Relative bioavailability of zinc using weight gain of rats

Weanling rats were fed semi-purified diets with varying zinc levels in order to derive new measures of relative bioavailability of zinc (RBAZ). The various measures for RBAZ were slope-ratio assays of weight gain, total liver zinc and total femur zinc along with five alternative measures developed from sigmoidal curves for weight gain estimated by a non-linear, least-squares curve fitting computer program. The slopes of weight gains explained a higher proportion of the true measure than similar slopes of femurs or livers as indicated by R2. The 95% confidence intervals of ratios were narrowest for weight gain assays. Four of the five alternative methods had RBAZ similar to the RBAZ of slope-ratio weight gain assays. These new methods provided a diversity of information and allowed more information to be obtained than from slope-ratio assays alone.