Heritability Estimates For Birth Weight Research Articles

Preliminary outcomes on phenotypic and genetic parameter estimates for body weight of indigenous Tswana goats in Botswana

The aims of this study were to estimate the genetic and phenotypic parameters for growth traits and evaluate genetic trends on 585 indigenous Tswana goats. The population was maintained under low input production system at the Department of Agricultural Research in Lesego ranch, Botswana, from 2005 to 2008. Data included birth weight (BW), weaning weight (WW), weight at 8 months (PW), yearling weight (YW), pre-weaning average daily gain (ADG) and two post weaning average daily gains (ADG2 and ADGYW). Data was analysed using general linear model of SAS to determine non-genetic effects. Estimation of genetic and phenotypic parameters were estimated using ASREML fitting an animal model that accounted for fixed effect of parity, sex, type of birth and year of birth. Least squares means for BW, WW, PW and YW were 2.88 ± 0.03, 12.15 ± 0.17, 16.52 ± 0.28 and 21.04 ± 0.32Kg, respectively, while those for ADG, ADG2 and ADGYW were 74.52 ± 1.41, 28.78 ± 1.55 and 33.66 ± 2.28 g/day, respectively. Estimates of heritability for BW, WW, PW and YW were 0.79 ± 0.11, 0.63 ± 0.14, 0.32 ± 0.13 and 0.48 ± 0.16, respectively. The genetic correlations for all the traits studied were positive and moderate to high (0.48 to 0.82) whilst phenotypic correlations ranged from 0.21 to 0.72. Positive average genetic trends of 12.32% (WW), 13.39% (PW) and 7.38% (YW) were attained. The results have demonstrated the potential of this breed to be improved through selection.

Estimation of genetic parameters as well as trends for growth traits in Harnali sheep

The current study focussed on the growth traits pertaining to Harnali sheep maintained at Sheep Farm, LUVAS, Hisar and data were recorded from pedigree sheets of 1278 animals. Growth traits considered were birth weight (BW), weaning weight (WW), six-month weight (6MW), yearling weight (YW), and pre-weaning average daily gain (PRWDG) and least-squares means for corresponding traits found to be 3.28±0.02 kg, 12.89±0.07 kg, 17.06±0.06 kg, 24.36±0.06 kg, and 106.74±0.61 g, respectively. Effect of different factors like period of birth, sex of animal and dams’ weight at lambing was studied on growth traits. Except YW, significant effect of period of birth was observed on all the growth traits. Sex had significant influence on BW only however, dams’ weight at lambing affected significantly all the considered growth traits except YW. By leveraging the sire component of variance and covariance from mixed model analysis, the paternal half-sib correlation method was used to estimate genetic as well as phenotypic parameters. Estimates of heritability for BW, WW, 6MW, YW and PRWDG were 0.28±0.07, 0.33±0.07, 0.31±0.07, 0.12±0.04 and 0.27±0.06, respectively. Genetic as well as phenotypic trends for WW and PRWDG were found to be positive. Moderate range of genetic variability at weaning weight and its positive genetic and phenotypic correlations with growth traits specially six month’s weight indicated that genetic improvement could be possible through early selection at weaning weight in Harnali sheep.

Development of selection strategies for genetic improvement in production traits of Mecheri sheep based on a Bayesian multi trait evaluation

The progression of genetic selection techniques to enhance farm animal performance traits is guided by the present level of genetic variation and maternal impact in each trait, as well as the genetic association between traits. This study was conducted on a population of Mecheri sheep maintained from 1980 to 2018 at Mecheri Sheep Research Station, Pottaneri, India, to determine variance and covariance components, as well as genetic parameters for various production performance traits. A total of 2616 lambs, produced by 1044 dams and 226 sires, were examined in the study and the production traits of Mecheri sheep assessed include birth weight (BW), weaning weight (WW), six-month weight (SMW), nine-month weight (NMW), and yearling weight (YW). The Bayesian approach, using the Gibbs sampler, analyzed six animal models with different combinations of additive direct and maternal additive effects. Direct genetics, maternal genetics, and residual effects models were the major contributors to total phenotypic variation for all the production traits studied. Direct heritability estimates of birth weight, WW, SMW, NMW, and YW were 0.25, 0.20, 0.12, 0.14, and 0.13, respectively. The maternal heritability estimated for BW, WW, SMW, NMW, and YW were 0.17, 0.10, 0.12, 0.14, and 0.14, respectively. The maternal effects had a major impact on the pre-weaning production traits. The genetic correlations estimated between different pairs of production traits studied ranged from 0.19 to 0.93. The body weight at birth exhibited a higher genetic relationship with weaning weight than post-weaning growth characteristics, and the genetic correlation between weaning weight and post-weaning attributes was moderate to high (0.52 to 0.72). Based on the additive genetic variance in weaning weight and the correlation estimates of weaning weight with post-weaning traits, weaning weight was proposed as a selection criterion for improving growth traits in Mecheri sheep.

Estimates of (co)variance components and genetic parameters for pre-weaning body weight traits and Kleiber ratio in Sangsari sheep breed

The current study aimed to estimate (co)variance components and heritability for pre-weaning body weight traits and Kleiber ratio in Sangsari sheep. Data used in this research were collected over 30 years (1986–2016) at the breeding station of Sangsari sheep. Traits considered were birth weight (BW), weaning weight (WW), pre-weaning daily gain (PWDG), and Kleiber ratio (KR). Genetic parameters were estimated by the average information restricted maximum likelihood (AI-REML) procedure, using six animal models. The most suitable model was selected using the Akaike information criterion (AIC) for each trait. Direct heritability estimates for BW, WW, PWDG and KR were 0.30 0.04, 0.20 0.03, 0.15 0.02, and 0.13 0.05, respectively. Maternal heritability estimates varied from 0.06 0.02 for PWDG to 0.12 0.03 for BW. The maternal permanent environmental effects for the traits of KR, WW and PWDG account for about 7%, 9% and 12% of the phenotypic variance. The estimates of the direct genetic () and maternal genetic () correlations among pre-weaning growth traits were positive and ranged from 0.21 (BW-KR) to 0.98 (WW-PWDG) and 0.27 (WW-PWDG) to 0.48 (BW-WW), respectively. Therefore, to have an accurate genetic evaluation, maternal effects need to be considered in any program aimed at improving pre-weaning growth traits. In addition, due to the existence of genetic variation for early growth traits and generally positive and medium to high genetic correlations among them, it can be concluded that in the Sangsari breed of sheep, genetic progress for these traits is possible by selection. HIGHLIGHTS Genetic parameters (direct and maternal heritability) were estimated for the Sangsari breed of sheep. The low to moderate estimate of heritability for pre-weaning body weights and Kleiber ratio indicate that genetic improvement of these traits is possible by selection. Considerable genetic correlations among early body weights, pre-weaning daily weight gain, and Kleiber ratio in Sangsari sheep were estimated.

Meta-analysis of genetic parameters for traits of economic importance for beef cattle in the tropics

Previous genetic and economic evaluation of beef cattle breeding programmes have used genetic and phenotypic parameter estimates obtained in different studies. Such parameters are heterogeneous because they are obtained from different locations, using different sample sizes and estimation methods. The consequence of using such parameters is underestimation or overestimation of potential genetic gains, leading to wrong investment decisions. The objective of the current study was to estimate consensus genetic and phenotypic parameter estimates for beef cattle in the tropics. Meta-analysis of productive, reproductive, adaptation and disease resistance traits was done to obtain weighted traits means, heritabilities, and genetic and phenotypic correlations. Estimates from 208 means, 119 direct and 50 maternal heritability, 42 direct genetic and maternal genetic correlations, 136 genetic and 93 genetic and phenotypic correlations, respectively, were used. A random effect model was used to include the variances within and between studies. Unweighted average direct heritability estimates ranged from 0.26 to 0.32, 0.08 to 0.40, 0.14 to 0.34, 0.18 to 0.67 and 0.30 to 0.35 for growth, reproduction, disease resistance, adaptation and carcass traits, respectively. Weighted heritability estimates for birth weight, weaning weight and yearling weight ranged from 0.18 to 0.26, while those for reproduction traits ranged from 0.02 to 0.09. Weighted maternal heritability estimates for growth traits ranged from 0.07 to 0.11. Carcass, disease resistance and adaptation traits were the least studied despite their great economic importance to beef production in the tropics. Direct maternal heritability estimates for birth, weaning and yearling weights were 0.26, 0.24 and 0.18, while the corresponding maternal heritability estimates were 0.07, 0.11 and 0.08, respectively. Genetic and phenotypic correlations for body weights ranged from 0.43 to 0.88 and 0.32 to 0.80, respectively. Yearling weight and final weight had the highest genetic correlation (0.88). The genetic correlations between body weights and growth rates were moderate to high (0.37 to 0.79). Weaning weight was negatively correlated with post-weaning daily gain (-0.12). Disease resistance traits had low to negative genetic correlations with body weight and growth rate traits (-0.06 to 0.01). Some traits reviewed in the current study were not given a lot of attention, and therefore more focus is required on disease resistance, adaptation and carcass traits. In spite of these limitations, the weighted parameter estimates reported here can be used to add value to beef cattle improvement programmes in the tropics.

Multi trait genetic evaluation of growth traits in Nellore sheep raised on pasture in semi-arid regions of India using Bayesian approach

Abstract The main aim of this study is to estimate genetic parameters and (co) variance components for body weights at various ages in Nellore sheep born during the period from 1993 to 2016 (23 years). A total of 4822 lambs with pedigree descended from 144 sires and 1299 dams were included in this study. Bayesian analysis using Gibbs sampler multi trait animal model with and without maternal effects was studied. Traits included in this study were birth weight (BW), weaning weight (WW), six months body weight (6MW), nine months body weight (9 MW), Yearling weight (YW). Year-season of birth and sex of lamb (contemporary groups) were considered as fixed effects with ewe weight at lambing as a covariate. Estimates of direct heritability estimates for birth weight, WW, 6MW, 9MW and YW based on best model were 0.17, 0.28, 0.27, 26 and 0.23, respectively and the corresponding maternal heritability estimates were 0.12, 0.14, 0.14, 0.12 and 0.13, respectively. The direct-maternal genetic covariance was negative for all the studied traits. Strong and positive estimates of direct additive genetic correlations were observed in growth traits and they ranged from 0.16 to 0.83, whereas the direct-maternal genetic correlations were negative for all the traits and these estimates ranged from ˗0.89 to ˗0.08. Moderate estimates of heritability for the growth traits obtained in this study suggested the presence of better genetic variability and the possibility for genetic improvement of Nellore sheep through selection. Maternal genetic effects were significant in all the traits. Hence, it is recommended to incorporate these effects in the genetic analysis by including it as a genetic or environmental effect or both. The environmental variance obtained in the study suggested that the growth performance of Nellore sheep may be enhanced by improving the feeding and management aspects. Correlations among traits and effects should be considered while implementing breed improvement program.

Genetic Parameters of Birth Weight and Weaning Weight and Their Relationship with Gestation Length and Age at First Calving in Hanwoo (Bos taurus coreanae).

Simple SummaryHanwoo cattle is considered one of the most economically important species and sources of nutrition for Koreans. Thus, both the reproductive performance and growth traits play an important role in the continuous development and productivity of Hanwoo farming. Therefore, to improve beef production and the profitability of Hanwoo farming, estimations of genetic parameters for birth weight (BW) and weaning weight (WW) and their relationship with age at first calving (AFC) and gestation length (GL) are necessary to understand and improve their responses to selection. Thus, this study estimated the variance components, heritability estimates of birth weight (BW) and weaning weight (WW) and their genetic and phenotypic relationship to age at first calving (AFC), and gestation length (GL). Results revealed a moderate and high heritability estimate for BW and WW, which suggests a sluggish and rapid response of these traits to selection, respectively. The moderate and high genetic correlation between BW and reproductive traits (AFC and GL) revealed that the selection of a heavier BW might result in a longer AFC and GL. Although the genetic correlation for BW and AFC was moderate and positive, the phenotypic correlation of close to zero may indicate that the phenotypic expression for these traits is likely to be influenced by the genotype-environment interaction (GxE). Moreover, the genetic and phenotypic correlation between WW and reproductive traits (AFC and GL) indicates that the selection of a heavier WW may not influence the AFC and GL of Hanwoo cow. These estimated genetic parameters and correlations for the studied traits can be utilized for genetic breeding programs of Hanwoo cattle.Hanwoo is one of the most economically important animal species in Korea due to its significant contribution to nutrition. However, the current selection index only focuses to improve carcass traits of Hanwoo. Thus, this study aimed to estimate the genetic parameters of birth weight (BW) and weaning weight (WW) and their genetic and phenotypic relationship to the age at first calving (AFC) and gestation length (GL) of Hanwoo. The genetic parameters for birth weight (BW) and weaning weight (WW) were estimated using the data obtained from 52,173 and 35,800 Hanwoo calves born from February 1998 to March 2017, respectively. Further, these data were used to determine their genetic and phenotypic correlation to age at first calving (AFC) and gestation length (GL). The heritability estimates of BW and WW and correlation coefficients were obtained using the average information restricted maximum likelihood (AIREML) procedure, fit in single and two-trait linear animal models. The estimated direct heritability for BW and WW was moderate (0.22 ± 0.02) and high (0.51 ± 0.03), respectively, while the maternal heritability for both traits was 0.12 ± 0.01 and 0.17 ± 0.01, respectively. The genetic correlation of BW and reproductive traits (AFC and GL) showed a moderate and high positive correlation coefficient of 0.33 ± 0.06 and 0.53 ± 0.02, respectively, while close to zero and low positive phenotypic correlations of 0.06 ± 0.01 and 0.21 ± 0.06 were also observed between the correlated traits, respectively. For the correlation analysis between WW and AFC, both the genetic and phenotypic correlation showed close to zero values of 0.04 ± 0.06 and −0.01 ± 0.01, respectively. Meanwhile, the genetic and phenotypic correlation between WW and GL showed low and negative correlations of −0.09 ± 0.06 and −0.09 ± 0.01, respectively. These obtained estimated variances for BW and WW and their corresponding genetic and phenotypic correlation to AFC and GL can be used as information for genetic improvement and subsequent economic improvement of Hanwoo farming.

Estimation of genetic parameters for production and reproduction traits in Kashmir Merino sheep

Data pertaining to 6,300 birth records spread over 21 years of Kashmir Merino sheep maintained at Government Sheep Breeding Farm Kralapathri and Government Sheep Breeding Farm Goabal Kashmir and Fleece Testing Laboratory were used to estimate the genetic parameters. The genetic parameters for birth weight (BWT), 6 months body weight (6-MWT), yearling body weight (12 MWT), greasy fleece yield of first clip (GFY-1), greasy fleece yield of second clip (GFY-2), fiber diameter (FD), staple length (SL), age at first lambing (AFL) and inter-lambing period (ILP) were estimated by paternal half-sib correlation method using sire components of variance and covariance. The heritability estimates for BWT, 6-MWT, 12-MWT, SL, GFY-1, GFY-2 were moderately high whereas the estimates of heritability for FD, SL, AFL and ILP were low respectively. The genetic correlation between different traits ranged from - 0.73±0.10 to 0.87±0.04 while as phenotypic correlation different traits ranged from - 0.66±0.07 to 0.54±0.01. Keeping in view its high heritability of SMW and favorable correlations with birth weight, yearling body weight, wool traits and age at first lambing, it is concluded that selection on basis of 6-MWT would be effective to improve growth, quality wool production and age at first lambing in Kashmir Merino sheep.

Genetic evaluation of growth performance of kashmir merino sheep

A study was conducted to evaluate the growth performance of Kashmir Merino sheep at two Government Sheep Breeding Farms (Kralapathri and Goabal) in Kashmir using 6299 birth records spread over 21 years (1997 to 2017). Mixed linear model with sire as a random effect and year, sex, birth type, parity and farm as fixed effects were used for analysis. The overall least squares means for birth weight (BW), six months body weight (W6), average daily gain from birth to six months (ADG1), metabolic weight at six months (W6 0.75), Kleiber ratio from birth to six months (KR1), yearling bodyweight (W12), metabolic weight at yearling age (W12 0.75), average daily gain from six month toyearling age (ADG2) and Kleiber ratio from six months to yearling age (KR2) were 3.26±0.06 kg, 18.74±0.47 kg, 84.60±2.63 g, 8.96±0.17kg, 9.27±0.12, 21.75±0.66 kg, 10.03±0.23kg, 22.21±3.01 g and 2.11±0.25, respectively. The effects of year and sex of animal were significant (P<0.01) whereas, effect of birth type (except BW) and farm was non-significant for all the traits. The effect of parity was significant on the BW, W6, W6 0.75, KR1 and W12. The estimates of heritability for BW, W6, ADG1, W60.75, KR1, W12, W120.75, ADG2 and KR2 were 0.64±0.07, 0.54±0.07, 0.54±0.06, 0.55±0.06, 0.54±0.07, 0.60±0.09, 0.69±0.09, 0.50±0.08 and 0.59±0.08, respectively. The genetic, phenotypic and environmental correlations ranged from low to high. The high heritability estimates of traits under study indicated existence of genetic variance which can be utilised to improve growth performance and feed efficiency conversion of Kashmir Merino sheep. To reduce the generation interval, 6 month body weight (high heritability and high genetic correlations with other traits including 12 month weight) canbechosenas aselection criterion.

Genetic and non-genetic factors influencing birth weight in the Tuli cattle breed of Zimbabwe

Genetic and non-genetic factors were estimated for birth weight in the Tuli cattle breed of Zimbabwe. Performance records ( n = 1154) were obtained from the Livestock Identification Trust (LIT) for the period (2008–2014) for three farms; X ( n = 494), Z ( n = 143) and Y ( n = 517). We used the Restricted Maximum Likelihood (REML) for fitting the Sire model. The model used the farm, season, sex, year and dam age as fixed effects while the sire was fitted as a random variable. Best Linear Unbiased Prediction (BLUP) was used to predict breeding values (BVs). The mean birth weight was (30.89±0.128). Wet season had higher birth (31.62±0.27) weight than dry season (30.62±0.144); however, the difference was not statistically significant. The other factors, farm, sex, year and dam age had a significant effect (P &lt;0.05) on birth weight. Heritability and repeatability estimates were 0.44 and 0.35, respectively. Based on the results, the high heritability estimate for birth weight suggests that the trait responds well to selection. Sire breeding values ranged from -4.400 to 6.845 with the majority of sires between -2 and 2, showing that there was stabilising selection over the years to minimise both overweights and underweights.

Pendugaan nilai heritabilitas sifat pertumbuhan pada Sapi Madura

Madura, a local cattle breed in Indonesia, is included as a national genetic resource. Genetic evaluation for growth traits in Madura cattle is important for appropriate utilization and improvement of this breed. The aim of this study was to estimate the heritability for growth traits in Madura cattle. The method used in this study is a data recording from 2010 until 2016 including birth weight (190 animals), weight at day 205 (155 animals) and weight at day 365 (135 animals) were used for heritability estimates by using paternal half sib correlation . The results showed that heritability estimates for birth weight, weight at day 205 and weight at day 365 were 0.38±0.17; 0.64±0.22 dan 0.54±0.18. Estimates of heritability for growth traits in Madura cattle ranged between medium and high. In conclusion,growth traits can be used as selection criteria for future genetic improvement in Madura cattle.

Growth curves and genetic parameters in Nelore animals estimated by random regression models

The objective of this work was to estimate growth curves and genetic parameters from birth to 650 days of age of Nelore cattle raised in pasture in two production regions of the Mato Grosso do Sul State, Brazil (233,835 weight records from 47,459 cattle were analyzed). Genetic parameters were determined by random regression using Legendre orthogonal polynomials of cubic order, and age at weighing was considered in the model as a fixed effect to model the average growth trajectory. In the models, the effects of the contemporary group were considered as fixed and, as covariates, the animal age at weighing and the cow age at calving were nested in the animal age class (linear and quadratic effects), forming eight age classes. All models included the direct genetic additive, maternal genetic, and animal permanent environment as random effects, and the most appropriate model to describe the studied effects was defined according to the AIC and BIC criteria. Heritability estimates for birth weight varied between the two production regions, Campo Grande-Dourados (R1) and Alto Taquari-Bolsão (R2) and R1 (0.36 ± 0.02) and R2 (0.28 ± 0.03), and there were variations in the estimates at advanced ages. In both regions, the highest heritability values at 650 days of age were 0.47 ± 0.03 and 0.65 ± 0.02 for R1 and R2, respectively, with high heritability reflecting the high values of additive genetic variance. The random regression methodology was efficient in estimating growth curves and genetic parameters. Growth curves were different when they were estimated separately by sex, birth season, and production region. Genetic parameters estimated separately by region indicate differences in additive genetic variance, maternal additive, and animal permanent environment for weights up to 650 days of age.

Phenotypic and Genetic Parameters Estimation For Birth Weight in Zebu and Crossbred Calves Born Under Organized Farm Conditions in India

Abstract Data on birth weight of Zebu (Sahiwal and Tharparkar) and Crossbred (Holstein Friesian X Tharparkar) cattle spread over 16 years were utilized to assess the influence of genetic and environmental factors on calf birth weight, and to estimate variance components and genetic parameters. Non genetic factors taken into consideration were season of birth, period of birth, sex of the calf, damÂ’s parity and gestation period. Least squares means for birth weights of Sahiwal (S), Tharparkar (TP) and crossbred (CB) cattle was 19.92 ± 0.18, 20.91 ± 0.25 and 28.29 ± 0.29 kg respectively. All the non genetic factors, except period of birth (Sahiwal) and gestation period (Tharparkar), included in the study had a significant effect on birth weight of calves in all the three breeds. Heritability estimate for birth weight by paternal half-sib method on 1520 progeny from 48 sires was 0.149 ± 0.055 in Sahiwal, whereas on 2360 progeny from 101 sires was 0.323 ± 0.063 in crossbred. Variance components and genetic parameters due to direct additive genetic and maternal additive genetic effects were estimated by using two univariate animal models (Model 1 and 2) using AIREML algorithm of WOMBAT software. Model 1 produced highest estimate of additive genetic variance (3.65 Kg2, 3.90 Kg2 and 15.38 Kg2 for Sahiwal, Tharparkar and crossbred respectively) and direct heritability (0.57, 0.60 and 0.67 for Sahiwal, Tharparkar and crossbred respectively) in all the three breeds. When maternal influence was included in the Model 2, the direct heritability (h2d) estimate were 0.14, 0.55 and 0.34 and the maternal heritability (h2m) estimate for birth weight were 0.19, 0.16 and 0.13 in Sahiwal, Tharparkar and crossbred respectively. Model 2 was better in estimation of variance components of birth weight for all three breeds because of significant improvement in likelihood value.

Genetic analysis of growth traits in Harnali sheep.

Aim:The present investigation was to study genetic characteristics of Harnali sheep with respect to growth performance and to estimate genetic parameters.Materials and Methods:The 22 years (1992-2013) data of growth traits of a 1603 synthetic population of Harnali sheep maintained at Lala Lajpat Rai University of Veterinary and Animal Sciences, Hisar, was utilized for this study. A mixed methodology with regression on their dam's weight was used to study the effect of non-genetic factors on growth traits. Heritability, genetic and phenotypic correlations were estimated using paternal half-sib analysis for body weight at various ages and average daily gain (ADG) for different growth periods.Result:The overall least squares mean of body weights recorded for birth weight (BW), weaning weight (WW), six months body weight (SMW), one yearling body weight (YBW), average daily gain from birth to 3 months (ADG1) and average daily gain from 3 to 12 months (ADG2) were 3.35±0.05 kg, 12.41±0.08 kg, 16.30±0.12 kg, 21.88±0.08 kg, 100.66±0.86 g/day and 35.07±0.39 g/day, respectively. The effects of year of birth significantly (p<0.01) influenced the BW, WW, SMW, YWB, ADG1 and ADG2. The effects of sex of lamb significantly (p<0.01) influenced the BW, WW SMW, YWB, ADG1 and ADG2. The effects of dam's weight at lambing significantly (p<0.01) influenced BW, WW, SMW, YWB, ADG1 and ADG2. No definite trend was observed over the years for the averages of body weight and gain. The heritability estimates of BW, WW, SMW, YBW, ADG1 and ADG2 were 0.40±0.05, 0.38±0.05, 0.45±0.06, 0.29±0.05, 0.40±0.06 and 0.33±0.02, respectively. The male lambs were significantly heavier than females at all stages of growth. The heritability estimates were moderate for all the growth traits and high genetic correlations of BW and WW with SMW were found.Conclusion:Due to high heritability and positive correlations of SMW with other body weights and daily gain, it was concluded that selection on the basis of SMW would be the best approach to improve growth performance in Harnali sheep.

Variance components and genetic parameters of growth traits and Kleiber ratio in Muzaffarnagari sheep

Estimates of (co)variance components and genetic parameters were obtained for birth weight (BW), weaning weight (WW), average daily weight gain from birth to weaning (ADG) and Kleiber ratio (KR) of Muzaffarnagari sheep maintained at the Central Institute for Research on Goats, Makhdoom, Mathura, India, over a period of 30 years (1976–2005). Records of 5835 lambs descended from 176 rams and 1703 ewes were used in the study. Analyses were carried out by restricted maximum likelihood (REML) fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Six different animal models were fitted for all traits. The best model was chosen after testing the improvement of the log-likelihood values. Direct heritability estimates were inflated substantially for all traits when maternal effects were ignored. Heritability estimates for BW, WW, ADG and KR were 0.15, 0.16, 0.15 and 0.13, respectively. Maternal genetic effects contributed only 12% of the total variance for birth weight. Estimates of fraction of variance due to maternal permanent environmental effects (c2) for BW, WW, ADG and KR accounted for 6–12% of the total phenotypic variance in this study. The estimates of the direct genetic correlation among studied traits were positive, ranging from 0.18 (BW–KR) to 0.98 (WW–ADG), whereas permanent maternal environmental correlations among traits varied from from 0.55 (BW–KR) to 0.99 (WW–ADG). The estimates of the phenotypic and environmental correlation between traits under study ranged from 0.10 to 0.99 and −0.05 to 0.99, respectively. Results suggest that maternal additive effect was only important for birth weight whereas permanent environmental maternal effects were important for other traits in our study. The moderate heritability estimates for early growth traits and Kleiber ratio of sheep in this study indicates that modest rates of genetic progress may be possible for these traits from selection under the prevailing management system.

Growth Traits and Estimated Heritability by Variance Component for Dhofari Calf Breed

Dhofari calf breed weight variations at similar age indicate their potentiality for genetic improvement by careful selection. The present study was carried out to find the average growth traits of birth weight (BW), weaning weight(WW), yearling weight(YW), pre-weaning daily gain(PRE), post-weaning daily gain(POS) and the effect of dam age, season, sex, and year of birth on the variance of these traits. In addition, the estimated heritability of these traits by estimating the (co)variance components was the second objective of this study. Data of 556 Dhofari breed calves from Salalah Livestock Research Station were used and statistically analyzed by SPSS, GLM, Duncan test and Linear Mixed model with restricted maximum likelihood (REML). Average of growth traits for birth weight (BW), weaning weight (WW), yearling weight (YW), pre-weaning daily gain (PRE), and post-weaning daily gain (POS) were 17.83 ±0.10, 85.11 ±0.60, 160.27 ±1.30 kg, 639.30 ±5.20, and 235.69 ±5.86 g/d respectively. Phenotypic Pearson correlation analysis of growth traits showed high significance (P 9 years old), season (spring), and sex (males) for all growth traits. Analysis of estimated variance components revealed heritability estimates for BW, WW, YW, PRE, and POS of 0.23 ±0.80, 0.41 ±0.86, 0.58 ±0.93, 0.40 ±0.85, and 0.59 ±0.92 respectively.

Genetic Parameter Estimates for Growth and Reproductive Trait of Sheep for Genetic Improvement and Designing Breeding Program in Ethiopia: A Review

Small ruminants in general and sheep in particular are important investments in the highlands of Ethiopia. Genetic and environmental improvements offer an opportunity to increase production from existing animal resources. Development of effective genetic evaluation and improvement programs requires knowledge of the genetic parameters (genetic variance of each trait and covariance among traits) for economically important production traits. Direct heritability estimates for birth weight of Afar sheep (0.13 to 0.38) and BHS (0.20 to 0.58) using univariate analysis; for Horro sheep (0.18 - 0.32) and Menz sheep (0.46) by fitting a multi-trait individual animal model. The weaning weight direct heritability estimates for sheep in Ethiopia, Afar sheep (0.11 - 0.37) and BHS (0.00 - 0.29), Horro sheep (0.10 - 0.26) and Menz sheep (0.48). Fertility, litter size and lamb survival are the components of the overall ewe reproduction traits. It appears that heritability estimates of these traits are rather low and reflect the generally small genetic variance for most reproductive traits. Moreover, litter size has a higher heritability (0.16 - 0.19) than the other components traits like fertility (0.10) and survival rate (0.07 - 0.09) for Awassi sheep breed. Genetic correlations among most pairs of traits were higher than the corresponding phenotypic correlations. Live weights measured at successive ages were highly correlated, ranging from 0.61 to 0.98 for Menz sheep. Genetic correlations were also high between pre-weaning daily gain and weaning weight for Afar and BHS sheep. Except for Blackhead Somali sheep breed which has high genetic correlation between birth weight and weaning weight, Horro, Menz and Afar sheep have high genetic correlation between post-weaning weight traits. This indicates that selection for one trait improves the other trait in those sheep breeds. In order to develop alternative improvement program for sheep breeds in Ethiopia, estimates of genetic parameters for economical growth and reproduction traits should be done by designing experiments since the information on most sheep breed is nonexistence.

Various factors influencing birth weight in animal production

This is a review article that looks at various factors that influence birth weight in animal production. Birth weight is an important indicator of potential growth of an animal and is affected by both genetic and non-genetic factor, and the birth size depends on their interaction. Environmental conditions such as kind and quality of feed and details of management may have an influence on birth weight in livestock production. In order to minimize the adverse effects of factors that influence birth weight, it is perhaps important to understand the implications of different mechanisms, how and why they affect birth weight. Low birth weight than optimum is the main factor that determine the pre weaning losses of young ones and large birth have been associated with difficult birth. Traditional measures to ameliorate birth associated negative effects should also focus on maternal dietary manipulation which may influence optimum birth weight. Nutritional programs designed to improve dam’s body condition during pregnancy will have a positive influence on birth weight of progeny. A good knowledge of genetic parameters is essential to develop accurate selection indices and to optimally design breeding programs and performance recording systems for maximum economic gain or profit from growth traits. Estimates of genetic parameters for birth weight is model dependent and ignoring of maternal genetic effect in the model leads to overestimation of direct heritability for birth weight. Estimates of direct and maternal heritability for birth weight in different species have been reported and vary from low to high. The review article therefore, concludes that the large variability of birth weight in livestock species suggests that many factors or conditions may be responsible for this variation. The reported low heritability estimates for birth weight may be explained by the poor nutritional levels of dams creating a large environmental variation.

Estimation of genetic parameters for growth traits in Brangus cattle

A combination of multiple trait and repeatability models were used to estimate genetic parameters for birth weight (BW), weaning weight (WW), yearling weight (YW), eighteen month weight (FW) and three measurements of mature weight (MW) using 23 768 records obtained from the South African Brangus Cattle Breed Society. The data covered a period of 7 generations from 1985 to 2010. Direct heritability estimates obtained were 0.21 ± 0.024, 0.23 ± 0.021, 0.22 ± 0.025, 0.29 ± 0.029 and 0.24 ± 0.019 for BW, WW, YW, FW and MW, respectively. Maternal heritability estimates for birth weight and weaning weight were 0.05 ± 0.01 and 0.11 ± 0.001, respectively. The direct genetic correlations between the different traits were all positive, ranging from moderate (0.43 ± 0.081) between YW and MW to high (0.99 ± 0.043) between WW and FW.

Estimation of variance components and genetic parameters for growth traits in New Zealand White rabbit (Oryctolagus cuniculus)

Birth weights and subsequent body weights of individual kits of New Zealand White rabbits were analysed to estimate the impact of direct additive genetic, maternal additive genetic and permanent environmental litter effect on growth traits i.e. birth weight (BW), 15th day body weight (15dW), 30th day body weight (30dW), 90th day body weight (90dW) and 180th day body weight (180dW). The variance components and genetic parameters were estimated using Sire Model and two different animal models. Effect of litter size was significant on all the growth traits except 90dW. Kits born in winter season had significantly higher BW, 30dW and 90dW than the kits born in summer season. The heritability estimate for BW ranged from 0.266 (Sire Model) to 0.540 (Animal Model 2). The permanent effect of litter (c2) was highest (0.288–0.310) just before weaning at 30dW and decreased after weaning. The effect of indirectly inherited maternal genetic effect (m2) was present at early juvenile stage of growth (15dW, 30dW and 90dW) and was nil for 180dW. Selection for better growth would be more reliable at 180dW because at this age both c2 and m2 became lower than in previous stages of growth. Using Animal Model 1, repeatabilities of doe effects on BW, 15dW, 30dW, 90dW and 180dW were 0.35, 0.44, 0.40, 0.35 and 0.01, respectively. Animal Model 1 was better than Animal Model 2 in partitioning of variances when the maternal genetic variance () was very low or zero.