The Gompertz curve or Gompertz function is a type of mathematical model for a time series , named after Benjamin Gompertz — It is a sigmoid function which describes growth as being slowest at the start and end of a given time period. The right-hand or future value asymptote of the function is approached much more gradually by the curve than the left-hand or lower valued asymptote. This is in contrast to the simple logistic function in which both asymptotes are approached by the curve symmetrically.

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Estimation of model parameters of the Japanese quail growth curve using Gompertz model. Raji, A. University of Maiduguri. This study was conducted to describe the growth pattern of Japanese quails with the Gompertz growth model using body weight measurements from an unselected, random bred quail population. The coefficient of determination R 2 was high for both male and female 0.

However, male and female Japanese quails did not have identical growth patterns. Generally, females appeared to be heavier than males at all ages and this difference increased with age. Thus, males matured faster than females though the latter had higher weights. Thus, a strong and negative relationship Age, weight and maximum gain at point of inflection for male and female Japanese quails were 2. Similarly, they had lower inflection weight and gain than female quail.

And it explains difference between males and females Japanese quail in Nigeria. Sin embargo, los modelos de crecimiento de las codornices machos y hembras, no son iguales. Ello explica las diferencias entre codornices japonesas machos y hembras en Nigeria. Palabras clave: Coeficiente de madurez. It also offers an excellent opportunity for poultry farmers to enter a new and profitable poultry business especially in Nigeria where it was only recently introduced. In addition to its lean meat, the egg is lower in cholesterol as compared to chicken Musa et al.

They are, particularly, important for egg production in Japan and South East Asia and meat production in Europe Minvielle, Growth curves are useful tools representing the evolution of body weight during growth and are particularly important in breeding and management.

In addition, curve parameters provide information on growth characteristics. Ricklefs pointed out that the purpose of curve fitting is to describe the course of mass increase with age by simple equations with few parameters. Growth curves can be used for pre-selection of animals as it provides prediction of future growth at any age. Brody suggested that the asymptotic or mature weight, rate of attainment of mature weight and the standardized age at which an animal attained the inflection point of the curve are parameters that could be manipulated by geneticists.

Different mathematical growth models have been used to define growth curves. The most commonly used functions to estimate animal's growth have three to four parameters. Ratkowsky observed that these curves start at some fixed point, growth rate then increases up to an inflection point after which it decreases asymptotically to a final value.

The growth of most galliforms including poultry conforms closely to the shape of the Gompertz. It is a three parameter growth function with a smooth sigmoid behavior and fixed point of inflection that has been cited as the model of choice for poultry data because of its overall fit and biological meaning of the model parameters Anthony et al.

The three parameters of the Gompertz growth model are defined as asymptotic weight A , integration constant B and rate of maturity k Akbas and Oguz, Kniztova et al.

In addition, Mendes observed that the Gompertz model had better fit to weight-age, shank width-age, shank length-age, body length-age data than other models. Similarly, Narinc et al. Wiseman and Lewis also employed the Gompertz to study the patterns of growth of live weight and carcass components in broilers. Since the Gompertz model generally fits the growth of many mammals and chickens Hurwitz et al.

Maiduguri, the Borno State capital is situated on latitude 11 o 5' N, longitude 13 o 09' E and at an altitude of m above sea level. The area falls within the Sahelian region of West Africa, which is noted for great climatic and seasonal variations. It has very short period months of rainfall of Day length varies from 11 to 12 hours.

One hundred and twenty one 54 male and 67 females Japanese quails hatched from eggs collected from unselected and random mating parents were used for the study. After hatching, the chicks were individually weighed and labeled before brooding for two weeks. The birds were housed at three weeks in cages 30x30x45 cm; with 2 birds per cage and had free access to feed and water.

Birds were weighed weekly from week 0 to week The Gompertz model was fitted to the quail growth data using Levenberg-Marquardt nonlinear least-squares algorithm in Statistix 9. The Gompertz non linear model fitted to the body weight data was described by Ricklefs as:.

Weight and age at the inflection point POI were calculated as:. Descriptive statistics and degree of maturity for body weights at different ages of male and female Japanese quails are presented in table I. Similarly, the SD also increased with age as is common with time series data Aggrey ; Nahashon et al. Many authors also reported that sexual dimorphism was in favour of females in the Japanese quail Aggrey and Cheng, ; Aggrey et al.

They observed that male and female Japanese quails do not have identical growth patterns as is evident in figure 1. They however over and under estimated early weights weeks of the quails with little difference between observed and predicted weights thereafter. This also agrees with the reports of Brown et al.

Thus, males matured faster than females though the latter had higher mature weight. This result may be important in determining the length of commercial breeding for meat in the Japanese quail. It may also indicate the period of collection of growth data for analysis. Estimated coefficients for the Gompertz model parameters of the Japanese quail are presented in table II. This implies that the growth curves of the observed data were adequately described by the Gompertz function.

This agrees with the reports of Akbas and Oguz and Balcioglu et al. Asymptotic weight A was higher in females Differences in A between genders have been reported in the Japanese quail Akbas and Oguz, ; Aggrey et al. The asymptotic weights for male and female Japanese quail in this study were lower than However, Narinc et al.

Thus, quails fed in different environment and have different genotype will have different asymptotic weight. Asymptotic weights from different studies should therefore be compared with caution. Higher asymptotic weight in females has also been reported in the pearl gray guinea fowl Nahashon etal. It was however higher for males in chicken Aggrey, Like the asymptote weight, B parameter integration constant which is related to initial weight hatch weight was higher in females than males.

These authors reported higher values for males than females. However, parameter k maturation or growth rate was higher in males 0. Parameter k indicates the rate of maturity and high values imply shorter periods of growth early maturity and lower mature weights. Thus, male quails grew faster than females and reached their weight at point of inflection and asymptotic weight at a younger age.

The estimates of correlation Thus, there seems to be an antagonistic relationship between asymptotic weight and growth rate since females with higher asymptotic weight had lower growth rate and were late maturing while the reverse was observed with males.

Similarly, the inflection weight and maximum gain was higher for female quails than males. In this study, females reached inflection age three days later than males. Du Preez and Sales reported that this delay was likely to arise from the higher asymptotic value and consequently the longer growth period. However, the inflection age weeks and weight grams reported for male and females respectively, in this study were lower than 2.

The higher values reported in these studies could be because the authors obtained higher asymptotic weights for quails in their respective studies. The Gompertz model adequately described the growth of both male and female Japanese quails though the pattern of growth differed.

Male and female Japanese quails had almost attained their mature weights at 12 weeks of age. The males matured much earlier than females, but had lower asymptotic weights and gain at inflection point. Finally, understanding the growth pattern of the Japanese quail will contribute to efforts at improving this species in Nigeria. Aggrey, S. Comparison of three non-linear and spline regression models for describing chicken growth curves. Poultry Sci , Effect of long-term divergent selection on growth characteristics in Japanese quail.

Animal model analysis of genetic co variance of growth traits in Japanese quail. Akbas, Y. Growth curve parameters of lines of Japanese quail Coturnix coturnix japonica , unselected and selected for four-week body weight.

Arch Geflugelkd , Heritability estimates of growth curve parameters and genetic correlations between the growth curve parameters and weights at different age of Japanese quail. Anthony, N.

Comparison of growth curves of weight selected populations of turkeys, quail and chickens. Analysis of growth characteristics in short-term divergently selected Japanese quail. S Afr J Anim Sci , Bertalanffy, L. Quantitative laws in metabolism and growth. Q Rev Biol , Brody, S. Bioenergetics and Growth.


Gompertz function








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