Serum alpha-tocopherol, vitamin A, and blood selenium concentrations, and glutathione peroxidase activity in llamas...

To measure blood selenium concentration and glutathione peroxidase (GSH-Px) activity and serum concentrations of vitamin A and alpha-tocopherol, and to determine the correlation between blood selenium concentration and GSH-Px activity of llamas fed alfalfa hay.

Mean (+/- SD) serum vitamin A and alpha-tocopherol concentrations, blood selenium concentrations, and GSH-Px activity were calculated from 9 sequential blood samples collected from llamas fed a diet of alfalfa hay.

15 clinically normal llamas (8 males, 7 females) between 10 and 14 months of age.

Llamas were fed alfalfa hay for 40 days prior to sample collection and then for the duration of the trial. Vitamin E, selenium, and concentrations of vitamin A precursors were measured in the hay. Blood samples were collected on days 0, 6, 7, 9, 13, 20, 42, 64, and 98. Blood selenium concentrations were measured, using an inductively coupled spectrometric method. Blood GSH-Px activity was measured with a spectrophotometer, using a modification of a previously described assay. Isocratic high-performance liquid chromatography with florescent detection was used to determine serum alpha-tocopherol and vitamin A concentrations.

The alfalfa hay contained 0.2 mg/kg of selenium, 5 mg/kg of vitamin E, and 0.9 mg/kg of vitamin A precursors. The mean (+/- SD) blood selenium concentration and GSH-Px activity were 0.179 +/- 0.032 micrograms/ml and 25.76 +/- 6.53 mU NADPH oxidized/min/mg of Hb, respectively, with a correlation coefficient of 0.97. The mean (+/- SD) concentrations for serum alpha-tocopherol and vitamin A were 128.1 +/- 41.7 and 74.8 +/- 5.5 micrograms/dl, respectively.

Blood selenium concentrations in llamas are highly correlated to GSH-Px activity. Blood selenium concentrations in llamas appear to be similar to other domestic ruminants and diets containing 0.2 mg/kg of selenium appear to provide an adequate dietary source. The concentrations of vitamin A precursors and vitamin E in the hay were below currently recommended dietary levels for llamas, and alfalfa hay appears to provide an unreliable source of vitamins A and E in this species. Further studies are required to determine optimal dietary concentrations and to substantiate a reference range for these vitamins in llamas.