Oxidative status during late pregnancy and early lactation in dairy cows

Reproductive stage associated changes in plasma fatty acid profile and proinflammatory cytokine expression in rat mammary glands

Mastitis is a common disease for mammals all around the world. Figuring out why mastitis mainly occurs around parturition may be helpful for dealing with the disease. Lipolytic activity and oxidative stress take place around parturition, which may leads to alteration in fatty acids profile and proinflammatory cytokine expression. Thus, the aim of the present study was to further our understanding about the high incidence of mastitis around parturition by comparison of plasma fatty acid profile and mammary inflammation indicators at different reproductive stages. A total of 47 female rats were included in the present study. After mating, all the pregnant and non-pregnant rats began to receive the same experimental diet. Blood samples were collected at day 1 and 14 of gestation as well as day 3 postpartum. Mammary samples were collected at day 14 of gestation and day 3 postpartum from pregnant and non-pregnant rats. The results showed that rats at d 3 postpartum had greater (P < 0.05) plasma concentrations of non-esterified fatty acids (NEFA), arachidonic acid (ARA) and docosahexaenoic acid (DHA) as well as ARA: eicosapentaenoic acid (EPA) ratio than those at d 14 of gestation. The mRNA abundances of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-8 and xanthine oxidoreductase (XOR) in mammary of the pregnant rats were greater (P < 0.05) than those in age-matched non-pregnant rats. Rats at d 3 postpartum had higher (P < 0.05) protein expression levels of IL-1β and TNF-α as well as meloperoxidase (MPO) activity and polymorphonuclear neutrophils (PMN) prevalence than those at d 1 of gestation. The rats at d 3 postpartum also had greater (P < 0.05) IL-1β and MPO activity than those at d 14 of gestation. The results indicated that elevated mammary expression of proinflammatory cytokines and XOR as well as altered fatty acid profile around parturition might facilitate the recruitment of neutrophils into mammary glands.

Selenium and Antioxidant Status in Dairy Cows at Different Stages of Lactation

Thirty-five multiparous Holstein cows averaging 550 ± 50 kg of body weight and in 2 to 4 parity were divided into three groups according to lactation stage (group A: nine cows from 4 to 1 weeks prepartum; group B: 11 cows from 1 to 30 days postpartum; group C: 15 cows from 30 to 100 days postpartum). Selenium concentration, malondialdehyde (MDA) level, glutathione peroxidase (GSH-Px) activity, thioredoxin reductase (TrxR) activity, and total antioxidant status (TAS) in serum were determined to evaluate selenium and antioxidant status in dairy cows at different stages of lactation. The results showed that mean serum selenium concentration, MDA level, and GSH-Px activity of cows in early lactation increased significantly (P < 0.05) when compared with cows in the dry period and peak lactation. Conversely, serum TrxR activity and TAS declined during this period (P < 0.05). The increase of serum MDA level during early lactation indicate that the reactive oxygen species, including lipid hydroperoxides, increase in this period, thus placing the cows at a greater risk of oxidative stress. The significant decrease in TrxR activity that is accompanied with a decrease in TAS during early lactation suggests that dairy cows have low antioxidant defense in this period and TrxR may be an important antioxidant defense mechanism in transition dairy cows.

Evaluation of serum markers of blood redox homeostasis and inflammation in PCB naturally contaminated heifers undergoing decontamination

Dioxins and polychlorinated biphenyls (PCBs) are widely spread and long persistent contaminants. The aim of this study was to evaluate physiological changes associated with the decontamination of animals previously exposed to environmental pollutants. Eight Limousine heifers were removed from a polluted area and fed a standard ration for six months. The extent of contamination was defined by measuring total toxic equivalents (TEQ) values of dioxin like-PCBs (DL-PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs), and NDL-PCBs amount in pericaudal fat two weeks after the removal from the contaminated area (day 0) and then bimonthly for six months during the decontamination (days 59, 125, and 188). The concentrations of both DL-PCBs + PCDD/Fs and NDL-PCBs at the start of decontamination (day 0) were higher than those legally admitted, and they were strongly decreased at the end of the experimental period. Specific indices of blood redox homeostasis and inflammation were also measured at each time. Serum concentrations of Retinol, Tocopherol and Ascorbate, the total antioxidant capacity (TAC) and the activities of superoxide dismutase and glutathione peroxidase were lower at day 0 than after 59, 125 or 188 days of decontamination. Protein-bound carbonyls (PC), nitro-tyrosine (N-Tyr), and lipid hydroperoxides concentrations were higher at day 0 than during decontamination. In addition, TAC, PC and N-Tyr levels correlated with both DL-PCB and NDL-PCB concentrations only at day 0. Serum concentrations of TNF-alpha and Haptoglobin were higher in samples collected at day 0 than in those obtained during decontamination. As Haptoglobin and TNF-alpha levels correlated with both DL-PCB and NDL-PCB concentrations at day 0 and at day 59 (when these concentrations are still over legal limit), they might represent easily measurable parameters for assessing acute exposure to pollutants. Further both N-Tyr and TNF-alpha concentrations could be used as bio-monitoring markers of the decontamination procedure.

Accelerated pre-weaning growth rates in dairy calves: do antioxidants have a place?

Accelerated growth of dairy calves in the pre-weaning phase has been shown to increase productivity of dairy cows during their lifetime. The increased weight gain during the pre-weaning phase is not the driving factor behind the changes in life-time productivity as the weight gained is inconsequential in terms of pre-lactation and weight gain. Furthermore, there are no differences in weight of heifers at the start of first lactation. The increased weight gain during the pre-weaning period must, therefore, initiate cellular changes within the animal. Research has focussed on increasing total nutritional supply or an increase in protein supply for promotion of such changes. The benefits of antioxidants in animal nutrition have been known for a long period of time. However, they have gained prominence with enforced reduction in use of antibiotics in many animal production systems. The role of antioxidants in nutrition of both the calf and the dam before parturition is critical for preventing disease and optimising growth weight of the pre-weaned calf. However, studies are yet to demonstrate a role, outside of preventive health, for the use of antioxidants in the pre-weaning period for increasing total life-time production of the dairy cow.

Oxidative stress and life histories: unresolved issues and current needs

Life‐history theory concerns the trade‐offs that mold the patterns of investment by animals between reproduction, growth, and survival. It is widely recognized that physiology plays a role in the mediation of life‐history trade‐offs, but the details remain obscure. As life‐history theory concerns aspects of investment in the soma that influence survival, understanding the physiological basis of life histories is related, but not identical, to understanding the process of aging. One idea from the field of aging that has gained considerable traction in the area of life histories is that life‐history trade‐offs may be mediated by free radical production and oxidative stress. We outline here developments in this field and summarize a number of important unresolved issues that may guide future research efforts. The issues are as follows. First, different tissues and macromolecular targets of oxidative stress respond differently during reproduction. The functional significance of these changes, however, remains uncertain. Consequently there is a need for studies that link oxidative stress measurements to functional outcomes, such as survival. Second, measurements of oxidative stress are often highly invasive or terminal. Terminal studies of oxidative stress in wild animals, where detailed life‐history information is available, cannot generally be performed without compromising the aims of the studies that generated the life‐history data. There is a need therefore for novel non‐invasive measurements of multi‐tissue oxidative stress. Third, laboratory studies provide unrivaled opportunities for experimental manipulation but may fail to expose the physiology underpinning life‐history effects, because of the benign laboratory environment. Fourth, the idea that oxidative stress might underlie life‐history trade‐offs does not make specific enough predictions that are amenable to testing. Moreover, there is a paucity of good alternative theoretical models on which contrasting predictions might be based. Fifth, there is an enormous diversity of life‐history variation to test the idea that oxidative stress may be a key mediator. So far we have only scratched the surface. Broadening the scope may reveal new strategies linked to the processes of oxidative damage and repair. Finally, understanding the trade‐offs in life histories and understanding the process of aging are related but not identical questions. Scientists inhabiting these two spheres of activity seldom collide, yet they have much to learn from each other.

The diagnostic and prognostic importance of oxidative stress biomarkers and acute phase proteins in Urinary Tract Infection (UTI) in camels

The present study aimed to investigate the diagnostic and prognostic importance of oxidative stress biomarkers and acute phase proteins in urinary tract infection (UTI) in camels. We describe the clinical, bacteriological and biochemical findings in 89 camels. Blood and urine samples from diseased (n = 74) and control camels (n = 15) were submitted to laboratory investigations. The urine analysis revealed high number of RBCS and pus cells. The concentrations of serum and erythrocytic malondialdehyde (sMDA & eMDA), Haptoglobin (Hp), serum amyloid A (SAA), Ceruloplasmin (Cp), fibrinogen (Fb), albumin, globulin and interleukin 6 (IL-6) were higher in diseased camels when compared to healthy ones. Catalase, super oxide dismutase and glutathione levels were lower in diseased camels when compared with control group. Forty one of 74 camels with UTI were successfully treated. The levels of malondialdehyde, catalase, super oxide dismutase, glutathione, Hp, SAA, Fb, total protein, globulin and IL-6 were associated with the odds of treatment failure. The MDA showed a great sensitivity (Se) and specificity (Sp) in predicting treatment failure (Se 85%/Sp 100%) as well as the SAA (Se 92%/Sp 87%) and globulin levels (Se 85%/Sp 100%) when using the cutoffs that maximizes the sum of Se + Sp. Multivariate logistic regression analysis revealed that two models had a high accuracy to predict failure with the first model including sex, sMDA and Hp as covariates (area under the receiver operating characteristic curve (AUC) = 0.92) and a second model using sex, SAA and Hp (AUC = 0.89). Conclusively, the oxidative stress biomarkers and acute phase proteins could be used as diagnostic and prognostic biomarkers in camel UTI management. Efforts should be forced to investigate such biomarkers in other species with UTI.

Oxidant/Antioxidant Balance in Animal Nutrition and Health: The Role of Protein Oxidation

This review examines the role that oxidative stress (OS), and protein oxidation in particular, plays in nutrition, metabolism, and health of farm animals. The route by which redox homeostasis is involved in some important physiological functions and the implications of the impairment of oxidative status on animal health and diseases is also examined. Proteins have various and, at the same time, unique biological functions and their oxidation can result in structural changes and various functional modifications. Protein oxidation seems to be involved in pathological conditions, such as respiratory diseases and parasitic infection; however, some studies also suggest that protein oxidation plays a crucial role in the regulation of important physiological functions, such as reproduction, nutrition, metabolism, lactation, gut health, and neonatal physiology. As the characterization of the mechanisms by which OS may influence metabolism and health is attracting considerable scientific interest, the aim of this review is to present veterinary scientists and clinicians with various aspects of oxidative damage to proteins.

Analysis of chromosome damage by sister chromatid exchange (SCE) and redox homeostasis characterization on sheep flocks from Sardinian pasturelands

Over the last decades, an increase of pollutants of diverse origin (industrial, military, mining, etc.) was recorded in several areas of Sardinia Island. We report the results of a multidisciplinary and complementary study based on cytogenetic and physiological analyses. The data obtained show the effects of the environmental impact on six sheep flocks (Sardinian breed) grazing on natural pasturelands next to possible polluted areas and compared to three herds grazing in different areas far from those potentially contaminated and used as control. Sister chromatid exchange (SCE) test was used as cytogenetic test to analyze chromosomal damages and it was performed on peripheral blood samples collected from 129 adult sheep (age > 4 years) randomly selected from polluted (92 animals) and control (37 animals) areas. Two types of cell cultures were performed: without (normal cultures) and with the addition of 5-BrdU. SCE-mean values estimated over 35 cells counted for each animal were 8.65 ± 3.40, 8.10 ± 3.50, 8.05 ± 3.08, 7.42 ± 3.34, 9.28 ± 3.56 and 8.38 ± 3.29 in the exposed areas, whereas the average values were 7.86 ± 3.31 in the control group. Significant increases (P < 0.01) of SCEs were found in three investigated areas of Southern Sardinia. Furthermore, sheep of the same flocks were characterized for blood redox homeostasis in order to define the potential targets of oxidative damage and to identify biomarkers of the extent of animal exposure to environmental contaminants. The plasma levels of Asc, Toc and Ret were found to be significantly lower (P < 0.001) in exposed sheep (I, II, IV and V) than in the control group. TAC as well as GPx and SOD activities were higher in control than in the exposed groups (P < 0.001). Finally, plasma levels of N-Tyr, PC, and LPO were significantly lower (P < 0.001) in the control group than in the exposed groups.

Immune and oxidative response to linseed in the diet of periparturient Holstein cows

The aim of this research was to determine the influence of dietary replacement of n-6 with n-3 polyunsaturated fatty acids on cellular immunity and oxidative stress in the transition period dairy cows. The experiment was conducted on 20 dairy Holstein cows from 3 ± 1 weeks before parturition until the 6th week of lactation. Both groups were fed an iso-energetic and iso-nitrogenous diet. Soybean meal from control (C) group was replaced with linseed in the experimental (LS) group. Cellular immunity and oxidative stress were measured on days -10, 1, 21 and 42 relative to parturition. During the entire experimental period, the proportion of CD45+ cells was lower (P<0.05) in LS group compared with the C group. The phagocytosis ability and phagocytosis index of cows fed with n-3 fatty acids were significantly reduced (P<0.05) compared with the group of cows fed with n-6 fatty acids. The most severe decrease in phagocytosis ability was on day -10 and 1 relative to parturition. The activity of superoxide dismutase (P<0.05) and plasma glutathione peroxidase (P<0.05) increased around calving, although activities were not influenced by dietary treatment. Increased malondialdehyde concentration (P<0.05) was influenced by dietary n-3 fatty acids and the time relative to parturition. The immune suppression was most pronounced during periparturient period. In that matter we can conclude that not only dietary n-3 fatty acids but also oxidative stress, which reached peak at time of parturition, contributed to the reduced cellular immunity during the periparturient period.

Supplementation of prepartum dairy cows with β-carotene

The prepartum supplementation of dairy cows with β-carotene was evaluated. Cows were blocked by parity and expected calving date and assigned to a treatment: β-carotene (1.2 g/cow per d) or control (no supplementation). The same total mixed ration batch was offered to all cows, and β-carotene was top dressed to individual cows once per day. The data set contained 283 Holsteins that received a treatment for >14 d (29.1±6.9 d). Frequency distributions were analyzed with the GENMOD procedure of SAS using logistic regression for binomial data. Continuous variables were analyzed with the MIXED procedure of SAS. Within parity, nonparametric estimates of the survivor function for reproductive variables were computed using the product-limit method of the Kaplan-Meier method with the LIFETEST procedure of SAS. Plasma β-carotene concentration before supplementation was similar between supplemented and nonsupplemented cows (2.99µg/mL) and peaked at 3.26±0.175µg/mL on d -15±2.4 precalving for supplemented cows (2.62±0.168µg/mL for control). Colostrum density, milk yield, and milk composition were similar between treatments. β-Carotene tended to increase milk protein content from 2.90 to 2.96% and to decrease the proportion of primiparous cows with a milk fat to protein ratio >1.5 from 22.6 to 6.4%. The proportion of primiparous and multiparous cows with difficult calving, metritis, progesterone >1 ng/mL at 21 d and at 42 d in lactation, % conception at first service, and % pregnancy at 90 and 150 d in lactation were similar between treatments. A trend for decreased incidence of somatic cell count >200,000 cells/mL was present in multiparous cows supplemented with β-carotene (38.9% vs. 28.1%). β-Carotene was associated with a reduction in the proportion of multiparous cows with retained placenta 12 h postpartum from 29.9 to 21.7%; time of placenta release was 392 min (340 to 440) for β-carotene and 490 min (395 to 540) for control (median and 95% confidence interval). For primiparous cows, placenta release was not affected by β-carotene (incidence was 15.4%). The intervals from calving to first estrus, to first service, and to conception were not affected by β-carotene supplementation in either parity. However, independent of treatment, cows with improved reproductive efficiency had increased postpartum β-carotene concentration in plasma. The prepartum supplementation of β-carotene increased plasma concentration around calving. No response in milk yield or reproductive performance was detected. Beta-carotene supplementation was associated with a lower incidence of retained placenta in multiparous cows.

Association of oxidative status and insulin sensitivity in periparturient dairy cattle: an observational study

Post-parturient insulin resistance (IR) is a common feature in all mammalian animals. However, in dairy cows, it can be exacerbated because of high milk yield, leading to excessive negative energy balance, which is related with increased disease incidence, reduced milk production and worsened reproductive performance. IR has been extensively investigated in humans suffering from diabetes mellitus. In these subjects, it is known that oxidative stress (OS) plays a causative role in the onset of IR. Although OS occurs in transitional dairy cattle, there are yet no studies that investigated the association between IR and OS in dairy cattle. Therefore, the aim of this study was to investigate whether there is a relationship between OS and IR in dairy cattle. Serum samples were taken repeatedly from 22 dairy cows from 2 months prior to the expected calving date to 2 months after calving and were analysed for markers of metabolic and redox balance. Surrogate indices of insulin sensitivity were also calculated. Generalised linear mixed models revealed an effect of the oxidative status on peripheral insulin concentration and on indices of insulin sensitivity. Hence, field trials should investigate the effectiveness of antioxidant therapy on insulin sensitivity in peripheral tissues during the transition period of dairy cattle.

Oxidative stress and antioxidant status in dairy cows during prepartal and postpartal periods

The aim of the present study was to evaluate the indicators of oxidative stress (malondialdehyde [MDA]) and antioxidant status (ferric reducing ability of plasma [FRAP]; superoxide dismutase [SOD]; glutathione peroxidase [GSH-Px]; selenium [Se]; vitamin E) in dairy cows of the Slovak Pied cattle from 3 weeks before parturition to 9 weeks after parturition. The mean MDA concentration was significantly (P < 0.001) higher in the cows 1 week after calving compared to the cows 3, 6, and 9 weeks after calving. The lowest mean FRAP value was found in the cows 3 weeks after parturition. The SOD activities were increased during the whole monitored time (ANOVA, P < 0.001). A significant (P < 0.05) decrease of GSH-Px activities was recorded in the cows 1 week after calving compared to the weeks 6 and 9 after calving. Statistical multiple comparison test showed no significant changes in Se between the examined groups. The lowest mean vitamin E concentration was found in the first week after parturition. Significantly positive correlations (P < 0.05) were recorded between Se and vitamin E (r = 0.897), SOD and GSH-Px (r = 0.903), while Se and GSH-Px had no significantly positive correlation (r = 0.520). Significant changes between MDA and indicators of oxidative stress (SOD, GSH-Px, vitamin E) confirm that during parturition and onset of lactation, oxidative stress occurs in dairy cows. Exposure of peripartal cows to oxidative stress may cause an increased incidence of metabolic diseases.

Silymarin and lycopene administration in periparturient dairy cows: effects on milk production and oxidative status

AIMS

To establish during late gestation and early lactation the effects of supplementing silymarin, a natural hepatoprotective substance, combined with a powerful antioxidant, lycopene, on milk production and on serum biomarkers of oxidative status.

METHODS

Italian Friesian dairy cows were given individually a supplement containing a mixture of silymarin (7.77 g/day/cow) and lycopene (1.27 g/day/cow) (n=10) or no supplement (control; n=10). Treatment was administered from 7 days before the expected calving date to the first 14 days in milk. At 7 days before the expected calving date, at calving, and 7 days postpartum, body condition score (BCS) and concentrations in serum of reactive oxygen metabolites (ROM), total antioxidant capacity (OXY) and thiobarbituric acid reactive substances (TBARS) were evaluated. Bodyweight, milk production, and somatic cell count (SCC) were determined at 7, 14 and 21 days postpartum.

RESULTS

The mean time of treatment prior to calving was 6.3 (min 4, max 11) days. Compared with control cows, treatment increased energy corrected milk yield (33.3 vs. 37.8 (SEM 1.10) kg/day; p=0.006) and milk fat yield (1.14 vs. 1.32 (SEM 0.06) kg/day; p=0.05) over the first 21 days of lactation. Treated cows had lower mean log10 SCC compared to control cows (4.9 vs. 5.24 (SEM 0.11) log10 cells/mL) and had lower overall concentration of TBARS (1.47 vs. 1.59 (SEM 0.016) nM/mL; p<0.001), but similar concentrations of ROM and OXY in serum. However there was a treatment by time interaction (p=0.09) for OXY, and at calving mean OXY was higher in treated cows compared with pre-calving values (p<0.001).

CONCLUSIONS

Despite the acknowledged limitation of the study, i.e. the small number of animals, our results suggest that silymarin and lycopene, as health-beneficial feed supplements, may help dairy cows in metabolic adaptation during the first stages of lactation.

CLINICAL RELEVANCE

During the peripartum period dairy cows suffer moderate-to-severe fatty liver and from an overproduction of free radicals. The supplementation of a mixture of silymarin and lycopene during these stressful days may be useful to mitigate these metabolic disorders with beneficial effects on the subsequent lactation.

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

The aim of this study was to assess the redox balance of organically managed dairy cattle (OMC; n = 40) during the transition period and to compare this with conventionally managed cattle (CMC; n = 22). Serum samples of dairy cows from two organic and one conventional farm were taken. Markers of oxidants production [reactive oxygen species] and total serum antioxidant capacity were measured in four different production stages: (i) far-off dry (2 to 1 months before calving; 44 samples in CMC and 48 in OMC); (ii) close-up dry (1 month until 3 days before calving; 44 CMC; 54 OMC); (iii) fresh (3 days to +1 month after calving; 44 CMC; 49 OMC); and (iv) peak of lactation (+1 to +3 months; 71 CMC; 78 OMC). Values were compared between production stages and against a metabolic baseline status (4th-5th month of pregnancy; 40 CMC; 30 OMC). Our results indicated that throughout the periparturient period, OMC had lower concentrations of reactive oxygen species, but also a lower antioxidant capacity than CMC. Indeed, when the two components of the redox balance were assessed together through the Oxidative Stress index, the values of this parameter were higher for OMC than for CMC, thereby implying a higher risk of oxidative stress. Therefore, further larger studies are needed to confirm the current observations, as organically reared animals might be exposed to a lack of antioxidants supply.

Oxidative shielding and the cost of reproduction

Life-history theory assumes that reproduction and lifespan are constrained by trade-offs which prevent their simultaneous increase. Recently, there has been considerable interest in the possibility that this cost of reproduction is mediated by oxidative stress. However, empirical tests of this theory have yielded equivocal support. We carried out a meta-analysis to examine associations between reproduction and oxidative damage across markers and tissues. We show that oxidative damage is positively associated with reproductive effort across females of various species. Yet paradoxically, categorical comparisons of breeders versus non-breeders reveal that transition to the reproductive state is associated with a step-change reduction in oxidative damage in certain tissues and markers. Developing offspring may be particularly sensitive to harm caused by oxidative damage in mothers. Therefore, such reductions could potentially function to shield reproducing mothers, gametes and developing offspring from oxidative insults that inevitably increase as a consequence of reproductive effort. According to this perspective, we hypothesise that the cost of reproduction is mediated by dual impacts of maternally-derived oxidative damage on mothers and offspring, and that mothers may be selected to diminish such damage. Such oxidative shielding may explain why many existing studies have concluded that reproduction has little or no oxidative cost. Future advance in life-history theory therefore needs to take account of potential transgenerational impacts of the mechanisms underlying life-history trade-offs.

Effect of additional chromium supplementation on health status, metabolic responses, and performance traits in periparturient Murrah Buffaloes (Bubalus bubalis)

This study was conducted to determine the effects of inorganic chromium (Cr) on body condition, metabolic responses, lactation performance, and reproductive parameters in periparturient Murrah buffaloes. Twenty-four multiparous advanced pregnant Murrah buffaloes were randomly assigned to four treatment diets. Feeding regimen was the same in all the groups, except that the animals in the four respective groups were additionally supplemented with 0.0, 0.5, 1.0, and 1.5 mg of Cr/kg dry matter (DM) from day 60 prepartum to 150 days postpartum. Dry matter intake (DMI) and milk production were recorded every day, while body condition score (BCS) and whole blood samples were collected at days -60, -45, -30, -15, -7, -3, 0, 3, 7, 15, 30, 45, 60, 90, 120, and 150 relative to actual calving. As the days to calving advanced, DMI, plasma glucose, insulin, leptin, and Cr levels decreased (P < 0.05), and the levels were minimum on the day of calving. In contrast, the concentration of nonesterified fatty acid (NEFA) increased (P < 0.05) and was found to be highest at parturition. No change in DMI as well as BCS was observed due to dietary treatments. Supplementation of Cr improved plasma concentration of glucose, leptin, and Cr levels. However, the concentration of insulin decreased (P < 0.05) with the increased level of supplemental Cr. Milk yield (kg/day) was improved significantly (P < 0.05) in groups supplemented with 1.0 or 1.5 mg Cr/DM; however, only a small change was recorded in the group fed 0.5 mg Cr/kg DM. Fat-corrected milk and energy-corrected milk were 28.78 and 42.32 % and 28.76 and 41.68 % higher in the 1.0 and 1.5 mg Cr/DM groups, respectively. Dietary Cr supplementation during the peripartum period had beneficial effects on the reproductive performance of buffaloes. These results could be interpreted as an improvement in the body condition, metabolic response, milk yield, efficiency of milk production and nutrient utilization, and reproductive performance of peripartum Murrah buffaloes.

Plasma parameters related to energy and lipid metabolism in periparturient Modenese and Italian Friesian cows

The aim of this work was to compare energy and lipid metabolism during the peripartum period between Modenese (MO) and Italian Friesian (IF) cows. The study was carried out on 33 pluriparous pregnant cows, 19 IF and 14 MO, reared together in the same herd and kept under equal conditions of management and nutrition. Blood was sampled from jugular vein starting 4 week before expected calving date until 4 week post-calving, once weekly. Plasma was analysed for glucose, NEFA, BHBA, triglycerides and cholesterol concentrations. Body condition score (BCS) was assessed weekly after blood sampling. Data from antepartum (a.p.) and post-partum (p.p.) periods were separately analysed as repeated measures by a linear mixed models with the effect of breed, time and their interaction as main factors and random cow within breed. The energy status differed between the two breeds during the peripartum period. We observed higher BCS a.p. and p.p. and lower BCS variations p.p. in MO compared to IF group. Modenese cows showed lower glucose and cholesterol concentrations (p < 0.001), but higher NEFA values, NEFA to cholesterol and NEFA to albumin ratios (p < 0.001) during a.p.; on the contrary, IF cows had higher (p < 0.05) cholesterol, NEFA, BHBA levels and NEFA to albumin ratio than MO ones during p.p. The differences observed between the two breeds suggest how MO cows are subjected to lipid mobilization during late gestation; on the contrary, IF cows are predisposed to mobilize their lipid reserves at the beginning of lactation to support high production. The results indicate a diverse ability to cope with metabolic stress and suggest the hypothesis that the differences in concentrations of plasma parameters and their variation amplitude around the calving period might depend on the different genetic merit for milk production between the two breeds.

Body condition, energy balance and immune status of periparturient Murrah buffaloes (Bubalus bubalis) supplemented with inorganic chromium

Periparturient Murrah buffaloes were used to determine whether body condition, energy balance and immune status are affected by inorganic Cr supplementation. Twenty-four Murrah buffaloes were blocked into four groups having six animals in each group and fed for 60 days pre-partum to 150 days post-partum. Feeding regimen was same in all the groups except that these were supplemented with 0.0, 0.5, 1.0 and 1.5 of Cr per kilogram of dry matter (DM) in the four respective groups. Buffaloes were weighed at fortnightly intervals. Blood samples were collected from the jugular vein at days -60, -30, -15, -7, 0, 7, 15, 30, 60, 90, 120 and 150 of experimental feeding for the estimation of non-esterified fatty acid (NEFA), beta-hydroxybutyric acid (BHBA), Cr level, lymphocyte proliferation, neutrophil phagocytic activity, plasma total immunoglobulin (TIg), immunoglobulin G (IgG) and cortisol levels. Results revealed that with approaching parturition, dry matter intake (DMI), immune response and plasma Cr level decreased (P < 0.05) gradually and minimum values were observed on the day of parturition in all groups. In contrast, body condition score (BCS), plasma NEFA and BHBA concentrations showed increasing (P < 0.05) trends towards calving and level decreased after calving. Dietary Cr supplementation did not have any effect on DMI and BCS, but immune response and plasma Cr concentration showed a positive correlation with dietary Cr supplementation. Buffaloes supplemented with 1.5 mg/kg Cr had significantly (P < 0.05) low plasma NEFA and BHBA concentrations. The results of present findings indicated that dietary inorganic Cr supplementation reduced lipid mobilization and improved immune response in periparturient buffaloes.

A comparative study of the metabolic profile, insulin sensitivity and inflammatory response between organically and conventionally managed dairy cattle during the periparturient period

The number of organically managed cattle (OMC) within the European Union has increased tremendously in the last decade. However, there are still some concerns about animals under this farming system meeting their dietary requirements for milk production. The aim of this study was to compare the metabolic adaptations to the onset of lactation in three different herds, one conventional and two organic ones. Twenty-two conventionally managed cattle (CMC) and 20 from each organic farm were sampled throughout the periparturient period. These samplings were grouped into four different stages: (i) far-off dry, (ii) close-up dry, (iii) fresh and (iv) peak of lactation and compared among them. In addition, the results of periparturient animals were also compared within each management type with a control group (animals between the 4th and 5th months of pregnancy). Metabolic profiles were used to assess the health status of the herds, along with the quantification of the acute phase proteins haptoglobin and serum amyloid A, insulin and the calculation of different surrogate indices of insulin sensitivity. Generalised linear mixed models with repeated measurements were used to study the effect of the stage, management type or their interaction on the serum variables studied. The prevalence of subclinical ketosis was higher in OMC, although they showed better insulin sensitivity, a lower degree of inflammation and less liver injury, without a higher risk of macromineral deficiencies. Therefore, attention should be paid on organic farms to the nutritional management of cows around the time of calving in order to prevent the harmful consequences of excessive negative energy balance. Moreover, it must be taken into account that most of the common practices used to treat this condition in CMC are not allowed on a systematic basis in OMC.

Energy metabolites, lipid variables and lactation performance of periparturient Murrah buffaloes (Bubalus bubalis) fed on diet supplemented with inorganic chromium

The aim of this study was to elucidate the effects of chromium (Cr) supplementation as inorganic Cr (CrCl3·6H2O) on energy balance, lipid peroxidation, and lactation performance in periparturient Murrah buffaloes. Twenty-four multiparous Murrah buffaloes according to lactation, parity, body mass, and expected calving date were divided equally. Experimental buffaloes were randomly assigned to four treatment diets: a control diet and three diets with an inorganic Cr supplementation at 0.5, 1.0, and 1.5 mg of Cr/kg dry matter (DM), respectively from 60 days before expected calving date until 60 days of lactation. Milk productions of buffaloes were recorded every day until 60 days in milk. Blood samples were collected at days -60, -45, -30,-21, -15, -7, -3, 0, 7, 15, 21, 30, 45, and 60 days relative to actual calving for determination of plasma glucose, nonesterified fatty acid (NEFA), thiobarbituric acid reactive substance (TBARS), total cholesterol, total protein, albumin, blood urea nitrogen (BUN), and minerals. Adding inorganic Cr to the diet of Murrah buffaloes increased milk yield. Percentage of fat and total solid yield increased significantly through the experiment in the Cr-supplemented group. At the day of calving, buffaloes showed a decrease in dry matter intake (DMI), plasma glucose, and zinc (Zn) and Cr concentrations. In contrast, plasma NEFA, TBARS, and copper (Cu) levels were found highest at the day of calving among all groups. Cr supplementation increased peripheral blood glucose concentration while decreased level of NEFA and TBARS was recorded in Cr-fed buffaloes. Supplemental Cr had no effect on plasma cholesterol, total protein, albumin, and BUN in periparturient period. Dietary Cr supplementation had positive effect on plasma Cr concentration, but the plasma concentration of Cu, Zn, and iron (Fe) was not affected by different dietary Cr level supplementation. The results suggest that dietary inorganic Cr supplementation improved milk yield by reducing negative energy balance and lipid peroxidation in buffaloes during periparturient period.

Amelioration of reproduction-associated oxidative stress in a viviparous insect is critical to prevent reproductive senescence

Impact of reproductive processes upon female health has yielded conflicting results; particularly in relation to the role of reproduction-associated stress. We used the viviparous tsetse fly to determine if lactation, birth and involution lead to damage from oxidative stress (OS) that impairs subsequent reproductive cycles. Tsetse females carry an intrauterine larva to full term at each pregnancy cycle, and lactate to nourish them with milk secretions produced by the accessory gland ( = milk gland) organ. Unlike most K-strategists, tsetse females lack an apparent period of reproductive senescence allowing the production of 8-10 progeny over their entire life span. In a lactating female, over 47% of the maternal transcriptome is associated with the generation of milk proteins. The resulting single larval offspring weighs as much as the mother at birth. In studying this process we noted an increase in specific antioxidant enzyme (AOE) transcripts and enzymatic activity at critical times during lactation, birth and involution in the milk gland/fat body organ and the uterus. Suppression of superoxide dismutase (sod) decreased fecundity in subsequent reproductive cycles in young mothers and nearly abolished fecundity in geriatric females. Loss of fecundity was in part due to the inability of the mother to produce adequate milk to support larval growth. Longevity was also impaired after sod knockdown. Generation of OS in virgin females through exogenous treatment with hydrogen peroxide at times corresponding to pregnancy intervals reduced survival, which was exacerbated by sod knockdown. AOE expression may prevent oxidative damage associated with the generation of nutrients by the milk gland, parturition and milk gland breakdown. Our results indicate that prevention of OS is essential for females to meet the growing nutritional demands of juveniles during pregnancy and to repair the damage that occurs at birth. This process is particularly important for females to remain fecund during the latter portion of their lifetime.

Bovine mammary stem cells: new perspective for dairy science

Mammary stem cells provide opportunities for the cyclic remodelling of the bovine mammary gland. Therefore, understanding the character and regulation of mammary stem cells is important for increasing animal health and productivity. The exciting possibility that stem cell expansion can influence milk production is currently being investigated by several researchers. In fact, appropriate regulation of mammary stem cells could hopefully benefit milk yield, persistency of lactation, dry period management and tissue repair. Accordingly, we and others have attempted to characterize and regulate the function of bovine mammary stem cells. However, research on mammary stem cells requires tissue biopsies, which represents a limitation for the management of animal welfare. Interestingly, different studies recently reported the identification of putative mammary stem cells in human breast milk. The possible identification of primitive cell types within cow's milk may provide a non-invasive source of relevant mammary cells for a wide range of applications. In this review, we have summarized the main achievements in this field for dairy cow science and described the interesting perspectives open to manipulate milk persistency during lactation and to cope with oxidative stress during the transition period by regulating mammary stem cells.

Effect of supplementation with antioxidants on the quality of bovine milk and meat production

From a clinical point of view, oxidative stress (OS) is considered the primary cause of numerous metabolic processes in transition cow. Thus, the addition of antioxidants has been considered a palliative or preventive treatment. But beyond the clinical perspective, antioxidant supplementation provides an added value to the product obtained being either milk or meat. This paper reviews the beneficial aspects that provide antioxidant supplementation on quality of both products and that fit into the new concept that the consumer has a functional and healthy food. Our approach is from a veterinary standpoint, by reviewing the studies conducted to date and the new perspectives that are interesting and need to be studied in the following years. One of the highlights is that sustainable farming, one in which production is combined with animal health, also impacts positively on the quality of the final products, with beneficial antioxidant properties to human health.

Effect of vitamin e and zinc supplementation on energy metabolites, lipid peroxidation, and milk production in peripartum sahiwal cows

The study was conducted to evaluate the effect of vitamin E and zinc supplementation on energy metabolites, lipid peroxidation, and milk production in peripartum Sahiwal cows. For this, thirty-two pregnant dry Sahiwal cows were selected at sixty days prepartum and divided into four groups viz control, T1, T2, and T3 of eight each. Group T1 were supplemented with zinc at 60 ppm/d/cow, group T2 were supplemented with vitamin E at 1,000 IU/d/cow and group T3 were supplemented with combination of vitamin E at 1,000 IU/d/cow and zinc at 60 ppm/d/cow during d 60 prepartum to d 90 postpartum. Blood samples were collected on d -60, -45, -30, -15, -7, -3, 0, 3, 7, 15, 30, 45, 60, 90, and 120 with respect to day of parturition and analysed for glucose, non esterified fatty acid, and thiobarbituric acid reactive substance. Body condition score was maintained significantly better (p<0.05) in T3 than in the control, T1 and T2 groups. Overall glucose level was higher (p<0.05) in T3 than control, T1, and T2 groups. Levels of nonesterified fatty acid, and thiobarbituric acid reactive substance were lower (p<0.05) in T3 than control, T1, and T2 groups. Milk yield was higher (p<0.05) in T3 than control, T1, and T2 groups. In conclusion, the present study indicated that the supplementation of vitamin E and zinc in peripartum Sahiwal cows enhanced milk production by reducing negative energy balance.

Effects of reproduction on immuno-suppression and oxidative damage, and hence support or otherwise for their roles as mechanisms underpinning life history trade-offs, are tissue and assay dependent

Life history parameters appear to be traded off against each other, but the physiological mechanisms involved remain unclear. One hypothesis is that potentially energetically costly processes such as immune function and protection from oxidative stress may be compromised during reproductive attempts because of selective resource allocation. Lower temperatures also impose energy costs, and hence allocation decisions might be more pronounced when animals are forced to reproduce in the cold. Here, we experimentally tested whether reproduction at different ambient temperatures was associated with elevated oxidative stress and suppressed immune function in Mongolian gerbils (Meriones unguiculatus). Using a variety of different markers for both immune function and oxidative stress, we found that some measures of immune function (serum bactericidal capacity and size of the thymus) were significantly suppressed, while some measures of oxidative protection [serum superoxide dismutase (SOD) activity and glutathione peroxidase (GPx) activity] were also reduced, and a marker of oxidative damage (protein carbonyls in serum) was increased in lactating compared with non-reproductive gerbils. These changes were in line with the selective resource allocation predictions. However, the phytohaemagglutinin response and serum total immunoglobulin (IgG) were not suppressed, and other markers of oxidative damage [malondialdehyde (MDA) (TBARS) and protein carbonyls in the liver] were actually lower in lactating compared with non-reproductive gerbils, consistent with increased levels of SOD activity and total antioxidant capacity in the liver. These latter changes were opposite of the expectations based on resource allocation. Furthermore, other measures of protection (GPx levels in the liver and protein thiols in both serum and liver) and damage [MDA (TBARS) in serum] were unrelated to reproductive status. Ambient temperature differences did not impact on these patterns. Collectively, our results indicated that the inferred effects of reproduction on immunosuppression and oxidative damage, and hence support or otherwise for particular physiological mechanisms that underpin life history trade-offs, are critically dependent on the exact markers and tissues used. This may be because during reproduction individuals selectively allocate protection to some key tissues, but sacrifice protection of others.

Oxytocin induced oxidative stress in lactating Bubalis bubalis (Nili Ravi)

Background

Oxytocin has been reported for a wide range of adverse effects in different species of lactating animals. The present study was aimed to evaluate the adverse effects of oxytocin on biomarkers of oxidative stress in buffaloes. Lactating buffaloes (n = 40) were randomly selected from a commercial dairy farm located in the peri-urban area of district Faisalabad, Pakistan and divided into two equal groups viz. treatment and control groups, each containing 20 buffaloes. Buffaloes in treatment group were injected with oxytocin before each milking (morning and evening) for milk let down; whereas, animals in control group were milked naturally without oxytocin injection. Both the groups were assessed for oxidative stress biomarkers.

Results

Results showed significantly higher levels (P ≤ 0.05) of TOS, tHcy and ceruloplasmin oxidase activity in lactating buffaloes injected with oxytocin as compared to those of control group. On the other hand, serum levels of TAS, PON1 and arylesterase were significantly lower (P ≤ 0.05) in the buffaloes of treatment group.

Conclusions

Oxytocin injection in lactating buffaloes resulted in elevated oxidative stress by increasing the total homocysteine and ceruloplasmin oxidase activity and decreasing enzymatic activities of antioxidant enzymes including paraoxonase-1 and arylesterase; that might render the animals to poor productive and reproductive potential.

Effects of chestnut tannins on performance and antioxidative status of transition dairy cows

This study was conducted to evaluate the effects of chestnut tannins (CT) on performance and antioxidative status of transition dairy cows. Twenty multiparous Chinese Holstein cows in late gestation were paired according to expected calving date and randomly assigned either to a diet supplemented with CT (CNT, 10 g of CT/kg of diet, dry matter basis) or to an unsupplemented control (CON) diet from 3 wk prepartum to 3 wk postpartum. Blood samples were taken on d -21, 1, 7, and 21 relative to calving for analysis of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and malondialdehyde (MDA). Liver samples were taken by puncture biopsy on d 1 and 21 relative to calving for analysis of SOD, GSH-Px, and MDA. Data were analyzed for a completely randomized block design with repeated measures. The addition of CT had no significant effects on dry matter intake, body weight, body condition score, milk yield, 3.5% fat-corrected milk yield, and milk composition but did decrease milk MDA and somatic cell score in transition dairy cows. Dry matter intake decreased from d -21 to 0 and increased from d 1 to 21 relative to calving across treatments. During the experimental period, body weight and body condition score decreased, whereas milk MDA and somatic cell score increased across treatments. A time effect was also observed for plasma MDA, which peaked on d 1 relative to calving and remained higher than that on d -21 relative to calving across treatments. Addition of CT decreased MDA concentrations in plasma and liver. Neither time nor CT × time effects were observed for SOD and T-AOC in plasma and SOD and GSH-Px in liver; a time effect was observed for plasma GSH-Px, which peaked on d 1 relative to calving and remained higher than those on d -21 relative to calving across treatments. Addition of CT increased SOD, GSH-Px, and T-AOC activities in plasma and SOD and GSH-Px activities in liver. In conclusion, addition of CT might inhibit lipid peroxidation and increase antioxidant enzymes activities in plasma and liver of transition dairy cows. Supplementation of CT may be a feasible means to improve the antioxidative status of transition dairy cows.

The influence of the duration of the expulsive stage of parturition on the occurrence of postpartum oxidative stress in sows with uncomplicated, spontaneous farrowings

The aim of the study was to determine the influence of the duration of the expulsive stage of parturition on the occurrence of postpartum oxidative stress in sows with uncomplicated, spontaneous farrowings. Twenty-five pregnant gilts were divided into three groups on the basis of duration of the expulsive stage of farrowing: (I) duration of the expulsive stage was below 3 hours; (II) duration of the expulsive stage ranged from 3 to 6 hours; (III) duration of the expulsive stage was longer than 6 hours. Blood samples were collected at 24 to 48 hours before and 24 hours after parturition. As indicators of alterations in the redox state, we quantified the enzymatic activity of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT), as well as the blood levels of glutathione (GSH), thiobarbituric acid reactive substances (TBARS), and sulfhydryl groups (SH groups). In group III, it was found that erythrocyte activity of CAT (63.89 ± 6.70 vs. 53.18 ± 2.32 U/g Hb), as well as plasma GSH concentration (0.088 ± 0.020 vs. 0.045 ± 0.024 mmol/g protein) and SH groups content (5.045 ± 1.256 vs. 3.383 ± 0.430 μmol/g protein) decreased significantly (P < 0.05) at 24 hours after parturition, compared with their values during the last 48 hours before parturition. The concentration of TBARS increased not significantly, although markedly at 24 hours postpartum in group III (0.124 ± 0.014 vs. 0.153 ± 0.031 μmol/g protein). The results indicate that uncomplicated, spontaneous parturition can lead to the occurrence of oxidative stress during the early postparturient period in sows, the intensity of which is related to the duration of the expulsive stage.

Effect of nitric oxide on physical development and erythropoiesis in the offspring of rats with impaired uteroplacental circulation

We evaluated physical development and activity of erythropoiesis in the offspring of rats with experimentally impaired uteroplacental circulation as well as the effect of exogenous nitric oxide donator used during pregnancy, on offspring development. Exogenous NO producing an anti-hypoxic effects contributes to the increase in somatometric parameters of the offspring on postnatal days 15 and 30. The rates of erythropoiesis in the liver and bone marrow did not differ from the normal; hemopoietic organs were not overstrained, which prevented exhaustion and failure of functional reserves of the erythrocyte system.

Mammary gene expression and activity of antioxidant enzymes and oxidative indicators in the blood, milk, mammary tissue and ruminal fluid of dairy cows fed flax meal

The effects of flax meal (FM) on the activity of antioxidant enzymes (superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT)) in the blood, mammary tissue and ruminal fluid, and oxidative stress indicators (thiobarbituric acid-reactive substances(TBARS) and 1,1-diphenyl-2-picrylhydrazyl-scavenging activity) in the milk, plasma and ruminal fluid of dairy cows were determined.The mRNA abundance of the antioxidant enzymes and oxidative stress-related genes was assessed in mammary tissue. A total of eight Holstein cows were used in a double 4 x 4 Latin square design. There were four treatments in the diet: control with no FM(CON) or 5% FM (5FM), 10% FM (10FM) and 15% FM (15FM). There was an interaction between treatment and time for plasma GPx and CAT activities. Cows supplemented with FM had a linear reduction in TBARS at 2 h after feeding, and there was no treatment effect at 0, 4 and 6 h after feeding. TBARS production decreased in the milk of cows fed the 5FM and 10FM diets. There was a linear increase in nuclear factor (erythroid-derived 2)-like 2 (NFE2L2) mRNA abundance in mammary tissue with FM supplementation.A linear trend for increased mRNA abundance of the CAT gene was observed with higher concentrations of FM. The mRNA abundance of CAT, GPx1, GPx3, SOD1, SOD2, SOD3 and nuclear factor of k light polypeptide gene enhancer in B-cells (NFKB) genes was not affected by the treatment. These findings suggest that FM supplementation can improve the oxidative status of Holstein cows as suggested by decreased TBARS production in ruminal fluid 2 h post-feeding and increased NFE2L2/nuclear factor-E2-related factor 2 (Nrf2) mRNA abundance in mammary tissue.

Oral supplementation of medium-chain fatty acids during the dry period supports the neutrophil viability of peripartum dairy cows

A randomised clinical trial was conducted to explore the effect of orally supplemented medium-chain fatty acids (MCFA) to heifers and cows starting 6-8 weeks prior to expected calving date on blood and milk polymorphonuclear neutrophilic leucocyte (PMNL) apoptosis between 1 and 3 d in milk (DIM). The effects of MCFA-supplementation on the likelihood of intramammary infections (IMI) in early lactation, and test-day somatic cell count (SCC) and average daily milk yield (MY) during the first 4 months of lactation were evaluated as well. Twenty-two animals were included of which half were orally supplemented with MCFA starting 6-8 weeks prior to calving and half served as non-supplemented controls. The PMNL viability in both blood and milk was quantified using dual-colour flow cytometry with fluorescein-labelled annexin and propidium iodide. In non-supplemented animals, % blood PMNL apoptosis significantly increased between start of supplementation and early lactation, reflecting a potential reduction in innate immune capacity, whereas this was not true in the MCFA-supplemented animals. Similar results were seen in milk PMNL apoptosis. Overall, the % apoptotic milk PMNL between 1 and 3 DIM was significantly lower in the MCFA-supplemented group compared with the non-supplemented group. There was no substantial effect of oral MCFA-supplementation on the likelihood of quarter IMI nor on the composite test-day milk SCC or average daily MY. In conclusion, oral MCFA-supplementation starting 6-8 weeks before expected calving date supported the blood and milk neutrophil viability in early lactating dairy cows. Still, this was not reflected in an improvement of udder health nor MY in early and later lactation. The results should trigger research to further unravel the mechanisms behind the observed immunomodulating effect, and the potential relevance for the cows' performances throughout lactation.

Preliminary results in the redox balance in healthy cats: influence of age and gender

Oxidative stress (OS) impairs organic function and is considered causally related to cellular senescence and death. This study aims to evaluate if the redox balance varies in relation to age and gender in healthy cats. To quantify the oxidative status of this species we determined the oxidative damage as serum reactive oxygen metabolites (ROM) and the total serum antioxidant capacity (SAC). In addition, we used the ratio of ROM to SAC as a measure of the oxidative balance, with higher values meaning higher oxidative stress (oxidative stress index). Our results suggest that the male population is at oxidative risk when compared with females, especially between the age of 2 and 7 years. Nutritional strategies in this population looking for additional antioxidant support would probably avoid the oxidative stress status that predisposes to chronic processes in senior male cats. Further clinical trials in this field are recommended.

Oxidative stress index (OSi) as a new tool to assess redox status in dairy cattle during the transition period

Oxidative stress (OS) plays a key role in the initiation or progression of numerous diseases, and dairy cows undergo OS at the transition period. However, discrepancies between methodologies make it difficult to make comparisons between studies, and therefore research on this topic may not be implemented in farms. This study aims to test under field conditions the use of an oxidative stress index (OSi) as a combined measurement through a ratio between pro-oxidants and antioxidants throughout the transition period in dairy farms. Serum samples of high-yielding dairy cows were taken, and markers of oxidative damage and antioxidant capacity were measured in four different production stages: (i) late lactation (LL; -2 to -1 months); (ii) prepartum (PrP; -1 month until parturition); (iii) postpartum (PsP; delivery to +1 month); and (iv) peak of lactation (PkL; +1 to +2.5 months). Values were compared between production stages and against a metabolic baseline status (CTR, 4th to 5th month of gestation). To the best of our knowledge, this is the first report in the literature that discusses the values of these oxidative stress biomarkers (and the OS index) for cows with low metabolic demands, as to date most research in this area has focused on the transition period. With the joint evaluation through the OSi, differences were found that were not present with the separate evaluation of pro-oxidants or antioxidants, thus supporting our hypothesis that the OSi indicates more accurately the oxidative status of the animals. It was also confirmed that dairy cows undergo OS after parturition, and that antioxidant supplementation from 1 month before parturition until the peak of lactation may be needed to reduce the risk of OS.

The presence of SOD 1 and GSH-Px in bovine retained and properly released foetal membranes

The maintenance of antioxidative/oxidative balance is crucial for cellular and extracellular environment. That is why antioxidative enzymes express their activity in different isoforms in different cell compartments and extracellular space. The aim of study was to verify the results of previous experiment on activities of antioxidative enzymes by the determination of their enzymatic proteins in bovine placental tissues by Western blotting technique. Moreover, the presence of particular isoenzymes was detected and differentiated. Homogenates of maternal and foetal part of both properly released and retained bovine placenta were subjected to PAGE electrophoresis in non-reducing and reducing conditions and Western blotting with appropriate antibodies against superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Electrophoresis allowed for the detection of protein bands of molecular weight related to CuZn-SOD as well as cGSH-Px isoenzymes. The reaction with appropriate antibodies confirmed this. Densitometric analysis, although semi-quantitative, allowed for the observation of trends in differences in antioxidative enzyme proteins, which may partly confirm previously described results in cases of retained and released placenta. Local antioxidative enzymatic mechanisms in bovine placental tissues are represented by CuZn-SOD and cGSH-Px, which show the changes in their expression during improper placental release.