Age At Sexual Maturity Research Articles

Genetic and Phenotypic Correlations between Production and Reproduction Traits in Frieswal Cattle under Field Progeny Testing Programme

Aim: To estimate the genetic and phenotypic correlations in production and reproduction traits in Frieswal Cattle under FPT. Place and Duration of Study: G B Pant University of Agricultural and Technology, Pantnagar, Uttarakhand, India, Between March, 2023 to March, 2024. Methodology: The present study was conducted on Frieswal cattle, a synthetic breed, using data from 1163 first lactation records, progenies of 67 sires, spread over period of nine years (2013-2021) as part of an ongoing field progeny testing programme at GBPUA&T, Pantnagar, Uttarakhand. The study aimed to estimate genetic and phenotypic correlations among various production and reproduction traits, such as test day peak yield (TDPY), first lactation 305-days milk yield (FL305D-MY), fat percentage (FP), first lactation length (FLL), age at sexual maturity (ASM), age at first calving (AFC), gestation period (GP), first calving interval (FCI), first service period (FSP), and number of services per conception (NSPC).The data were analyzed using WOMBAT software. Results: The study revealed that age at first service (ASM) and age at first calving (AFC) had very high genetic (0.99) and phenotypic (0.99) correlations, suggesting they were influenced by the same genes. A strong genetic correlation (0.71) between ASM and gestation period (GP) indicates a close association, while the negative correlation between ASM and total days to peak yield (TDPY) (-0.76) suggests younger cows reach higher peak yields. ASM’s negative genetic correlation (-0.57) with first lactation 305-days milk yield (FL305D-MY) implied that selecting for earlier maturity could enhance milk production. Positive correlation between ASM and reproductive traits (FCI, FSP, NSPC, and FDP) were observed, while FL305D-MY showed high negative correlation with traits like FLL and FP but positive phenotypic correlation with FLL, FCI, and FSP. Additionally, there were varied genetic correlation among FCI, FSP, NSPC and FDP, highlighting complex inter-trait relationships. Conclusions: The present study highlighted the potential of Frieswal herd for selective breeding to improve both milk production and reproductive efficiency. By focusing on traits like age at sexual maturity (ASM), age at first calving (AFC), and milk yield indicators such as test day peak yield (TDPY) and first lactation 305-days milk yield (FL305D-MY), breeders can target genetically associated traits for enhanced overall productivity. These findings provide a valuable foundation for future genetic improvement strategies in Frieswal cattle.

Exploring polymorphism's impact on layer production traits: A deep dive into association studies and candidate genes in Kadaknath

This investigation aimed to study the polymorphism and association of important egg production linked candidate genes and layer performances in Kadaknath. The Genomic DNA samples were obtained from blood of 112 birds that were chosen at random. RestrictionFragment Length Polymorphism (RFLP) patterns of three candidate genes viz., cGH, MTNR1C and VIPR-1 was determined using SacI, MboI and HhaI restriction enzymes, respectively. The alleles were separated on 2 % AGE and their molecular sizes were estimated.Two out of the three genes studied i.e. cGH and MTNR1C showed polymorphism however VIPR-1 revealed monomorphic patterns. The different genotypes obtained were then associated with layer performance traits using least-squares analysis of variance. The cGH/SacI genotype was found to have a substantial impact on egg production up to 40 weeks (EP40) and age at sexual maturity (ASM) via association analysis. The cGH gene's AC genotype was linked to the lowest ASM (192.41 ± 11.84 days) and greatest EP40 (36.72 ± 8.86). The EP40 was also affected significantly by MTNR1C/MboI genotypes and birds with AA genotype attained higher body weight at 20 weeks (BW20) and had the highest EP40 (49.29 ± 6.84). The findings suggest that the markers identified can be used in Marker Assisted Selection primarily to select Kadaknath birds for higher BW20 (p ≤ 0.05) and may be used to select birds for lower ASM and higher EP40 with relatively lower level of significance (p ≤ 0.15). It emphasizes on adapting candidate gene PCR-RFLP genotype based selection for faster genetic improvement in layer economic traits of Kadaknath.

Computation of Heritability for Production and Reproduction Traits in Frieswal Cattle under Field Progeny Testing

Aims: To study the genetic parameter (heritability) for production and reproduction traits in Frieswal cattle under field progeny testing programme. Place and Duration of Study: G B Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, India, between March, 2023 and March, 2024. Methodology: The present study was conducted on 1163 Frieswal cattle comprised of five different sets maintained at six field units over a period from 2013-2021. The traits considered were age at sexual maturity (ASM), age at first calving (AFC), gestation period (GP), test day peak yield (TDPY), 305 days milk yield (305D-MY), fat percentage (FP), lactation length (LL), calving interval (CI), service period (SP), number of services per conception (NSPC), dry period (DP). The data were analyzed for the estimation of heritability by the software WOMBAT. Results: The heritability estimates of the traits namely; ASM, AFC, GP, TDPY, 305D-MY, FP, LL, CI, SP, NSPC and DP were 0.469±0.082, 0.467±0.082, 0.259±0.067, 0.248±0.059, 0.354±0.013, 0.413±0.069, 0.389±0.071, 0.394±0.071, 0.452±0.072, 0.072±0.046 and 0.08±0.06, respectively. Conclusion: Therefore, the heritability estimates were found to be low to high magnitude for different reproduction and production traits and further it has been concluded that, this study will aid breeders in selecting high-performing animals for future generations, taking into account the genetic factors that influence milk production and reproductive traits during early lactation.

Development of novel egg type chicken variety with improved productivity for rural backyards of India

Rural poultry farming with improved high producing chicken varieties is transforming the rural livelihoods. The present study was aimed at developing a high egg producing variety suitable for backyard poultry farming. A total of 602 female birds representing five crossbreds, i.e. Kadaknath × IWH (KH), PD-3 × IWH (DH), PD-2 × IWH (VH), PD-1 × IWH (CH) and PD-3 × KH (DKH) were evaluated for their performance up to 72 weeks under farm conditions. The traits evaluated were body weights at 8, 16, 20, 40, 52, 64 and 72 weeks age at sexual maturity (ASM), egg production and egg weight at 40, 52, 64 and 72 weeks and egg quality traits. Analysis of variance was used to assess the effect of genotypes on different traits and heterosis was estimated to check the superiority of the crosses over the parent lines. Genotype had significant influence on all the traits. Morphologically, only DKH crossbred had multi-coloured plumage, while all other crosses had white plumage with brown patches. DKH cross produced about 239.2±2.96 eggs annually and also witnessed the highest heterotic gains for all the body weight traits. Also, heterosis for ASM was very low for DKH cross and hence, in desired direction. Based on present findings, the three-way DKH cross owing to its multi-coloured plumage and good performance can be further studied for its potential as a high-producing layer variety in rural backyards.

Delineating maternal influence in regulation of variance in major economic traits of White Leghorns: Bayesian insights.

Proper variance partitioning and estimation of genetic parameters at appropriate time interval is crucial for understanding the dynamics of trait variance and genetic correlations and for deciding the future breeding strategy of the population. This study was conducted on the same premise to estimate genetic parameters of major economic traits in a White Leghorn strain IWH using Bayesian approach and to identify the role of maternal effects in the regulation of trait variance. Three different models incorporating the direct additive effect (Model 1), direct additive and maternal genetic effect (Model 2) and direct additive, maternal genetic and maternal permanent environmental effects (Model 3) were tried to estimate the genetic parameters for body weight traits (birth weight, body weight at 16, 20, 40 and 52 weeks), Age at sexual maturity (ASM), egg production traits (egg production up to 24, 28, 40, 52, 64 and 72 weeks) and egg weight traits (egg weight at 28, 40 and 52 weeks). Model 2 and Model 3 with maternal effects were found to be the best having the highest accuracy for almost all the traits. The direct additive genetic heritability was moderate for ASM, moderate to high for body weight traits and egg weight traits and low to moderate for egg production traits. Though the maternal heritability (h2mat) and permanent environmental effect (c2mpe) was low (<0.1) for most of the traits, they formed an important component of trait variance. Traits like egg weight at 28 weeks (0.14±0.06) and egg production at 72 weeks (0.13±0.07) reported comparatively higher values for c2mpe and h2mat respectively. Additive genetic correlation was high and positive between body weight traits, between egg weight traits, between consecutive egg production traits and between body weight and egg weight traits. However, a negative genetic correlation existed between egg production and egg weight traits, egg production and body weight traits, ASM and early egg production traits. Overall, a moderate positive genetic correlation was estimated between ASM and body weight traits and ASM and egg weight traits. Based on our findings, we can deduce that maternal effects constitute an important source of variation for all the major economic traits in White Leghorn and should be necessarily considered in genetic evaluation programs.

Genetic and Phenotypic Trend and Inbreeding Effects for Sexual and Egg Production Traits of Iraqi Local Chickens

A study was conducted to estimate genetic and phenotypic trend and inbreeding effect on a sexual and egg production trait in Iraqi brown local chickens. Data on 2234 hens raised in poultry research stations from successive 6 generations of selection for high egg production during the first 24 weeks of production were used. Data of age at sexual maturity (ASM), body weight at sexual maturity (BWSM), first egg weight (FEWT), egg weight (EW), egg number (EN), and egg mass (EM) were recorded individually. The univariate animal models under Average Information Restricted Maximum Likelihood (AI-REML) of Wombat package were applied to estimate the heritability, BLUP-breeding value and inbreeding rate. The heritability estimates based on individual animal model was 0.39±0.05, 0.42±0.05, 0.17±0.04, 0.68±0.04, 0.40±0.05 and 0.40±0.05 for the traits mentioned above respectively. Average breeding values across generation tend to be positive in productive traits but it was negative in ASM, BWSM and FEW. The overall predicted genetic gains, after 6 generations of selection, estimated by the regression coefficients of the breeding value on generation number were equal to -0.010, 0.029, 0.033, -0.397, -1.514, and -41.541, for ASM, BWSM, FEWT, EW, EN and EM, respectively. In conclusion, the moderate to high heritability estimated for egg production traits suggested that these traits could be improved through selection. The effect of the inbreeding rate negatively on some traits and positively on other traits suggested that both traits could not be improved simultaneously using additive selection. The inconsistency between phenotypic and genetic trends suggests that genetic progress was not achieved in a higher magnitude.

Age Structure and Body Size of the Plateau Brown Frog (Rana kukunoris) in the Jiuzhaigou National Nature Reserve and Potential Climatic Impacts on Its Life History Variations

Jiuzhaigou National Nature Reserve (JNNR) is a renowned World Biosphere Reserve and UNESCO-designated World Nature Heritage Site. The age structure and body size of a population are crucial for assessing the quality of habitats in which a population lives and are essential for the vertebrate conservation and management, especially for amphibians. Unfortunately, information about the life history traits of amphibians is currently unavailable in JNNR. Herein, we first estimated the age structure and body size of Rana kukunoris, which is endemic to the Eastern Qinghai-Xizang Plateau. Then, we compared our data with 28 reported populations along an elevation gradient (1797–3450 m) and investigated how life history traits respond to climatic variations. Our results indicated the following: (1) For individuals from JNNR, the maximum longevity is 8 years, age at sexual maturity (ASM) is 2 years, suggesting a favorable ecological environment in JNNR. Notably, females are significantly larger than males due to the age factor. (2) The average age and ASM show a positive correlation with elevation. However, when the elevation exceeds 3000 m, the average SVL initially increases and then decreases due to the harsh environmental conditions at higher elevation. (3) Temperature and/or UV-B have a significant impact on the average age, ASM, and average SVL variations of R. kukunoris, suggesting adaptive potential of this species via life history variations in light of environmental changes. These accounts provide antecedent information about the life history traits of amphibians in JNNR, and provide insights into the driving factors of the life history variations of the plateau brown frog.

Reproductive parameters of Bering‐Chukchi‐Beaufort Seas bowhead whales

AbstractData from Bering‐Chukchi‐Beaufort Seas bowhead whales (Balaena mysticetus), harvested during 1973–2021 by aboriginal subsistence hunters, were used to estimate reproductive parameters: length at sexual maturity (LSM), age at sexual maturity (ASM), pregnancy rate (PR), and calving interval. Sexual maturity (N = 187 females) was determined from the presence/absence of corpora in the ovaries, or a fetus. Using sampling bias‐corrected logistic regression, LSM was estimated at 13.5 m, 95% CI [13.0, 13.8]. There was a downward trend in LSM over time, statistically significant with one method but marginal with another. A growth model translated this estimate to an ASM estimate of 23.5 years, 95% CI [20.4, 26.7]. Pregnancy rate was determined from mature females (N = 125), and from a subset limited to certain autumn‐caught whales (n = 37) to reduce bias. The PR was estimated at 0.46 globally, 95% CI [0.36, 0.55] and 0.38 for the autumn sample, 95% CI [0.20, 0.51]. Both estimated PRs are consistent with a 3‐year calving interval, because the larger estimate includes two cohorts of pregnant whales harvested in spring, and bowhead whale gestation is longer than 12 months. These analyses represent the most conclusive empirical estimates of ASM, LSM, and PR for this bowhead whale stock from the largest available data sets to date.

CORRELATIONS AMONGST TRAITS OF ECONOMIC IMPORTANCE IN LAYER TYPE CHICKENS UNDER RECIPROCAL RECURRENT SELECTION

The objective of this study was to estimate genetic and phenotypic correlations amongst traits in layer type chickens under reciprocal recurrent selection. Matings within pure male line and female lines were carried out to produce purebred male line (AA x AA) and female line (BB x BB). A total of 364 pullets arising from 207 hens and 23 cocks in generation 1 and 440 pullets from 70 hens and 10 cocks in generation 2 under selection were monitored in individual cage units for part period egg production up to 280 days. Parameters considered were age at sexual maturity (ASM), body weight at 20 and 40 weeks (BW 20 and BW40), egg weight average (EWTAV) and egg production up to 280 days (Egg 280). Results obtained shows that ASM had a high negative genetic (-0.52 to -0.64) and moderate phenotypic (-0.39 to -0,46) correlations with BW20 in the male line, positive genetic and phenotypic correlations with EWTAV in both male (0.41 to 0.80 and 0.07 to 0.26) and female line (0.53 and 0.09 to 0.14) and negative genetic and phenotypic correlations in both male (0.45 to -0.65 and -0.08 to -0.53) and female (-0.37 and -0.20), lines, respectively. Similarly, BW40 had positive genetic and phenotypic correlations (0.68 to 0.93 and 0.01 to 0.20) with Egg-280 in the female line. EWTAV had a negative genetic and phenotypic correlation with Egg280 in both male (-0.53 to -0.96 and -0.09 to -0.17) and female line (-0.15 to -0.27 and -0.09 to -0.15), respectively. It was concluded that the favourable correlations that exist between traits measured in this study for both male and female lines indicate the presence of non-additive genetic effects which can be utilized through selection and crossing for commercial use.

Association of vasoactive intestinal peptide receptor 1 gene polymorphism with layer economic traits in Rhode Island Red chicken

The research work was conducted to determine allelic polymorphism of vasoactive intestinal peptide receptor-1 (VIPR-1) gene and its association with layer traits in Rhode Island Red (RIR) chicken. Blood samples were collected from pullets (n=111) belonging to five hatches. Data on body weight at 20 weeks of age (BW20) and layer economic traits, viz. age at sexual maturity (ASM), egg weight at 28 (EW28) and 40 weeks (EW40) of age, and egg production up to 40 weeks of age (EP40)) were recorded. Genomic DNA was isolated by phenol chloroform extraction method. Samples were amplified for product sizes of 364, 434 and 486 bp of VIPR-1 gene. Amplified regions were digested by TaiI, HhaI and TaqI restriction enzymes. Digested fragments of TaiI and HhaI revealed monomorphism, whereas TaqI showed polymorphism. Allelic frequencies for polymorphic locus were 0.98 (A) and 0.02 (B) and genotypic frequencies for AA and AB were 0.96 and 0.04, respectively. The BW20 and layer traits (ASM, EW28, EW40 and EP40) were analysed by least-squares analysis of variance taking sire as random and hatch as fixed effect. Average ASM and egg production up to 40 weeks of age were 135.19±1.15 days and 124.55±1.94 eggs, respectively. Least-square analysis of variance had revealed significant effect of hatch on ASM, EW28 and EP40. However, effect of TaqI-RFLP genotypes was non-significant on layer traits. Further investigations on a larger sample basis are suggested to confirm effect of this mutation on layer traits as molecular marker in RIR chicken.

Inheritance of growth and production traits in Gramapriya male line chicken

A comprehensive study was carried out in Gramapriya male line (PD-6) chicken with respect to growth, production and egg quality traits utilizing the data generated from 1995 chicks and 230 hens in S-8 generation at ICAR-Directorate of Poultry Research, Hyderabad, Telangana. Highly significant differences among hatches were observed for body weight, shank length, age at sexual maturity (ASM), egg production (EP), egg weight (EW) and egg mass (EM). The least squares mean of body weights (BW) at 2, 4, 6, 20 and 40 weeks of age were 187.03±0.97, 499.74±1.58, 838.67±5.69, 2074.93±9.82 and 2891.26±15.25 g, respectively. The least squares mean of shank lengths at 4 and 6 weeks of age were 70.19±0.09 and 87.48±0.12 mm respectively. The h2 for body weight and shank length at six weeks of age was 0.31±0.06 and 0.23±0.05, respectively, which were moderate to high in magnitude. The ASM was 168.94±0.71 days. The EP40 was 69.87±1.24 eggs with an egg weight of 55.11±0.22 g. The EM40 was 3840.02±67.52 g. The heritability estimate was low for EP40 (0.09±0.11). The gradual improvement in primary trait (SL6) in parent line will improve the performance in terminal cross ‘Gramapriya’ which ultimately benefits the farmers.

Growth rates and age at maturity of Mediterranean loggerhead sea turtles estimated from a single-population foraging ground

In sea turtles, somatic growth rates and Age at Sexual Maturity (ASM) are important parameters for investigating population dynamics. Moreover, ASM informs on the time lag needed to observe the effects of past environmental variables, threats and conservation measures acting at nesting beaches on future numbers of clutches or nesting females, that are the most monitored indices. Assessing ASM of mixed populations that share the same foraging areas is difficult, as in the case of the Mediterranean Sea that is frequented by turtles originating from both the Mediterranean and the Atlantic. Here we investigated growth rates of loggerhead sea turtles (Caretta caretta) foraging in the Adriatic Sea, known to be frequented only by individuals of Mediterranean origin. Capture–mark–recapture records of 79 turtles provided growth rates ranging from – 1.1 to 9.6 cm yr−1 which were analyzed through Generalized Additive Models. When integrated with previous data on growth rates in the first years of life, results indicate a non-monotonic growth curve, likely due to an ontogenetic shift from oceanic to neritic areas. Using an integration equation, we estimated mean ASM to be 29.5 or 25.0 year based on mean nester size in Greece (83.4 cm curved carapace length, CCL) or across the Mediterranean (79.7 cm CCL), respectively. Growth rates and size-at-age are similar to the Atlantic population, but Mediterranean turtles mature earlier at a smaller size. The heterogenous growth rates and ASM reported so far in the Mediterranean are probably due, at least in part, to different foraging areas.

Estimation of genetic parameters for production, reproduction, and growth curve of Fars indigenous chicken.

Iranian native chicken, including Fars indigenous chicken, is an important genetic resource due to its adaptation to stressful environmental conditions, good endurance and resistance to disease. The aim of this research was to determine the genetic infrastructure of Fars indigenous chicken using several nonlinear functions. The dataset included body weight at hatch (BW1), body weight at the 8th week (BW8), body weight at the 12th week (BW12), weight at sexual maturity (WSM), age at sexual maturity (ASM), number of eggs in the first 12 weeks of laying period (EN), egg weight at the first day of laying (EW1), average egg weight at the 28thday of laying (EW28), and average egg weight at weeks 28, 30, and 32 of the laying period (AEW). Growth models were fitted using the NLIN procedure and WOMBAT software was used to predict variance components for the best fit model parameters. Results suggested three-parameter models, for example, Gompertz, fitted better to the data than others. The maturity weight (A), initial weight (B), and maturity rate (K) parameters in the Gompertz model were 1996.8 ± 6.63, 4.11 ± 0.03, and 0.021 ± 0.0001, respectively. The heritability of A, B, and K parameters were 0.03, 0.05, and 0.12, respectively.

Characterization of Mewari, an indigenous chicken breed, from hot tropical climate of India

Mewari, an indigenous chicken breed, was characterized for phenotypic parameters, growth, reproduction and production traits under the hot tropical climate of India. The data collected on 690 chicks were analyzed for effect of sex, hatch and their interaction on body weight and body measurements. The body weights of males were significantly higher at different weeks except at day old. Significantly higher shank and keel length was found in males as compared to females. The effect of hatch was significant on mean body weights at all ages, on shank length and breast angles at 8 weeks of age. The fertility and hatchability on fertile eggs set (FES) was 74.15±4.29% and 71.37±8.15%, respectively. The age at first egg (AFE) in the flock was 142 days and the age at sexual maturity (ASM) was 181.2±3.85 days. The average egg weights at 28 and 40 weks of age were 36.61±0.29 and 42.59±0.37 g, respectively. The hen day egg production (HDEP) up to 40 and 52 weeks of age was 28.93±0.13 and 59.87±0.14 eggs, respectively. The annual HDEP up to 72 weeks of age was 86.37± 0.13 eggs. The growth and egg production of Mewari chicken is comparable with other indigenous breeds. Mewari, a newly registered indigenous breed, needs to be further studied for various parameters to conserve and improve the breed for higher productivity.

Phenotypic performance and response to selection for reproductive traits of black bengal Goat (BBG) in a community breeding program

Black Bengal Goat (BBG) is only one goat breed in Bangladesh popularly known for its’ fecundity and carcass quality. The study aimed to investigate the genetic improvement of this goat breed in-situ through a community-based breeding program under a low input production system in three villages namely Gangatia, Borochala, and Pachpai in Bhaluka upazila of Mymensingh district. Data on a total of 657 individuals included with three progressive generations taken during 2009 - 2015 were analyzed for performance evaluation and genetic improvement as a result of two breeding strategies (BS) viz. mating within superior bucks and does, and within superior bucks and existing does and also compared with a control group mated among existing bucks and does. Statistical analysis was performed by SPSS 17.0 and genetic parameters by VCE 4.2.5. The average age at sexual maturity (ASM), age at first kidding (AFK), services per conception (SPC), litter size (LS), postpartum heat period (PPHP), and kidding interval (KI) were 233.09±2.71d, 383.01±2.61d, 1.13±0.03, 1.90±0.05, 42.41±0.84d and 186.44±0.95d, respectively. Generation and BS had significant effect on all traits, except SPC, except AFK, all other traits differed significantly among the flocks. The heritability estimates of all reproductive traits were medium ranging from 0.32 to 0.57. Genetic and phenotypic correlations among reproductive traits were low to medium (-0.03 to 0.37). The overall responses of up to three generations for ASM, LS, PPHP, and KI were -15.59d, 0.12 no, -6.14d and -7.66d per generation, respectively. It is concluded that community based breeding program with selected superior bucks and does is very rationale under a low input production system, as it improves reproductive performance in progressive generations. However, estimates of heritability and genetic correlations indicate the scope of improvement for reproductive traits with selection and breeding among does and bucks with proven genetic worth. Bangladesh J. Agri. 2019-2021, 44-46: 97-113

Genetic effects on growth and egg production traits in two-way crosses of Egyptian and commercial layer chickens

A crossbreeding experiment was conducted between the Sinai (SI), an indigenous Egyptian strain, and the exotic Lohmann Brown (LB) breeds of chickens. A total of 790 chicks were produced in four genetic groups, namely SI x SI, LB x LB, SI x LB, and LB x SI. The objective was to estimate the direct additive effect (gi), individual heterosis (hi), and maternal additive effect (gm) for growth and reproduction traits. Direct additive effects were positive (P ≤0.01) for bodyweight (BW) at 4, 8, and 12 weeks old in favour of SI. For egg production traits, gi was positive for age at sexual maturity (ASM) and age at which the first 10 eggs were produced (P10), but negative for mean 10 egg production (MP10), egg number at 90 days (EN90),mean egg number at 90 days (MEN90), and egg mass (EM). The estimates of heterosis (%) were high for BW and daily gain except for BW0. Maternal effect estimates of BW and daily weight gain were significant (P &lt;0.05) only for bodyweight at hatching (BW0), bodyweight at 4 weeks old (BW4) and daily weight gain from four to eight weeks old (DWG4-8). Thus, the Sinai and Lohmann Brown crossbreed produced favourable heterosis on the growth of the chicks. As an adapted indigenous strain, SI should be regarded as a dam line in crossing with LB, which has greater genetic potential for growth. Use of LB as a sire strain in conjunction with Sinai would increase egg production from the resulting hybrid chickens.

Analysis of (co) variance components and estimation of breeding value of growth and production traits in Dahlem Red chicken using pedigree relationship in an animal model.

Variance and covariance components of growth and production traits were analyzed employing REML animal model to assess the Dahlem Red (PD-3) chicken population for direct additive genetic, maternal effects and to estimate the estimated breeding value (EBV), genetic parameters, genetic trends and rate of inbreeding (ΔF) utilizing seven generation’s data. The generation and hatch had significant (P≤0.01) effect on the body weight at 0 day (BW0), 2 (BW2), 4 (BW4) and 6 weeks (BW6) and shank length at six weeks of age (SL6). The average least squares means (LSM) for BW6 and SL6 were 273.93±0.62 g and 53.97±0.05 mm, respectively. All the production traits were significantly (P≤0.01) influenced by generation and hatch. The average LSM for age at sexual maturity (ASM), egg production up to 40 weeks (EP40) and egg mass up to 40 weeks (EM40) were 168.82±0.25 d, 72.60±0.41 eggs and 4.21±0.07 kg, respectively. Model 5 with additive direct, maternal genetic, maternal permanent environmental and residual variance components was the best for BW0, BW2 and BW4 based on the AIC values obtained in WOMBAT. Model 4 was the best model for BW6, SL6, ASM, EP40 and EM40 with additive direct, maternal permanent environmental and residual variance components. Maternal effects were higher during early age, decreased with age, and remained present until 20 weeks of age. The heritability (h2) estimates were low to moderate in magnitude for all the growth traits and ranged from 0.02±0.03 to 0.19±0.03. The maternal heritability was high at hatch (0.35±0.06), decreased gradually until 4th week (0.02±0.01) and ceased afterwards. The heritabilities of EP40 (0.11±0.03) and EM40 (0.12±0.04) were low. The direct additive genetic correlations (ra) between BW2, BW4, BW6 and SL6 were high and positive (P≤ 0.05). The additive genetic and maternal permanent environmental correlation between EP40 and EM40 were high and positive (P≤ 0.05). The EBV of EM40 was significant (P≤ 0.05) with 0.48 kg/generation in PD-3 chicken at the end of the seventh generation. The EBV of EP40 showed an increasing trend with a genetic gain of 1.87 eggs per generation. The average inbreeding coefficient of the population was 0.019 and average ΔF was 0.007 over the last seven generations of selection. The EBV trends for primary and associated traits showed linear trends in the desired direction and negligible inbreeding.

GENETIC AND PHENOTYPIC ASSOCIATIONS OF JUVENILE BODY WEIGHTS AND EGG PRODUCTION TRAITS IN TWO STRAINS OF RHODE ISLAND CHICKENS

Data on body weight at 16 (WT16); 20 (WT20) weeks of age and at sexual maturity (WTSM) weight of first egg (WT1st), age at sexual maturity (ASM) and 120-d egg production (EN) were used to estimate genetic parameters in 636 hens of two strains of Rhode Island chikens. There were significant (P.01) differences between the two strains for all traits except for WTSM.The heritability estimates obtained ranged from 0.05 to 0.41 and 0.04 to 0.30 for strains 1 and 2 respectively. The genetic correlations obtained for the various traits were medium to high for the two strains. The phenotypic correlations were generally low but followed the same trend. The results indicate that selected stocks of the two strains would show improvements in egg production and age at sexual maturity if juvenile body weight (WT20) is employed as a selection criterion at housing for laying hens.

Progress in the Performance of Indigenous Chickens Selected for Economic Traits in Bangladesh

This study was conducted to investigate the progress in productive and reproductive performances of three indigenous chicken genotypes namely Non-descript Deshi (ND), Hilly (HI) and Naked Neck (NN) being selected since 2010 under intensive management system. Eight generations data on body weight (BW) at 8th week and seven generations data on body weight at 40th week of age, age at sexual maturity (ASM), egg production (EP) from 24-40 weeks of age and egg weight (EW) at 40th weeks of age were evaluated. It was observed that HI chicken had significantly (p<0.001) heavier body weight than ND and NN birds at both 8th and 40th week of age. Weight gains for ND, HI and NN at 8th and 40th weeks of age were 259.10, 324.08, 250.96g and 290.11, 453.13, 293.32g respectively over the seven generations of selection. Male chicks were significantly (p<0.001) heavier in body weight than females at 8th week of age. ASM decreased significantly (p<0.001) with the progress of generations of selection. The observed number of EP from 24-40 weeks of age in ND, HI and NN have increased from 58.33, 52.48 and 52.70 eggs in G0 to 72.40, 60.32 and 68.33 eggs respectively in generation six (G6). In case of ND, HI and NN chicken the EW has increased from 41.64g, 41.14g and 41.61g in G0 to 45.01g, 45.09g and 44.88g in G6 respectively. The results indicate that selective breeding program has made significant progress through increasing the mean of economic traits selected in indigenous chickens of Bangladesh coupled with their concurrent conservation ex-situ.

Mathematical Modelling of Egg Production Curves of Shikabrown Parents

This study was conducted to evaluate egg production curves of Shikabrown parents, using mathematical models. A total of 200 birds: 100 from each of the two strains of Shikabrown® parents (sire and dam) lines at the Breeding Unit of Poultry Research Programme, National Animal Production Research Institute (NAPRI) were used for the study. The birds were obtained from the selected lines (sire and dam) and were denoted as Strain A and Strain B, respectively. Body weight (BWT), age at sexual maturity (ASM), egg number (EGGNO), and egg weight (EWT) were examined. Four non-linear models (Logistic, Richard, Gompertz, and Exponential) and a linear model were used to predict the efficiency of weekly bodyweight and egg production traits. The adequacies of the models were fitted using R Package, version 3.0.3. High coefficients of determination for BWT (R2 = 0.84 - 0.93) were recorded in the models for both Strains. Strain A had higher R2 (0.93) for BWT in Richard, Gompertz and Exponential models while Strain B recorded (R2 = 0.89) in Logistic, Richard and Gomprtz models. High coefficient of determination was obtained in a reproductive trait; egg number; in which almost all the models gave (R2 = 0.70). Exponential model recorded a higher R2 (0.93) for EGGNO in strain A. EWT in strain A recorded higher R2 (0.96) coefficient of determination across the four nonlinear models except linear model with (R2 = 0.95) for egg weight. Significant differences (P&lt;0.05) were observed in the birds' performance for BWT and EWT, with strain B having a higher BWT (1.59±0.01) and Strain A having a higher EWT (48.75±0.17). Similarly, age of birds in lay had a concomitant significant differences (P&lt;0.05) in their BWT as well as their EWT. The birds performed better for BWT and EWT in week 26 and 27 for both Strains. It was concluded that Strain significantly (P&lt;0.05) had effect on BWT and EWT of Shikabrown® parent with Stain B performing better than Strain A in the former trait and strain A better than strain B in the latter trait. R2 identified differences between Strains in predicting egg production traits. Strain B was adjudged good and profitable because the Strain had the highest mean values in body weight and egg number and it is being recommended as one of the lines for future improvement of Shikabrown® .