Hepatic vitamin A concentrations in sheep in north-western Queensland

Abstract

The vitamin A concentrations were determined on livers taken from wether sheep one to five years old grazing Mitchell grass downs in north-western Queensland. The animals were slaughtered for rations at intervals of two weeks. The mean value over a three-year period for the 123 sheep examined was 260.3 ¦ SD 128.3 ¦g/g, which is considered normal ; at no time were values less than 48 ¦g/g. Subsequent results were obtained from a further 199 young sheep slaughtered at monthly intervals between the ages of 15 to 64 weeks. The concentration of vitamin A ranged from 40.4 ¦ SD 41.3 ¦g/g at 29 weeks to 265 -¦ SD 97.1 ¦g/g at 60 weeks. In the adult sheep there did not appear to be any relationship between concentration and rainfall, whereas in individual young sheep low values coincided with extended periods of no rainfall. A clinical deficiency of vitamin A in young sheep could be expected if the length of a drought exceeds approximately seven months.