Impact of models and frequency of measuring on describing body measurement-age relationship in sheep

Abstract

Linear, quadratic and Brody growth models were used to fit body measurement-age data for 8 Rahmani male sheep. Comparisons were also made among these models for goodness of fit using R2, residual variance and Cp statistics. The residual variance and Cp criterion were judged to be more informative than R2 for selection between growth models. The Brody model gave the best fit for height at withers, chest girth and length of body measurements based on Cp criterion. The comparisons between the various recording schedules revealed that, if any practical application of measurement-age model characteristics is possible, the measurements must be obtained at monthly intervals especially at early ages, and at 3-month intervals thereafter until maturity.