The description of the growth of the Japanese quails is necessary to characterize the genetic potential of these birds raised in different countries. Thus, the aim of this study was to describe the genetic potential of Japanese quails by conducting a meta-analysis considering studies conducted in different countries. Only data about the subspecies Coturnix coturnix japonica were considered; studies regarding Coturnix coturnix coturnix were not examined. The criteria investigated were BW (W), age (t), year of publication and location of the study. Each set of genetic material within a publication was coded as one study. The Gompertz function was used to interpret the growth of laying quails; thus, each study was represented by Gompertz parameters. The W and t data were applied to estimate the values of Gompertz growth parameters, including BW at maturity (Wm), BW at birth (Wi), maturity rate (B) and inflection point (IP). The age at which the maximum growth rate was achieved (t*) was calculated considering the parameters Wm, Wi and B. To estimate these parameters, random regression was used to randomize the parameter Wm. The parameters estimated for each assay were used in exploratory, grouping, and principal component analyses. The values of Wi ranged from 4.1 to 11.6 g. The values of B ranged from 0.0393 to 0.1039/day, and consequently, the values of t* and IP ranged from 14 to 31 days and 9.21 to 31.03 g, respectively. These results show that there is considerable variability in the growth potential of Japanese quails. To better understand this variation, two groups were examined: Brazil and other countries, according to the grouping of Wi, Wm, B and t*; parameter B was the variable that presented the highest specificity, indicating that both groups modified the maturity rate. For the principal component analysis, the year of publication showed a relationship with the growth parameters but only for studies performed in Brazil. For studies carried out in other countries, the changes in growth parameters were not related to the year of publication. In Brazilian studies, there was a decrease in the maturity rate, but the weight at maturity was higher. Therefore, it appears that different strategies of genetic selection were adopted in Brazil compared to other countries.

Corn poppy is the most abundant broad-leaved weed in winter cereals of Mediterranean climate areas and causes important yield losses in wheat. Knowledge of the temporal pattern of emergence will contribute to optimize the timing of control measures, thus maximizing efficacy. The objectives of this research were to develop an emergence model on the basis of soil thermal time and validate it in several localities across Spain. To develop the model, monitoring of seedling emergence was performed weekly during the growing season in a cereal field located in northeastern Spain, during 3 yr. Cumulative thermal time from sowing date was used as the independent variable for predicting cumulative emergence. The Gompertz model was fitted to the data set of emergences. A base temperature of 1.0 C was estimated through iteration for maximum fit. The model accounted for 91% of the variation observed. Model validation in several localities and years showed general good performance in predicting corn poppy seedling emergence ( values ranging from 0.64 to 0.99 and root-mean-square error from 4.4 to 24.3). Ninety percent emergence was accurately predicted in most localities. Results showed that the model performs with greater reliability when significant rainfall (10 mm) occurs within 10 d after crop sowing. Complemented with in-field scouting, it may be a useful tool to better timing control measures in areas that are homogeneous enough regarding climate and crop management.

Genealogical and live body weight monthly records from 790 sheep of the Chiapas breed born between 1991 and 2004 were used to characterize the growth curve and estimate (co)variance components for the parameters (A, k and b) of the Gompertz function. The pedigree structure consisted of 790 sheep, including 45 rams and 379 ewes. Estimation of (co)variance components for each growth parameter was achieved using a univariate animal model with the restricted maximum likelihood (REML) method. Estimated values of heritability were: A (adult weight) 0.21 ± 0.06; b (integration constant) 0.25 ± 0.07; k (maturity rate) 0.16 ± 0.06; age at the inflexion estimated as (ln(b)/k) 0.24 ± 0.07; and absolute growth rate as [k*(0.368*A)* ln(A/0.368*A)] 0.22 ± 0.07. The growth of males was 24% (P < 0.05) faster than that of females; adult weight was 25 ± 0.7 kg for males and 23 ± 0.7 kg for females; absolute growth was 59 ± 2 g and 44 ± 2 g per day for males and females respectively. The Chiapas breed of sheep is a small animal with a slow growth curve, probably due to its adaptation to the environmental conditions where it lives. Growth curve can be modified through selection.

The Gompertz is one of a family of growth functions that, when the environment (e.g. food, housing) is non-limiting, provides a useful description of growth as a comparatively simple, single equation. It has three parameters of which the important ones are mature size, A, and the rate parameter, B. Estimates of A and B, however, are highly correlated and defining their separate values for individual animals is problematic. This problem was explored using five methods for estimating the parameters, or transformations of them, to describe the growth of two genotypes of Suffolk sheep kept under non-limiting conditions. One genotype was under selection for high lean growth rate and the other was its control. Live weights that were collected at least fortnightly from near birth to 150 days of age over a 9-year period on 1934 lambs were used. The Gompertz form adequately described the growth of the great majority of the lambs evaluated. When considering A and B as a lumped parameter, Z = A·B, and fitting Z, B and an initial condition (a transformed birth weight) as the parameters, the problems in estimation were substantially overcome as shown by a low correlation of Z with estimates of B both within and across animals. Usefully Z has a biological interpretation in that Z/e is the maximum daily growth rate. Since the Gompertz form adequately described growth in these sheep, the extent of genetic co-variation for the growth parameters values (A, B, Z) was estimated to determine if they were amenable to selection. A weighted univariate animal model was fitted. Mature size, A, and the rate parameter, B, were moderately heritable (0·37 (s.e. 0·04) and 0·38 (s.e. 0·05), respectively) as was live weight at 150 days of age (0·31 (s.e. 0·06)). However there was a substantial negative genetic relationship between A and B (–0·48). Z was highly heritable (0·72 (s.e.0·05)). After 9 years of selection, the genotype selected for high lean growth rate was heavier (P < 0·001) at 150 days of age (5·2 kg) and at maturity (6·6 kg), with a maximum growth rate (Z/e) that was 1·12 times that of the control. Our lumped parameter Z, in effect a rate parameter scaled for mature size, avoided problems in estimating A and B and, in so doing, offers a general and robust description of lamb growth amenable to selection.