Direct-maternal Genetic Correlations Research Articles

Genetic parameters, genetic trends and correlated responses of growth traits considering maternal ability in Nelore cattle.

The growth of Nelore cattle was analysed considering the following performance parameters; the effect of the calving order of cows on the phenotypic expression of birth weight (BW), average daily gain from birth to weaning (BWG), and weaning weight (WW), the estimated genetic parameters for the traits, including the covariance components between direct and maternal genetic effects. Genetic trends and correlated responses were also obtained for the studied traits. The calving order of cows, as well as other fixed effects used to obtain the adjusted phenotypic means, were statistically significant (p < 0.001) for studied traits. Direct heritability was estimated at 0.24 ± 0.01 (BW), 0.15 ± 0.01 (BWG), and 0.18 ± 0.01 (WW), while maternal heritability was 0.06 ± 0.01 (BW), 0.12 ± 0.01 (BWG), and 0.11 ± 0.01 (WW). The correlations between direct and maternal effects within the same trait were negligible. Moderate to higher direct genetic correlations (ranging from 0.54 ± 0.04 to 0.98 ± 0.01) and maternal genetic correlations (ranging from 0.34 ± 0.09 to 0.99 ± 0.002) were estimated between the studied traits. Unlike direct genetic effects, there was no significant change in maternal genetic effects over time (p > 0.05). These results indicated the need for revising selection indexes for enhancing maternal ability. Correlated responses were generally lower compared to direct responses, except for BWG. The selection for BWG, considering the maternal genetic effect, would be more efficient to improve maternal ability of the cows for pre-weaning growth in relation to selection for WW. Our results found that direct genetic merit improves pre-weaning weight and this trait can be incorporated into the breeding goal as reflected in the WW.

Genome-Wide Association Study of Maternal Genetic Effects on Intramuscular Fat and Fatty Acid Composition in Rabbits.

Maternal genetic effects (MGE) could affect meat quality traits such as intramuscular fat (IMF) and its fatty acid composition. However, it has been scarcely studied, especially in rabbits. The objectives of the present study were, first, to assess the importance of MGE on intramuscular fat and fatty acid composition by applying a Bayesian maternal animal model in two rabbit lines divergently selected for IMF. The second objective was to identify genomic regions and candidate genes of MGE that are associated with the traits of these offspring, using Bayesian methods in a Genome Wide Association Study (GWAS). Quantitative analyses were performed using data from 1982 rabbits, and 349 animals from the 9th generation and 76 dams of the 8th generation with 88,512 SNPs were used for the GWAS. The studied traits were IMF, saturated fatty acids (total SFA, C14:0; myristic acid, C16:0; palmitic acid and C18:0; stearic acid), monounsaturated fatty acids (total MUFA, C16:1n-7; palmitoleic acid and C18:1n-9; oleic acid), polyunsaturated fatty acids (total PUFA, C18:2n-6; linoleic acid, C18:3n-3; α-linolenic acid and C20:4n-6; arachidonic acid), MUFA/SFA and PUFA/SFA. The proportion of phenotypic variance explained by the maternal genetic effect ranged from 8 to 22% for IMF, depending on the model. For fatty acid composition, the proportion of phenotypic variance explained by maternal genetic effects varied from 10% (C18:0) to 46% (MUFA) in a model including both direct and additive maternal genetic effects, together with the common litter effect as a random variable. In particular, there were significant direct maternal genetic correlations for C16:0, C18:1n9, C18:2n6, SFA, MUFA, and PUFA with values ranging from -0.53 to -0.89. Relevant associated genomic regions were located on the rabbit chromosomes (OCU) OCU1, OCU5 and OCU19 containing some relevant candidates (TANC2, ACE, MAP3K3, TEX2, PRKCA, SH3GL2, CNTLN, RPGRIP1L and FTO) related to lipid metabolism, binding, and obesity. These regions explained about 1.2 to 13.9% of the total genomic variance of the traits studied. Our results showed an important maternal genetic effect on IMF and its fatty acid composition in rabbits and identified promising candidate genes associated with these traits.

Genetic and phenotypic parameters for growth traits of Sonadi sheep

The aim of present study was to estimate the genetic and phenotypic parameters for growth traits of Sonadi sheep. Records of lambs were collected over a period of four years from Sonadi unit maintained at CVAS Navania (Rajasthan) under Mega Sheep Seed Project. Traits included for the study were birth weight (BWT), weight at three months (3MWT), weight at six months (6MWT), weight at nine months (9MWT) and weight at twelve months of age (12MWT). Low estimates of heritability were observed for weight at birth, three and twelve months of age. Lamb weight at six and nine months of age was moderately heritable and shows that these traits are less influenced by environmental effects; which make them effectively transmitted to the progeny. However, estimates of genetic parameter with high sampling error do not agree with empirical results. The direct maternal genetic correlation (ram) was negative for all body weight except for twelve months body weight. A negative estimate of am resulted in increase in direct and maternal heritability pointing towards cross substitution effect in the partitioning of total variation. The high positive genotypic and phenotypic correlations between body weight at six months, nine months and twelve months of age indicates that selection for six months of traits will result in increase in nine and twelve months of body weight

Estimation of genetic parameters for important traits using a multi-trait model in late-feathering Qingyuan partridge hens in China.

Qingyuan partridge chicken is one of the most well-known Chinese indigenous yellow broilers. In breeding programmes, five traits are usually selected when the chickens are 105 days old, namely body weight (BW), comb height (CH), shank length (SL), shank girth (SG) and feather maturity (FM). The objective of this study was to estimate the genetic parameters of these five traits, especially direct additive genetic correlations, to lay the foundation for balanced selection of Qingyuan partridge chickens. Approximately 9600 records were used for estimation. Variance components for these five traits were estimated using three multi-trait models incorporating different effects via Gibbs sampling. Based on model 1 in which the random effects included direct additive genetic effects and residuals, the estimated direct heritabilities for BW, CH, SL, SG and FM were 0.29 ± 0.04, 0.53 ± 0.04, 0.47 ± 0.04, 0.43 ± 0.05 and 0.18 ± 0.03, respectively. The direct genetic correlations ranged from -0.08 to 0.46. When additionally considering maternal additive genetic effects (model 2), the estimates of direct heritabilities and absolute values of direct additive genetic correlations were smaller. The heritabilities were 0.14 ± 0.04, 0.40 ± 0.02, 0.34 ± 0.05, 0.27 ± 0.05 and 0.12 ± 0.03 for BW, CH, SL, SG and FM, respectively. The direct additive genetic correlations ranged from -0.33 to 0.36. More specifically, the direct additive genetic correlations between BW and CH, SL, SG and FM were 0.19 ± 0.13, 0.15 ± 0.15, 0.36 ± 0.15 and - 0.33 ± 0.21, respectively. The genetic correlations of FM with SL, SG and CH were - 0.15 ± 0.15, -0.08 ± 0.17 and 0.18 ± 0.15, respectively. The direct genetic correlations between CH and SG and SL were - 0.02 ± 0.11 and - 0.20 ± 0.11, respectively, and that between SL and SG was 0.19 ± 0.11. The total heritabilities and maternal additive genetic correlations ranged from 0.16 to 0.44 and from -0.13 to 0.61, respectively. The third model also included the maternal permanent environmental effect for BW. The estimates of direct heritability, direct additive genetic correlation, total heritability and maternal additive genetic correlation were only slightly different from those based on the second model. Therefore, the maternal additive genetic effect has a large effect on the estimation of genetic parameters, and it is better to consider this effect in the genetic evaluation of these five traits. Relatively high direct and maternal additive genetic correlations for most trait pairs suggested that it is better to jointly evaluate these five traits in breeding programmes.

Genetic variation and parameters for growth and feed efficiency traits in Boran beef cattle in Kenya

A major drawback of improving feed efficiency in beef cattle enterprises is to identify measures of feed efficiency which do not require feed intake information on an individual animal basis. Kleiber Index, (KI) and relative growth rate (RGR) are alternative measures which do not need individual measurement of intake and can be used select for improved feed and growth efficiency in relation to their body size. The aim of this study was to estimate genetic parameters for measures of feed efficiency and growth traits for the Boran beef cattle in Kenya. A total of 1348, 2209, 2183 and 2184 weight records were available for birth, weaning, yearling and 550-day weight records, respectively, were available for animals born between 1973 and 2019. The traits derived were growth rates (ADG), adjusted weights (WA), KI and RGR at weaning (205 days), yearling (365 days) and 550 days. Genetic parameters were estimated using a maternal genetic effects model. Direct heritability estimates for direct heritability estimates for ADG ranged from 0.12±0.04 for ADG205-365 to 0.27±0.02 for ADGB-205. Estimates for WA were in range of 0.05±0.05 at to 0.10±0.05 at 550 days. Estimates for KI were 0.13±0.05 at 205 to 0.29±0.05 at 550 days. For RGR estimate direct heritability at 205 was 0.21±0.05, 0.19±0.04 at 365 and 0.33±0.05 at 550 days. The direct-maternal genetic correlations for WA, ADG, KI and RGR at 205 days were -0.30±0.05, -0.30±0.04, 0.90±0.05 and -0.72±0.04, respectively. Alongside growth traits, Kleiber Index and residual growth rate had substantial heritability estimates, implying potential for improvement through selection.

Estimation of direct and maternal genetic parameters for weaning weight in Hungarian Simmental cattle

The aim of the current research was to estimate variance components and genetic parameters of weaning weight in Hungarian Simmental cattle. Weaning weight records were obtained from the Association of Hungarian Simmental Breeders. The dataset comprised of 44,278 animals born from 1975 to 2020. The data was analyzed using the restricted maximum likelihood methodology of the Wombat software. We fitted a total of six models to the weaning weight data of Hungarian Simmental cattle. Models ranged from a simple model with animals as the only random effect to a model that had maternal environmental effects as additional random effects as well as direct maternal genetic covariance. Fixed effects in the model comprised of herd, birth year, calving order and sex. Likelihood ratio test was used to determine the best fit model for the data. Results indicated that allowing for direct-maternal genetic covariance increases the direct and maternal effect dramatically. The best fit model had direct and maternal genetic effects as the only random effect with non-zero direct-maternal genetic correlation. Direct heritability, maternal heritability and direct maternal correlation of the best fit model was 0.57, 0.16 and -0.78 respectively. The result indicates that problem of (co-)sampling variation occurs when attempting to partition additive genetic variance into direct and maternal components.

PSI-17 Genetic analysis of weaning weight in Hungarian Simmental cattle

Abstract The aim of the study was to partition the total phenotypic variation in the weaning weight of Hungarian Simmental calves into their various causal components. The data used was provided by the Association of Hungarian Simmental Breeders. The dataset comprised of the weaning weight records of 44,278 calves (sire = 879, dam = 14,811) born from 1975 to 2020. A total of six models were fitted to the weaning weight data. Herd, birth year, calving order and sex were included as fixed effects in the models. Model 1 had direct genetic effect as the only random effect. Model 2 had a permanent maternal environment as an additional random effect. Model 3 had both direct and maternal genetic effects, with their covariance is being zero. Model 4 was similar to Model 3 but with non-zero direct-maternal genetic covariance. Model 5 had direct, maternal genetic and permanent environmental effects and a zero direct-maternal genetic covariance. Model 6 was similar to model 5 but the direct-maternal genetic effect was assumed to be correlated. Variance components and genetic parameters were estimated using restricted maximum likelihood method with the Wombat software. The best fit model was determined using the Log likelihood ratio test. Inclusion of direct maternal genetic covariance increased the variance components estimates dramatically which resulted in a corresponding increase in the direct and maternal heritability estimates. The best fitted model (Model 4) had direct and maternal genetic effects as the only random effects with a non-zero direct-maternal genetic covariance. The direct heritability, maternal heritability and direct-maternal genetic correlation estimate of the best model was 0.57, 0.16 and -0.78, respectively. Our result suggests the problem of (co)sampling variation in the partitioning of additive genetic effect into direct and maternal components.

The impact of direct-maternal genetic correlations on international beef cattle evaluations for Limousin weaning weight.

In beef cattle maternally influenced traits, estimates of direct-maternal genetic correlations (rdm) are usually reported to be negative. In international evaluations, rdm can differ both within countries (rdm_WC) and between countries (rdm_BC). The rdm_BC are difficult to estimate and are assumed to be zero in the current model for international beef cattle evaluations (Interbeef). Our objective was to investigate re-ranking of international estimated breeding values (IEBVs) in international beef cattle evaluations between models that either used estimated values for rdm or assumed them to be 0. Age-adjusted weaning weights and pedigree data were available for Limousin beef cattle from ten European countries. International EBVs were obtained using a multi-trait animal model with countries modeled as different traits. We compared IEBVs from a model that uses estimated rdm_BC (ranging between −0.14 and +0.14) and rdm_WC (between −0.33 and +0.40) with IEBVs obtained either from the current model that assumes rdm_BC to be 0, or from an alternative model that assumes both rdm_BC and rdm_WC to be 0. Direct and maternal IEBVs were compared across those three scenarios for different groups of animals. The ratio of population accuracies from the linear regression method was used to further investigate the impact of rdm on international evaluations, for both the whole set of animals in the evaluation and the domestic ones. Ignoring rdm_BC, i.e., replacing estimated values with 0, resulted in no (rank correlations > 0.99) or limited (between 0.98 and 0.99) re-ranking for direct and maternal IEBVs, respectively. Both rdm_BC and rdm_WC had less impact on direct IEBVs than on maternal IEBVs. Re-ranking of maternal IEBVs decreased with increasing reliability. Ignoring rdm_BC resulted in no re-ranking for sires with IEBVs that might be exchanged across countries and limited re-ranking for the top 100 sires. Using estimated rdm_BC values instead of considering them to be 0 resulted in null to limited increases in population accuracy. Ignoring both rdm_BC and rdm_WC resulted in considerable re-ranking of animals’ IEBVs in all groups of animals evaluated. This study showed the limited impact of the current practice of ignoring rdm_BC in international evaluations for Limousin weaning weight, most likely because the estimated rdm_BC was close to 0. We expect that these conclusions can be extended to other traits that have reported rdm values in the range of rdm_WC values for weaning weight in Limousin.

Direct and maternal genetic components for body weight traits in Markhoz goat.

The aim of the study was to estimate the (co)variance components and genetic trends of direct and maternal genetic effects in Markhoz goat using random regression (RR) models. A total of 16,283 body weight trait records from birth to 400 days of age were obtained from 3476 Markhoz kids. Kids were from 223 bucks and 1217 does raised in the Markhoz goat breeding station in Sanandaj, Iran. The fixed effects were gender, year of birth (1992-2014), age of dam (2 to 7 years old), and type of birth (single or twin). RR models based on Legendre polynomials of age at weight recording included direct and maternal genetic and permanent environmental effects. Heterogeneous residual variances were considered along age of recording. According to the Akaike information criterion (AIC), the Bayesian information criterion (BIC) and the likelihood ratio test (LRT), adding covariance between direct and maternal genetic effects, resulted in significant improvement in the level of fit. After examining models with different order of fits, the most suitable model consisted of the fourth-order polynomial for direct genetic effect and the third-order polynomial for maternal genetic, individual permanent environmental, and maternal permanent environmental effects. The direct heritabilities ranged from 0.21 at birth to 0.55 at 400 days of age. The largest (0.25) and the lowest (0.17) maternal heritabilities were estimated at birth and 60 days of age, respectively. Generally, negative direct-maternal genetic correlations were estimated between different ages, which might cause fluctuations of direct-maternal genetic trends along the years. It was concluded that selection at 100 days of age could reduce the impact of the antagonist relationship between maternal and direct genetic effects.

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.

Maternal effect on body measurement and meat production traits in purebred Duroc pigs.

We investigated maternal effect on nine body measurement traits (body height, body length, front width (FW), chest width (CW), hind width (HW), chest depth, chest girth (CHG), front cannon circumference (FCC) and rear cannon circumference (RCC)) measured at the end of performance testing and five meat production traits (ages at the start and end of performance testing (D30 and D105), average daily gain (ADG), backfat thickness and loin muscle area) in purebred Duroc pigs. Genetic parameters for each trait were estimated by using six single-trait models with and without common litter environmental effect, maternal genetic effect and direct-maternal genetic correlation. The value of Akaike's information criterion was lowest with the model including direct additive genetic and common litter environmental effects for 10 traits. The estimated proportion of common litter environmental variance to phenotypic variance was approximately ≥0.1 for D30, D105, ADG, FW, CW, HW, CHG, FCC and RCC. Using a model without common litter environmental effect would overestimate the direct heritability of most traits. Standard errors of estimated genetic parameters tended to be larger in models including maternal genetic effect. The results indicate that a compromise could be made for accurate genetic parameter estimation for body measurement traits, as well as meat production traits, in pigs by considering common litter environmental effect.

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.

Desired Gain Selection Indices for Pre-Weaning Body Weights in Zaraibi Male Kids in Egypt

The aim of the current study was to estimate the genetic parameters and evaluate various desired-gain selection indices for pre-weaning live body weights of Zaraibi male kids in Egypt. From 2005 to 2012, data of 763 does mated with 75 bucks of Zaraibi goats raised at El-Serw Experimental Station belonging to the Animal Production Research Institute were collected. Data were analyzed with REML using animal model to determine genetic parameters and using SAS to construct different desired-gain selection indices. Direct heritability (h2d) for BW, W30, W60 and WW were 0.25, 0.22, 0.31 and 0.35, respectively. Corresponding maternal heritability (h2m) for aforementioned traits were 0.145, 0.141, 0.099 and 0.073, respectively. While total heritability (h2t) above traits were 0.25, 0.38, 0.48, 0.49 and 0.34, respectively. The direct-maternal genetic correlations (rdm) were positive for W30 (0.35) and W60 (0.47), while negative for BW (-0.23) and WW (-0.19). Genetic correlations (rd1d2) among studies traits ranged from 0.80 to 0.95, while phenotypic correlations (rp1p2) among all traits ranged from 0.69 to 0.84. Comprisable between selection indices was the highest number of generations required (T) to attain the pre-estimated goals was 5.6143 in I4. In contrast, the lowest number of generations required (T) was 2.0220 in I14. Therefore, I14 was considered the best selection index lead to save time and efforts for genetic improvement of studied traits in Zaraibi male kids in Egypt.

Genetic parameters for growth and cow productivity traits in Angus, Hereford and crossbred cattle

Reproductive and growth performance are major factors affecting the efficiency of beef production. The objectives of this study were to estimate genetic parameters for five cow fertility and productivity traits (pre-weaning average daily gain (PWG), weaning-to-first calving average daily gain (WFCG), age at first calving (AFC), cow weight at weaning (CWW) and cow average annual productivity (CAAP) in an experimental herd of Angus, Hereford, and reciprocal Hereford-Angus crossbred cattle. (Co)variance components were estimated by Bayesian inference using ten bivariate animal models representing all possible pairwise combinations of the five traits. Fixed environmental effects were contemporary group (all traits), class of age of dam at calving (PWG only), age of heifer at first calving (WFCG only), and cow age at weaning, age of calf at weaning and sex of calf (CWW only). Fixed genetic effects for all traits were breed group of cow and heterosis of the cow as a function of expected heterozygosity. Random effects were direct additive genetic (PWGd and WFCGd; d = direct), maternal additive genetic effects (PWGm and WFCGm; m = maternal), maternal permanent environmental effect (PWG only), direct permanent environmental effect (CWW only), and residual (all traits). Direct heritability estimates ± standard deviations for PWG and WFCG were 0.15 ± 0.04 and 0.44 ± 0.18, respectively. Heritability for maternal additive genetic effects was lower for WFCG (0.08 ± 0.05) than for PWG (0.17 ± 0.13). Direct-maternal genetic correlations were -0.38 ± 0.35 for WFCG and -0.26 ± 0.17 for PWG. Heritabilities were low for AFC (0.08 ± 0.05) and CAAP (0.17 ± 0.06). Conversely, CWW had high heritability (0.64 ± 0.13) and repeatability estimates (0.74 ± 0.03). AFC showed a high positive genetic correlation with PWGd (0.98 ± 0.01) and a negative correlation with PWGm (-0.51 ± 0.13). CWW was positively and highly associated genetically with PWGd and WFCGd, while genetic correlations were moderate and positive between CAAP and CWW (0.46 ± 0.13) and high and positive between CAAP and PWGm (0.93 ± 0.03). The estimated genetic variation for CAAP makes it a good selection objective. However, unrestricted selection for CAAP could increase mature weight. Thus, monitoring female mature weight under grazing conditions is essential to avoid large and heavy replacement cows with high nutritional requirements. Therefore, beef selection programs in Argentina should be aimed at increasing CAAP while maintaining mature weight, by imposing restrictions on CWW or other traits measured earlier in life. Outcomes of this study will contribute to the development of optimized bioeconomic models for commercial beef cattle herds under the extensive production conditions in Argentina.

Genetic parameters of pre-weaning weights in crossbred piglets using multi-trait animal model.

Variances and genetic parameters (heritability and correlation) were estimated for pre-weaning weights from birth to 6weeks of age at weekly intervals in crossbred (Landrace X Desi) pigs. Data were analysed using multi-trait animal model incorporating dam's age (covariable), parity of sow, sex of piglet, season of birth and year of birth as fixed effects and direct additive genetic, maternal genetic and permanent litter as random effects. The estimates of direct additive genetic and maternal genetic heritability were 0.18 ± 0.04 and 0.14 ± 0.04; 0.73 ± 0.06 and 0.62 ± 0.06; 0.64 ± 0.06 and 0.37 ± 0.05; 0.42 ± 0.05 and 0.30 ± 0.05; 0.37 ± 0.04 and 0.33 ± 0.05; 0.43 ± 0.04 and 0.34 ± 0.06 and 0.47 ± 0.04 and 0.36 ± 0.05 for birth weight and subsequent weights at weekly intervals up to 6weeks, respectively. The permanent litter effect ranged from 0.02 ± 0.01 (birth weight) to 0.11 ± 0.04 (weight at first week). The estimates of correlation between direct additive genetic component and maternal genetic component (i.e. ram) were moderate to high but all negative. ram ranged from - 0.79 ± 0.15 (weight at first week) to - 0.49 ± 0.26 (birth weight). The direct additive genetic and maternal genetic correlations between birth weight and weaning weight were 0.59 ± 0.04 and 0.62 ± 0.13, respectively, which revealed sufficient scope for selection based on birth weight itself. Early weights were found to be highly heritable with due influence of maternal and permanent litter effects, and thus, appropriate selection interventions may be aimed at this stage for favourable changes at subsequent ages.

Statistical models for genetic evaluation of some first kidding and lifetime traits of the Egyptian Zaraibi goats

The aim of the present study was to define the best fitting model for genetic evaluation of the Egyptian Zaraibi goats using three statistical models. Models differed based on the inclusion or exclusion of maternal additive genetic effects and the direct-maternal genetic covariance (σam). The models used were; Model 1 (without maternal effects); Model 2 (with maternal effects where σam = 0) and Model 3 (as in Model 2, but σam ≠ 0). The evaluated traits were; litter size at birth (LSB, kid), litter size at weaning (LSW, kid), litter weight at birth (LWB, kg), litter weight at weaning (LWW, kg), first lactation milk yield (FLMY, kg), first lactation length (FLL, day), total milk yield in productive life (TMY, kg) and total lactation length in productive life (TLL, day). Data represented some first lactation and longevity traits. A total of 2270 first kidding records produced from 600 does that were sired by 95 bucks. Statistical analyses were done using VCE-6 software. Model selection was built on the value of Akaike information criterion (AIC). Direct heritabilities were higher than maternal heritabilities in all models, and varied between 0.09 to 0.21, 0.05 to 0.22, 0.11 to 0.24 and 0.05 to 0.20 for LSB, LSW, LWB and LWW, respectively. Direct heritability for yield and lifetime traits were low to moderate and varied from 0.16 to 0.18, 0.07 to 0.34, 0.15 to 0.16 and 0.08 to 0.18 for FLMY, FLL, TMY and TLL, respectively. Maternal heritabilities ranged from 0.02 to 0.30 from models 2 and 3. Direct-maternal genetic correlations were low to moderate, negative for most of studied traits and ranged from −0.01 to −0.38. The inclusion of both direct and maternal effects in addition to the covariances between them in statistical models is recommended for the best genetic improvement of Egyptian Zaraibi goats.

Estimates of (co)variance components and genetic parameters for body weights and growth efficiency traits in the New Zealand white rabbit

The genetic parameters of growth traits in the New Zealand White rabbits kept at Sheep Breeding and Research Station, Sandynallah, The Nilgiris, India were estimated by partitioning the variance and covariance components. The (co)variance components of body weights at weaning (W42), post-weaning (W70) and marketing (W135) age and growth efficiency traits viz., average daily gain (ADG), relative growth rate (RGR) and Kleiber ratio (KR) estimated on a daily basis at different age intervals (42 to 70 d; 70 to 135 d and 42 to 135 d) from weaning to marketing were estimated by restricted maximum likelihood, fitting 6 animal models with various combinations of direct and maternal effects. Data were collected over a period of 15 yr (1998 to 2012). A log-likelihood ratio test was used to select the most appropriate univariate model for each trait, which was subsequently used in bivariate analysis. Heritability estimates for W42, W70 and W135 were 0.42±0.07, 0.40±0.08 and 0.27±0.07, respectively. Heritability estimates of growth efficiency traits were moderate to high (0.18 to 0.42). Of the total phenotypic variation, maternal genetic effect contributed 14 to 32% for early body weight traits (W42 and W70) and ADG1. The contribution of maternal permanent environmental effect varied from 6 to 18% for W42 and for all the growth efficiency traits except for KR2. Maternal permanent environmental effect on most of the growth efficiency traits was a carryover effect of maternal care during weaning. Direct maternal genetic correlations, for the traits in which maternal genetic effect was significant, were moderate to high in magnitude and negative in direction. Maternal effect declined as the age of the animal increased. The estimates of total heritability and maternal across year repeatability for growth traits were moderate and an optimum rate of genetic progress seems possible in the herd by mass selection. The genetic and phenotypic correlations among body weights and between growth efficiency traits were also estimated. Moderate to high heritability and higher genetic correlation in body weight traits promise good scope for genetic improvement provided measures are taken to keep the inbreeding at the lowest level.

The milk yield of dams and its relation to direct and maternal genetic components of weaning weight in beef cattle

Cow milk yield is a critical component for the growth of the calves in the preweaning period. The genetic correlation between direct weaning weight and milk yield traits may cause a decrease in the maternal ability of cows when they are selected for the direct weaning weight of the calf. The objective of this study was to analyse the genetic and environmental components of some traits of interest in beef cattle breeds managed in mountain conditions by analysing the actual cumulative milk yield at 150 days obtained by milking (MY150) and the weight at birth (BW), at 90 days (W90), at weaning (W150), and mature weight (MW). Genetic evaluations were conducted using field data from 2679 calves born from 553 dams of Parda de Montaña beef cattle breed. The variances, genetic (both direct and maternal) and phenotypic, were estimated by a multi-trait animal model. Milk yield was correlated with maternal components of calf weight at 90 days and 150 days (genetic correlations of 0.59 and 0.48, respectively) and also correlated with a direct genetic component of W90 and W150 (genetic correlations of 0.58 and 0.54, respectively). The maternal heritability values for W90 and W150 were 0.023 (0.005) and 0.009 (0.004), respectively. The estimates of the direct-maternal genetic correlation for W90 and W150 were − 0.13 (0.11) and − 0.34 (0.16), respectively. Environmental effects, especially the sex of calf and dam parity for direct genetic effects and energy level of cow and body condition at calving for maternal effects, should be included in the evaluation models to obtain a proper estimation of genetic parameters for beef cattle evaluation. Genetic milk yield explains half the variation of maternal effects for W90 and W150. The prediction of milk yield will be better using maternal effects at 90 days than at 150 days. The combined index (maternal and direct) for the trait weight at 150 days yielded the highest economic response increasing the direct effect indirectly without decreasing the maternal effect at 150 days.

The direct-maternal genetic correlation has little impact on genetic evaluations.

Obtaining unbiased estimates of the direct-maternal genetic correlation proves far from straightforward for several reasons. Consequently, the use of such over- or underestimated correlations may introduce errors in genetic evaluation models. The objective of our study was to evaluate how the value of the direct-maternal genetic correlation affects EBV. Direct, maternal, and total breeding values were predicted for the ADG or weight at weaning for 3 different species (sheep, rabbits, and pigs) using models that differ depending on the fixed value of the direct-maternal genetic correlation (ranging from -0.9 to 0.9) as well as a model in which the correlation was estimated. The results were consistent between species. The direct-maternal genetic correlation had a greater impact on the estimated maternal genetic effects than on direct effects. The lowest correlations between maternal breeding values obtained with different models were -0.20, -0.01, and -0.72 in pigs, sheep, and rabbits, respectively, whereas for the direct breeding value, the lowest correlations were 0.45, 0.90, and 0.95 in pigs, sheep, and rabbits, respectively. The total EBV, calculated as the unweighted sum of direct and maternal genetic effects, did not differ greatly between the models, the lowest correlations between total breeding values being 0.93, 0.98, and 0.97 for pigs, sheep, and rabbits, respectively. Given the uncertainty associated with estimating the direct-maternal genetic correlation, setting its value to 0 in genetic evaluation models appears to be a good compromise.