Effect of selection for productive traits in broiler maternal lines on embryo development

Abstract

This study used 300 females and 30 males with 36 weeks of age from the selected PP and control PPc maternal broiler lines. PP has been selected for heavy body weight (PC) and high egg production for eight generations. Fertile eggs were collected and weighed individually for 4 periods of 5 consecutive days at two-week intervals. In each period, a total of 960 eggs/line were identified and separated in groups of 240 eggs, and stored for later incubation. Embryo weight (PE) was evaluated at 9 (P9), 11 (P11), 13 (P13), 15 (P15), 17 (P17) and 21 (P21) days of incubation. The objective was to estimate the effect of selection on embryo development. Egg weight (PO) was similar between the two lines. The differences in PE were significant from P15 on, resulting in 1.9g of difference in the chick weight, indicating correlated genetic changes in the embryo development, which can be credited to the selection for PC. Changes in PE while PO was kept unaltered modified the correlations between these two traits. Differences were significant from P13 on and estimated correlations for P21 were 0.72 and 0.70 for PP and PPc, respectively. Chick weight corresponded to 70.91% (PP) and 68.48% (PPc) of egg weight. The estimated increase in P21 that resulted from the increase of 1.0g in PO was 0.71 in PP and 0.68g in PPc

Effect of selection for productive traits in broiler male lines on embryo development

“…In general, the range found in literature for P21 is between 0.50 and 0.95 (Yannakopoulos & Tserveni-Gousi, 1987). Hatchling weight corresponded to 71.94 and 68.96% of the egg weight (Table 3) for LL and LLc, respectively, which is consistent with the findings of Schmidt et al (2003b). After P13, increases in embryo weight for each 1.0g increase in EgW were 0.16 (P13), 0.29 (P15), 0.45 (P17), and 0.73g (P21) for the LL line, and 0.15 (P13), 0.27 (P15), 0.41 (P17), and 0.69g (P21) for LLc.…”

“…As EgW remained similar between the lines, which had et al (2003b) for female lines, and lower than those verified by Hassan & Nordskog (1971), who estimated correlations closer to zero at P14, 0.50 at P16, and 0.90 at P21. The stronger emphasis on the selection for body weight in the male line, as compared to the female line (Schmidt et al, 2003b) increased in 1.4% the correlation between EgW and hatchling weight. In general, the range found in literature for P21 is between 0.50 and 0.95 (Yannakopoulos & Tserveni-Gousi, 1987).…”

“…Individual or genetic line characteristics affect the correlation between egg weight and chick weight. Schmidt et al (2003b) observed a 3.0% reduction in that correlation in selected lines as compared to control lines after eight generations of selection, with a reduction of 2.5% in the egg weight to chick weight ratio. Increases in chick weight resulting from an increase of 1.0g in egg weight were of 0.71 and 0.68g for selected and control lines, respectively.…”

“…The correlation between egg weight and embryo weight increases with embryo development stage, and becomes significant after day 13 of incubation. Final chick weight is primarily determined by initial egg weight, typically corresponding to 62 to 78% (Whiting & Pesti, 1983;Wilson & Harms, 1988;Schmidt et al, 2003b), and secondarily by weight loss during incubation, eggshell weight and egg residue weight, genetic line, incubation time and conditions, breeder age, and chick sex.…”

Nutrient utilization during incubation and juvenile growth of indigenous and exotic chicken in Nigeria

“…Besides, when chickens are selected for various post-hatch characteristics, they may also differ in their embryonic developmental trajectories (Clum et al, 1995). Avian embryos develop and grow from nutrients stored in the egg over a wide range of time (Schmidt et al, 2003). Amounts and forms of nutrients deposited in the egg determine the success of embryo development and hatching of a healthy chick.…”