Comparison of non-linear models to describe growth of Iranian Guilan sheep

Abstract

SummaryBackground: non-linear mathematical models, empirically developed by plotting body weight against age, are used to describe the growth curve in different animals. Objective: to describe the growth pattern in Guilan sheep using non-linear models. Methods: six non-linear mathematical equations (Brody, Negative exponential, Logistic, Gompertz, von Bertalanffy and Richards) were used to describe the growth curves in Guilan sheep. The Agricultural Organization of Guilan province (Rasht, Iran) provided the dataset used in this study. The dataset included 42,257 weight records of lambs from birth to 240 days of age during years 1994 to 2014. Each model was separately fitted to body weight records of all lambs, males and females, using the NLIN and MODEL procedures of SAS. The models were tested for goodness of fit using adjusted coefficient of determination, root means square error (RMSE), Durbin-Watson statistic, akaike's information criterion (AIC) and bayesian information criterion (BIC). Results: the Richards model provided the best fit to the growth curve in females and all lambs, with the lowest RMSE, AIC, and BIC values compared to the other models. The Brody model provided the best fit of growth in male lambs due to the lower values of AIC and BIC compared to the other models. The negative exponential model provided the worst fit of growth for males, females and all lambs. Conclusion: the evaluation of the growth equations used in this study indicates the potential of non-linear functions for fitting body weight records of Guilan sheep.

Definición de curvas de crecimiento con modelos no lineales en borregas de siete razas con registro de pureza en México

“…La TAC se refiere a la rapidez de crecimiento relativo al PAD; con TAC altas se alcanza el PAD a menor edad. La velocidad de crecimiento es económicamente importante porque se puede usar para determinar el momento óptimo del sacrificio, una vez que el animal haya alcanzado la velocidad de crecimiento máxima (13,21) .…”

“…Los análisis se realizaron con el método de Gauss-Newton del procedimiento NLIN del programa para análisis estadístico SAS (10) ; la selección del modelo con mejor ajuste se realizó en función de (11,12,13) . Donde: pvi = peso vivo (kg) en la iésima edad (d); pei = peso vivo (kg) estimado para la iésima edad (d); n = número total de datos; sce = suma de cuadrados del error; sct = suma de cuadrados total; k = número de parámetros en el modelo; ln = logaritmo natural.…”

Genetic analysis of body weight and growth curve parameters in Muzaffarnagari sheep of India

“…The maturing rate parameter k is an indicator of relative growth rate, such that animals with high k-values mature more quickly than those with lower kvalues and similar initial weights (Mandal et al, 2021). Greater values of k for females indicated more rapid maturing rates and were also reported in other sheep breeds (Ganesan et al, 2015;Ghavi Hossein-Zadeh & Golshani, 2016;Hojjati & Ghavi Hossein-Zadeh, 2018;Kopuzlu et al, 2014).…”

Early Growth Model of Pelibuey Lambs Raised Under an Intensive Production System in Colima, Mexico

“…Growth is best described by the sigmoidal relationship between age and body weight (Lupi et al, 2015). In this sense, the most widely used methods to describe weight are the Brody, Gompertz and Logistic models (Waheed et al, 2016;Hojjati and Hossein-Zadeh, 2018;Hossein-Zadeh and Golshani, 2016) since they provide a set of mathematical and biological parameters that are used to fit growth curves, describe growth pattern over time, and estimate the expected weight of the animal at specific ages.…”

“…Biological growth is defined as the weight gain of an animal until it reaches adulthood, whereas commercial growth is the weight gain during the period comprised between birth and slaughter (Lupi et al, 2015). Analysis of growth curves and parameters through biological and commercial life span is helpful to improve feeding strategies, select the best replacement lambs, and establish the best age for matting and slaughtering (Lupi et al, 2015;Waheed et al, 2016;Hojjati and Hossein-Zadeh, 2018;Hossein-Zadeh and Golshani, 2016). Therefore, the objective of this study was to describe the early growth of Pelibuey lambs raised under an intensive production system in Colima, Mexico, using non-linear models.…”