SERUM ALPHA-TOCOPHEROL, VITAMIN-A, AND BLOOD SELENIUM CONCENTRATIONS,AND GLUTATHIONE-PEROXIDASE ACTIVITY IN LLAMAS FED ALFALFA HAY

Objectives-To measure blood selenium concentration and glutathione per oxidase (GSH-Px) activity and serum concentrations of vitamin A and al pha-tocopherol, and to determine the correlation between blood seleniu m concentration and GSH-Px activity of llamas fed alfalfa hay. Design- Mean (+/- SD) serum vitamin A and alpha-tocopherol concentrations, blo od selenium concentrations, and GSH-Px activity were calculated from 9 sequential blood samples collected from llamas fed a diet of alfalfa hay. Animals-15 clinically normal llamas (8 males, 7 females) between 10 and 14 months of age. Procedure-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 activi ty was measured with a spectrophotometer, using a modification of a pr eviously described assay. Isocratic high-performance liquid chromatogr aphy with florescent detection was used to determine serum alpha-tocop herol and vitamin A concentrations. Results-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 ia SD) blood selenium concentration and GSH-Px activity were 0.179 +/- 0.032 mu g/ml and 25.76 +/- 6.53 mU NADPH oxid ized/min/mg of Hb, respectively, with a correlation coefficient of 0.9 7. The mean (+/- SD) concentrations for serum a-tocopherol and vitamin A were 128.1 +/- 41.7 and 74.8 +/- 5.5 mu g/dl, respectively. Conclus ions-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 concentrati ons of vitamin A precursors and vitamin E in the hay were below curren tly recommended dietary levels for llamas, and alfalfa hay appears to provide an unreliable source of vitamins A and E in this species. Furt her studies are required to determine optimal dietary concentrations a nd to substantiate a reference range for these vitamins in llamas.