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.

Enhanced reproductive performance of ewes given a sustained-release multi-trace element/vitamin ruminal bolus.

A sustained-release multi-trace element/vitamin bolus has been devised for administration to ewes in advance of mating. Each bolus contained 5.3g Cu, 50mg Se, 90mg Co, 100mg I, 3.2g Mn and 4.7g Zn with 268x10(3) IU Vitamin A, 54x10(3) IU Vitamin D and 800 IU Vitamin E. About 50% of each nutrient is released during the first 6 weeks. Thereafter the release rate slows and over the remaining life of the bolus (about 6 months extending to lambing time) the daily release rates are about 15mg Cu, 0.1mg Se, 0.2mg Co, 0.3mg I, 9.4mg Mn and 13mg Zn with 775 IU Vitamin A, 156 IU Vitamin D and 2 IU Vitamin E. In one study the proportion of twins born to ewes given the bolus was very significantly (P<0.001) higher than for the untreated ewes and greater than for those given a copper injection or copper oxide needles. In a second study the proportion of ewes given a bolus and having twin lambs was significantly (P<0.01) greater than for untreated ewes and significantly (P<0.05) fewer ewes were non-pregnant. In a third study, giving a bolus to shearling ewes tended (P=0.06) to result in fewer non-pregnant animals than for those untreated. Blood copper and Vitamin B(12) concentrations and glutathione peroxidase activities were above normal values throughout.

The influences of dietary selenium and vitamin E intakes on milk somatic cell counts and mastitis in cows.

Dietary supplements of selenium and vitamin E in greater amounts than are required for nutritional adequacy can have complementary functions in reducing somatic cell counts and both the severity and duration of clinical mastitis. Selenium inadequacy is geographically widespread and can frequently be a year-round problem. In contrast, an adequate intake of fresh grass and quality grass silage or other green, leafy material should provide adequate vitamin E. Many observations indicate that in farm situations where there is good udder hygiene and where long-acting antibiotic treatment is given at drying off, significant correlations are found between the mean bulk milk somatic cell counts and the blood selenium concentration or glutathione peroxidase activity in the blood, even where plasma vitamin E concentration is fully adequate. The accompanying reduced incidence of clinically affected quarters diminishes the need for corrective antibiotic treatment during lactation. Presentation of selenium and vitamin E within a sustained-release rumen bolus system during the dry period and into the succeeding lactation is a convenient means of supplementation to avoid over- or under-consumption by individual cows within a group. Adequate hygiene of the environment, the milking equipment and the udder are essential.

Sustained-release boluses to supply trace elements and vitamins to calves.

Cylindrical rumen boluses of a size (55 mm length x 18 mm diameter, density 2.9 g cm(-3)) appropriate for ruminating calves over 75 kg liveweight were constructed. The mean daily nutrient releases from two rumen boluses measured in rumen-cannulated cows were 62 mg Cu, 0.56 mg Se, 1.08 mg Co, 1.14 mg I, 38 mg Mn and 55 mg Zn with vitamins 3140 IU A, 628 IU D3 and 9 IU E. In a 123-day experiment with housed dairy calves given hay and a barley/soyabean meal mix, administration of two rumen boluses significantly increased plasma copper and blood glutathione peroxidase levels compared with unsupplemented control calves. There were similarly significant responses in a 143-day experiment with suckled beef-cross calves treated with two rumen boluses at grass. In both circumstances the basic diets provided inadequate allowances of both copper and selenium.

The effectiveness of copper oxide powder as a component of a sustained-release multi-trace element and vitamin rumen bolus system for cattle.

Copper oxide powder administered in the form of two experimentally produced sustained-release rumen boluses significantly increased blood and liver copper concentrations in growing sheep. It was estimated that 7% of the copper released was stored in the liver. In two farm observation trials administration of two standard production boluses significantly increased blood copper concentrations in out-wintered suckler cows during late pregnancy and early lactation, and in growing cattle at grass in the summer over periods of at least 170 and 123 days, respectively.

Low phosphorus intakes by beef suckler cows in late pregnancy and early lactation.

Two groups each of 10 suckler cows were given a basal diet of oat straw and pressed unmolassed sugar beet pulp for the last 19 weeks of pregnancy and the first 6 weeks of lactation. One group received 0.88 kg extracted soya bean meal (SBM) in pregnancy and 1.03 kg in lactation. The other was given 0.27 kg of a liquid supplement (LS) (containing inter alia urea and phosphoric acid) in pregnancy increasing to 0.33 kg in lactation. Both diets provided about the same amounts of digestible crude protein and about 10 g phosphorus (P) per day in pregnancy and 12 g P per day in lactation. Cows given SBM consumed marginally more straw but there were no differences in total diet digestibility. Cows given LS lost significantly more liveweight but their calves grew equally well. There were indications that cows given LS had slightly higher mean blood inorganic P and lower mean blood calcium (Ca) concentrations. Mean blood inorganic P concentrations were not below 1.4 mmol/l in pregnancy or 1.2 in lactation. There were no signs of reduction in voluntary straw intake or depraved appetite. When transferred to grass with a bull at the end of the experiment all cows were served within 24 days. It is concluded that these amounts of dietary P were adequate over the 25 weeks.