Estimation of variance components for postpartum dysgalactia syndrome in sows.

The postpartum dysgalactia syndrome (PDS) represents one of the most important diseases after parturition in sows. The genetic background of the disease has been investigated some time ago and heritability estimates around 0.10 have been obtained. To compute current estimates, a dataset of 1680 sampled sows and their 2001 clinically examined litters was used for variance components estimation with a threshold liability model. Affected sows were defined through clinical examination 12-48 h after parturition. Posterior mean of additive genetic variance was 0.10 and estimated heritability for PDS averaged 0.0879 with a 95% confidence interval of 0.0876 and 0.0881. The results are in agreement with those of other studies and emphasize the importance of considering the genetic predisposition for susceptibility to PDS as well as of additional factors including hygiene and management conditions.

Pigs' aggressive temperament affects pre-slaughter mixing aggression, stress and meat quality.

Pre-slaughter stress has a negative impact on animal welfare and on meat quality. Aggressive behaviour when pigs are mixed together for transportation to, or on arrival at, the abattoir is an important factor in pre-slaughter stress. Aggressiveness of pigs varies between individuals in the population, and this study investigated its effects on stress and meat quality at slaughter. We mixed pigs at a young age to identify individuals of high (H) or low (L) aggressive temperament using the previously validated approach of lesion scoring. To contrast extremes of social stress single-sex groups of eight pigs were mixed according to their aggressiveness in HH, HL or LL combinations or left unmixed (U) prior to transport and slaughter (n = 271). Each treatment was replicated in at least two groups in each of four slaughter batches. Mixing per se had little effect, but mixed groups composed of aggressive pigs (HH) had more carcass skin lesions and higher levels of plasma cortisol at slaughter and had loin muscle samples with higher pH at 24 h, and lower redness (a*) and yellowness (b*) compared to the other treatments. Females had higher levels of plasma cortisol at slaughter, a more rapid decline in pH post-slaughter and greater lean content of meat. Lactate and creatine kinase (CK) levels and meat pH were affected by the interaction of sex and treatment. Genetic factors, dam and sire line composition, and halothane locus (ryanodine receptor 1, RYR1) genotype, also affected a number of production and meat quality parameters as expected. Additionally, 'commercially normal' levels of social stress were studied in four further slaughter batches with no manipulation of group composition (n = 313). In these pigs, the proportion of unfamiliar pigs and group size of lairage groups explained limited variation in lesion scores at slaughter, but earlier aggressiveness did not. High numbers of skin lesions on the carcass were associated with high levels of cortisol and lactate and low glucose at slaughter, but not with meat quality measures. When stress and meat quality measures were compared for all pigs, high lactate was associated with low early pH and high drip loss, while high cortisol and CK were associated with high pH at 24 h and changes in meat colour. In conclusion, mixing pigs of above average aggressiveness resulted in greater aggression and stress, and changes in meat quality parameters, consistent with the effects of pre-slaughter stress on muscle chemistry.

Associations of DNA markers with meat quality traits in pigs with emphasis on drip loss.

Phenotypic information on 1155 market pigs for several pig meat quality traits, was collected. Genotypes on 12 DNA markers, including RYR1 and PRKAG3 I199V, were also obtained on all pigs to investigate the relationship between genetic markers and meat quality. The RYR1 gene had the highest impact on meat quality, however, several other markers showed significant effects on one or more traits. Animals heterozygous at the RYR1 locus were significantly inferior in almost all meat quality traits, except ultimate pH value, initial conductivity and redness of the meat. Drip loss from case-ready meat (measured from 1 to 7 days post-mortem) was 43% higher for heterozygotes than animals of the stress resistant genotype. The homozygous genotype II at position I199V of the PRKAG3 locus also resulted in less drip loss than genotypes IV and VV, regardless of the method and time of measurement. Furthermore, the favourable genotype related to higher ultimate pH and darker meat. Both loci significantly affected the intercept, linear and quadratic terms of fitted drip loss development curves. The favourable genotypes showed a lower drip loss after one day of measurement and a slower increase and a more linear development over time. Whilst the RYR1 and PRKAG3 markers influenced numerous meat quality traits, some of the other markers were also found to have significant effects on one or two meat quality traits. Markers at MC4R and HMGA1 loci significantly affected drip loss, whereas LDHA, CAST (Hpy188I) and ATP2A1 influenced pH value. In addition, the marker ATP2A1 was associated with variation in intramuscular fat content in M. longissimus dorsi. GLUT4 affected temperature 45min post-mortem and several markers (MC4R, LDHA, GLUT4, HMGA1, CAST (Hpy188I and PvuII)) influenced one or two of the different colour measurements. The markers at MC4R, CKM, AGRP, PRKAG3, and HMGA1 loci were tested for their interactions with RYR1 regarding drip loss. Only AGRP showed a significant interaction, but this was based on only a few animals with the homozygous genotype for one allele. Our results suggest that genetic markers provide a useful tool to improve meat quality in pigs independently from RYR1, especially the mutation I199V in the PRKAG3 gene.

Quantitative trait loci associated with AutoFOM grading characteristics, carcass cuts and chemical body composition during growth of Sus scrofa.

A three-generation full-sib resource family was constructed by crossing two commercial pig lines. Genotypes for 37 molecular markers covering chromosomes SSC1, SSC6, SSC7 and SSC13 were obtained for 315 F2 animals of 49 families and their parents and grandparents. Phenotypic records of traits including carcass characteristics measured by the AutoFOM grading system, dissected carcass cuts and meat quality characteristics were recorded at 140 kg slaughter weight. Furthermore, phenotypic records on live animals were obtained for chemical composition of the empty body, protein and lipid accretion (determined by the deuterium dilution technique), daily gain and feed intake during the course of growth from 30 to 140 kg body weight. Quantitative trait loci (QTL) detection was conducted using least-squares regression interval mapping. Highest significance at the 0.1% chromosome-wise level was obtained for five QTL: AutoFOM belly weight on SSC1; ham lean-meat weight, percentage of fat of primal cuts and daily feed intake between 60 and 90 kg live weight on SSC6; and loin lean-meat weight on SSC13. QTL affecting daily gain and protein accretion were found on SSC1 in the same region. QTL for protein and lipid content of empty body at 60 kg liveweight were located close to the ryanodine receptor 1 (RYR1) locus on SSC6. On SSC13, significant QTL for protein accretion and feed conversion ratio were detected during growth from 60 to 90 kg. In general, additive genetic effects of alleles originating from the Piétrain line were associated with lower fatness and larger muscularity as well as lower daily gain and lower protein accretion rates. Most of the QTL for carcass characteristics were found on SSC6 and were estimated after adjustment for the RYR1 gene. QTL for carcass traits, fatness and growth on SSC7 reported in the literature, mainly detected in crosses of commercial lines x obese breeds, were not obtained in the present study using crosses of only commercial lines, suggesting that these QTL are not segregating in the analysed commercial lines.

Association between body composition of growing pigs determined by magnetic resonance imaging, deuterium dilution technique, and chemical analysis.

Development of body composition of 440 growing pigs from a three generation full-sib design to identify quantitative trait loci (QTL) was determined by three different methods. Firstly, the non-invasive method deuterium dilution technique (DT), was applied to all pigs in the experiment at six weights 20, 30, 60, 90, 120 and 140kg. Secondly, at each weight class, eight pigs were slaughtered and their entire body chemically analysed (CA). Thirdly, magnetic resonance imaging (MRI) was applied on 16 live pigs at different weights. For the entire empty body (without content of the gastrointestinal tract and bladder), allometric prediction equations to predict body composition from empty body water content measured by DT were derived from chemically analysed serial slaughtered pigs. These equations showed high correlations of 0.92, 0.90 and 0.85 for the contents of body water, fat-free substance as well as protein in fat-free substance, respectively. For the soft tissue (empty body without bones and viscera), allometric prediction equation of body composition based on DT and CA showed correlations of 0.91, 0.88 and 0.82 for water content, fat-free substance, and protein content of fat free substance, respectively. Fat tissue content, fat tissue mass, and lean tissue mass measured by MRI showed allometric relationships to lipid content, lipid mass, and protein mass determined by DT with correlations of 0.98, 0.87, and 0.98, respectively. Lean (measured by MRI) and protein (determined by DT) content of soft tissue was best fitted by a linear-quadratic polynomial and resulted in a correlation of 0.86. Allometric coefficients for change of percentages of chemical components, water (b=-0.036) and protein (b=0.106) in fat-free substance of empty body during growth were similar to those in the literature indicating the consistency of accretion rates of chemical components of the fat-free substance in different studies. Means for protein- and lipid-deposition rates (determined by DT) as well as lean tissue- and fat tissue-deposition rates (measured by MRI) ranged from 95 to 154, 147 to 328, 373 to 420 and 129 to 254g in the different weight ranges. Variation between animals in protein (lean tissue) and lipid (fat tissue) deposition rate was large which can be exploited in order to identify QTL of these traits.

Drip loss of case-ready meat and of premium cuts and their associations with earlier measured sample drip loss, meat quality and carcass traits in pigs.

Drip loss of 374 samples taken from porcine M. longissimus dorsi and M. semimembranosus was measured by using the "bag method" (BM), EZ-DripLoss (EZ-DL) from premium cuts (PC) and in retail tray (case-ready meat; CRM). This provided a comparison between these methods and their relationships to other meat quality and carcass traits. Samples were prepared at 24h post-mortem (pm) and were measured 24 and 48h after preparation (at 48 and 72h pm) using the BM and after 48h (at 72h pm) with the EZ-DL and PC. Drip loss of meat kept in retail trays was measured after 7 days (CRM(7)) and daily within a week (CRM(1-7)). Average drip loss was 1.80% and 3.10% using the BM after 24 and 48h, respectively. EZ-DL and CRM(7) showed higher drip losses of 4.71% and 4.00%. Daily loss of CRM(1-7) showed a concavely shaped curve and increased from 1.57% to 5.64% after 7 days. High correlations were obtained between drip loss of CRM(7) and BM (r=0.88) or the EZ-DL (r=0.91). The development of drip loss in case-ready meat fitted by linear-quadratic regression (y=0.439+1.245x-0.072x(2)) showed that high drip loss measured earlier by bag and EZ-DripLoss methods was highly associated with a high intercept (r=0.63-0.72), a high linear increase (r=0.77-0.81), but larger decrease in increments (r=-0.82 to -0.86) during weekly stored meat in retail trays as supplied at consumer level. Because the positive linear regression coefficient was substantially higher than the negative quadratic regression coefficient, the development of drip loss is mainly dependent on the initial drip loss. Therefore, animals with high drip loss within 72h post-mortem also showed undesirable high drip loss curves over the entire retail period. Relationships between drip loss and other meat quality traits were similar for BM, EZ-DL and CRM(7). Of these the correlation between pH(24) and drip loss was highest with r=-0.54, -0.49 and -0.47 for BM, EZ-DL and CRMH(7), respectively. Interestingly, a correlation of r=-0.35 between blood pH value and CRML(7) was obtained. Carcass traits such as loin, ham, shoulder, belly weight or loin eye area showed only marginal correlations to drip loss. In conclusion, EZ-DL was the most appropriate method to predict drip loss of case-ready meat in retail trays and its development during a 7 day storage period.

Comparison of different methods for determination of drip loss and their relationships to meat quality and carcass characteristics in pigs.

Samples of the M. longissimus dorsi of 776 pigs from three commercial lines were used to compare two methods for measuring drip loss, referred to as the EZ-DripLoss and bag methods. Furthermore, relationships between drip loss and other meat quality and carcass traits were analysed. The bag method used a slice of M. longissimus dorsi of approximately 120 g hung in an airtight container whereas the EZ-DripLoss method used two samples of approximately 10 g placed in drip loss containers. In the bag method, samples taken at 24 h post-mortem were measured 24 and 48 h after sampling and average drip loss was 1.94% and 3.33% at 24 and 48 h, respectively. Correlation between these consecutive measurements was high (r=0.98). Using the EZ-DripLoss method, drip loss of samples taken at 24 h post-mortem was measured 48 h after sampling and showed an average value of 4.97%. Correlation between the drip loss obtained using EZ-DripLoss and bag methods was high (r=0.86). Relationships between drip loss and other meat quality traits were similar for both methods. Highest correlations were observed between drip loss and pH(45) (r=-0.52 and -0.48 using EZ-DripLoss method(48) and bag method(48), respectively) and the lowest to Minolta a (∗) value (r=0.11 and 0.09, respectively). Correlations among several carcass traits, such as lean content, and drip loss were low or not significant. Low associations between loin eye area (cm(2)) and drip loss were obtained regardless of the method used to determine drip loss (r=0.21 and 0.18 using EZ-DripLoss method(48) and bag method(48), respectively). For routine measurements, the EZ-DripLoss method is recommended because it showed a high correlation with the bag method but is easier to perform and is more standardised.

The Belt mutation in pigs is an allele at the Dominant white (I/KIT) locus.

A white belt is a common coat color phenotype in pigs and is determined by a dominant allele (Be). Here we present the result of a genome scan performed using a Hampshire (Belt)/Pietrain (non-Belt) backcross segregating for the white belt trait. We demonstrate that Belt maps to the centromeric region of pig Chromosome (Chr) 8 harboring the Dominant white (I/KIT) locus. Complete cosegregation between Belt and a single nucleotide polymorphism in the KIT gene was observed. Another potential candidate gene, the endothelin receptor type A gene (EDNRA), was excluded as it was assigned to a different region (SSC8q21) by FISH analysis. We argue that Belt is a regulatory KIT mutation on the basis of comparative data on mouse KIT mutants and our previous sequence analysis of the KIT coding sequence from a Hampshire pig. Quantitative PCR analysis revealed that Belt is not associated with a KIT duplication, as is the case for the Patch and Dominant white alleles. Thus, Belt is a fourth allele at the Dominant white locus, and we suggest that it is denoted I(Be).