Permanent Environmental Effects Research Articles

Genetic parameters for test-day milk yield, lactation persistency, and fertility in low-, medium-, and high-production systems in Kenya

Genetic parameters for test-day milk yield, lactation persistency, and age at first calving (as a fertility trait) were estimated for the first 4 lactations in multiple-breed dairy cows in low-, medium-, and high-production systems in Kenya. Data included 223,285 test-day milk yield records from 11,450 cows calving from 1990 to 2015 in 148 herds. A multivariate random regression model was used to estimate variance and covariance components. The fixed effects in the model included herd, year, and test month, and age as a covariate. The lactation profile over days in milk (DIM) was fitted as a cubic smoothing spline. Random effects included herd, year, and test month interaction effects, genetic group effects, and additive genetic and permanent environmental effects modeled with a cubic Legendre polynomial function. The residual variance was heterogeneous with 11 classes. Consequently, the variance components were varied over the lactation and with the production system. The estimated heritability for milk yield was lower in the low-production system (0.04-0.48) than in the medium- (0.22-0.59) and high-production (0.21-0 60) systems. The genetic correlations estimated between different DIM within lactations decreased as the time interval increased, becoming negative between the ends of the lactations in the low- and medium-production systems. Low (0.05) to medium (0.60) genetic correlations were estimated among first lactation test-day milk yields across the 3 production systems. Genetic correlations between the first lactation test-day milk yield and age at first calving ranged from 0.27 to 0.49, 0 to 0.81, and -0.08 to 0.27 in the low-, medium-, and high-production systems, respectively. Medium to high heritabilities (0.17-0.44) were estimated for persistency, with moderate to high (0.30-0.87) genetic correlations between 305-d milk yield and persistency. This indicates that genetic improvement in persistency would lead to increased milk yield. The low to medium genetic correlations between test-day milk yield between production systems indicate that sires may be re-ranked between production systems. Therefore, we conclude that sires should be selected based on a genetic evaluation within the target production system.

Genetic and nongenetic factors influencing ewe prolificacy and lamb body weight in a closed Romanov flock.

The U.S. Meat Animal Research Center was the first entity in the United States to import the Romanov breed and it has been maintained as a closed flock for over 30 yr. Incorporating this super-prolific breed into crossbred and composite populations has resulted in large improvements in ewe productivity. However, few have quantified factors contributing to genetic and nongenetic variation in ewe reproduction and lamb growth within purebred Romanov populations, which were the objectives of this study. The pedigree contained a total of 8,683 lambs born to 218 and 1,600 unique sires and dams, respectively. Number of lambs born on a per ewe exposed (NLBE) and lambing (NLBL) basis were analyzed in univariate repeatability animal models. As expected, the proportion of phenotypic variance (σP2) in litter size attributable to additive genetic (0.06 to 0.08) and permanent environmental (0.05 to 0.07) effects of the ewe was low. The service sire permanent environmental effect contributed to a small but significant amount of σP2 in NLBE (0.03) but not NLBL. However, the service sire additive genetic effect did not influence σP2 in NLBE or NLBL. Lamb body weight was recorded at birth (BWB) and upon weaning from either milk replacer (~30 d; BWW-N) or their dam (~60 d; BWW-D) and were analyzed in a three-trait model with random additive direct and maternal effects. Estimated direct heritabilities were low for all body weight (BW) traits (0.07 to 0.10). Maternal heritability was moderate for BWB (0.34) but low for weaning BW (0.11 to 0.18). This was the first to report direct and maternal genetic correlations between BW of nursery- and dam-reared lambs, and both were estimated to be moderate (0.43 to 0.47). Additionally, the direct and maternal effects of BWB were more strongly correlated with BWW-N (0.74 to 0.82) than BWW-D (0.17 to 0.33). Despite inbreeding coefficients having increased at a rate of 0.33% per birth year (1986 to 2019) in this flock, they were not consistently associated with reductions in ewe or lamb performance. Parameter estimates generally agreed with those from less-prolific breeds, and results indicate that selection can be an effective means of improving subcomponents of ewe productivity.

Characterising the Influence of Genetics on Breast Muscle Myopathies in Broiler Chickens.

This report provides the first estimates of the genetic basis of all key breast muscle myopathies (BMM) in broiler chickens [Deep pectoral myopathy, wooden breast, white striping and spaghetti breast] and their relationship with body weight and breast yield. Data from a pure bred high yielding commercial broiler line were analysed to estimate the genetic parameters using a multivariate animal model with the appropriate fixed effects and permanent environmental effect of the dam. Heritabilities of the BMM ranged from 0.04 to 0.25 and the genetic correlation of the BMM with body weight and breast yield ranged from -0.06 to 0.41. Here we highlight that the genetic variance of BMM accounts for a low proportion of the phenotypic variance and the BMM have a low genetic relationship with performance traits. The large contribution of residual variance to the phenotypic variance for the BBM was >71.5% which indicates the importance of the non-genetic effects on BMM. The data presented also show that the moderate to low genetic influence for the development of BMM can be used, through balanced selection, to reduce the myopathy incidence in the long term. The impact of genetic selection against BMM was tested empirically by comparing the incidence of WB and % breast yield of a commercial broiler with a high generation (HG) broiler. The HG broiler used represents 2 years of genetic improvement compared to the commercial broiler; the HG broiler had an 18.4% relative decrease in WB and a 1.02% relative increase in breast yield compared to the commercial broiler. This paper describes the relationship between the genetic and non-genetic factors influencing BMM highlighting the importance of understanding the non-genetic effects on myopathy incidence. It also shows that the genetic component of BMM can be reduced whilst at the same time improving breast yield as part of balanced breeding goals.

Evaluation of animal models for genetic analysis of growth performance in Landlly pigs

Selection of the most appropriate animal model for the estimation of genetic parameters for body weight was carried out using restricted maximum likelihood (REML) procedure at birth and thereafter at 3, 6, and 8 weeks of age in Landlly pigs. Six different models were fitted for each trait; by inclusion or exclusion of maternal additive genetic effect, maternal permanent environmental effect, and covariance between direct and maternal additive genetic effects. Records on 1968 piglets, born in 4 parities of 131 gilts/sows, sired by 68 boars during a period of 5 years from 2014 to 2018 were used. In order to determine the most appropriate model, Log likelihood values, log the likelihood ratio test and Akaike's information criterion were used. A model including direct additive genetic and maternal permanent environmental effects fitted best to data for birth weight. The best model explaining W3, W6, and W8 included direct additive genetic, maternal genetic and maternal permanent environmental effect with direct and maternal genetic covariance. Total heritability estimates for the body weights were low to moderate across best models.

Using random regression models to estimate genetic variation in growth pattern and its association with sexual maturity of Thai native chickens

ABSTRACT 1. Genetic (co)variances and parameters between body weights (BW) across the growth trajectory were estimated using a univariate random regression (RR) animal model. The effect of growth rates (GH) on age at first egg (AFE) and egg weight at first egg (EWFE) were explored using a series of univariate and bivariate analyses. 2. Body weights were taken from Thai native chickens at hatch day to 168 days of age. The model included interactions between age with hatch nested within year and sex as fixed effects, and random effects of direct additive genetic, direct permanent environmental, maternal genetic and maternal permanent environmental effects. All random effects were fitted as regressions to animals’ age via quadratic Legendre polynomials and fitting six classes of residual variances was identified as an optimal variance structure to estimate parameters. 3. Genetic and phenotypic variances for BW increased with increasing age. Estimated heritabilities for direct additive (h2 a) and maternal genetic (h2 m) effects on BW traits ranged from 0.34 to 0.54, and 0.04 to 0.06, respectively. Estimated variance ratios for direct (c2 ape) and maternal permanent environmental (c2 mpe) effects ranged from 0.19 to 0.48 and 0.10 to 0.12, respectively. Estimated correlations between weights at different ages were high for all random effects. 4. Estimated h2 a for six GH traits ranged from 0.06 to 0.28, while for AFE and EWFE these were 0.24 and 0.16, respectively. Estimated h2 m and c2 mpe were low for GH. Estimated genetic correlations between GH and AFE ranged from −0.22 to 0.02 and, between GH and EWFE, ranged from −0.05 to 0.40. These estimates suggested that selecting high GH chickens at 28 days of age can be expected to reduce AFE and to increase EWFE.

Estimation of variance components and genetic parameters for lactation persistency indices in crossbred cattle using Bayesian and REML methods

The present investigation was carried out to estimate variance components and genetic parameters for different lactation persistency indices and their association in Jersey crossbred cattle, maintained at the Eastern Regional Station, National Dairy Research Institute, Kalyani, Nadia, West Bengal, India. Data on lactation traits (part lactation yields and 305-days milk yield) comprising all lactations of 378 Jersey crossbred cattle were collected over a period of 35 years (1982–2016) and used to calculate the different lactation persistency indices (P21, P31, P32, P4 and P5) of animals by ratio method. Data were analyzed using single trait repeatability model using Restricted Maximum Likelihood (REML) algorithm and Bayesian approach. In both the models, the direct heritability estimates were low in magnitude and ranged from 0.01 to 0.05 for the studied traits. The permanent maternal environmental (c2) effects of different lactation persistency indices accounted for 2–19% of the total phenotypic variance under both the models in this study. The repeatability estimates of different persistency indices ranged from 0.06 to 0.20 in this study under both the models. Using Bayesian model, the genetic correlations between all lactation persistency indices were medium to high and positive except between P21 and P32. Medium to high and positive correlations (both residual and phenotypic correlations) also existed between lactation persistency indices except between P21 and P32 and between P32 and P5 in this study.The low heritability estimates of all the persistency measures in both the estimation methods indicate little scope of genetic improvement of lactation persistency of animals through selection.

Genetic analysis of persistency indices of milk yield in Jersey crossbred cattle.

The study reported in this Research Communication was conducted to estimate genetic parameters for different lactation persistency indices and their association with reproductive traits in Jersey crossbred cattle. Data on lactation traits (part lactation yields and 305-days milk yield) comprising all lactations as well as reproductive traits viz. calving interval, conception rate and gestation length of 378 Jersey crossbred cattle, maintained at National Dairy Research Institute, Kalyani, West Bengal, India, were collected over a period of 35 years (1982-2016). Five lactation persistency indices of animals (P21, P31, P32, P4 and P5) were calculated using ratio method. A total of six different animal models, ignoring or including maternal genetic or permanent environmental effects, were fitted for all persistency traits. The best model was chosen after testing the improvement of the log-likelihood values. The estimates of direct heritability were low in magnitude and ranged from 0.02 to 0.14 for the studied traits under the best fitted animal model. The permanent maternal environmental (c2) effects of different lactation persistency indices accounted for 2-9% of the total phenotypic variance in this study. Estimated genetic correlations of lactation persistency indices with all studied reproductive traits were low to moderate and negative (-0.11 to -0.68), except for calving interval. Phenotypic correlations of lactation persistency measures with studied reproductive traits were low (0.01 to 0.15). The low heritability estimates of all the persistency indices indicate some limited scope of genetic improvement of lactation persistency of animals through selection under the prevailing management conditions.

Genetic parameters of somatic cell scores using random regression test-day models with Legendre polynomials in Tunisian dairy cattle

The aim of this study was to analyse the genetic parameters of test-day somatic cell scores (TDSCS) in Tunisian dairy cattle using random regression models (RRM) with homogeneous residual variances. Data included 43,647 test-day somatic cell count (TDSCC) records collected on 4825 Holstein-Friesian cows with parities up to the fifth, and calving dates between 2000 and 2014. Records of the same animal belonging to different lactations were treated as repeated records. Additive genetic (AG) and permanent environmental (PE) random effects were fitted using Legendre polynomials functions (LP) up to the fifth-order. The models included fixed regressions on days-in-milk (DIM), modelling the average phenotypic curve using Ali-Schaeffer's lactation function. Overall, three models (LP3, LP4 and LP5) where compared using the -2log marginal density for Bayes factor (-2logp) and the deviance information criterion (DIC). Models were also compared by similarities between the estimated breeding values and genetic trends. For all models, the total variances tended to decrease during the first month of the lactation, then they maintained a nearly constant trend. All models showed the largest AG and PE variances at the beginning and at the end of lactation with an oscillating pattern in the middle. The heritability estimates of from the three models ranged from 0.01 to 0.08 with the lowest heritability estimates being in the mid-lactation period. Genetic correlations between adjacent DIM were high and then decreased as the intervals widened. All the best statistical criteria were obtained with the LP5 model, however, no differences were observed between the estimated 305 average breeding values (EBV305) from the three models. This assumes that the LP3 model can be selected as a parsimonious model since it contains the smallest number of parameters. This RRM study provided a good insight into the changes in genetic merit of the somatic cell score trait in Tunisian dairy cattle and that an EBV for the SCS should be included in the selection programs. It also showed the benefits given of using RRMs to perform national genetic evaluations of dairy cattle for milk production traits in Tunisia.

Genetic analysis of growth and egg production traits in synthetic colored broiler female line using animal model

Variance and genetic parameters were estimated for growth and production traits of synthetic broiler female line (PB-2) using REML animal model to delineate the population status, direct additive, maternal genetic, permanent environmental effects, besides genetic trends and performance of economic traits. The overall least squares mean (LSM) for body weights at 0day (BW0), at 2weeks (BW2), at 4weeks (BW4), at 5weeks (BW5), shank length at 5weeks (SL5), and breast angle at 5weeks (BA5) of age were 40.03g, 207.40g, 589.58g, 828.51g, 76.89cm, and 80.78°, respectively. The overall LSM for egg production up to 40weeks of age (EP40) and egg weight at 40weeks (EW40) were 66.02 eggs and 58.23g, respectively. The heritability estimates using the best model for BW0, BW2, BW4, BW5, SL5, and BA5 were 0.06 ± 0.03, 0.19 ± 0.03, 0.15 ± 0.03, 0.14 ± 0.02, 0.08 ± 0.02, and 0.02 ± 0.01, respectively. The heritability estimates were low to moderate in the magnitude for all early growth traits. The heritability estimate for egg production up to 40weeks (EP40) was 0.30 ± 0.05. The heritability estimates for adult body weights at 20 and 40weeks of age (BW 20 and BW 40), age at sexual maturity (ASM), and egg weight at 40weeks (EW40) were 0.21 ± 0.04, 0.19 ± 0.04, 0.16 ± 0.03, and 0.33 ± 0.05, respectively, and the estimates were moderate to high in magnitude. Model 4 with additive, maternal permanent environmental, residual, and phenotypic effects was the best model for growth traits except for BW0 and BA5. The average genetic gain observed in primary trait (BW5) over the five generations was 13.62g per each generation indicating effective selection. The animal model minimized the overestimation of genetic parameters and improved the accuracy of the BV, thus enabling the breeder to select the suitable breeding strategy for genetic improvement.

GENETIC PARAMETERS OF BODY WEIGHT AND MEASUREMENTS TRAITS IN BALADI BLACK RABBITS

ABSTRACT: A total of 250 progeny of 17 sires and 58 dams from Baladi Black breed population were used to estimate variance components and heritability of growth traits. Traits studied were individual body weight (BW12), body length (BL12), head length (HL12) and thigh circumference (TC12) all at 12 weeks of age. Single-trait Animal Model (DFREML) was used to estimate genetic variance components, as well as permanent environmental variation. Estimates of variance components were 0.52, 0.96, 0.91 and 0.81 for BW12, BL12, TC12 and HL12, respectively. Heritability estimates were 0.24, 0.36, 0.36 and 0.33 for BW12, BL12, TC12 and HL12 respectively. The proportions of variance due to permanent environmental effect of dams were 0.08, 0.05, 0.10 and 0.12 for BW12, BL12, TC12 and HL12, respectively. Results showed that out of the principal components (PC) calculated, the one represent 68.98 % of the total variance. The PC1 was 68.98 of the generalized variance. Principal component factor scores expound 77 % of the variation in the body weight of rabbits. Conclusively, the use of orthogonal body shape characters (PC1) derived from the principal component factor solution could be more reliable in predicting body weight compared to the use of the original autocorrelated body measurements. This is because multicollinearity of interdependent explanatory variables could lead to false inferences when original body measurements are used as predictors. Key words: Body measurements, multicollinearity, Rabbits, Principal Component Analysis.

Genetic and environmental parameters and trends for early growth and yearling traits in the Elsenburg Dormer resource flock

Abstract The Dormer is a composite breed and constitutes the most numerous terminal sire breed in South Africa. The Elsenburg Dormer flock is the foundation flock of the breed and is still being maintained at the Elsenburg research farm in the Western Cape province of South Africa. Data from 1943 to 2019 were used to investigate genetic and environmental parameters and trends for early growth traits and lamb survival (LS) in the flock. Yearling live weight- and wool traits were recorded for a shorter period from 2008 to 2018. REML-procedures were used to estimate fixed effects as well as genetic parameters and trends in the flock. The fixed effects of birth year, sex, birth type and age of dam had a significant influence on all the early growth traits. There was an interaction between birth year and sex for most traits. Direct single-trait heritability estimates were 0.15 for birth weight (BW), 0.06 for weaning weight (WW), 0.02 for LS, 0.19 for yearling weight (YW), 0.63 for clean yield, 0.56 for clean fleece weight, 0.59 for staple length, 0.59 for staple strength, 0.60 for coefficient of variation of fibre diameter and 0.80 for fibre diameter. Maternal genetic effects amounted to 0.21 for BW, 0.08 for WW and 0.06 for YW. Dam permanent environmental effects ranged from 0.03 for LS to 0.08 for BW and litter effects from 0.12 for LS to 0.28 for BW. Multi-trait heritability estimates were fairly consistent with the above single-trait estimates. Genetic correlations among live weight traits ranged from low (-0.11) for BW and YW to very high (0.93) for WW and YW. Genetic correlations of YW with wool traits ranged from low to moderate. Genetic correlations among wool traits were mostly consistent with literature estimates for wool breeds. Genetic trends for all weight traits suggested a significant positive trend with time. Expressed relative to the overall phenotypic mean, these trends amounted to 0.12 % for BW, 0.16 % for WW and 0.45 % for YW. The study indicated that all traits were heritable and variable. Purposeful selection for a well-defined objective should allow faster genetic improvement than the annual rates of gain that were realised.

Combining Threshold, Thurstonian and Classical Linear Models in Horse Genetic Evaluations for Endurance Competitions.

Simple SummaryEndurance competitions are carried out across the countryside worldwide, where the adapted physical and metabolic conditions of the horses are essential to satisfactorily end the competition. Horse breeding programs usually use the rank and time to improve the performance of horses in competitions. It is also relevant to analyse the placing trait i.e., whether or not a horse finishes the race. The discontinuous nature of rank and placing traits require special methodologies to deal with them. Here we have used 6135 endurance records from 1419 horses, with a pedigree containing 10,868 animals, to develop a multitrait model with a new free software tool (GIBBSTHUR). The obtained results suggest that it is possible to ignore the race time and use rank and placing to perform the genetic evaluation in endurance horse populations.The racing time and rank at finish traits are commonly used for endurance horse breeding programs as a measure of their performance. Even so, given the nature of endurance competitions, many horses do not finish the race. However, the exclusion of non placed horses from the dataset could have an influence on the prediction of individual breeding values. The objective of the present paper was to develop a multitrait model including race time (T), rank (R) and placing (P), with different methodologies, to improve the genetic evaluation in endurance competitions in Spain. The database contained 6135 records from 1419 horses, with 35% of the records not placed. Horse pedigree included 10868 animals, with 52% Arab Horses. All models included gender, age and race effect as systematic effects and combined different random effects beside the animal and residual effects: rider, permanent environmental effect, and interaction horse-rider. The kilometers per race was included as a covariate for T. Heritabilities were estimated as moderately low, ranging from 0.06 to 0.14 for T, 0.09 to 0.15 for P, and 0.07 to 0.17 for R, depending on the model. T and R appeared mostly as inverse measures of the same trait due to their high genetic correlation, suggesting that T can be ignored in future genetic evaluations. P was the most independent trait from the genetic correlations. The possibility of simultaneously processing the threshold, Thurstonian and continuous traits has opened new opportunities for genetic evaluation in horse populations, and much more practical genetic evaluations can be done to help a proper genetic selection.

Selecting sheep for Haemonchus contortus resistance and susceptibility: Flock dynamics and genetic architecture

The study was carried out in the selected strains of Malpura and Avikalin sheep for nematode resistance versus susceptibility (Malpura resistant: MR, Malpura susceptible: MS, Avikalin resistant: AR and Avikalin susceptible: AS). Strains were selected since 2004 and inter-se breeding followed since year 2007. The objective was to decipher the genetic structure of strains and to estimate genetic parameters for fecal egg count (FEC). The population size was small (107–279); however, all the four flocks had sizable effective population size (fe) for founders. The ratio for fe to effective number of ancestors (fa) was nearly 1 indicating genetic stability. Inbreeding was under control. The log transformed FEC (LFEC) was significantly (P < .05) affected by sex, year and month of recording for all 4 strains. Generation had desired genetic trend. There was low heritability for LFEC in MR(0.02), MS(0.06), AR(0.07) and AS(0.02). The estimate of the permanent environment effect (c2) was low. Repeatability (ρ) for LFEC were 0.05, 0.11, 0.07 and 0.06 for MR, MS, AR and AS, respectively. Pruning the data for repeated records in peak infection period (1: “Aug-Sep” and 2: only “Sep”) resulted in considerable increase in ρ for MR (Aug-Sep: 0.07 ± 0.03 and Sep: 0.12 ± 0.07) and AR (Aug-Sep: 0.05 ± 0.04 and Sep: 0.09 ± 0.10). Results revealed genotype x environment interaction for repeated measures across months. Low flock size and low genetic variability are hurdles for improvement in R strains. It is recommended to incorporate new candidates post selection from the other breeding flocks and admit them in the R strains for selective breeding.

Genetic trends for the growth rates and Kleiber ratio in Avikalin sheep

Robust genetic progress and positive response to selection occurred in growth rate. The tangible increase in the genetic trends for early ADG and KR over the 40 years. Presence of additive genetic variation specifies selection that favors higher gain. KR has high genetic and phenotypic correlation with ADG for Avikalin sheep. KR as selection criterion will produce fast growing animals with limited resources. Avikalin sheep has been developed for higher growth rate and wool yield, however, wool has lost its market value over time. The aim of the study was to know the genetic potential of Avikalin for growth and also to suggest a selection criterion for higher growth with feed conversion efficiency. A total of 6296 animals descended from 2048 dams and 390 sires spread over a period of 41 years (1976–2016) at ICAR-Central Sheep and Wool Research Institute (CSWRI), Avikanagar were used for the analysis. Genetic trends were obtained for average daily gain (ADG) from birth to weaning (ADG1), weaning to 6-month (ADG2), 6-month to 12-month (ADG3) and Kleiber ratios of corresponding age (KR1, KR2 and KR3) in crossbred Avikalin sheep. Co(variance) components and genetic parameters were estimated by univariate and bivariate animal models using the average information restricted maximum likelihood (AIREML) by excluding or including maternal genetic or maternal permanent environmental effects. Significant and high additive genetic variances were observed for all the traits. Decreasing trends were observed for maternal effects as age advances. The genetic trends for ADG and KR up to 6 month age were positive and had substantial increment over the years indicating the impact of selection that favored higher gain in body weight at early ages. However positive and desired genetic trend at early ages (≤6 months), had an inverse relationship with genetic gain or trend at a later age (>6 month). Moderate estimates of the total heritability ( h T 2 ) 0.14, 0.18, 0.11, 0.19, 0.13 and 0.14 were obtained for ADG1, ADG2, ADG3, KR1, KR2 and KR3, respectively. This indicates the scope of direct selection for these traits for further improvement. The positive and desired genetic and phenotypic correlations between ADG and their corresponding KR suggested the scope of indirect selection for growth rate if lambs are selected for higher feed efficiency based on KR.

Random regression models for the evaluation of the growth of goats of the Anglonubian breed

ABSTRACT A total of 6593 weight records collected from 796 male and female Anglo-Nubian goats aged up to 130 days, offspring from 29 sires and 225 dams, were used to compare models and estimate genetic parameters throughout the growth curve by applying random regression models. Direct and maternal additive genetic effects and direct and maternal permanent environmental effects were included as random in the models. The contemporary groups were included as fixed effects and goat age at kidding was included as a covariable (linear and quadratic). The choice of the best model was based on the AIC, BIC and AICc criteria. Variance estimates of the four random effects increased as the animals aged. Direct heritability (h2) rose from 0.13 to 0.40 with age, whereas maternal heritability showed a low value. Genetic correlations of weight between closer ages were high. The most suitable random regression model to compare the fitting of random effects was that which employed the Legendre polynomials of quadratic order with homogeneous variance (3333-1).

Effectiveness of Genetic Parameter Estimation in a Small Flock of Merino Sheep with Shallow Pedigree

In this study, the genetic and non-genetic parameters were estimated for growth traits of Karacabey merino sheep. Growth performance data refer to 1863 lambs born between 2016 and 2018. Analyses were carried out by restricted maximum likelihood fitting animal models and disregarding or including maternal genetic or maternal permanent environmental effect. Six different animal model were fitted for all traits, and the most suitable model for each trait was chosen after Akaike information criterion test (AIC). Year of birth, age of dam, type of birth and lamb sex were significant sources of variation on birth weight (BW), average daily gain (ADG), Kleiber ratio (KR), weaning weight (WW) and six month weight (6MW). Direct heritability (h^2) for BW, ADG and 6MW were 0.12, 0.02 and 0.04, respectively, however, for KR and WW were 0.00 model 6 (which the best). The estimates of maternal heritability (m^2) for ADG, KR and WW were 0.12, 0.04 and 0.04, respectively in model 5, also maternal heritability were low for BW and 6MW. Maternal permanent environmental effects (c^2) have high contribution to the explanation growth traits and were estimated between 0.19 and 0.75 for these traits. These results showed that selecting for improved maternal and/or direct effects for Karacabey merino in the herd would generate very slow genetic improvement in growth traits.

Variance component analysis of growth and production traits in Vanaraja male line chickens using animal model.

ObjectiveA comprehensive study was conducted to study the effects of partition of variance on accuracy of genetic parameters and genetic trends of economic traits in Vanaraja male line/project directorate-1 (PD-1) chicken.MethodsVariance component analysis utilizing restricted maximum likelihood animal model was carried out with five generations data to delineate the population status, direct additive, maternal genetic, permanent environmental effects, besides genetic trends and performance of economic traits in PD-1 chickens. Genetic trend was estimated by regression of the estimated average breeding values (BV) on generations.ResultsThe body weight (BW) and shank length (SL) varied significantly (p≤0.01) among the generations, hatches and sexes. The least squares mean of SL at six weeks, the primary trait was 77.44±0.05 mm. All the production traits, viz., BWs, age at sexual maturity, egg production (EP) and egg weight were significantly influenced by generation. Model four with additive, maternal permanent environmental and residual effects was the best model for juvenile growth traits, except for zero-day BW. The heritability estimates for BW and SL at six weeks (SL6) were 0.20±0.03 and 0.17±0.03, respectively. The BV of SL6 in the population increased linearly from 0.03 to 3.62 mm due to selection. Genetic trend was significant (p≤0.05) for SL6, BW6, and production traits. The average genetic gain of EP40 for each generation was significant (p≤0.05) with an average increase of 0.38 eggs per generation. The average inbreeding coefficient was 0.02 in PD-1 line.ConclusionThe population was in ideal condition with negligible inbreeding and the selection was quite effective with significant genetic gains in each generation for primary trait of selection. The animal model minimized the over-estimation of genetic parameters and improved the accuracy of the BV, thus enabling the breeder to select the suitable breeding strategy for genetic improvement.

Estimation of genetic parameters for dairy traits and somatic cell score in the first 3 parities using a random regression test-day model in French Alpine goats

Lactation curve shape can affect an animal's health, feed requirements, and milk production throughout the year. We implemented a random regression model for the genetic evaluation of lactation curve shapes of dairy traits in French Alpine goats for their first 3 parities. Milk, fat, and protein yields, fat and protein contents, somatic cell score, and fat/protein ratio were considered. The data consisted of test-day records from 49,849 first lactation Alpine goats during their first 3 lactations. The reference model used a Legendre polynomial of order 2 for each parity to describe the genetic and permanent environmental effects, and was compared with a model that combined the second and third parities. A rank reduction of the variance-covariance matrix was also performed using an eigenvalue decomposition for each parity from the 2 models. Genetic parameters were consistent between the models tested. With a reduction to rank 2 and combining the second and third parities, the first 2 principal components correctly summarized the genetic variability of milk yield level and persistency, with a near-nil correlation between the 2, and with a much shorter computation time than the reference model. A favorable correlation of +0.43 between milk yield persistency and fat/protein ratio persistency at the beginning of the lactation was found from buck estimated breeding values.

Atopic dermatitis in a cohort of West Highland white terriers in Switzerland. Part II: estimates of early life factors and heritability.

There is accumulating evidence in studies of allergic diseases in humans and dogs that environmental experiences during the first months of life can influence the development of allergic disease. No prospective study has evaluated this in veterinary medicine. To assess early-life risk factors for canine atopic dermatitis (cAD) and estimate its heritability. A West Highland white terrier birth cohort (n=107) followed up to three years of age recording the development of cAD. The effect of environmental factors [house dust mites (HDM), hygiene, feeding, lifestyle] and early-life determinants [breeder, mode of delivery, birth season, sex, litter size, early-life immunoglobulin E (IgE) levels] were assessed, using Stata SE 15.1 statistical analysis. Heritabilities were estimated using the R program packages MCMCglmm and QGglmm. Maternal allergic status [P=0.013, odds ratio (OR 3.3)], male sex (P=0.06), mode of delivery (P=0.12), breeder (P=0.06), presence of HDM (P=0.11) and environmental hygiene level (P=0.15) were identified as possible influence factors by bivariate analyses. In the multivariate analysis the male sex was significantly associated with the development of cAD in the offspring (P=0.03, OR 2.4). The heritabilities on the observed scale were 0.31 (direct), 0.04 (maternal genetic effects) and 0.03 (maternal permanent environmental effects). These results suggest that several environmental factors could influence the development of cAD but clearly demonstrate the genetic influence of the individual and the dam. Further studies are needed to identify specific environmental factors, which could be potential targets for primary disease intervention.

Genetic parameter estimates for growth performance of crossbred piglets

The direct heritability estimates for piglet weights in pre and post weaning stages were moderate and improvement through mass selection is plausible. In the pre-weaning stage, the piglets had maximum genetic potential at birth (BW) to be exploited through direct selection. The 3 random effects, namely direct additive, maternal additive and litter permanent environmental effects had significant roles during different phases of pre-weaning growth and all must be included in the model used for formulating a breeding program. For post-weaning traits, the direct additive and permanent litter effects were the predominant factors governing the variability. The non-significance of postweaning maternal influence was as per expectation because the piglets moved away from maternal care after 8thweekof age.