Maternal Heritability Estimates Research Articles

Parent of origin genetic effects on milk production traits in a population of Iranian Holstein cows.

The aim was to estimate the relative contribution of imprinting effects from both paternal and maternal sides to phenotypic variation in milk production traits including 305 days milk yield (MY), average daily milk production (ADM), fat percentage (F%), protein percentage (P%), 305 days fat yield (FY), 305 days protein yield (PY), ratio of fat percentage to protein percentage (F:P) and somatic cell score (SCS) in Iranian Holstein cows. To do this, each trait was analysed with a series of four animal models, which were identical for fixed and additive genetic effects but differed for combinations of paternal and maternal imprinting effects. The log-likelihood ratio test (LRT) and Akaike's information criteria (AIC) were used to select the best model for each trait. Correlations between traits due to additive and imprinting effects were estimated by bivariate analyses. For all traits studied, fitting the imprinting effect led to a better data fit. Also, it resulted in a noticeable decrease in additive genetic variance from 8% (SCS) to 28% (F:P). A significant maternal imprinting effect was detected on all traits studied. Estimates of maternal imprinting heritability ( ) were 0.07 ± 0.02, 0.04 ± 0.01, 0.06 ± 0.01, 0.05 ± 0.01, 0.5 ± 0.01, 0.09 ± 0.02, 0.07 ± 0.02 and 0.06 ± 0.01 for MY, ADM, F%, P%, FY, PY, F:P and SCS, respectively. For F:P, in addition to the maternal imprinting effect, a significant paternal imprinting component was also detected with a 7% contribution to phenotypic variance of F:P. Estimates of direct heritability ( ) were 0.29 ± 0.02, 0.17 ± 0.01, 0.22 ± 0.02, 0.11 ± 0.01, 0.18 ± 0.02, 0.22 ± 0.02, 0.15 ± 0.04 and 0.06 ± 0.01 for MY, ADM, F%, P%, FY, PY, F:P and SCS, respectively. Maternal imprinting correlations (rmi) were in a wide range between -0.75 ± 0.15 (P%-SCS) and 0.95 ± 0.11 (MY-ADM). Additive genetic correlations (ra) ranged between -0.54 ± 0.05 (MY-P%) and 0.99 ± 0.01 (MY-ADM) and phenotypic correlations (rp) ranged from -0.30 ± 0.01 (MY-F%) to 0.93 ± 0.01 (MY-ADM). The Spearman's correlation between additive breeding values including and excluding imprinting effects deviated from unity especially for top-ranked animals implying re-ranking of top animals following the inclusion of imprinting effects in the model. Since including imprinting effects in the model resulted in better data fit and re-ranking of top animals, including these effects in the genetic evaluation models for milk production traits was recommended.

Evaluation of models for estimation of genetic parameters for post-weaning body measurements and their association with yearling weight in Nellore sheep.

The objective of this study was to obtain (co) variance components and genetic parameter estimates for post-weaning body measurements such as body length (BL), height at withers (HW), and chest girth (HG) recorded at six (SBL, SHW, and SHG), nine (NBL, NHW, and NHG) and twelve (YBL, YHW, and YHG) months of age along with yearling weight (YW) in Nellore sheep maintained at livestock research station, Palamaner, Andhra Pradesh, India and also the association among body measurements with YW was studied. Data on 2,076 Nellore sheep (descended from 75 sires and 522 dams) recorded between 2007 and 2016 (10 years) were utilized in the study. Lambing year, sex of lamb, season of lambing and parity of dam were included in the model as fixed effects and ewe weight was kept as a covariate. Analyses were conducted with six animal models with different combinations of direct and maternal genetic effects using restricted maximum likelihood procedure. Best model for each trait was determined based on Akaike's information criterion. Moderate estimates of direct heritability were obtained for the studied traits viz., BL (0.02 to 0.24), HW (0.31 to 0.49), and CG (0.08 to 0.35) and their corresponding maternal heritability estimates were in the range of 0.00 to 0.07 (BL), 0.13 to 0.17 (HW), and 0.07 to 0.13 (CG), respectively. Positive direct genetic and phenotypic correlations among the traits and they ranged from 0.07 (YBL-YW) to 0.99 (SBL-SHG, SHG-YW, and NBL-YBL) and 0.01 (SBL-YBL) to 0.99 (NBL-NHG), respectively. Further, the genetic correlations among all the body measurements and YW were positive and ranged from 0.07 (YW and YBL) to 0.99 (YW and SHG). There was a strong association of chest girth at six months with YW. Further, it is indicated that moderate improvement of post-weaning body measurements in Nellore sheep would be possible through selection.

Genetic correlation estimates between calving ease in primiparous cows and economically important traits in Nellore cattle.

This study aimed to estimate (co)variance components and genetic parameters for calving ease (CE) and their genetic correlations with growth, reproductive, carcass, and feed efficiency traits in Nellore cattle. Phenotypes for CE are scored in two categories: normal calving and assisted calving. The traits considered were probability of precocious calving, age at first calving, stayability, adjusted scrotal circumference at 365 days of age, accumulated cow productivity, age at puberty of males, gestation length, birth weight, adjusted weights at 210 and 450 days of age, adult cow weight, frame score, hip height, rib eye area, subcutaneous backfat thickness, rump fat thickness, intramuscular fat percentage, residual feed intake and dry matter intake. The estimation of genetic parameters was performed using a two-trait threshold-linear animal model, except for CE, stayability, and probability of precocious calving, which were evaluated through a two-trait threshold animal model. The direct (0.27) and maternal (0.19) heritability estimates for CE in heifers primiparous Nellore indicated that selecting for this trait is feasible. The selection to improve the female sexual precocity should consider CE during the selection and mating decisions to reduce calving problems. Genetic correlation estimates between CE and BW suggest that selecting low birth weight to reduce calving problems is not an appropriate strategy to improve calving ease in heifers Nellore. Therefore, adopting a multi-trait selection model with CE and BW in the Nellore breed would reduce calving difficulties, particularly in sexually precocious heifers, without impairing the growth, reproductive, feed efficiency conversion, and carcass indicator traits.

Genetic and environmental parameters for early growth and yearling traits of the Elsenburg South African Mutton Merino resource flock

The Elsenburg South African Mutton Merino (SAMM) resource flock has been maintained at the Elsenburg Research Farm in the Western Cape, South Africa since 1955. Early growth and lamb survival data (record numbers from 9512 for weaning weight or WW to 13101 for lamb survival LS) over the 66-year period from 1955 to 2020 and yearling weight and wool data (record numbers from 1351 the coefficient of variation of fibre diameter or CVFD to 3505 for clean yield or CY) over a 38-year period from 1983 to 2020 were used to estimate genetic and environmental parameters for the flock. The ASREML package was used to estimate fixed effects and genetic parameters. Birth year, sex, birth type and age of dam significantly (P < 0.001) influenced the weight traits and LS. The interaction between birth year and sex was evident in most early growth traits. Direct single-trait heritability estimates amounted to 0.11 ± 0.02 for birth weight (BW), 0.04 ± 0.01 for WW, 0.03 ± 0.01 for LS, 0.28 ± 0.04 for yearling weight (YW), 0.62 ± 0.04 for CY, 0.36 ± 0.04 for clean fleece weight (CFW), 0.33 ± 0.05 for staple length (SL), 0.56 ± 0.06 for CVFD, and 0.65 ± 0.04 for fibre diameter (FD). Maternal heritability estimates were 0.17 ± 0.02 for BW, and 0.06 ± 0.01 for WW. Maternal permanent environmental effects amounted to 0.08 ± 0.02 for BW, 0.04 ± 0.01 for WW, 0.04 ± 0.01, 0.07 ± 0.02 for YW and 0.05 ± 0.02 for CFW. Litter effects were 0.22 ± 0.01 for BW, 0.18 ± 0.02 for WW and 0.14 ± 0.01 for LS. Multi-trait heritability estimates compared well with the single-trait estimates. Genetic correlations for the weight traits in the three-trait analyses ranged from −0.23 ± 0.12 for BW and YW to 0.81 ± 0.09 for WW and YW. Genetic, environmental, and phenotypic correlations amongst yearling weight and wool traits in the six-trait analyses were low to moderate and mostly within the ranges from previous literature for wool breeds. It should be feasible to select for a balanced breeding objective based on economic considerations in the flock.

A meta-analysis of genetic parameter estimates for growth traits in fat-tailed sheep

This study aimed at using a random-effects model of meta-analysis to compile the estimates of direct heritability, maternal heritability, the ratio of the permanent environmental variance to phenotypic variance, the correlation between direct and maternal genetic effects for growth traits (body weights, average daily gains, and Kleiber ratios), and also genetic correlations among these traits in fat-tailed sheep. A total of 458 direct heritability estimates, 260 maternal heritability estimates, 217 estimates of the ratio of the permanent environmental variance to phenotypic variance, 144 estimates of the correlation between direct and maternal genetic effects, and 349 genetic correlations from articles which were published between 1978 and 2021 were used in the meta-analysis. Chi-square (Q) test was performed to measure heterogeneity and the I2 statistic was determined. The average direct heritability estimates for the studied traits were low to moderate and ranged from 0.108 (for Kleiber ratio from three to six-months of age (KR3–6)) to 0.258 (for Kleiber ratio from birth to six-months of age (KR0–6)). The average maternal heritability estimates for growth traits were low and varied from 0.056 (for KR3–6) to 0.142 (for birth weight (BW)). The average correlation estimates between direct and maternal genetic effects for growth traits were negative and varied from −0.826 (for KR3–6) to −0.039 (for three-months weight (3 MW)). The genetic correlation estimates between BW and other traits were low to moderate and ranged from 0.089 (between BW-KR0–3) to 0.472 (between BW-3 MW). Also, the genetic correlation estimate between 3 MW and average daily gain from three to six-months of age (ADG3–6) was low (0.187) and not significant, but genetic correlation estimates between 3 MW and other traits were moderate to high and varied from 0.637 to 0.853 (P < 0.05). The meta-analysis showed that growth traits in fat-tailed sheep were under low to moderate genetic control. The average genetic parameter estimates obtained in this study could be utilized in the genetic selection plans for fat-tailed sheep, especially when there is limited access to accurate phenotypic records or genetic parameter estimates for the studied traits.

Study of genetic parameters for pre-weaning growth traits in inner Mongolia white Arbas cashmere goats.

Inner Mongolia Arbas white cashmere goats is a dual-purpose breed for producing cashmere and meat. In recent years, its meat has become more and more popular among consumers because of rich nutrients and delicious flavor. Therefore, it is particularly important to study the genetic and non-genetic factors affecting the early growth traits and estimate variance components of pre-weaning growth traits of Inner Mongolia Albas white cashmere goats. A total of 37487 kidding records such as birth weight (BWT), weaning weight (WWT), average daily gain from birth to weaning (ADG) and Kleiber ratio (KR) from 343 sires and 7296 dams were used in this study. The most appropriate model was chosen on the basis of likelihood ratio test by fitting six models which excluding or including maternal genetic, maternal permanent environmental effects. The parameters were estimated under the most appropriate model using AIREML method by WOMBAT software. With the best model (Model 6), heritability estimates were 0.0435, 0.0911, 0.0932 and 0.2339 for BWT, WWT, ADG and KR traits, respectively. Maternal heritability estimates were 0.0143, 0.0246, 0.0220 and 0.0186 for BWT, WWT, ADG, and KR traits respectively. The correlation between different traits was estimated with the most suitable model by using bivariate analysis method. The direct additive genetic correlation among the traits ranged from -0.026 (BWT~KR) to 0.772 (ADG~KR). The maternal permanent environment correlation is between -0.289 (BWT-KR) ~0.900 (WWT-ADG). Results indicated that maternal effects and direct-maternal genetic covariance should be considered in any program aimed at improving pre-weaning growth traits to have an accurate genetic evaluation. In addition, positive and medium to high genetic correlations generally exist among WWT, ADG and KR due to the existence of genetic variation for early growth traits. The results showed that the genetic progress of these traits could be slowly through selection except for KR.

Environmental Effects and Genetic Parameters for Growth Traits of Lohi Sheep.

Estimating genetic parameters for growth traits is crucial to plan breeding strategies for improving meat production in indigenous sheep breeds. The study first tested the effects of environmental and maternal effects on five growth traits, including birth weight (BWT), weight at 120 days (WT120), weight at 180 days (WT180), weight at 270 days (WT270) and weight at 365 days of age (WT365) and then estimated genetic parameters for these traits using data obtained in 1215 Lohi sheep. The effects of factors, including year (YOB), season (SOB) and type of birth (TOB), age of dam (AOD) and sex on growth traits of Lohi sheep, were examined using analysis of variance (ANOVA) in R software. Sex, TOB and YOB significantly affected all studied traits. The estimates of direct and maternal heritability for BWT and WT120 were 0.15 ± 0.08 and 0.20 ± 0.06, and 0.45 ± 0.16, 0.21 ± 0.08, respectively. The direct heritability estimates for WT180, WT270 and WT365 were 0.20 ± 0.07, 0.21 ± 0.07 and 0.19 ± 0.08, respectively. Due to the high heritability estimate obtained for WT120 compared to other studied traits, and its strong genetic correlation (&gt;0.9) with post-weaning growth traits, it is recommended that selection must be practiced on WT120 to improve the growth performance of Lohi sheep. The results could be used for the development of genetic/genomic selection programs aiming to improve the production performance of the Lohi sheep.

Multivariate Animal Model-based Analysis of Fiber Traits in Kashmir Merino Sheep

ABSTRACT An attempt was made in the present study to elucidate the (co)variance components and genetic parameters of fiber traits in Kashmir Merino sheep population using multivariate animal model. The data pertained to a total of 6836 sheep lambs born over a period of 21 years (1997–2017) and included information on different fiber traits [greasy fleece weight at first (GFW1) and second (GFW2) clips; and fiber diameter (FD) and staple length (SL) at second clip]. Genetic analysis was undertaken using average information restricted maximum likelihood (AI-REML) algorithm in WOMBAT program. The model incorporated six fixed (sex of lamb, season and period of birth, farm of origin, breed and type of birth) and two random effects (direct additive genetic and maternal genetic effects without any covariance between them) in it. The additive genetic heritability estimates for fiber traits were 0.300 ± 0.031; 0.289 ± 0.022; 0.254 ± 0.029 and 0.189 ± 0.028 for GFW1, GFW2, FD, and SL, respectively. The maternal genetic heritability estimates were very low for all traits under study. The genetic correlation between different traits was positive and estimates ranged from moderate to high. The results from present study imply that the variation in these traits has genetic basis which can be exploited in the selection programmes for their improvement. The correlation between different fiber traits was found to be favorable, which can lead to indirect selection response upon formulation of efficient breeding programmes.

Estimation of nonadditive and additive genetic effects on growth traits of Horro cattle.

The estimation of nonadditive genetic effects plays a significant role in the accuracy of estimated breeding values for growth traits. Data for estimation of individual and maternal heterosis of crossbreed cattle in Ethiopia are limited to research institutions and universities. This paper aimed to estimate the crossbreeding effects for growth traits of Holstein Friesian × Horro and Jersey × Horro crossbreds in Ethiopia. The data included pedigree and weight data of animals born between 1980 and 2008. Heritability of growth traits was estimated using restricted maximum likelihood (ASREML). However, the additive genetic, maternal, and heterosis effects for growth traits of crossbred animals were estimated using the crossbreeding effects (CBE3) package by fitting Kinghorn's Model one. The direct and maternal heritability estimates for 1-year weight with the model that included the direct maternal covariance were 0.77 ± 0.12 and 0.26 ± 0.09, respectively. Individual heteroses estimated for Holstein Friesian × Horro and Jersey × Horro were significantly high and positive for 1-year weight (21.6 ± 6.7 and 26.0 ± 3.9kg), preweaning average daily gain (27.4 ± 26 and 28.9 ± 15g), and postweaning average daily gain (68.8 ± 16.6 and 61.8 ± 9.9g), respectively. The maternal additive genetic effect for growth traits was mostly positive; therefore, it may be preferable to use crossbred cows from purebred dams instead of crossbred cows from crossbred dams. The significantly higher heterosis and additive genetic parameters in Holstein Friesian × Horro crossbreds indicated that these crossbreds may be preferable to Jersey × Horro crossbreds in areas occupied by Horro cattle.

Bayesian threshold analysis of litter size in sheep

Background: Litter size at birth (LSB) is one of the most important economic traits in sheep and could be used in genetic improvement schemes for meat production. LSB is inherently a categorical trait and should be analysed with threshold models. Objective: Bayesian threshold models were used to analyze sheep LSB to estimate genetic parameters. Methods: Data was based on 7,901 LSB records from 14,968 dams and 682 sires collected from 1986 to 2012 at Makouie Sheep Breeding Station in Iran. Means of posterior distributions (MPDs) of LSB's genetic parameters were estimated, and the best-fitted models were selected using the deviance information criterion. Results: In the repeated measurement analysis, the estimated direct and maternal heritabilities, and permanent environmental effect (±SE), according to the best-fitted model (model 5), were 0.01 (0.010), 0.02 (0.014), and 0.01 (0.011), respectively. In the univariate analysis, the best estimates of direct and maternal heritabilities were 0.12 (0.064) and 0.08 (0.045), respectively. An increasing trend for direct and maternal heritabilities was observed in parity 2 (0.15 (0.082) and 0.25 (0.083), respectively). In the bivariate analysis, the best estimates of direct and maternal heritabilities for LSB were 0.03 (0.027) and 0.22 (0.041), respectively. The direct and maternal genetic correlations among parities were 0.25 (0.054) and 0.12 (0.021), respectively. Conclusions: The results showed a considerable influence of environmental factors on LSB in each parity of sheep; also, statistically different genetic parameters (p&lt;0.05) were obtained from one parity to another, indicating the different and large influences of genetic and environmental factors for each parity.

Thermal stress during late gestation impairs postnatal growth and provides background for genotype-environment interaction in Hereford-Braford and Angus-Brangus cattle

Heat stress suffered by pregnant cows can impair fetal development and have negative consequences for the future performance of calves. Thus, our objective was to determine the effect of heat stress during late gestation on birth weight (BW) and postnatal growth traits of Hereford-Braford and Angus-Brangus cattle from Brazil. In addition, we employ a reaction norm model to investigate the genotype by environment interaction (G × E) due to thermal stress in late gestation. The average temperature and humidity index of the last 60 days of gestation (THIg) was chosen as an environmental descriptor. The BW of animals was considerably lower for extreme low and high values of THIg. In contrast, the average daily gain from birth to weaning (ADG) and muscling score at weaning (MUS) were gradually reduced by increasing THIg values by -0.0014 kg /day/THIg -0.0119 units/THIg, respectively. The variation observed for the estimates of variances, direct and maternal heritability for BW, ADG, and MUS suggest that there is substantial heterogeneity of genetic variances along the environmental gradient. Thus, differences in response to selection are expected depending on the level of thermal stress where selection candidates are evaluated. Genetic correlation estimates for direct and maternal effects between distant THIg values differed from unity or were negative for all traits. This was another strong indication that few of the same genes are responsible for the same trait in contrasting thermal environments during late pregnancy. In this sense, the thermal environment during late gestation provides background for G × E and should be appropriately considered in genetic evaluations of Hereford-Braford and Angus-Brangus cattle reared on pasture in (sub)tropical regions.

Estimates of direct and maternal genetic effects on birth and weaning weights in Egyptian buffalo calves

A total of 1173 first calves of Egyptian buffalo kept at Mehalet Mousa Farm, belonging to Animal Production Research, Ministry of Agriculture, Dokki, Cairo, Egypt during the period from 2000 to 2015 were used to estimate variances of direct and maternal genetic effects for birth weight (BW) and weaning weight (WW). Two animal models are used. Model 1 (full model) includes month and year of birth and sex as fixed effects and direct genetic, maternal genetic, covariance between direct and maternal genetic and residual as random effects. Model 2 is similar to model 1 while additive maternal genetic and covariance between direct and maternal effects were omitted from the analysis. Year of birth and sex had highly significant effects on BW and WW, while month of birth had no significant effects on both traits studied. Bulls of the buffalo had highly significant effects on BW and WW. Direct heritability estimates for BW are 0.30 and 0.33, for Model 1 and Model 2, respectively. Direct heritability estimates for WW are 0.34 and 0.39 for Model 1 and Model 2, respectively. Maternal heritability estimates are 0.10 and 0.03 for BW and WW, respectively. Phenotypic and genetic correlations among BW and WW are positive and highly significant. These results indicate the important of maternal genetic effect on birth weight.

Genetic-quantitative uni- and bi-trait analysis for growth traits in the Colombian creole breed Blanco Orejinegro (BON).

The Blanco Orejinegro (BON) is a Colombian creole cattle breed that is not genetically well characterized for growth traits. The aim of this work was to estimate genetic parameters for birth weight (BW), weaning weight (WW), yearling weight (YW), daily weight gain between birth and weaning (DWG), time to reach 120kg of live weight (T120), and time to reach 60% of adult weight (T60%), and establish the selection criteria for growth traits in the BON population of Colombia. Genealogical and phenotypic information for BW, WW, YW, DWG, T120, and T60% traits of BON animals from 14 Colombian herds were used. These traits were analyzed with the AIREML method in a uni- and bi-trait animal model including the maternal effect for BW, WW, DWG, and T120. The direct heritability estimates values were 0.22 ± 0.059 (BW), 0.20 ± 0.057 (WW), 0.20 ± 0.153 (YW), 0.17 ± 0.07 (DWG), 0.26 (T120), and 0.44 ± 0.03 (T60%). The maternal heritability estimates values were 0.14 ± 0.040 (BW), 0.15 ± 0.039 (WW), 0.25 ± 0.06 (DWG), and 0.16 (T120). The direct genetic correlations were high ( >|0.60|) among all the traits, except between T60% with BW, WW, YW, and DWG (ranged from - 0.02 to - 0.51), all in a favorable direction. The results showed that there is genetic variation in the growth traits associated with the additive genetic effect, and they might respond to selection processes. Furthermore, genetic gains would improve through selection, especially for YW and T60% when WW is used as criterion.

Model definition for genetic evaluation of purebred and crossbred lambs including heterosis.

Crossbreeding is a common practice among commercial sheep producers to improve animal performance. However, genetic evaluation of U.S. sheep is performed within breed type (terminal sire, semi-prolific, and western range). While incorporating crossbred records may improve assessment of purebreds, it requires accounting for heterotic and breed effects in the evaluation. The objectives of this study were to: 1) describe the development of a paternal composite (PC) line, 2) determine the effect of direct and maternal heterosis on growth traits of crossbred lambs, 3) estimate (co)variance components for direct and maternal additive, and uncorrelated maternal environmental, effects, and 4) provide an interpretation of the estimates of random effects of genetic groups, and to use those solutions to compare the genetic merit of founding breed subpopulations. Data included purebred and crossbred records on birth weight (BN; n = 14,536), pre-weaning weight measured at 39 or 84 d (WN; n = 9,362) depending on year, weaning weight measured at 123 d (WW; n = 9,297), and post-weaning weight measured at 252 d (PW; n = 1,614). Mean (SD) body weights were 5.3 (1.1), 16.8 (3.9) and 28.0 (7.6), 39.1 (7.2), and 54.2 (8.7) kg for BN, WN (at the two ages), WW, and PW, respectively. In designed experiments, the Siremax, Suffolk, Texel, Polypay, Columbia, Rambouillet, and Targhee breeds were compared within the same environment. Estimates of heterotic effects and covariance components were obtained using a multiple trait animal model. Genetic effects based on founders' breeds were significant and included in the model. Percent estimates of direct heterosis were 2.89 ± 0.61, 2.60 ± 0.65, 4.24 ± 0.56, and 6.09 ± 0.86, and estimates of maternal heterosis were 1.92 ± 0.87, 4.64 ± 0.80, 3.95 ± 0.66, and 4.04 ± 0.91, for BN, WN, WW, and PW, respectively. Correspondingly, direct heritability estimates were 0.17 ± 0.02, 0.13 ± 0.02, 0.17 ± 0.02, and 0.46 ± 0.04 for BN, WN, WW, and PW. Additive maternal effects accounted for trivial variation in PW. For BN, WN, and WW, respectively, maternal heritability estimates were 0.16 ± 0.02, 0.10 ± 0.02, and 0.07 ± 0.01. Uncorrelated maternal environmental effects accounted for little variation in any trait. Direct and maternal heterosis had considerable impact on growth traits, emphasizing the value of crossbreeding and the need to account for heterosis, in addition to breed effects, if crossbred lamb information is included in genetic evaluation.

Analysis of genetic parameters and genetic trends for early growth and reproductive traits of Doyogena sheep managed under community-based breeding program

This study aims to estimate genetic parameters and genetic trends for early growth and reproductive traits of Doyogena sheep. Data used in the study were collected over 6 years (2013–2018). Studied traits were birth weight (BWT), weaning weight (WWT), 6-month weight (SMWT), average daily gains from birth to weaning (ADG0-3), average daily gains from weaning to 6-month age (ADG3-6), average daily gain from birth to 6-month age (ADG0-6), litter size (LS), lambing interval (LI), age at first lambing (AFL), and annual reproductive rate (ARR). (Co) variance components and genetic parameters were estimated using restricted maximum likelihood (REML). The analyses were carried out using WOMBAT program. Univariate analysis was applied to estimate genetic parameters. Six different animal models were fitted by including or excluding maternal effects. The direct heritability estimates for BWT, WWT, SMWT, ADG0-3, ADG3-6 and ADG0-6 were 0.33 ± 0.06, 0.31 ± 0.06, 0.14 ± 0.06, 0.13 ± 0.04, 0.11 ± 0.07, and 0.02 ± 0.05 respectively. Direct heritability for LS, LI, and AFL were 0.28 ± 0.12, 0.20 ± 0.5, and 0.001 ± 0.3, respectively. The maternal heritability estimates for BWT, WWT, and LS were 0.24 ± 0.12, 0.60 ± 0.07, and 0.24 ± 0.08, respectively. The genetic correlation between BWT with WWT and BWT with SMWT were 0.21 ± 0.07 and 0.21 ± 0.09, respectively. Genetic progress for most of the studied traits has shown promising improvements. Thus, continuation of selection, therefore, suggested for more improvements in the performance of Doyogena sheep. Direct heritability estimates decrease as lamb age increases and selection based on earlier body weight will be more efficient.

Parental imprinting effects on growth traits and Kleiber ratio in sheep

AbstractThe goal was to study imprinting effects on birth weight (BW), weaning weight (WW), six months weight (W6), pre- and post-weaning growth rate (GRa and GRb), and pre- and post-weaning Kleiber ratio (KRa and KRb) in Baluchi and Makuie sheep breeds. Analyses were done in a two steps process. In the first step, each trait was analysed with a series of 12 univariate animal models, including different combinations of direct and maternal effects and the best model was selected by the AIC criterion. In the second step, three new models were fitted by adding either maternal imprinting effect, paternal imprinting effect, or both of them, respectively, to the best model already selected in the first step, and changes in AIC were monitored. (Co)variances between traits were estimated using bivariate analyses. In Baluchi sheep, for BW, WW and W6, estimates of maternal imprinting heritability (${\boldsymbol h}_{{\boldsymbol mi}}^2$) were 0.12 ± 0.02, 0.08 ± 0.01 and 0.09 ± 0.01, respectively. In Makuie sheep, paternal imprinting heritability (${\boldsymbol h}_{{\boldsymbol pi}}^2$) for BW, WW, W6, GRb and KRb were 0.17 ± 0.05, 0.8 ± 0.05, 0.38 ± 0.10, 0.71 ± 0.15 and 0.65 ± 0.13, respectively. In Baluchi sheep, strong maternal imprinting correlations were observed between BW and WW (0.93 ± 0.05), BW and W6 (0.80 ± 0.07) and WW and W6 (0.91 ± 0.02). In Makuie sheep, paternal imprinting correlations ranged from −0.97 ± 0.33 (BW-GRb) to 0.99 ± 0.47 (GRb-KRb). It was concluded that imprinting effects need to be included in the statistical model to increase the accuracy of genetic evaluation. However, to have accurate and reliable estimates of imprinting effects, the availability of large data sets and deep pedigrees are necessary.

Influence of environmental factors and genetic variation on mitochondrial DNA copy number.

Mitochondrial DNA copy number (mtDNA CN) has been shown to be highly heritable and associated with traits of interest in humans. However, studies are lacking in the literature for livestock species such as beef cattle. In this study, 2,371 individuals from a crossbred beef population comprising the Germplasm Evaluation program from the U.S. Meat Animal Research Center had samples of blood, leucocyte, or semen collected for low-pass sequencing (LPS) that resulted in both nuclear DNA (nuDNA) and mitochondrial DNA (mtDNA) sequence reads. Mitochondrial DNA CN was estimated based on the ratio of mtDNA to nuDNA coverages. Genetic parameters for mtDNA CN were estimated from an animal model based on a genomic relationship matrix (~87K SNP from the nuDNA). Different models were used to test the effects of tissue, sex, age at sample collection, heterosis, and breed composition. Maternal effects, assessed by fitting a maternal additive component and by fitting eleven SNP on the mtDNA, were also obtained. As previously reported, mtDNA haplotypes were used to classify individuals into Taurine haplogroups (T1, T2, T3/T4, and T5). Estimates of heritability when fitting fixed effects in addition to the intercept were moderate, ranging from 0.11 to 0.31 depending on the model. From a model ignoring contemporary group, semen samples had the lowest mtDNA CN, as expected, followed by blood and leucocyte samples (P ≤ 0.001). The effect of sex and the linear and quadratic effects of age were significant (P ≤ 0.02) depending on the model. When significant, females had greater mtDNA CN than males. The effects of heterosis and maternal heterosis were not significant (P ≥ 0.47). The estimates of maternal and mtDNA heritability were near zero (≤0.03). Most of the samples (98%) were classified as haplogroup T3. Variation was observed in the mtDNA within Taurine haplogroups, which enabled the identification of 24 haplotypes. These results suggest that mtDNA CN is under nuclear genetic control and would respond favorably to selection.

Genetic Evaluations of Stillbirth for Five United States Dairy Breeds: A Data-Resource Feasibility Study.

Genetic selection has been an effective strategy to improve calving traits including stillbirth in dairy cattle. The primary objectives of the present study were to characterize stillbirth data and determine the feasibility of implementing routine genetic evaluations of stillbirth in five non-Holstein dairy breeds, namely Ayrshire, Guernsey, Milking Shorthorn, Brown Swiss, and Jersey. An updated sire-maternal grandsire threshold model was used to estimate genetic parameters and genetic values for stillbirth. Stillbirth data with the birth years of dams from 1995 to 2018 were extracted from the United States national calving ease database maintained by the Council on Dairy Cattle Breeding. The extracted stillbirth records varied drastically among the five dairy breeds. There were approximately 486K stillbirth records for Jersey and more than 80K stillbirth records for Brown Swiss. The direct and maternal heritability estimates of stillbirth were 6.0% (4.5–7.6%) and 4.7% (3.3–6.1%) in Jersey and 6.8% (3.2–10.5%) and 1.1% (0.6–2.9%) in Brown Swiss. The estimated genetic correlations between direct and maternal genetic effects for stillbirth were −0.15 (−0.38 to −0.08) in Jersey and −0.35 (−0.47 to −0.12) in Brown Swiss. The estimated genetic parameters for stillbirth in these two breeds were within close ranges of previous studies. The reliabilities of predicted transmitting abilities in Jersey and Brown Swiss increased substantially, thanks to the substantial increase in available stillbirth data in the past 10 years. The stillbirth records for Ayrshire, Guernsey, and Milking Shorthorn, which ranged approximately between 3K and 12K, are insufficient to implement reliable routine genetic evaluations of stillbirth in these three dairy breeds. Estimated genetic (co)variances and genetic values deviated considerably from the reported ranges of previous studies, and the reliabilities of predicted transmitting abilities were low in these three breeds. In conclusion, routine genetic evaluations of stillbirth are feasible in Brown Swiss and Jersey. However, reliable genetic evaluations of stillbirth in Ayrshire, Guernsey, and Milking Shorthorn require further data collection on stillbirth.

Genetic study of quantitative traits supports the use of Guzerá as dual-purpose cattle

ObjectiveThe aim of this study was to estimate genetic parameters for 305-day cumulative milk yield and components, growth, and reproductive traits in Guzerá cattle.MethodsThe evaluated traits were 305-day first-lactation cumulative yields (kg) of milk (MY305), fat (FY305), protein (PY305), lactose (LY305), and total solids (SY305); age at first calving (AFC) in days; adjusted scrotal perimeter (cm) at the ages of 365 (SP365) and 450 (SP450) days; and adjusted body weight (kg) at the ages of 210 (W210), 365 (W365), and 450 (W450) days. The (co)variance components were estimated using the restricted maximum likelihood method for single-trait, bi-trait and tri-trait analyses. Contemporary groups and additive genetic effects were included in the general mixed model. Maternal genetic and permanent environmental effects were also included for W210.ResultsThe direct heritability estimates ranged from 0.16 (W210) to 0.32 (MY305). The maternal heritability estimate for W210 was 0.03. Genetic correlation estimates among milk production traits and growth traits ranged from 0.92 to 0.99 and from 0.92 to 0.99, respectively. For milk production and growth traits, the genetic correlations ranged from 0.33 to 0.56. The genetic correlations among AFC and all other traits were negative (−0.43 to −0.27). Scrotal perimeter traits and body weights showed genetic correlations ranging from 0.41 to 0.46, and scrotal perimeter and milk production traits showed genetic correlations ranging from 0.11 to 0.30. The phenotypic correlations were similar in direction (same sign) and lower than the corresponding genetic correlations.ConclusionThese results suggest the viability and potential of joint selection for dairy and beef traits in Guzerá cattle, taking into account reproductive traits.

Genetic parameters of average daily gain and kleiber ratio in mecheri sheep

The objective of study was to estimate the genetic parameters for average daily gain and feed efficiency in Mecheri sheep in an organized farm. Atotal of 2516 records collected over a period of 10 years (2010 to 2019) were utilised for the study. The least-squares means for average daily gain (ADG) at different periods viz., ADG1, ADG2 and ADG3 were 89.83±1.38, 43.06±1.61 and35.65±1.41 g, respectively and the means for Kleiber ratio (KR) for KR1, KR2 and KR3 were15.20±0.10, 5.63±0.18 and 3.49±0.12, respectively. The direct heritability estimates for ADG1, ADG2, ADG3, KR1, KR2 and KR3 were 0.14±0.05, 0.06±0.04, 0.04±0.04, 0.14±0.05, 0.08±0.05and 0.05±0.04,respectively and the corresponding maternal heritability estimates were 0.03±0.02, 0.01±0.02, 0.05±0.03, 0.02±0.02, 0.01±0.03 and 0.06±0.03, respectively. The geneticcorrelations of ADG1 were highly positive with ADG3 and KR1 and negative with ADG2 (−0.697) and KR2 (−0.843). The genetic correlations of KR1 with other traits ranged between -0.049 and 0.988 and KR2 had high genetic correlation (0.974) with only ADG2. It is crucial to consider any negative relationships between the pre- and post-weaning development characteristics when putting the breeding methods into practice. ADG and KR from birth to three months should be considered, since heritability estimates and the strength of the genetic and phenotypic correlations were strong at this stage of development.