ABSTRACT The objective of the present study was to evaluate the qPCR for detection and enumeration of Staphylococcus aureus and Streptococcus agalactiae using different milk samplings in comparison to the conventional microbiology. Four dairy herds with a history of subclinical mastitis caused by S. aureus and S. agalactiae were selected. Sampling approach included milk samples from bulk tank (BT), cow level (composite samples, CO), and mammary quarter level (MQ) from 785 lactating cows. Three consecutive monthly milk samplings were carried out, totaling 3347 MQ milk samples, 912 CO, and 12 from BT. All collected milk samples were subjected to conventional microbiology and qPCR for detection and enumeration of S. aureus and S. agalactiae. The qPCR showed 71.5% of diagnostic sensitivity for S. aureus isolated from MQ milk samples, 71.8% for CO, and 50% for BT milk samples compared with conventional microbiology methodology. Taken together, the diagnostic sensitivity for S. agalactiae isolated from MQ milk samples was 90.2, 87.7 for CO, and 90.9% for BT milk samples. In general, the qPCR methodology enabled the detection of S. aureus and S. agalactiae, regardless of the type of milk sampling. The direct use of milk samples to estimate the counting of S. aureus by qPCR demonstrated lower sensitivity than the counting of S. agalactiae, which can be explained by the pathogen infection dynamics and differences in milk sample type.

ABSTRACT We evaluated the inclusion of two crude extracts produced by Streptomyces genus on in vitro dry matter and organic matter digestibility (IVDMD; IVOMD), cumulative gas production, volatile fatty acids (VFA), and methane (CH4) and ammoniacal nitrogen (NH3-N) concentration. The experimental design was randomized blocks with three blocks and four treatments: AMC (1.2 mg/25 mL ruminal inoculum), Caat (1.2 mg/25 mL ruminal inoculum), negative control (no inclusion of extracts), and positive control (sodium monensin, 1.7 mg/25 mL ruminal inoculum). Ruminal fluid samples were collected from three multiparous Holstein dairy cows fitted with ruminal cannula and incubated in a 24-h fermentation assay. There was no effect of crude extract inclusion in comparison with negative control on cumulative gas production in 24 h. However, cumulative gas production was lower when Caat extract was included in comparison with AMC inclusion. The Caat inclusion increased propionic acid concentration and reduced the concentration of butyric acid and acetate:propionate (A:P) ratio in relation to negative control. The CH4 concentration was lower with Caat inclusion in relation to AMC, and the ratio of CH4 concentration to digestible dry matter was lower in the negative control compared with all additives. Caat inclusion decreased the NH3-N concentration, and IVDMD was not altered compared with negative control. Additionally, the inclusion of Caat crude extract increased propionic acid concentration and reduced butyric acid concentration and A:P ratio, without reducing the IVDMD and IVOMD. Caat extract modulates rumen fermentation, increasing available energy and decreasing gas production without causing changes in dry matter and organic matter digestibility.