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Hepatic and Blood Concentrations of Carotene and Vitamin A in Unsupplemented Range Cattle^{1, 2,}

University of Arizona, Tucson

Abstract

Data from essentially unselected bull and heifer progeny of registered Hereford cattle were used to estimate mean concentrations and study genetic and broad environmental sources of variation in hepatic and plasma carotene and vitamin A. These cattle were maintained under ordinary semiarid range conditions. Individual animal weights and samples were obtained at 235, 340, 600 and 710 days of age. Herd size ranged from 280 to 435 cows with 9 to 14 sires per year.

Hepatic carotene levels were significantly higher at weaning and 600 days of age for femal progeny compared to males. There were no significant differences between the sexes at 340 and 710 days. Hepatic vitamin A concentrations were also higher for females at weaning, but levels for the bull progeny were greater at 600 days. No difference between the sexes was detected at 340 or 710 days age. The hepatic vitamin A levels increased with age for all animals.

Heifer progeny had significantly higher concentrations of plasma carotene and vitamin A than did bull progeny at all four ages. Only small differences in concentrations were noted among periods within sex except for the heifers at 710 days, when both carotene and vitamin A concentrations showed a marked increase.

Year-of-birth effects were the most important source of variation considered for the constituents. Age of dam was a significant source of variation only in hepatic and plasma carotene concentrations for male calves at weaning.

Differences in age within sampling period showed their greatest influence at weaning. Weaning concentrations of plasma carotene and vitamin A were influenced in both sexes by age differences. Plasma vitamin A concentration showed significant effects of age differences in both sexes at 600 days.

Heritability estimates of hepatic carotene and vitamin A differed appreciably among sampling periods. Hepatic vitamin A estimates were consistently larger following periods of storage as contrasted to depletion periods. Heritability estimates for plasma carotene concentrations were higher for male progeny and showed greater values after periods of high carotene intake. Estimates for plasma vitamin A concentration showed little evidence of genetic influence.

Simple correlations of hepatic carotene and vitamin A at the four ages with contemporary and subsequent growth traits tend to be low and of little or no predictive value. The simple correlations of plasma carotene and vitamin A concentrations with these traits are highly variable. Male animals do show a tendency for improved performance with higher levels of plasma carotene.

¹ Arizona Agricultural Experiment Station Technical Paper 1297. This study was conducted in cooperation with the U.S.D.A. under Western Regional Project W-1.

² This material was taken from thesis data submitted by the senior author in partial fulfillment of the requirements for the degree of Doctor of Philosophy, University of Arizona, Tucson.

³ Present address: U. S. Range Livestock Experiment Station, Miles City, Montana.