Estimates Of Direct Genetic Correlation Research Articles

Bayesian estimation of the genetic relationship of survival traits from birth to yearling age with birth weight in Guilan sheep.

This study aimed to estimate genetic parameters for cumulative survival traits from birth to yearling age and to estimate their genetic relationship with birth weight in Guilan sheep. The dataset used in this study comprised 41,037 survival records of Guilan lambs born from 496 sires and 10,256 dams, collected by the Guilan Province Agricultural Jihad Organization (in Rasht, Iran) during 1990-2013. The data included complete pedigree information; gender; year, month, and day of death; dam age; year, month, and day of birth; birth type; and birth weight. Cumulative survival traits from birth to yearling age were analyzed using threshold animal models via the Bayesian method. Also, linear-threshold animal models were used to study the genetic relationship between survival at different ages and birth weight. Direct heritability estimates of cumulative survival from birth to 60, 90, 180, 270, and 365days of age were low and equal to 0.17, 0.16, 0.08, 0.04, and 0.04, respectively, and the corresponding maternal heritability estimates were 0.21, 0.18, 0.15, 0.08 and 0.08, respectively. Mean estimates of direct genetic correlations between birth weight and survival traits were medium (from 0.22 to 0.28). To improve the survival traits, more emphasis must be put on the amelioration of the non-genetic factors affecting it. Indirect selection based on traits high genetically correlated with survival could increase the survival rate in Guilan lambs.

Maternal Genetic Effect on Expected Genetic Response of Selection Indices for Milk Production of Friesian Cows in Egypt

The present study aimed to estimate the genetic parameters of first lactation milk yield (FLMY), first lactation period (FLP), first dry period (FDP) and first calving interval (FCI) and inclusion these studied traits in selection indices through different animal models. The data utilized in this study were obtained from 1821 normal first lactation of Friesian cows belong to Sakha and EI-Karada Experimental stations of Animal Production Research Institute (APRI), Ministry of Agriculture, Dokki, Cairo, Egypt. Data were collected during the period from 1990 to 2016 and analyzed using the MTDFREML program. Covariance components were used to construct the different selection indices for FLMY kg, FLP day, FDP day and FCI day with four multiple animal models. Means for FLMY FLP, FDP and FCI were 2425 kg, 304 d, 170 d and 474 d, respectively. Direct additive heritability (h2a) for the above-mentioned traits were 0.32, 0.29, 0.27 and 0.18, respectively. The corresponding estimates of the maternal heritability (h2m) for the same traits were 0.25, 0.22, 0.30 and 0.27, successively. Estimates of direct genetic correlations among studied traits ranged from -0.52 to 0.61. Phenotypic correlations among investigated traits were ranging from -0.20 to 0.23. Animal model number two that included the additive and permanent effects had the highest accuracy. On the contrary, model number three that included additive and maternal effects. The ranking correlations among four animal models were higher than 0.93. This indicates that using one of the studied models can be achieved the genetic improvement. We would however recommend that included the permanent environmental effects on analytical models when selection for these traits in Friesian cows under Egyptian condition.

Estimation of genetic parameters for growth traits and Kleiber ratios in Boer x Central Highland goat.

Accurate performance evaluation and genetic parameters estimation are the prerequisites for any successful genetic improvement program. This study was conducted to estimate genetic parameters for growth and Kleiber ratio traits in Boer x Central Highland goats. On-station data collected from 2009 to 2018 were utilized for the study. A general linear model procedure of the Statistical Analysis System (SAS, version 9.0) was used to analyze fixed effects, and genetic parameters were estimated using the WOMBAT software fitted animal model. The log-likelihood ratio test was used for selecting the best fitted model. Based on best fitted models, the total heritability (h2t) estimate for birth weight (BWT), weaning weight (WWT), six-month weight (SMWT), nine-month weight (NMWT), and yearling weight (YWT) were 0.38, 0.12, 0.05, 0.30, and 0.28, respectively. The total heritability (h2t) estimates for weight gain from birth to weaning (ADG1), 3 to 6months (ADG2), 6 to 9months (ADG3), and 9 to 12months of age (ADG4) were 0.09, 0.08, 0.16, and 0.14, respectively. The heritability estimates for Kleiber ratios in different growth phases were found to be low (0.09 to 0.18) based on the selected models. Even with this figure, including the Kleiber ratio in the selection criteria would be imperative to improve the feed efficiency of crossbred goats. The direct genetic correlation estimates among growth traits range from 0.60 ± 0.14 to 0.97 ± 0.12. Except for NMWT, ADG4, and Kleiber ratio from 9months to yearling age, the maternal effect had a significant influence on all considered traits. However, the contribution of the maternal genetic effect was more important for early growth traits. Thus, considering both the direct additive genetic effect and the maternal genetic effect is imperative for accurate genetic evaluation and for high selection response. The moderate heritability estimates for most of the growth traits implies the possibility of selection in conjunction with crossbreeding for a better genetic response. The positive and high genetic correlation estimates among growth traits confirm the possibility of a selection of goats at an early age.

Direct and maternal effects models for variance components and genetic parameters estimation of growth traits in prolific Garole sheep

The objective of the study was to identify the mostsuitable model for estimation of (co) variance components and genetic parameters of different growth traits in prolific Garole sheep. Growth data of 1,058 Garole lambs born to 49 sires and 208 ewe was collected from ICAR-Central Sheep and Wool Research Institute (ICAR-CSWRI), Avikanagar, India. The traits studied were birth weight (BWT), 3 month weight (3WT), 6 month weight (6WT), 9 month weight (9WT), 12 month weight (12 WT), average daily gain from birth to 3 month age (ADG1), average daily gain from 3 month to 6 month age (ADG2). Twelve different animal models were fitted to account for different direct genetic and maternal effects. Model including maternal permanent environmental effect, maternal temporary environmental effect and direct genetic effects (Model 8) was most appropriate model for BWT. For other traits model with direct genetic effect and common litter effect (Model 7) was found most suitable. From best model direct heritability estimates of 0.037±0.054, 0.148±0.075, 0.104±0.077, 0.079±0.083, 0.103±0.116, 0.137±0.072 and 0.045±0.071 were obtained for BWT, 3WT, 6WT, 9WT, 12WT, ADG1and ADG2, respectively. Maternal temporary environmental effect variance contributed highest to total phenotypic variance. It ranged from 0.347±0.040 for BWT to 0.451±0.083 for 9WT. Estimates of direct genetic correlation ranged from –0.047 for BWT-ADG1 to 1.00 for BWT-12WT, 6WT-12WT and 9WT-12WT. Phenotypic correlations were positive and varied from 0.119 for ADG1-ADG2 to 0.982 for 3WT-ADG1. The growth traits of Garole sheep have low to moderate heritability and were influenced by maternal temporary environmental effect due to sharing of common litter environment.

Bayesian estimates of genetic parameters and genetic trends for morphometric traits and their relationship with yearling weight in Moghani sheep

This study was conducted to estimate variance components, genetic parameters and genetic trends for morphometric traits and their relationship with yearling weight in Moghani sheep. The data set and pedigree information of Moghani sheep were obtained from the breeding station of Moghani sheep (in Ardebil province, Iran) and comprised 2387 lamb records for morphometric traits during 1994 to 2012. Traits considered were height at withers (HW), height at rump (HR), body length (BL), heart girth (HG), leg circumference (LC) and yearling weight (YW). Four different animal models were fitted, differentiated by including or excluding maternal effects, with covariance between maternal and direct genetic effects were implemented by Gibbs sampling methodology. Selection of the best model of analysis for each trait was based on Akaike’s information criterion (AIC). Posterior mean estimates of direct heritabilities for BL, HW, HR, LC, HG and YW were 0.34, 0.037, 0.47, 0.073, 0.065 and 0.17, respectively. Estimates of direct genetic correlation between morphometric traits varied from −0.21 (between BL–LC) to 0.67 (between LC–HG). Estimates of direct genetic correlation between morphometric traits and YW were positive and varied from 0.08 (between HW–YW) to 0.52 (between HG–YW). Estimates of direct genetic trends for BL, HW, HR, LC and HG were significant (p < .0001), and their corresponding values were −0.054 ± 0.009, −0.005 ± 0.001, 0.032 ± 0.006, −0.009 ± 0.002 and −0.014 ± 0.003, respectively. The results implied that applicable genetic variations observed for under study traits could be applied in designing future genetic selection plans for Moghani sheep.

Estimates of direct and maternal (co)variance components as well as genetic parameters of growth traits in Nellore sheep.

In the present study, (co)variance components and genetic parameters in Nellore sheep were obtained by restricted maximum likelihood (REML) method using six different animal models with various combinations of direct and maternal genetic effects for birth weight (BW), weaning weight (WW), 6-month weight (6MW), 9-month weight (9MW) and 12-month weight (YW). Evaluated records of 2075 lambs descended from 69 sires and 478 dams over a period of 8years (2007-2014) were collected from the Livestock Research Station, Palamaner, India. Lambing year, sex of lamb, season of lambing and parity of dam were the fixed effects in the model, and ewe weight was used as a covariate. Best model for each trait was determined by log-likelihood ratio test. Direct heritability for BW, WW, 6MW, 9MW and YW were 0.08, 0.03, 0.12, 0.16 and 0.10, respectively, and their corresponding maternal heritabilities were 0.07, 0.10, 0.09, 0.08 and 0.11. The proportions of maternal permanent environment variance to phenotypic variance (Pe2) were 0.07, 0.10, 0.07, 0.06 and 0.10 for BW, WW, 6MW, 9MW and YW, respectively. The estimates of direct genetic correlations among the growth traits were positive and ranged from 0.44(BW-WW) to 0.96(YW-9MW), and the estimates of phenotypic and environmental correlations were found to be lower than those of genetic correlations. Exclusion of maternal effects in the model resulted in biased estimates of genetic parameters in Nellore sheep. Hence, to implement optimum breeding strategies for improvement of traits in Nellore sheep, maternal effects should be considered.

Estimation of genetic parameters for body weight traits and pelt quality score in Iranian Karakul sheep

Genetic parameters for birth weight (BW), weight at 3, 6, 9 months of age (3MW, 6MW, 9MW), yearling weight (YW) and pelt quality score (PELT) were estimated in Iranian Karakul sheep. Data and pedigree information were obtained from the Breeding Station of Karakul sheep located in North Khorasan province in Iran from 1994 to 2009 on 5437 lambs descended from 193 sires and 1886 dams. Six different animal models were fitted, differentiated by including or excluding maternal effects, with and without covariance between maternal and direct genetic effects. The most suitable model amongst all six models was determined based on likelihood ratio tests for each trait. In addition, multivariate analysis was carried out among the considered traits to estimate the genetic and phenotypic correlations. Direct heritability estimates for BW, 3MW, 6MW, 9MW, YW and PELT were 0.21, 0.10, 0.14, 0.18, 0.21 and 0.004, respectively. All the phenotypic correlations estimates among body weight at different ages were positive. The estimates of phenotypic correlations for PELT-BW and PELT-3MW were low and positive while the remaining were low and negative. The estimates of direct genetic correlations between body weights were positive; whereas those among PELT and liveweights were negative. Current estimates of genetic parameters in Iranian Karakul breed may be used to design selection programme. Our results showed that improvement of growth performances seems feasible, as the studied traits were moderately heritable, although the heritabilities at 3MW and 6MW were quite low. However, selection for BW should be judicious in order to prevent unfavorable consequences on pelt quality. So, considering the high genetic correlations between 3MW and other body weight traits, the genetic improvement of 3MW should be one of the main selection goals.

Estimation of genetic parameters and maternal effects for body weight at different ages in D’man sheep

The objective of this study was to estimate the genetic parameters for birth weight (BW), weight at 30 days (W30), 90 days (W90) and 135 days (W135) of D’man sheep. Records used in the study were collected over a period of 25 years (1988–2012) from 4728 lambs that descended from 129 sires and 621 dams. (Co) variance components and genetic parameters were estimated with univariate and bivariate animal models using the restricted maximum likelihood (REML) procedure. Age of dam, type of birth, sex of lamb and period of birth showed significant effects on studied weights, so they were considered as in the analysis models. Twelve different animal models were fitted by including or excluding maternal additive genetic effects, maternal permanent environmental effect, maternal temporary environmental effect and covariance between direct-maternal additive genetic effects. The most appropriate model for each trait was determined based on Akaike’s Information Criterion (AIC). Bivariate analysis was performed using the most appropriate models obtained in univariate analysis. Based on the best model, direct heritability estimates were 0.05±0.02, 0.03±0.02, 0.08±0.03 and 0.12±0.04 for BW, W30, W90 and W135, respectively. Maternal effects significantly influenced the growth traits. The maternal heritability for BW, W30 and W90 were 0.10±0.02, 0.07±0.03 and 0.07±0.03, respectively. Direct-maternal additive genetic correlations were negative and medium ranging from −0.04 to −0.54 for BW, W90 and W135, but positive and medium to high for W30 (0.25–0.71). The maternal permanent environmental effects as a proportion of total variance were 0.10, 0.05 and 0.09 for W30, W90 and W135, respectively. The maternal temporary environmental effects were 0.18, 0.09, 0.08 and 0.07 for BW, W30, W90 and W135, respectively. The estimates of direct genetic correlation between BW–W30, BW–W90, BW–W135, W30–W90, W30–W135 and W90–W135 were 0.84±0.23, 0.66±0.24, 0.81±0.15, 0.92±0.09, 0.93±0.05, 1.00±0.01, respectively. The estimates of the phenotypic correlation among traits were positive and ranged from 0.31 for BW–W135 to 0.87 for W90–W135. In conclusion, maternal effects on weights of D’man sheep are important and need to be considered in any selection programme undertaken for this breed.

Estimation of genetic relationships between growth curve parameters in Guilan sheep.

The objective of this study was to estimate variance components and genetic parameters for growth curve parameters in Guilan sheep. Studied traits were parameters of Brody growth model which included A (asymptotic mature weight), B (initial animal weight) and K (maturation rate). The data set and pedigree information used in this study were obtained from the Agricultural Organization of Guilan province (Rasht, Iran) and comprised 8647 growth curve records of lambs from birth to 240 days of age during 1994 to 2014. Marginal posterior distributions of parameters and variance components were estimated using TM program. The Gibbs sampler was run 300000 rounds and the first 60000 rounds were discarded as a burn-in period. Posterior mean estimates of direct heritabilities for A, B and K were 0.39, 0.23 and 0.039, respectively. Estimates of direct genetic correlation between growth curve parameters were 0.57, 0.03 and −0.01 between A-B, A-K and B-K, respectively. Estimates of direct genetic trends for A, B and K were positive and their corresponding values were 0.014 ± 0.003 (P < 0.001), 0.0012 ± 0.0009 (P > 0.05) and 0.000002 ± 0.0001 (P > 0.05), respectively. Residual correlations between growth curve parameters varied form −0.52 (between A-K) to 0.48 (between A-B). Also, phenotypic correlations between growth curve parameters varied form −0.49 (between A-K) to 0.47 (between A-B). The results of this study indicated that improvement of growth curve parameters of Guilan sheep seems feasible in selection programs. It is worthwhile to develop a selection strategy to obtain an appropriate shape of growth curve through changing genetically the parameters of growth model.

The estimation of (co)variance components and genetic parameters for growth traits and Kleiber ratios in Malpura sheep of India

Objective of the present study was to estimate the genetic parameters and (co)variance components for different economic traits in Malpura sheep. The traits analyzed were birth weight (BWT), weaning weight (WWT), 6-month weight (6WT), average daily gain from birth to weaning (ADG1), average daily gain from weaning to 6-month (ADG2), average daily gain from birth to 6-month (ADG3), Kleiber ratio from birth to weaning (KR1), Kleiber ratio from weaning to 6-month (KR2) and Kleiber ratio from birth to 6-month (KR3). Six different animal models including or ignoring maternal genetic or permanent environmental effects were fitted for all traits. Akaike information criterion (AIC) was applied to determine the most appropriate model for each trait. For BWT, WWT, 6WT, ADG1, ADG2 and KR2 the model including permanent environmental effects due to ewe over direct genetic effects was the most appropriate. Model which included only direct genetic effects was the best model for ADG3, KR1 and KR3. Direct heritability estimates of 0.21, 0.24, 0.23, 0.23, 0.13, 0.22, 0.20, 0.12 and 0.23 were obtained for BW, WW, 6MW, ADG1, ADG2, ADG3, KR1, KR2 and KR3, respectively. Ratios of phenotypic variance due to maternal permanent environmental effects were 0.24, 0.07, 0.01, and 0.05 for BW, WWT, 6WT and ADG1, respectively. Estimates of direct genetic correlation were very low to high in magnitude and varied from −0.27 for BW–KR2 to 0.97 for ADG1–KR1. Estimates of phenotypic correlation were very low to high in magnitude and varied from −0.27 for WW–KR2 to 0.96 for ADG3–KR3. The moderate estimate of direct heritability for body weight, growth rate and Kleiber ratio suggests that Malpura sheep can be improved through selection for economic mutton production.

Genetic analysis of growth traits in Iranian Makuie sheep breed

The Makuie sheep is a fat-tailed sheep breed which can be found in the Azerbaijan province of Iran. In 1986, a Makuie sheep breeding station was established in the city of Maku in order to breed, protect and purify this breed. The genetic parameters for birth weight, weaning weight (3 months), 6-month, 9-month and yearling weight, and average daily gain from birth to weaning traits were estimated based on 25 years of data using DFREML software. Six different models were applied and a likelihood ratio test (LRT) was used to select the appropriate model. Bivariate analysis was used to define the genetic correlation between studied traits. Based on the LRT, model II was selected as an appropriate model for all studied traits. Direct heritability estimates of birth, weaning, 6-month, 9-month and yearling weights and average daily gain from birth to weaning were 0.36, 0.41, 0.48, 0.42, 0.36 and 0.37, respectively. Estimates of direct genetic correlation between birth and weaning weights, birth and 6-month weights, birth and 9-month weights, as well as between birth and yearling weights were 0.57, 0.49, 0.46 and 0.32, respectively. The results suggest there is a substantial additive genetic variability for studied traits in the Makuie sheep breed population, and the direct additive effect and maternal permanent environment variance are the main source of phenotypic variance.

Quantitative genetic analysis of growth traits and Kleiber ratios in Sanjabi sheep

Genetic parameters for growth traits and Kleiber ratio were estimated in Sanjabi sheep. Data collected from 1992 to 2002 in Mehregan Breeding Station in Kermanshah province at west of Iran were analyzed. Studied traits were birth weight (BW), weaning weight (WW), six-month weight (6MW), nine-month weight (9MW), yearling weight (YW), average daily gain from birth to weaning (ADG1), Kleiber ratio from birth to weaning (KR1), average daily gain from weaning to six months of age (ADG2) and Kleiber ratio from weaning to six months of age (KR2). (Co)variance components were obtained fitting different animal models using restricted maximum likelihood (REML) procedure. Akaike information criterion (AIC) was applied to determine the most appropriate model for each trait. Model including maternal genetic effects as well as direct genetic effects, without considering covariance between them, was chosen as the most appropriate model for BW, ADG1 and WW. For KR1 and 6MW the model including permanent environmental effects due to ewe over direct genetic effects was the most appropriate one. Model which included only direct genetic effects was the most suitable model for other traits (9MW, YW, ADG2 and KR2). Direct heritability estimates of 0.09, 0.15, 0.09, 0.19, 0.11, 0.14, 0.08, 0.15 and 0.07 were obtained for BW, WW, 6MW, 9MW, YW, ADG1, ADG2, KR1 and KR2, respectively. Maternal heritabilities for BW, ADG1 and WW were estimated as 0.14, 0.23 and 0.24, respectively. Ratios of phenotypic variance due to maternal permanent environmental effects were 0.11, 0.21 and 0.16 in respective order for BW, KR1 and 6MW. Estimates of direct genetic correlation among studied traits were very low to high in magnitude and varied from −0.00 for BW–KR2 to 0.99 for WW–6MW, ADG1–YW and ADG2–9MW.

Genetic Relationship of Gestation Length with Birth and Weaning Weight in Hanwoo (Bos Taurus Coreanae)

The genetic relationship of gestation length (GL) with birth and weaning weight (BW, WW) was investigated using data collected from the Hanwoo Experiment Station, National Institute of Animal Science, RDA, Republic of Korea. Analytical mixed models including birth year-season, sex of calf, linear and quadratic covariates of age of dam (days) and linear covariate of age at weaning (days) as fixed effects were used. Corresponding restricted maximum likelihood (REML) and Bayesian estimates of variance components and heritability were obtained with two models; Model 1 included only direct genetic effect and Model 2 included direct genetic, maternal genetic and permanent environmental effect. All the genetic parameter estimates from REML were corresponding to the Bayesian estimates. Direct heritability estimates for GL, BW, and WW were 0.48, 0.33 and 0.25 by Model 1. From Model 2, direct and maternal heritability estimates were 0.38 and 0.03 for GL, 0.14 and 0.05 for BW, and 0.08 and 0.05 for WW. Genetic correlation estimates between direct and maternal effects were 0.05 for GL, 0.59 for BW, and 0.52 for WW. Estimates of direct genetic correlation between GL and BW (WW) were 0.44 (0.21). Positive genetic correlation of GL with BW and WW imply that selection for greater BW or WW would lead to prolonged gestation length.

Genetic evaluation of crossbred lamb production. 4. Genetic parameters for first-cross animal performance

The study estimated heritability for lamb growth and carcass performance, hogget ewe wool production, and worm egg count among crossbred progeny of maternal breed sires, as well as the genetic and phenotypic correlations among the traits. The data were from crossbred progeny of 91 sires from maternal breeds including Border Leicester, East Friesian, Finnsheep, Coopworth, White Suffolk, Corriedale, and Booroola Leicester. The sires were mated to Merino ewes at 3 sites over 3 years (and also Corriedale ewes at one site), with 3 common sires used at each site and year to provide genetic links. These sheep comprised part of the national maternal sire central progeny test program (MCPT) to evaluate the genetic variation for economically important production traits in progeny of maternal and dual-purpose (meat and wool) sires and the scope for genetic improvement. The matings resulted in 7846 first-cross lambs born, with 2964 wether lambs slaughtered at an average age of 214 days, and wool data from 2795 hogget ewes. Data were analysed using univariate mixed models containing fixed effects for site, year, sex and type of birth and rearing, dam source and sire breed, and random terms for sire and dam effects. Heritabilities and genetic correlations were estimated based on variances from progeny of 70 sires by fitting the same mixed models using a REML procedure in univariate and multivariate analyses. Estimates of heritability were low for lamb growth traits (0.07–0.29), meat colour and meat pH (0.10–0.23), and faecal worm egg count (0.10), moderate for carcass fat and muscle traits (0.32–0.47), and moderate to high for wool traits (0.36–0.55). Estimates of direct genetic correlations among liveweights at various ages were high and positive (0.41–0.77) and those between liveweights and most carcass and meat quality traits were small and varied in sign. Liveweights were moderately to highly positively correlated with most wool traits, except fibre diameter (–0.28–0.08). The study indicates that there is genetic variation for wool, growth, carcass, and meat quality traits, as well as for faecal worm egg count, with scope for selection within Australian maternal sire breeds of sheep.

Estimates of genetic parameters and genetic trend for reproduction, weight, and wool characteristics of Polypay sheep

Abstract The objective was to describe genetic parameters and genetic changes in litter sizes at birth and weaning (LB and LW, n = 9081), birth weight (BW, n = 11,896), weaning weight (WW, n = 11,104), fleece weight and grade (FW and FG, n = 8872), and staple length (SL, n = 1805) of Polypay sheep. Direct heritability estimates from single-trait analyses were 0.11 for LB, 0.02 for LW, 0.17 for BW, 0.18 for WW, 0.68 for FW, 0.36 for FG, and 0.76 for SL. Estimates of direct genetic correlation were 0.40 between LB and LW, 0.57 between BW and WW, 0.65 between FW and SL, − 0.37 between FW and FG and − 0.70 between SL and FG. Breeding values (BV) from both single-trait and seven-trait analyses calculated using the parameters estimated from single-trait and two-trait analyses were compared across years of birth with respect to genetic trends. Estimated BV from both analyses for LB, LW, BW, WW and FW increased over time, while those for FG and SL were unchanged. Estimated changes in BV over time did not differ substantially for single-trait and seven-trait analyses, except for traits highly correlated with another trait that was responding to selection (i.e., LB, which was highly correlated to both LW and WW).

Estimates of Parameters for Genetic Relationship between Reproductive Performances and Body Condition Score of Hanwoo Cows

This study was conducted to estimate phenotypic and genetic parameters of body condition score (BCS) and reproductive traits in Hanwoo cows. DFREML procedures were applied to obtain variance-covariance components and heritability estimates with single or two-trait models. Estimates of phenotypic correlations of BCS at service with BCS at calving was 0.16 and 0.26 with calving interval, 0.08 with gestation length, and 0.06 with number of services per conception, respectively. Estimates of phenotypic correlation of BCS at calving was 0.10 with calving interval, 0.13 with gestation length, and 0.10 with number of services per conception, respectively. Estimates of phenotypic correlation were low and negative, -0.11 between calving interval and gestation length and -0.13 between gestation length and number of services per conception. Estimates of direct genetic correlation were -0.06, between BCS at service and BCS at calving, 0.37 between BCS at service and BCS at weaning, and -0.18 between BCS at calving and BCS at weaning. Estimates of direct genetic correlation of days from calving to the 1st service were 0.17 with number of services per conception and -0.21 with BCS at service. Estimates of direct genetic correlation for BCS at calving were -0.02 with number of services per conception and -0.08 with BCS at service. Estimates of direct genetic correlation for BCS at weaning were 0.02 with number of services per conception and -0.07 with BCS at service. Estimates of direct heritability from single trait analyses were 0.13 for BCS at service, 0.20 for BCS at calving, 0.02 for BCS at weaning, and 0.20 for number of service per conception, respectively. Estimates of direct heritability were 0.20 for birth weight and 0.10 for weaning weight. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 7 : 909-914)

Estimates of genetic parameters and genetic change for reproduction, weight, and wool characteristics of Rambouillet sheep

Records were for Rambouillet sheep from data collected from 1950 to 1998 at the U.S. Sheep Experiment Station, Dubois, Idaho, USA. Number of observations were 44,211 for litter size at birth and litter size at weaning, 35,604 for birth weight, 34,114 for weaning weight, 39,820 for fleece weight, 39,821 for fleece grade, and 3574 for staple length. Genetic parameters from both single- and two-trait analyses for prolificacy, weight, and wool traits were estimated using REML with animal models. Direct heritability estimates from single-trait analyses were 0.09 for litter size at birth, 0.06 for litter size at weaning, 0.27 for birth weight, 0.20 for weaning weight, 0.51 for fleece weight, 0.16 for fleece grade, and 0.58 for staple length. Estimates of direct genetic correlation between litter sizes at birth and weaning was 0.76 and between birth and weaning weights was 0.60. Estimates of genetic correlation between fleece weight and staple length was positive (0.45), but negative between fleece weight and fleece grade (−0.47) and between staple length and fleece grade (−0.52). Estimates of genetic correlations were near zero between birth weight and litter size at weaning, small and positive between birth weight and litter size at birth, and moderate and positive between weaning weight and litter size traits. Fleece weight, fleece grade, and staple length were slightly but negatively correlated with both litter size traits. Estimates of correlations between weight traits and fleece weight were positive and low to moderate. Estimates of correlations between weight traits and fleece grade were negative and small, while estimates between weight traits and staple length were positive and small. Breeding values from both single- and seven-trait analyses calculated using the parameters estimated from the single- and two-trait analyses were compared across years of birth with respect to genetic trends. Estimated breeding values averaged by year of birth from both the single- and seven-trait analyses for the prolificacy and weight traits increased over time, while those for fleece weight decreased and those for the other wool traits were unchanged. Estimated changes in breeding values over time did not differ substantially for the single- and seven-trait analyses, except for traits highly correlated with another trait that was responding to selection (i.e., litter size at birth, which was highly correlated to both litter size at weaning and weaning weight).

Genetic parameter estimates for lamb growth traits and greasy fleece weight at first shearing in Turkish Merino sheep

The aim of the current study was to estimate genetic parameters for birth weight (BW), weaning weight (WW), yearling weight (YW), average daily gain from birth to weaning (ADG) and greasy fleece weight at first shearing (GFW), which are essential to design a selection programme for Turkish Merino sheep. Data and pedigree information of Turkish Merino sheep used in this study were collected at Marmara Animal Breeding Research Institute from 1996 to 2001. Genetic parameters were estimated with single- and two-trait analyses using restricted maximum likelihood (REML) with animal models. Estimates of direct heritability were 0.08 for BW, 0.12 for WW, 0.25 for YW, 0.11 for ADG and 0.08 for GFW. Estimates of maternal heritability were 0.09, 0.04, 0.03 and 0.04 for BW, WW, YW and ADG, respectively. Estimates of maternal permanent environmental variance as a proportion of phenotypic variance were 0.19, 0.08 and 0.09 for BW, WW and ADG, respectively. Estimates of direct genetic correlations among growth traits were positive and ranged from 0.56 to 0.98. GFW had a moderate to high positive direct genetic correlation with BW, WW and ADG but not with YW (0.19). Estimates of the correlation between direct and maternal genetic effects were negative and ranged from −0.63 to −0.92 for growth traits.

Estimates of (co)variances due to direct and maternal effects for body weights in Timahdite sheep

AbstractGenetic parameters for body weights in Timahdite sheep were estimated using records of 10370 lambs from the ‘Société Nationale de Développement de l’Elevage’ born in 1988-89 to 1998-99. An animal model with derivativefree restricted maximum likelihood procedures was used. Random effects were direct and maternal additive genetic, maternal permanent environmental, and error. Direct and maternal heritability estimates were 0·05 and 0·05 for birth weight, 0·02 and 0·07 for weight at 30 days, 0·07 and 0·08 for weight at 70 days, 0·06 and 0·01 for weight at 90 days. Estimates of fraction of variance due to maternal permanent environmental effects were close to zero, except for weight at 90 days. Genetic correlations between direct and maternal genetic effects were –0·55, –0·51, –0·50 and –0·17 for body weights at birth, 30, 70 and 90 days, respectively. Estimates of direct genetic correlations among body weights were positive and high, ranging from 0·69 to unity. Phenotypic correlations were positive and moderate to high, being lower than their corresponding direct genetic correlations. Estimates of correlations between maternal genetic effects among weights were positive and high, varying from 0·79 to unity. Cross-correlations between direct genetic effects for one weight and maternal genetic effects for another weight were consistently negative, ranging from –0·05 to –0·63. These results indicate that selecting for improved maternal and/or direct effects in Timahdite sheep is expected to generate only slow genetic progress in terms of early growth.

Genetic parameter estimates of early growth traits in the Tygerhoek Merino flock

Genetic parameters were estimated for birth weight (BWT), weaning weight (WWT) and pre-weaning average daily gain (ADG) using Restricted Maximum Likelihood (REML) procedures. Four different animal models were fitted, differentiated by including or excluding maternal effects. The direct heritability estimates (h²) ranged from 0.19 to 0.38, 0.25 to 0.36 and 0.26 to 0.34 for BWT, WWT and ADG, respectively. The estimates were substantially higher when maternal effects, either genetic or environmental, were ignored from the model. The maternal heritability (m²) for BWT was 0.38 when only maternal genetic effects were fitted in the model but decreased to 0.25 when the maternal permanent environmental effect (c²) was fitted. The m² for WWT and ADG ranged from 0.05 to 0.11 and from 0.04 to 0.10, respectively. The respective c² estimates ranged from 0.06 to 0.10 and from 0.06 to 0.09. Moderate negative genetic correlations (ram)between direct and maternal genetic effects were observed in BWT, while close to zero estimates were obtained for WWT and ADG. The direct genetic correlation estimates between BWT and WWT and BWT and ADG were 0.16 and 0.04, respectively. The corresponding maternal genetic correlation estimates were 0.93 and 0.60. The direct and maternal genetic correlation estimates between WWT and ADG were 0.99 and 0.85, respectively. It is suggested that selection should be applied to WWT. South African Journal of Animal Science Vol.32(2) 2002: 66-75