Associations between marker genotypes, halothane reaction, creatine kinase activity and meat quality characters in a sample of German Landrace pigs

Routine blood typing of German Landrace pedigree populations and an earlier study revealed very low frequencies of the favourable alleles at the marker loci Phi, Pgd and H. The hypothesis was that in this population the whole linkage group of favourable alleles at the halothane and neighbouring marker loci may have been lost as a consequence of intense selection for leanness and type. The present study of 1050 German Landrace pigs at the Relliehausen experimental station, where some effort has been made to maintain a higher frequency of the favourable alleles PhiA (0.48), H- (0.43) and PgdA (0.70) gave quite different results. The frequency of halothane-positive pigs found by using a severe test was only 30%. Only 5.4%, 8.8%, 13.4% and 13.9% of animals with PhiA/A, H-/-, PgdA/A and PhiA/B genotypes respecitively were halothane-positive. Forty to sixty per cent of pigs with these marker genotypes could therefore be expected to be homozygous halothane-negative (N/N) animals. Creatine kinase activity and three selected meat quality characters showed highly significant differences between the A/A and the B/B genotypes for the marker loci Phi and Pgd, with the heterozygotes being intermediate. These differences are greater than those observed between halothane-negative and halothane-positive phenotypes. The only other consistently superior marker genotype in this population was the H blood group genotype H-/-. In contrast to findings from Sweden and Switzerland, the postalbumin locus Po2 and the suppressor locus S for the A-O blood groups did not exhibit useful marker qualities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gene order and recombination rates in the linkage group S-Phi-Hal-H-(Po2)-Pgd in pigs

Families of Czech Landrace (94 litters and 636 offspring) were tested for halothane sensitivity, A-O (S), H, PHI and PGD phenotypes. Informative matings for the estimation of recombination rates between marker loci were selected. The following recombination frequencies were established: S-Phi = 4.8 % (2.5 % -10.7 %);S-H = 6.8 % (4.3 %-11.7 %); Phi-H = 2.6 % (0.9 %-5.3 9%); H-Pgd = 4.4 % (1.6 %-8.0 %). CCCC-overs were observed also between S- Hal, Hal-H andHal - Pgd, but were not found between Phi - Hal. On the basis of these results it has been possible to revise the position of the S locus in this linkage group. The most probable gene order would be: S - Phi - Hal (or Hal - Phi) -H- (P02) - Pgd.
A striking difference was found between the number of halothane-sensitive pigs (87) and HalⁿHal ⁿ genotypes determined by haplotyping (123). Segregation rates in 19 backcross matings and experimental matings of the animals proved that this difference is mostly due to incomplete CCC or low expression of halothane sensitivity.     

Genetic variation at a pig serum protein locus, Po-2 and its assignment to the Phi, Hal, S, H, Pgd linkage group

Two-dimensional agarose gel (pH 5.4)-polyacrylamide gel (pH 9.0) electropho-resis of pig serum samples revealed a new serum protein (postalbumin-2, PO-2) polymorphism. Family data supported the hypothesis that the three PO-2 phenotypes observed were controlled by two codominant, autosomal alleles ( Po-2^F and Po-2^S ) at a single locus. The frequency of Po-2^F in Swedish Landrace and in Swedish Yorkshire breeds was estimated at 0.74 and 0.65, respectively. Evidence was presented for close genetic linkage between Po-2 and the red cell phospho-hexose isomerase locus ( Phi ). A recombination frequency of 3.2 % was obtained from double backcross material. Data obtained in a Danish Landrace material showing linkage between the Po-2 locus and the H blood group locus, the Pgd locus and Hal (locus for halothane sensitivity) are also given. A total of seven re-combinants were observed. They show that Po-2 is a new locus in a previously established linkage group. The likely sequence of the loci is: Phi, Hal, S, H, Po-2, Pgd .     

Localization of the Po2 locus in the S, Phi, Hal, H, Po2, Pgd linkage group in pigs

The localization of the Po2 locus controlling a polymorphic serum postalbumin was studied in 41 families of the Czech Landrace breed. The haplotypes involving six closely linked loci (S, Phi, Hal, H, Po2, Pgd) were determined for each family member. The crossovers observed between the H, Po2 and Pgd loci indicated that Po2 is located between H and Pgd. The Po2 locus appears to be closer to H [theta = 0.54% (0.06%-1.92%)] than to Pgd [theta = 4.02% (1.67%-7.96%)]. A strong Ha-Po2S association (r = 0.96, P less than 0.001) and H-PO2 linkage disequilibrium (D = 0.2218, P less than 0.01, D/DMax = 0.98) were found.     

Trends in economic traits, halothane sensitivity, blood group and enzyme systems of Swiss Landrace and Large White pigs

Pigs deriving from 150 breeding centres constituting a representative section of elite breeding herds (2496 Swiss Landrace pigs, 587 Swiss Large White pigs) were subjected to blood typing during the period 1981 to 1984. Production traits such as daily gain, feed conversion ratio, lean meat content and meat quality score were available to show the trend in these performance traits since 1978. Field data on the halothane reaction of 14 270 Swiss Landrace (SL) pigs were used to assess the porcine stress syndrome during the period 1978–1983.
In SL pigs the frequency of the alleles H^a, Phi^B and Ada^A decreased significantly, and that of the H^c and Phi^A increased during the period of the study. The frequency of the H^a allele dropped from 0.36 in 1981 to 0.20 in 1984, whereas the H^c allele rose from 0.22 to 0.37. In Swiss Large White (SLW) pigs, on the other hand, the frequency of the H^a allele increased constantly from 0.31 to 0.37 during this period.
An initial frequency of 17.7 % (1978) halothane reactors in SL pigs was lowered to 0.7 % (1982) after five years of halothane testing.
In SL pigs the meat quality scores improved regularly, whereas in SLW pigs it did not change very much. The percentage of PSE animals in the SL breed was reduced from 32.7 % in 1978 to 7.1 % in 1983.
Because the Hal locus is associated with production traits such as meat quality, linkage disequilibria could explain the observed associations between the H and Phi types and production traits.     

Blood group association with severity and speed of the halothane reaction1

The second generation (n= 227) of British Landrace pigs from selected halothane-positive parents (36 litters) were blood-typed for the S(A-0), H and Phi loci and subjected to four 5-minute halothane tests at 21, 35, 49 and 63 days of age. Cumulative scores based on seventy and speed of reaction were analysed in relation to single-locus blood group genotypes and linkage group sequences at two and three loci. A highly significant negative correlation (r = -0.79) was found between severity and speed of reaction. Significant differences occurred between blood group genotypes and linkage groups in both severity and speed of reaction. Genotypes S s/s, H a/a or H a/- and Phi B/B and linkage groups involving these three types had the highest cumulative reaction score and the fastest reaction time, whereas genotypes Phi A/B, S S/S or S S/s and H a/cd and linkage groups with these types had the Iowest and slowest reaction scores. Some differences between genotypes and linkage groups were attributed to phenotypically halothane-positive parents and offspring being genotypically Hal N/n. These effects could result from linkage with heterozygous types such as H a/cd and S S/s. The possible role of the H ^cd allele acting as a genetic marker for a suppressor gene to the halothane reaction is discussed.     

Blood group association with severity and speed of the halothane reaction

The second generation (n = 227) of British Landrace pigs from selected halothane-positive parents (36 litters) were blood-typed for the S(A-O), H and Phi loci and subjected to four 5-minute halothane tests at 21, 35, 49 and 63 days of age. Cumulative scores based on severity and speed of reaction were analysed in relation to single-locus blood group genotypes and linkage group sequences at two and three loci. A highly significant negative correlation (r = -0.79) was found between severity and speed of reaction. Significant differences occurred between blood group genotypes and linkage groups in both severity and speed of reaction. Genotypes S s/s, H a/a or H a/- and Phi B/B and linkage groups involving these three types had the highest cumulative reaction score and the fastest reaction time, whereas genotypes Phi A/B, S S/S or S S/s and H a/cd and linkage groups with these types had the lowest and slowest reaction scores. Some differences between genotypes and linkage groups were attributed to phenotypically halothane-positive parents and offspring being genotypically Hal N/n. These effects could result from linkage with heterozygous types such as H a/cd and S S/s. The possible role of the H cd allele acting as a genetic marker for a suppressor gene to the halothane reaction is discussed.     

The position of the epistatic S locus in the halothane linkage group in pigs

The linkage of the Phi, Pgd, Po2, S, H and halothane sensitivity loci was followed in a Belgian Landrace family, heterozygous for these systems over 6 generations. Recombination next to the S locus occurred mainly in pigs belonging to this particular family. From this investigation the position of the S locus is proved to be outwith the Phi-Pgd region, next to Phi . Therefore the gene sequence S - Phi - Hal -H- Po2 -Pgd is proposed. Higher recombination rates were observed in the female parental line of the multiheterozygous family when compared to the male parental line. Additional data from animals, unrelated to this strain, confirm the evidence of close linkage of the S system to the nearest marker loci.     

Gene order and recombination rates in the linkage group S-Phi-Hal-H-(Po2)-Pgd in pigs

Families of Czech Landrace (94 litters and 636 offspring) were tested for halothane sensitivity, A-O (S), H, PHI and PGD phenotypes. Informative matings for the estimation of recombination rates between marker loci were selected. The following recombination frequencies were established: S - Phi = 4.8% (2.5%-10.7%); S - H = 6.8% (4.3%-11.7%); Phi - H = 2.6% (0.9%-5.3%); H - Pgd = 4.4% (1.6%-8.0%). Cross-overs were observed also between S - Hal, Hal - H and Hal - Pgd, but were not found between Phi - Hal. On the basis of these results it has been possible to revise the position of the S locus in this linkage group. The most probable gene order would be: S - Phi - Hal (or Hal - Phi) - H - (Po2) - Pgd. A striking difference was found between the number of halothane-sensitive pigs (87) and HalnHaln genotypes determined by haplotyping (123). Segregation rates in 19 backcross matings and experimental matings of the animals proved that this difference is mostly due to incomplete penetrance or low expression of halothane sensitivity.     

The position of the epistatic S locus in the halothane linkage group in pigs

The linkage of the Phi, Pgd, Po2, S, H and halothane sensitivity loci was followed in a Belgian Landrace family, heterozygous for these systems over 6 generations. Recombination next to the S locus occurred mainly in pigs belonging to this particular family. From this investigation the position of the S locus is proved to be outwith the Phi-Pgd region, next to Phi. Therefore the gene sequence S - Phi - Hal - H - Po2 - Pgd is proposed. Higher recombination rates were observed in the female parental line of the multiheterozygous family when compared to the male parental line. Additional data from animals, unrelated to this strain, confirm the evidence of close linkage of the S system to the nearest marker loci.     

Prediction of the halothane (Hal) genotypes of pigs by deducing Hal, Phi, Po2, Pgd haplotypes of parents and offspring: results from a large-scale practice in Swedish breeds

Results from a large-scale study, comprising 75 different breeding herds, are reported on predicting the halothane (Hal) genotypes of individual pigs by making use of the known close linkage between Hal and three electrophoretic blood marker loci (Phi, Po2, Pgd). The parents haplotypes (involving Hal and marker loci) were determined from the HAL phenotypes (halothane test results) and marker loci phenotypes of their offspring in the first one or two litters studied. In subsequent litters of the Hal-marker loci haplotyped parents, the offspring's expected Hal genotypes could be predicted on the basis of the marker loci haplotypes inherited by them. By comparing the expected and observed HAL phenotypes of offspring in subsequent litters, the predicted Hal genotype was found to be correct in 90-95% of the 4000 offspring (from Nn X Nn and Nn X nn matings) of Swedish Landrace and Yorkshire breeds studied. The order of the three marker loci was confirmed as Phi-Po2-Pgd but the position of Hal with regards to Phi could not be resolved. The recombination frequencies between the most distant loci in this region, viz. Hal-Pgd and Phi-Pgd, were estimated to be 3-4.5% and 4-6%, respectively. The easy and rapid electrophoretic techniques described in the study to phenotype PHI, PO2, PGD, also allowed phenotyping of six other polymorphic protein systems on the same gels. Thus Hal genotyping and effective parentage control can be conducted simultaneously.     

Prediction of the halothane (Hal) genotypes of pigs by deducing Hal, Phi, Po2, Pgd haplotypes of parents and offspring: results from a large-scale practice in Swedish breeds

Results from a large-scale study, comprising 75 different breeding herds, are reported on predicting the halothane ( Hal ) genotypes of individual pigs by making use of the known close linkage between Hal and three C blood marker loci ( Phi, Po2, Pgd ). The parents haplotypes (involving Hal and marker loci) were determined from the HAL phenotypes (halothane test results) and marker loci phenotypes of their offspring in the first one or two litters studied. In subsequent litters of the Hal -marker loci haplotyped parents, the offspring's expected Hal genotypes could be predicted on the basis of the marker loci haplotypes inherited by them. By comparing the expected and observed HAL phenotypes of offspring in subsequent litters, the predicted Hal genotype was found to be correct in 90–95 % of the 4000 offspring (from Nn × Nn and Nn × nn matings) of Swedish Landrace and Yorkshire breeds studied.
The order of the three marker loci was confirmed as Phi-Po2-Pgd but the position of Hal with regards to Phi could not be resolved. The recombination frequencies between the most distant loci in this region, viz. Hal-Pgd and Phi-Pgd , were estimated to be 3–4.5 % and 4–6 % , respectively. The easy and rapid electrophoretic techniques described in the study to phenotype PHI, PO2, PGD, also allowed phe-notyping of six other polymorphic protein systems on the same gels. Thus Hal genotyping and effective parentage control can be conducted simultaneously.     

Genetic variation at a pig serum protein locus, Po-2 and its assignment to the Phi, Hal, S, H, Pgd linkage group

Two-dimensional agarose gel (pH 5.4)-polyacrylamide gel (pH 9.0) electrophoresis of pig serum samples revealed a new serum protein (postalbumin-2, PO-2) polymorphism. Family data supported the hypothesis that the three PO-2 phenotypes observed were controlled by two codominant, autosomal alleles (Po-2F and Po-2s) at a single locus. The frequency of Po-2F in Swedish Landrace and in Swedish Yorkshire breeds was estimated at 0.74 and 0.65, respectively. Evidence was presented for close genetic linkage between Po-2 and the red cell phosphohexose isomerase locus (Phi). A recombination frequency of 3.2% was obtained from double backcross material. Data obtained in a Danish Landrace material showing linkage between the Po-2 locus and the H blood group locus, the Pgd locus and Hal (locus for halothane sensitivity) are also given. A total of seven recombinants were observed. They show that Po-2 is a new locus in a previously established linkage group. The likely sequence of the loci is: Phi, Hal, S, H, Po-2, Pgd.     

Relationships between blood groups, isozymes and halothane reaction in pigs from a selection experiment

German Landrace pigs (n = 1500) were halothane-tested and blood samples were taken for the determination of A-O and H blood types as well as for the determination of PHI and 6-PGD isozymes. The pigs originated from two generations (7th and 8th) of a selection experiment 'selection for activity of NADPH-generating enzymes in backfat of pigs'. The selection lines are E-, E+ (selection for low and high enzyme activity), U- (selection for low ultrasonic backfat thickness) and K (control). Preliminary results show an average proportion of halothane-susceptible animals of 49%. The frequencies of halothane-positive pigs amount to 60%, 46%, 70% and 30% in lines E-, E+, U- and K, respectively. The investigation shows a non-random combination of the marker genes caused by linkage disequilibrium, especially in line E-. Recombination frequencies between the loci vary from 0% to 18%.     

Further contribution to the H blood group system in pigs

The haemolytic reagent allowing direct serological detection of He homozygous pigs was obtained by the immunization of a Landrace sow. Another monospecific reagent prepared from immune serum of a Miniature pig made possible the evidence for a new factor of the H system - He. This factor is genetically controlled by the allele H ^be. Its frequency in Miniature pigs was 0.099.
The H system with alleles H ¹=H^a, H²= H^b, H³= H^ab, H⁴=H^cd, H⁵= H^bd, H⁶=H^be and H⁷= H- continues to be a genetically open system.     

H blood group genotypes and expression of A and 0 antigens in pigs

Tests of over 2000 pigs, with the blood group reagents Ac, Ap and 0, and the reagents Ha, Hb, He, Hd, He and Hc/c, confirmed that the H locus affects the expression of A and 0 antigens. The 'exceptional' phenotypes Ap and — were found in Ha homozygotes of Miniature pigs and in Hcd homozygotes of a semi-inbred Landrace line. They were also found in unrelated pigs of other breeds, and moreover in some individuals with genotypes H ^a H ^cd, H ^ab H ^cd, H-H- and H ^a H ^ab or H ^ab H ^ab.
The mechanism of the effect of the H locus on the A phenotypes may consist in the interaction of certain, not yet completely defined, H genotypes, or in linkage of the H system with the hypothetical ' S ' locus.     

The blood group factor Kf and allele Kae in the pig

By means of alloimmune reagents used in the indirect Coombs test and the dextran test a new factor Kf in the K bloodgroup system of pigs was found, controlled by alleles K ^acf, K ^acef and K ^bf. A new allele K ^ae was also detected.
The K system with 6 alleles, 11 phenotypes and 21 combinations of genotypes remains (from the genetic point of view) an open system.     

Relationships between blood groups,isozymes and halothane reaction in pigs from a selection experiment1

German Landrace pigs (n= 1500) were halothane-tested and blood samples were taken for the determination of A-O and H blood types as well as for the determination of PHI and 6-PGD isozymes. The pigs originated from two generations (7th and 8th) of a selection experiment ‘selection for activity of NADPH-generating enzymes in backfat of pigs’. The selection lines are E^-, E⁺ (selection for low and high enzyme activity), U^- (selection for low ultrasonic backfat thickness) and K (control). Preliminary results show an average proportion of halothane-susceptible animals of 49 %. The frequencies of halothane-positive pigs amount to 60 %, 46 %, 70 % and 30 % in lines E^-, E⁺, U- and K, respectively. The investigation shows a non-random combination of the marker genes caused by linkage disequilibrium, especially in line E^-. Recombination frequencies between the loci vary from 0 % to 18 %.     

Trends in economic traits, halothane sensitivity, blood group and enzyme systems of Swiss Landrace and Large White pigs

Pigs deriving from 150 breeding centres constituting a representative section of elite breeding herds (2496 Swiss Landrace pigs, 587 Swiss Large White pigs) were subjected to blood typing during the period 1981 to 1984. Production traits such as daily gain, feed conversion ratio, lean meat content and meat quality score were available to show the trend in these performance traits since 1978. Field data on the halothane reaction of 14 270 Swiss Landrace (SL) pigs were used to assess the porcine stress syndrome during the period 1978-1983. In SL pigs the frequency of the alleles Ha, PhiB and AdaA decreased significantly, and that of the Hc and PhiA increased during the period of the study. The frequency of the Ha allele dropped from 0.36 in 1981 to 0.20 in 1984, whereas the Hc allele rose from 0.22 to 0.37. In Swiss Large White (SLW) pigs, on the other hand, the frequency of the Ha allele increased constantly from 0.31 to 0.37 during this period. An initial frequency of 17.7% (1978) halothane reactors in SL pigs was lowered to 0.7% (1982) after five years of halothane testing. In SL pigs the meat quality scores improved regularly, whereas in SLW pigs it did not change very much. The percentage of PSE animals in the SL breed was reduced from 32.7% in 1978 to 7.1% in 1983. Because the Hal locus is associated with production traits such as meat quality, linkage disequilibria could explain the observed associations between the H and Phi types and production traits.     

Linkage studies between the halothane (Hal), phosphohexose isomerase (Phi) and the S(A -O) and H red blood cell loci of Pietrain/ Hampshire and Landrace pigs

Frequency of blood group factors at the A-O and H loci were markedly altered within halothane positive (HP) and halothane negative (HN) composite synthetic Pietrain/Hampshire lines (PTH) over four generations of selection.
Linkage studies on the litters from 45 double backcross and 20 mixed and intercross matings, involving the S(A-O), H, Phi and Hal loci, were made in the PTH line and halothane positive and negative selected British Landrace lines. Crossing-over frequencies of 0.05 ± 0.04, 0.05 ± 0.03 and 0.1 ± 0.03 were established between Phi and Hal, H and Hal , and Phi and H respectively. An unequal crossing-over frequency between Phi and H was found when the alleles Ha and Hcd were compared. The difference in recombination frequency between the Ha and Hcd alleles amounted to 0.04 to 0.06.
No cross-overs were observed between the S(A -O ) and Phi, H or Hal loci in 15 families studied. The position of the S locus in relation to the other loci could not be established, but statistical evidence of association favours a haplotype sequence of Phi-Hal-S-H .