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.     

Association of halothane sensitivity with growth and meat quality in pigs

Previous reports have indicated that a proportion of pigs, homozygous normal for the skeletal muscle ryanodine receptor gene (RYR1), was halothane sensitive, and this was associated with poor meat quality when pigs were handled aggressively. This study was conducted to evaluate halothane sensitivity in RYR1-normal pigs, managed under simulated commercial conditions, to ascertain the association of halothane sensitivity with growth rate and meat quality. A total of 363 pigs across four farrowing groups, from seven Landrace sires and 38 Yorkshire–Landrace F1 dams, were tested at 8 weeks of age for halothane sensitivity using a closed system that delivered 5% halothane at 2 l/min for 3 (group 1) or 2 (groups 2 to 4) min. After 1 min, limb rigidity, limb tremors and abdominal discoloration were evaluated on a binomial scale with 0 indicating no reaction and 1 indicating reaction. Testing was repeated 2 days later. At 10 weeks of age, pigs were moved to finishing pens and not moved again until marketing. Within farrowing group, pigs were harvested in one of two groups, and at marketing were moved a distance of 91 m, weighed, tattooed, loaded and transported a distance of 550 km to a commercial harvest plant. After overnight rest, pigs were harvested and the pH of the loin muscle was measured at 45 min (pH45) after stunning. After an 18-h chill, loin muscle pH (pHu), International Commission on Illumination (CIE) L*, a*, b*, color (1 to 6) and marbling (1 to 10) scores and fluid loss percent were collected. Generalized linear mixed models were used to estimate repeatabilities for response to halothane challenge. Repeatabilities for limb rigidity for the front right and left legs were 0.24 and 0.31, respectively, whereas rear right and left leg repeatabilities were 0.19 and 0.17, respectively. Repeatabilities for front right and left leg tremors were 0.16 and 0.20, respectively. Growth rate was not influenced by any measure of halothane sensitivity. Carcasses from pigs exhibiting limb rigidity tended to have lower pH45 (5.88 v. 5.97; P = 0.06), similar pHu (5.47 v. 5.49; P = 0.32), less pH decline from 45 min to 18 h (−0.40 v. −0.50; P = 0.04) and a tendency for greater fluid loss percent (5.01 v. 4.55; P = 0.08) than carcasses from pigs that did not exhibit limb rigidity during halothane challenge. A proportion of pigs normal for RYR1 did exhibit limb rigidity during halothane gas challenge, and subsequently tended to have lower 45 min pH and greater longissimus muscle fluid loss post harvest.     

Linkage of genes for PHI,halothane sensitivity,A-O inhibition,H red blood cell antigens and 6-PGD variants in pigs*

Data from one apparent crossover between S and H, two between PHI and HAL on one side and S on the other, and one between PHI on one side and HAL, S and H on the other, indicate a gene order in pigs of Phi-Hal-S-H-Pgd for genes for PHI, halothane sensitivity, inhibition of expression of A and O, H red blood cell antigens and 6-PGD types. Rasmusen et al. (1980) provided data for a gene order in pigs ofPhi-Hal-H-Pgd for genes for phosphohexose isomerase (PHI) isozyme variants, halothane sensitivity (HAL), H red cell antigens and 6-phosphogluconate dehydrogenase (6-PGD) variants, and suggested that there might be a locus for a gene for inhibition of expression of A and O separate from the locus for H. This is contrary to an earlier proposal by Rasmusen (1972) that the H-system genotype directly influences expression of A and O. Imlah (1980) suggested that the recessive gene for halothane sensitivity has a suppressant effect on the expression of A and O. Andresen (1981) proposed that the locus for inhibition of A and O (for which Rasmusen, 1964, proposed the symbol S) was between the loci for HAL and H types. Data presented in Table 1, which includes haplotypes for three recombinant offspring described by Rasmusen et al. (1980) (883-1, 233-3 and 3864-1) as well as one other recombinant (296-2) provide evidence for the gene order for five genes proposed by Andresen. Types for 6-PGD are listed for all pigs, although they do not provide evidence for gene order in these cases. Male 883-1 (Table 1, and Rasmusen et al., 1980, Table 5) provided the original evidence for recombination between S and H. His phenotype, as well as his genotype as revealed by progeny test (Rasmusen et al., 1980, Table 6) indicated that recombination had occurred between the genes for PHI, HAL and S and the gene for H type in his dam, so that the S locus mapped between H and the loci for the other three traits. The phenotype of one of his sons (233-3, Table 1, and Rasmusen et al., 1980, Table 6) indicated that there had been a recombination between genes for PHI and HAL types on one side and S and H types on the other, providing evidence that the S locus was separate from PHI and HAL as well as H. Another pig listed in Table 1,3864-1, was also described by Rasmusen et al. (1980, Table 9) as a recombinant. This pig provides evidence for recombination between PHI on one side and HAL, S and H on the other, establishing a gene order of Phi-Hal-S-H-Pgd. The last pig listed in Table 1,296-2, is a recombinant comparable to 233-3. The H type of his dam provides markers indicating the recombination was between PHI and HAL on one side and S and H on the other, although the unusual expression of HAL phenotype in both parents of 296-2 makes her haplotypes somewhat uncertain. (Recombination may have been between PHI and HAL rather than as indicated in Table 1.) In spite of incomplete penetrance for HAL (Ollivier et al., 1975; Smith & Bampton, 1977) which makes haplotypes for HAL questionable in some cases, the other genetic markers available are useful to show that recombination has taken place. Without considering the results of halothane testing, if the apparent recombinants are accepted as being as indicated, the order of the genes at the other four loci seems established. Alleles for S types appear to be separable by recombination from those for PHI and H, and the S locus appears to be between the loci for PHI and H. For the five loci, data obtained thus far are cohsistent with a gene order of Phi-Hal-S-H-Pgd.     

Associations between marker genotypes, halothane reaction, CC 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 Phi^A (0.48), H- (0.43) and Pgd^A (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 7% of animals with Phi^AIA, H^-I-, Pgd^A/A and Phi^A/B genotypes respectively 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 -^I- . 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.
It is concluded that in the German Landrace the marker loci Phi, Pgd and H could also be helpful in breeding homozygous halothane-negative pigs with distinctly better meat quality characteristics.     

Genetic parameters for tissue and fatty acid composition of backfat, perirenal fat and longissimus muscle in Large White and Landrace pigs

Genetic parameters pertaining to the same chemical characteristics of three porcine tissues, that is backfat (BF), perirenal fat (PF) and longissimus muscle (LM), were estimated in centrally tested Large White and Landrace pigs. Animals were fed ad libitum. They were slaughtered at an average BW of 99.6 kg, and samples of BF (both inner and outer layers) and LM were removed at the 13th to 14th rib level of the carcass on the day after slaughter. The data set included 2483 animals recorded for average daily gain (ADG; 35 to 100 kg), estimated carcass lean percentage (LEAN) and lean tissue growth rate (LTGR). Among these animals, around 950 pigs were recorded for lipid content (L%) and water content (W%) of BF and LM and for fatty acid composition (FAC) of BF, whereas FAC of LM was measured on 297 pigs and L%, W%, and FAC of PF on around 210 pigs. Heritabilities (h2) and genetic correlations (ra) were estimated using REML-animal model methodology. Estimates of h2 for L%, W% and FAC of BF, PF and LM were of moderate-to-high magnitude: for example 0.47 ± 0.09 for L% of LM, 0.59 ± 0.11 for W% of BF, 0.45 ± 0.08 for the ratio of polyunsaturated to saturated fatty acids (P/S) of BF, 0.61 ± 0.15 and 0.29 ± 0.10 for the coefficient of unsaturation of lipids (UNSAT, average number of double bonds of unsaturated fatty acids) of PF and LM, respectively. Genetic correlations of L% with P/S or UNSAT were strongly negative (from -0.4 to -0.9) in BF and LM, but not in PF. The 'between-tissue' genetic correlations for homologous compositional traits were far from being unity (e.g. ra = 0.57 ± 0.05 'between' BF and PF for UNSAT). Genetic relationships between ADG and tissue compositional traits were globally weak. By contrast, genetic correlations were moderate-to-high between carcass leanness and tissue compositional traits, especially those of fat depots: for example -0.66 ± 0.14 between LEAN and L% of BF, 0.50 ± 0.07 between LEAN and UNSAT of PF, -0.44 ± 0.08 between LEAN and L% of LM, and 0.27 ± 0.03 between LEAN and UNSAT of LM. On the basis of the parameter estimates found here, breeding for higher LTGR is expected to increase the ratio of water to lipids and the unsaturation degree of lipids in subcutaneous BF and, to a lesser extent, in PF. Tissue composition and FAC of LM would be less affected.     

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.     

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.     

Malic enzyme 1 genotype is associated with backfat thickness and meat quality traits in pigs

Malic enzyme 1 (ME1) is a part of the tricarboxylate shuttle that provides NADPH and acetyl-CoA required in fatty acid biosynthesis. The pig ME1 locus maps on the proximal end of chromosome 1, where a quantitative trait loci (QTL) affecting fat deposition has been previously described. We amplified fragments of 1457 and 1459 bp that corresponded to the complete coding region and the 3'-untranslated region (UTR), respectively, of the pig ME1 gene. The sequences of these two fragments in pigs from three breeds (Landrace, Large White and Piétrain) contained five single nucleotide polymorphisms (SNP) in the 3'-UTR: C1706T, G1762T, A1807C, C1857A and T1880A. Three haplotypes were found in two generations of a selected Landrace population: H1 (C1706 G1762 A1807 C1857 A1880), H2 (C1706 G1762 A1807 C1857 T1880) and H3 (T1706 T1762 C1807 A1857 T1880). Using Bayesian association analyses, significant associations (highest posterior density at 95%) between ME1 genotype and backfat (BF) thickness at 171 days and muscular pH were found in a Landrace population.     

Genome‐wide association study identifies quantitative trait loci affecting hematological traits in an F2 intercross between Landrace and Korean native pigs

Changes affecting the status of health and robustness can bring about physiological alterations including hematological parameters in swine. To identify quantitative trait loci (QTL) associated with eight hematological traits (one leukocyte trait, six erythrocyte traits and one platelet trait), we conducted a genome‐wide association study using the PorcineSNP60K BeadChip in a resource population derived from an intercross between Landrace and Korean native pigs. A total of 36 740 SNPs from 816 F₂ progeny were analyzed for each blood‐related trait after filtering for quality control. Data were analyzed by the genome‐wide rapid association using mixed model and regression (GRAMMAR) approach. A total of 257 significant SNPs (P < 1.36 × 10^?6) on SSC3, 6, 8, 13 and 17 were identified for blood‐related traits in this study. Interestingly, the genomic region between 17.9 and 130 Mb on SSC8 was found to be significantly associated with red blood cell, mean corpuscular volume and mean corpuscular hemoglobin. Our results include the identification of five significant SNPs within five candidate genes (KIT, IL15, TXK, ARAP2 and ERG) for hematopoiesis. Further validation of these identified SNPs could give valuable information for understanding the variation of hematological traits in pigs.     

Absence of detectable linkage between the G and H blood group loci in the pig

Morton's lod score method used for the analysis of data from 168 backcross matings (1094 offspring) did not indicate linkage between the G and H blood group loci of the pig. Linkage closer than 0.413 could be excluded at the 1% significance level.     

Halothane sensitivity and linkage of genes for H red blood cell antigens,phosphohexose isomerase (PHI) and 6-phosphogluconate dehydrogenase (6-PGD) variants in pigs*

Data from matings appropriate to test linkage in pigs of genes for halothane sensitivity (HAL), H red cell antigens, phosphohexose isomerase (PHI) and 6-phosphogluconate dehydrogenase (6-PGD) red cell isoenzyme variants were consistent with a gene order of Phi-Hal-H-Pgd. There was no unequivocal evidence for a Hal locus separate from Phi, although the phenotype of one pig not tested for halothane sensitivity suggested recombination between Hal and Phi. Breeding tests confirmed that in two cases there had been recombination between Hal and H. Offspring of one of these recombinant types provided evidence for a locus for a gene for inhibition of expression of A and O separate from the locus for H.     

Associations between blood groups, blood protein polymorphisms and breeding values for production traits in Swedish Red and White Dairy bulls

The relationships of nine blood group systems and two blood protein polymorphisms with breeding values for several production traits were examined in dairy cattle of the Swedish Red and White (SRB) breed. The material consisted of 2212 bulls; the bulls were performance tested for growth rate and their breeding values for milk yield, fat and protein content in milk were estimated from progeny tests. The direct effect of marker alleles or marker phenotypes was analysed in a multiple regression model. Several significant associations were found; many supported earlier findings. However, the contribution of the markers to the total variation of the breeding values was very small. Linkage between marker loci and production loci was studied in offspring from heterozygous sires by estimating the interactions between sire and marker alle using a model eliminating the direct effects of sire and marker alle. There were strong indications of linkage between some marker loci (e.g. B, J and Am-1 loci) and loci with large effects on production traits.     

Health and immune traits of Basque and Large White pigs housed in a conventional or enriched environment

Since decades, production traits such as growth rate, feed efficiency or body composition have been drastically increased in pigs by genetic selection. Whether this selection impacted animal robustness is still unclear. In this study, we compared Large White (LW) pigs, a breed submitted to intense genetic selection for production traits, and Basque (B) pigs, a local rustic breed, reared in two different housing environments (conventional v. enriched). Adaptation to housing conditions among each breed was evaluated at the level of endocrine and immune traits. These are known to be impacted by housing conditions and breed; however, the interaction effects between genotype and environment are less described. Animals (20 per breed and housing environment) entered the experiment at 35 kg of live weight. Levels of cortisol, acute-phase inflammatory proteins, immunoglobulins and hydrogen peroxide, blood formula, lymphocyte proliferation and in-vitro cytokine expression were measured at ∼115 kg of live weight. Animals were checked for skin injuries during the growing period. At slaughter, at the average live weight of 145 kg, carcasses were examined for pathological conditions of the respiratory tract. The major result was that the two breeds exhibited differences in response to the housing environment. Among the 24 sanitary, endocrine or immune traits investigated, the housing conditions affected eight variables in both breeds (salivary cortisol at 0700 and 1900 h, severity of pneumonia at slaughter) or only in B pigs (severe skin lesions) or LW pigs (salivary cortisol at 1500 h, granulocyte numbers and lymphocyte/granulocyte ratio and lymphocyte proliferation). These observations strengthen the hypothesis that selection for high meat production level might be associated with an increased susceptibility of animals to environmental stressors.     

Impact of the ESR gene on litter size and production traits in Czech Large White pigs

To evaluate the effect of the PvuII polymorphism of the oestrogen receptor gene on litter size and production traits in Czech Large White swine, data from 1250 sows and 3600 litters were analysed with two four-trait animal models. The traits in the first model were number of piglets born alive in a sow's first litter, number of piglets born alive in second and subsequent litters, lifetime daily gain and lean meat percentage. The second model included number of piglets born, number of piglets born alive, number of piglets weaned and litter weight at weaning from first and subsequent litters. The oestrogen receptor (ESR) locus significantly affected prolicacy in the first parity and averaged over all parities (P < 0.05), with allele A superior to allele B. In the first parity, AA sows produced approximately 0.5 more live piglets per litter than BB sows. Averaged over all parities, this difference was c. 0.25 piglets. Results for total number of piglets born and number of piglets weaned were similar to results for numbers born alive. No significant dominance effect was found for prolificacy traits. For litter weight at weaning, no significant additive effect was observed at the ESR locus, but a significant negative dominance effect (-1.5 kg) was estimated averaged across parities (litters of AB sows were similar to litters of BB sows for this trait). No pleiotropic effect of the ESR polymorphism on average daily gain or lean meat percentage was found.     

QTL analysis of white blood cell, platelet and red blood cell-related traits in an F2 intercross between Landrace and Korean native pigs

Haematological traits play important roles in disease resistance and defence functions. The objective of this study was to locate quantitative trait loci (QTL) and the associated positional candidate genes influencing haematological traits in an F₂ intercross between Landrace and Korean native pigs. Eight blood‐related traits (six erythrocyte traits, one leucocyte trait and one platelet trait) were measured in 816 F₂ progeny. All experimental animals were genotyped with 173 informative microsatellite markers located throughout the pig genome. We report that nine chromosomes harboured QTL for the baseline blood parameters: genomic regions on SSC 1, 4, 5, 6, 8, 9, 11, 13 and 17. Eight of twenty identified QTL reached genome‐wide significance. In addition, we evaluated the KIT locus, an obvious candidate gene locus affecting variation in blood‐related traits. Using dense single nucleotide polymorphism marker data on SSC 8 and the marker‐assisted association test, the strong association of the KIT locus with blood phenotypes was confirmed. In conclusion, our study identified both previously reported and novel QTL affecting baseline haematological parameters in pigs. Additionally, the positional candidate genes identified here could play an important role in elucidating the genetic architecture of haematological phenotype variation in swine and in humans.     

Evaluation of linkage between the R-O-i and C blood group systems in sheep

Linkage between the C and I blood group loci in sheep was demonstrated by lod score analysis of data from double backcross matings. The recombination frequency between the I locus and the gene coding for the Cb red cell antigen was estimated to be 0.09 with a standard error of 0.04.     

Genetic parameters of a random regression model for daily feed intake of performance tested French Landrace and Large White growing pigs

Daily feed intake data of 1 279 French Landrace (FL, 1 039 boars and 240 castrates) and 2 417 Large White (LW, 2 032 boars and 385 castrates) growing pigs were recorded with electronic feed dispensers in three French central testing stations from 1992–1994. Male (35 to 95 kg live body weight) or castrated (100 kg live body weight) group housed, ad libitum fed pigs were performance tested. A quadratic polynomial in days on test with fixed regressions for sex and batch, random regressions for additive genetic, pen, litter and individual permanent environmental effects was used, with two different models for the residual variance: constant in model 1 and modelled with a quadratic polynomial depending on the day on test d_m as follows in model 2: . Variance components were estimated from weekly means of daily feed intake by means of a Bayesian analysis using Gibbs sampling. Posterior means of (co)variances were calculated using 800 000 samples from four chains (200 000 each). Heritability estimates of regression coefficients were 0.30 (FL model 1), 0.21 (FL model 2), 0.14 (LW1) and 0.14 (LW2) for the intercept, 0.04 (FL1), 0.04 (FL2), 0.11 (LW1) and 0.06 (LW2) for the linear, 0.03 (FL1), 0.04 (FL2) 0.11 (LW1) and 0.06 (LW2) for the quadratic term. Heritability estimates for weekly means of daily feed intake were the lowest in week 4 (FL1: 0.11, FL2: 0.11) and week 1 (LW1: 0.09, LW2: 0.10), and the highest in week 11 (FL1: 0.25, FL2: 0.24) and week 8 (LW1: 0.19, LW2: 0.18), respectively. Genetic eigenfunctions revealed that altering the shape of the feed intake curve by selection is difficult.