The proportionality effect of morphological measurements on brahman young bulls productive performance in pasture

Abstract

This study presents the differences of Average Daily Gain (A.D.G.) in three ranges (high, medium and low) for twenty one morphological indexes generated from the interrelation among the seven corporal measurements taken by Asocebú to the young Brahman bulls in pasture gain test: hip height (HIPHEI), thoracic perimeter (THOPER), body length (BODLEN), rump width (RUMWID), ischium width (ISCWID), rump length (RUMLEN) and testicular circumference (TESCIR). In order to make up each range index, the average was calculated then a standard deviation was added and subtracted to limit the cutting points for each range. The data analysis was made with software SPSS, where a “univariate” variance analysis was made to confirm the absence of effects in the interaction of the zones (Montería, Dorada and Llanos) and ages (nine to twelve and twelve to fifteen months) over the ranges. Later, the A.D.G. averages of the ranges of each index were compared to a Test of Tukey with a level of significance of 0,05. The twelve morphological indexes that presented significant differences in the averages of A.D.G. for the established ranges were: HIPHEI/THOPER, HIPHEI/RUMWID, HIPHEI/ISCWID, HIPHEI/RUMLEN, THOPER/BODLEN, THOPER/RUMWID, BODLEN/RUMWID, BODLEN/ISCWID, ODLEN/RUMLEN, RUMWID/TESCIR, ISCWID /TESCIR and RUMLEN/TESCIR. Those indexes were used for a regression analysis (lineal, quadratic and cubic), generating significant statistical formulas to predict the A.D.G. with the twelve indexes and three types of regression. However, the cubic regression presents determination coefficients higher than the other types of regression (linear and quadratic), where WIPHEI/RUMWID has the lowest prediction error of the dependent variable (A.D.G.) with this cubic formula: A.D.G. = -6.12 + 14.13*(HIPHEI/RUMWID) - 8.81*(HIPHEI/RUMWID)3