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1.
Estimates of (co)variance components were obtained for weights at birth, weaning and 6, 9 and 12 months of age in Chokla sheep maintained at the Central Sheep and Wool Research Institute, Avikanagar, Rajasthan, India, over a period of 21 years (1980–2000). Records of 2030 lambs descended from 150 rams and 616 ewes were used in the study. Analyses were carried out by restricted maximum likelihood (REML) fitting an animal model and ignoring or including maternal genetic or permanent environmental effects. Six different animal models were fitted for all traits. The best model was chosen after testing the improvement of the log-likelihood values. Direct heritability estimates were inflated substantially for all traits when maternal effects were ignored. Heritability estimates for weight at birth, weaning and 6, 9 and 12 months of age were 0.20, 0.18, 0.16, 0.22 and 0.23, respectively in the best models. Additive maternal and maternal permanent environmental effects were both significant at birth, accounting for 9% and 12% of phenotypic variance, respectively, but the source of maternal effects (additive versus permanent environmental) at later ages could not be clearly identified. The estimated repeatabilities across years of ewe effects on lamb body weights were 0.26, 0.14, 0.12, 0.13, and 0.15 at birth, weaning, 6, 9 and 12 months of age, respectively. These results indicate that modest rates of genetic progress are possible for all weights.  相似文献   

2.
An understanding of influencing factors and genetic principles affecting the growth traits is needed to implement optimal breeding and selection programs. In this study, heritabilities (direct additive and maternal) of body weights at birth (BW0), 90 days (BW90) and 300 days (BW300) of age and average daily gains from birth to 90 days (ADG0-90), birth to 300 days (ADG0-300) and 90 days to 300 days (ADG90–300) of age in Boer goats were estimated on the basis of 1520 Boer goats at Boer Goat Breeding Station in Yidu, China, during 2002–2007. The parameters were estimated using a DFREML procedure by excluding or including maternal genetic or permanent maternal environmental effects, four analysis models were fitted in order to optimize the model for each trait. Influencing factors such as parity, litter size, kidding year and season, as well as sex of kids and some significant interactions among these factors were investigated as the fixed effects for the models. The results showed that the birth year and maternal genetic effects such as parity and litter size of dam were important determinants of the genetic parameter estimates for pre-weaning growth traits, and environmental effects such as birth year, season and sex of kids had some significant effect on post-weaning growth traits. The mean values and standard errors (SE) of direct additive heritability estimates calculated with the optimum model were 0.17 ± 0.07, 0.22 ± 0.08, 0.07 ± 0.07, 0.10 ± 0.08, 0.30 ± 0.12 and 0.08 ± 0.10 for BW0, BW90, ADG0-90, BW300, ADG0-300 and ADG90–300, respectively. For pre-weaning weights, correlation estimates between direct additive and maternal genetic (ra–m) effect were high and negative ranging from − 0.74 to − 0.86.  相似文献   

3.
Weight records of Brazilian Nelore cattle, from birth to 630 d of age, recorded every 3 mo, were analyzed using random regression models. Independent variables were Legendre polynomials of age at recording. The model of analysis included contemporary groups as fixed effects and age of dam as a linear and quadratic covariable. Mean trends were modeled through a cubic regression on orthogonal polynomials of age. Up to four sets of random regression coefficients were fitted for animals' direct and maternal, additive genetic, and permanent environmental effects. Changes in measurement error variances with age were modeled through a variance function. Orders of polynomial fit from three to six were considered, resulting in up to 77 parameters to be estimated. Models fitting random regressions modeled the pattern of variances in the data adequately, with estimates similar to those from corresponding univariate analysis. Direct heritability estimates decreased after birth and tended to be lowest at ages at which maternal effect estimates tended to be highest. Maternal heritability estimates increased after birth to a peak around 110 to 120 d of age and decreased thereafter. Additive genetic direct correlation estimates between weights at standard ages (birth, weaning, yearling, and final weight) were moderate to high and maternal genetic and environmental correlations were consistently high.  相似文献   

4.
Genetic breed differences, heterosis, recombination loss, and heritability for reproduction traits, lamb survival and growth traits to 90 days of age were estimated from crossing D'man and Timahdite Moroccan breeds. The crossbreeding parameters were fitted as covariates in the model of analysis. The REML method was used to estimate (co)variance components using an animal model. The first estimation of crossbreeding effects for Timahdite and D'man breeds shows that breed differences in litter traits are mainly of maternal genetic origin: +1.04 lambs, +1.88 kg, +0.60 lambs, and +2.23 kg in favour of D'man breed for litter size at lambing, litter weight at lambing, litter size at weaning, and litter weight at 90 days, respectively. The breed differences in lamb growth and survival are also of maternal genetic origin for the majority of traits studied, but in favour of the Timahdite breed: +3.48 kg, +45 g day−1 and +0.19 lambs for weight at 90 days, for average daily gain between 30 and 90 days of age, and for lamb survival to 90 days, respectively. The D'man direct genetic effect was low and negative for survival and birth weight of lambs during the first month of life. All traits studied showed positive heterosis effects. Recombination loss effects were not significant. Therefore, crossbreeding of Timahdite with D'man breeds of sheep can result in an improved efficiency of production of saleable lambs. Heritability estimates were medium for litter size but low for the other reproduction traits. Direct heritabilities were low for body weights and lamb survival at 90 days and the corresponding maternal heritabilities showed, however, low to moderate estimates. For litter traits, the estimates of genetic and phenotypic correlations were positive and particularly high for genetic correlations.  相似文献   

5.
The aim of this study was to estimate genetic parameters for prenatal (PRE) and postnatal (POS) mortality in Nellore cattle. A total of 13 141 (PRE) and 17 818 (POS) records from Nellore females were used. PRE and POS were recorded using binary scale scores: a score of ‘1’ was given to calves that were born alive (PRE) and those that were alive at weaning (POS), and a score of ‘0’ was given to calves that were not alive at or around birth (PRE), as well as to those weighed at birth but not at weaning (POS). The relationship matrix included 698 sires, 107 paternal grandsires and 69 maternal grandsires. Data were analysed using Bayesian inference and a sire–maternal grandsire threshold model, including contemporary groups as random effects, and the classes of dam age at the beginning of mating season (for PRE), and dam age at calving and birthweight (linear covariable) (for POS), as fixed effects. For both traits, the covariance between direct and maternal effects (rD,M) was estimated (rD,M≠ 0) or fixed at zero (rD,M = 0). PRE and POS rates were 3.00 and 4.04%, respectively. Estimates of direct and maternal heritability were 0.07 and 0.17, respectively, for PRE, and 0.02 and 0.07, respectively, for POS, assuming rD,M = 0. For rD,M ≠ 0, these estimates were 0.07 and 0.12, respectively, for PRE, and 0.03 and 0.07, respectively, for POS. The correlation estimates between direct and maternal effects were ?0.71 (PRE) and ?0.33 (POS). PRE and POS show low genetic variability, indicating that these traits probably suffer major environmental influences. Additionally, our study shows that the maternal genetic component affects preweaning calf mortality twice as much (or more) as the direct genetic component. A large number of offspring per sire is necessary in progeny tests to genetically decrease calf mortality.  相似文献   

6.
The de Wildt Cheetah and Wildlife Centre was established in 1971 and the first cheetah cubs were born in 1975. During the period 1975–2005, 242 litters were born with a total of 785 cubs. Mean cub survival from 1 to 12 months and greater than 12 months of age was 71.3 and 66.2%, respectively. The majority of losses (84.9%) occurred during the first month postpartum whereas only 15.1% deaths took place between 1 and 12 months of age. Females were first bred at an age of approximately 3 years, reached maximum reproductive age at 6–8 years, where after fertility declined. Males reached peak reproduction at 6 and maintained this for up to 12 years of age. Male fertility was best correlated with sperm morphology. During recent years, for practical purposes, males were allocated to 'good' (≥70% normal), 'fair' (40–70% normal) and 'poor' (<40% normal) categories according to sperm morphology count. The breeding males were selected from the good (preferably) and fair categories but poor category males were also used at times. Average litter sizes for 'good', 'fair' and 'poor' males were 3.44 (n = 21), 3.14 (n = 18) and 2.28 (n = 18), respectively. In females the heritability for litter size was high at 0.5848 (532 progeny, 1975–2007) and the maternal heritability for cub mortality was estimated to be 0.596. The data from the de Wildt Cheetah and Wildlife Centre and two other centres in the world (Kapama and Wassenaar) demonstrate that cheetah can be bred successfully in captivity.  相似文献   

7.
Age at first calving (AFC) measures the entry of heifers into the beef cattle production system. This trait can be used as a selection criterion for earlier reproductive performance. Using data from Nelore cattle participating in the 'Program for Genetic Improvement of the Nelore Breed' (PMGRN-Nelore Brazil), bi-trait analyses were performed using the restricted maximum likelihood method, based on an AFC animal model and the following traits: female body weight adjusted to 365 (BW365) and 450 (BW450) days of age, and male scrotal circumference adjusted to 365 (SC365), 450 (SC450), 550 (SC550) and 730 (SC730) days of age. The heritability estimates for AFC ranged from 0.02 ± 0.02 to 0.04 ± 0.02. The estimates of additive direct heritabilities (with standard error) for BW365, BW450, SC365, SC450, SC550 and SC730 were 0.36 ± 0.07, 0.38 ± 0.07, 0.48 ± 0.07, 0.65 ± 0.07, 0.64 ± 0.07 and 0.42 ± 0.07, respectively, and the genetic correlations with AFC were −0.38, −0.33, 0.10, −0.13, −0.13 and 0.06, respectively. In the herds studied, selection for SC365, SC450, SC550 or SC730 should not cause genetic changes in AFC. Selection based on BW365 or BW450 would favor smaller AFC breeding values. However, the low magnitude of direct heritability estimates for AFC in these farms indicates that changes in phenotypical expression depend mostly on non-genetic factors.  相似文献   

8.
Records for Afshari sheep were retrieved from data collected between 2000 and 2005 at the Zanjan University experimental flock, at Zanjan, Iran. (Co)variance components and corresponding genetic parameters for birth weight (BW), weaning weight (WW), 6-month weight (W6), average daily gain from birth to weaning (ADGa), from birth to 6 months (ADGb), from weaning to 6 months (ADGc), Kleiber ratio at weaning (WWKR) and Kleiber ratio at 6 months of age (W6KR) were estimated using univariate and bivariate analyses by the DFREML procedure. The Kleiber ratio, defined as growth rate/metabolic weight, has been suggested to be a useful indicator of growth efficiency and an indirect selection criterion for feed conversion. Estimates of direct heritability ( h 2) were 0.23, 0.27, 0.11, 0.22, 0.07, 0.01, 0.13 and 0.06 for BW, WW, W6, ADGa, ADGb, ADGc, WWKR and W6KR, respectively. Maternal genetic effects represented a relatively large proportion of the total phenotypic variance for BW ( m 2 = 0.22), whereas maternal permanent environmental effects were significant for W6 ( c 2 = 0.15), ADGb ( c 2 = 0.16), ADGc ( c 2 = 0.14) and W6KR ( c 2 = 0.16). Results of bivariate analyses indicated the variable genetic correlations between traits. The largest positive genetic relationships were between adjacent measurements. The moderate estimates of h 2 for early growth traits indicate that in Afshari sheep faster genetic improvement through selection is possible for these traits. In order to increase the efficiency of feed conversion, use of Kleiber ratio in selection programmes was recommended.  相似文献   

9.
A total of 11,815 weight records from 23,94 Japanese Black calves was used to estimate direct, maternal, direct permanent environmental, and maternal permanent environmental effects on growth from birth to 356 d of age. The data were collected from a herd of Japanese Black cattle in Shiroshi city, Miyagi prefecture, Japan. A random regression model, including parity of dam and year-season of calving-sex of calf as fixed effects and animal, dam, animal permanent environmental, and maternal permanent environmental as random effects, was fitted to the data using Legendre polynomials for age of calf. Direct heritability estimates increased from 0.38 at birth to 0.65 at 120 d of age, decreased to 0.38 at 300 d, and then increased again up to 0.47 at 356 d. The ratio of animal permanent environmental variance to phenotypic variance decreased from 0.41 at birth to 0.12 at 90 d, and then increased gradually up to 0.40 at 270 d and oscillated around this value up to the end of the test period. Maternal genetic heritabilities increased from 0.04 at birth to 0.09 at 120 d and then decreased to 0.06 thereafter, whereas the variance ratios due to maternal permanent environment were fairly constant across the age trajectory, fluctuating around the value of 0.03. Direct genetic, phenotypic, maternal genetic, animal permanent environmental, and maternal permanent environmental correlations between different ages were all positive, and they generally decreased as the interval between ages increased. These correlations were lower between weights from nonadjacent ages than those between weights from adjacent ages. Results suggest that selection on preweaning weights would have a positive effect on weights at later ages.  相似文献   

10.
To estimate adjustment factors and genetic parameters for gestation length (GES), AI and calving date records (n = 40,356) were extracted from the Canadian Charolais Association field database. The average time from AI to calving date was 285.2 d (SD = 4.49 d) and ranged from 274 to 296 d. Fixed effects were sex of calf, age of dam (2, 3, 4, 5 to 10, > or = 11 yr), and gestation contemporary group (year of birth x herd of origin). Variance components were estimated using REML and 4 animal models (n = 84,332) containing from 0 to 3 random maternal effects. Model 1 (M1) contained only direct genetic effects. Model 2 (M2) was G1 plus maternal genetic effects with the direct x maternal genetic covariance constrained to zero, and model 3 (M3) was G2 without the covariance constraint. Model 4 (M4) extended G3 to include a random maternal permanent environmental effect. Direct heritability estimates were high and similar among all models (0.61 to 0.64), and maternal heritability estimates were low, ranging from 0.01 (M2) to 0.09 (M3). Likelihood ratio tests and parameter estimates suggested that M4 was the most appropriate (P < 0.05) model. With M4, phenotypic variance (18.35 d2) was partitioned into direct and maternal genetic, and maternal permanent environmental components (hd2 = 0.64 +/- 0.04, hm2 = 0.07 +/- 0.01, r(d,m) = -0.37 +/- 0.06, and c2 = 0.03 +/- 0.01, respectively). Linear contrasts were used to estimate that bull calves gestated 1.26 d longer (P < 0.02) than heifers, and adjustments to a mature equivalent (5 to 10 yr old) age of dam were 1.49 (P < 0.01), 0.56 (P < 0.01), 0.33 (P < 0.01), and -0.24 (P < 0.14) d for GES records of calves born to 2-, 3-, 4-, and > or = 11-yr-old cows, respectively. Bivariate animal models were used to estimate genetic parameters for GES with birth and adjusted 205-d weaning weights, and postweaning gain. Direct GES was positively correlated with direct birth weight (BWT; 0.34 +/- 0.04) but negatively correlated with maternal BWT (-0.20 +/- 0.07). Maternal GES had a low, negative genetic correlation with direct BWT (-0.15 +/- 0.05) but a high and positive genetic correlation with maternal BWT (0.62 +/- 0.07). Generally, GES had near-zero genetic correlations with direct and maternal weaning weights. Results suggest that important genetic associations exist for GES with BWT, but genetic correlations with weaning weight and postweaning gain were less important.  相似文献   

11.
Direct and maternal (co)variance components and genetic parameters were estimated for growth and reproductive traits in the Kenya Boran cattle fitting univariate animal models. Data consisted of records on 4502 animals from 81 sires and 1010 dams collected between 1989 and 2004. The average number of progeny per sire was 56. Direct heritability estimates for growth traits were 0.34, 0.12, 0.19, 0.08 and 0.14 for birth weight (BW), weaning weight (WW), 12-month weight (12W), 18-month weight (18W) and 24-month weight (24W), respectively. Maternal heritability increased from 0.14 at weaning to 0.34 at 12 months of age but reduced to 0.11 at 24 months of age. The maternal permanent environmental effect contributed 16%, 4% and 10% of the total phenotypic variance for WW, 12W and 18W, respectively. Direct-maternal genetic correlations were negative ranging from −0.14 to −0.58. The heritability estimates for reproductive traits were 0.04, 0.00, 0.15, 0.00 and 0.00 for age at first calving (AFC), calving interval in the first, second, and third parity, and pooled calving interval. Selection for growth traits should be practiced with caution since this may lead to a reduction in reproduction efficiency, and direct selection for reproductive traits may be hampered by their low heritability.  相似文献   

12.
Mortality records of 8,642 lambs from a composite population at the U.S. Meat Animal Research Center during the first year of life were studied using discrete survival analyses. Lamb mortality was studied across periods from birth to weaning, birth to 365 d of age, and weaning to 365 d of age. Animal-time data sets were created for each period using different time intervals: daily, weekly, fortnightly, and monthly. Each data set was analyzed using logistic and complementary log-log sire, animal, and maternal effects models. Explanatory variables included in the models were duration of time interval, sex, type of birth, contemporary group, age of dam, and type of upbringing (nursery or not). Similar estimates of explanatory variables were obtained within the same period across models and different time intervals. Heritability estimates from the complementary log-log models were greater than those from the comparable logistic models because of the difference in variance of the respective link functions. Heritability estimates from the complementary log-log sire model ranged from 0.13 to 0.21 for all periods. These estimates were greater than the complementary log-log animal model estimates that ranged from 0.04 to 0.12. Maternal effects were important early in life, with the maternal heritability slightly greater than the direct additive heritability. Negative correlations (-0.72 to -0.65) between direct additive and maternal effects was estimated. The similarity of results among survival analysis methods demonstrates that the discrete methodology is a viable alternative to estimate variance components in livestock survival data.  相似文献   

13.
Records for yearling scrotal circumference (SC; n = 7,580), age at puberty in heifers (AP; n = 5,292), age at first calving (AFC; n = 4,835), and pregnancy, calving, or weaning status following the first breeding season (PR1, CR1, or WR1, respectively; n = 7,003) from 12 Bos taurus breeds collected at the Meat Animal Research Center (USDA) between 1978 and 1991 were used to estimate genetic parameters. Age at puberty (AP) was defined as age in days at first detected ovulatory estrus. Pregnancy (calving or weaning) status was scored as one for females conceiving (calving or weaning) given exposure during the breeding season and as zero otherwise. The final model for SC included fixed effects of age of dam at breeding (AD), year of breeding (Y), and breed (B) and age in days at measurement as a covariate. Fixed effects in models for AP and AFC were AD, Y, B, and month of birth. Fixed effects in models for PR1, CR1, and WR1 included AD, Y, and B. For all traits, random effects in the model were direct genetic, maternal genetic, maternal permanent environmental, and residual. Analyses for a three-trait animal model were carried out with SC, AP, and a third trait (the third trait was AFC, PR1, CR1, or WR1). A derivative-free restricted maximum likelihood algorithm was used to estimate the (co)variance components. Direct and maternal heritability estimates were 0.41 and 0.05 for SC; 0.16 and 0.03 for AP; 0.08 and 0.00 for AFC; 0.14 and 0.02 for PR1; 0.14 and 0.03 for CR1; and 0.12 and 0.01 for WR1. Genetic correlations between direct and maternal genetic effects within trait were -0.26, -0.63, -0.91, -0.79, -0.66, and -0.85 for SC, AP, AFC, PR1, CR1, and WR1, respectively. Direct genetic correlations between SC and AP and between those traits and AFC, PR1, CR1, and WR1 ranged from -0.15 (between SC and AP) to 0.23 (between AP and WR1). Estimates of heritability indicate that yearling SC should respond to direct selection better than AP, AFC, PR1, CR1, and WR1. Variation due to maternal genetic effects was small for all traits. No strong genetic correlations were detected between SC and female reproductive traits or between AP and the other female traits. These results suggest that genetic response in female reproductive traits through sire selection on yearling SC is not expected to be effective.  相似文献   

14.
This study examined the viability of 4,554 D’man lambs born alive at Errachidia research station in south-eastern Morocco between 1988 and 2009. Lamb survival to 1, 10, 30 and 90 days old was 0.95, 0.93, 0.93 and 0.92, respectively. The majority of deaths (85.7 %) occurred before 10 days of age. Type and period of birth both had a significant effect on lamb survival traits, whereas age of dam and sex of lamb did not. The study revealed a curvilinear relationship between lamb’s birth weight and survival traits from birth to 90 days, with optimal birth weights for maximal perinatal and preweaning survival varying according to type of birth from 2.6 to 3.5 kg. Estimation of variance components, using an animal model including direct and maternal genetic effects, the permanent maternal environment as well as fixed effects, showed that direct and maternal heritability estimates for survival traits between birth and 90 days were mostly low and varied from 0.01 to 0.10; however, direct heritability for survival at 1 day from birth was estimated at 0.63. Genetic correlations between survival traits and birth weight were positive and low to moderate. It was concluded that survival traits of D’man lambs between birth and 90 days could be improved through selection, but genetic progress would be low. However, the high proportion of the residual variance to total variance reinforces the need to improve management and lambing conditions.  相似文献   

15.
Variance components, heritability (direct additive and maternal) and correlations (additive genetic, phenotypic, maternal genetic and environmental) of body weight (BW) and body size including length (BL), height (BH) and chest girth (BCG) at birth in Boer goats were estimated on the basis of 5096 records obtained from a Boer Goat Breeding Station in Yidu, China, during 2001–2005. The parameters were estimated using a DFREML procedure by excluding or including maternal genetic or permanent maternal environmental effects, four different analysis models were fitted in order to determine the optimum model for each trait. The environmental factors such as year, season, sex and litter size (LS, number of kids) were investigated as the fixed effects. The results showed that the maternal effects were important determinants of estimated the genetic parameters for birth traits. Year and season had significant effect on birth traits. Single births and male kids had the heaviest live weight and the largest body size at birth. The mean values and standard deviation (SD) of BW, BL, BH and BCG were 3.87 ± 0.85 kg, 31.67 ± 2.87 cm, 32.92 ± 2.80 cm, 33.46 ± 3.21 cm. The mean values and standard error (SE) of direct additive heritability estimates for BW, BL, BH and BCG calculated with the optimum model were 0.19 ± 0.08, 0.14 ± 0.07, 0.24 ± 0.09 and 0.25 ± 0.10, respectively. For all the birth traits, estimates of the correlations between direct additive and maternal genetic (ra–m) were negative. The estimates of additive genetic and phenotypic correlations among the birth traits were high and positive, and implied no genetic antagonisms among these traits analyzed. The estimates of maternal genetic correlations also were high and positive. Medium and positive environmental correlations indicated the important effects of environmental factors on early growth traits.  相似文献   

16.
Survival analysis of lamb mortality in a terminal sire composite population   总被引：1，自引：0，他引：1  
Records of mortality during the first year of life of 8,642 lambs from a composite population at the U.S. Meat Animal Research Center were studied using survival and logistic analyses. The traditional logistic approach analyzes the binary response of whether or not a lamb survived until a particular time point, thus disregarding information on the actual age at death. Survival analysis offers an alternative way to study mortality, wherein the response variable studied is the precise age at death while accounting for possible record censoring. Lamb mortality was studied across five periods based on management practices: birth to weaning, birth to 120 d of age, birth to 365 d of age, weaning to 365 d of age, and 120 to 365 d of age. Explanatory variables included in the models were sex, type of birth, age of dam, and whether or not a lamb was raised in a nursery. The survival analysis was implemented using Weibull and Cox proportional hazards models with sire as random effect. The logistic approach evaluated sire, animal, and maternal effects models. Lambs culled during any period were treated as censored in the survival analyses and were assumed alive in the logistic analyses. Similar estimates of the explanatory variables were obtained from the survival and logistic analyses, but the survival analyses had lower standard errors than the logistic analyses, suggesting a slight superiority of the former approach. Heritability estimates were generally consistent across all periods ranging from 0.15 to 0.21 in the Weibull model, 0.12 to 0.20 in the Cox model, 0.08 to 0.11 in the logistic sire model, 0.04 to 0.05 in the logistic animal model, and 0.03 to 0.07 in the maternal effects logistic model. Maternal effects were important in the early stages of lamb life, but the maternal heritability was less than 0.07 in all the stages studied with a negative correlation (-0.86 to -0.61) between direct and maternal effects. The estimates of additive genetic variance indicate that the use of survival analysis estimates in breeding schemes could allow for effective selection against mortality, thereby improving sheep productivity, welfare, and profitability.  相似文献   

17.
The purpose of this study was to compare estimates of genetic parameters for sequential growth of beef cattle using two models and two data sets. Growth curves of Nellore cattle were analyzed using body weights measured at ages 1 (birth weight) to 733 d. Two data samples were created, one with 71,867 records sampled from all herds (MISS), and the other with 74,601 records sampled from herds with no missing traits (NMISS). Records preadjusted to a fixed age were analyzed by a multiple-trait model (MTM), which included the effects of contemporary group, age of dam class, additive direct, additive maternal, and maternal permanent environment. Analyses were by REML, with five traits at a time. The random regression model (RRM) included the effects of age of animal, contemporary group, age of dam class, additive direct, additive maternal, permanent environment, and maternal permanent environment. All effects were modeled as cubic Legendre polynomials. These analyses were also by REML. Shapes of estimates of variances by MTM were mostly similar for both data sets for all except late ages, where estimates for MISS were less regular, and for birth weight with MISS. Genetic correlations among ages for the direct and maternal effects were less smooth with MISS. Genetic correlations between direct and maternal effects were more negative for NMISS, where few sires were maternal grandsires. Parameter estimates with RRM were similar to MTM cept that estimates of variances showed more artifacts for MISS; the estimates of additive direct-maternal correlations were more negative with both data sets and approached -1.0 for some ages with NMISS. When parameters of a growth model obtained by used for genetic evaluation, these parameters should be examined for consistency with parameters from MTM and prior information, and adjustments may be required to eliminate artifacts.  相似文献   

18.
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   

19.
The heritability of hip dysplasia in the German Shepherd Dog was estimated by applying the animal model and the Restricted Maximum Likelihood (REML) method to a data-set which consisted of the hip scores of 10 335 dogs. Fixed effects of the model were the month and the year of birth, screening age, the panelist responsible for screening and the origin of the animal's sire. The litter and the breeder had only minor effects on hip joints. Heritability estimates were moderate (0.31–0.35). The moderate heritability, which was found in this study, enables a much better genetic gain in the breeding programme, if proper evaluation methods, such as BLUP animal model, and effective selection is used instead of phenotypic selection.  相似文献   

20.
A 300 cow Brahman herd kept on improved pasture was subjected to a selection and management programme based on a limited breeding season. Artificial insemination using mainly progeny tested bulls was used in part of the herd and the rest were bred in single sire herds. Of the 200 sires used during the 30 year period, 82% were homebred and selected principally for high estimated breeding value of 18-month weight. Variance components of birth (BW), weaning (205 W) and 18-month (548 W) weights of 6130 calves born 1968 through to 1997 were estimated by the Restricted Maximum Likelihood method (REML) using uni- and bivariate animal models. For each weight the animal's direct and maternal genetic and the dam's permanent environmental effects were considered random and those of sex, year and month of birth and age of cow were considered fixed, but the models differed as far as the number of significant interactions included. Adjusted least squares means for BW, 205 W and 548 W were 28, 158 and 292 kg. Phenotypic and direct and maternal genetic trends from univariate analysis were for BW: 0.156, 0.061 and −0.001 kg; for 205 W: 0.471, 0.126 and 0.044 kg; for 548 W: 1.973, 0.486 and 0.251 kg per year. Direct and maternal heritabilities from univariate analyses were for BW, 205 W and 548 W, 0.33 and 0.08; 0.07 and 0.14; 0.13 and 0.08, respectively. Genetic direct-maternal correlations for the three weights were −0.37, −0.13 and 0.49 and permanent environmental variance of the dam as proportion of phenotypic variance (c2) had values of 0.03, 0.16 and 0.01, respectively. Direct and maternal genetic correlations were for BW: 205 W, 0.64 and 0.74; for BW: 548 W, 0.35 and 0.74; and for 205 W: 548 W, 0.64 and 0.96. Future genetic work in the herd should put more emphasis on the improvement of cow efficiency for sustainable beef production on native and improved pasture.  相似文献   

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