This study aims to evaluate the oxidative stress during hot summer season using serum oxidative stress biomarkers and elucidate the effects of serum antioxidant vitamin levels in dairy and beef cows in a daytime grazing system. Blood samples were collected once a month from eight Holstein Friesian (HF) and 10 Japanese Black (JB) cows from November 2013 to October 2014. Serum values of derivatives of reactive oxygen metabolites (d-ROMs) tended to be higher in March in both breeds and those in HF cows were kept at higher (P<0.001) levels than those in JB cows during the study period. Serum levels of biological antioxidant potential (BAP) in both breeds were maintained at almost the same values during study period. The OSI [(d-ROMs/BAP) × 100] values in both breeds showed similar seasonal changes, i. e. increase from December to March and decrease from March to August or September. In addition, the OSI values in HF cows were kept at higher (P<0.01) levels than those in JB cows during the study period. Serum concentrations of α-tocopherol, β-carotene, blood urea nitrogen and total cholesterol showed similar seasonal changes in both breeds, low in the winter and high from spring to summer, which may be attributed to the pasture grass intake. Opposite changes in OSI values and serum concentrations of α-tocopherol and β-carotene indicated that antioxidant vitamin levels could affect oxidative stress status.

This study aimed to evaluate the effects of live yeast (Saccharomyces cerevisiae) (LY) supplementation on serum oxidative stress biomarkers, antioxidant vitamin levels, and lactation performance in dairy cows during summer. A total of 16 lactating cows weighing 707.5 ± 13.1 kg (mean ± standard error) were enrolled and randomly assigned to either supplemented (n = 8) or control group (n = 8). In the supplemented group, the cows were administered with LY product at 10 g/day per cow from mid-July to mid-September for 8 weeks. The serum levels of derivatives of reactive oxygen metabolites in the supplemented group were lower (P < 0.05) at week 6. The serum retinol and blood glucose concentrations in the supplemented group were higher (P < 0.01) at week 8. LY supplementation did not affect physiological responses, such as rectal temperature, respiratory rate, protein and cholesterol metabolism, and lactation performance. During the study period, daily average milk yield decreased in both groups. The reduction rates of milk yield in the supplemented and control groups were 17.6 and 20.0%, respectively. These results suggest that LY supplementation may reduce oxidative stress and improve carbohydrate metabolism in lactating dairy cows during summer.

Background: Subacute ruminal acidosis (SARA) is one of the most important metabolic disease of dairy cattle which decrease milk production, dry matter intake, productivity and increase culling rate and even cause death.Methods: In this study the epidemiological status of SARA namely age, breed, stage of lactation, lactation number, general health condition, body condition score, daily milk production, milk fat content and biochemical alteration were investigated.Result: Out of 100 cows examined 20 were found to be positive for SARA and the mean age of dairy cows suffering from SARA was found to be 6.53 ±0.68 years. The prevalence of SARA was 70 and 30 per cent in Jersey and HF breed of cows respectively and was high in mid lactation and the lactation number ranged from 2 to 6. 65 per cent. SARA affected cows were in poor body condition score, milk production and milk fat content was significantly low (P≤ 0.05). The mean GGT (Gamma Glutamyl Transferase) and AST (Asparate aminotransferase) values were significantly increased in SARA affected dairy cows. SARA seems to be a common problem in dairy cattle and it has to be considered when dealing with herd level problems like low milk fat, low milk production, poor body condition and appropriate management measures should be implemented to prevent it.