BackgroundExacerbated postparturient insulin resistance (IR) has been associated with several pathologic conditions in dairy cattle. Oxidative stress (OS) plays a causative role in IR in humans, and an association, but not direct relationship, between OS and IR recently has been reported in transition dairy cattle.HypothesisSupplementation with antioxidants shortly before calving improves glucose tolerance after parturition in dairy cattle.AnimalsTen late‐pregnant Holstein cows entering their 2nd to 5th lactation.MethodsRandomized placebo‐controlled trial: 15 ± 2 days before expected calving, the treatment group received an injection of DL‐alpha‐tocopheryl acetate at a dosage of 6 mg/kg body weight (BW) and 0.06 mg/kg BW of sodium selenite, and the control group was injected with isotonic saline. During the first week after calving, both groups underwent glucose tolerance testing (0.25 g glucose/kg BW). Commercial assays were used to quantify the concentrations of glucose, insulin, nonesterified fatty acids (NEFA), beta‐hydroxybutyrate, and markers of redox status in blood. Data were analyzed using the Mann–Whitney U‐test (α = 0.05).ResultsSupplemented cows showed a lower risk for OS, as reflected by a lower OS index (P = .036), different areas under the curve for the concentrations of glucose (P < .01), insulin (P = .043), and NEFA (P = .041), more rapid elimination rates (P = .080, <.01 and .047 respectively), and shorter half‐lives (P = .040, <.01 and .032) of these metabolites.Conclusions and Clinical ImportanceSupplementation with antioxidants before calving resulted in greater insulin sensitivity after calving, thereby suggesting the role of OS in the development of IR in cattle and the potential benefits of antioxidant supplementation in minimizing the consequences of negative energy balance.

In ambulatory practice, there has traditionally been limited access to quick ancillary tests to aid the diagnostic process. However, over the past decades, diagnostic technologies have improved substantially, producing several accurate and cost-effective tests that can be used on-farm to establish a better diagnosis, a quick and informed therapeutic plan and help to determine the prognosis. Examples of these tests include the glutaraldehyde test for estimating the inflammatory response, tests to measure several metabolites (eg, glucose, ketone bodies, L-lactate) cow-side, or tests to identify different pathogens. This article aims to review the accuracy and practical applications of some of the different animal-side tests that are available to cattle veterinarians in an ambulatory setting, providing diagnostic tools that can be used in the field, without having to submit a sample to a laboratory, thereby expediting the clinical decision.

There has been some recent criticism about the reliability of the assays commonly used to measure oxidant status in cattle, because some recent publications suggested that the concentration of different trace elements influences the results of these assays. The aim of this study was to test the correlation in 502 bovine serum samples between the concentration of several trace elements (Br, Co, Cr, Cu, Fe, I, Mn, Mo, Ni, Se, Sr, V and Zn) and markers of oxidant status (reactive oxygen species (ROS) and total serum antioxidant capacity (SAC)). The Oxidative Stress index (OSi) was also calculated as ROS/SAC. Some significant correlations were found, although weak (|ρ| < 0.50). Therefore, the relationships observed might be attributed to the different pro- and antioxidant effect of the different elements rather than to the assays detecting these elements instead of the oxidised molecules or total antioxidant potential, respectively. The OSi was poorly correlated (|ρ| ≤ 0.36) with the concentration of the studied trace elements, and therefore, its use is recommended to assess shifts in the systemic redox balance.