Response of cows consuming adequate selenium to vitamin E and selenium supplementation prepartum

Role of antioxidants and trace elements in health and immunity of transition dairy cows

A number of antioxidants and trace minerals have important roles in immune function and may affect health in transition dairy cows. Vitamin E and beta-carotene are important cellular antioxidants. Selenium (Se) is involved in the antioxidant system via its role in the enzyme glutathione peroxidase. Inadequate dietary vitamin E or Se decreases neutrophil function during the perpariturient period. Supplementation of vitamin E and/or Se has reduced the incidence of mastitis and retained placenta, and reduced duration of clinical symptoms of mastitis in some experiments. Research has indicated that beta-carotene supplementation may enhance immunity and reduce the incidence of retained placenta and metritis in dairy cows. Marginal copper deficiency resulted in reduced neutrophil killing and decreased interferon production by mononuclear cells. Copper supplementation of a diet marginal in copper reduced the peak clinical response during experimental Escherichia coli mastitis. Limited research indicated that chromium supplementation during the transition period may increase immunity and reduce the incidence of retained placenta.

A meta-analysis of the effects of Vitamin E supplementation on the incidence of retained foetal membranes in dairy cows

A meta-analysis was performed to consolidate the results of studies which have evaluated the effects of Vitamin E supplementation during the dry period on the risk of retained foetal membranes (RFM) in the dairy cow. Twenty studies demonstrated a beneficial response to Vitamin E whilst 21 found no benefit and 3 reported an increase in the incidence of RFM in treated cows. The odds ratios (OR) of the available studies exhibited significant heterogeneity, so multivariable logistic regression analysis was performed to enable the identification of factors associated with the response to Vitamin E supplementation. Our multivariable analysis included parity and Vitamin E supplementation (control/treated) in the model, because all other factors were co-linear. Results indicated that Vitamin E supplementation led to a reduction in the incidence of RFM. A second multivariable analysis was undertaken on a subset of the data including only supplemented cows to determine the influence of supplementation factors on the risk of RFM. All factors were co-linear with each other, therefore, only type of Vitamin E supplementation was included in this analysis. The regression model demonstrated that administration of the synthetic Vitamin E alpha-tocopheryl acetate was associated with a lower risk of RFM than treatment with natural Vitamin E (alpha-tocopherol) (P=0.047, OR=0.49), whereas the difference between the synthetic Vitamin E alpha-tocopherol acetate and natural Vitamin E just failed to attain statistical significance (P=0.059, OR=0.53). Overall the analyses indicate that Vitamin E supplementation during the dry period is associated with a reduced risk of RFM, and that the synthetic forms of Vitamin E are more effective than the natural compound.

Effect of Se on selenoprotein activity and thyroid hormone metabolism in beef and dairy cows and calves

Although Se is essential for antioxidant and thyroid hormone function, factors influencing its requirement are not well understood. A survey and two experiments were conducted to determine the influence of cattle breed and age on selenoprotein activity and the effect of maternal Se supplementation on cow and calf selenoprotein activity and neonatal thyroid hormone production. In our survey, four cowherds of different ages representing three breeds were bled to determine the influence of breed and age on erythrocyte glutathione peroxidase activity (RBC GPX-1). All females were nonlactating, pregnant, and consumed total mixed diets (Holstein) or grazed pasture (Angus and Hereford). In our survey of beef breeds, yearlings had greater average RBC GPX-1 activity than mature cows. In Exp. 1, neonatal Holstein heifers (n = 8) were bled daily from 0 to 6 d of age to determine thyroid hormone profile. An injection of Se and vitamin E (BO-SE) was given after the initial bleeding. Thyroxine (T4) and triiodothyronine (T3) concentrations were greatest on d 0 and decreased (P < 0.05) continuously until d 5 postpartum (156.13 to 65.88 and 6.69 to 1.95 nmol/L, d 0 to 5 for T4 and T3, respectively). Reverse T3 concentrations were 3.1 nmol/L on d 0 and decreased (P < 0.05) to 0.52 nmol/ L by d 5. In Exp. 2, multiparous Hereford cows were drenched weekly with either a placebo containing 10 mL of double-deionized H2O (n = 14) or 20 mg of Se as sodium selenite (n = 13). After 2 mo of treatment, Se-drenched cows had greater (P < 0.01) plasma concentrations than control cows (84.92 vs. 67.08 ng/mL), and at parturition, they had plasma Se concentrations twofold greater than (P < 0.05) control cows (95.51 vs. 47.14 ng Se/mL). After 4 mo, cows receiving Se had greater (P < 0.05) RBC GPX-1 activity than controls; this trend continued until parturition. Colostrum Se concentration was twofold greater (P < 0.05) in Se-drenched cows than control cows (169.97 vs. 87.00 ng/mL). Calves born to cows drenched with Se had greater (P < 0.05) plasma Se concentration, RBC GPX-1, and plasma glutathione peroxidase activity on d 0 compared with calves born to control cows. By d 7, no differences in plasma glutathione peroxidase activity in calves were observed. Maternal Se supplementation did not influence calf thyroid hormone concentrations. Selenium provided by salt and forages is not adequate for cattle in Se-deficient states.

Manipulation of antioxidant status fails to improve fertility of lactating cows or survival of heat-shocked embryos

Experiments were conducted to test whether enhancement of antioxidant status could improve fertility and milk yield in dairy cows and resistance of cultured embryos to heat shock. Three experiments in three herds were performed to evaluate the effect of multiple intramuscular injections of 500 mg of vitamin E and 50 mg of selenium at 8 to 21 d before expected calving and at 30 and 80 d postpartum on reproduction of lactating Holstein cows. Vitamin E and selenium injections did not improve reproductive function or milk yield in any of the studies. The predicted 305-d milk yield (averages of least-squares means across treatments) were: 9478, 7073, and 10,204 kg projected 305-d milk for experiments 1, 2, and 3, respectively. Percentages of cows pregnant at first service were 30, 16, and 24% in experiments 1, 2, and 3, respectively. Three studies were performed to test whether vitamin E improved development of cultured bovine embryos exposed to heat shock. Heat shock of 41 degrees C at the two-cell stage reduced development to the blastocyst stage, but culture with 100 microM vitamin E did not reduce effects of heat shock on impaired development. For example, 9 h at 41 degrees C reduced blastocyst development from 51.2 +/- 3.3% to 3.4 +/- 3.3% in the absence of vitamin E and from 54.0 +/- 3.3% to 5.2 +/- 3.3% in the presence of vitamin E. Development of morulae to the blastocyst stage was not compromised by culture at 41 degrees C for 9 h. Additionally, there was no overall effect of vitamin E on morula development. In conclusion, multiple injections of vitamin E and selenium at the administered levels did not improve postpartum fertility nor milk yield of lactating Holstein cows in three different herds, and there was no direct thermoprotective effect of vitamin E for cultured, heat-shocked embryos.

The influences of dietary intakes and supplementation with selenium and vitamin E on reproduction diseases and reproductive efficiency in cattle and sheep

Retained placenta, endometritis, cystic ovaries and low conception rates are often considered as interconnected conditions in cattle. Wide ranges in amounts of selenium and vitamin E supplements have been advised in late-pregnancy diets and, frequently, they can be synergistically beneficial. Animals at grass or with other green foods should be of adequate vitamin E status, but dietary selenium deficiencies are both more frequent and severe. Selenium status is important for super-ovulation in cattle and multiple births in ewes because of its importance in sperm transport and establishment of ova. However, the potential toxicity of selenium-enriched feed supplements restricts their use on a free-access basis. Giving sodium selenite or selenate by injection provides only a short-term response in the plasma. Barium selenate given in oil by injection provides a more durable response but has potential tissue residue problems. Compressed metallic selenium powder with iron powder in high-density reticulo-ruminal pellets gives sustained release, but uncertainties regarding possible surface coating and the variable effects of selenium particle size may require additional grinders to ensure prolonged release. Neither reticulo-ruminal pellets of such composition nor barium selenate by injection may be used worldwide because only sodium selenite and selenate have general regulatory approval. A sustained-release multi-trace element/vitamin rumen bolus system effective for several months has increased lambing percentages in ewes, and increased herd conception rates and reduced the spread of calving for herds of beef cattle.

Effects of supplemental parenteral administration of vitamin E and selenium to Jerseys and Holsteins during the nonlactating period

OBJECTIVE

To determine effects of breed and supplemental administration of vitamin E and selenium (Se) during late gestation on circulating concentrations of these micronutrients in periparturient Jerseys and Holsteins.

DESIGN

Randomized controlled clinical study.

ANIMALS

16 Jersey and 36 Holstein cows.

PROCEDURE

Cows were allotted to blocks on the basis of breed and expected parturition date. Cows within blocks were randomly assigned to be given vitamin E or Se parenterally 3 to 4 weeks prior to anticipated parturition in a 2 x 2 factorial design.

RESULTS

Results of ANOVA indicated Jerseys had higher blood concentrations of Se and lower serum concentrations of vitamin E than Holsteins at the end of lactation. Jerseys had higher blood concentrations of Se than Holsteins 3 to 4 weeks prior to parturition and at parturition. Selenium administration increased blood concentrations of Se at parturition. Administration of nutrients did not affect serum concentrations of vitamin E at parturition or 2 to 3 weeks after parturition or blood concentrations of Se 2 to 3 weeks after parturition.

CONCLUSIONS AND CLINICAL RELEVANCE

Jerseys and Holsteins consuming rations of comparable Se content differ in blood concentrations of Se during the nonlactating period, suggesting breed-related differences in Se metabolism during late lactation and the nonlactating period. Parenteral administration of Se 3 to 4 weeks prior to anticipated parturition increased blood concentrations of Se at parturition; however, Se concentrations of both groups at parturition were considered within the reference range for clinically normal cattle.

Effect of injection of beta-carotene or vitamin E and selenium on fertility of lactating dairy cows

Experiments tested whether supplemental antioxidants improved fertility. To test effects of beta-carotene, cows in a hot environment were injected with prostaglandin F2 alpha (PGF2 alpha) and were given 3 injections, i.m., of 800 mg beta-carotene or saline at Days -6 and -3 before the anticipated date of insemination and at insemination (n = 37-41 inseminated cows/group). There was no effect of beta-carotene on the proportion of cows detected in estrus following PGF2 alpha, timing of estrus after PGF2 alpha injection or pregnancy rate in inseminated cows. In a second trial, cows in a temperate climate received intramuscular injections of vitamin E (500 mg) and selenium (50 mg) at 30 d post partum (n = 97) or were untreated controls (n = 89). Treatment did not affect interval from calving to first insemination or the proportion of cows pregnant at first service, but it increased the pregnancy rate at second service (69.8 vs 52.1%; P = 0.07) and reduced services per conception (1.7 vs 2.0; P < 0.05) and interval from calving to conception (84.6 vs 98.1; P < 0.05). Thus, injection of vitamin E and selenium increased fertility in cattle that did not become pregnant at first service.

The use of oxytocin for the reduction of cow placental retention, and subsequent endometritis

Oxytocin was administered to reduce incidence of retained placenta and uterine infections that could delay subsequent conception. Three hundred and fifty multiparous Friesian cows, each with spontaneous delivery of a single calf were divided randomly into two groups. Some (n = 175) were injected with 30 IU of oxytocin immediately after delivery and again 2-4 h later, while the remainder formed an untreated control group. The placental retention 24 h after parturition was 24.6% and 10.9% in control and treated animals respectively (P < 0.01). Endometritis occurred in 51.6% of the animals following placental retention as compared to 10.4% of those with normal expulsion of the fetal membranes (P < 0.001). A comparison of reproductive indices showed a statistically significant improvement of fertility in treated cows with the average interval from calving to conception being reduced from 124.4 d to 93.7 d (P < 0.0001).

Assessment of selenium and vitamin E deficiencies in dairy herds and clinical disease in calves

Because of the very low concentrations of selenium in the dry matter of grass, grass silage, hay and maize silage Slovenian dairy herds need to be supplemented with selenium. Selenium in the form of mineral and feed mixtures maintained adequate mean (sd) blood serum selenium concentrations of 43.9 (27.6) to 65.3 (18.5) micrograms/litre in lactating cows, but in late lactation and in the dry period when only mineral mixtures were used, about 60 per cent of the cows had marginal serum selenium concentrations, mainly because of the low intake of the mineral supplement. In 18 herds which were either unsupplemented or irregularly supplemented with selenium, the mean (sd) concentrations in blood serum were 13.7 (5.5) micrograms/litre and 17.4 (9.2) micrograms/litre, respectively, for selenium and 2.98 (2.72) mg/litre and 1.62 (1.73) mg/litre for vitamin E, indicating that under extensive farming conditions in Slovenia the lack of both micronutrients may be responsible for nutritional muscular dystrophy in calves. Among 37 clinical cases, cardiorespiratory signs predominated in 25 of the calves and skeletal myopathy was dominant in 12. A very low mean serum selenium concentration [9.7 (7.2) micrograms/litre] and typically high activities of aspartate aminotransferase (AST) [1125 (373) U/litre] and creatine kinase (CK) [9169 (3681) U/litre) were observed for the myocardial form of the disease, and 2797 (550) U/litre and 22,650 (13,500) U/litre were observed for the skeletal form of the disease. A highly significant (P < 0.0001) difference in the selenium concentration of liver dry matter between the regularly supplemented [402 (207) micrograms/kg] and irregularly supplemented [173 (69) micrograms/kg] herds was observed. If a minimum value of 300 micrograms/kg of liver dry matter is accepted as the criterion for the determination of adequate selenium status, 93 per cent of the samples from the irregularly supplemented herds were selenium deficient. A similar proportion was estimated to be selenium deficient when the criterion was taken to be 30 micrograms selenium/litre of blood serum.

Effectiveness of short-term cooling and vitamin E for alleviation of infertility induced by heat stress in dairy cows

Four experiments were performed to determine whether cooling cows during final maturation of oocytes and early embryonic development or injection of vitamin E at AI prevented adverse effects of heat stress on pregnancy rates in lactating Holstein dairy cows. In Experiment 1, cows were placed in a cooling facility containing sprinklers and forced ventilation or received shade only from 2 to 3 d before until 5 to 6 d after breeding. Although cooling had no effect on detection of estrus, pregnancy rates were increased slightly for cooled cows (8 of 50 cows; 16.0%) compared with those for cows exposed to shade only (2 of 32 cows; 6.2%). In Experiments 2 through 4, cows were administered 3000 IU of vitamin E or placebo i.m. at AI during two consecutive summers and one winter in Florida. Administration of vitamin E had no consistent beneficial effect on pregnancy rates during summer or winter. Short-term cooling improved pregnancy rates slightly in heat-stressed cows, but administration of vitamin E had no beneficial effects on pregnancy rates during heat stress. Further improvements in cooling schemes during early pregnancy and delineation of antioxidant effects are necessary before such systems become practical for improvement of fertility in heat-stressed dairy cows.

Effect of prepartum injection of vitamin E and selenium on postpartum reproductive function of dairy cattle

A total of 198 cows were randomly assigned to treatment with a single intramuscular injection of 10 ml of a preparation containing vitamin E and selenium or placebo 3 wk before expected parturition. Incidence of retained fetal membranes was 3.0% for the treated group and 10.1% for the control group (P=0.06). Administration of MU-SE also increased the percentage of cows pregnant to the first service (41.2 vs 25.3%; P=0.02), reduced the number of services per conception (2.3 vs 2.8; P=0.03), and reduced the interval from calving to conception (121 vs 141 days; P=0.06). The effect of MU-SE on fertility was apparent in cows with and without retained fetal membranes. There was no effect of MU-SE on the interval from calving to the first estrus. In conclusion, prepartum supplementation with vitamin E and selenium can decrease the incidence of retained fetal membranes, increase pregnancy rates and, thereby, reduce the interval from calving to conception in lactating dairy cows.

Oxidative stress, antioxidants, and animal function

Reactive oxygen metabolites generated during normal metabolism and metabolism stimulated by xenobiotics can enter into reactions that, when uncontrolled, can impair performance of dairy cows. Direct effects include peroxidative changes in membranes and other cellular components. Indirectly, competitive consumption of reducing equivalents can interfere with important metabolic functions and divert glucose from other pathways by inducing the monophosphate shunt. Normally, the body is protected by a wide range of antioxidant systems working in concert. Metal catalysts of oxidative reactions are removed in intracellular fluids by metal-binding macromolecules. Superoxide dismutases, glutathione peroxidase, and catalase within cells remove superoxide and peroxides before they react with metal catalysis to form more reactive species. Finally, peroxidative chain reactions initiated by reactive species that escaped enzymatic degradation are terminated by chain-breaking antioxidants, including water-soluble ascorbate, glutathione, and urate and lipid-soluble vitamin E, ubiquinone, and beta-carotene. To optimize performance, oxidative stress in high producing cows must be controlled by supplying all known antioxidant nutrients and by minimizing effects of substances that stimulate reactive oxygen metabolites.

Recent developments in the roles of vitamins and minerals in reproduction

Vitamins and minerals affect reproductive function. Vitamin A deficiency has long been known to affect reproductive function in cattle. More recently, a role has been proposed for the vitamin A percursor, beta-carotene, in reproductive efficiency. Dietary supplementation with vitamin E and selenium may reduce the incidence of retained placenta, but these nutrients may also affect reproductive function in other ways. Calcium and phosphorus deficiencies affect reproduction in cattle, and vitamin D may directly affect reproductive function in addition to its role in calcium and phosphorus metabolism. Dietary manipulation of a number of other vitamins and minerals also influences reproductive function. However, the specific roles of nutrients in reproductive tissues are not well-defined in dairy cattle, and nutrient requirements for optimal reproductive efficiency in modern dairy cattle deserve careful reevaluation. This review provides a background of the effect of vitamins and minerals on reproduction and it attempts to provide a basis for further investigation of specific mechanisms by which reproductive function is affected. The interface between nutritional science and reproductive physiology provides considerable potential for optimizing reproductive efficiency in dairy cattle.

Responses of dairy cattle to long-term and short-term supplementation with oral selenium and vitamin E1

In a two-lactation-gestation cycle experiment, 152 Holstein cows with low serum Se and vitamin E were fed total mixed rations and assigned at parturition to four groups (1, control; 2, 500 IU vitamin E/d; 3, 2 mg Se/d; 4, 500 IU vitamin E plus 2 mg Se/d). Supplements were not fed during dry periods. Serum Se and vitamin E were increased within 1 mo by oral supplements. Maximal mean serum Se in cycles 1 (67 ng/ml at 7 mo) and 2 (74 ng/ml at 4 mo) occurred in groups 3 and 4, respectively. Maximal mean serum vitamin E in cycle 1 (3.3 micrograms/ml at mo 8) and 2 (3.03 micrograms/ml at mo 2) occurred in groups 4 and 2, respectively. Selenium treatment of the dams increased Se in colostrum and in serum of presuckle calves. Vitamin E supplementation of dams did not affect vitamin E in serum of presuckled calves. Reproductive performance was not affected by supplement. In an 8-wk study, 24 lactating cows with low serum Se were assigned (6/group) to 0, 2.5, 5, and 10 mg supplemental Se/d. Maximal mean serum Se concentrations of 23, 56, 71, and 79 ng/ml were attained by wk 4 in the above respective groups. These data indicate that 2 to 2.5 mg supplemental Se/cow per d were inadequate for desirable serum Se concentrations and support recent changes in allowed Se supplementation for dairy cattle.

Distribution of supplemental selenium in the serum, hair, colostrum, and fetus of parturient dairy cows

A selenium supplementation study was conducted with Holstein cows to evaluate amounts and methods of administration, namely, oral supplementation (1 vs. 2 mg/head/d, last 60 d of gestation) and intramuscular injection (50 mg at 40 and 20 d prepartum vs. 50 mg at 60, 40, and 20 d prepartum). Blood was collected every 10 d, starting 60 d prepartum and extending 20 d postpartum for cows, and at birth to 20 d for calves. Hair samples of cows were obtained at 60 to 40 and 20 d prepartum, and of the calves at birth. Colostrum samples were obtained for assay. Oral (2 mg/d) and both injection treatments resulted in increased selenium in serum of cows, but selenium in serum of calves at birth was greater only for those whose dams received selenium by injection. Selenium in hair of cows was increased by both injection treatments as well as by the oral treatment of 2 mg/d. Selenium in hair of calves was increased by all methods of administering selenium to the dams. Selenium in colostrum was not affected by any treatment. Thus, pregnant dairy cattle respond to selenium supplementations of a daily oral intake of 2 mg/head/d, the last 60 d of gestation, or by injection of 50 mg each on d 40 and 20 prepartum.