Effects of selenium levels in ewe diets on selenium in milk and the plasma and tissue selenium concentrations of lambs

Abstract

The objective of this 504 day experiment was to evaluate and compare the effects of six levels of dietary selenium (Se) on ewes’ milk and the Se status of their lambs prior to weaning. Sodium selenite was added to a basal diet to provide 0.2 (control), 4, 8, 12, 16, and 20 mg/kg dietary Se for ewes during gestation and lactation over two lambings. Colostrum Se ranged from 257 to 3542 μg/L and increased linearly as dietary Se increased ( P < 0.001) in both years. Ewe milk Se ranged from 75 to 2228 μg/L and also increased linearly as dietary Se increased ( P < 0.01). In general, ewes receiving >12 mg/kg Se produced higher milk Se than controls. Blood samples were collected from lambs before nursing and at 3, 28, and 56 days of age to evaluate plasma Se concentrations. At birth, lamb plasma Se ranged from 74 to 775 μg/L and was affected ( P < 0.001) by the Se concentration of the ewe diets, which indicates placental transfer of Se. Lambs from ewes receiving dietary Se at 20 mg/kg had higher ( P < 0.05) plasma Se than controls at birth and 3, 28, and 56 days of age in both years. Selenium concentration in lamb testes collected at 70 days of age was also affected by Se content of ewe diets. In year 1, lambs whose dams received 16 or 20 mg/kg Se had higher ( P < 0.05) testicular Se than controls, and no differences in testicular Se were observed in year 2. No signs of Se toxicosis were observed in lambs regardless of dietary Se concentration of the ewes’ diet. These results suggest that ewes consuming up to 20 mg/kg inorganic Se may give birth to normal lambs, and that the lambs may not suffer from Se toxicosis before weaning. Selenium as sodium selenite may be fed to ewes at concentrations greater than the current maximum tolerable levels (2 mg/kg) without adversely affecting their offspring.