The aim of this study was to determine changes of reactive oxygen species (ROS), serum antioxidant capacity (SAC), oxidative stress index (OSi), and α-tocopherol (α-T) during the periparturient period in healthy and mastitic cows and to further investigate whether these parameters can be used as a tool for identifying cows at higher risk of developing mastitis. Blood samples from 110 dairy cows from two commercial farms were obtained at dry-off, calving, and 30 days post-partum. Healthy cows formed group A (n = 90) and mastitic cows B (n = 20). Blood serum was obtained by centrifugation, and the aforementioned parameters were determined. A general linear model was used for analysing the associations among the determined blood parameters, the health of the animals’ udder, and the sampling time. ROS and OSi values were higher (P < 0.001) by a respective 14% and 26%, and SAC values lower (P < 0.001) by 10% in group B than in group A at calving. ROC curve analysis revealed that all determined parameters at calving and α-T at dry-off and 30 days post-partum had excellent or acceptable predicting ability for mastitis incidence. This information provides a tool for early identification of cows at high risk of developing mastitis, allowing the implementation of intervention strategies.

Objective: The current investigation was designed to point out the prevalence of multidrug-resis¬tant Streptococcus spp. causing acute clinical mastitis and their pattern of antibiotic resistance in dairy cows. Materials and methods: Milk was sampled from 128 dairy cows with 191 infected quarters during the period from August 2017 to December 2018. Bacterial species were isolated from the milk samples and identified based on colony morphology and biochemical tests. Multiplex PCR was done for confirmatory detection of the Streptococcus spp. isolates. Results: The chief isolation percentages, from the sampled milk, were Escherichia coli (26%), then Staphylococcus aureus (23%), and Streptococcus dysagalactiae (23%), then Streptococcus agalac¬tiae (20.1%), and finally coagulase-negative Staphylococci (7.7%). In confirmed PCR streptococci isolates, the antibiotic resistance genes have been detected, including macrolides antibiotic resis¬tance genes (ermB and mefA genes), lincosamides antibiotic resistance genes (linB gene), and tetra¬cycline resistance genes (tetM and tetO genes). Age, parity number, cleaning of bedding materials, cleaning of milking facilities, and utensils and udder cleaning practice were significant risk factors for multidrug-resistant streptococcal mastitis in dairy cows. Conclusion: The results of this study explored the phenotypic and genotypic traits of Streptococcus spp. which constitute a usual cause of acute clinical mastitis in dairy cows. The ermB, mefA, tetM, and tetO antibiotic-resistant genes were identified in streptococci isolates from dairy cows milk with acute clinical mastitis, indicating a public health hazard. Thus, veterinary clinical breakpoints are needed to improve surveillance data, improve the hygiene regimen on the farms, and pro¬mote the wise use of antimicrobials. [J Adv Vet Anim Res 2020; 7(2.000): 186-197]

Objective: The influence of intramammary infection (IMI) and types of bacteria was assessed on somatic cell count (SCC) in dairy cows milk with respect to breed, age, parity, stage of lactation, milk production, and mammary quarter location. Materials and methods: After recording data in a structured questionnaire, 360 samples of quar¬ter milk were collected. The samples were subjected to SCC and isolation and identification of bacteria. The data were analyzed to find out the significant influence of independent factors on SCC and IMI. Results: The infected quarters had a significantly higher mean SCC (210.52 × 103 cells/ml) compared to uninfected ones (32.72 × 103 cells/ml). The mean SCC was the highest for IMI with Enterobacter spp. (338.00 × 103 cells/ml) followed by Bacillus spp. (319.20 × 103 cells/ml), coagulase-negative Staphylococci (CNS) (268.17 × 103 cells/ml), Staphylococcus aureus (218.31 × 103 cells/ ml), and Escherichia coli (200.75 × 103 cells/ml) and the lowest for Pseudomonas aeruginosa (66.33 × 103 cells/ml). Milk of rear quarters had a significantly higher SCC than the front quarters. SCC increased with increasing age, parity, and lactation stage regardless of whether cows are infected or not. The IMI was more prevalent in rear quarters (42.2%) and cows at early (&#8804;7 days) lactation (100.0%). Cows having a parity of &#8805;5 and crossbred and high yielding (>5 l) cows had also a higher rate of IMI of 38.2%, 36.7%, and 38.2%, respectively. Conclusion: The IMI and type of bacteria were the principal factors for SCC variation. Besides, mammary quarter location, age, and parity should be taken into consideration during the inter¬pretation of SCC. [J Adv Vet Anim Res 2020; 7(2.000): 314-319]

The objective of this study was to evaluate the association between ketonemia and serum paraoxonase-1 (PON1), malondialdehyde (MDA), and other blood components in tail and mammary veins of dairy cows. Forty-two Holstein dairy cows with decreased feed intake were divided into HIGH (≥ 1.2 mM; n = 31) and LOW (< 1.2 mM; n = 11) groups based on the β-hydroxybutyrate concentration in plasma collected from the tail vein. The HIGH group had a significantly greater plasma non-esterified fatty acid (NEFA) concentration, but significantly lower serum PON1 activity and phospholipid concentration, and a tendency to have a lower cholesterol ester concentration than the LOW group. Serum PON1 activity was not correlated with the MDA concentration but was positively correlated with serum concentrations of cholesterol esters and phospholipids, and negatively correlated with the plasma NEFA concentration. These results suggest that serum PON1 activity is reduced by hyperketonemia and the relevance of PON1 to MDA seems to not be direct, though it is involved.

This study was planned to assess the possible relationships with pregnancy-associated glycoproteins (PAG) concentrations by the determination of the biomarkers of oxidative stress in the plasma of dairy cattle during the early period of gestation. Materials and Methods: Blood samples were collected from coccygeal vessels in pregnant (n = 54) and nonpregnant (n = 45) cows. Measurement of biomarkers of oxidative stress (LPO, GSH and SOD) was carried out in females using spectrophotometric method.Plasma PAG concentrations increased and continuously over the both periods investigated. There were significant differences between pregnant and non-pregnant groups (P < 0.001). The concentration of SOD were significantly lower (P< 0.05) in pregnant females from day 25 to 35 (7.08 ±0.31 U.ml-1) and day 36 to 50 after AI (6.6 ± 0.29 U.ml-1) compared with non-pregnant cows (7.59 ± 0.35 U.ml-1). Concerning the concentrations of LPO and GSH, the values obtained were also significant lower (P < 0.05) in pregnant females in the period 25-35 days post AI (122.7 ±10.27 μM and 6.46 ±1.24 μmol/min.ml-1, respectively) and 36-50 days post AI (108.05±6.17 μM and 6.2±0.77 μmol/min.ml-1, respectively) than in the non-pregnant females (124.8 ± 12.16 μM and 6.96 ± 0.92 μmol/min.ml-1, respectively).It was observed that the markers of oxidative stress tended to be higher in non-pregnant females compared with pregnant females during the early period of gestation in dairy cattle. Our results suggest the existence of a relationship among the concentration of oxidative stress markers and PAG during early pregnancy.