Modeling the growth curve of Iranian Shall sheep using non-linear growth models

In 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...

https://tandfonline.com/doi/pdf/10.1080/09712119.2017.1348949

Comparison of non-linear growth models to describe the growth curve of Mehraban sheep

In the present study, we examined the suitability of seven asymptotic nonlinear models to describe body weight growth of Hemsin male and female sheep from birth to 36 months of age and, using the selected functions, to provide a biological interpretation for this growth. The weight–age data for this study were obtained from records of 108 Hemsin female and male sheep held in variety breeder flocks of Artvin province in Turkey. The sheep records were collected between 2008 and 2010 with measurements taken at birth, 2nd, 3rd, 6th, 12th, 18th, 24th, and 36th months of age. Body weight–age data from Hemsin sheep were used to obtain a growth pattern for sheep, with the use of Negative exponential, Brody, Gompertz, Logistic, Bertalanffy, Richards, and Janoschek nonlinear functions. Comparisons between these functions were based on coefficients of determination and residual squared error. The R2 values of the models ranged from 0.971 to 0.989 for males and from 0.951 to 0.991 for males. In both sexes, the Brody,...

Estimation of growth curve characteristics of Hemsin male and female sheep

Modeling the growth curve in Kordi sheep: The comparison of non-linear models and estimation of genetic parameters for the growth curve traits

Studying genetic parameters and genetic changes in Santa Ines sheep is important, because it is the commonest breed in Brazil. This study obtained genetic data from 37,735 pedigree records of lambs over 12 years (2003-2014) from 33 flocks in 10 Brazilian States; 11,851 records of performance were available. (Co)variance components, genetic parameters and breeding values estimates were obtained by derivative-free restricted maximum likelihood in a univariate analysis that included maternal additive genetic and maternal permanent environmental effects. Birth weight, weaning weight, weight at 180 days of age, weight at 270 days of age, average daily weight gain in the following states: from birth to weaning, from weaning to 6 months, from 6 months to 9 months, and from weaning to 9 months; presence of hair in fur and leg muscularity were assessed. (Co)variance component values increased in the weight traits with age. A significant maternal effect was found in the pre-weaned stage that decreased in the post-weaned stage. High values were estimated for the maternal permanent environmental effect, possibly because of the extensive grassland that was available. High total heritability values were estimated for all of the traits evaluated. Significant, positive correlations were found between direct and maternal additive genetic traits with a gradual decrease as the lambs gained independence from their mothers. The genetic trends observed were irregular and incremental. Significant genetic variance suggests that direct selection for pre-weaning traits results in indirect selection of maternal abilities, and individual selection of any post-weaning trait results in rapid genetic improvement.

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Laíza Sofia Acioli da Silva

Papers

Growth curve in Santa Inês sheep