A Pilot Study to Compare Oxidative Status between Organically and Conventionally Managed Dairy Cattle During the Transition Period

Evaluation of a portable fluorometer for the quantification of vitamin E in blood at key physiological stages of dairy cattle

Vitamin E is essential in mitigating the impact of oxidative stress on periparturient dairy cows and neonatal calves. Therefore, it is essential to measure circulating vitamin E concentrations accurately. Currently, the only reliable method is an expensive and time-consuming procedure using liquid chromatography-mass spectrometry (LC-MS). However, a cheaper and faster method has been developed, which allows the quantification of circulating vitamin E through the use of a handheld fluorometric analyzer (HFA) called the vitamin E iCheck (BioAnalyt GmbH). Our objective was to compare the accuracy of the HFA to the reference LC-MS method for measuring vitamin E in bovine samples. A total of 177 samples collected for other studies were used: 98 newborn calf serum samples from a vitamin E supplementation study (including treated and control animals) and 79 whole-blood samples from cows 1 to 7 d postcalving. Vitamin E concentrations were measured on thawed calf serum and fresh cow EDTA blood using the HFA, following the manufacturer's instructions. Whole blood from cows was then centrifuged to obtain plasma. Vitamin E was also quantified in calf serum and cow plasma at the Michigan State University Veterinary Diagnostic Laboratory using LC-MS. Calf and cow results were analyzed separately because they represent different biological matrices and physiological times. In each dataset, results between the HFA and LC-MS determinations were compared using Passing-Bablok regressions and Bland-Altman plots. The HFA showed a poor linear relationship with LC-MS for calf serum and cow plasma (intercept = 0.33 and 0.67 μg/mL, respectively). The HFA unreliably estimated vitamin E, with a mean bias of -3.2 and 0.6 μg/mL for calves (vitamin E concentration range: 0.28 to 30.75 μg/mL) and cows (0.8 to 5.88 μg/mL), respectively. Moreover, 40.4% of the calf samples read below the linear range of acceptable results for the HFA, making it unsuitable for this age group. Hence, under the conditions of our study, the HFA yielded unreliable results and cannot be recommended for field use.

Circulating and endometrial cell oxidative stress in dairy cows diagnosed with metritis

Dairy cows diagnosed with metritis may experience a greater degree of oxidative stress (OS) and a deficit in the antioxidative capacity compared to healthy cows. We aimed to assess circulating OS markers and endometrial cell mitochondrial function, intracellular reactive oxygen species (ROS) production, and mean endometrial nuclear cell area in postpartum cows diagnosed with metritis or as healthy. From an initial pool of 121 Holstein cows, we retrospectively selected 34 cows and balanced for metritis (n = 17) or healthy (n = 17). Metritis was defined as an enlarged uterus with red-brown watery or thick off-white purulent discharge occurring within 21 days postpartum. Cows with no signs of clinical disease (including dystocia or retained placenta) were referred to as healthy. Blood samples for serum reactive oxygen metabolites (d-ROM), antioxidants (OXY), and oxidative status index (OSI) tests, evaluated via photometric determination of plasma thiols, were performed at 7, 14, 21, 28, and 35 days postpartum. Furthermore, from the initial pool, a random subset of 5 cows diagnosed with metritis and 6 diagnosed as healthy we collected (at the same time points as for the blood samples) endometrial cytology samples using the cytobrush technique. From the uterine samples, we evaluated the endometrial cell mitochondrial function, intracellular ROS levels, and the endometrial cell nuclear area using MitoTracker Orange, dichlorodihydrofluorescein diacetate, and Hoechst 33258, respectively. Mixed linear regression models, accounting for repeated measurements, were fitted to assess the effect of metritis versus healthy on circulating and endometrial cell OS parameters and endometrial cell size. The effect of days postpartum and its interaction with uterine health status were forced into each model. Serum concentrations of d-ROMs and OSI were greater in metritis at 7, 14, and 35 days postpartum than in healthy cows. Interestingly, the mean endometrial cell nuclear area was lower in metritis than healthy cows at 14 and 21 days postpartum. We found no differences between metritis and healthy for endometrial cell mitochondrial function and intracellular ROS production. In conclusion, cows diagnosed with metritis experienced greater systemic OS levels than healthy cows, but their OS was not higher in the uterine milieu.

Nrf2 Activation and NF-Kb & caspase/bax signaling inhibition by sodium butyrate alleviates LPS-induced cell injury in bovine mammary epithelial cells

Mastitis, an inflammation of the mammary gland, is a complex disease that affects the health of dairy cows worldwide. Sodium butyrate (SB) is a short-chain fatty acid that has recently been shown to have antioxidant, anti-inflammatory and anti-apoptotic potential in various cells types, although its role in bovine mammary epithelial cells (bMECs) has not been comprehensively reported. Therefore, the aim of this study was to assess the protective effect of sodium butyrate on Lipopolysaccharide (LPS)-induced mastitis model in vitro and to elucidate the possible underlying molecular mechanisms. The in vitro mastitis model was designed to investigate the regulatory effect of SB on LPS-induced inflammatory conditions in bMECs, with particular emphasis on oxidative stress, inflammatory response, apoptosis, and mitochondrial dysfunction. The results showed that SB co-treatment markedly prevented LPS-induced death of bMECs in a concentration-dependent manner. In addition, SB attenuated LPS-induced oxidative stress (OS) (Increased Intracellular ROS, MDA, and decreased SOD, GSH-Px and CAT activity), thereby reduced inflammation (increased expression of IL-6, IL-Iβ, and TNF-α), and apoptosis (Increased the expression of caspases and Bax and decreased Bcl-2) via inhibiting NF-kB and caspase/bax signaling pathways. Furthermore, the protective effect of SB was also associated with the activation of endogenous antioxidant system (Nrf2, Keap1, NQO-1 and HO-1). Nrf2 silencing significantly abolished the protective effect of SB on bMECs. In conclusion, our findings suggest that SB has a significant protective effect on LPS-induced OS, inflammatory responses and apoptosis by activating Nrf2 and inhibiting NF-kB and ROS-mediated mitochondrial dysfunction. These results propose that SB may be an important regulator of OS and its subsequent inflammatory responses, and thus could be used as a therapeutic agent for bovine mastitis.

Transcription factor EB (TFEB)-mediated autophagy protects bovine mammary epithelial cells against H2O2-induced oxidative damage in vitro

Background

Bovine mammary epithelial cells after calving undergo serious metabolic challenges and oxidative stress both of which could compromise autophagy. Transcription factor EB (TFEB)-mediated autophagy is an important cytoprotective mechanism against oxidative stress. However, effects of TFEB-mediated autophagy on the oxidative stress of bovine mammary epithelial cells remain unknown. Therefore, the main aim of the study was to investigate the role of TFEB-mediated autophagy in bovine mammary epithelial cells experiencing oxidative stress.

Results

H₂O₂ challenge of the bovine mammary epithelial cell MAC-T increased protein abundance of LC3-II, increased number of autophagosomes and autolysosomes while decreased protein abundance of p62. Inhibition of autophagy via bafilomycin A1 aggravated H₂O₂-induced reactive oxygen species (ROS) accumulation and apoptosis in MAC-T cells. Furthermore, H₂O₂ treatment triggered the translocation of TFEB into the nucleus. Knockdown of TFEB by siRNA reversed the effect of H₂O₂ on protein abundance of LC3-II and p62 as well as the number of autophagosomes and autolysosomes. Overexpression of TFEB activated autophagy and attenuated H₂O₂-induced ROS accumulation. Furthermore, TFEB overexpression attenuated H₂O₂-induced apoptosis by downregulating the caspase apoptotic pathway.

Conclusions

Our results indicate that activation of TFEB mediated autophagy alleviates H₂O₂-induced oxidative damage by reducing ROS accumulation and inhibiting caspase-dependent apoptosis.

Symposium review: Late-gestation maternal factors affecting the health and development of dairy calves

Efficient production of heifers is fundamental to the productivity and sustainability of dairy farms. However, high preweaning morbidity and mortality rates are frequently reported worldwide, imposing substantial welfare and economic implications. A major contributing factor to disease susceptibility in the neonatal stage is the inability of calves to mount an effective immune response. Appreciation is now greater that exposure in utero to several stresses (nutritional, social, metabolic, and so on) during the last stages of pregnancy have downstream carryover effects in calves' health, growth, and development. Suboptimal intrauterine conditions during critical periods of development lead to changes in tissue structure and function that may have long-term consequences on the offspring's physiology and disease susceptibility. Indeed, preweaning metabolic function and growth are associated with future milk production. Thus, late-gestation carryover effects span into the lactating stage of the heifers. Nevertheless, researchers have been studying how to minimize these effects. This review will discuss the effects of maternal stress during late gestation on the offspring's growth, productivity, metabolism, and health. In addition, strategies focusing on maternal interventions that improve neonatal health will be discussed. A better understanding of the intrauterine conditions affecting calf health and growth may facilitate the design of management practices that could improve neonatal development and future cow productivity.

Short communication: Pro- and antioxidative indicators in serum of dairy cows during late pregnancy and early lactation: Testing the effects of parity, different dietary energy levels, and farm

Dairy cows face metabolic challenges in the transition from late pregnancy to early lactation. The energy demands for the growing fetus and the onset of milk production are increasing but voluntary feed intake often decreases around parturition and cannot meet these demands. This energy balance, among others, can change the oxidative status. Oxidative stress occurs when antioxidant defense mechanisms are not sufficient to cope with the increasing generation of reactive oxygen species. Our objectives were to investigate (1) the effect of parity on the oxidative status of dairy cows (n = 247) in late pregnancy and early lactation; and (2) the effect of different inclusion rates of concentrate feeding (150 vs. 250 g/kg of energy-corrected milk) during early lactation on 2 farms including 87 cows in total. In addition, we aimed to compare the oxidative status across the 2 farms using equal portions of concentrate feeding. For these purposes, we measured concentrations of the derivatives of reactive oxygen metabolites (dROM) and the ferric reducing ability (FRAP) in serum on d -50, -14, +8, +28, and +100 relative to calving. Furthermore, we calculated the oxidative status index (OSi) as dROM/FRAP × 100. Data were analyzed using a linear mixed model. Cows in the first and second lactations had greater dROM, FRAP, and OSi than cows in their third and greater lactations. Hence, supporting the antioxidative side of the balance might be of particular importance in the first and second lactations. Feeding different amounts of concentrates did not affect dROM, FRAP, or OSi under our experimental conditions, suggesting that the relatively small differences in energy intake were not affecting the oxidative status. Comparing farms, cows from one farm were notable for having greater dROM and lower FRAP, resulting in a greater OSi compared with cows on the other farm. Milk yield showed a time by farm interaction with 7% less milk on d 100 on the farm with the greater OSi. Moreover, cows on that farm had 1.4-fold greater β-hydroxybutyrate concentrations. Our results emphasize the value of assessing oxidative status with regard to both the pro- and antioxidative sides, and support the association between oxidative and metabolic status. Further investigations are needed to determine the applicability of OSi as a prognostic tool during early lactation and to determine which factors have the greatest influence on oxidative status.

A Review of Lignan Metabolism, Milk Enterolactone Concentration, and Antioxidant Status of Dairy Cows Fed Flaxseed

Lignans are polyphenolic compounds with a wide spectrum of biological functions including antioxidant, anti-inflammatory, and anticarcinogenic activities, therefore, there is an increasing interest in promoting the inclusion of lignan-rich foods in humans' diets. Flaxseed is the richest source of the lignan secoisolariciresinol diglucoside-a compound found in the outer fibrous-containing layers of flax. The rumen appears to be the major site for the conversion of secoisolariciresinol diglucoside to the enterolignans enterodiol and enterolactone, but only enterolactone has been detected in milk of dairy cows fed flaxseed products (whole seeds, hulls, meal). However, there is limited information regarding the ruminal microbiota species involved in the metabolism of secoisolariciresinol diglucoside. Likewise, little is known about how dietary manipulation such as varying the nonstructural carbohydrate profile of rations affects milk enterolactone in dairy cows. Our review covers the gastrointestinal tract metabolism of lignans in humans and animals and presents an in-depth assessment of research that have investigated the impacts of flaxseed products on milk enterolactone concentration and animal health. It also addresses the pharmacokinetics of enterolactone consumed through milk, which may have implications to ruminants and humans' health.

Nuclear factor erythroid 2-related factor 2 antioxidant response element pathways protect bovine mammary epithelial cells against H2O2-induced oxidative damage in vitro

The experiment was conducted to determine the role of nuclear factor (erythroid-derived 2)-like factor 2 (NFE2L2, formerly Nrf2) antioxidant response element (ARE) pathway in protecting bovine mammary epithelial cells (BMEC) against H₂O₂-induced oxidative stress injury. An NFE2L2 small interfering RNA (siRNA) interference or a pCMV6-XL5-NFE2L2 plasmid fragment was transfected to independently downregulate or upregulate expression of NFE2L2. Isolated BMEC in triplicate were exposed to H₂O₂ (600 μM) for 6 h to induce oxidative stress before transient transfection with scrambled siRNA, NFE2L2-siRNA, pCMV6-XL5, and pCMV6-XL5-NFE2L2. Cell proliferation, apoptosis and necrosis rates, antioxidant enzyme activities, reactive oxygen species (ROS) and malondialdehyde (MDA) production, protein and mRNA expression of NFE2L2 and downstream target genes, and fluorescence activity of ARE were measured. The results revealed that compared with the control, BMEC transfected with NFE2L2-siRNA3 had proliferation rates that were 9 or 65% lower without or with H₂O₂, respectively. These cells also had apoptosis and necrosis rates that were 27 and 3.5 times greater with H₂O₂ compared with the control group, respectively. In contrast, transfected pCMV6-XL5-NFE2L2 had proliferation rates that were 64.3% greater or 17% lower without or with H₂O₂ compared with the control group, respectively. Apoptosis rates were 1.8 times lower with H₂O₂ compared with the control. In addition, compared with the control, production of ROS and MDA and activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and glutathione-S-transferase (GST) increased markedly in cells transfected with pCMV6-XL5-NFE2L2 and without H₂O₂. However, compared with the control, production of ROS and MDA and activity of CAT and GSH-Px increased markedly, whereas activities of SOD and GST decreased in cells transfected with pCMV6-XL5-NFE2L2 and incubated with H₂O₂. Compared with the control, cells transfected with NFE2L2-siRNA3 with or without H₂O₂ had lower production of ROS and MDA and activity of SOD, CAT, GSH-Px, and GST. Cells transfected with pCMV6-XL5-NFE2L2 with or without H₂O₂ had markedly higher protein and mRNA expression of NFE2L2, heme oxygenase-1 (HMOX-1), NADH quinone oxidoreductase 1, glutamate cysteine ligase catalytic subunit, and glutamyl cystine ligase modulatory subunit compared with the control incubations. Cells transfected with NFE2L2-siRNA3 without or with H₂O₂ had markedly lower protein and mRNA expression of NFE2L2, HMOX-1, NADH quinone oxidoreductase 1, glutamyl cystine ligase modulatory subunit, and glutamate-cysteine ligase catalytic subunit compared with the control incubations. In addition, expression of HMOX-1 was 5.3-fold greater with H₂O₂ compared with the control. Overall, results indicate that NFE2L2 plays an important role in the NFE2L2-ARE pathway via the control of HMOX-1. The relevant mechanisms in vivo merit further study.

Association of Serum Concentration of Different Trace Elements with Biomarkers of Systemic Oxidant Status in Dairy Cattle

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.