Maternal Heritability Research Articles

Genetic and phenotypic aspects of growth rate and efficiency-related traits in sheep

A large set of Baluchi sheep growth data collected at Abbasabad Sheep Breeding Station, Mashhad, Khorasan Razavi, Iran, was used to estimate phenotypic and genetic parameters for growth rate from birth to weaning (GRa), weaning to six months of age (GRb), and weaning to 12 months of age (GRc) and corresponding Kleiber ratios (KRa, KRb, KRc), efficiency of growth (EFa, EFb, EFc) and relative growth rate (RGRa, RGRb, RGRc). Genetic parameters were estimated by REML procedure fitting a series of six univariate animal models including various combinations of maternal effects. The most appropriate model for each trait was determined by the Akaike Information Criterion (AIC). In addition, a multi-variate analysis was done to estimate (co)variance components between traits. Estimates of direct heritabilities (h2) were, respectively, 0.06, 0.03 and 0.10 for GRa, GRb, and GRc; 0.06, 0.06, and 0.05 for EFa, EFb and EFc; 0.07, 0.04 and 0.06 for KRa, KRb and KRc; and 0.07, 0.05 and 0.05 for RGRa, RGRb and RGRc. For traits measured in the pre-weaning growth phase, maternal genetic effect was significant. The estimates of maternal heritability (m2) for GRa, KRa, EFa and RGRa were 0.11, 0.11, 0.04 and 0.04, respectively. Estimates of the additive genetic coefficients of variation (CVA) were used as a measure of genetic variability and ranged between 1.68% (RGRa) and 14.67% (EFb). Genetic correlations between traits ranged from −0.81 (EFa-KRc) to 0.94 (ADGa-KRa) and phenotypic correlations ranged from −0.72 (KRa-EFc) to 0.99 (GRb-RGRb). Overall, results showed little additive genetic variation in growth rate or efficiency-related traits of Baluchi sheep, indicating little opportunity for genetic improvement of these traits in this breed through selection. In addition, significant maternal effects on traits related to pre-weaning growth indicated the importance of including maternal effects in genetic evaluation of traits measured early in life.

Estimation of Genetic Parameters for Some Production and Reproduction Traits Using Different Animal Models in Egyptian Buffaloes

Estimates of (co)variance component and genetic parameters using multi-traits animal model, traits studied were lactation period (LP), total lactation milk yield (TMY), and days open (DO). In all lactations based on 4745 records of Egyptian buffaloes calved during the period from 1980 to 2014 at Mehallet Mousa Experimental farms of Animal Production Research Institute (APRI), Ministry of Agriculture. The six mixed model used in the analysis included the non genetic effects of month and year of calving, parity, and the random effects of additive direct genetics, maternal effect, maternal permanent environmental and residual. Means for LP, TMY and Do were 220.632 d, 1445.26 kg and 184.34 d, respectively. The estimates of heritability in six models for LP, TMY and Do were ranged from (0.026±0.56 to 0.047±0.16), (0.15±0.57 to 0.021±0.15) and (0.02±0.020 to 0.020±0.13), respectively. While Estimates of maternal heritability was very low in six models for LP, TMY and DO and ranged from 0.055±0.026 to 0.18E-09±0.79E-05: 0.081±0.029 to 0.52E-09±0.13E-04; 0.053±0.01 to 0.83E-09±0.12E-04, respectively. The estimates of genetic correlations between LP and TMY in six models ranged from (0.53 to 0.84). Estimates of genetic correlation between DO and TMY in six models ranged from (-0.15 to 0.58).While the estimates of genetic correlation between LP and DO in six models ranged from (0.30 to 0.94). Corresponding estimates of phenotypic correlation among same traits fluctuated (0.17 to76). Thus, the influence of the maternal genetic effect for traits studied was lowest thereby no relative efficiency of improvement. Vice-versa, direct heritabilities for TMY and LP were efficiency, therefore considerable rate of genetic improvement these traits under investigation. Genetic betterment for LP following up improve each TMY and DO. The estimates of heritabilities were low for DO indicated that the major part of the variation in this trait was environmental and selection may not prove effective in bringing about genetic improvement. Therefore, preferable improving management can play a major role in this trait.

Bayesian inference of genetic parameters for ultrasound scanning traits of Kivircik lambs

Ultrasound scanning traits have been adapted in selection programs in many countries to improve carcass traits for lean meat production. As the genetic parameters of the traits interested are important for breeding programs, the estimation of these parameters was aimed at the present investigation. The estimated parameters were direct and maternal heritability as well as genetic correlations between the studied traits. The traits were backfat thickness (BFT), skin+backfat thickness (SBFT), eye muscle depth (MD) and live weights at the day of scanning (LW). The breed investigated was Kivircik, which has a high quality of meat. Six different multi-trait animal models were fitted to determine the most suitable model for the data using Bayesian approach. Based on deviance information criterion, a model that includes direct additive genetic effects, maternal additive genetic effects, direct maternal genetic covariance and maternal permanent environmental effects revealed to be the most appropriate for the data, and therefore, inferences were built on the results of that model. The direct heritability estimates for BFT, SBFT, MD and LW were 0.26, 0.26, 0.23 and 0.09, whereas the maternal heritability estimates were 0.27, 0.27, 0.24 and 0.20, respectively. Negative genetic correlations were obtained between direct and maternal effects for BFT, SBFT and MD. Both direct and maternal genetic correlations between traits were favorable, whereas BFT–MD and SBFT–MD had negligible direct genetic correlation. The highest direct and maternal genetic correlations were between BFT and SBFT (0.39) and between MD and LW (0.48), respectively. Our results, in general, indicated that maternal effects should be accounted for in estimation of genetic parameters of ultrasound scanning traits in Kivircik lambs, and SBFT can be used as a selection criterion to improve BFT.

Genetic parameters estimation for preweaning traits and their relationship with reproductive, productive and morphological traits in alpaca

The aim of this study was to estimate the genetic parameters for preweaning traits and their relationship with reproductive, productive and morphological traits in alpacas. The data were collected from 2001 to 2015 in the Pacomarca experimental farm. The data set contained data from 4330 females and 3788 males corresponding to 6396 and 1722 animals for Huacaya and Suri variants, respectively. The number of records for Huacaya and Suri variants were 5494 and 1461 for birth weight (BW), 5429 and 1431 for birth withers height (BH), 3320 and 896 for both weaning weight (WW) and average daily gain (DG) from birth to weaning, 3317 and 896 for weaning withers height (WH), and 5514 and 1474 for survival to weaning. The reproductive traits analyzed were age at first calving and calving interval. The fiber traits were fiber diameter (FD), standard deviation of FD (SD), comfort factor and coefficient of variation of FD and the morphological traits studied were density, crimp in Huacaya and lock structure in Suri, head, coverage and balance. Regarding preweaning traits, model of analysis included additive, maternal and residual random effects for all traits, with sex, coat color, number of calving, month–year and contemporary group as systematic effects, and age at weaning as linear covariate for WW and WH. The most relevant direct heritabilities for Huacaya and Suri were 0.50 and 0.34 for WW, 0.36 and 0.66 for WH, 0.45 and 0.20 for DG, respectively. Maternal heritabilities were 0.25 and 0.38 for BW, 0.18 and 0.32 for BH, 0.29 and 0.39 for WW, 0.19 and 0.26 for WH, 0.27 and 0.36 for DG, respectively. Direct genetic correlations within preweaning traits were high and favorable and lower between direct and maternal genetic effects. The genetic correlations of preweaning traits with fiber traits were moderate and unfavorable. With morphological traits they were high and positive for Suri but not for Huacaya and favorable for direct genetic effect but unfavorable for maternal genetic effect with reproductive traits. If the selection objective was meat production, the selection would have to be based on the direct genetic effect for WW but not on the maternal genetic effect that has been shown to have less relevance. Other weaning traits such as WH or DG would be indirectly selected.

Genetic parameters for lameness, mastitis and dagginess in a multi-breed sheep population

The objective of the present study was to quantify the extent of genetic variation in three health-related traits namely dagginess, lameness and mastitis, in an Irish sheep population. Each of the health traits investigated pose substantial welfare implications as well as considerable economic costs to producers. Data were also available on four body-related traits, namely body condition score (BCS), live weight, muscle depth and fat depth. Animals were categorised as lambs (<365 days old) or ewes (⩾365 days old) and were analysed both separately and combined. After edits, 39 315 records from 264 flocks between the years 2009 and 2015 inclusive were analysed. Variance components were estimated using animal linear mixed models. Fixed effects included contemporary group, represented as a three-way interaction between flock, date of inspection and animal type (i.e. lamb, yearling ewe (i.e. females ⩾365 days but <730 days old that have not yet had a recorded lambing) or ewe), animal breed proportion, coefficients of heterosis and recombination, animal gender (lambs only), animal parity (ewes only; lambs were assigned a separate ‘parity’) and the difference in age of the animal from the median of the respective parity/age group. An additive genetic effect and residual effect were both fitted as random terms with maternal genetic and non-genetic components also considered for traits of the lambs. The direct heritability of dagginess was similar across age groups (0.14 to 0.15), whereas the direct heritability of lameness ranged from 0.06 (ewes) to 0.12 (lambs). The direct heritability of mastitis was 0.04. For dagginess, 13% of the phenotypic variation was explained by dam litter, whereas the maternal heritability of dagginess was 0.05. The genetic correlation between ewe and lamb dagginess was 0.38; the correlation between ewe and lamb lameness was close to zero but was associated with a large standard error. Direct genetic correlations were evident between dagginess and BCS in ewes and between lameness and BCS in lambs. The present study has demonstrated that ample genetic variation exists for all three health traits investigated indicating that genetic improvement is indeed possible.

Bayesian analyses of genetic parameters for growth traits in Nellore cattle raised on pasture.

This study was carried out to investigate (co)variance components and genetic parameters for growth traits in beef cattle using a multi-trait model by Bayesian methods. Genetic and residual (co)variances and parameters were estimated for weights at standard ages of 120 (W120), 210 (W210), 365 (W365), and 450 days (W450), and for pre- and post-weaning daily weight gain (preWWG and postWWG) in Nellore cattle. Data were collected over 16 years (1993-2009), and all animals were raised on pasture in eight farms in the North of Brazil that participate in the National Association of Breeders and Researchers. Analyses were run by the Bayesian approach using Gibbs sampler. Additive direct heritabilities for W120, W210, W365, and W450 and for preWWG and postWWG were 0.28 ± 0.013, 0.32 ± 0.002, 0.31 ± 0.002, 0.50 ± 0.026, 0.61 ± 0.047, and 0.79 ± 0.055, respectively. The estimates of maternal heritability were 0.32 ± 0.012, 0.29 ± 0.004, 0.30 ± 0.005, 0.25 ± 0.015, 0.23 ± 0.017, and 0.22 ± 0.016, respectively, for W120, W210, W365, and W450 and for preWWG and postWWG. The estimates of genetic direct additive correlation among all traits were positive and ranged from 0.25 ± 0.03 (preWWG and postWWG) to 0.99 ± 0.00 (W210 and preWWG). The moderate to high estimates of heritability and genetic correlation for weights and daily weight gains at different ages is suggestive of genetic improvement in these traits by selection at an appropriate age. Maternal genetic effects seemed to be significant across the traits. When the focus is on direct and maternal effects, W210 seems to be a good criterium for the selection of Nellore cattle considering the importance of this breed as a major breed of beef cattle not only in Northern Brazil but all regions covered by tropical pastures. As in this study the genetic correlations among all traits were high, the selection based on weaning weight might be a good choice because at this age there are two important effects (maternal and direct genetic effects). In contrast, W120 should be preferred when the objective is improving the maternal ability of the dams. Furthermore, selection for postWWG can be used if the animals show both heavier weaning weights and high growth rate after weaning because it is possible to shorten the time between weaning and slaughter based on weaning weight, postWWG, and desired weight at the time of slaughter.

COMPARING GENETIC PARAMETERS OF FRIESIAN MILK PRODUCTION TRAITS IN COMMERCIAL AND STATE FARMS IN EGYPT

This study was conducted to estimate the genetic parameters for milk production traits of Friesian cattle in two selected dairy farms located in the Nile Delta of Egypt. A total of 1438 lactation records during the years2001 to 2009 were collected to represent 472 cows in Sakha Governmentfarm (SF). In comparison, a total of 1660 lactation records during the years 1998 to 2005 were collected to represent 465 cows in Gharbawy commercial (GF) farm. The derivative-free restricted maximum likelihood (REML) procedure was used to determine heritability, genetic correlation and breeding value of the studied traits. The results indicated that non genetic factors affecting lactation period (LP), total milk yield (TMY) and 305d -milk yield (305 d-MY) had highly significant (p < 0.001) effect on those traits except the effect of season of calving on TMY. Interaction between (herd & parity) and the interaction between (herd & parity & season) had highly significant effect (P< 0.001) on all milk production traits. The overall means of LP, TMY and 305-dMY were 313day; 4140kg; 3630 kg, respectively for cows in SF and as the corresponding values in GFwere 369.5day,8820Kg and 7430 kg. Estimates of direct heritability for LP, TMY, and 305MY in SF were 0.10, 0.11and 0.19 respectively, the corresponding estimates for GF were 0.10, 0.13 and 0.07 respectively on the other hand, estimates of maternal heritability for LP,TMY and 305MY in SF were 0.04, 0.07 and 0.06, respectively, while , the estimate in GF were 0.08, 0.09 and 0.12, respectively. The breeding values of sires estimated for LP,TMY and 305d-MY were 50.4, 27.4 and 42.3, respectively in SF, while the same estimates in GF were150.1, 20.04,and 30.7. The breeding values of cow concerning LP, TMY and 305MY in SF were 63.32, 45,4 and 21.5 while in GF, values were 195.1 , 29.9 , 53.2 , respectively . It can be concluded that improving environmental conditions and management practices, coupled with improved genetic potential of dairy animals in the state or commercial farms would be more effective approaches for high milk productivity.

Estimates of genetic parameters and genetic trends for pre-weaning growth traits in Sardi sheep

The aim of the present study was to estimate (co)variance components for weights at birth (BW), 30days (W30d) and 90days (W90d) of age, as well as average daily gain from birth to 30days (ADG1) and from 30 to 90days (ADG2) of Sardi sheep. Records of 3709 lambs that descended from 1170 dams and 85 sires were collected over a period of 21 years in the Kra Kra sheep farm. (Co) variance components and the corresponding genetic parameters were estimated under Restricted Maximum Likelihood (REML) method by fitting of six different animal models with ignoring or including maternal effects including maternal genetic or maternal permanent environmental effects. The best model was chosen based on Akaike’s Information Criterion (AIC). Bivariate analysis was performed using the most appropriate models obtained in univariate analysis. Age of dam, type of birth, sex of lamb and year of birth showed significant effects on studied traits, so they were considered as fixed effects in analyzing models. Direct heritability estimates for BW, W30d, W90d, ADG1 and ADG2 were 0.07±0.02, 0.09±0.03, 0.05±0.02, 0.01±0.01 and 0.05±0.02, respectively. Maternal heritability estimates were 0.13±0.03 and 0.21±0.04 for BW and W30d, respectively. These results indicate that maternal effects on BW and W30d of Sardi lambs need to be considered in any selection programme undertaken in this breed. Maternal permanent environmental effects accounted for 11%, 8% and 8% of phenotypic variance for W90d, ADG1 and ADG2, respectively. The direct genetic correlations between studied traits were positive in all cases and ranged from 0.23 for BW-ADG1 to 0.98 for W90d-ADG2. The corresponding phenotypic correlations varied from −0.01 for BW-ADG1 to 0.92 for W30d- ADG1. The maternal additive genetic correlation between BW and W30d was 0.66. Also, the environmental correlations among studied traits varied from −0.04 for BW-ADG1 to 0.93 for W30d-ADG1. Annual genetic gains for direct and maternal additive genetic effects of studied traits were close to zero. Thus to realize a genetic progress, selection should be based on additive genetic values instead of phenotypic characteristics.

Genetic parameter estimates for prenatal and postnatal mortality in Nellore cattle.

The aim of this study was to estimate genetic parameters for prenatal (PRE) and postnatal (POS) mortality in Nellore cattle. A total of 13141 (PRE) and 17818 (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.

Bayesian estimates of genetic relationship between calving difficulty and productive and reproductive performance in Holstein cows

The objective of present study was to estimate genetic correlations between calving difficulty and productive and reproductive traits in Iranian Holsteins. Calving records from the Animal Breeding Center of Iran, collected from 1991 to 2011 and comprising 183 203 first-calving events of Holstein cows from 1470 herds were included in the dataset. Threshold animal models included direct genetic effect (Model 1) or direct and maternal genetic effects with covariance between them (Model 2) were fitted for the genetic analysis of calving difficulty. Also, linear animal models including direct genetic effect were fitted for the genetic analysis of productive and reproductive performance traits. A set of linear-threshold bivariate models was used for obtaining genetic correlation between calving difficulty and other traits. All analyses were implemented by Bayesian approach via Gibbs sampling methodology. A single Gibbs sampling chain with 300 000 rounds was generated by the TM program. Posterior mean estimates of direct heritabilities for calving difficulty were 0.056 and 0.066, obtained from different models. Also, posterior mean estimate of maternal heritability for this trait was 0.018. Estimate of correlation between direct and maternal genetic effects for calving difficulty was negative (–0.44). Posterior mean estimates of direct heritabilities for milk yield, fat yield, protein yield, days from calving to first service, days open and first calving interval were 0.257, 0.188, 0.235, 0.034, 0.042 and 0.050 respectively. The posterior means of direct genetic correlation between calving difficulty and milk yield, fat yield, protein yield, days from calving to first service, days open and first calving interval were low and equal to –0.135, 0.030, –0.067, –0.010, –0.075 and –0.074 respectively. The results of the current study indicated that exploitable genetic variation in calving difficulty, productive and reproductive traits could be applied in designing future genetic selection plans for Iranian Holsteins.

Combination of B-Spline and Legendre functions in random regression models to fit growth curve of Moghani sheep

Random regression models (RRMs) were employed to estimate variance components for body weight (BW) records of Moghani sheep from 60 to 365days of age. A total of 9165 BW records of 2811 lambs, collected at a breeding station of Moghani sheep were used in this study. Various combinations of Legendre (Leg) polynomials with 2 and 3 orders of fit and linear and quadratic B-Splines (BS) with 2 or 3 coefficients were fitted for fixed and random regression parts of the RRMs. The models were compared based on Akaike’s and Bayesian Information Criteria. Different combinations of Leg and BS functions had almost similar estimates of variance components as ratios to total phenotypic variance, but the models with Leg polynomials especially in random regression parts had easier convergence and better fitting criteria on average. However, a model fitting quadratic B-Splines with 3 coefficients in fixed regression part and 3, 3, 2 and 2 coefficients for random direct additive genetic, permanent environmental, maternal genetic and maternal environmental effects, respectively was the best model. According to the best model, direct heritability (h2) was estimated in the range of 0.14–0.32 with a decrease from 60 to 120days of age and a subsequent increase to the end of trajectory. Coefficient of permanent environmental effects (p2) was in the range of 0.23–0.61 with an increasing trend throughout the trajectory. Maternal heritability (m2) and coefficient of maternal environment (c2) had low and negligible estimates, respectively. The results of the present study indicated potential of B-Splines for genetic evaluations of body weight in sheep, using RRMs.

Inflammatory Bowel Disease: Influence and Implications in Reproduction.

The incidence and prevalence of inflammatory bowel disease (IBD) continues to rise with time, signifying its emergence as a global disease. Clinical onset of IBD, comprising Crohn's disease and ulcerative colitis, typically occurs before or at peak reproductive age. Although active disease in female patients is associated with reduced fertility and adverse obstetric outcomes in pregnancy, the molecular mechanisms underlying this altered reproductive course, and its impact on IBD transmission to offspring, remain poorly understood. Clinical and experimental studies have now begun to elucidate the hormonal, environmental, and microbial factors that modulate immune-reproductive cross talk in IBD and define their impact on maternal health, fetal development, and heritability of disease risk. Evolving insight into maternal-fetal imprinting in IBD has important implications for patient counseling and disease management during pregnancy and may help predict clinical outcomes for both mother and child.

The application of six different models to estimate the genetic parameters, variance components and breeding values for birth weight of Holstein calves

ABSTRACTThis research was conducted to determine variance component, genetic parameters and breeding values (EBV) for the birth weight (BW) of Holstein calves. In this context, the direct genetic (), maternal genetic () and maternal permanent environmental effects, which affect BW, were separately assessed. The multi-trait, derivative-free restricted maximum likelihood programme was used for determining the effect of the genetic parameters by using models that either included or excluded the maternal genetic and/or permanent maternal environmental effects. The estimation of the BW of Holstein calves was optimized by evaluating six different models. The best model was chosen according to the log-likelihood ratio tests. Within the context of the study, a total of 4443 calves were investigated between 1987 and 2006. Among the six different models, model 4 was selected as the best model, since it had the lowest value for the likelihood ratio. The range of the values for direct heritability () and maternal heritability (m2) were between 0.07–0.13 and 0.04–0.09, respectively. In conclusion, an estimation of the genetic parameters for BW can be used as a selection criteria for Holstein calves.

Parameter estimates for reproductive and carcass traits in Nelore beef cattle

The aim of this study was to estimate genetic parameters for scrotal circumference at 365 (SC365) and 450 (SC450) days of age, age at first calving (AFC), ribeye area (REA), backfat (BF) thickness, and rump fat (RF) thickness, in order to provide information on potential traits for Nelore cattle breeding program. Genetic parameters were estimated using the Average Information Restricted Maximum Likelihood method in single- and multitrait analyses. Four different animal models were tested for SC365, SC450, REA, BF, and RF in single-trait analyses. For SC365 and SC450, the maternal genetic effect was statistically significant (P < 0.01) and was included for multitrait analyses. The direct heritability estimates for SC365, SC450, AFC, REA, BF, and RF were equal to 0.31, 0.38, 0.24, 0.32, 0.16, and 0.19, respectively. Maternal heritability for SC365 and SC450 was equal to 0.06 and 0.08, respectively. The highest genetic correlations were found among the scrotal circumferences. Testing for the inclusion of maternal effects in genetic parameters estimation for scrotal circumference should be evaluated in the Nelore breeding program, mostly for correctly ranking the animal's estimated breeding values. Similar heritability estimates were observed for scrotal circumference, as well as favorable genetic correlations of this trait with AFC and carcass traits. Thus, scrotal circumference measured at 365 days of age could be a target trait for consideration in the Nelore selection index in order to improve most of the traits herein analyzed.

Genetic evaluations for growth heat tolerance in Angus cattle.

The objectives were to assess the impact of heat stress and to develop a model for genetic evaluation of growth heat tolerance in Angus cattle. The American Angus Association provided weaning weight (WW) and yearling weight (YW) data, and records from the Upper South region were used because of the hot climatic conditions. Heat stress was characterized by a weaning (yearling) heat load function defined as the mean temperature-humidity index (THI) units greater than 75 (70) for 30 (150) d prior to the weigh date. Therefore, a weaning (yearling) heat load of 5 units corresponded to 80 (75) for the corresponding period prior to the weigh date. For all analyses, 82,669 WW and 69,040 YW were used with 3 ancestral generations in the pedigree. Univariate models were a proxy for the Angus growth evaluation, and reaction norms using 2 B-splines for heat load were fit separately for weaning and yearling heat loads. For both models, random effects included direct genetic, maternal genetic, maternal permanent environment (WW only), and residual. Fixed effects included a linear age covariate, age-of-dam class (WW only), and contemporary group for both models and fixed regressions on the B-splines in the reaction norm. Direct genetic correlations for WW were strong for modest heat load differences but decreased to less than 0.50 for large differences. Reranking of proven sires occurred for only WW direct effects for the reaction norms with extreme heat load differences. Conversely, YW results indicated little effect of heat stress on genetic merit. Therefore, weaning heat tolerance was a better candidate for developing selection tools. Maternal heritabilities were consistent across heat loads, and maternal genetic correlations were greater than 0.90 for nearly all heat load combinations. No evidence existed for a genotype × environment interaction for the maternal component of growth. Overall, some evidence exists for phenotypic plasticity for the direct genetic effects of WW, but traditional national cattle evaluations are likely adequately ranking sires for nonextreme environmental conditions.

Threshold analysis of genetic effects for secondary sex ratio in domestic sheep using Bayesian approach via Gibbs sampling

This study was conducted to estimate variance components, genetic parameters and genetic trends for secondary sex ratio (SSR) in three domestic sheep breeds of Iran (Guilan, Moghani and Shall) using threshold animal models. The data set and pedigree information of Guilan, Moghani and Shall sheep comprised 21,736 lambs born during 1994 to 2014, 35,076 lambs born during 1994 to 2012, and 64,964 lambs born during 1982 to 2012, respectively. Threshold animal models included direct and maternal genetic effects with covariance between them and maternal permanent environmental effects were implemented by Gibbs sampling methodology. Posterior mean estimates of direct heritabilities for SSR in Guilan, Moghani and Shall sheep were 0.042, 0.051, and 0.153, respectively. Also, posterior mean estimates of maternal heritabilities for SSR in Guilan, Moghani and Shall breeds were 0.050, 0.052, and 0.083, respectively. Estimates of correlations between direct and maternal genetic effects of SSR in Guilan, Moghani and Shall sheep breeds were negatively high and equal to −0.61, −0.64 and −0.90, respectively. Also, the posterior mean estimates of permanent environmental effect due to the dam were 0.038, 0.114 and 0.008 in Guilan, Moghani and Shall sheep breeds, respectively. Although the results of current study indicated low heritability estimates for SSR, but improvement of SSR in sheep seems possible in selection programs and applicable genetic variation in SSR can take advantage of sexual dimorphism for economically important traits such as growth related characters, which may, in turn, make possible greater intensity of selection and therefore greater genetic change, as well as decreasing the costs related to animal replacement.

Genetic parameters for large white pigs reared under intensive management systems in Kenya

ABSTRACTA lack of performance parameters is one of the factors limiting the implementation of sustainable breeding strategies for the pig industry in Kenya. The objective of this study was to estimate genetic and phenotypic parameters for growth performance of Large White pigs reared under intensive management systems in Kenya. Growth performance data of 1398 pigs with 10 428 records were obtained from the Kenya Agricultural and Livestock Research Organization (KALRO)-Naivasha. Random regression models were used to estimate variance components by fitting different orders of Legendre polynomials. Phenotypic variance increased with age from 3.43±0.28 to 2449.28±392.07, while direct heritability ranged between 0.20±0.04 and 0.52±0.08. Maternal heritability increased from 0.26±0.05 to 0.79±0.04 while permanent environmental heritability was between 0±0.01 and 0.15±0.10. Genetic correlations were greater than 0.48 between all weights and decreased with an increase in age intervals. The first three eigenvalues ...

Parâmetros e ganhos genéticos em características de crescimento de bovinos Tabapuã da Bahia

RESUMO Compararam-se dois modelos (com ou sem o efeito materno) na estimativa de parâmetros genéticos por meio do fator de Bayes (FB) e do critério de informação da deviance (DIC). Adicionalmente, avaliaram-se as tendências genéticas, maternas e fenotípicas em características de crescimento de bovinos da raça Tabapuã do estado da Bahia. O modelo que incluiu o efeito materno proporcionou menores valores de FB (167629,2; 117341,2 e 124804,8) e DIC (174550,0; 120242,7 e 128037,2) para pesos aos 205 (P205), 365 (P365) e 550 (P550) dias de idade, respectivamente. As estimativas médias, a posteriori, das herdabilidades diretas e maternas foram 0,33; 0,43 e 0,44 e 0,15; 0,14 e 0,16 para as três características, respectivamente. As tendências genéticas para o efeito direto foram de 0,4415 e 0,3613kg/ano para P205 e P365 e representam incrementos de apenas 0,25 e 0,15% nas médias das características ao ano. As tendências genéticas maternas para as três características demonstraram perdas e indicam ausência de seleção de matrizes para boa habilidade materna. Apesar de existir variabilidade genética suficiente para justificar ganhos genéticos via seleção, estes e os ganhos fenotípicos foram pequenos, sugerindo necessidade de melhorias genéticas e ambientais.

Short communication: Estimates of genetic parameters for dairy fertility in New Zealand.

Reproductive performance of dairy cows in a seasonal calving system is especially important as cows are required to achieve a 365-d calving interval. Prior research with a small data set has identified that the genetic evaluation model for fertility could be enhanced by replacing the binary calving rate trait (CR42), which gives the probability of a cow calving within the first 42d since the planned start of calving at second, third, and fourth calving, with a continuous version, calving season day (CSD), including a heifer calving season day trait expressed at first calving, removing milk yield, retaining a probability of mating trait (PM21) which gives the probability of a cow being mated within the first 21d from the planned start of mating, and first lactation body condition score (BCS), and including gestation length (GL). The aim of this study was to estimate genetic parameters for the proposed new model using a larger data set and compare these with parameters used in the current system. Heritability estimates for CSD and PM21 ranged from 0.013 to 0.019 and from 0.031 to 0.058, respectively. For the 2 traits that correspond with the ones used in the current genetic evaluation system (mating trait, PM21 and BCS) genetic correlations were lower in this study compared with previous estimates. Genetic correlations between CSD and PM21 across different parities were also lower than the correlations between CR42 and PM21 reported previously. The genetic correlation between heifer CSD and CSD in first parity was 0.66. Estimates of genetic correlations of BCS with CSD were higher than those with PM21. For GL, direct heritability was estimated to be 0.67, maternal heritability was 0.11, and maternal repeatability was 0.22. Direct GL had moderate to high and favorable genetic correlations with evaluated fertility traits, whereas corresponding residual correlations remain low, which makes GL a useful candidate predictor trait for fertility in a multiple trait evaluation. The superiority of direct GL genetic component over the maternal GL component for predicting fertility was demonstrated. Future work planned in this area includes the implementation and testing of this new model on national fertility data.

Direct and maternal genetic effects on growth, reproduction, and ultrasound traits in zebu Brahman cattle in Colombia.

Covariance components and genetic parameters were estimated for birth weight (BiW); adjusted weights at 4, 7, 12, and 18 mo; and ADG between 0 and 4 mo, between 4 and 7 mo, between 7 and 12 mo, and between 12 and 18 mo. Additionally, reproductive traits, calving interval, and age at first calving were analyzed, together with traits measured by ultrasound: loin eye area, deep fat mean, back fat, and rump fat. Analyses were performed using an animal model, considering the fixed effects of the farm ( = 37), year and month of birth, sex, calving number (1 to 7), season (dry and rainy seasons), region (North Coast, Andean Region, and Oriental Savannas), and conception (natural mating or AI), whereas the age of the cows at calving was considered a polynomial covariate with linear and quadratic effects. Three different models were used to find the one with the best fit for each trait: a single-trait model with an additive direct genetic effect, a single-trait model with additive direct and maternal genetic effects, and finally, a multitrait model with an additive direct genetic effect. For the growth traits, the heritability was between 0.24 and 0.47, with the lowest value for weight at 7 mo and the greatest value for BiW, and the maternal heritability was found to be between 0.15 and 0.21 but did not decrease later on. The correlation between direct and maternal effects was high and negative (-0.59 to -0.76). With ultrasound traits, a model with only direct effects was used. The heritability was between 0.13 and 0.28 for back fat and loin eye area, respectively. The heritabilities for deep fat mean and rump fat were similar, being 0.19 and 0.21, respectively. The reproductive traits showed high residual variance. In particular, the heritability of calving interval was low (0.06). The results showed that the growth traits have an important genetic component, which is a favorable indicator for obtaining improvement progress in the zebu Brahman breed for beef production in tropical regions of Colombia. The maternal effects influenced the weight performance from 4 to 18 mo and should be taken into account in genetic analyses. In general, the direct heritability of medium magnitude estimated for growth and traits measured by ultrasound suggests that individual selection for these traits will be effective.