Genetic Parameters For Body Weight Research Articles

78 Estimates of genetic parameters for weight, wool, and carcass traits of Rambouillet sheep

Abstract The Rambouillet sheep breed is the foundation to most western range sheep in the U.S. Through the National Sheep Improvement Program (NSIP), Rambouillet breeders seek to improve economically relevant traits. However, the parameters used in the NSIP genetic evaluation were last estimated two decades ago. Our aim was to re-estimate genetic parameters for body weight (BW), carcass, and wool traits. Data were provided by NSIP, which included BW at birth (BWT; n = 28,817), weaning [WWT; n = 5,633; age: 68 (SD 16) day], early post-weaning [PWTE; n = 23,303; 128 (SD 22) d], late post-weaning [PWTL; n = 7,689; 201 (SD 45) d] and as yearlings [YWT; n = 5,830; 375 (SD 33) d]. Yearling ultrasound scans of 12th rib backfat depth (YCF; n = 2,447) and eye muscle depth (YEMD; n = 2,457) were also available. Yearling wool traits were fiber curvature (YFC; n = 6,009), fiber diameter (YFD; n = 9,880), fiber diameter coefficient of variation (YFDCV; n = 8,803), greasy fleece weight (YGFW; n = 11,859) and staple length (YSL; n = 11,270). The pedigree consisted of 36,297 individuals. Animals with phenotypic records were progeny of 333 sires and 1,727 dams. A succession of univariate animal models was fitted. The most comprehensive model included direct and maternal additive genetic effects, their genetic covariance, and maternal permanent environmental and residual effects. Phenotypes were pre-adjusted for birth-rearing type category and, as covariates, dam age and age at recording. Contemporary group—a concatenation of flock, year, season, management group, sex, and, excluding BWT, recording date—was the only fixed effect fitted in the model. Model selection was based on the log-likelihood ratio test, and Akaike and Bayesian information criteria. The data structure, namely dams and their daughters and granddaughters contributing data, allowed reliable testing of the maternal effect terms. The direct-maternal genetic covariance did not explain variation for any trait (P > 0.18). The most parsimonious model for BW traits included direct and maternal additive genetic, and maternal permanent environmental, effects. For carcass and wool traits, only direct additive genetic effects were included in the final model. Such was unsurprising, as maternal effects often diminish as animals age. For the final models fitted (Table 1), direct heritabilities (± SE) for body weights ranged from 0.14 ± 0.01 (BWT) to 0.38 ± 0.04 (PWTL); the maternal heritabilities ranged from 0.04 ± 0.02 (PWTL; YWT) to 0.13 ± 0.01 (BWT). For carcass traits, direct heritabilities were 0.13 ± 0.04 (YCF) and 0.31 ± 0.05 (YEMD). For wool traits, they ranged from 0.37 ± 0.02 (YSL) to 0.58 ± 0.02 (YFD). These re-estimated parameter values are consistent with those used by NSIP, with the exception of PWTL (greater) and YSL (lower). With genomic data accumulating in Rambouillet, further refinements in parameter estimation are planned.

Sex-specific genetic parameter estimates of body weight in Mazandaran indigenous chickens.

Body weight is an economically important trait in poultry that shows sexual dimorphism (SD). In the present study, variation in SD in Mazandaran native chickens was investigated in terms of the (Co) variance components and genetic parameters of body weight between males and females. Studied traits were body weights at hatch (BW1), 8 weeks (BW8) and 12 weeks of age (BW12). Also, for weight at sexual maturity (WSM) covariance components were only estimated in females. Cross-sex direct and maternal correlations were also estimated for studied traits except for WSM. For this purpose, a deep 21-generation pedigree and body weight data (57,576 BW1, 72,925 BW8, 62,727 BW12 and, 42,496 WSM) were used. Evaluation of SD of body weight was performed using six bivariate animal models with and without considering the genetic and permanent maternal environmental effects under the restricted maximum likelihood method in WOMBAT software. Model with direct additive genetic effects and maternal genetic effects without covariance between them was identified as the best model for BW1 and BW8. The Model including direct additive genetic effects and permanent maternal environmental effects was the best model for BW12 and WSM. Direct heritability (h2 ) estimates for BW1, BW8 and, BW12 were, respectively, 0.05 ± 0.013, 0.17 ± 0.02 and, 0.25 ± 0.03 in males and, 0.05 ± 0.012, 0.15 ± 0.01 and 0.21 ± 0.01 in females. Also, the direct heritability of WSM based on univariate analysis in females was estimated to be 0.40 ± 0.01. Maternal heritability ( ) varied from 0.39 ± 0.01 (BW1) to 0.04 ± 0.009 (BW8) in males, and 0.36 ± 0.10 (BW1) to 0.04 ± 0.006 (BW8) in females. The correlation between direct genetic effects between males and females for BW1 was not significantly different from one. The direct genetic correlation between the two sexes for BW8 and BW12 was significantly different from 1 concluding that these traits are dimorphic in terms of direct genetic effects and therefore independent selection in both sexes is possible.

Genetic and nongenetic factors affecting body weight in Nili Ravi buffaloes

Live body weight of Nili Ravi buffaloes was studied to investigate the effect of certain environmental sources of variation such as herd, lactation number, lactation stage, season of recording and age of buffaloe at the time of recording alongwith appraisal of genetic parameters of body weight including heritabilities, genetic correlation and phenotypic correlation of body weight with mik yield. Five milking herds belonging to Nili Ravi buffaloe breed in Punjab were utilized in this study. Data recorded during 2010 to 2012 included 839 observations. Estimation of genetic parameters were carried out by Best Linear Unbiased Prediction (BLUP) procedure through ASREML set of coputer program. Least square mean for body weight was found as 523.13±81.63 with a coefficient of variation of 15.60%. Herd, stage of lactation, lactation number, recording season and buffalo’s age at the time of recording significantly affected live body weight. Univariate analysis of body weight indicated that heritability estimate for body weight was 0.33±0.07. Phenotypic correlations of body weight with milk yield in 305 days and milk yield on day of recording were found as 0.071±0.034 and 0.090±0.053 while genetic correlations were found as 0.16±0.00 and 0.20±0.00, respectively. High heritability and positive genetic correlation of body weight with milk yield suggested that body weight should be included in selection program for improved milk yield in Nili Ravi buffaloes.

Heritability and genetics correlations for body weight in escargots

The objective of this study was to estimate genetic parameters for body weight at 60 (P60), 90 (P90), and 120 (P120) days of age in escargots of the subspecies Cornu aspersum maximum, evaluating the influence of fixed and covariable effects on these traits. The data used were collected from escargots kept in a total confinement system. The significant fixed effects and covariates for these traits were tested in a general linear model by the F-test, considering a level of significance of 5%. Both the fixed effects of box and birth year and the quadratic effect of age of weighing as a covariate were significant (p < 0.05) for P60, P90, and P120. The Restricted Maximum Likelihood (REML) methodology was used to estimate (co)variance components and genetic parameters. High heritability for P60, P90, and P120 (0.38, 0.55 and 0.78, respectively) and high genetic correlations (0.58 to 0.77) among the traits were observed. The genetic parameters can be used as a basis for studies and practical applications to increase zootechnical indexes in this population.

Comparison of different models for the estimation of genetic parameters in tropical goats.

This study aimed to estimate the variance components and genetic parameters for body weight in tropical goats testing different models using Bayesian approach and investigate the effectiveness of fitting the effects of maternal genetic, permanent environmental, and covariance between direct and maternal effects. Records from 1980 to 2010 of 1453 Anglo-Nubian goats' herd were used. Six performance growth traits: birth weight (BW, kg), at 28 (W28, kg), 56 (W56, kg), 112 (W112, kg), 140 (W140, kg), and 196 (W196; kg) days of age, were evaluated. There was a negative covariance between direct genetic effects and maternal additive for all weights. The effect of maternal permanent environment is an important source of variation for performance characteristics in goats until the 196days, and must be considered in genetic evaluation models in order to obtain accurate predictions of breeding values of individuals. The importance of inclusion of the additive maternal effect appears to be more dependent on the structure of the data set under evaluation. Given the structure of the data, the described management and criteria for choosing the best model (deviance information criterion and the Bayes factor) should make the estimation of parameters for weights at birth and at 28 and 56days using model IV, since that will provide more consistent results than the type I (less complex), without the need of accurate representations of knowledge prior to data collection. Over time, the breeding program will have more data and thereby increase the possibility of building a prior distribution confident that would enable the inference of parameters for more complex models. However, these are preferable components for the estimation of the characteristics and weights to 112 at 140 and at 196days, using model I (less complex).

Estimation of genetic parameters of growth traits for direct and maternal effects in Murrah buffalo.

An understanding of genetic principles and environmental factors affecting the growth traits is essential to implement optimal breeding and selection programs. Early growth is an indicator of future success in production and reproduction status of dairy animals. In this study, a total of 18,989 records of body weight were used to estimate genetic parameters of body weight at birth (BW), 3months (3BW), 6months (6BW), 9months (9BW),12months (12BW), 18months (18BW), 24months (24 BW), 30months (3BW), and 36months (36BW) in Murrah buffalo at ICAR-NDRI Karnal, Haryana, for the period 1974-2019. The genetic parameters were estimated using the average information restricted maximum likelihood (AIREML) procedure by excluding or including maternal effects. Six analytical models were fitted in order to optimize the model for each trait. The most appropriate univariate model was selected based on the log likelihood ratio test (LRT). Influencing factors like calf sex, period of birth, season of birth, and dam's parity were investigated. The results showed that the maternal genetic effects, in addition to direct additive effects, were important for unbiased and accurate genetic parameter estimates of growth traits in Murrah buffaloes. Total heritability estimates h2T1 for BW, 3BW, 6BW, 9BW, 12BW, 18BW, 24BW, 30BW, and 36BW were 0.25, 0.04, 0.14, 0.16, 0.10, 0.15, 0.21, 0.24, and 0.23, respectively. Maternal effect was significant for birth weight and accounted for 13% variation through maternal genetic and 5% variability through maternal permanent environmental effect. Maternal genetic effect was also important for other traits. However, it interfered with the estimates of variance ratios in live weight traits owing to large and negative covariance between direct and maternal genetic effects. Direct genetic correlations between body weight traits were positive and high ranging from 0.10 to 0.94. Results revealed that the Murrah herd has a sizable genetic variability for growth traits and hence, there is sufficient scope for selection for achieving better growth rate if selection in this direction is applied. Owing to higher positive genetic correlation of 6BW with later ages, the scope of indirect selection for optimum growth in later ages can be aimed at by selecting animals for their higher 6-month live weight.

Profiles of genetic parameters of body weight and feed efficiency in two divergent broiler lines for meat ultimate pH

BackgroundSelection for feed efficiency is one of the best ways to decrease poultry production costs and environmental impacts. While literature on its genetic determinism is abundant, it is limited to one or a few periodic values over the animals’ lifespans. With the development of new phenotyping tools, kinetics of growth and feed intake are now available, providing access to daily data on feed efficiency. In this study, over the course of 6 weeks, we described the kinetics of body weight (BW), average daily weight gain (ADG), feed intake (FI), and daily cumulative feed conversion ratio (DCFCR) using electronic feed stations. We then estimated the genetic parameters of daily data in two fast growing lines of chicken divergently selected for breast meat ultimate pH (heritability and genetic correlations with breast meat yield and pH).ResultsBirds from the line selected to have a more acidic meat (pHu-), were more efficient than those selected to have a less acidic meat (pHu+), with a 4.3% higher BW from d7 to d29 and 5.0% better feed efficiency from d12 to slaughter. The line effect for ADG and DCFCR appeared to be significant as early as d5, which is consistent with the early age at which metabolic differences between the two lines appear. Genetic parameters estimated within each line revealed different genetic determinisms of growth and feed efficiency, with a higher impact of maternal effects on BW during the growing phase (d10 to d20) in the pHu+ line and much higher heritability values of DCFCR during the finishing phase (d26-d42) in the pHu- line.ConclusionGenetic profiles of daily performance highlighted the difference between both lines. Their behavior during dietary transitions reinforced the already known impact of these periods in the animals’ lives. Based on the profiles of genetic parameters within each line, it seems feasible to identify early criteria for selecting feed efficiency, but they must be defined for each line, as the genetic determinism of these traits is line-dependent.

First genetic evaluation of growth traits in Larimichthys polyactis to guide the formulation of selective breeding programs

Growth is an economically important trait in aquaculture. For the genetic improvement of growth traits in Larimichthys polyactis, a relatively new aquaculture species with great potential in large-scale farming, a genetic evaluation of these traits is necessary. In the present study, 34 families of L. polyactis were used to estimate genetic parameters for body weight, total length, and body length at the age of 11 months. Heritability estimates for the three growth traits including body weight, total length, and body length were 0.17 ± 0.06 to 0.23 ± 0.07 and were significantly different from zero (P < 0.05). The genetic correlation coefficients among the three traits were highly positive (i.e., 0.88–0.96). A selection ratio of 30% can result in an expected genetic gain (ΔG) of 3.41% and relative genetic gain (ΔG′) of 5.31% per generation for body weight in L. polyactis. There were significant differences in the response to selection when using parents selected by estimated breeding values (EBVs) and by phenotypic values (PVs). The concordance rate of individuals selected by the two methods was only 42.72%–46.02%. The average breeding value of the individuals selected based on EBVs (6.87 for body weight) was much higher than that for individuals selected based on PVs (3.48 for body weight). Environmental factors had a substantial impact on the growth phenotype of L. polyactis; accordingly, the EBV selection method is more efficient than the PVs method for breeding. The results of this study confirm that L. polyactis shows genetic variation for growth traits and highlight the enormous potential for improvements in growth by selective breeding based on EBVs.

Estimates of genetic parameters, principal components and cluster analysis for milk yield and body weight in Guzera cattle

Context The estimation of genetic parameters for traits related to the production of milk, beef or both may assist in defining the selection criteria and objectives of the breeding program, as well as in the identification and selection of genetically superior animals. Aims The objectives of this study were to estimate genetic parameters for body weight and 305-day milk yield of Guzera cattle and to perform cluster analysis on the basis of estimated breeding values for these traits, to identify groups of animals that could be selected for the production of beef, milk or dual purpose. Methods Body weights (N = 253 012) of males and females were ecorded at 120 days of age (BW120), at weaning (WW), at 365 days (BW365), at yearling stage (YW) and at 24 months (BW24), and 6237 complete lactations (MY305) of 4723 cows were used to estimate the genetic parameters. The bi-trait animal models included direct additive genetic, maternal permanent environmental and temporary random effects for body weights and additive genetic, permanent environmental and temporary environmental random effects for MY305. The fixed effects for all the traits were contemporary group and age of cow at calving. Key results The estimates of heritability ranged from 0.14 ± 0.01 for WW to 0.23 ± 0.01 for MY305. The genetic correlations between body weights at different ages and milk yield were positive and ranged from 0.27 ± 0.11 to 0.38 ± 0.19. Two principal components explained 86.74% of the total genetic variance among the traits. Conclusions Cluster analysis identified four different clusters and showed that the Guzera breed had bulls with different genetic patterns that permits genetic selection for beef, milk or dual purpose. Implications The genetic correlations of the present study suggest that selection to increase milk yield will lead to a slight genetic gain in the same direction for body weight at different ages, in contrast to reports from some other studies.

Estimation of Genetic Parameters for Body Weight and Some Colour Traits in the Seventh-generation Index Selected Nigeria Heavy Local Chicken Ecotype

Background: This study was conducted to estimate the genetic parameters of body weight and some colour traits in seventh generation (G7) index selected Nigerian Heavy Local Chicken Ecotype (NHLCE) progenies at point of lay to 12 weeks. Methods: 5 sires and 12 hens were used to generate the progenies used for the experiment. Traits measured included weekly body weight, egg colour, beak colour and feather colour. Data collected were subjected to one way analysis of variance in a Paternal half sib analysis using Animal model of SAS (2003). Four weeks body weight measurements, egg colour, beak colour and feather colour for 5 sires ranged from 1.29±0.05 1.54±0.07; 2.55±0.02 to 4.00±0.02; 2.45±0.02 to 4.83±0.02 and 1.73±0.02 to 4.58±0.04 respectively. Result: The new Duncan’s multiple range test shows that sire families are similar (p greater than 0.05) in the body weight and beak colour, but significantly differed (p greater than 0.05) in the egg colour and feather colour. The heritability estimates of mature body weight for week 3 was medium, while estimates of heritability for weekly mature body weight for weeks 1, 2 and 4, egg colour, beak colour and feather colour of NHLCE were low heritability. Low h2 of traits suggest that progeny and pedigree selection could be employed for improvement of the egg colour, beak colour and feather colour of NHLCE. The study showed positive genetic correlations between beak colour and egg colour, negative genetic correlations between beak and feather colour. This means that no decision can be taken in isolation as the selection of one trait will have consequences on other traits.

Inclusion of genomic information in estimation of genetic parameters for body weights and visual scores in Nelore cattle

ABSTRACT The aim of this study was to evaluate genomic information inclusion in genetic parameter estimation of standardized body weight at birth and at 240, 365, and 450 days of age, and visual scores for body structure, precocity, and body muscularity, measured as yearlings in Nelore cattle. We compared genetic parameters, (co)variance components (estimated from Bayesian inference and Gibbs sampling), breeding value accuracies, genetic trends, and principal component analysis (PCA) obtained through traditional GBLUP and ssGBLUP methods. For all traits [...]

The Estimation of Genetic Parameters for Body Weight, Body Dimension, and Carcass Traits in Four Egyptian Chickens Strains

The Estimation of Genetic Parameters for Body Weight, Body Dimension, and Carcass Traits in Four Egyptian Chickens Strains

Genetic and phenotypic parameters for body weights, harvest length, and growth curve parameters in American mink.

Understanding the genetics underlying growth curve is important for selection of animals with better growth potential, but little is known about the genetics of growth curve parameters in mink. This study estimated the genetic parameters for body weights (BWs), harvest length (HL), and growth parameters derived from the Richards model. For this purpose, individual BW of 1,088 mink measured seven times in 3-wk intervals (weeks 13 to 31 of life) were used for growth curve modeling using the Richards model. The BW traits included BW at week 13 (BW13), 16 (BW16), 19 (BW19), 22 (BW22), 25 (BW25), 28 (BW28), and 31 (BW31). Univariate analyses indicated that sex and birth-year had significant effects (P < 0.05) on BW, HL, asymptotic weight (α), growth rate at mature (k), shape parameter (m), weight at the inflection point (WIP), and age at the inflection point (AIP). In contrast, the color type had only significant effect (P < 0.05) on BW31 and HL. Estimated heritabilities (±SE) were ranged from 0.36 ± 0.13 (BW13) to 0.46 ± 0.10 (BW22) for BW and were 0.51 ± 0.09, 0.29 ± 0.09, 0.30 ± 0.09, 0.33 ± 0.1, 0.44 ± 0.10, and 0.47 ± 0.10 for HL, α, k, m, WIP, and AIP, respectively. The parameter α had non-significant (P > 0.05) genetic correlations (±SE) with k (−0.21 ± 0.23) and m (−0.10 ± 0.22), suggesting that changing shape parameters (k and m) will not influence asymptotic weight (α). Strong significant (P < 0.05) phenotypic (from 0.46 ± 0.03 to 0.60 ± 0.03) and genetic (0.70±0.13 to 0.88±0.09) correlations were observed between HL and different BW measures. The α, AIP, and WIP parameters had significant (P < 0.05) genetic correlations with HL indicated that selection for higher α, AIP, and WIP values would increase HL. Parameters k and m had nonsignificant (P > 0.05) genetic correlations with HL, indicating the change of the curve shape could not influence HL. Overall, the results suggest that growth curve parameters are heritable and can respond to genetic or genomic selection for optimizing the performance in mink.

Genetic parameters for production traits, resistance and resilience to Nematode parasites under different worm burden challenges in Corriedale sheep

Characterized as the most important gastrointestinal parasite (GIP) in the world, Haemonchus contortus is also the most predominant and pathogenic genus in Uruguay, causing high morbidity and mortality rates in sheep flocks. For approximately 26 years resistance to GIP has been included in the National Genetic Evaluation (NGE) of Corriedale and Merino breeds, using Faecal Egg Count (FEC) as the selection criterion. The aim of the present study was to estimate genetic parameters for FEC, post-weaning Body Weight (BW), Packed Cell Volume (PCV), FAMACHA© and Body Condition Score (BCS), to determine the possibility to include these traits in the NGE of GIP resistance and resilience, as complementary selection criteria and to investigate the sensitivity of breeding values to different environmental worm burden challenges. Data were collected on 19,510 lambs from 2000 to 2009 in 24 Corriedale studs that participated in the NGE of sheep in Uruguay. (Co)variances components were estimated using a multi-trait animal model performing a Bayesian analysis. Posterior means estimated for heritability (h2) were of low to moderate magnitude (between 0.10 and 0.33) for the traits analysed. Genetic correlations (rg) were not significantly different from zero for BW- Loge (FEC + 100), BW-FAMACHA©, BW-PCV, Loge (FEC + 100)-PCV, BCS-FAMACHA©, moderate favourable rg for Loge (FEC + 100)-FAMACHA and PCV-BCS (0.55, 0.41) and high favourable rg for BW-BCS (0.66). These results indicate the possibility to complement selection programs incorporating BW, Loge (FEC + 100), FAMACHA©, PCV and BCS in order to select resistant and resilient animal to GIP. Furthermore, genetic parameters for BW and Loge (FEC + 100) to different environmental worm burden challenge was investigated. Two contemporary groups of low worm environment (Loge (FEC + 100) below 6.40) and a high worm environment (Loge (FEC + 100) above 6.75) were considered. In this model, h2 estimated for BW and Loge (FEC + 100) were found to be not statistically different between low and high environmental worm burden, furthermore, high correlations between traits at both environments were also presented.

Evaluation of animal models for genetic analysis of growth performance in Landlly pigs

Selection of the most appropriate animal model for the estimation of genetic parameters for body weight was carried out using restricted maximum likelihood (REML) procedure at birth and thereafter at 3, 6, and 8 weeks of age in Landlly pigs. Six different models were fitted for each trait; by inclusion or exclusion of maternal additive genetic effect, maternal permanent environmental effect, and covariance between direct and maternal additive genetic effects. Records on 1968 piglets, born in 4 parities of 131 gilts/sows, sired by 68 boars during a period of 5 years from 2014 to 2018 were used. In order to determine the most appropriate model, Log likelihood values, log the likelihood ratio test and Akaike's information criterion were used. A model including direct additive genetic and maternal permanent environmental effects fitted best to data for birth weight. The best model explaining W3, W6, and W8 included direct additive genetic, maternal genetic and maternal permanent environmental effect with direct and maternal genetic covariance. Total heritability estimates for the body weights were low to moderate across best models.

Genetic correlations between body weight, daily weight gain, and semen characteristic traits in young Norwegian Red bulls

The aim of this study was to estimate genetic parameters for body weight (BW) at 150 d (Bw_150d), and 330 d (Bw_330d) of age and average daily weight gain (Dwg), and to estimate genetic correlations between these traits and semen characteristic traits: volume; concentration (Conc); motility in fresh, 24-h, and 48-h samples (Mot0h, Mot24h, Mot48h); and sperm defects. Data were collected at the performance test station of young Norwegian Red bulls from 2002 to 2012, before selection of bulls for artificial insemination. The weight and growth data consisted of observations for 3,209 bulls, and andrology information was available for up to 2,034 of these bulls. Genetic parameters were estimated using linear animal models. Models for BW and growth traits included the group and year the bull left the station and the pen they occupied during weighing (group-year-pen) and parity of their dam as fixed effects. Models for andrology traits had group-year, age in months (11 to 15), and the interaction between ejaculate number and days since previous collection included as fixed effects. Estimated heritability was 0.14 for Bw_150d, 0.26 for Bw_330d, and 0.34 for Dwg; the estimated genetic correlations among these traits were all favorable. Both BW traits correlated favorably with all the semen characteristic traits (0.20 to 0.76), whereas Dwg was favorably correlated with volume, Mot24h, Mot48h, and sperm defects, and unfavorably correlated with Conc (-0.25) and Mot0h (-0.53). Our results indicate that the genetic correlations between weight and growth traits and semen characteristics depend on the age of the bulls. Although most genetic correlations were favorable, selection for higher daily weight gain between 150 and 330 d might explain the slight negative genetic trends observed for semen characteristics in young Norwegian Red bulls.

GENETIC AND NON GENETIC PARAMETERS FOR BODY WEIGHTS OF TWO IRAQI LOCAL CHICKNS

This study aimed to investigate the genetic parameters for body weights of White and Black local chickens. The experiment conducted at College of Agric., Salahaddien Univ. during the period from Sept. 2016 until April 2018. 520 fertile eggs were taken from Agri. Res. Center, Ministry of Agric., Baghdad. Hatched chicks considered as parents (G0), and distributed randomly in to ten families. Resulted eggs from each family were collected during the peak of production for each generation to produce chicks of the next generation (G1 and G2). Body weights of resulted chicks were recorded at 1-day old and weekly till maturity. SAS program used to analyze the body weights (BW) and body weight gains (BWG) at different ages. The model includes genetic groups and generations for traits before sexing and the effect of sex added for the traits after sexing. Variance component of random effects estimated by REML and tested for positive definiteness to develop reliable estimates. Repeatability for body weights estimated. BW of chicks at 1 day, 4, 8, 9, 10, 16 and 17 week were 31.02, 292.47, 679.29, 794.58, 892.82, 1362.53 and 1252.17 g, and BWG at (1-4, 4-8, 9-10 and10-16) weeks were 261.45, 386.82, 98.24, and 469.51 g, respectively. The chicks of black group significantly excelled the white group in their weight at 1 day, 4, 8, 16 and 17, as well at ages 1-4 and 10-16 weeks. The effect of generation on BW of chicks at all ages and BWG at 1-4, 4-8 weeks was highly significant and (P&lt;0.05) during 9-10 and 10-16 weeks. Males surpassed females significantly (p&lt;0.01) in their BW at 9, 10 and 16 weeks and in their BWG during 9-10 and 10-16 weeks. Estimates of heritability were 0.42, 0.61, 0.76, 0.71, 0.43, 0.51, and 0.70 and of repeatability were 0.29, 0.26, 0.22, 0.38, 0.41, 0.74, and 0.78 for BW at 1 day, 4, 8, 9, 10, 16 and 17 weeks respectively. Higher (0.78) and lower (0.14) genetic correlations were recorded between BW at 8 weeks with each of BW at 10 and 17 weeks respectively. While the phenotypic correlations ranged between 0.04 (among BW at 1 day with weight at 9 weeks) and 0.58 (among BW 16 with 17 weeks).

Evaluation of body weight and hip height in Nellore cows in a tropical environment

The aim of this study was to evaluate random regression models to estimate genetic parameters for body weight and hip height in Nellore females and identify the best time to select these characteristics for adult size control. The dataset comprised 33,569 body weight and 31,804 height records from 3,860 and 3,487 females, respectively. Contemporary group and physiological state (for body weight analysis) were modeled as fixed effects, whereas age at birth (both linear and quadratic effects) and Legendre polynomials of age at (k = 4) as covariates. Random effects, including the additive genetic effects, and the animal permanent environment effect and the dam (for body weight analysis), were also included in the model. Random effects were modeled by Legendre polynomials of degree k in [3, 6], while residues were considered to be homogeneous or heterogeneous. The best model for body weight included heterogeneous residual variance with 21 classes and Legendre polynomials of degree k = 3, k = 6 and k = 1 for the additive genetic effects, animal and maternal permanent environment effects, respectively. The best model for hip height included homogeneous residual variance and Legendre polynomials of degree k = 4 and k = 3 for the additive genetic effects and animal permanent environment effect, respectively. Heritability estimates were moderate to high and suggest the studied characteristics could be used for maintaining cow size, being the selection at 3 years sufficient to get the desired size.

Genetic Parameters for Growth and Kid Survival of Indigenous Goat under Smallholding System of Burundi.

Simple SummaryGoats play a key multifunctional role in food security and poverty alleviation for small farmers in many less developed countries. Unfortunately, the productivity level of these goats is low. Among the alternatives proposed to overcome this situation, one is to establish a phenotypic breeding program with the support of community breeding organizations. In this study, genetic parameters were estimated for the growth, conformation, and survival of 1538 young goats raised by small farmers in Burundi organized in farmer field schools. Overall, the results suggest that phenotypic selection of growth and conformation traits would be possible if data recording and animal management were improved. On the other hand, efforts to improve survival should focus on improving the environmental conditions in which kids are raised. The role of community breeding organizations and animal health workers is therefore essential to disseminate breeding techniques and methods that optimize animal production and health.The goal of this study was to estimate genetic parameters for the growth, conformation, and survival of goat kids raised in smallholder farming systems in Burundi. To do this, measurements were taken on live weight, thoracic perimeter, length, and height at birth (n = 1538 animals), at 3 months (n = 1270 animals), at 6 months (n = 992 animals), at 9 months (n = 787 animals), and at 12 months (n = 705 animals). Kids were born between 2016 and 2019, from 645 dams and 106 bucks. Three bivariate animal models were used to estimate genetic parameters of body weight and conformation measurements as potential indicators of this weight. According to the measure, heritability was estimated between 15 and 17% and genetic correlations between 65 and 79%. An accelerated failure time animal model was used to estimate the heritability of survival for kids under one year, adjusted for birth weight. Goat survival was significantly prolonged by 0.64 days per kilogram of birth weight. The estimated heritability for this trait was 2%. Overall, these results suggest that a selection program could be implemented to improve animal growth, either directly on weight or indirectly on conformational traits. At the same time, efforts need to be made to improve rearing conditions to increase the survival of kids.

Genetic parameters for weights from birth to 10 years of age in different beef cow breeds

Context Most Brazilian beef breeding programs perform selection for young bodyweight, which will inevitably increase mature weight due to the genetic correlation among weights at different ages. Aims The objective of the present study was to estimate genetic parameters for bodyweight from birth to maturity in Gir, Guzerat, Nelore and Caracu cows born between 1981 and 2014 at Centro APTA Bovinos de Corte, Instituto de Zootecnia, Sertãozinho, São Paulo, Brazil. Methods The model included the fixed effects of contemporary group (herd and year of birth), month of birth and previous reproductive status (calved = 1, or not calved = 0), the linear and quadratic effects of animal and cow age as covariates, and direct additive genetic, maternal genetic and maternal permanent environmental effects as random effects. The genetic parameters were estimated by univariate analysis of weights adjusted at birth, and at 120, 210, 378, 450 and 550 days of age, and annually from 2 to 10 years. In addition, multivariate analysis was performed considering weights at birth, and at 210 and 550 days, and at 5 years of age for all breeds. Key results For the different breeds, the heritability estimates ranged from 0.28 to 0.49 for birthweight, from 0.11 to 0.31 for weaning weight, from 0.25 to 0.43 for yearling weight, and from 0.25 to 0.69 for weights from 2 to 10 years of age. The genetic correlations were high and positive, indicating that selection at any age will affect weights at the other ages. Conclusions The results suggest the possibility of genetic progress for weights at different ages and the use of the young weights to monitor the mature weight of the animals. Implications As the trait most strongly correlated with mature weight was yearling weight, already used as the selection criteria for females in the breeding program of the Instituto de Zootecnia, selection indexes should be derived to keep the mature cow weight constant, since heavier cows could be undesirable for pasture-based Brazilian production systems.