Genetic and phenotypic parameter estimates for body weights and egg production in Horro chicken of Ethiopia

High natural antibody titers of indigenous chickens are related with increased hazard in confinement

Natural antibody (NAb) levels and survival rates were evaluated in 4 breeds of laying hens in Ethiopia: indigenous, improved indigenous, exotic layer, and crossbred. Titers of NAb isotypes IgG and IgM binding keyhole limpet hemocyanin (KLH) in serum were measured at 20, 26, 35, and 45 wk age. Repeated-measure ANOVA showed that IgG and IgM levels vary with time within each breed (P < 0.05). Indigenous chickens had significantly (P < 0.05) higher NAb levels at all ages. The Cox proportional hazard analysis showed increased hazard with increased levels of NAbs in the exotic layers (P < 0.05). However, the reduced hazards with increased levels of NAbs were not significant in the improved indigenous and crossbred chickens. Indigenous chickens showed increased hazard with increasing levels of NAb (P > 0.05). We concluded that not only the NAb levels but also the effect of Nabs on survival vary between indigenous and improved breeds. The results indicate that NAb levels are associated with survival in elite (improved) breeds, but are associated with increased hazard in indigenous chickens.

Infection-interactions in Ethiopian village chickens

Chickens raised under village production systems are exposed to a wide variety of pathogens, and current or previous infections may affect their susceptibility to further infections with another parasite, and/or can alter the manifestation of each infection. It is possible that co-infections may be as important as environmental risk factors. However, in cross-sectional studies, where the timing of infection is unknown, apparent associations between infections may be observed due to parasites sharing common risk factors. This study measured antibody titres to 3 viral (Newcastle disease, Marek's disease and infectious bursal disease) and 2 bacterial (Pasteurella multocida and Salmonella) diseases, and the infection prevalence of 3 families of endo- and ecto-parasites (Ascaridida, Eimeria and lice) in 1056 village chickens from two geographically distinct populations in Ethiopia. Samples were collected during 4 cross-sectional surveys, each approximately 6 months apart. Constrained ordination, a technique for analysis of ecological community data, was used to explore this complex dataset and enabled potential relationships to be uncovered and tested despite the different measurements used for the different parasites. It was found that only a small proportion of variation in the data could be explained by the risk factors measured. Very few birds (9/1280) were found to be seropositive to Newcastle disease. Positive relationships were identified between Pasteurella and Salmonella titres; and between Marek's disease and parasitic infections, and these two groups of diseases were correlated with females and males, respectively. This may suggest differences in the way that the immune systems of male and female chickens interact with these parasites. In conclusion, we find that a number of infectious pathogens and their interactions are likely to impact village chicken health and production. Control of these infections is likely to be of importance in future development planning.

Genetic parameters for production and feeding behaviour traits in crossbred steers fed a finishing diet at different ages

Durunna, O. N., Mujibi, F. D. N., Nkrumah, D. J., Basarab, J. A., Okine, E. K., Moore, S. S. and Wang, Z. 2013. Genetic parameters for production and feeding behaviour traits in crossbred steers fed a finishing diet at different ages. Can. J. Anim. Sci. 93: 79–87. Because cattle can be raised postweaning under several feeding regimes, this study examined the consistency of phenotypic and genetic parameters of some production and feeding behaviour traits between two feeding periods that beef cattle received a finisher diet. Crossbred steers (n=851) were used for feeding trials from 2002 to 2009 where the steers received a finisher diet either during the fall–winter season (FP1) or during the winter–spring season (FP2). The steers evaluated in FP2 received a backgrounding diet in FP1. Traits examined include dry matter intake (DMI), average daily gain (ADG), gain: feed ratio (G:F), residual feed intake (RFI), and ultrasound measures of backfat thickness (UBF), rib-eye area (UREA) and marbling (UMB). Others include feeding duration (FD), headdown time (HDT) and feeding frequency (FF). As expected, there was no difference (P=0.90) between the RFI measured in the two periods. The two periods were similar for UBF (P=0.87) and UREA (P=0.25),while DMI, ADG and UMB were greater (P<0.04) in FP2 than in FP1. The FD, HDT and FF were greater (P<0.0001) in FP1 compared with FP2. Heritability estimates were calculated in FP1 and FP2, respectively, for ADG (0.38, 0.28), DMI (0.52, 0.42), RFI (0.16, 0.27), G:F (0.18, 0.33), HDT (0.35, 0.18) and FF (0.26, 0.46). More importantly, genetic correlations between FP1 and FP2 were estimated for DMI (0.61), RFI (0.65) and G:F (0.60). The results may indicate the influence of age or feeding period or both on these traits, which may suggest the need for multi-environment genetic evaluations to identify superior animals.

Evaluation of breeding objectives for purebred and crossbred selection schemes for adoption in indigenous chicken breeding programmes

1. The aim of the study was to evaluate the genetic and economic breeding objectives for an indigenous chicken (IC) breeding programme in Kenya. 2. A closed three-tier nucleus breeding programme with three breeding objectives and two selection schemes was simulated. The breeding objectives included IC dual-purpose (ICD) for both eggs and meat, IC layer (ICL) for eggs and IC broiler (ICB) for meat production. 3. Pure line selection scheme (PLS) for development of IC pure breeds and crossbreeding scheme (CBS) for the production of hybrids were considered. Two-and three-way crossbreeding strategies were evaluated under CBS and the impact of nucleus size on genetic gains and profitability of the breeding programme were investigated. 4. Males were the main contributors to genetic gains. The highest genetic gains for egg number (2·71 eggs) and growth traits (1·74 g average daily gain and 57·96 g live weight at 16 weeks) were realised under PLS in ICL and ICB, respectively. 5. The genetic response for age at first egg was desirable in all the breeding objectives, while that for fertility and hatchability were only favourable under ICL and PLS in ICD. Faecal egg count and immune antibody response had low, but positive gains except under PLS where the later was unfavourable. ICB was the most profitable breeding objective, followed by ICD and ICL under all the selection schemes. 6. Although PLS was superior in genetic gains and profitability and recommended in breeding programmes targeting ICL and ICB, a three line CBS should be considered in development of a dual-purpose breed. 7. Increasing the nucleus size beyond 5% of the IC population was not attractive as it resulted in declining profitability of the breeding programme.

Estimation of genetic parameters for body weight and egg production traits in Mazandaran native chicken

Native chicken breeding station of Mazandaran was established in 1988 with two main objectives: genetic improvement through selection programs and dissemination of indigenous Mazandarani birds. (Co)variance components and genetic parameters for economically important traits were estimated using (bi) univariate animal models with ASREML procedure in Mazandarani native chicken. The data were from 18 generations of selection (1988-2009). Heritability estimates for body weight at different ages [at hatch (bw1), 8 (bw8), 12 (bw12) weeks of ages and sex maturation (wsm)] ranged from 0.24 ± 0.00 to 0.47 ± 0.01. Heritability for reproductive traits including age at sex maturation (asm); egg number (en); weight of first egg (ew1); average egg weight at 28 (ew28), 30 (ew30), and 32 (ew32) weeks of age; their averages (av); average egg weight for the first 12 weeks of production (ew12); egg mass (em); and egg intensity (eint) varied from 0.16 ± 0.01 to 0.43 ± 0.01. Generally, the magnitudes of heritability for the investigated traits were moderate. However, egg production traits showed smaller heritability compared with growth traits. Genetic correlations among egg weight at different ages were mostly higher than 0.8. On the one hand, body weight at different ages showed positive and relatively moderate genetic correlations with egg weight traits (ew1, ew28, ew30, ew32, ew12, and av) and varied from 0.30 ± 0.03 to 0.59 ± 0.02. On the other hand, low negative genetic correlations were obtained between body weight traits (bw1, bw8, bw12, and wsm) and egg number (en). Also, there is low negative genetic correlation (-24 ± 0.04 to -29 ± 0.05) between egg number and egg weight. Therefore, during simultaneous selection process for both growth and egg production traits, probable reduction in egg production due to low reduction in egg number may be compensated by increases in egg weight.

Phenotypic and genetic parameters for body weights and antibody response against Newcastle disease virus (NDV) vaccine for Kuchi chicken ecotype of Tanzania under extensive management

This study was carried out to estimate phenotypic and genetic parameters for body weights and primary antibody response (Ab) against Newcastle diseases virus (NDV) vaccine for Kuchi chicken ecotype of Tanzania managed extensively. Body weight was evaluated at 8 (Bwt8), 12 (Bwt12), 16 (Bwt16) and 20 (Bwt20) weeks of age, while Ab against NDV vaccine was evaluated at 6 weeks of age (2 weeks post-vaccination). Number of birds per trait varied from 373 to 430. Mean value ± standard error (SE) over both sexes for Bwt8, Bwt12, Bwt12 and Bwt20 were 348 ± 2.8, 685 ± 5.3 g, 974 ± 6.4 g and 1,188 ± 7.3 g, respectively. Mean Ab value (HI titre in log(2)) against NDV vaccine was 4.69 ± 0.06. Heritability values ± SE for Bwt8, Bwt12, Bwt16, Bwt20 and Ab against NDV vaccine were 0.30 ± 0.13, 0.34 ± 0.12, 0.37 ± 0.11, 0.39 ± 0.12 and 0.22 ± 0.08, respectively. Genetic (r (g)) and phenotypic (r (p)) correlations were positive and high among body weights (i.e. r (g) = 0.53 to 0.74 and r(p) = 0.44 to 0.64), and were negative and low (i.e. around 0.10 and below) among Ab against NDV vaccine and body weights. Based on these estimates, it was concluded that growth performance for Kuchi chicken under extensive management is still poor. Adequate additive genetic variations exist for body weights and Ab against NDV vaccine under extensive management, thus they can be improved through selection under such environment, and further that both traits (body weight(s) and Ab) can be improved/selected simultaneously without significant reduction in genetic gain (response) for each trait.

Application of risk-rated profit model functions in estimation of economic values for indigenous chicken breeding

The economic values for productive (egg number, average daily gain, live weight, and mature weight) and functional (fertility, hatchability, broodiness, survival rate, feed intake, and egg weight) traits were derived for three production systems utilizing indigenous chicken in Kenya. The production systems considered were free-range, semi-intensive, and intensive system and were evaluated based on fixed flock size and fixed feed resource production circumstances. A bio-economic model that combined potential performances, feeding strategies, optimum culling strategies, farmer's preferences and accounted for imperfect knowledge concerning risk attitude of farmers and economic dynamics was employed to derive risk-rated economic values. The economic values for all the traits were highest in free-range system under the two production circumstances and decreased with level of intensification. The economic values for egg number, average daily gain, live weight, fertility, hatchability, and survival rate were positive while those for mature weight, broodiness, egg weight, and feed intake were negative. Generally, the economic values estimated under fixed feed resource production circumstances were higher than those derived under fixed flock size. The difference between economic values estimated using simple (traditional) and risk-rated profit model functions ranged from -47.26% to +67.11% indicating that inclusion of risks in estimation of economic values is important. The results of this study suggest that improvement targeting egg number, average daily gain, live weight, fertility, hatchability, and survival rate would have a positive impact on profitability of indigenous chicken production in Kenya.