Adequacy of trace minerals in bovine milk for human consumption

Ultrasensitive detection of glucose oxidase and alkaline phosphatase in milk based on valence regulated upconversion nanoprobes

Fresh milk should undergo sterilization before consumption to eliminate bacteria that can cause foodborne illnesses. Additional antimicrobial measures are beneficial to extend its shelf life. The nanoprobe developed herein can not only inspect the activity of alkaline phosphatase (ALP) for evaluating the degree of pasteurization, but also detect the activity of glucose oxidase (GOD), which is added as a chemical preservative. The facile preparation of the nanoprobe involved introducing gallic acid-Fe complex (GA-Fe) into lanthanide doped upconversion nanomaterials (UCNPs). Based on the alteration of iron's valence state in the complex through a straightforward redox reaction, both enzyme activities could be determined through colorimetric and luminometric dual-signal readouts. With detection limits of 1.669 × 10-5 for GOD and 9.81 × 10-6 U/mL for ALP respectively, this nanoprobe shows merits of easy operation and high sensitivity. Successful application in milk samples demonstrates its potential as an innovative and cost-effective approach to food safety inspection.

Relationship of dietary selenium to selenium in plasma and milk from dairy cows

In a 13-wk trial Holstein cows in mid-lactation were fed four diets containing natural selenium alone or supplemented with .1, .2, or .5 mg of inorganic selenium per kilogram of diet. Dietary selenium concentration averaged .334, .385, .456, and .772 mg/kg. Selenium plasma in wk 7 averaged .112 mu/ml with no differences among treatments; milk selenium ranged from .040 to .046 mu/ml and was higher in the two higher selenium diets. In wk 13 selenium in plasma and milk averaged .119 and .054 with no treatment differences. The 7 and 13 wk concentrations were higher than pretrial .084 and .033 mu/ml for plasma and milk during which time dietary selenium concentration was .254 mg/kg. Selenium concentration increased linearly from about .08 to .120 mu/ml of plasma and about .030 to .055 mu/ml of milk as intake of selenium increased from about 2 to 6 mg/day. Increase in selenium intake from 6 to 12 mg/day resulted in little change in plasma and milk selenium. Moderate concentrations of dietary selenium (.3 to .7 mg/kg) do not result in toxic amounts of selenium in milk.

The nutritional and physiological impact of milk in human nutrition

The nutritional value of milk as an important source of energy, high-quality protein, calcium, and riboflavin has been recognized for many years. Currently, the widespread use and promotion of milk in the U.S. as well as developing countries has been questioned. This review examines the nutrient composition of dairy products, factors that account for variability in composition of milk, milk processing, preservation, quality control, and contaminants (such as minerals, radionuclides antibiotics, microorganisms and their metabolites, herbicides, and insecticides) in milk. Consumption patterns for milk and evidence for its nutritional value, especially in children, are presented. Milk consumption has been related to disease or conditions such as atherosclerosis, milk allergy, lactose intolerance, anemia, dental problems, and others. Recent recommendations for dietary changes for individuals in the U.S. and other developed countries could affect the use of milk. In addition, the use of feeding programs in the U.S. and developing countries which are based primarily on milk has been criticized. The preparation of new types of milk designed to offset certain difficulties encountered with cow's milk are now being evaluated in humans.

Selenium in ruminant nutrition: a review

The early interest in selenium related primarily to its toxicity, but since 1957 the element has been recognized as a dietary essential. The dietary requirement for selenium by most species is about .1 ppm. Deficiencies of selenium in cattle and sheep have been confirmed under natural grazing conditions in many countries of the world. Overt signs of inadequacy such as white muscle disease (nutritional muscular dystrophy) occur primarily in young calves or lambs born to selenium deficient dams. Infertility has increased in ewes grazing pastures low in selenium. In general, signs of deficiency have not occurred in older animals such as finishing beef cattle and lactating dairy cows. Subclinical deficiencies of selenium are not determined easily, however, and thus an inadequacy of the element may be limiting maximum animal performance under certain circumstances of drylot feeding. The current nutritional status of ruminant animals in many geographical areas and involving various feeding programs with this element has not been established. The recent widespread deficiency problems with nonruminants suggest that such an assessment should be made. Concentration of selenium in tissue, particularly in the liver, has been used in establishing selenium status of the animal. With lambs glutathione peroxidase activity in certain tissues may be a more accurate indicator of selenium adequacy than is selenium content of the tissue. Supplemental sodium selenite and sodium selenate by either oral administration or parenteral injection have prevented clinical signs of selenium deficiency and animal losses in both ruminant and nonruminant animals. Heavy pellets containing elemental selenium for placement in the rumen have proved effective. In general, organic forms of selenium are absorbed more readily by animals than are inorganic compounds. The dietary requirements for selenium and its metabolism are influenced by many nutrient interrelationships, including its interactions with sulfur, lipids, vitamin E, proteins, amino acids, and several microelements. The Food and Drug Administration gave approval in 1974 for the oral administration of supplemental selenium as either sodium selenite or sodium selenate to certain classes of swine and poultry. Similar approval in the United States for ruminants will require additional information, particularly with regard to the influence of dietary intake on concentrations of selenium in tissue and milk in beef and dairy animals.