Paternal Half-sib Groups Research Articles

Influence of Sires on Population Substructure in Dülmen Wild Horses.

The objectives of the present study were to analyze the influence of the stallions employed in the Dülmen wild horses on the genetic diversity and population substructure using Bayesian cluster analysis. The Dülmen wild horse is maintained as a unique horse population exposed to the natural conditions all year round in the Merfelder Bruch near Dülmen in Westphalia, Germany. Stallions selected for breeding have to prove their abilities to survive under this harsh environment. We used multilocus genotypic information from a set of 29 autosomal microsatellites to determine the paternity of 185 male foals sired by nine stallions. As females could not be sampled, we could not make inferences on all yearlings and test whether there are differences in the genetic population parameters between both sexes. The mean number of progeny was 19.92 with a range of 2-32, caused by the length of the service period per stallion. The average observed and unbiased expected heterozygosity was 0.688 and 0.631, the mean number of alleles was 4.448, and Wright's FIS was -0.173. Pairwise genetic distances (FST and Nei's unbiased genetic distances) were significant and varied between 0.038 to 0.091 and 0.085 to 0.290, respectively. Neighbor-joining dendrogram plots clustered a large proportion of the paternal progeny groups in different branches. Posterior Bayesian analyses using seven paternal half-sib groups with 10-74 members supported a maximum of six clusters, with two paternal progeny groups not differing, and a median of five clusters, with two groups of two sires each falling into the same clusters. When sires were employed in non-consecutive years, progeny from these different years of the same sires were grouped in the same cluster, whereas the progeny of one sire from two consecutive years were in different clusters. We were able to distinguish male progeny from Dülmen wild horse stallions and to show the effects of stallion use on the genetic substructure in the Dülmen wild horse herd. In conclusion, the analyses showed the genetic potential of the Dülmen wild horse stallions to maintain a high genetic diversity and also the effects in which breeding seasons and for how long stallions are used to sire foals. The selection of stallions may be sensitive for the further development of genetic diversity and preserve this closed population as a valuable resource for further studies on the evolution of the horse.

Exploring underlying drivers of genotype by environment interactions in feed efficiency traits for dairy cattle with a mechanistic model involving energy acquisition and allocation

Feed efficiency (FE) is a complex phenotype made up of multiple traits for which there is potential for substantial genotype by environment interaction (G × E). The objective of this study is to evaluate the extent of G × E for FE traits with a simulation approach. We used a mechanistic model of the dairy cow that simulates trajectories of phenotypes throughout lifetime, depending on trajectories of resource acquisition and allocation, driven by 4 genetic scaling parameters, and depending on the nutritional environment (quantity and quality of feed resources). The cow model, calibrated for a grass-based farming system and seasonal calving, was combined with a genetic module. This simulated genetic variation in the 4 genetic scaling parameters related to resource acquisition and allocation, based on a simple balanced pedigree structure (200 paternal half-sib groups each of 100 daughters). The population of 20,000 cows generated was simulated in 4 nutritional environment scenarios, representing a gradient of feeding constraints. In each scenario, 6 traits derived from the model outputs were analyzed to obtain population genetic parameters. Genetic correlations between second-lactation production and FE were positive and high in all scenarios and increased as the nutritional environment became more constraining. A measure of lifetime FE was positively correlated with second-lactation production under a less constrained environment, but these correlations decreased as the environment became more constraining. The genetic correlation between body reserves at second calving, and lifetime FE was positive and low in the least constraining scenario and increased as the environment became more constraining. In addition to genetic parameters, we looked at the distributions of acquisition and allocation parameters among the best performing cows for lactation and life FE, in the 2 most contrasted scenarios. The 4 subpopulations of best cows had acquisition and allocation strategies different from the whole population. In conclusion, this simulation study identifies the potential underlying biological basis for important G × E in FE traits. This highlights the importance of having a balanced breeding goal when undertaking selection that should also be based on phenotypes relevant to the target performance environment.

Imputation of ungenotyped parental genotypes in dairy and beef cattle from progeny genotypes

The objective of this study was to quantify the accuracy of imputing the genotype of parents using information on the genotype of their progeny and a family-based and population-based imputation algorithm. Two separate data sets were used, one containing both dairy and beef animals (n=3122) with high-density genotypes (735 151 single nucleotide polymorphisms (SNPs)) and the other containing just dairy animals (n=5489) with medium-density genotypes (51 602 SNPs). Imputation accuracy of three different genotype density panels were evaluated representing low (i.e. 6501 SNPs), medium and high density. The full genotypes of sires with genotyped half-sib progeny were masked and subsequently imputed. Genotyped half-sib progeny group sizes were altered from 4 up to 12 and the impact on imputation accuracy was quantified. Up to 157 and 258 sires were used to test the accuracy of imputation in the dairy plus beef data set and the dairy-only data set, respectively. The efficiency and accuracy of imputation was quantified as the proportion of genotypes that could not be imputed, and as both the genotype concordance rate and allele concordance rate. The median proportion of genotypes per animal that could not be imputed in the imputation process decreased as the number of genotyped half-sib progeny increased; values for the medium-density panel ranged from a median of 0.015 with a half-sib progeny group size of 4 to a median of 0.0014 to 0.0015 with a half-sib progeny group size of 8. The accuracy of imputation across different paternal half-sib progeny group sizes was similar in both data sets. Concordance rates increased considerably as the number of genotyped half-sib progeny increased from four (mean animal allele concordance rate of 0.94 in both data sets for the medium-density genotype panel) to five (mean animal allele concordance rate of 0.96 in both data sets for the medium-density genotype panel) after which it was relatively stable up to a half-sib progeny group size of eight. In the data set with dairy-only animals, sufficient sires with paternal half-sib progeny groups up to 12 were available and the within-animal mean genotype concordance rates continued to increase up to this group size. The accuracy of imputation was worst for the low-density genotypes, especially with smaller half-sib progeny group sizes but the difference in imputation accuracy between density panels diminished as progeny group size increased; the difference between high and medium-density genotype panels was relatively small across all half-sib progeny group sizes. Where biological material or genotypes are not available on individual animals, at least five progeny can be genotyped (on either a medium or high-density genotyping platform) and the parental alleles imputed with, on average, ⩾96% accuracy.

Co-segregation of quantitative trait loci (QTL) for milk production traits and length of productive life with QTL for left-sided displacement of the abomasum in German Holstein dairy cows

Left-sided displacement of the abomasum (LDA) is a commonly observed disease in Holstein dairy cows, previously shown to be genetically correlated with milk performance traits and length of productive life (LPL). The objective of this study was to detect joint quantitative trait loci (QTL) among milk production traits and LDA using a paternal half-sib design including only LDA affected daughters. Joint QTL for LDA and milk production traits in LDA-affected daughters may indicate genetic correlations among these traits due to linkage disequilibrium or even pleiotropic genes. We genotyped 14 paternal half-sib groups including 328 LDA affected daughters and eight sires for 302 microsatellites. Linkage analyses were performed for milk performance traits, somatic cell score (SCS), and LPL. In total, we identified seven genome-wide and further 30 chromosome-wide significant QTL for milk performance traits, SCS, and LPL. All four QTL for LPL, two of the QTL for fat yield, and one QTL for protein percentage overlapped with QTL identified for LDA and twelve further ones overlapped with or were adjacent to family-dependent QTL for LDA. Furthermore, polymorphisms located within the DGAT1 and ABCG2 genes, which were previously reported to be associated with milk performance traits were analysed for all cows. The DGAT1 SNP was associated with milk yield, fat yield, fat percentage, and protein percentage, but showed no association with LDA, while the ABCG2 SNP was monomorphic. We can conclude that genetic correlations among LDA and LPL may arise from these joint QTL. Therefore, selection for longevity should even lower LDA incidence in German Holsteins. A lower co-incidence for LDA-QTL locations was found for fat yield and protein percentage. This study is a step towards better understanding of genetic correlations of LDA with milk performance traits and identification of possible side-effects due to selection for milk production in dairy cows.

Estimation of genetic parameters and breeding values in shrimp Fenneropenaeus chinensis using the REML/BLUP procedure

An analysis of a selection experiment was used to assess the impact of various animal model structures on REML estimates of variance components. The analyses were carried out based on 162 d body mass (BM) of 1 287 animals from 21 paternal half-sib groups of Fenneropenaeus chinensis. Estimated breeding values (EBV) of BM of all individuals were estimated using eight statistical models (A, AB, ABC, ABDC, ABMFC, ABMDC, ABFDC and ABMFDC) and BLUP (best linear unbiased prediction). These models were designed involving factors such as sex, spawn date as fixed effects, maternal genetic effects, full-sib family effects as random effects, mean BM of families at tagging and age at recording (covariate). The results demonstrate the importance of correct interpretation of effects in the data set, particularly those that can influence resemblance between relatives. The data structure and the particular model that was applied markedly influenced the magnitude of variance component estimates. Models based on few effects obtained upward biased estimates of additive genetic variance. The accuracy of genetic parameters and breeding value estimated by ABFDC model was higher than other models. The results imply that additive genetic direct value, full-sib family effects, and covariance effects besides sex and spawn date as fixed effects were very important for estimating genetic parameters and breeding value of body mass. This model had a heritability estimate of 162 d BM of 0.44. The comparison of the efficiency of selection based on breeding values or phenotypic value revealed great difference: average breeding value of the best 24 families selected by the 162 d BM breeding value and phenotype were 0.577 g and 0.366 g, respectively, representing a 36.57% higher efficiency in the former. In conclusion, selection based on breeding value was more effective than selection based on phenotypic value. Our results indicate that effects influencing the magnitude of estimates should be taken into account when estimating heritability and breeding values for BM.

Fine mapping of a quantitative trait locus for osteochondrosis on horse chromosome 2

In this study, we refine a quantitative trait locus for equine osteochondrosis (OC) on horse chromosome (ECA) 2 to a genome-wide significant interval at 20.08-30.94 Mb. The marker set contained 27 newly developed microsatellites equidistantly distributed over ECA2 and 44 nucleotide polymorphisms, located in 16 positional candidate genes for OC. Genotyping was performed in 211 Hanoverian horses from 14 paternal half-sib groups. A NCDN-associated SNP and haplotype were significantly associated with OC in fetlock and/or hock joints. This study is a further step towards the identification of genes responsible for OC in horses.

Refinement of quantitative trait loci on equine chromosome 10 for radiological signs of navicular disease in Hanoverian warmblood horses

Navicular disease is characterized by a progressive degenerative alteration of the equine podotrochlea. In this study, we refined a previously identified quantitative trait locus (QTL) on horse chromosome 10 for the abnormal development of canales sesamoidales (DCS) of the navicular bone in Hanoverian warmblood horses. Genotyping was done in 192 Hanoverian warmblood horses from 17 paternal half-sib groups. The whole marker set comprised 45 markers including seven newly developed microsatellites and 13 single nucleotide polymorphisms (SNPs) within positional candidate genes. Chromosome-wide significant QTL were confirmed and refined for DCS on horse chromosome (ECA) 10 at 0.16-2.70 Mb and at 14.45-36.37 Mb. Nine microsatellites and three SNP markers reached the highest multipoint Zmeans and LOD scores at 19.34-20.38 Mb and at 23.17-30.73 Mb with genome-wide error probabilities of P<0.05. In addition, a significant association of a SNP within VSTM1 and a significant haplotype-trait association within IRF3 could be shown. These results support a possible role of the candidate genes VSTM1 and IRF3 within the QTL on ECA10 for DCS. This study is a further step towards the identification of the genes responsible for navicular disease in Hanoverian warmblood horses.

Refinement of a quantitative trait locus on equine chromosome 5 responsible for fetlock osteochondrosis in Hanoverian warmblood horses

In this report, we provide 29 new informative microsatellites distributed over a region of 21 Mb on horse chromosome (ECA) 5 and refine a quantitative trait locus (QTL) for fetlock osteochondrosis dissecans (OCD) to a genome-wide significant interval between 78.03 and 90.23 Mb on ECA5. Genotyping was performed in 211 Hanoverian warmblood horses from 14 paternal half-sib groups. Within this OCD-QTL, collagen type XXIV alpha 1 was identified as a potential functional candidate gene for equine osteochondrosis. This report is a further step towards unravelling the genes that cause equine osteochondrosis.

Fine mapping a quantitative trait locus on horse chromosome 2 associated with radiological signs of navicular disease in Hanoverian warmblood horses

Navicular disease or podotrochlosis is one of the main causes of progressive forelimb lameness in warmblood horses. The objective of this study was to refine a quantitative trait locus on horse chromosome 2 for radiological alterations in the contour of the navicular bone (RAC) in Hanoverian warmblood horses. Genotyping was performed in 192 Hanoverian warmblood horses from 17 paternal half-sib groups. The marker set was extended to 58 informative microsatellites including nine newly developed microsatellites. QTL for RAC could be delineated at 32.50-43.13 Mb and a further new QTL for RAC could be identified at 59.08-65.14 Mb. The markers ABGe342 and ABGe343 reached the highest multipoint Z(mean) and LOD scores at 34.42 and 35.23 Mb with genome-wide error probabilities of P = 0.013 and P = 0.064. In addition, significant associations of markers and haplotypes within the QTL could be shown. The results support the location of the QTL on ECA2 associated with RAC. This work is a further step towards the development of a marker test for navicular disease in Hanoverian warmblood horses.

Refinement of a quantitative gene locus on equine chromosome 16 responsible for osteochondrosis in Hanoverian warmblood horses

Osteochondrosis (OC) is an inherited developmental disease in young horses most frequently observed in thoroughbreds, trotters, warmblood and coldblood horses. Quantitative trait loci (QTL) for equine OC have been identified in Hanoverian warmblood horses employing a whole genome scan with microsatellites. A QTL on ECA16 reached the genome-wide significance level for hock osteochondrosis dissecans (OCD). The aim of this study was to refine this QTL on ECA16 using an extended marker set of 34 newly developed microsatellites and 15 single nucleotide polymorphisms (SNPs). We used the same 14 paternal half-sib groups as in the above-mentioned whole genome scan. The QTL for OCD in hock joints on ECA16 could be delimited at an interval between 17.60 and 45.18 Mb using multipoint non-parametric linkage analyses. In addition, six microsatellites and one SNP were significantly associated with hock OCD in the QTL region between 24.26 and 42.41 Mb. Furthermore, our analysis revealed a second QTL for fetlock OC between 6.55 and 24.26 Mb on ECA16. This report is a further step towards unravelling the genes underlying QTL for equine OC and towards the development of a marker test for OC in Hanoverian warmblood horses.

Genetic analysis of insect bite hypersensitivity (summer eczema) in Icelandic horses

There is a lack of knowledge about the genetic background of eczema due to insect bite hypersensitivity, also called summer eczema, in horses. The condition is known in several horse breeds and countries and it causes reduced welfare of the horse and economic losses to the owner. The aim of this study was to estimate genetic parameters for summer eczema in Swedish-born Icelandic horses. A questionnaire was sent to owners of horses sired by stallions with more than 50 offspring born in Sweden between 1991 and 2001. Variance components of summer eczema classified as healthy, mild, moderate or severe were estimated using the threshold methodology with sire models. In addition, summer eczema was analysed as a binary trait (healthy v. affected). The analyses included 1250 horses sired by 33 stallions. The prevalence of summer eczema was 8%, with a range of 0% to 30% in different paternal half-sib groups. Offspring of dams suffering from eczema had a higher risk of developing eczema. The heritability for severity of summer eczema was estimated at 0.3 (s.d. < 0.2) with a threshold sire model. In contrast to the age of the horse, different geographic areas and gender were significantly associated with severity of the eczema. We conclude that genetic selection could decrease the prevalence of summer eczema among Swedish-born Icelandic horses. The amount and quality of data are, however, crucial for the possibility to introduce a genetic evaluation of summer eczema. The symptoms should be classified in several classes according to severity, and this classification could be made by the horse owner.

Genome-wide search for microsatellite markers associated with radiologic alterations in the navicular bone of Hanoverian warmblood horses

The aim of this study was to identify quantitative trait loci (QTLs) for pathologic changes in the navicular bone in Hanoverian warmblood horses. Seventeen paternal half-sib groups comprising 192 individuals were analyzed in a whole-genome scan. These families included 144 progeny and grandchildren, which were randomly chosen from the Hanoverian warmblood. Three different traits were considered: deformed canales sesamoidales and radiographic changes in the contour and in the structure of the navicular bone. The genome scan included in total 214 highly polymorphic microsatellite markers. The putatively linked genomic regions on equine chromosomes (ECA) 2, 3, 10, and 15 were refined using 53 additional microsatellites. Chromosome-wide significant QTLs were located on five different equine chromosomes (ECA2, 3, 4, 10, and 26). Genome-wide significant QTLs were on ECA2 at 48 cM and on ECA10 from 45.5 to 49.8 cM. This study was a first step to get more insight into the molecular genetic determination of radiologic changes in the equine navicular bone.

Natural selection on floral traits of female Silene dioica by a sexually transmitted disease

Floral traits endowing high reproductive fitness can also affect the probability of plants contracting sexually transmitted diseases. We explore how variations in floral traits influence the fitness of Silene dioica females in their interactions with pollinators carrying pollen or spores of the sterilizing anther-smut fungus Microbotryum violaceum. We collected healthy and infected plants in a highly diseased population and grew them under conditions that 'cure' infected individuals, and used standard regression methods to detect natural selection on floral traits. Narrow-sense heritabilities, coefficients of additive genetic variation (CV(A)) and genetic correlations among traits were estimated from paternal half-sib groups. Pollinator preferences imposed strong direct and directional selection on traits affecting female attractiveness and pollen-/spore-capturing abilities. Levels of additive genetic variance were high in these traits, suggesting that rapid responses to selection are possible. By considering our results in the light of spatial and temporal heterogeneity resulting from the colonization dynamics typical for this species, we suggest that the conflicting selective effects of pollen/spore loads lead to the maintenance of genetic variation in these traits.

Sex ratio distortion in bovine sperm correlates to recombination in the pseudoautosomal region.

A total of 2122 single sperm from 35 bulls belonging to six different paternal half-sib groups were analysed with respect to two markers in the bovine pseudoautosomal region (PAR) and sex-specific loci on the X and Y chromosomes, respectively. A segregation ratio significantly different from 1:1 was observed in a test over all families, with a higher proportion of X-bearing gametes (53.5%). The analysis of recombination conducted separately for X- and Y-bearing sperm showed that X-bearing sperm cells possess highly significant individual and between-family variability in recombination rate, whereas Y-bearing sperm show linkage homogeneity. To test whether the two phenomena are related, different logistic regression models were fitted to the data. The results show that sex ratio significantly correlates with changes in recombination rate among X-bearing but not among Y-bearing sperm. Different hypotheses to explain these observations are discussed.

Genetic variation in lytic activities of blood serum from Nile tilapia and genetic associations with survival and body weight

A study was carried out on lysozyme activity and spontaneous haemolytic (SH) activity of blood serum from 388 individuals of Nile tilapia ( Oreochromis niloticus) coming from 42 full-sib groups within 21 paternal half-sib groups. The lysozyme activity was measured at both 15°C and 30°C incubation temperatures, whereas SH activity was measured at 30°C incubation temperature. Significant variation in lysozyme activity was detected between half-sib groups at 30°C incubation temperature, but not at 15°C incubation temperature and not for SH activity. Significant variation was found between full-sib groups for all parameters. The estimated heritabilities of lysozyme activity were relatively high (0.6–0.7) at 30°C incubation temperature and intermediate (about 0.3) at 15°C incubation temperature. The heritability estimate of SH activity was zero according to estimates based both on the sire component of variance and on variance components from an individual animal model, whereas the estimate based on the dam component of variance was about 0.7 and highly significant. Survival and growth were recorded after a grow-out period of 120 days in individuals from a parallel set of samples from the same sib families. Significant negative correlations were found between least-squares means in the parallel sib groups for lysozyme activity and survival rates for both half-sib groups ( r=−0.53; P=0.01) and full-sib groups ( r=−0.32; P=0.04). No significant correlations were found between SH activity and survival rate nor between lytic activities and body weight at harvest.

Nonadditive genetic effects and inbreeding depression for body weight in Atlantic salmon ( Salmo salar L.)

For four sub-populations of Atlantic salmon ( Salmo salar) in Norway, additive, dominance and additive by additive genetic variances and inbreeding depression were estimated for body weight at slaughter after two years in sea-water. The data used were from a hierarchical mating design, in which each sire was mated with two to seven dams. In each generation, 104 to 206 full-sib groups and 18 to 110 paternal half-sib groups were produced. Data from each sub-population covered three successive generations with pedigrees traced one generation further back to the base population. In the four sub-populations, the number of fish recorded ranged from 51 969 to 62 162 offsprings of 96 to 187 sires and 386 to 525 dams. A sire–dam model was applied separately to each of the sub-populations. In addition to the random additive, dominance and additive by additive genetic effects, the model also included the random environmental effect common to members of a full-sib group, a covariate of body weight on inbreeding coefficient, and a fixed subclass effect of year by farm by cage by sex. Variance components were estimated using an algorithm based on the tilde-hat approximation to REML with solutions for random effects obtained by iteration on data. In each of the four sub-populations, dominance and additive by additive genetic variances were at least equal to the additive genetic variance in magnitude. In every case, the inclusion of nonadditive genetic effects in the model lead to a 50 to 79% decline in the estimates of additive genetic variances, while reductions in the error variances were negligible. Estimates of common environmental effects ranged from 4 to 6% of the total phenotypic variance. Estimated inbreeding depression in the analysed data sets ranged from 0.6 to 2.6% per 10% increase in inbreeding coefficient.

Evidence for individual and between-family variability of the recombination rate in cattle.

We have conducted a study based on single sperm typing in a family design to assess patterns of variability of the male recombination rate in cattle. 2214 sperm of 37 bulls were typed for 11 loci on bovine Chromosomes (Chrs) 6, 23, and the sex chromosomes. Statistically significant individual variability of the recombination rate was observed for one interval in the pseudoautosomal region (PAR) of the bovine sex chromosomes; one marker interval on bovine Chr 23 exhibited individual variability that was close to significance. Thirty-five of the bulls were members of six paternal halfsib groups, and highly significant variability between families was found for one interval in the PAR. This variability may be due to DNA sequence differences in the PAR or to a genetic control of the recombination activity in this region. It is demonstrated that differences in the recombination rate of the magnitude observed in the present study may have a considerable impact on the power of QTL mapping experiments as well as on the sustainability of marker-assisted selection strategies.

Antibody response in Atlantic salmon ( Salmo salar) against Vibrio anguillarum and Vibrio salmonicida O-antigens: Heritabilities, genetic correlations and correlations with survival

Genetic variation in antibody response to Vibrio anguillarum and V. salmonicida O-antigens was analysed in serum samples from Atlantic salmon ( Salmo salar) immunised twice with V. salmonicida. Antibody production against V. anguillarum was expected as a response to naturally occurring bacteria in the environment. The material consisted of 1200 fish from 57 full-sib groups within 20 paternal half-sib groups and serum was sampled three times. The estimated heritabilities for antibody concentration at different samplings ranged from 0.0–0.10 with standard errors from 0.03 to 0.21. Variance estimates for common' full-sib effects due to factors other than additive gene effects were low (0.1). The genetic correlations between antibody concentration and body weight tended to be negative at the first sampling (prior to immunisation) and positive at the third sampling (6 weeks after second immunisation). The genetic correlations between antibody response to the two antigens were positive at the first sampling and tended to be negative at the third sampling. Survival during commercial rearing in sea water was recorded for full-sibs reared in a field test. The variation in survival of offspring from different sires was significant. There was a significant positive correlation between the mean survival rate of the half-sib groups in the field test and mean antibody concentration against both V. salmonicida and V. anguillarum O-antigens of half-sib groups sampled prior to immunisation.

Genetic variation in the humoral immune response against Vibrio salmonicida and in antibody titre against Vibrio anguillarum and total IgM in Atlantic salmon ( Salmo salar)

Total IgM level and antibody titre to Vibrio anguillarum O-antigen after bath-vaccination, and specific antibody response to V. salmonicida O-antigen at three different samplings were analysed in family material of Atlantic salmon ( Salmo salar), consisting of 791 fish belonging to 34 maternal full-sib groups within 12 paternal half-sib groups. The fish were immunized twice, and blood samples collected three times. After the third blood sampling, the fish were challenged with V. anguillarum. Medium to low genetic variation was recorded in total IgM and in the antibody titres against V. anguillarum O-antigen and V. salmonicida O-antigen, with heritability estimates of 0.12, 0.18 and from 0.03 to 0.12, respectively. Moderate to high genetic and phenotypic correlations were found between the V. salmonicida O-antigen titres at different samplings. Genetic and phenotypic correlations between the initial titres were moderate to low. The effect of different immune traits, including Aeromonas salmonicida A-layer titres (previously described), on the ability to survive the challenge was examined. The likelihood of surviving the challenge was affected positively by the A. salmonicida A-layer titre at the second sampling, and almost significantly affected by the initial V. anguillarum O-antigen titre. Production traits, such as mean slaughter weight and mean proportion of survivors in a corresponding full-sib material, were obtained in the sea-rearing period. No significant full-sib correlation between immune parameters and production traits was detected.

A note on genetic correlations between pubertal traits of males or females and lifetime pregnancy rate in beef cattle

Genetic correlations were estimated between pubertal traits of males or females and yearling or lifetime pregnancy rate (PR) in beef cows, using 269 paternal half-sib groups. Lifetime PR was recorded from up to 5 mating/calving years for each cow. The genetic correlations between age at first oestrus (AFO) or standardised age at first oestrus (SFO) and yearling PR were −0.30 ± 0.26 and −0.67 ± 0.44, whilst corresponding estimates with lifetime PR were −0.29 ± 0.26 and −0.76 ± 0.68. For scrotal circumference (SC), genetic correlation estimates with yearling PR were 0.53 ± 0.66 and with lifetime PR 0.34 ± 0.40. The data generally supported the concept of a favourable genetic correlation between pubertal traits (higher SC or lower AFO and SFO) and lifetime PR.