Estimation of growth curve parameters in Konya Merino sheep (Short communication)

Abstract

The objective of this study was to determine the fitness of Quadratic, Cubic, Gompertz and Logistic functions to the growth curves of Konya Merino lambs obtained by using monthly records of live weight from birth to 480 days of age. The models were evaluated according to determination coefficient (R 2 ), mean square prediction errors (MSPE) and Durbin Watson (DW) statistics. The R 2 values of the models ranged from 0.96 to 0.99 for females and from 0.96 to 0.99 for males. The Cubic model gave the best R 2 value of 0.99 in females, while the Logistic model gave the lowest R 2 value of 0.96 in females. The results indicated that the Quadratic and Gompertz models showed the best fit to growth of Konya Merino ewe lambs by having higher R 2 values, lower MSPE and non autocorrelation. By using these models live weights at later ages could be predicted from early partial live weight data. Further studies should be carried out on growth curve characteristics at later ages including adult age.________________________________________________________________________________ Increase in live weight or dimension against age has been described as growth. Changes in live weight or dimension for a period of time are explained by the growth curves. Animal breeders are interested in the genotypic and phenotypic relationships during all phases of growth. Knowledge of genotypic and phenotypic relationships among live weights, degree of maturity and growth rate during all phases of growth is necessary to formulate breeding programmes to improve lifetime efficiency (Smith et al., 1976). Growth curves are also used for investigating optimum feeding programmes, determining optimum slaughtering age and the effects of selection on curve parameters and on live weight at a certain age (Blasco & Gomes, 1993).The shape of growth curves has been reported to vary according to the species of animal, the environment and the trait (Efe, 1990;Akbaş et al., 1999;Topal et al., 2004). Moore (1985) studied the growth curves of domesticated mammals. He reported that linear and cubic models fitted the data of cattle, pigs, sheep, goats, rabbits, mice and rats sufficiently, and supplied a standard growth curve for these mammals. Akbaş et al. (1999) studied live weight changes of Kıvırcık and Dağlıç male lambs from birth to 420 days using growth curve models. They reported that the simple linear model gave the best fit for Dağlıç and the quadratic model for Kıvırcık lambs. Also, nonlinear Brody, Negative exponentials, Gompertz, Logistic and Bertalanffy models fitted the body weight data of Kıvırcık and Dağlıç male lambs well (models' R 2 values were above 0.98). Esenbuğa et al. (2000) reported that R 2 values for the Brody model in Morkaraman, Awassi and Tushin lambs were 0.99, 0.99 and 0.98, respectively and the fitness of this model was found to be sufficient. The Gompertz function was found to be appropriate for describing the growth curve of Suffolk sheep (Lewis et al., 2002). Growth from birth to 360 days of age in ewe lambs of the Morkaraman and Awas...

Estimation of growth curve characteristics of Hemsin male and female sheep

“…In both sexes, the highest estimates for the B parameter were found for the Logistic model. Similar findings were reported elsewhere (Akbas et al 1999;Bilgin et al 2004a;Keskin et al 2009). The k parameter still indicates the maturing rate, but the parameter from both types of functions is not precisely the same trait among the models.…”

“…Parameter estimates, their standard errors (SE), coefficient of determination (R 2 ) and residual squared error (RSE) for nonlinear curves describing growth of body weight (kg) by age (months) in male and female of Hemşin male and female sheep. Similarly, Bathaei and Leroy (1998) Karakus et al (2008), Eyduran et al (2008), Keskin et al (2009), andMalhado et al (2009).…”

Mathematical modeling of the native Mexican turkey’s growth

“…Growth curves models can describe and summarize quantitative changes that birds experiment through their lives, they are useful to select Creole birds according to the producer request and to program feeding phases, focusing a large amount of nutrients on the fast growth phases, to know the optimal age to slaughter, effects of gene selection on curve components, and weight gain on a certain age [1][2][3].…”

Descripción del crecimiento de ovinos criollos (Ovis aries) en dos poblaciones de Córdoba, Colombia

“…The figure was done based on the estimated parameters presented in (19), when evaluating the same models in sheep (Dorper×Morada Nova, Dorper × Longtail and Dorper × Santa Inés), found that the Gompertz model was the one that best described growth. Keskin et al (20) found that the Quadratic and Gompertz models were the ones that best described the growth of the sheep when evaluating the Quadratic, Cubic, Gompertz and Logistic models in sheep of the Konya Merino breed.…”