The measurement of chest girth as an alternative to weight determination in the performance recording of meat sheep

Abstract

The aim of this study was to assess, for two Italian meat sheep breeds (Appenninica and Merinizzata italiana), the relationship between an easily recorded measurement (girth of chest) and the character used for selection purposes (weight), and to define the most appropriate mathematical methods to infer the second from the first. For the Appenninica 1392 lambs were measured, for the Merinizzata italiana 1559 lambs were measured. The possibility of estimating weight through chest girth (CG) measurement was evaluated, separately for each breed, by taking the most suitable model between those including different kinds of regression effect. The model was chosen in relation to the value of the determination coefficient and the sum of square residuals. The prediction accuracy of the model was assessed by comparing the expected values with the observed ones through a number of statistical tests. A further prediction analysis was carried out using the mean values of the observed weights that fell in each 1 cm class of girth, in order to reduce the error derived by the varying numbers of observations per unit of chest girth. The model including the square regression nested within the sex effect and the flock random effect nested within the sex effect was observed to be the most suitable one to predict the weight from the chest girth; the determination coefficients ranged between 0.944 (Appenninica) and 0.955 (Merinizzata). The prediction parameters were: -10. ) for the Merinizzata females. The correlation between the observed and expected values was always higher than 0.97. The equations estimated using the mean weights for each girth showed extremely high determination coefficients (= 0.99) due to the reduction of variability implied by this method. Choosing between the equations calculated on the entire data set or on the mean weights will only be possible after a period of field tests.

Analysis of the Non-Genetic Factors Affecting the Growth of Segureño Sheep

“…These data are not only useful in genetic purposes, they are also important to develop economic prognostics and evaluations, and to make prevision on feeding, reproduction and other farming activities. Weight recording is expensive and complex and for this reason some successful alternative has been proposed in meat sheep by using simple characters highly related to the lamb growth (Sarti et al, 2003).…”

Multivariate analysis of morphostructural characteristics in Nigerian indigenous sheep

“…Phenotypic comparison based on morphological characters can provide to an extent a reasonable representation of genetic differences among populations. Body measurement can also be used routinely in weight estimation and selection programmes based on its utility in determining breed evolution trends (Sarti et al, 2003;Riva et al, 2004;Araujo et al, 2006).…”

A comparative study of some estimation methods for parameters and effects of outliers in simple regression model for research on small ruminants

“…), especially when there is no access to weighing equipment. Researchers have used least squares method to determine the best regression model for estimation of body weights from various body measurements in small ruminant researches (Atta and El khidir 2004;Macit and Topal 2004;Singh and Mishra 2004;Sarti et al 2003;Mohammed and Amin 1997;Benyi 1997;Sulieman et al 1990). These authors concluded that the model including chest girth was the best regression model.…”