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1.
Genetic parameter estimates for growth traits in Horro sheep   总被引：5，自引：0，他引：5  
Variance components and genetic parameters were estimated for growth traits: birth weight (BWT), weaning weight (WWT), 6‐month weight (6MWT) and yearling weight (YWT) in indigenous Ethiopian Horro sheep using the average information REML (AIREML). Four different models: sire model (model 1), direct animal model (model 2), direct and maternal animal model (model 3) and direct–maternal animal model including the covariance between direct and maternal effects (model 4) were used. Bivariate analysis by model 2 was also used to estimate genetic correlation between traits. Estimates of direct heritability obtained from models 1–4, respectively, were for BWT 0.25, 0.27, 0.18 and 0.32; for WWT, 0.16, 0.26, 0.1 and 0.14; for 6MWT 0.18, 0.26, 0.16 and 0.16; and for YWT 0.30, 0.28, 0.23, and 0.31. Maternal heritability estimates of 0.12 and 0.23 for BWT; 0.19 and 0.24 for WWT; 0.09 and 0.09 for 6MWT and 0.08 and 0.14 for YWT were obtained from models 3 and 4, respectively. The correlations between direct and maternal additive genetic effects for BWT, WWT, 6MWT and YWT were –0.64, –0.42, 0.002 and –0.46, respectively. On the other hand, the genetic correlations between BWT and the rest of growth traits (WWT, 6MWT and YWT, respectively) were 0.45, 0.33 and 0.31, whereas correlations between WWT and 6MWT, WWT and YWT and 6MWT and YWT were 0.98, 0.84 and 0.87, respectively. The medium to high direct and maternal heritability estimates obtained for BWT and YWT indicate that in Horro sheep faster genetic improvement through selection is possible for these traits and it should consider both (direct and maternal) h2 estimates. However, since the direct‐maternal genetic covariances were found to be negative, caution should be made in making selection decisions. The high genetic correlation among early growth traits imply that genetic improvement in any one of the traits could be made through indirect selection for correlated traits.  相似文献   

2.
The main objectives of this study were to estimate genetic and phenotypic parameters for growth traits and prolificacy in the Raeini Cashmere goat. Traits included, birth weight (BWT), weaning weight (WWT), 6-month weight (6WT), 9-month weight (9WT), 12-month weight (12WT), average daily gain from birth to weaning (ADG1), average daily gain from weaning to 6WT (ADG2), average daily gain from 6WT to 12WT (ADG3), survival rate (SR), litter size at birth (LSB) and litter size at weaning (LSW) and total litter weight at birth (LWB). Data were collected over a period of 28 years (1982-2009) at the experimental breeding station of Raeini goat, southeast of Iran. Genetic parameters were estimated with univariate models using restricted maximum likelihood (REML) procedures. In addition to an animal model, sire and threshold models, using a logit link function, were used for analyses of SR. Age of dam, birth of type, sex and of kidding had significant influence (p < 0.05 or 0.01) all the traits. Direct heritability estimates were low for prolificacy traits (0.04 ± 0.01 for LSB, 0.09 ± 0.02 for LSW, 0.16 ± 0.02 for LWB and 0.05 ± 0.02 for SR) and average daily gain (0.12 ± 0.03 for ADG1, 0.08 ± 0.02 for ADG2, and 0.07 ± 0.03 for ADG3) to moderate for production traits (0.22 ± 0.02 for BWT, 0.25 ± 0.02 for WWT, 0.29 ± 0.04 for 6WT, 0.30 ± 0.02 for 9WT, 0.32 ± 0.05 for 12WT). The estimates for the maternal additive genetic variance ratios were lower than direct heritability for BWT (0.17 ± 0.03) and WWT (0.07 ± 0.02).  相似文献   

3.
Correlations between genetic expression in lambs when dams were young (1 yr), middle-aged (2 and 3 yr), or older (older than 3 yr) were estimated with three-trait analyses for weight traits. Weights at birth (BWT) and weaning (WWT) and ADG from birth to weaning were used. Numbers of observations were 7,731, 9,518, 9,512, and 9,201 for Columbia (COLU), Polypay (POLY), Rambouillet (RAMB), and Targhee (TARG) breeds of sheep, respectively. When averaged, relative estimates for WWT and ADG were similar across breeds. Estimates were variable across breeds. On average, direct heritability was greater when environment was young dams (.44 for BWT and .34 for WWT) than when environment was dams of middle age or older (.24 and .28 for BWT and .20 and .16 for WWT, respectively). Maternal heritability was greater when dams were middle-aged or older (.28 and .22 vs .18) for BWT but was greater when dams were younger (.10 vs .05 and .04) for WWT. The estimates of genetic correlations for direct effects across age of dam environments averaged .32 for birth weight and averaged .70 for weaning weight. Average estimates of maternal genetic correlations across age of dam classes were .36 or less for both BWT and WWT. Average estimates of correlations among maternal permanent environmental effects were .49 or less across age of dam classes. Total maternal effects accounted for .33 to .42 of phenotypic variance for BWT and for .09 to .26 of phenotypic variance for WWT. The average estimates of genetic correlations between expressions of the same genotypes with different ages of dams suggest that measurements of BWT of lambs with dams in young, middle, and older age classes should be considered to be separate traits for genetic evaluation and that for WWT measurements with young age of dam class and combined middle and older age of dam classes should be considered to be separate traits for genetic evaluation.  相似文献   

4.
Records of 9,055 lambs from a composite population originating from crossing Columbia rams to Hampshire x Suffolk ewes at the U.S. Meat Animal Research Center were used to estimate genetic parameters among growth traits. Traits analyzed were weights at birth (BWT), weaning (7 wk, WWT), 19 mo (W19), and 31 mo (W31) and postweaning ADG from 9 to 18 or 19 wk of age. The ADG was also divided into daily gain of males (DGM) and daily gain of females (DGF). These two traits were analyzed with W19 and with W31 in three-trait analyses. (Co)variance components were estimated with REML for an animal model that included fixed effects of sex, age of dam, type of birth or rearing, and contemporary group. Random effects were direct and maternal genetic of animal and dam with genetic covariance, maternal permanent environmental, and random residual. Estimates of direct heritability were .09, .09, .35, .44, .19, .16, and .23 for BWT, WWT, W19, W31, ADG, DGM, and DGF, respectively. Estimates of maternal permanent environmental variance as a proportion of phenotypic variance were .09, .12, .03, .03, .03, .06, and .02, respectively. Estimates of maternal heritability were .17 and .09 for BWT and WWT and .01 to .03 for other traits. Estimates of genetic correlations were large among W19, W31, and ADG (.69 to .97), small between BWT and W31 or ADG, and moderate for other pairs of traits (.32 to .45). The estimate of genetic correlation between DGM and DGF was .94, and the correlation between maternal permanent environmental effects for these traits was .56. For the three-trait analyses, the genetic correlations of DGM and DGF with W19 were .69 and .82 and with W31 were .67 and .67, respectively. Results show that models for genetic evaluation for BWT and WWT should include maternal genetic effects. Estimates of genetic correlations show that selection for ADG in either sex can be from records of either sex (DGM or DGF) and that selection for daily gain will result in increases in mature weight but that BWT is not correlated with weight at 31 mo.  相似文献   

5.
The objective of this study was to examine the feasibility of using random regression-spline (RR-spline) models for fitting growth traits in a multibreed beef cattle population. To meet the objective, the results from the RR-spline model were compared with the widely used multitrait (MT) model when both were fit to a data set (1.8 million records and 1.1 million animals) provided by the American Gelbvieh Association. The effect of prior information on the EBV of sires was also investigated. In both RR-spline and MT models, the following effects were considered: individual direct and maternal additive genetic effects, contemporary group, age of the animal at measurement, direct and maternal heterosis, and direct and maternal additive genetic mean effect of the breed. Additionally, the RR-spline model included an individual direct permanent environmental effect. When both MT and RR-spline models were applied to a data set containing records for weaning weight (WWT) and yearling weight (YWT) within specified age ranges, the rankings of bulls' direct EBV (as measured via Pearson correlations) provided by both models were comparable, with slightly greater differences in the reranking of bulls observed for YWT evaluations (>or=0.99 for BWT and WWT and >or=0.98 for YWT); also, some bulls dropped from the top 100 list when these lists were compared across methods. For maternal effects, the estimated correlations were slightly smaller, particularly for YWT; again, some drops from the top 100 animals were observed. As in regular MT multibreed genetic evaluations, the heterosis effects and the additive genetic effects of the breed could not be estimated from field data, because there were not enough contemporary groups with the proper composition of purebred and crossbred animals; thus, prior information based on literature values had to be included. The inclusion of prior information had a negligible effect in the overall ranking for bulls with greater than 20 birth weight progeny records; however, the effect of prior information for breeds or groups poorly represented in the data was important. The Pearson correlations for direct and maternal WWT and YWT ranged from 0.95 to 0.98 when comparing evaluations of data sets for which the out-of-range age records were removed or retained. Random regression allows for avoiding the discarding of records that are outside the usual age ranges of measurement; thus, greater accuracies are achieved, and greater genetic progress could be expected.  相似文献   

6.
Data were collected over a period of 21 years (1988–2008) to estimate (co)variance components for birth weight (BWT), weaning weight (WWT), 6-month weight (6WT), 9-month weight (9WT), 12-month weight (12WT), average daily gain from birth to weaning (ADG1), weaning to 6WT (ADG2), and from 6WT to 12WT (ADG3) in Sirohi goats maintained at the Central Sheep and Wool Research Institute, Avikanagar, Rajasthan, India. Analyses were carried out by restricted maximum likelihood, fitting six animal models with various combinations of direct and maternal effects. The best model was chosen after testing the improvement of the log-likelihood values. Heritability estimates for BWT, WWT, 6WT, 9WT, 12WT, ADG1, ADG2, and ADG3 were 0.39 ± 0.05, 0.09 ± 0.03, 0.06 ± 0.02, 0.09 ± 0.03, 0.11 ± 0.03, 0.10 ± 0.3, 0.04 ± 0.02, and 0.01 ± 0.01, respectively. For BWT and ADG1, only direct effects were significant. Estimate of maternal permanent environmental effect were important for body weights from weaning to 12WT and also for ADG2 and ADG3. However, direct maternal effects were not significant throughout. Estimate of c 2 were 0.06 ± 0.02, 0.03 ± 0.02, 0.06 ± 0.02, 0.05 ± 0.02, 0.02 ± 0.02, and 0.02 ± 0.02 for 3WT, 6WT, 9WT, 12WT, ADG2, and ADG3, respectively. The estimated repeatabilities across years of ewe effects on kid body weights were 0.10, 0.08, 0.05, 0.08, and 0.08 at birth, weaning, 6, 9, and 12 months of age, respectively. Results suggest possibility of modest rate of genetic progress for body weight traits and ADG1 through selection, whereas only slow progress will be possible for post-weaning gain. Genetic and phenotypic correlations between body weight traits were high and positive. High genetic correlation between 6WT and 9WT suggests that selection of animals at 6 months can be carried out instead of present practice of selection at 9 months.  相似文献   

7.
Data were analyzed to estimate the effects of heterosis and breed on a series of maternal and individual traits. Crossbred cows were Boran X Ankole and Boran X Zebu; straight-bred cows were Ankole, Boran and Small East African Zebu (Zebu). Cows of all breed groups were mated to Friesian, Brown Swiss and Simmental sires to produce crossbred progeny. While not generally significant, the average effects of heterosis of both crosses for the traits analyzed were: calf crop born, 7.0%; preweaning viability, 7.2%; overall viability, 7.3%; birth weight, 6.0%; weaning weight, 5.4%; 12-mo weight, 4.2%; 18-mo weight, 3.7%; 24-mo weight, 3.6%; calf weight weaned per cow exposed to breeding (cow productivity index), 24.5%; cow parturition weight, 3.5%; cow weaning weight, 4.2% and cow mean weight, 4.0%. Boran cows weaned 31.8 kg (48.0%) more (P less than .05) calf weight per cow exposed to breeding than Ankole cows. Boran cows were generally superior to Zebu cows in progeny weights at all ages (P less than .01). Boran cows weaned 34.5 kg (54.3%) more (P less than .05) calf weight per cow exposed to breeding than Zebu cows. Boran cows weighed an average of 70.8 kg more (P less than .01) than Zebu cows. Although progeny of Ankole dams were heavier (P less than .05) than the progeny of Zebu dams at all ages, the two breeds did not differ (P greater than .05) in calf weight weaned per cow exposed to breeding. Mean weight of Ankole cows was 75.8 kg heavier (P less than .01) than mean weight of Zebu cows.  相似文献   

8.
Estimates of direct and maternal genetic parameters in beef cattle were obtained with a random regression model with a linear spline function (SFM) and were compared with those obtained by a multitrait model (MTM). Weight data of 18,900 Gelbvieh calves were used, of which 100, 75, and 17% had birth (BWT), weaning (WWT), and yearling (YWT) weights, respectively. The MTM analysis was conducted with a three-trait maternal animal model. The MTM included an overall linear partial fixed regression on age at recording for WWT and YWT, and direct-maternal genetic and maternal permanent environmental effects. The SFM included the same effects as MTM, plus a direct permanent environmental effect and heterogeneous residual variance. Three knots, or breakpoints, were set to 1, 205, and 365 d. (Co)variance components in both models were estimated with a Bayesian implementation via Gibbs sampling using flat priors. Because BWT had no variability of age at recording, there was good agreement between corresponding components of variance estimated from both models. For WWT and YWT, with the exception of the sum of direct permanent environmental and residual variances, there was a general tendency for SFM estimates of variances to be lower than MTM estimates. Direct and maternal heritability estimates with SFM tended to be lower than those estimated with MTM. For example, the direct heritability for YWT was 0.59 with MTM, and 0.48 with SFM. Estimated genetic correlations for direct and maternal effects with SFM were less negative than those with MTM. For example, the direct-maternal correlation for WWT was -0.43 with MTM and -0.33 with SFM. Estimates with SFM may be superior to MTM due to better modeling of age in both fixed and random effects.  相似文献   

9.
Breed additive and non‐additive effects plus heritabilities and repeatabilities for milk yield per lactation (LMY), milk yield per day (DMY), lactation length (LL), annual milk yield (AMY), annual milk yield per metabolic body weight (AMYBW) and cow weight at calving (BW) were estimated for 5464 lactation records collected from purebred Boran (B), Friesian (F), and crosses of Friesian and Jersey (J) breeds with the Boran breed raised in the tropical highlands of Ethiopia. Single trait analysis was carried out by using two equivalent repeatability animal models. In the first model the genotype was fitted as a fixed group effect, while in the second model the genotype was substituted by breed additive, heterotic and recombination effects fitted as fixed covariates. Both the F and J breed additive effects, measured as a deviation from the B breed were significant (p < 0.01) for all traits, except for BW of the J. The F and J additive contributions were 2774 ± 81 and 1473 ± 362 kg for LMY, 7.1 ± 0.2 and 4.8 ± 0.8 kg for DMY, 152 ± 7 and 146 ± 31 days for LL, 2345 ± 71 and 1238 ± 319 kg for AMY, 20.6 ± 0.9 and 18.9 ± 4.3 kg for AMYBW, and 140 ± 4 and ?21 ± 22 kg (p > 0.05) for BW. The heterotic contributions to the crossbred performance were also positive and significant (p < 0.01) for all traits. The F1 heterosis expressed as a deviation from the mid‐parent values were 22 and 66% for LMY, 11 and 20% for DMY, 29 and 29% for LL, 21 and 64% for AMY, 42 and 42% for AMYBW, and 2% (p < 0.05) and 11% for BW for the F × B and J × B crosses, respectively. The recombination effect estimated for the F × B crosses was negative and significant for LMY (?526 ± 192 kg, p < 0.01), DMY (?3.0 ± 0.4 kg, p < 0.001), AMY (?349 ± 174 kg, p < 0.05) and BW (?68 ± 11 kg, p < 0.001). For the J × B crosses the recombination loss was significant and negative only for DMY (?2.2 ± 0.7 kg, p < 0.05) and BW (?33 ± 17 kg, p < 0.05). The direct heritabilities (h2) estimated for LMY, DMY, LL, AMY and AMYBW were 0.24 ± 0.04, 0.19 ± 0.03, 0.13 ± 0.03, 0.23 ± 0.04 and 0.17 ± 0.05, respectively. Based on the genetic parameters estimated, the best breeding strategy to increased milk production under highland Ethiopian conditions is to apply selection on purebred base populations (Boran and Friesian) and then crossing them to produce F1 dairy cows. However, for breeding decision based on total dairy merit, further investigations are needed for traits such as milk quality, reproduction, longevity and survival.  相似文献   

10.
Variance components and genetic parameters were estimated using data recorded on 740 young male Japanese Black cattle during the period from 1971 to 2003. Traits studied were feed intake (FI), feed‐conversion ratio (FCR), residual feed intake (RFI), average daily gain (ADG), metabolic body weight (MWT) at the mid‐point of the test period and body weight (BWT) at the finish of the test (345 days). Data were analysed using three alternative animal models (direct, direct + maternal environmental, and direct + maternal genetic effects). Comparison of the log likelihood values has shown that the direct genetic effect was significant (p < 0.05) for all traits and that the maternal environmental effects were significant (p < 0.05) for MWT and BWT. The heritability estimates were 0.20 ± 0.12 for FI, 0.14 ± 0.10 for FCR, 0.33 ± 0.14 for RFI, 0.19 ± 0.12 for ADG, 0.30 ± 0.14 for MWT and 0.30 ± 0.13 for BWT. The maternal effects (maternal genetic and maternal environmental) were not important in feed‐efficiency traits. The genetic correlation between RFI and ADG was stronger than the corresponding correlation between FCR and ADG. These results provide evidence that RFI should be included for genetic improvement in feed efficiency in Japanese Black breeding programmes.  相似文献   

11.
Data from purebred and crossbred calves, consisting of Afrikaner (AF), Charolais (CH), Simmental (ST) and Hereford and Aberdeen Angus combined (HA), were analyzed to estimate breed additive effects, breed maternal effects, average individual heterosis and average maternal heterosis. The traits studied were birthweight (BW), weaning weight (WW) and preweaning average daily gain (ADG) (kg). A multiple regression procedure was used for the estimation of these genetic effects and for predictions for breed crosses that were not included in the data set. Crosses containing higher proportions of CH or ST were heavier at birth and weaning than the other crosses and purebreds. The direct effects of BW were negative and significant (P < 0.05), except that of the CH, which was the highest. The regression coefficients were ?24.87, ?18.16, ?22.80 and ?27.02 for AF, CH, ST and HA, respectively. The maternal effects were not significant. Both average individual and average maternal heterosis regression coefficients were also not significant for BW. Regression coefficients of both direct and maternal effects for WW were not significant and were characterized by large standard errors. Average individual heterosis and average maternal heterosis regression coefficients were, however, significant (P < 0.01) and the values were 5.34 and 2.19, respectively. A similar pattern was observed for ADG, except for the regression coefficients of the maternal effects, which were significant, with larger estimates for AF and ST reflecting their superior mothering ability. The values were 0.01, 0.13, 0.13, 0.03; ?0.82, ?0.85, ?0.85, ?0.81; 0.03 and 0.01 for direct effects and maternal effects of AF, CH, ST and HA; and average individual heterosis and average maternal heterosis, respectively. Means and standard errors of purebreds and their F1 crosses not included in the dataset were predicted.  相似文献   

12.
The purpose of the present study was to obtain estimates of variance components and genetic parameters for direct and maternal effects on various growth traits in Beetal goat by fitting four animal models, attempting to separate direct genetic, maternal genetic and maternal permanent environmental effects under restricted maximum likelihood procedure. The data of 3,308 growth trait records of Beetal kids born during the period from 2004 to 2019 were used in the present study. Based on best fitted models, the direct additive h2 estimates were 0.06, 0.27, 0.37, 0.17 and 0.10 for birth weight (BWT), weight at 3 (WT3), 6 (WT6), 9 (WT9) and 12 (WT12) months of age, respectively. Maternal permanent environmental effects significantly contributed for 10% and 7% of total variance for BWT and WWT, respectively, which reduced direct heritability by 40 and 10% for respective traits from the models without these effects. For average daily gain (ADG1) and Kleiber ratios (KR1) up to weaning period (3 months) traits, maternal permanent environmental effects accounted for 7% and 8% of phenotypic variance, respectively, and resulted in a reduction of 6.6% and 5.4% in direct h2 of respective traits. For post-weaning traits, the maternal effects were non-significant (p > .05) which indicates diminishing influence of mothering ability for these traits. High and positive genetic correlations were obtained among WT3-WT6, WT6-WT9 and WT9-WT12 with correlations of 0.96 ± 0.25, 0.84 ± 0.23 and 0.90 ± 0.13, respectively. Thus, early selection at weaning age can be practised taking into consideration maternal variation for effective response to selection in Beetal goat.  相似文献   

13.
The objective of this study was to estimate variance and covariance components, in Iranian Cashmere goats, for birth weight (BWT) and weaning weight (WWT) performances of kids and total weight of kids weaned (TWW) per doe joined at first (TWW1), second (TWW2) and third (TWW3) parities by REML procedures using univariate and multivariate animal models. The analysis was based on 2313 records of kids and 940 records of does. Through ignoring or including maternal additive genetic or maternal permanent environmental effects, four different models were fitted for BWT and WWT performances. For TWW performances only two models (without or with service sire effect) were used. Models were compared using likelihood ratio test. Direct additive genetic and maternal permanent environmental effects had significant influence on BWT and WWT performances. These effects accounted for 9.4% and 15.6%, and 13.9% and 6.7% of phenotypic variation, respectively. No significant effect of service sire was observed on TWW. The estimates of heritabilities were 0.072, 0.109 and 0.082 for TWW1, TWW2 and TWW3, respectively. Direct genetic correlations among all performances were positive and low (for BWT with TWW) to high (for BWT with WWT and WWT with TWW). The corresponding estimates for phenotypic and residual correlations were moderate and lower than genetic correlations. The high genetic correlation among WWT and TWW suggests that direct selection on TWW1 or indirect selection on WWT would increase total weight of kids weaned per doe joined.  相似文献   

14.
Estimates of (co)variance components and genetic parameters were calculated for birth weight (BWT), weaning weight (WWT), 6 month weight (6WT), 9 month weight (9WT), 12 month weight (12WT) and greasy fleece weight at first clip (GFW) for Malpura sheep. Data were collected over a period of 23 years (1985–2007) for economic traits of Malpura sheep maintained at the Central Sheep & Wool Research Institute, Avikanagar, Rajasthan, India. Analyses were carried out by restricted maximum likelihood procedures (REML), fitting six animal models with various combinations of direct and maternal effects. Direct heritability estimates for BWT, WWT, 6WT, 9WT, 12WT and GFW from the best model (maternal permanent environmental effect in addition to direct additive effect) were 0.19 ± 0.04, 0.18 ± 0.04, 0.27, 0.15 ± 0.04, 0.11 ± 0.04 and 0.30 ± 0.00, respectively. Maternal effects declined as the age of the animal increased. Maternal permanent environmental effects contributed 20% of the total phenotypic variation for BWT, 5% for WWT and 4% for GFW. A moderate rate of genetic progress seems possible in Malpura sheep flock for body weight traits and fleece weight by mass selection. Direct genetic correlations between body weight traits were positive and ranged from 0.40 between BWT and 6WT to 0.96 between 9WT and 12WT. Genetic correlations of GFW with body weights were 0.06, 0.49, 0.41, 0.19 and 0.15 from birth to 12WT. The moderately positive genetic correlation between 6WT and GFW suggests that genetic gain in the first greasy fleece weight will occur if selection is carried out for higher 6WT.  相似文献   

15.
Evidence of heterogeneity of parameters and genotype by country interactions was investigated for birth weight (BWT), weaning weight (WWT) and postweaning gain (PWG) between Australian (AUS), Canadian (CAN), New Zealand (NZ) and USA populations of Charolais cattle. An animal model was fit to data sets for each individual country to compare the within-country parameter estimates for homogeneity. The direct heritability estimates of BWT in AUS (0.34) and NZ (0.31) were less than CAN (0.55) and USA (0.47). Maternal BWT heritabilities (0.13–0.18), direct WWT heritabilities (0.22–0.27), and maternal WWT heritabilities (0.12–0.18) were similar across all four countries. Direct PWG heritability for AUS (0.14) was smaller than the same estimate in the other three countries (0.24–0.31). The phenotypic variances for all three traits were similar across AUS, CAN and USA; however, NZ was higher for BWT and WWT and lower for PWG. A multiple trait animal model that considered each trait as a different trait in each country was also fit to the data for pairs of countries. Direct (maternal) estimated genetic correlations for BWT for AUS–CAN, AUS–USA, USA–CAN, NZ–CAN and NZ–USA were 0.88 (0.86), 0.85 (0.82), 0.88 (0.82), 0.85 (0.83), and 0.84 (0.80), respectively. Direct (maternal) estimated genetic correlations for WWT for AUS–CAN, AUS–USA, USA–CAN, NZ–CAN and NZ–USA were 0.96 (0.91), 0.95 (0.90), 0.95 (0.91), 0.95 (0.92), and 0.95 (0.92), respectively. Direct estimated genetic correlations for PWG for AUS–CAN, AUS–USA, USA–CAN, NZ–CAN and NZ–USA were 0.89, 0.91, 0.94, 0.90, and 0.91, respectively. The magnitude of the across-country genetic correlations indicates that genotype by country interactions were biologically unimportant. However, strong evidence exists for heterogeneity of parameters across the countries for some traits and effects. Therefore, combining these countries into one single analysis to produce a common set of genetic values will depend on the development of methods to adjust for heterogeneous parameters for models containing both direct and maternal effects, and for circumstances where constant variance ratios or heritabilities are not present across populations.  相似文献   

16.
The effects of heterosis for gestation length, dystocia, calf survival, birth weight, 200-d weight, and ADG from birth to weaning were evaluated in F1, F2, and combined F3 and F4 generations in three composite populations. Breed effects were evaluated for the nine parental breeds (Red Poll, Hereford, Angus, Limousin, Braunvieh, Pinzgauer, Gelbvieh, Simmental, and Charolais) that contributed to the three composite populations. Breed effects were significant for all traits evaluated except survival at birth. The large differences among breeds in additive direct and additive maternal genetic effects offer a great opportunity to use the genetic differences among breeds to achieve and maintain optimum additive genetic (breed) composition to match genetic resources to a wide range of production-marketing ecosystems. There was no heterosis for gestation length. Mean heterosis for dystocia was significant estimated in F1 but not in F2 or in the combined F3 and F4 generations. Mean heterosis was not significant in any generation for survival at birth, to 72 h, and to weaning for the F1 generation; mean heterosis was significant for survival to weaning for the F2 generation and approached significance (P = .06) for the combined F3 and F4 generations. Mean heterosis over all composite populations and heterosis for each composite population were significant in all generations for weight at birth and at 200 d and for ADG from birth to weaning. Retained heterosis was not less than expected from retained heterozygosity in composite populations for the traits evaluated. These results suggest that heterosis for these traits likely is due to dominance effects and, thus, can be attributed to the recovery of accumulated inbreeding depression in the parental breeds.  相似文献   

17.
A study with the objectives of estimating breed differences, heterosis and recombination effects as well as heritabilities (h2) and repeatabilities (r2) for age at first calving (AFC), calving interval (CI), days open (DO) and number of services per conception (SPC) was conducted using reproduction records collected from 1496 cows comprising purebred Boran (B), Friesian (F), crosses of Friesian and Jersey (J) with Boran breeds. The crossbred cow groups included four F × B crosses [1/2F:1/2B(F1), 1/2F:1/2B(F2), 5/8F:3/8B and 3/4F:1/4B], three J × B crosses [1/2J:1/2B(F1), 1/2J:1/2B(F2) and 3/4J:1/4B] and one three‐breed cross (1/4F:1/4J:1/2B). The crossbreeding parameters were estimated using a repeatability animal model for CI, DO and SPC, and a unitrait animal model for AFC. The overall least‐squares means estimated were: 38.3 ± 0.26 months, 435 ± 4 days, 145 ± 10 days and 1.58 ± 0.03 (number) for AFC, CI, DO and SPC, respectively. The breed additive effects of F and J were only significant (p < 0.01) for AFC. Relative to B, both F and J additive contributions for AFC were ?5.4 ± 0.5 and ?5.5 ± 1.9 months, respectively. Crossing the B with F and J breeds also resulted in significant heterosis (p < 0.05) ranging from 10 to 21% in all traits. The estimated recombination loss was only significant for AFC (2.8 ± 1.0 months) for F × B crosses. Heritability estimates were high for AFC (0.44 ± 0.05) and low for CI (0.08 ± 0.03), DO (0.04 ± 0.03) and SPC (0.08 ± 0.02). The corresponding estimates for the repeatability (r2) were 0.14 ± 0.02 and 0.14 ± 0.02 for CI and DO, respectively. The permanent environmental effect for SPC was zero. These findings show that breed differences between F or J and B, and the individual cow variations are low for reproductive traits studied, except for AFC. Heterotic effects seem to be the major genetic causes for the improved reproductive performances in both the F × B and J × B crossbred cows.  相似文献   

18.
The objectives of this work were to evaluate birth and weaning traits, to estimate genetic effects, including heterosis and direct and maternal breed effects, and to evaluate calving difficulty, calf vigor at birth, and calf mortality of Romosinuano as purebreds and as crosses with Brahman and Angus. Calves (n = 1,348) were spring-born from 2002 through 2005 and weaned in the fall of each year at about 7 mo of age. Traits evaluated included birth and weaning weight, ADG, BCS, and weaning hip height. Models used to analyze these traits included the fixed effects of year, sire and dam breeds, management unit, calf sex, cow age, and source of Angus sire (within or outside of the research herd). Calf age in days was investigated as a covariate for weaning traits. Sire within sire breed and dam within dam breed were random effects. Estimates of Romosinuano-Brahman and Romosinuano-Angus heterosis (P < 0.05) were 2.6 +/- 0.3 (8.6%) and 1.4 +/- 0.3 kg (4.7%) for birth weight, 20.5 +/- 1.5 (9.5%) and 14.6 +/- 1.4 kg (7.4%) for weaning weight, 79.2 +/- 6.1 (9.8%) and 55.1 +/- 6.0 g (7.5%) for ADG, 0.16 +/- 0.03 (2.7%) and 0.07 +/- 0.03 (1.2%) for BCS, and 2.77 +/- 0.32 cm (2.4%) and 1.87 +/- 0.32 cm (1.7%) for hip height. Heterosis for Brahman-Angus was greater (P < 0.05) than all Romosinuano estimates except those for Romosinuano-Brahman and Romosinuano-Angus BCS. Romosinuano direct effects were negative and lowest of the breeds, except for the Angus estimate for hip height. Romosinuano maternal effects were the largest of the 3 breeds for birth weight and hip height but intermediate to the other breeds for weaning weight and ADG. A large proportion of Brahman-sired calves from Angus dams (0.09 +/- 0.03; n = 11) was born in difficult births and died before 4 d of age. Brahman and Angus purebreds and Romosinuano-sired calves from Brahman dams also had large proportions of calves that died before weaning (0.09 or greater). Results indicated that Romosinuano may be used as a source of adaptation to subtropical environments and still incorporate substantial crossbred advantage for weaning traits, although not to the extent of crosses of Brahman and Angus.  相似文献   

19.
The study was conducted to assess early-expressed reproductive traits of Boran cattle and their crosses with Jersey and Holstein Friesian (HF). The traits studied were age at first services (AFS), number of services for first conception, age at first calving (AFC), first dry period (FDP), first calving interval (FCI), and first service period (FSP). Genetic group and period of birth/calving had a significant (p?<?0.05) effect on reproductive traits. The Boran cattle were inferior to HF or Jersey crosses. First crosses (F 1) for Jersey and Boran (50 % Jersey: 50 % Boran) showed a significantly (p?<?0.05) younger AFS (by 7.25 months) and AFC (by 10.75 months), had shorter FCI (by 63.27 days), FDP (by 61.13 days), and FSP (by 60.3 days), and needed less (by 0.35) numbers of services per first conception as compared to the Boran cattle. The F 1 for Jersey and Boran (50 % Jersey: 50 % Boran) crosses showed better performance than the F 1 for HF and Boran (50 % HF: 50 % Boran). Heritability values for AFS and AFC were the highest and were estimated at 0.51?±?0.10 and 0.49?±?0.13, respectively, and lowest heritability was recorded for FDP (0.02?±?020) and FSP (0.10?±?0.29). The genetic correlation was highest (0.10?±?0.20) between AFS and AFC and was lowest (?0.01?±?0.66) between FCI and FSP. The breed additive for Jersey was only significant (p?<?0.01) for AFS and AFC. The crossing of HF with Boran cattle has desirably reduced 9.16?±?2.88 months in AFS; the corresponding reduction in AFS was 3.49?±?3.59 months by crossing with Jersey. The performance comparisons and genetic and crossbreeding parameters indicated that crossbreeding of Boran with HF or Jersey can improve reproductive performance.  相似文献   

20.
Heterosis effects for birth weight, ADG from birth to weaning, 200-d weight, ADG from weaning to 368 d, 368-d weight, 368-d height, 368-d condition score, and 368-d muscling score (males only) were evaluated separately for each sex in F1, F2, and combined F3 and F4 generations in three composite beef cattle populations. Breed effects were evaluated for the nine parental breeds (i.e., Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 C, 1/4 B, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, 1/4 A). Breed effects were significant for all traits evaluated. The large differences among breeds for growth and size traits in combined additive direct and additive maternal genetic effects (Gi + Gm) provide an opportunity to use genetic differences among breeds to achieve and maintain optimum additive genetic (breed) composition for growth and size traits to match cattle genetic resources to a wide range of production and marketing situations. Combined individual and maternal heterosis was significant in the F1, F2, and combined F3 and F4 generations for each composite population and for the mean of the three composite populations in both sexes for most of the traits evaluated. In both sexes, heterosis retained in combined F3 and F4 generations was greater (P less than .05) than expected based on retained heterozygosity for birth weight, ADG from weaning to 368 d, and for 368-d weight and did not differ (P greater than .05) from expectation for other traits. These results support the hypothesis that heterosis in cattle for traits related to growth and size is due to dominance effects of genes.  相似文献   

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