Simulation of growth dynamics of meat and egg chickens

Abstract

The paper presents the results of research on the application of mathematical modeling of polygenically determined trait "live weight" on a wide range of genetic material of chickens. They were the original related forms of meat and egg chickens of domestic selection, descendants of the first and second generations and the improved synthetic population. Live weight of chickens was determined at the daily and 2-, 4-, 6-, 8-, 10-week-old age. Models of B. Gompertz, T. Bridges and
F. Richards were used to predict the live weight of birds. The actual values of live weight were compared with the predicted ones and the deviations between them in percent were calculated. Live weight prediction was performed at 8 and 10 weeks of age in chickens based on actual values for the first 6 weeks of rearing. When using the model of B. Gompertz in meat and egg hens F₁₀ local subpopulation "K", the offspring of F₁ showed an overestimation of live weight at the age of 8 and 10 weeks. The highest percentage of exceeding the predicted values over the actual ones was found in "Ross" chickens of the "K-2" group. In birds of other studied groups, this model also slightly overestimated the value of live weight at 8 weeks of age (by 3.79–9.62%). However, at the age of 10 weeks, this model, on the contrary, significantly underestimated the predicted live weight by 11.27–17.88%. In general, according to the model of B. Gompertz, the average percentage deviation of the actually obtained indicators of live weight and theoretically calculated in chickens of the studied groups was at the level of 3.60–7.93%. The most similar correspondence between empirical and predicted values of live weight was observed in meat and egg hens of the improved subpopulation "K-5". According to the model of T. Bridges, in most of the studied groups of chickens at 8 weeks of age there is an overestimation of live weight by 1.84–12.13%, especially in meat and egg chickens F₁₀ subpopulation "K" and descendants of F₁ group "K-2". In birds of groups "K-32" and "K-5", this model, on the contrary, slightly underestimated the value of live weight – by 1.50–3.02%. At the age of 10 weeks, T. Bridges’ model in hens of all groups underestimates the live weight in the range of 1.58-20.40%, especially in meat-and-egg hens F₁₁ and offspring F₂. In general, the average percentage of deviations of the actually obtained indicators of live weight and theoretically calculated according to this model was 2.81–7.15%. In meat-egg hens F₁₀ of the original maternal form, offspring of F₁ and group "K-5" the average percentage of deviations did not exceed 5.0%, which indicates a good correspondence of the actual live weight with the theoretically calculated. F. Richards’ model, like previous models, in chickens of most groups overestimated the predicted live weight at the age of 8 weeks - in the range of 2.86–15.96%. Whereas, in birds of groups "K-32" and "K-5", on the contrary, this model slightly reduced the value of live weight – respectively by 2.71% and 3.17%. F. Richards’ model in chickens of groups "K" (F₁₀), "K-2" and "K-5" slightly overestimated the value of live weight at 10 weeks of age – by 0.44-4.30%. At the same time, in birds of other groups, on the contrary, it underestimated the live weight at this age by 0.63–17.28%, especially in birds of groups "K" (F₁₁) and "K-32". The average percentage of deviations of empirical values calculated by this model was 2.44–6.36%. The greatest coincidence of the actual indicators with the calculated ones was found in the descendants of F₁ group "K-1". The coefficients of determination in the models used in the prediction of live weight were high, with maximum values in chickens of the synthetic group "K-5".