Temporary Environmental Effects Research Articles

Early growth performance in the Murciano-Granadina goats: insights from genetic and phenotypic analyses

Abstract This study investigates the genetic and phenotypic aspects of early growth performance in the Murciano-Granadina goat breed, using data collected between 2016 and 2022 from a private dairy farm in Ghale-Ganj city, located in the southern area of Kerman province, Iran. Pedigree and data information were collected on several early body weight traits, including birth weight (BW), weaning weight (WW), average daily gain (ADG), Kleiber ratio (KR) and growth efficiency from birth to weaning (GE). Nine univariate animal models included direct additive genetic effects and different combinations of maternal effects were compared by using Akaike information criterion (AIC). Among the tested models, the best genetic analysis model for BW, included direct additive, maternal additive, maternal permanent and maternal temporary environmental effects. The best model for ADG, KR and GE included direct additive, maternal permanent and litter effects. For WW, the best model was determined to be one that included direct additive and maternal additive genetic effects. The estimated direct heritabilities were low values of 0.04, 0.07, 0.08, 0.05 and 0.07 for BW, ADG, KR, GE and WW, respectively. The estimates of genetic correlations among the studied traits were positive and low to high in magnitude which ranged from 0.11 for BW-KR to 0.91 for BW-GE. The phenotypic correlations ranged from 0.03 for KR-WW to 0.87 for ADG-KR. The positive correlations observed among the studied growth traits of the Murciano-Granadina goat breed indicate no negative genetic or phenotypic changes associated with selection for these traits.

Additive genetic and environmental variation interact to shape the dynamics of seasonal migration in a wild bird population.

Dissecting joint micro-evolutionary and plastic responses to environmental perturbations requires quantifying interacting components of genetic and environmental variation underlying expression of key traits. This ambition is particularly challenging for phenotypically discrete traits where multiscale decompositions are required to reveal non-linear transformations of underlying genetic and environmental variation into phenotypic variation, and when effects must be estimated from incomplete field observations. We devised a joint multistate capture-recapture and quantitative genetic animal model, and fitted this model to full-annual-cycle resighting data from partially-migratory European shags (Gulosus aristotelis) to estimate key components of genetic, environmental and phenotypic variance in the ecologically critical discrete trait of seasonal migration versus residence. We demonstrate non-negligible additive genetic variance in latent liability for migration, resulting in detectable micro-evolutionary responses following two episodes of strong survival selection. Further, liability-scale additive genetic effects interacted with substantial permanent individual and temporary environmental effects to generate complex non-additive effects on expressed phenotypes, causing substantial intrinsic gene-by-environment interaction variance on the phenotypic scale. Our analyses therefore reveal how temporal dynamics of partial seasonal migration arise from combinations of instantaneous micro-evolution and within-individual phenotypic consistency, and highlight how intrinsic phenotypic plasticity could expose genetic variation underlying discrete traits to complex forms of selection.

Estimates of genetic parameters, principal components and cluster analysis for milk yield and body weight in Guzera cattle

Context The estimation of genetic parameters for traits related to the production of milk, beef or both may assist in defining the selection criteria and objectives of the breeding program, as well as in the identification and selection of genetically superior animals. Aims The objectives of this study were to estimate genetic parameters for body weight and 305-day milk yield of Guzera cattle and to perform cluster analysis on the basis of estimated breeding values for these traits, to identify groups of animals that could be selected for the production of beef, milk or dual purpose. Methods Body weights (N = 253 012) of males and females were ecorded at 120 days of age (BW120), at weaning (WW), at 365 days (BW365), at yearling stage (YW) and at 24 months (BW24), and 6237 complete lactations (MY305) of 4723 cows were used to estimate the genetic parameters. The bi-trait animal models included direct additive genetic, maternal permanent environmental and temporary random effects for body weights and additive genetic, permanent environmental and temporary environmental random effects for MY305. The fixed effects for all the traits were contemporary group and age of cow at calving. Key results The estimates of heritability ranged from 0.14 ± 0.01 for WW to 0.23 ± 0.01 for MY305. The genetic correlations between body weights at different ages and milk yield were positive and ranged from 0.27 ± 0.11 to 0.38 ± 0.19. Two principal components explained 86.74% of the total genetic variance among the traits. Conclusions Cluster analysis identified four different clusters and showed that the Guzera breed had bulls with different genetic patterns that permits genetic selection for beef, milk or dual purpose. Implications The genetic correlations of the present study suggest that selection to increase milk yield will lead to a slight genetic gain in the same direction for body weight at different ages, in contrast to reports from some other studies.

36 Factors influencing racing performance in Polish Thoroughbreds and Purebred Arabian horses

Horse racing serves as a performance test to evaluate the speed and endurance of horses. Globally, the breed most widely used for racing is the Thoroughbred. In Poland, the Purebred Arabian horse racing sector size is comparable to that of Thoroughbreds, as the racing merit is a crucial element of the complex Polish breeding goal for Arabian horses. In many cases, the elite Thoroughbred mares – both in Poland and internationally – fail to perform as broodmares. However, the heritability of racing performance is proven to be higher in the dam line than in the sire line. In contrast, elite Polish Arabian racing mares usually produce elite racing offspring, and this relationship is observed through many generations. Polish State Studs conduct a particular racing program for the best racing mares, who are bred with race-type stallions (without the novel French-origin sire lines). The aim of this study was to identify the factors influencing the racing performance of Polish Thoroughbreds and Purebred Arabians and compare the effects of these factors in both breeds, with special emphasis put on the effect of dam's racing performance on the racing performance of their offspring. 1099 Thoroughbreds and 1022 Purebred Arabians were included in this study. The impact of each factor was evaluated using logistic and mixed linear regression models. We also created a correlation matrix to find additional dependencies between variables. In both Thoroughbreds and Purebred Arabians, a positive relationship between the racing performance of dams and their offspring was observed, except the elite Thoroughbred mares’ (4+ wins) progeny, which had 7,918% less chance ( P < 0,001) to enter the race. The chance for progeny both for entering the race and for good racing performance decreased with the dam's age. For instance, Arabian horses out of mares 13 years and older had 17,856% less chance ( P < 0,001) than the offsprings of mares aged 4–6. The age of the maternal grand-dam was significant in one of the models. Additionally, the fixed effects of the sire and maternal grandsire were significant, leading to the conclusion that at least 2 generations of ancestors must be considered while analyzing the chances of an individual performing well at the racetrack. A small percentage of the phenotypic variation explained by applied models suggests the importance of various fixed and temporary environmental effects affecting racing performance. The general conclusion is that in both breeds, the offspring of young mares with good but not elite racing performance has the best chances to win a race.

Building a Social Mandate for Climate Action: Lessons from COVID-19

The COVID-19 imposed lockdown has led to a number of temporary environmental side effects (reduced global emissions, cleaner air, less noise), that the climate community has aspired to achieve over a number of decades. However, these benefits have been achieved at a massive cost to welfare and the economy. This commentary draws lessons from the COVID-19 crisis for climate change. It discusses whether there are more sustainable ways of achieving these benefits, as part of a more desirable, low carbon resilient future, in a more planned, inclusive and less disruptive way. In order to achieve this, we argue for a clearer social contract between citizens and the state. We discuss how COVID-19 has demonstrated that behaviours can change abruptly, that these changes come at a cost, that we need a ‘social mandate’ to ensure these changes remain in the long-term, and that science plays an important role in informing this process. We suggest that deliberative engagement mechanisms, such as citizens’ assemblies and juries, could be a powerful way to build a social mandate for climate action post-COVID-19. This would enable behaviour changes to become more accepted, embedded and bearable in the long-term and provide the basis for future climate action.

Milk production of imported Holstein cows over different environment

Indonesia is importing genetically superior Friesian Holstein (FH) cows as breeding stocks for domestic dairy cattle population. The milk production of these imported cows, however, are very much affected by temporary environmental effect due to the habitat changes and transportation. This study aimed to observe the consistency of milk production of imported cows viewed from the repeatability estimates. In total, milk yield records on lactation one (L1), two (L2) and three (L3) of 70 imported FH cattle were obtained from Baturaden Dairy Cattle Breeding Centre. The repeatability values were estimated with intraclass correlation method utilizing information from three lactation periods. Milk yield decreased over lactation periods which were 6077.55±1239; 4821.79±888 and 4374.6±1012 kg for L1, L2, and L3 respectively. The repeatability of milk yield trait in this population was 0.41. It indicates 59% of the variation in milk yield is controlled by the unknown error term, including temporary environmental effects. Imported cows undergone extreme adaptation processes to be able to live optimally in a new environment which would modify their physiology. We suspect environmental changes and resource differences between tropical and subtropical climates triggers different trait expression as the explanation of the phenomenon.

The application of recursive multivariate model for genetic evaluation of early growth traits in Raeini Chasmere goat: A comparison with standard multivariate model

Data collected on 2638 kids originated from 1305 dams and 197 sires during 1979 to 2012 in Raeini Cashmere goat breeding station located in Baft, Kerman province, south-eastern part of Iran, on body weights of 2638 Raeini Cashmere kids at birth (BW), at weaning (WW) and at six-month age (6 MW) were used to adopt a fully recursive multivariate model considering causal effects from BW on WW and on 6 MW and from WW on 6 MW. The adopted recursive multivariate model (RMM) was compared with a standard multivariate mixed model (SMM), in which causal relationships were ignored, in terms of deviance information criterion (DIC), predictive ability and the estimates of genetic and phenotypic parameters. Preliminary analyses revealed that the importance of direct additive genetic, maternal permanent environmental and temporary environmental effects for genetic evaluation of all the studied traits. Maternal additive genetic effects were only influencing on BW. Model comparisons via DIC revealed the plausibility of RMM over SMM; DIC value obtained by fitting RMM (-15,218.76) was lower than that of obtained under SMM (21,654.92). For BW, lower mean square of error (MSE) and higher Pearson's correlation coefficient between the observed and predicted values (r(y,y^)) were obtained under SMM but in the case of WW and 6 MW lower MSE and higher r(y,y^) were obtained under RMM. The causal effects of BW on WW and on 6 MW and that of WW on 6 MW were 1.94 kg, 2.48 kg and 1.03 kg, respectively. The estimates of direct heritability, maternal heritability (for BW) and ratio of permanent and / or temporary environmental variances to phenotypic variance were not significantly affected by model fitted (SMM and RMM). Direct additive genetic correlations of BW-WW and BW-6 MW were not statistically significant under SMM (95% HPD interval included zero) but the corresponding estimates under RMM were significant (99% HPD interval did not include zero) values of 0.28 and 0.84, respectively; implying that genes associated with BW also increase WW and 6 MW in Raeini Cashmere goat. Direct genetic correlation estimate for WW-6 MW were 0.88 (under SMM) and 0.29 (under RMM). Generally, RMMs perform better than SMMs and may provide a better explanation to biological relationships among the studied traits.

Variance components for direct and maternal effects on body weights of Katahdin lambs.

The aim of this study was to estimate genetic parameters for BW in Katahdin lambs. Six animal models were used to study direct and maternal effects on birth weight (BWT), weaning weight (WWT), and postweaning weight (PWWT) using 41,066 BWT, 33,980 WWT, and 22,793 PWWT records collected over 17 yr in 100 flocks. Models included fixed effects of management group, dam age, type of birth (for BWT) or birth and rearing (for WWT and PWWT), and lamb age at weighing (fitted as a covariate for WWT and PWWT; all < 0.05). Variance components for random effects were estimated in sequentially more complex models and tested for significance with likelihood-ratio tests. A model that fitted only an additive animal effect overestimated additive variance for all BW, resulting in larger estimates of direct heritability than models that included maternal effects. Maternal effects explained variation ( < 0.05) in all BW. Heritability estimates for optimal models were 0.15 ± 0.01 for BWT, 0.18 ± 0.02 for WWT, and 0.20 ± 0.02 for PWWT. Estimates of maternal heritabilities were 0.14 for BWT, 0.10 for WWT, and 0.06 for PWWT, with SE = 0.01. Permanent environmental maternal effects explained 4 to 6% (±1%) of total phenotypic variances for these BW. Litter effects included temporary environmental effects common to littermates and a proportion of the dominance genetic variance and accounted for 16 to 19% (±1%) of phenotypic variance. Correlations between additive direct and maternal genetic effects were -0.14 for BWT, -0.23 for WWT, and -0.04 for PWWT but differed from 0 ( < 0.05) only for WWT. The total heritability predicted the total response in direct and maternal genetic effects from mass selection and was 0.23 for BWT, 0.20 for WWT, and 0.23 for PWWT. Direct and maternal additive, maternal permanent environmental, residual, and phenotypic correlations between BWT and WWT were 0.53 ± 0.05, 0.58 ± 0.06, 0.51 ± 0.06, 0.39 ± 0.01, and 0.44 ± 0.01, respectively; those between BWT and PWWT were 0.45 ± 0.06, 0.58 ± 0.08, 0.36 ± 0.08, 0.33 ± 0.01, and 0.37 ± 0.01 respectively; and those between WWT and PWWT were 0.85, 0.99, 0.92, 0.77, and 0.81, respectively, with SE ≤ 0.02. Therefore, both direct and maternal effects had an important impact on BW in Katahdin lambs. Models that included both additive and permanent environmental maternal effects as well as a temporary environmental litter effect should result in more accurate estimates of breeding values and better selection decisions.

Genetic description of growth traits in Markhoz goat using random regression models

The objective of the present study was to estimate genetic parameters and genetic trends for body weight traits in Markhoz goat using random regression (RR) models. In this study, 12,116 test-day body weight records of 3078 Markhoz goats, from birth to 365days of age, were used to compare RR models in which fixed and random effects were modeled using Legendre polynomials. The best model for direct genetic and maternal temporary environmental effects (common litter) included cubic, for direct permanent environmental effect included quadratic and for maternal permanent environmental effect included linear Legendre polynomials with a heterogeneous error structure. Direct heritability increased from 0.17 at birth to 0.32 at 120days of age then decreased suddenly to 0.27 at 240days of age and increased thereafter. Some estimates for the highest ages with the least records tended to be overestimated, in particular heritability beyond 340days. Variances due to direct permanent and maternal permanent environmental effects, respectively, were the highest and the lowest compared with the other sources of variation. This study has demonstrated the possibility of application of RR models for routine genetic evaluation of Markhoz goat in Iran. Although the results confirm that there is a scope for genetic improvement in growth pattern in Markhoz goat, but the genetic changes of body weight for selected ages (120-d and 200-d) have not shown a substantial tendency among the years.

Modelling genetic improvement of Pabna cattle in Bangladesh

ABSTRACTIn this study, individual cow performance for milk yield, fat yield, protein yield, liveweight and longevity were simulated using a stochastic approach. Additive genetic effects, permanent and temporary environmental effects, and herd and age effects were included in the model along with inclusion of Mendelian sampling. The model generated 10,000 Pabna cows distributed across 200 herds with the herd size ranging between 40 and 60 milking cows. The model ran for 20 years with bulls being selected based on daughter production (progeny testing (PT)) in one scenario and on parent average genetic merit in another. Selection of replacement cows and bulls was based on one of three following objectives: genetic merit for milk yield, milk and survival, and total genetic merit which included all five traits. Each year, 150 cows with the best predicted genetic merit were selected for the production of replacements. The breeding scheme using selection of new bulls and cows based on parent average showed higher genetic gains than the PT for all selection objectives due to the differences between generation interval, accuracy and size of the progeny group/bull. The highest genetic gain was obtained when the selection objective was for milk yield genetic merit (US$15.02/year) compared with total genetic merit (US$10.95/year).

Estimation of genetic parameters and maternal effects for body weight at different ages in D’man sheep

The objective of this study was to estimate the genetic parameters for birth weight (BW), weight at 30 days (W30), 90 days (W90) and 135 days (W135) of D’man sheep. Records used in the study were collected over a period of 25 years (1988–2012) from 4728 lambs that descended from 129 sires and 621 dams. (Co) variance components and genetic parameters were estimated with univariate and bivariate animal models using the restricted maximum likelihood (REML) procedure. Age of dam, type of birth, sex of lamb and period of birth showed significant effects on studied weights, so they were considered as in the analysis models. Twelve different animal models were fitted by including or excluding maternal additive genetic effects, maternal permanent environmental effect, maternal temporary environmental effect and covariance between direct-maternal additive genetic effects. The most appropriate model for each trait was determined based on Akaike’s Information Criterion (AIC). Bivariate analysis was performed using the most appropriate models obtained in univariate analysis. Based on the best model, direct heritability estimates were 0.05±0.02, 0.03±0.02, 0.08±0.03 and 0.12±0.04 for BW, W30, W90 and W135, respectively. Maternal effects significantly influenced the growth traits. The maternal heritability for BW, W30 and W90 were 0.10±0.02, 0.07±0.03 and 0.07±0.03, respectively. Direct-maternal additive genetic correlations were negative and medium ranging from −0.04 to −0.54 for BW, W90 and W135, but positive and medium to high for W30 (0.25–0.71). The maternal permanent environmental effects as a proportion of total variance were 0.10, 0.05 and 0.09 for W30, W90 and W135, respectively. The maternal temporary environmental effects were 0.18, 0.09, 0.08 and 0.07 for BW, W30, W90 and W135, respectively. The estimates of direct genetic correlation between BW–W30, BW–W90, BW–W135, W30–W90, W30–W135 and W90–W135 were 0.84±0.23, 0.66±0.24, 0.81±0.15, 0.92±0.09, 0.93±0.05, 1.00±0.01, respectively. The estimates of the phenotypic correlation among traits were positive and ranged from 0.31 for BW–W135 to 0.87 for W90–W135. In conclusion, maternal effects on weights of D’man sheep are important and need to be considered in any selection programme undertaken for this breed.

The contribution of additive genetic variation to personality variation: heritability of personality.

Individual animals frequently exhibit repeatable differences from other members of their population, differences now commonly referred to as 'animal personality'. Personality differences can arise, for example, from differences in permanent environmental effects--including parental and epigenetic contributors--and the effect of additive genetic variation. Although several studies have evaluated the heritability of behaviour, less is known about general patterns of heritability and additive genetic variation in animal personality. As overall variation in behaviour includes both the among-individual differences that reflect different personalities and temporary environmental effects, it is possible for personality to be largely genetically influenced even when heritability of behaviour per se is quite low. The relative contribution of additive genetic variation to personality variation can be estimated whenever both repeatability and heritability are estimated for the same data. Using published estimates to address this issue, we found that approximately 52% of animal personality variation was attributable to additive genetic variation. Thus, while the heritability of behaviour is often moderate or low, the heritability of personality is much higher. Our results therefore (i) demonstrate that genetic differences are likely to be a major contributor to variation in animal personality and (ii) support the phenotypic gambit: that evolutionary inferences drawn from repeatability estimates may often be justified.

Estimates of genetic parameters of growth traits of Nellore cattle in the Midwest region of Brazil

Records of birth weight (BW) and weights standardized to 210 (W210); 365 (W365) and 550 (W550) of age in the Nellore breed were used to estimate variance components of genetic effects and predict genetic values of sires. The model included the fixed effects of contemporary group and cow age at calving as co-variable, and the additive and maternal genetic, permanent maternal environmental, and temporary environmental random effects. Estimates of means and standard deviations for BW, W210; W365 and W550 were 32.76 ± 3.74; 184.30 ± 29.02; 240.31 ± 41.85 and 322.12 ± 60.77, respectively. A significant additive genetic variability was detected for all weights. The permanent maternal environmental variance showed greater relevance on weaning weight, and it was practically inexistent after weaning. For the maternal genetic variance, the estimate for birth weight was more significant as compared with weaning weight. The estimated heritability values for BW, W210; W365 and W550 were 0.37 ± 0.02; 0.36 ± 0.03; 031 ± 0.01 and 0.38 ± 0.02, respectively. Genetic correlations between birth weight and other weights were of low magnitude, with high values of weights at other ages. The use of sires of higher genetic value for total maternal effect makes it possible to use sires that are more positive for weaning weight and also for year and yearling weight.

Model comparisons and genetic parameter estimates of growth and the Kleiber ratio in Shal sheep

Abstract. Genetic and phenotypic parameters were estimated for lamb growth traits for the Shal sheep using an animal model. Data on lamb growth performance were extracted from available performance records at the Shal sheep Station in Qazvin, Iran. Studied traits were body weights of lambs at birth (BW), at 3 months of age as weaning weight (WW), 6 months weight (6MW), 9 months weight (9MW), yearling weight (YW), average daily gain from birth to weaning (ADG) and Kleiber ratio from birth to weaning (KR). Significant random effects for each trait were determined by fitting additive direct genetic effects, additive maternal effects, covariance between additive direct and additive maternal effects, maternal permanent environmental and maternal temporary environmental (common litter) effects under twelve animal models. Univariate analyses were carried out under the most appropriate model, determined by AIC test. Direct heritability estimates for BW, WW, ADG, KR, 6MW, 9MW and YW were 0.13, 0.19, 0.18, 0.05, 0.16, 0.18 and 0.19, respectively. Maternal additive genetic effects were fitted only for BW and WW; corresponding estimates of 0.12 and 0.10 obtained for maternal heritability of BW and WW, respectively. Maternal permanent environmental effects have low contribution in expression of KR and lead to estimates of 0.06 and 0.06 for maternal permanent environmental variance as a proportion of phenotypic variance (c2) of these traits, respectively. All pre-weaning traits, except KR, were affected by litter effects. The magnitude of ratio of common litter variance to phenotypic variance (l2) was 0.05, 0.12 and 0.14 for BW, WW and ADG, respectively. Direct genetic correlations were positive and ranged from 0.09 for KR-YW to 0.80 for WW-ADG; phenotypic ones ranged from 0.18 for KR-YW to 0.87 for WW-ADG.

Modelagem do efeito materno e estimativa de parâmetros genéticos para pesos corporais de caprinos Anglo Nubiano

Objetivou-se com este trabalho determinar o modelo mais adequado, bem como estimar os parâmetros genéticos do peso ao nascimento até os 196 dias de idade de caprinos da raça Anglo-nubiana. Os parâmetros genéticos foram estimados pelo método da máxima verossimilhança restrita (REML), utilizando o programa WOMBAT. Doze diferentes modelos animais foram ajustados por meio da inclusão ou exclusão do efeito genético materno, ambiente permanente materno, ambiente temporário materno e a covariância genética entre os efeitos direto e materno. Com base no critério de informação Bayesiano de Schwarz (BIC), o modelo II, que incluiu os efeitos genético direto e de ambiente temporário da mãe, foi o mais apropriado para todas as características. O efeito de ambiente temporário materno foi a mais importante fonte de variação. Este efeito contribuiu com 33% a 44% da variação fenotípica de acordo com o peso analisado. Estes resultados indicam que a seleção para efeitos direto e/ou materno em caprinos da raça Anglo-nubiana podem gerar progresso genético em características de crescimento.

Variance component analysis of body mass in a wild population of deer (Odocoileus virginianus): results from two decades of research

Context Long-term studies of large, vertebrate mammals using capture–recapture data are scarce, even though long-term ecological studies are requisite to understanding quantitative genetics and evolutionary processes that can be applied as part of management programs. Aims Objectives were to (1) partition components of variation in body mass to understand the differential effects of environmental variation on the sexes during ontogeny, to better prescribe habitat-improvement projects, and (2) estimate repeatability to assess potential for selection on body mass. Methods We used a 23-year dataset (1983–2005) of capture–recapture records of wild white-tailed deer (Odocoileus virginianus) to estimate components of variance and repeatability of body mass. We used an animal-model approach that employed the use of general linear mixed models and restricted maximum likelihood to adjust for the effects of age (i.e. fixed effect), and to partition the total phenotypic variance into among-individual (i.e. the deer), permanent environmental (i.e. year of birth) and temporary environmental (i.e. year of measurement and residual) effects (all modelled as random effects). Key results We found that body mass increased with age in both sexes, repeatability of body mass was 0.595 for females and 0.716 for males, and among-individual variation was more influential on body mass than were permanent and temporary environmental effects combined. Year of birth was more important in males than females, but changed during the course of ontogeny for both sexes. Year of measurement did not influence post-rut body mass in males, but did contribute to variation in body mass of females. Conclusions These long-term data offer insights into the sources of variation that influence body mass of deer, which can be used to understand how environmental sources of variation influence phenotypic traits, and for developing management plans and making selection decisions. Implications Knowledge of repeatability (as an upper limit to heritability) can be used to make management decisions related to selection, culling and breeding, whereas understanding environmental effects can lead to better management recommendations (e.g. habitat-improvement projects).

Effect of parentage misidentification on estimates of genetic parameters for milk yield in the Mediterranean Italian buffalo population

The objective of this study was to evaluate the effect of parentage misidentification on estimation of genetic parameters for the Italian buffalo population for milk yield from 45,194 lactation records of 23,104 Italian buffalo cows. Animals were grouped into 10 data sets in which sires and dams were DNA identified, or reported from the pedigree, or unknown. A derivative-free restricted maximum likelihood method was used to estimate components of variance with a repeatability model. The model contained age at calving nested within parity and days from calving to conception as linear covariates, herd-year-seasons as fixed effects, and additive genetic, permanent environmental, and temporary environmental effects as random effects. Estimates of heritability (±SE) ranged from 0.00±0.099 (sires and dams as reported in the pedigree) to 0.39±0.094 (sires DNA identified and dams as reported in the pedigree). When identification of sires was as reported in the pedigree, estimates of heritability were close to zero. These small estimates indicate that a large proportion of reported paternity is incorrect. When sires are unknown and dams are DNA identified, the proportion of variance due to sires seems to be captured in the estimate of permanent environmental variance as a fraction of phenotypic variance. Therefore, as heritability decreased, permanent environmental variance increased about the same amount. Data sets with dams identified from pedigree and sires DNA identified showed the largest estimate of heritability (0.39), which was essentially the same as when dams were DNA identified (0.38). This result supports that most dams are correctly reported from the pedigree. Genetic progress should be much greater with bulls DNA identified because of greater heritability, but without artificial insemination and progeny testing, progress would be slow and would depend mostly on selection of sires based on dam estimated breeding values. Implementation of artificial insemination programs and DNA testing to identify sires are the keys for increasing genetic progress in the Italian buffalo population.

Can number and size of offspring increase simultaneously? - a central life-history trade-off reconsidered

BackgroundTo maximize their fitness, parents are assumed to allocate their resources optimally between number and size of offspring. Although this fundamental life-history trade-off has been subject to long standing interest, its genetic basis, especially in wild mammals, still remains unresolved. One important reason for this problem is that a large multigenerational pedigree is required to conduct a reliable analysis of this trade-off.ResultsWe used the REML-animal model to estimate genetic parameters for litter size and individual birth size for a common Palearctic small mammal, the bank vole (Myodes glareolus). Even though a phenotypic trade-off between offspring number and size was evident, it was not explained by a genetic trade-off, but rather by negative correlations in permanent and temporary environmental effects. In fact, even positive genetic correlations were estimated between direct genetic effects for offspring number and size indicating that genetic variation in these two traits is not necessarily antagonistic in mammals.ConclusionsOur results have notable implications for the study of the life-history trade-off between offspring number and size in mammals. The estimated genetic correlations suggest that evolution of offspring number and size in polytocous mammals is not constrained by the trade-off caused by antagonistic selection responses per se, but rather by the opposing correlative selection responses in direct and maternal genetic effects for birth size.

Prediction of prion protein genotype and association of this genotype with lamb performance traits of Suffolk sheep1,2

The association of the prion protein (PrP) gene with susceptibility to scrapie has formed the basis of selection programs aimed at eradicating the disease from sheep populations. Animals are genotyped for the PrP gene and those with the less susceptible genotypes are selected. The objectives of this study were to determine the effectiveness of predicting PrP genotypes by using information from relatives and to investigate the association of the PrP genotype with lamb performance traits in Suffolk sheep. Data were obtained from a scrapie-affected flock maintained in Scotland. A total of 643 were animals genotyped at codon 171 of the PrP gene with 2 alleles, R and Q. The genotypes of these animals were used to predict the genotypes of 5,173 nongenotyped animals in the same flock using segregation analysis. The genotype of nongenotyped animals was predicted from the probabilities for each possible genotype; further, an overall index for each animal was calculated to reflect the accuracy of prediction. Association analyses of the PrP gene (using animals with both known and inferred genotypes) with BW at birth, at weaning (56 d), and at 150 d, and for backfat and muscle depths at 150 d of age were carried out. A linear mixed model with random direct and maternal additive genetic effects, maternal permanent and temporary environmental effects, and year of birth was tested, and the most appropriate model was used for each trait. The expected number of Q alleles carried (from 0 to 2) by each animal was calculated and used in the model as a linear and quadratic covariate to test for associations with possible additive and dominance PrP gene effects, respectively. Results showed that the genotypes of relatively few animals (235) were inferred with certainty (compared with the 5,173 nongenotyped animals). Approximately 25% of the 5,173 predicted genotypes were inferred with a genotype probability index of 50% and greater. There was no significant association of the PrP gene with any of the performance traits studied (there were no significant additive or dominance effects). Such was the case whether data on animals with known or with both known and predicted genotypes were considered. It can be concluded that selection for PrP-resistant alleles in Suffolk sheep is unlikely to affect performance directly.

Genetic parameters of lamb weights and ultrasonic muscle and fat depths in Beulah Specklefaced sheep

Genetic parameters for live weight at 8 weeks and day of scanning (mean age 151 days), ultrasonic muscle (UMD) and fat (UFD) depths were estimated using data from Beulah Specklefaced sheep in a sire reference scheme. Heritability estimates were 0.17, 0.16, 0.18 and 0.17 for eight week weight, scan weight, UMD and log 10 UFD, respectively, with corresponding estimates of maternal heritability of 0.05, 0.17, 0.07 and 0.18. Estimates of the proportion of phenotypic variance explained by permanent and temporary environmental effects for eight week weight were 0.17 and 0.14, respectively, and ranged between 0.04 and 0.08 for scan traits, with no significant ( P > 0.05) variance due to permanent environmental effects for log 10 UFD. Correlations between direct and maternal additive effects ranged between −0.54 and −0.80. Genetic correlations among scan traits were moderate (0.33–0.51) and estimates of maternal, permanent and temporary environmental correlations were not significantly different from one ( P > 0.05). These estimates generally support the structure of the selection index currently used in the Beulah breed; however, further information is required concerning the importance of the covariance between the direct and maternal additive effects.