The recent experiment has been carried out at the Poultry research farm of the Faculty of Agriculture, Menoufia University, Shebin El-Kom, Egypt, during the period from 2018 to 2022 for three generations to investigate some egg production traits genetically and study the possibility of genetic improvement of these traits in Norfa chickens.
Results and conclusions can be summarized as follow:
- There are many (13) selection indices that were developed in the current experiment. The highest relative efficiency among all constructed indices recorded by the one trait (Egg weight at maturity) reduced selection index 99.805% followed by the body weight at maturity reduced selection index 97.839%, and finally the Body weight at maturity-restricted index 94.76%. On the other hand, the lowest (1.519%) effective index from current study was the two-traits (IR-EWM+EN42);
- Applying general selection index (IG) expected to change studied traits by +3.556 eggs, +0.638 g, and +13.711g for egg number till 42 wks, egg weight at maturity and body weight at maturity. Expected genetic gain due to application of ID-EWM in egg number till 42 wks of age, egg weight at maturity and body weight at maturity equals +3.559 eggs, +0.624 g and +13.204g, respectively. In Addition, application of ID-BWM would lead to change egg number till 42 wks of age, egg weight at maturity and body weight at maturity by +3.520 eggs, +0.535 g and +6.112 g, respectively. Among all developed selection indices in recent work, general selection index (IG) tends to be the best and led to the most desirable genetic change in studied economic traits based on the expected genetic gain values;
- Generally, results from recent work revealed that applying general index (IG) including three traits in Norfa chickens was exceedingly more effective than either completely one- or two- traits selection indices (IR-BWM, IR-EWM, IR-EN42, IR-BWM+EWM, IR-BWM+EN42 and IR-EWM+EN42). Complete restriction of one or two traits resulted in a significant reduction of the overall expected genetic changes compared to the general index;
- Results showed that using general index in selection for one generation resulted in improving egg production traits under investigation. The actual genetic gains for age at sexual maturity, body weight at sexual maturity, body weight at maturity, egg number during first 90 days of laying, egg weight at sexual maturity, egg weight at maturity and egg number till 42 wks of age were -1.990 days, +27.850 g, +13.820 g, +7.324 eggs, +0.024 g, -0.059 g and +7.924 eggs, respectively.
It can be concluded that applying selection indices including the main egg laying traits (i.e., egg number till 42 weeks of age, egg weight at maturity and body weight at maturity) leads to improve laying performance of Norfa hens regardless of the negative correlations between some traits as a multi-trait selection method.