Crossbreeding to improve local chicken breeds: predicting growth performance of the crosses using the Gompertz model and estimated heterosis

The present study aims to validate the Gompertz model to predict the growth performance of chicken crosses according to growth curve parameters of the parental lines and the estimated heterosis for each curve parameter. A total of 252 one-day-old chicks of both sexes belonging to 6 genotypes, including Ross 308, Sasso (SA), Bionda Piemontese (BP), and Robusta Maculata (RM), and the crosses between these local breeds and SA (BP x SA and RM x SA) were randomly allocated in 18 pens (3 pens/genotype) in mixed-sex groups (14 animals/pen; 7 females and 7 males). The individual body weight (BW) of all birds was recorded once a week from hatching until slaughtering (81 d for Ross 308; 112 d for SA, 140 d for the other genotypes). We drew up our final dataset with 240 birds (40 birds/ genotype; 20 females and 20 males). The growth curve of each genotype was described using the Gompertz model, and the heterosis for each growth curve parameter was calculated as the difference between F-1 crosses and the average of parental breeds. The predicted growth curve parameters were evaluated by cross-validation. The Gompertz model accurately estimated the growth curves of all the genotypes (R-2 > 0.90). Heterosis was significant for almost all growth curve parameters in both crosses (P < 0.05). Heterosis ranged from -13.0 to +11.5%, depending on parameters, but varied slightly between the crossbreeds (BP x SA and RM x SA). The predicted values of adult BW, weight at the inflection point, and maximum growth rate were overestimated for BP x SA and under-estimated for RM x SA, with a mean error between observed and predicted values <12.71% for all the curve parameters. In conclusion, the growth performance of chicken crosses between local breeds and commercial strains can be accurately predicted with Gompertz parameters of the parental lines adjusting for heterosis

The Open Method of Co-ordination: A Way to the Europeanization of Social and Employment Policies?

The open method of co-ordination (OMC) can contribute to the co-ordinated modernization of the national systems of employment and social protection in Europe, if it is institutionalized in a relatively stable way at the European level and if the European processes can influence effectively the national reform strategies. The first challenge was met successfully by the bureaucratization, codification and formalization of some co-ordination processes at the European level. These processes can be interpreted as the institutionalization of a social field. The second challenge refers to the need for an effective coupling between the European and the national arenas. Currently, the most important way of coupling these two social fields is based on mutual learning. Given the limitations of such a predominantly cognitive coupling, the Commission can either enforce the 'national ownership' of the co-ordination processes, improve the mutual learning processes or strengthen the strategic ('financial incentives') and normative ('legal obligations') forms of coupling between the European and national social fields. Copyright (c) 2008 The Author(s). Journal compilation (c) 2008 Blackwell Publishing Ltd.