The sixth generation of three native chickens: expected response, mortality, body weight, and productivity

The study aimed to assess the performance of three native chicken genotypes over six generations under intensive management. A total of 1488 day-old chicks (Naked Neck, NN-316; Hilly, HI-535; and Non-descript Deshi, ND-637) were used to produce the sixth generation (G 6 ). Adult birds were individually housed with feeders and drinkers. Concentrate feed containing 20.06 % CP and 2908 Kcal ME/kg DM; 18.13 % CP and 2904 Kcal ME/kg DM and 16.33 % CP and 2845 Kcal ME/kg DM, were fed twice daily in the morning and evening to the birds during the brooding, growing and laying periods, respectively. Significant differences in body weight at 8 th week was observed, with HI genotype having the highest weight (705.76g). NN genotype had slightly higher chick mortality (3.79 %) compared to ND (3.13 %) and HI (2.80 %) between 0–8 weeks. Age at first egg was affected by genotype, with ND, HI, and NN laying at 148.84, 152.39, and 153.24 days, respectively. Fertility was also influenced by genotype, with the highest hatchability in ND (88.98 %), intermediate in HI (83.72 %), and lowest in NN (79.99 %). In conclusion, HI genotype is recommended for meat production, while NN genotype is suitable for egg production. Continued selection of indigenous chicken lines is advised for further improvement.


Introduction
Poultry management in Bangladesh has undergone remarkable improvements in recent years, marked by a substantial increase in production.However, the Bangladeshi poultry industry grapples with a significant hurdle the scarcity of indigenous parent breeding stock.In light of this challenge, exploring the potential of local chicken production emerges as a viable strategy, offering opportunities for diversifying the nation's agricultural production base and creating alternative income streams.Faruque et al. (2015) and Hassen et al. (2009) have shed light on a crucial aspect of this issue namely, the presence of substantial phenotypic variations and the possibility of genetic diversity within indigenous chicken breeds and varieties.This discovery highlights the potential for implementing selective breeding programs as a means to further enhance the genetic stock of these indigenous chicken populations.The cornerstone of achieving optimal local chicken production hinges on genetic improvement.As expounded by Strandberg and Malforms (2006), selection within populations can yield enduring and continuous genetic enhancements.The crux of this process centers on increasing the prevalence of desirable genes within the population.Therefore, an effective breeding strategy involves a twofold approach: the development of pure breeds, which ensures the preservation of genetic integrity, coupled with selective breeding programs within local breeds.Such an approach promises manifold benefits, ensur- ing the preservation of unique genetic characteristics while enhancing desirable traits (Ali, 2018;Ali & Islam, 2021;Ali et al., 2021).To fully capitalize on the genetic diversity within these indigenous chicken stocks, it becomes paramount to employ these resources to improve economic traits, such as body weights and annual egg production, within chicken breeding programs.This perspective underscores the value of genetic diversity as a foundational element in the quest to optimize poultry production.In this context, the present study embarks on a comprehensive evaluation of the performance of three indigenous chicken genotypes ND, HI, NN within the confines of an intensive management system.By rigorously assessing the genetic potential and performance of these genotypes, we aim to contribute valuable insights and recommendations to bolster the indigenous poultry industry in Bangladesh, ultimately fostering sustainable growth and economic development.

Bird rearing and data collection
The birds were housed in an open-sided semi-gable roof structure with a concrete floor.Fences were constructed using galvanized wire net.Individual cages were used to raise the adult birds.Every cage had its own feeder and drinker.All of the birds were raised in a naturally ventilated poultry coop with a 16-hour photoperiod that included 12 hours of sunlight and four hours of artificial lighting.Maize, rice polish, soya bean meal, protein concentrates, and synthetic methionine and lysine were the materials utilized to produce the diet.All diets contained a trace mineral and vitamin premix.The diets were also supplemented with common salt and di-calcium phosphate (DCP).During the brooding, growing, and laying periods, concentrate mixtures containing 20.06 % crude protein and 2908 Kcal ME/kg DM, 18.13 % crude protein and 2904 Kcal ME/kg DM, and 16.33 % crude protein and 2845 Kcal ME/kg DM were given twice daily in the morning and evening.Water was also available ad libitum twice daily, in the morning and evening.Drinkers were cleaned on a daily basis, whereas feeders were cleaned twice a week.Every morning, the amount of feed refusals was recorded.
Selection and mating plan I) Selection objective.The study's selection objectives were to enhance the egg production, egg weight and/or growth rate of Indigenous chickens based on the genotype of birds.The improvement aim for egg weight is to increase by 1 g in every generation, the improvement target for egg production rate is to increase by 2 % per generation, and the improvement target for growth rate is to increase by 20 g per generation.
II) Selection criteria.In each generation, selection was performed in two stages.Firstly, selection was performed on the basis of breeding value for 8 th week body weight and physical appearance and secondly, at 40 th week of age on the basis of an index comprising the following parameter; age at first egg (days), body weight (g) at 40 th week of age, egg production (%) up to 168-280 days and egg weight (g) at 40 th week of age.
III) Mating plan.Using artificial insemination (AI), selected male and females were mated assortative with a maximum male: female ratio of 1: 5, avoiding mating among close relatives but simultaneously retaining the purity of the local chickens.The following mating strategy is depicted in Table 1.

Statistical analysis
All collected data were analyzed using the Generalized Linear Model (GLM) technique in SPSS 11.5 for Windows (SPSS, 1998).Snedecor and Cochran (1989) theory was used for all statistical reasons.The data used in the study came from three separate genotypes, and the data structures were imbalanced.The number of birds differed by class.As a result, it confirmed the properties of a non-orthogonal factorial experiment.To account for this circumstance, the data were analyzed using a factorial arrangement in a CRD using the General Linear Model (GLM) Univariate Procedure in the SPSS Computer Program.The following general linear statistical model was used to analyze the different parameters: Yij = μ + g i + e ij, where, Y ij is the dependent variable of the experiment; μ is the overall mean; g i is the effect of ith genotype (i=1-3); e ij is the error term specific to each record.

Prediction of expected selection response
Expected selection response in three types of indigenous chicken for body weight at 8 th week was estimated using the following equation (Falconer, 1996).R = h 2 × S Where: R = Expected response in mass selection, h 2 = heritability, h 2 for BW at 8 th week of age, S = Selection differential.

Body weight
Table 2 displays the effect of genotype on body weight.In all age groups, the genotype had a significant (p<0.001)effect on body weight.Day-old chicks of ND, HI, and NN had average initial body weights of 33.280.13, 33.870.15, and 32.050.19g, respectively (Table 2).The day-old weight of NN chicks was 5.37 % less than that of HI chicks.The difference in day-old weight was just 1.82 g between HI (33.87 g) and NN (32.05 g) chicks.Faruque et al. (2017a) observed that the body weight at hatch for the ND, HI, and NN genotypes in foundation stock under rigorous management was 27.74, 28.00, and 24.96g, respectively, which was much lower than the current study.It indicates that day-old weight of three types of indigenous chickens is increasing generation after generation through selection and breeding.Significantly (p < 0.001) body weight differences among the genotypes were observed at 4 th , 8 th and 12 th weeks of ages.The 4 th , 8 th and 12 th weeks body weights of ND, HI and NN were 188.44, 233.97 and 199.32g;564.33, 705.76 and 560.94 g;864.98, 1073.45 and891.87 g, respectively. Faruque et al. (2017b) found the body weight at 8 th week of age for HI and NN genotypes in fourth generation were 674.68 and 545.23 g, respectively which were much lower than the present observations.It indicates that body weight of HI (705.76 g) and NN (560.94 g) genotypes at 8 th week of age have increased in sixth generation than fourth generation.On the other hand, body weight of ND (570.95 g) at the same age in fourth generation is more or less similar to the present findings.294) p < 0.001 DOC = Day Old Chick; ND = Non-descript Deshi; HI = Hilly; NN = Naked Neck; figures in the parentheses indicate the number of observations; least squares mean without a common superscript along the row within a factor differed significantly (p < 0.001)

Mortality
Table 3 shows that the Naked Neck genotype had higher chick mortality (3.79 %) than the ND (3.13 %) and HI (2.80 %) at 0-8 weeks of age.The mortality rate in NN chickens was marginally lower than in ND and HI chickens (Khatun et al., 2005).This finding is not similar to our cur-rent findings.In this investigation, the HI genotype had better survivability.Under intensive rearing conditions, the mortality rate of ND, HI and NN in the brooding period (0-8 weeks) were 3.10, 4.05, and 2.92 %, respectively (Faruque et al., 2017b;Ali et al., 2020).Khan (2008) observed 70 % mortality of indigenous hens under free range management.

Productive and reproductive performance
The age at first egg laid was significantly (p < 0.001) affected by genotype (Table 4).The estimated age at 1 st egg of ND,HI and NN were 148.84,152.39 and 153.24 days,respectively.The average age at first egg of ND (148.84 days) was 4.4 days earlier than that of NN (153.24 days).The average age at first egg of NN (153.24days) in sixth generation was comparable to that of NN (152.7 days) reported by Faruque et al. (2015).The fertility of the present study was 87.84 %, 82.85 % and 82.46 %, respectively in ND, HI and NN genotypes, which was little bit lower than that reported by Khatun et al. (2005) and more or less similar to the findings of Faruque et al. (2015).The lowest hatchability reported in NN (79.99 %) could be due to the highest egg shell thickness and stronger breaking strength of NN eggs.Faruque et al. (2015) reported that the hatchability was 89.0 %, 85.6 % and 77.5 %, respectively in ND, HI and NN genotypes, and was more or less similar to the present findings.The dead in germ of three indigenous chickens is in agreement with the findings of Faruque et al. (2015) who reported 2.2 %, 2.3 % and 3.1 % dead in germ in ND, HI and NN genotypes.Feed consumption from 9 to 16 weeks shows that there was significant (p < 0.001) variation in feed intake among the indigenous chickens.At 16 weeks, the NN genotype had the lowest (63.87 g) and greatest (84.42 g) daily feed intake, respectively.The genotype had a substantial (p < 0.001) effect on hen-day egg production (HDEP%) in this study.The average HDEP% of ND, HI, and NN in this study was 62.85, 51.92, and 57.79, respectively.This study's finding of a substantial influence of genotype on HDEP% matches the findings of Miah et al. (2002), who observed that breed had a significant (p < 0.05) effect on hen-day egg production.At 22-28 weeks of age, the ND genotype had the greatest HDEP% (62.85).This finding is in agreement with the finding of Faruque et al. (2015) who found the highest HDEP% in ND genotype (51.4) at 24-45 weeks of age.

Expected response
As shown in Table 5 that 8 th week body weight of males ND, HI and NN birds were expected to increase by 76.52, 67.81 and 45.33 g, respectively.While in females ND, HI and NN birds, the expected responses were 18.89, 17.66 and 16.76 g, respectively.Both male and female birds showed a considerable response to selection as observed in 8 th week body weight.As estimated, the expected response to selection of 8 th week body weight was highest in ND (76.52 g vs. 18.89 g) males and females compared to other genotypes.Faruque et al. (2015) found 8 th week body weight of males ND, HI and NN birds were expected to increase by 52.03, 53.98 and 37.40 g, respectively.While in females ND, HI and NN birds, the expected responses were 20.92, 24.70 and 12.43 g, respectively.
Figure 1 depicts the annual egg output of a selected indigenous chicken generation by generation (G 0 to G 6 ).ND genotype produced more eggs than HI and NN genotypes in the first generation, whereas NN genotype produced more eggs in the second generation.

Table 1
Mating plan of three native chickens

Table 2
Body weight of native chicken up to 12 th week of age

Table 3
Effect of genotype on chick mortality (%) of native chicken during 0-8 weeks of age