Duroc Line Research Articles

229 Effects of sire line on survivability traits of commercial pigs sired by PIC 800 or a North American competitor Duroc Line from birth to market

Abstract This study aimed to evaluate differences in survivability traits on pigs originating from two sire lines from birth to market. A total of 28,426 commercial pigs sired by either PIC 800 boars (n = 13,960 pigs) or a North American competitor Duroc line (Sire A; n = 14,466 pigs) were used in this study. PIC Camborough sows from 2 sister-sow farms were bred using semen from both genetic lines was mated equally and randomly across sows to ensure sire lines and parity of dams were balanced across farms. Pigs were individually identified at birth by genetic line and cross-fostering was done following standard farm practices. At weaning (average wean age 22 d of age, average body weight 6.8kg), pigs from both lines were sent to nurseries or Wean-to-finish sites (n = 11,541 PIC 800 and n = 11,922 Sire A), comingling in the same barns and pens. Starting inventories for each genetic line were recorded at weaning for all sites, end of nursery (4 wk post weaning), and 1 to 2 wk before start of marketing (target market weight 127kg at 160 d of age). For each production period, information on mortality and morbidity traits (n = 10,600 PIC 800 and n = 10,974 Sire A) was collected. Data were analyzed using R separately for each production period (i.e., Pre-weaning, Grow-to-finish, and Wean-to-finish) and not pooled from birth to market due to some groups not being kept intact. Morbidity and mortality data were analyzed using binomial models with a fixed effect of sire line and a random effect of sow farm or nursery/wean-to-finish site for pre-wean traits or post-weaning traits, respectively. Pigs from farms without removal reason record were excluded from analysis of removal reasons (Table 1). Overall pre-wean mortality was less (P ≤ 0.05) for PIC 800 pigs than Sire A pigs (8.5 vs. 9.6%, for PIC 800 and Sire A, respectively), mostly due to having fewer (P ≤ 0.05) pigs laid-on (4.8 vs 5.9%, respectively). At 4 wk post weaning, PIC 800 pigs had less (P ≤ 0.05) fallout rate than Sire A pigs (2.5 vs 3.5%, for PIC 800 and Sire A, respectively), with no differences (P > 0.05) in mortality rate (1.2 vs 1.3%, respectively). Grow-to-finish morbidity and mortality rates were less (P ≤ 0.05) for PIC 800 (2.1 and 1.3%, for morbidity and mortality rates, respectively) compared with Sire A (2.5 and 1.8%, respectively). Likewise, wean-to-finish morbidity and mortality rates were less (P ≤ 0.05) for PIC 800 (2.5 and 3.7%, for morbidity and mortality rates, respectively) compared with Sire A (3.0 and 4.7%, respectively). Results suggest PIC 800 sired pigs consistently had lower incidence of morbidity and mortality than Sire A pigs across all stages of production included in this study.

Conditions of southern Ukraine pigs productivity under different methods of breeding in modern

The article presents the results of studies concerning pigs’ productivity for purebred breeding and innovative approaches to crossbreeding schemes in the South of Ukraine. In general, sows of all experimental groups had high productivity both in purebred breeding and because of combining different forms with each other however there was no heterosis effect on the sows’ multiplicity in crossbreeding of Large White breed and the complexity of combining the sows of hybrid origin. Young hybrid animals of experimental groups reached a live weight of 100 kg sooner for 2.6-16.4 days or 1.4-8.9 % and feed costs were lower 0.12-0.34 feed units or 3.4-9.7 % per 1 kg gain during the fattening period.
 The obtained results show that the proposed production of final hybrids with a conditional proportion of blood landrace Ч large white in terms of live weight is the most successful and adapted to the technology of moderate intensity. The use of purebred and local animals related to the so-called "White breeds" - Large White and Landrace, is characterized by increased intensity of formation and indices of growth stress. The obtained results additionally confirm the complexity of adaptation of non-ferrous breeds (Duroc and especially Pietrain breeds) to the technological conditions of domestic pork farms. Young pigs were obtained in combinations where the parental form was the breed: Large White, Landrace or Duroc had the best exterior features that characterize the development of animals in length. In combinations where the parent form was the Pietrain breed, the latitudinal measurements and the meat index were improved against the background of a decrease in body length.
 A morphological study of carcasses of young pig stock of different origin has proved that implementation of up-to-date crossbreeding schemes with the use of meat-type breeds as paternal lines results in improved carcass dressing percentage and optimised lean-to-fat ratio. As evident out of the physical and chemical analysis of pork obtained from pigs of different breed-of-origin, all investigated parameters are within the current physiological limits. Most parameters have shown no significant difference, though tended to exhibit some peculiarities associated with the impact of genotype on the manifestation of one or another physical or chemical characteristic. The use of Pietrain breed as a sire line results in decreased intramuscular fat content, and hence the energy value of pork, with the back fat having the highest melting point which is indicative of its enhanced storability, though slightly impaired cooking properties as compared to similar products obtained from the offspring of the Large White and Landrace parents. With respect to its pH level and water-holding capacity, the pork from Pietrain-sired offspring is quite similar to PSE (Pale, Soft, Exudative) meat being slightly less tender and paler in colour and exhibiting greater weight loss during thermal processing. Also, a comprehensive sensory evaluation of boiled pork and pork broth obtained from a group of the Pietrain-sired young stock has got the lowest score, which is consistent with most of the physical and chemical properties of pork from pigs of this genotype; therefore, it is 75% purebred Landrace that should be favoured as a terminal sire line in crossbreeding programmes in order to obtain pork and bacon of improved quality in intensive commercial swine production systems. It is recommended to preliminary combine Pietrain and Duroc lines to produce terminal sires (Pietrain Ч Duroc) which will be further mated with two-breed-cross dams (LW Ч L).

Identification of a missense variant in the porcine AGPAT gene family associated with intramuscular fat content through whole-genome sequencing.

The 1-acylglycerol-3-phosphate O-acyltransferases (AGPATs) are enzymes that catalyze the conversion of lysophosphatidic acid to phosphatidic acid, which is a precursor of triacylglycerol, the main fat reservoir in mammals. We used whole-genome sequencing of 205 pigs to identify 6639 genetic variants in the porcine AGPAT gene family. Of these, 166 common variants in the AGPAT5 gene had significant associations with fat content and composition traits. We preselected a missense single nucleotide polymorphism in exon 6 of AGPAT5 (rs196952262, A>G) for validation of its associations in 1034 pigs from the same Duroc line. The A allele showed a positive additive effect for intramuscular fat content (+1.12% ± 0.21, p < 0.001, for gluteus medius and +0.89% ± 0.33, p < 0.01, for longissimus). We also observed significant associations with fatty acid composition that were, at least in part, independent of the increased intramuscular fat. The A allele resulted in more monounsaturated fatty acids (+0.34% ± 0.15, p < 0.05, for longissimus) and a greater monounsaturated/polyunsaturated fatty acids ratio (+0.11 ± 0.04, p < 0.01, for gluteus medius and +0.13 ± 0.05, p < 0.05, for longissimus). The effect of the AGPAT5 variant on intramuscular fat was more noticeable in fatter pigs, and AGPAT5 interacts with other genes that affect overall fatness such as LEPR. AGPAT5 was the most expressed gene of the AGPAT family in pig skeletal muscle. This variant can be used as a marker in assisted selection for modulating pig fat deposition and fatty acid content.

Identification of Homozygous Regions With Adverse Effects on the Five Economic Traits of Duroc Pigs.

Runs of homozygosity (ROH) are widely used to estimate genomic inbreeding, which is linked to inbreeding depression on phenotypes. However, the adverse effects of specific homozygous regions on phenotypic characteristics are rarely studied in livestock. In this study, the 50 K SNP data of 3,770 S21 Duroc (American origin) and 2,096 S22 Duroc (Canadian origin) pigs were used to investigate the harmful ROH regions on five economic traits. The results showed that the two Duroc lines had different numbers and distributions of unfavorable ROHs, which may be related to the different selection directions and intensities between the two lines. A total of 114 and 58 ROH segments were found with significant adverse effects on the economic traits of S21 and S22 pigs, respectively. Serval pleiotropic ROHs were detected to reduce two or multiple phenotypic performances in two Duroc populations. Candidate genes in these shared regions were mainly related to growth, fertility, immunity, and fat deposition. We also observed that some ROH genotypes may cause opposite effects on different traits. This study not only enhances our understanding of the adverse effects of ROH on phenotypes, but also indicates that ROH information could be incorporated into breeding programs to estimate and control the detrimental effects of homozygous regions.

Runs of Homozygosity Uncover Potential Functional-Altering Mutation Associated With Body Weight and Length in Two Duroc Pig Lines.

Runs of homozygosity (ROH) are widely used to investigate genetic diversity, demographic history, and positive selection signatures of livestock. Commercial breeds provide excellent materials to reveal the landscape of ROH shaped during the intense selection process. Here, we used the GeneSeek Porcine 50K single-nucleotide polymorphism (SNP) Chip data of 3,770 American Duroc (AD) and 2,096 Canadian Duroc (CD) pigs to analyze the genome-wide ROH. First, we showed that AD had a moderate genetic differentiation with CD pigs, and AD had more abundant genetic diversity and significantly lower level of inbreeding than CD pigs. In addition, sows had larger levels of homozygosity than boars in AD pigs. These differences may be caused by differences in the selective intensity. Next, ROH hotspots revealed that many candidate genes are putatively under selection for growth, sperm, and muscle development in two lines. Population-specific ROHs inferred that AD pigs may have a special selection for female reproduction, while CD pigs may have a special selection for immunity. Moreover, in the overlapping ROH hotspots of two Duroc populations, we observed a missense mutation (rs81216249) located in the growth and fat deposition-related supergene (ARSB-DMGDH-BHMT) region. The derived allele of this variant originated from European pigs and was nearly fixed in Duroc pigs. Further selective sweep and association analyses indicated that this supergene was subjected to strong selection and probably contributed to the improvement of body weight and length in Duroc pigs. These findings will enhance our understanding of ROH patterns in different Duroc lines and provide promising trait-related genes and a functional-altering marker that can be used for genetic improvement of pigs.

Sex effects on carcass characteristics, meat quality traits and meat amino acid and fatty acid compositions in a novel Duroc line pig.

In-depth studies of carcass characters and meat quality could provide insight both for breeding improvement and food development in pigs. Breed and gender are two main factors affected the carcass and meat altitude, which plays important roles in pork industry. The aim of this study was to evaluate the sex effects on carcass characteristics and meat quality traits in a novel Duroc strain pig crossbred from French line, American line and Canadian line pigs. A total of 30 pigs (15surgical-castrated males and 15 females) with similar birthweight (1.8±0.13kg) was used in experiment. During the experiment period, all pigs were fed same commercial diets. Overall, female pigs observed higher (p<0.05) carcass weight, slaughter backfat, loin muscle area, loin muscle depth, carcass yield, pH on 45min, meat histidine and essential amino acid (AA) compositions, and eicosenoic, unsaturation and free fatty acids (FA) compositions compared with meat from castrated males. Whereas, castrated males' meat showed better altitude (p<0.05) on meat lightness, meat moisture content percentage, total umami AA and stearic acid and saturated FA compositions than those from female ones. In conclusion, the results of this study provide evidence on the sex effects on meat quality and carcass parameters in Duroc strain pigs. Furthermore, this study also give a reference on the relationship between sex and carcass and meat characteristics in Durco strain pigs.

Genomic Analyses Revealed the Genetic Difference and Potential Selection Genes of Growth Traits in Two Duroc Lines.

Duroc pigs are famous for their high growth rate, feed conversion efficiency, and lean meat percentage. Given that they have been subjected to artificial selection and breeding in multiple countries, various lines with obvious differences in production performance have formed. In this study, we genotyped 3,770 American Duroc (AD) pigs and 2,098 Canadian Duroc (CD) pigs using the GeneSeek Porcine SNP50 Beadchip to dissect the genetic differences and potential selection genes of growth traits in these two Duroc pig lines. Population structure detection showed that there were significant genetic differences between the two Duroc pig lines. Hence, we performed FST and cross-population extended haplotype homozygosity (XP-EHH) analyses between the two lines. As a result, we identified 38 annotated genes that were significantly enriched in the gland development pathway in the AD line, and 61 annotated genes that were significantly enriched in the immune-related pathway in the CD line. For three growth traits including backfat thickness (BFT), loin muscle depth (LMD), and loin muscle area (LMA), we then performed selection signature detection at 5 and 10% levels within the line and identified different selected regions and a series of candidate genes that are involved in lipid metabolism and skeletal muscle development or repair, such as IRX3, EBF2, WNT10B, TLR2, PITX3, and SGCD. The differences in selected regions and genes between the two lines may be the cause of the differences in growth traits. Our study suggests significant genetic differences between the AD and CD lines, which provide a theoretical basis for selecting different Duroc lines as sires for different needs.

PSIII-10 The Effect of Sire Line on Grow-finish Performance, Carcass Characteristics, and Meat Pricing Variables for Commercial Crossbred Pigs

Abstract The objective of this study was to evaluate the effect of sire line on wean-to-finish performance, carcass characteristics, and meat pricing variables. Pigs used for this study were the progeny of a commercial Landrace x Large White female mated to one of the following sire lines: a purebred Duroc line (Line S1), or a synthetic (Line S2) or purebred Duroc line (Line S3) originating from a different genetic source. An equivalent number of pigs (n =144) were used per group, for 432 pigs placed on test. Average initial weights per line were 6.67 ± 0.24, 6.67 ± 0.24, and 6.60 ± 0.24 for lines S1, S2, and S3, respectively. At placement, 8 pigs were assigned to each pen (split sex) and blocked by line and initial BW, with 18 replicates per line. Data were analyzed at the pen level using the PROC MIXED procedure of SAS, where the effects of line, sex, and line*sex were fitted as fixed effects and replicate was fitted as a random effect. Overall, piglets from line S2 (0.403 vs 0.381; P ≤ 0.0004) and line S3 (0.402 vs 0.381; P ≤ 0.001) had improved GF compared with piglets from line S1. The ADFI was greater in piglets from line S1 relative to piglets from line S2 (2.264 vs 2.117 kg; P ≤ 0.0001) and line S3 (2.264 vs 2.159 kg; P ≤ 0.004). The ADG, HCW, dressing yield, and loin depth were not different among treatment (P &amp;gt; 1.00). Piglets from line S3 had greater percent lean (57.12 vs 56.29 %; P ≤ 0.0001) and better carcass grade premium ($7.07 vs 6.60; P ≤ 0.0291) relative to piglets from line S1. In conclusion, line S1 piglets had greatest ADFI, but line S2 pigs and line S3 piglets had better feed efficiency. Line S3 pigs were leaner and had better carcass grade premium.

PSIII-9 The Effect of Sire Line on Reproductive Performance During Lactation

Abstract The objective of this study was to estimate the effect of sire line on sow and piglet performance during lactation. Commercial Landrace x Large White females (n = 60) were bred to one of the following sire lines: a purebred Duroc line (Line S1), a synthetic (Line S2), or purebred Duroc (Line S3) from a different genetic source. Matings were balanced by line and parity. Females were fed a common gestation and lactation diet during these respective phases. Sow and piglet data were analyzed as a completely randomized design using the GLM procedure of SAS. Results show that, during lactation, females bred to line S3 lost significantly (P = 0.01) more BW (-16.93 ± 3.56 kg) than females bred to line S2 (-2.00 ± 3.50 kg). However, no evidence of a difference (P = 0.18) in BW loss was detected between females bred to line S3 (-16.93 ± 3.56 kg) vs. Line S1 (-7.90 ± 3.56 kg). Further, sows bred to line S3 weaned significantly (P = 0.03) more piglets (12.0 ± 0.28) than females bred to line S2 (10.9 ± 0.27), but not (P = 0.1) compared to females bred to line S1 (11.7 ± 0.27). No significant effect of line (P &amp;gt; 0.05) or parity (P &amp;gt; 0.05) on total number of piglet’s born, number born alive, number of stillborn piglets, or preweaning mortality was detected. The number of mummified fetus tended to be lower in line S2 (0.17 vs 0.66; P = 0.079) and line S3 (0.12 vs 0.66; P = 0.051) sows compared with line S1 sows, respectively. In conclusion, sire line did not have a significant effect on total number born, number born alive, number stillborn, or preweaning mortality. However, females bred to line S3 lost significantly more BW during lact but weaned significantly more piglets than females bred to line S2.

Antagonistic maternal and direct effects of the leptin receptor gene on body weight in pigs.

Maternal effects on offspring growth can impact survival and evolution of natural and domesticated populations. Genetic correlation estimates often support a negative relationship between direct and maternal effects. However, the genetic underpinnings whereby this antagonism operates are unclear. In pigs, sow feeding status and body composition condition piglet development and growth. We hypothesized that variants in genes impacting these traits may be causative of maternal influences that could be antagonistic to the direct effects for piglet growth. A recessive missense mutation (C>T) in the porcine leptin receptor (LEPR) gene (rs709596309) has been identified as the possible causal polymorphism for increased feed intake and fatness. Using data from a Duroc line, we show that the TT sows exerted a negative impact on the body weight of their offspring at the end of the growing period of similar extent to the positive direct effect of the TT genotype over each individual. Thus, TT pigs from TT dams were about as heavy as CC and CT (C–) pigs from C–dams, but TT pigs from C–dams were around 5% heavier than C–pigs from TT dams. In contrast, body composition was only influenced by LEPR direct effects. This antagonism is due to a higher propensity of TT pigs for self-maintenance rather than for offspring investment. We show that TT pigs consumed more feed, favored fatty acid uptake over release, and produced lighter piglets at weaning than their C–counterparts. We conclude that LEPR underlies a transgenerational mechanism for energy distribution that allocates resources to the sow or the offspring according to whether selective pressure is exerted before or after weaning.

99 Breed authentication of five lines comparing Structure, Admixture, and an allele frequency method

Abstract Two commonly used population structure software packages are freely available for breed authentication, Structure and Admixture. Structure uses a Bayesian approach to model population structure, while Admixture uses a frequentist approach. More recently, an allele frequency method has been updated to use quadratic programming to constrain the multiple linear regression coefficients of the regression of genotype count (divided by two) on the matrix of allele frequencies for each known breed or line. This constraint forced coefficients to sum to one and be greater than or equal to 0 and less than or equal to 1. The goal of this research was to compare and contrast these three methods to determine the breed/line authenticity for each of the five genetic lines. These five lines included Large White, Landrace, a lean Duroc, a meat quality Duroc, and a Pietrain line. Only animals with a 50K SNP panel were used in this analysis. Analyses were run five times for Structure and Admixture to check repeatability. The allele frequency method did not need to be repeated because it remains the same as long as the reference allele frequency matrix stays constant. For Structure, results of breed composition were inconsistent across replicates. Structure separated at least one of the maternal lines in three out of the five replicates with only 500 animals and kept the Duroc lines together as one population. Only 500 animals could be utilized in each run of Structure due to computational restraints. Admixture was very consistent across runs for each animal, but also failed to separate the two Duroc lines, instead splitting one of the two maternal lines. Finally, the allele frequency method split all five lines correctly and was 100% reproducible as long as the reference allele frequency matrix stays the same across runs.

ASSESSMENT OF THE QUALITY OF MODERN COMMERCIAL PORK PRODUCTS

By a morphological study of carcasses of young pig stock of different origin, it has been proved that up-to-date crossbreeding schemes using meat-type breeds as parents increase the percentage of meat in a carcass and optimise the lean-to-fat ratio. Physicochemical analysis of pork obtained from pigs of different breeds has shown that all the parameters investigated are within the current physiological standards. Most parameters have shown no significant difference, though tend to exhibit some peculiarities associated with the effect of a genotype on how this or that physicochemical characteristic manifests itself. The use of the Piétrain breed as the sire line decreases the intramuscular fat content, and hence the calorific value of pork. The back fat of this breed has the highest melting point, which indicates its high storability, but somewhat lower cooking properties than those of similar products obtained from offspring of Large White and Landrace parents. The pH and water-holding capacity of the pork of Piétrain-sired offspring make it quite similar to PSE (Pale, Soft, Exudative) meat: this pork is slightly less tender and paler in colour and exhibits greater weight loss during thermal processing. Also, the result of a comprehensive sensory evaluation of boiled pork and pork broth obtained from Piétrain-sired young stock was the lowest, which is consistent with most of the physicochemical properties of pork from pigs of this genotype. So, it is the 75% purebred Landrace that should be favoured as a terminal sire line in crossbreeding programmes in order to obtain pork and bacon of improved quality in intensive commercial swine production systems. It is recommended to combine Piétrain and Duroc lines to produce terminal sires, ½ (Piétrain + Duroc), that will be further mated with two-breed-cross dams – ½ (Large White + Landrace).

Duroc boars have lower progeny mortality and lower fertility than Pietrain boars.

In pig production, Pietrain and Duroc lines are often used as terminal sire lines to produce crossbred slaughter pigs. The objective of this study was to identify the differences in paternal fertility and mortality during the suckling period of crossbred progeny from Pietrain and Duroc terminal sire lines. In total, 87 purebred Duroc boars and 68 purebred Pietrain boars were used as terminal sires to produce 1,823 crossbred Duroc litters (D-litters) and 1,705 crossbred Pietrain litters (P-litters) in two production herds. The sows were crosses between DanBred Landrace and Yorkshire (F1). All boars were kept at the same artificial insemination (AI) station, and all semen doses were produced in the same laboratory. The experiment was balanced according to herd, boars, and time, with approximately 13 sows from each herd mated to each boar within each breed. The results showed higher fertility expressed as litter size at birth in P-litters compared with D-litters led to 0.5 higher total number born (TNB) for P-litters (P = 0.0076). However, piglet mortality including number of stillborn piglets was lower in D-litters compared with P-litters (P < 0.0001), and 5 d after farrowing, the average litter size in P-litters ranged 0.4 below the litter size in D-litters (P < 0.027). At 21 d after birth, mean litter size in P- and D-litters were 14.5 and 14.9 piglets per litter, respectively (P < 0.015). This indicated that Pietrain progenies were weaker than Duroc progenies, and it was concluded that use of Duroc boars as the terminal sire line led to lower piglet mortality. In the two herds, the mean piglet mortality rate including still born piglets ranged from 19.5% to 23.6% and from 17.6% to 19.1% in P- and D-litters, respectively.

Sow communication with piglets while being active is a good predictor of maternal skills, piglet survival and litter quality in three different breeds of domestic pigs (Sus scrofa domesticus)

Maternal care behaviour is crucial for offspring quality and survival in pigs. Defining care is therefore essential for ensuring the welfare of pigs and sustainability of pig production. The aim of the present study was to investigate the relationship between sow nest building, communication with piglets (sniffing, nudging, grunting) during resting and activity, and piglet survival in three different sow breeds: a maternal line selected for high weaned pig production (Landrace), a paternal line selected for meat traits (Duroc), and a crossbred line (Landrace and Yorkshire). We predicted that a higher frequency of nest building and sow communication would have a positive impact on piglet survival. Secondly, we predicted that a high level of maternal care outside the time of nursing (nest building and communication) would increase the quality of the litter (weight at weaning). We also predicted that nest building activity and sow communication would be more pronounced in maternal sow lines selected for maternal traits than in a non-selected, paternal line, and that primiparous sows would perform more nest building behaviour and communicate more than multiparous sows due to high investment in their first litter. Finally, an impaired condition around farrowing (i.e. low body condition score and presence of shoulder lesions) was predicted to be negatively correlated to care behaviours. Data was collected on 38 sows with 511 born piglets. Sows with their litters, were loose-housed in individual farrowing pens until weaning. Nest building activity can be partly considered as maternal care behaviour as it prepares the sows for motherhood and is associated with a lower proportion of stillborn piglets (P < 0.001), starved piglets (P = 0.004), and overlaid piglets (P = 0.034). As predicted, sows that communicated more while being active had lower postnatal piglet mortality (starvation (P < 0.001), less overlying (P < 0.001), overlying with (P < 0.001), and without the milk in the stomach (P < 0.001) and fewer that died of other causes (P < 0.001), higher piglet survival (P < 0.001) and litter weight (P < 0.001) at weaning irrespective of the breed. A higher level of communication while active was associated with more pronounced shoulder lesions in sows (P = 0.010), suggesting a positive association between good maternal care and prevalence of shoulder lesions. We also found that resting sows that communicated more with piglets outside the time of nursing, had higher postnatal piglet mortality (P < 0.001) due to starvation (P < 0.001), overlying (P < 0.001), overlying with (P < 0.001), or without milk (P < 0.001). Communication during resting was more pronounced with increasing litter size at birth (P < 0.001), especially for thin sows (P < 0.001). Communication during resting was more pronounced in the non-selected Duroc line (P < 0.001). Our results suggest that sow communication while being active is a good predictor of good maternal care, piglet survival and litter quality in three different breeds of domestic pigs.

Genome-wide association studies for seven production traits highlight genomic regions useful to dissect dry-cured ham quality and production traits in Duroc heavy pigs

Protected designation of origin dry-cured hams are obtained from heavy pigs (slaughtered at about 160 kg of live weight). A specific breeding program designed to improve meat quality for this production has included as key traits the level of intermuscular fat between the leg muscles and ham weight loss during the seasoning period together with a balance between fat and lean cuts. In this study we carried out genome-wide association studies for seven traits used in the genetic merit of Italian Duroc heavy pigs, five related to meat and carcass quality traits (visible intermuscular fat, ham weight loss at first salting, backfat thickness, ham weight and lean cuts), and two related to performance and efficiency traits (average daily gain and feed : gain ratio). A total of 573 performance-tested pigs were genotyped with the Illumina PorcineSNP60 BeadChip and genome-wide association analyses were carried out using the Bayes B approach with the 1 Mb window option of GenSel and random residuals for each of the seven traits. Detected windows were supported by independent single nucleotide polymorphism analyses with a linear mixed model (LMM) approach on the same animals for the same traits. A total of 30 windows identifying different quantitative trait loci (QTL) were detected and among those, 27 were confirmed by LMM in one of these traits. Among the confirmed windows, three QTL were reported for visible intermuscular fat, seven for ham weight loss at first salting and five and four for backfat thickness and lean cut, respectively. A total of eight QTL were detected for the other production traits. No overlapping QTL were reported except for one window on porcine chromosome 10 between lean cuts and ham weight that contained the CACNB2 gene that has been already associated with loin marbling score in other Duroc pigs. Several regions contained genes that have been already associated with production traits in other pig breeds, including Duroc lines, related to fat deposition or muscle structure. This work reports, for the first time, genome-wide association study results for several traits in Italian Duroc heavy pigs. These results will be useful to dissect the genetic basis for dry-cured ham production traits that determine the total genetic merit index of Italian Duroc pigs.

Physicochemical changes of semimembranosus muscle during the processing of dry-cured ham from Celta pig. Effect of crossbreeding with Duroc and Landrace genotypes

Physicochemical characteristics of dry-cured hams from three genetic types, Celta breed (C line), Celta × Duroc (C × D) and Celta × Landrace (C × L) were determined on the semimembranosus muscle during 551 days of aging. Hams were obtained from 60 pigs reared in extensive systems and finished with a commercial feeding. Physicochemical parameters (pH and water activity) and chemical composition, (moisture, intramuscular fat, ash, protein and total chlorides content), colour parameters (L*, a* and b*) and lipid oxidation (thiobarbituric acid reactive substances value) were studied during the whole process after salting, post-salting, drying and bodega stages. Hams from crosses were characterised by higher intramuscular fat (12.78% and 10.48% for C × D and C × L lines, respectively) and moisture (46.86% and 46.63% for C × D and C × L genotypes, respectively), contents respect to Celta pure line that showed values of 5.96% and 35.83% for intramuscular fat and water content, respectively. Concerning colour parameters, hams from Celta line had lower values for all colour traits. The influence of crossbreeding on most physicochemical parameters observed was mainly due to the differences in moisture and intramuscular fat between hams obtained from pure breed and crosses. As a general conclusion, the crossbreeding of Celta pig (especially with the Duroc line) allows to improve the quality of dry-cured hams.

TRIENNIAL GROWTH AND DEVELOPMENT SYMPOSIUM: Genetics and breeding for intramuscular fat and oleic acid content in pigs.

The intramuscular fat (IMF) and oleic acid (OL) content have been favorably related to pork quality and human health. This influences the purchasing behavior of consumers and, therefore, also shifts the attention of breeding companies toward whether these traits are included into the breeding goal of the lines producing for high-valued markets. Because IMF and OL are unfavorably associated with lean content, a key economic trait, the real challenge for the industry is not simply to increase IMF and OL, but rather to come up with the right trade-off between them and lean content. In this paper we review the efforts performed to genetically improve IMF and OL, with particular reference to the research we conducted in a Duroc line aimed at producing high quality fresh and dry-cured pork products. Based on this research, we conclude that there are selection strategies that lead to response scenarios where IMF, OL, and lean content can be simultaneously improved. Such scenarios involve regular recording of IMF and OL, so that developing a cost-efficient phenotyping system for these traits is paramount. With the economic benefits of genomic selection needing further assessment in pigs, selection on a combination of pedigree-connected phenotypes and genotypes from a panel of selected genetic markers is presented as a suitable alternative. Evidence is provided supporting that at least a polymorphism in the leptin receptor and another in the stearoyl-CoA desaturase genes should be in that panel. Selection for IMF and OL results in an opportunity cost on lean growth. The extent to which it is affordable relies on the consumers' willingness to pay for premium products and on the cost to benefit ratio of alternative management strategies, such as specific dietary manipulations. How the genotype can influence the effect of the diet on IMF and OL remains a topic for further research.

0791 Genetics and breeding for intramuscular fat and oleic acid content in pigs

The intramuscular fat (IMF) and oleic acid (OL) content have been favorably related to pork quality and human health. This influences the purchasing behavior of consumers and, therefore, also shifts the attention of breeding companies toward whether these traits are included into the breeding goal of the lines producing for high-valued markets. Because IMF and OL are unfavorably associated with lean content, a key economic trait, the real challenge for the industry is not simply to increase IMF and OL, but rather to come up with the right trade-off between them and lean content. In this paper we review the efforts performed to genetically improve IMF and OL, with particular reference to the research we conducted in a Duroc line aimed at producing high quality fresh and dry-cured pork products. Based on this research, we conclude that there are selection strategies that lead to response scenarios where IMF, OL, and lean content can be simultaneously improved. Such scenarios involve regular recording of IMF and OL, so that developing a cost-efficient phenotyping system for these traits is paramount. With the economic benefits of genomic selection needing further assessment in pigs, selection on a combination of pedigree-connected phenotypes and genotypes from a panel of selected genetic markers is presented as a suitable alternative. Evidence is provided supporting that at least a polymorphism in the leptin receptor and another in the stearoyl-CoA desaturase genes should be in that panel. Selection for IMF and OL results in an opportunity cost on lean growth. The extent to which it is affordable relies on the consumers' willingness to pay for premium products and on the cost to benefit ratio of alternative management strategies, such as specific dietary manipulations. How the genotype can influence the effect of the diet on IMF and OL remains a topic for further research.

Relationship between perilipin genes polymorphisms and growth, carcass and meat quality traits in pigs.

The perilipins (PLIN) belong to a family of structural proteins that play a role regulating intracellular lipid storage and mobilization. Here, PLIN1 and PLIN2 have been evaluated as candidate genes for growth, carcass and meat quality traits in pigs. A sample of 607 Duroc pigs were genotyped for two single-nucleotide polymorphisms, one in intron 2 of the PLIN1 gene (JN860199:g.173G>A) and the other at the 3' untranslated region of the PLIN2 gene (GU461317:g.98G>A). Using a Bayesian approach, we have been able to find evidence of additive, dominant and epistatic associations of the PLIN1 and PLIN2 polymorphisms with early growth rate and carcass length. However, the major effects were produced by the dominant A allele at the PLIN2 polymorphism, which also affected the carcass lean weight. Thus, pigs carrying an additional copy of the A allele at the g.98G>A PLIN2 polymorphism had a probability of at least 98% of producing carcasses with heavier lean weight (+0.41kg) and ham weight (+0.10kg). The results obtained indicate that the PLIN2 polymorphism could be a useful marker for lean growth. In particular, it may help to reduce the undesired negative correlated response in lean weight to selection for increased intramuscular fat content, a common scenario in some Duroc lines involved in the production of high quality pork products.

A Functional Variant in the Stearoyl-CoA Desaturase Gene Promoter Enhances Fatty Acid Desaturation in Pork

There is growing public concern about reducing saturated fat intake. Stearoyl-CoA desaturase (SCD) is the lipogenic enzyme responsible for the biosynthesis of oleic acid (18∶1) by desaturating stearic acid (18∶0). Here we describe a total of 18 mutations in the promoter and 3′ non-coding region of the pig SCD gene and provide evidence that allele T at AY487830:g.2228T>C in the promoter region enhances fat desaturation (the ratio 18∶1/18∶0 in muscle increases from 3.78 to 4.43 in opposite homozygotes) without affecting fat content (18∶0+18∶1, intramuscular fat content, and backfat thickness). No mutations that could affect the functionality of the protein were found in the coding region. First, we proved in a purebred Duroc line that the C-T-A haplotype of the 3 single nucleotide polymorphisms (SNPs) (g.2108C>T; g.2228T>C; g.2281A>G) of the promoter region was additively associated to enhanced 18∶1/18∶0 both in muscle and subcutaneous fat, but not in liver. We show that this association was consistent over a 10-year period of overlapping generations and, in line with these results, that the C-T-A haplotype displayed greater SCD mRNA expression in muscle. The effect of this haplotype was validated both internally, by comparing opposite homozygote siblings, and externally, by using experimental Duroc-based crossbreds. Second, the g.2281A>G and the g.2108C>T SNPs were excluded as causative mutations using new and previously published data, restricting the causality to g.2228T>C SNP, the last source of genetic variation within the haplotype. This mutation is positioned in the core sequence of several putative transcription factor binding sites, so that there are several plausible mechanisms by which allele T enhances 18∶1/18∶0 and, consequently, the proportion of monounsaturated to saturated fat.