Abstract
ABSTRACTIn order to describe the growth curves in Iranian Mehraban sheep, five non-linear mathematical equations (Brody, Negative exponential, Logistic, Gompertz and Von Bertalanffy) were used. The data set used in this study was obtained from the Agricultural Organization of Hamedan province and comprised 35,414 weight records of lambs which were collected from birth to 365 days of age during 1991–2011. Each model was fitted separately to body weight records of all lambs, male and female lambs and single and twin lambs using the NLIN and MODEL procedures in SAS. The models were tested for goodness of fit using adjusted coefficient of determination ( ), root mean square error (RMSE), Durbin–Watson statistic (DW), Akaike’s information criterion (AIC) and Bayesian information criterion (BIC). The Brody model provided the best fit of growth curve in all lambs, male and female lambs and single and twin lambs due to the lower values of AIC and BIC than other models. The Logistic model provided the worst fit of growth curve for all lambs, male and female lambs and single and twin lambs. Evaluation of different growth equations used in this study indicated the potential of the non-linear functions for fitting body weight records of Mehraban sheep.
Highlights
Throughout the drier regions of Africa, Middle East and Asia, sheep is a major livestock resource (Hamoudaa and Atti 2011)
The Brody model provided the best fit of growth curve in all lambs, male and female lambs and single and twin lambs due to the lower values of Akaike’s information criterion (AIC) and Bayesian information criterion (BIC) than other models
The Logistic model provided the worst fit of growth curve for all lambs, male and female lambs and single and twin lambs
Summary
Throughout the drier regions of Africa, Middle East and Asia, sheep is a major livestock resource (Hamoudaa and Atti 2011). In 2007, the sheep population in Iran reached 25 million heads (Ghafouri-Kesbi 2013). This large population is mainly reared for meat production to provide a part of the protein requirements of a population of 75 million people (Ghafouri-Kesbi 2013). Mehraban sheep is one of the important Iranian sheep breeds. This breed of sheep originates from the western province of Iran known as Hamedan and is adapted to harsh and rocky environments. The Mehraban (approximately three million heads) is the predominant breed in this province, reared primarily for meat production (Yavarifard et al 2016). Mehraban sheep is a fat-tailed carpet wool sheep with light brown, cream or grey colour, along with a dark face and neck (Yavarifard et al 2016)
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