Unbalanced sex in plot in experimentation with chickens

Abstract

The influence of unbalanced sex in the plot of broilers was studied in four ages for slaughtering (A): 44, 48, 52 and 56 days, and five size plots (P): 10 (P10); 20 (P20); 30 (P30); 40 (P40) and 50 (P50) birds. The experiment was carried out in the Centro Nacional de Pesquisa de Suínos e Aves (Swine and Poultry National Research Center) at Concórdia, SC, Brazil, in 1986, with weight data (Wi) obtained by simulation. Each combination A and P resulted an experiment, and the plot containing 50% males (M) and 50% females (F) was considered the control treatment (CT). The other treatments were organized considering all of the sex combinations in the plot, maintaining the number of birds of a determined sex equal to the control treatment (CT). The agreement, the slope and the squash of the Wi data with the normal distribution were calculated, respectively, by Lilliefors test (D), coefficient of asymmetry (a3) and coefficient of curtosis (a4). The influence of unbalanced sex (US) alterates the level of significancy in the comparison of treatments. The unbalance in relation to males is more severe than in relation to females. A difference of about 0.20% in the average of any treatment compared to the control, due to US, is enough to alterate the significancy level around α = 0.05 in experiments with more than ten birds by plot.