Phenotypic and genomic characterisation of performance of tropically adapted chickens raised in smallholder farm conditions in Ethiopia.

Background: In sub-Saharan Africa, 80% of poultry production is on smallholder village farms, where chickens are typically reared outdoors in free-ranging conditions. There is limited knowledge on chickens' phenotypic characteristics and genetics under these conditions. Objective: The present is a large-scale study set out to phenotypically characterise the performance of tropically adapted commercial chickens in typical smallholder farm conditions, and to examine the genetic profile of chicken phenotypes associated with growth, meat production, immunity, and survival. Methods: A total of 2,573 T451A dual-purpose Sasso chickens kept outdoors in emulated free-ranging conditions at the poultry facility of the International Livestock Research Institute in Addis Ababa, Ethiopia, were included in the study. The chickens were raised in five equally sized batches and were individually monitored and phenotyped from the age of 56 days for 8 weeks. Individual chicken data collected included weekly body weight, growth rate, body and breast meat weight at slaughter, Newcastle Disease Virus (NDV) titres and intestinal Immunoglobulin A (IgA) levels recorded at the beginning and the end of the period of study, and survival rate during the same period. Genotyping by sequencing was performed on all chickens using a low-coverage and imputation approach. Chicken phenotypes and genotypes were combined in genomic association analyses. Results: We discovered that the chickens were phenotypically diverse, with extensive variance levels observed in all traits. Batch number and sex of the chicken significantly affected the studied phenotypes. Following quality assurance, genotypes consisted of 2.9 million Single Nucleotide Polymorphism markers that were used in the genomic analyses. Results revealed a largely polygenic mode of genetic control of all phenotypic traits. Nevertheless, 15 distinct markers were identified that were significantly associated with growth, carcass traits, NDV titres, IgA levels, and chicken survival. These markers were located in regions harbouring relevant annotated genes. Conclusion: Results suggest that performance of chickens raised under smallholder farm conditions is amenable to genetic improvement and may inform selective breeding programmes for enhanced chicken productivity in sub-Saharan Africa.

Genotype by Environment Interactions (G*E) of Chickens Tested in Ethiopia Using Body Weight as a Performance Trait.

Ethiopia is a developing nation that could highly benefit from securing food via improved smallholder poultry farming. To support farmer and breeding decisions regarding which chicken strain to use in which Ethiopian environment, G*E analyses for body weight (BW) of growing male and female chickens were conducted. Research questions were (1) if a G*E is present for BW and (2) which strain performs best in which environment in terms of predicted BW. Analyses were performed using predicted BW at four different ages (90, 120, 150, and 180 days) of five strains (Horro, Koekoek, Kuroiler, Sasso-Rhode Island Red (S-RIR), and Sasso) tested in five Ethiopian regions (Addis Ababa, Amhara, Oromia, South Region, and Tigray) that are part of three Agro-Ecological Zones (AEZ) (cool humid, cool sub-humid, and warm semi-arid). The indigenous Horro strain was used as a control group to compare four other introduced tropically adapted strains. The dataset consisted of 999 female and 989 male farm-average BW measurements. G*E was strongly present (p < 0.001) for all combinations of strain and region analyzed. In line with previous research, Sasso was shown to have the highest predicted BW, especially at an early age, followed by Kuroiler. Horro had the lowest predicted BW at most ages and in most regions, potentially due to its young breeding program. The highest predicted BW were observed in Tigray, Oromia, and Amhara regions, which are in the main part of the cool sub-humid AEZ.

Evaluation of reciprocal F1 crosses of Fayoumi with two exotic chicken breeds 2: additive and non-additive effects on egg quality traits.

The current study evaluates additive and non-additive genetic variances for egg quality traits in six genotypes generated through pure mating and reciprocal crossing of Fayoumi (FM) with Koekoek (KK) and White Leghorn (WL). For each genotype, measurements were taken on 30 eggs randomly sampled at 32, 36, and 40 weeks of age to evaluate both external and internal egg quality parameters. The results revealed significant differences (P < 0.001) among the genotypes in all external quality traits and most internal quality traits, including yolk weight (YW), albumen weight (AW), and yolk height (YH). The results also showed that variations due to purebred effect (PE), general combining ability (GCA), maternal effect (ME), and specific combining ability (SCA) were significant in most traits, which reflects that both additive and non-additive variances are important for the inheritances of the parameters investigated. In most of the traits, the ME and PE were higher in KK and WL, while GCA was higher in KK and FM. The FM x WL had higher SCA than FM x KK. The results suggest the likelihood of genetic improvement in these genotypes through selection and crossbreeding strategies and/or a combination of the two.

Evaluation of reciprocal F1 crosses of Fayoumi with two exotic chicken breeds 1: additive and non-additive effects on egg production traits.

The present study estimates additive and non-additive effects on egg production traits in genotypes generated through pure mating and reciprocal crossing of Fayoumi (FM) with Koekoek (KK) and White Leghorn (WL). Age at first egg (AFE) and body weight at first egg (BWAFE) were determined when the first bird in the pen laid its first egg, and egg weight at first egg (EWAFE) was the average weight of eggs laid consecutively during the first 10 days. Egg number (EN) and egg weight (EW) were recorded daily from AFE to 40 weeks of age. Egg mass (EM) was the product of EN and EW. EN of hens initially housed and hens alive during the experiment were used to calculate hen-housed egg production (HHEP) and hen-day egg production (HDEP), respectively. All the traits showed statistically significant differences among the genotypes. The results revealed the importance of additive and non-additive effects, where purebred effect (PE), general combining ability (GCA), maternal effect (ME), specific combining ability (SCA), and residual reciprocal effect (RRE) significantly affected most of the traits. The KK and WL had a higher PE, and GCA was highest in KK, with FM and WL showing a higher ME. The FM x WL had higher SCA and RRE. The KK x FM and FM x WL outperformed their main and reciprocal crosses, respectively, and purebred contemporaries. Therefore, a synthetic breeding program involving KK as a sire and FM, WL, FM x WL, and KK x FM as a dam would be feasible.

Dual-purpose production of genetically different chicken crossbreeds in Ethiopia. 2. Egg and meat production of the final-crossbreed females and males.

Females and males of 7 commercial (ComCb) and 3 experimental (ExpCb) crossbreeds were produced by 6 imported parent stocks (PS) and 1 local PS. The ComCb were Dominant Red Barred (DR), Dominant Sussex (DS), Lohmann Brown (LB), Lohmann-Dual, NOVOgen Brown (NB), NOVOgen Color (NC), and local Koekoek (KK). The ExpCb were (dams × sires) DR × KK (R × K), DS × DR (S × R), and KK × DS (K × S). The females were reared to 60 wk of age, and recorded data included BW, BWG, feed intake, egg number, and egg weight, allowing the calculation of egg mass and feed conversion ratio (FCR). The males were reared to 16 wk of age and recoded data included feed intake, BW, FCR, and carcass characteristics. A total of 621 females and 516 males were tested in sex-separated trials, each with 3 replicated floor pens per crossbreed. The overall value of each crossbreed was determined by overall egg production, 60-wk BW and FCR of females, and by 16-wk BW, carcass yield, and FCR of males. The highest laying rate was exhibited by LB (68%) and NB (66%), followed by RxK and K × S (∼62%). The crossbreeds differed in feed intake and in females' FCR, with LB leading (2.74) followed by NB and S × R (3.07) then DR (3.18). In egg production, LB, followed by NB, were the best, as expected from specialized table-egg crossbreeds. The highest 16-wk BW of males and best FCR were exhibited by NC, followed by NB. In summary, LB was the best egg-producing crossbreed, but poor in meat production. Better choice for dual-purpose production would be NB, ranked second in egg production and in males' BW and FCR. NC was the best meat-producing (males and spent hens) crossbreed and the hens were second in egg-mass production. Hence, NC might be the best dual-purpose hybrid where artificial insemination is feasible and the consumers prefer large eggs and birds.

Dual-purpose production of genetically different chicken crossbreeds in Ethiopia. 1. Parent stocks' feed intake, body weight, and reproductive performance.

A total of 6 chicken parent stocks (PS) bred by European companies, and 1 local PS, were evaluated under Ethiopian condition for their reproductive performance, to be followed by testing dual-purpose performance of their crossbreed progeny. The imported PS were Lohmann Brown (LB), Lohmann Dual (LD), NOVOgen Brown (NB), NOVOgen Color (NC), Dominant Sussex (DS), and Dominant Red Barred (DR); Koekoek (KK) was obtained locally. They were reared in replicated floor-pens from 16 to 60 wk of age, and evaluated for feed intake, body weight (BW), egg production, fertility, and hatchability. In total, 1,810 females and 261 males were distributed over 4 houses in randomized blocks design. Additionally, 3 experimental crosses, R × K (DR females × KK males), S × R (DS females × DR males), and K × S (KK females × DS males) were evaluated for fertility and hatchability. The PS differed in BW, feed intake, age of sexual maturity, egg production, fertility, and hatchability. Among females, DR and DS had the highest BW, whereas LB, NB, and NC had the lowest BW. Final mean BW of the parental meat-type males of NC and LD were the highest (5,027 and 3,660 g, respectively), whereas the other parental males ranged from 2,585 to 2,955 g. Fertility of NC and LD was low because the heavy parental males had difficulty to mate naturally their small-body female mates. However, with artificial insemination (AI), fertility of NC and LD was between 75 and 80%, similar to the other 5 PS. The fertility and hatchability of eggs laid by DR, DS, and KK hens was improved by 6.3% in the experimental crosses, where these hens were mated with genetically different males. The LD hens exhibited the highest overall laying rate (64.2%) during the study period, and with AI, hatchability of LD eggs (66.6%) was the highest, making it the best chick producer. Thus, despite its high total feed intake (but similar to DR, DS, and KK), LD (followed by DR) was the best PS in this study under floor management in Ethiopia.