[3]. Moreover, a moderate direct correlation between echogenicity and SCC has been proved. The possibility to predict and evaluate the degree of damage during mastitis through ultrasound mammary gland evaluation, particularly of the gland cistern, could represents an important on-farm tool. Moreover, the establishment of an objective mammary ultrasound score, might provide useful directions not only in terms of animal health and welfare, but also for the evaluation of the most proper therapeutic protocol. [1]Suzuki et al. Outcome Prediction from the First Examination in Clinical Mastitis Using Ultrasonography in Dairy Cows. Anim. Sci. J. 91, 2020 [2]Flöck et al. Ultrasonography in Cattle with Diseases of the Mammary Gland. Vet. J. , 171, 2006 [3]Santos et al. B-Mode and Doppler Sonography of the Mammary Glands in Dairy Goats for Mastitis Diagnosis. Reprod. Dom. Anim. 50, 2015