This experiment aimed at evaluating the effect of genetic selection on embryo development of two male broiler lines (LL and LLc). LL line was selected for eight generations for growth, carcass, and reproduction traits. The LLc line was derived from LL line in 1985, and kept under a random mating system with no selection. Fertile eggs were collected and individually weighed for four periods of five consecutive days, with two-week intervals. For every period, a total of 960 eggs/line were identified and separated in four groups of 240 eggs, and then stored for subsequent incubation. At 9 (P9), 11 (P11), 13 (P13), 15 (P15), 17 (P17) and 21 (P21) days of incubation, eggs and embryos were weighed (EmW). Egg weight (EgW) was similar between the two lines. The differences in EmW started to be significant after P15, resulting in a 2.03g difference in hatchling weight, indicating genetic changes of 0.54% by generation, which can be attributed to selection for body weight. The correlation between EgW and EmW started to be significant after P13, and correlations of 0.738 and 0.712 (P21) were observed for LL and LLc, respectively. Hatchling weight corresponded to 71.94 (LL) and 68.96 (LLc) of EgW. The estimated increases in P21 resulting from each 1.0g increase in EgW were 0.73g (LL) and 0.69g (LLc).

A total number of 300 females and 30 males of two experimental broiler lines, TT (male) and PP (female), with 39 and 36 weeks of age, respectively. Experiment 1 (TT) evaluated the effect of storage time (ST) on hatchability and embryo mortality (EM). Eggs were stored for 2 (ST1), 4 (ST2), 6 (ST3), 8 (ST4), 10 (ST5), 12 (ST6), and 24 (ST7) days and EM was assessed in the periods of 0 to 6 (EM1), 7 a 13 (EM2), 14 to 17 (EM3), 18 to 21 (EM4), and 0 to 21 (TEM) days. Experiment 2 (PP) evaluated the effect of egg weight (EW) on embryo development. Eggs were individually collected and weighed. Embryos were collected and weighed on days 9 (EW9), 11 (EW11), 13 (EW13), EW15, 17 (EW17) days of incubation and at hatching (EW21). ST linearly influenced hatchability and EM, with an estimated 1.17% reduction and a 1.15% increase, respectively for each 1.0 day of storage. Hatchability was reduced in 21% betweeb ST2 and ST7, resulting from a 462% increase in EM. The correlation between egg weight and embryo weight (EW) was significant after EW3 (0.25), reaching 0.72 for EW21, which corresponded to 70.92% of egg weight. The estimated increase in embryo weight for each 1.0g increase in egg weight was 0.71g for EW21.

The Brazilian Swine and Poultry Research Center (Embrapa Suínos e Aves) maintains a chicken breeding program for meat production since 1985. Two control lines (LLc and PPc) are maintained, whereas two male lines (TT and ZZ) and three female lines (PP, VV and KK) have been selected. This paper reports the genetic gain after 15 generations of combined selection (mass and independent culling levels) in order to develop the commercial broiler stocks Embrapa 021 and Embrapa 022. Selection pressure has been exerted on weight gain, carcass traits and fertility. In addition, female lines have also been selected for egg production, whereas males have been selected for feed efficiency since 1992. All lines have been selected for breast area instead of carcass traits since 1999. The genetic gain was estimated as the deviation between selected lines and the respective unselected lines at 42 days of age. In female lines, body weight improved 504, 548 and 587 g; average breast area increased 27.60; 16.99 and 26.43 cm²; adjusted feed conversion (42-49 d) improved -1.46; -0.97 and 1.76 units, and egg production varied 6.99; 7.12 and -3.43% units for PP, VV and KK, respectively. In male lines, body weight improved 758 and 408 g; average breast area increased 31.95 and 19.38 cm², and adjusted feed conversion improved (42-49 d) -0.99 and 1.26 for TT and ZZ, respectively. This breeding program has been effective to generate genetic gain and to develop two commercial products, Embrapa 021 (standard) and Embrapa 022 (high yield). Nevertheless, feed efficiency is still not satisfactory.

The objective of this study was to report the response to selection for fertility and hatchability in white egg layers strains, based on sire and dam performance, and the effects of inbreeding on these traits. Two selected white egg strains (CC and DD) from Embrapa´s poultry program under multiple trait selection were compared to a control strain (CCc). The control strain was established by randomly mating one male from each sire family to a non-related female from each dam family and was used to monitor genetic change in the selected lines. CC and DD were selected using family and individual information on hen-day egg production up to 40 weeks of age, egg weight, sexual maturity and 16-week-old body weight over five generations. Independent culling levels (ICL) were also used during population expansion to eliminate sires and dams with low fertility (FERT) and hatchability (HATC). Initially, FERT and HATC were over 90.0% in both selected and control strains. FERT and HATC of the selected and the control strains were compared during the last generation. FERT averages were 93.8, 93.8 and 94.4%, and HATCH averages were 93.2, 91.6 and 93.1% for CC, DD and CCc respectively. FERT and HATCH means were not different among strains. Estimated inbreeding increased at a rate of 0.4% per generation in all strains. Selection using ICL was able to effectively maintain the high initial FERT and HATC levels, and provide potential for high selection intensity in other traits. Inbreeding depression was not observed for any trait, indicating that selection compensated for any negative effects of inbreeding.

Two paternal broiler lines (LL and LLc, originated from the same stock in 1998) of Embrapa Suinos e Aves genetic program were used. Line LL had been selected for eight generations for rapid growth while LLc had been mated randomly, without selection, as a control line. In the last generation, 30 males and 240 females were used in hierarchical matings with pedigree control to determine sire effect. The same number of birds were used, but matings were at random for LLc. Eggs of both lines were incubated and embryos were collected in different development stages (40, 45, 50, 55 and 60 hours after setting) in order to determine somite number (NOS). The number of evaluated embryos were 1,967 and 498 for LL and LLc, respectively. This study aimed to determine the changes in somite formation during embryonic development that resulted from artificial selection for heavier body weight. In the evaluated generation, the differences for body weight, feed conversion ratio, carcass and breast yields between LL and LLc were 546 g; 0.16 FC units, 2.20 and 2.19%, respectively. NOS was greater in the initial (40 h) and in the final (60 h) stages for LL and in the intermediary stages (45, 50 and 55 h) for LLc, indicating significant differences in the mechanisms of somite formation and development. Considering that both lines had the same genetic origin, such deviation indicates genetic changes due to artificial selection for body weight. The heritability estimates indicated low additive genetic effect for NOS in the different stages. Since the alterations were due to artificial selection for body weight, one could consider the hypothesis of using such genetic marker throughout family selection.

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.