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The present study investigated differences in the allocation patterns of body stores in lactating female mice from a line selected for high litter size at birth (S-line, average litter size of 20) and dams from a nonselected control line (C-line, average litter size of 10). Body weight, litter size, litter weight, and absolute and relative lipid and protein mass were measured at peak lactation (2 wk in lactation) and at weaning (3 wk in lactation). Body size in S-line females has been increased as a correlated effect of selection for high litter size at birth, allowing for larger litters and higher absolute milk production. However, these dams produce larger litters relative to their own body weight. At peak lactation, lipid and protein percentage did not differ between lines. At weaning, S-line females had a higher protein percentage (P < 0.001) and lower lipid percentage (P < 0.05) than C-line females. Apparently, S-line females produce more offspring but at a greater cost to their own metabolism. This process was insufficient to supply the offspring with adequate resources, resulting in reduced (P < 0.0001) pup development and increased (P < 0.0001) preweaning mortality rates.

An experimental F2 cross between Iberian and Landrace pig strains was performed to map quantitative trait loci (QTL) for diverse productive traits. Here we report results for meat quality traits from 369 F2 animals with records for pH 24 h postmortem (pH 24 h), muscle color Minolta measurements L* (lightness), a* (redness), and b* (yellowness), H* (hue angle), C* (chroma), intramuscular fat (IMF) and haematin pigment content measured in the longissimus thoracis. Pigs were genotyped for 92 markers covering the 18 porcine autosomes (SSC). Results of the genome scan show evidence for QTL for IMF (SSC6; F = 27.16), pH 24 h (SSC3; F = 7.73), haematin pigments (SSC4 and SSC7; F = 8.68 and 9.47 respectively) and Minolta color measurements L* (SSC4 and SSC7; F =16.42 and 7.17 respectively), and a* (SSC4 and SSC8; F = 8.05 and 7.36 respectively). No QTL were observed for the color measurements b*, H*, and C*. Alternative models fitting epistasis between QTL were also tested, but detected epistatic interactions were not significant at a genome-wise level. In this work we identify genomic regions related with meat quality traits. Improvement by traditional selection methods is complicated, and finer mapping would be required for their application in introgression programs.

Data on individually tested pigs from a line selected for litter size (H) and a control line (C) were used to estimate the correlated responses to litter size in growth, fat, and feeding behavior patterns from 75 to 165 d of age. During the test period, BW and ultrasonic midback (UMB) and loin (ULB) backfat were recorded periodically on the same animal. Individual voluntary feed intake (DFI), number of visits (NVD), and feeding time (FTD) were measured on a daily basis using an automatic feeding system. Third degree polynomial models with random regression coefficients were used to describe BW, UMB, ULB, DFI, NVD, and FTD as a function of age. The first derivative of the model for BW was used to estimate growth rate. Several measurements of efficiency were obtained using polynomial models on accumulated DFI, NVD, and FTD. The difference between the genetic means of animals from line H and line C was used to estimate correlated responses. The H pigs showed higher BW throughout most of the test period (2.29 +/- 0.90 kg at 135 d of age, P < 0.05) but they were not different (P = 0.18) from C pigs at the end of the test (102 kg, SD 9). Thus, despite both lines showing similar average growth rate on the test, line H grew faster at the start of the test (34 +/- 11 g/d, P < 0.01), but it grew more slowly by the end (-68 +/- 27 g/d, P < 0.05). Fat deposition rate differed between lines, with H pigs showing higher UMB (1.26 +/- 0.23 mm, P < 0.01) and ULB (1.32 +/- 0.28 mm, P < 0.01) at 165 d of age. The difference between lines in total on-test feed intake was not significant (P= 0.10), but intake was slightly higher in line H between 105 and 135 d of age (2.28 +/- 1.25 kg, P = 0.07). Line H showed a higher feed efficiency up to about 100 d of age, whereas line C performed better from this age until 165 d of age. However, differences never exceeded 18 +/- 6 g of weight gain per kilogram of feed consumption (P < 0.01). Total feed efficiency throughout the test period was slightly higher in line C (1.37 +/- 0.77 kg of weight gain after eating 185 kg of feed, P = 0.08). Lines H and C had distinct feeding patterns with regard to eating frequency. Pigs from line H ate less frequently, but instead they spent more time and ate more per visit. In the long term, selection for litter size could result in pigs with less capacity of lean growth.

Results from a QTL experiment on growth and carcass traits in an experimental F2 cross between Iberian and Landrace pigs are reported. Phenotypic data for growth, length of carcass and muscle mass, fat deposition and carcass composition traits from 321 individuals corresponding to 58 families were recorded. Animals were genotyped for 92 markers covering the 18 porcine autosomes (SSC). The results from the genomic scan show genomewide significant QTL in SSC2 (longissimus muscle area and backfat thickness), SSC4 (length of carcass, backfat thickness, loin, shoulder and belly bacon weights) and SSC6 (longissimus muscle area, backfat thickness, loin, shoulder and belly bacon weights). Suggestive QTL were also found on SSC1, SSC5, SSC7, SSC8, SSC9, SSC13, SCC14, SSC16 and SSC17. A bidimensional genomic scan every 10 cM was performed to detect interaction between QTL. The joint action of two suggestive QTL in SSC2 and SSC17 led to a genome-wide significant effect in live weight. The results of the bidimensional genomic scan showed that the genetic architecture was mainly additive or the experimental set-up did not have enough power to detect epistatic interactions.

Data on a pig line selected for litter size (H) and a control line (C) were used to estimate the correlated responses to litter size in carcass, meat, and fat quality traits. The differences between the genetic means of animals from line H and line C were used to estimate correlated responses. No differences were found between the two lines in carcass measurements except backfat depth, which was higher (P < 0.05) in line H (0.69 +/- 0.28 mm). This led to a decrease (P < 0.05) in predicted carcass lean content (-6.0 +/- 2.7 g/kg). Differences in joint weight distribution between lines were primarily due to belly weight, which was higher (P < 0.05) in line H (6.3 +/- 1.2 g/kg). There were no important changes in meat quality traits. Chemical composition of semimembranosus muscle (SM) and subcutaneous backfat (SB) differed between lines only for DM in SB, which was higher (P < 0.05) in line H (15.1 +/- 7.1 mg/g), and for the fatty acid composition of intramuscular fat. The fatty acid profile in line H showed a lower (P < 0.01) proportion of polyunsaturated fatty acids (-14.7 +/- 4.8 mg/g FA), particularly with regard to the content of linoleic acid (-12.5 +/- 3.9 mg/g FA). It is concluded that selection for litter size reduced the lean content in the carcass but the proportion of high-priced cuts and meat quality traits were not affected. However, selection may lead to changes in the composition of intramuscular fat lipids towards a lower content of polyunsaturated fatty acids. The observed correlated effects can be interpreted assuming that selected pigs are more mature at the same weight, though the underlying genetic and physiologic processes that cause them are unknown. The results of this experiment indicate that the metabolic pathways taking part in fat metabolism should be considered first.

Litter size and production trait responses to experimental selection for increased litter size in a Landrace pig population are reported. The numbers of sows and litters available for the first cycle of selection were 3,034 and 961, respectively. Selection was carried out using a BLUP repeatability animal model for number of piglets born alive (NBA). The experiment included one selection and one control line, each with three nonoverlapping generations. The selection line (H) consisted of the 160 sows with the highest breeding values and one boar from each of 25 full-sib families with the highest breeding values. The control line (C) consisted of 160 sows and 25 boars randomly chosen. The two subsequent generations in each line were obtained by random selection. A Bayesian analysis of genetic response using a multivariate model was carried out by Gibbs sampler. Marginal posterior distributions were obtained for direct response in NBA, and for correlated response in weight (WT), and backfat thickness (BT) at 175 d of age. The posterior means and posterior standard deviation (PSD) for direct genetic response of NBA ranged from 0.32 (PSD 0.08) in the first parity to 0.64 (PSD 0.08) in the fourth. The posterior means for correlated genetic response in WT and BT were -0.66 kg (PSD 0.36) and 0.20 mm (PSD 0.10), respectively. For WT and BT, the 95% highest posterior density regions (HPD) contain zero-correlated genetic response. Marginal posterior distributions of selection differentials were investigated. The posterior means for standardized selection differentials for NBA in different parities ranged from 0.70 (PSD 0.12) to 0.94 (PSD 0.06) in females for line H, from 0.22 (PSD 0.19) to 0.34 (PSD 0.10) in males for line H, and from 0.08 (PSD 0.08) to 0.13 (PSD 0.07) in females for line C. All available males were used in line C. Results from this experiment showed that selection for increased litter size is effective. Responses to selection were heterogeneous across parities, suggesting that litter size in each parity may have a different genetic background. No correlated genetic response to growth and backfat thickness was observed.

A total of 66,620 records from the first six parities for number of piglets born alive (NBA) from 20,120 Landrace sows and 24,426 records for weight (WT) and backfat thickness (BT) at 175 d of age were analyzed to estimate genetic parameters. The pedigree consisted of 47,186 individuals, including 392 sires and 5,394 dams. Estimates were based on marginal posterior distribution of the genetic parameters obtained using Bayesian inference implemented via the Gibbs sampling procedure with a Data Augmentation step. The posterior means and posterior standard deviation (PSD) for heritability of NBA ranged from 0.064 (PSD 0.005) in the first parity to 0.146 (PSD 0.019) in the sixth parity, always increasing with the order of the parity. The posterior means for genetic correlations of litter size between adjacent parities were, in most cases, greater than 0.80. However, genetic correlation were much lower between nonadjacent parities. For example, the genetic correlation was 0.534 (PSD 0.061) between the fourth and the sixth parity for NBA. The posterior means of heritability for WT and BT were 0.229 (PSD 0.018) and 0.350 (PSD 0.019), respectively. Posterior mean for genetic correlation between WT and BT was 0.339 (PSD 0.044). The posterior means for genetic correlation between production (WT and BT) and reproduction traits (NBA in different parities) were close to zero in most cases. Results from this study suggest that different parities should be considered as different traits. Moreover, selection for growth and backfat should result in no or very little correlated response in litter size.

We present a very flexible method that allows us to analyze X-linked quantitative trait loci (QTL) in crosses between outbred lines. The dosage compensation phenomenon is modeled explicitly in an identity-by-descent approach. A variety of models can be fitted, ranging from considering alternative fixed alleles within the founder breeds to a model where the only genetic variation is within breeds, as well as mixed models. Different genetic variances within each founder breed can be estimated. We illustrate the method with data from an F(2) cross between Iberian x Landrace pigs for intramuscular fat content and meat color component a*. The Iberian allele exhibited a strong overdominant effect for intramuscular fat in females. There was also limited evidence of one or more regions affecting color component a*. The analysis suggested that the QTL alleles were fixed in the Iberian founders, whereas there was some evidence of segregation in Landrace for the QTL affecting a* color component.

One QTL affecting backfat thickness (BF), intramuscular fat content (IMF) and eye muscle area (MA) was previously localized on porcine chromosome 6 in an F2 cross between Iberian and Landrace pigs. This work was done to study the effect of two positional candidate genes on these traits: H-FABP and LEPR genes. The QTL mapping analysis was repeated with a regression method using genotypes for seven microsatellites and two PCR-RFLPs in the H-FABP and LEPR genes. H-FABP and LEPR genes were located at 85.4 and 107 cM respectively, by linkage analysis. The effects of the candidate gene polymorphisms were analyzed in two ways. When an animal model was fitted, both genes showed significant effects on fatness traits, the H-FABP polymorphism showed significant effects on IMF and MA, and the LEPR polymorphism on BF and IMF. But when the candidate gene effect was included in a QTL regression analysis these associations were not observed, suggesting that they must not be the causal mutations responsible for the effects found. Differences in the results of both analyses showed the inadequacy of the animal model approach for the evaluation of positional candidate genes in populations with linkage disequilibrium, when the probabilities of the parental origin of the QTL alleles are not included in the model.

Three Iberian boars were bred to 31 Landrace sows to produce 79 F1 pigs. Six F1 boars were mated to 73 F1 sows. The F2 progeny from 33 full-sib families (250 individuals) were genotyped for seven microsatellites spanning the length of chromosome 4. Least squares procedures for interval mapping were used to detect quantitative trait loci (QTL). A permutation test was used to establish nominal significance levels associated with QTL effects, and resulting probability levels were corrected to a genomewide basis. Observed QTL effects were (genomewide significance, position of maximum significance in centimorgans): percentage of linoleic acid in subcutaneous adipose tissue (< 0.01, 81); backfat thickness (< 0.01, 83); backfat weight (< 0.01, 80); longissimus muscle area (0.02, 83); live weight (0.19, 88); and percentage of oleic acid in subcutaneous adipose tissue (0.25, 81). Gene action was primarily additive. The Iberian genotypes were fatter, slower growing, and had lower linoleic and higher oleic acid contents than Landrace genotypes. The interval from 80 to 83 cM contains the FAT1 and A-FABP loci that have been shown previously to affect fat deposition in pigs. This is the first report of a QTL affecting fatty acid composition of subcutaneous adipose tissue in pigs and provides a guide for the metabolic pathways affected by candidate genes described in this region of chromosome 4.

Irritable bowel syndrome is the most frequently diagnosed disorder in gastroenterology. It has been demonstrated with specialized motility studies that these patients compared to healthy subjects show changes in rectoanal electrical and mechanical activity and in rectoanal sensitivity. However, until now no report has been published on morphological alterations in the rectum or the internal anal sphincter. Twenty-five consecutive patients with irritable bowel syndrome (mean age 32, range 17-47 years; 24 females) were evaluated prospectively by transrectal ultrasonography, rectal sensitivity studies, and recordings of both electrical and mechanical activity of the distal rectum and internal anal sphincter during a 2-h inter-digestive period. Ten healthy volunteers (mean age 34.5, range 19-50 years) served as a control group. Paired and non-paired Student's two-tailed t test and linear regression analysis were used. It was shown that muscle thickness of the rectum during rest (4.7 +/- 0.1 mm) was correlated neither with its rectal spike amplitude (0.73 +/- 0.1 mV) nor with rectal spike frequency (17.06 +/- 3.6 spike/2 h). In addition, the diameter of the internal anal sphincter (1.2 +/- 0.1 mm) was correlated neither with its resting pressure, nor with frequency (17.1 +/- 3.2/2 h), duration (14.9 +/- 1.5 s), or amplitude (14.1 +/- 1.9 mmHg), of inhibition of the spontaneous rectoanal inhibitory reflex. No correlation was found between ultrasonographic parameters and rectal distension variables (r = 0.03). This study demonstrates for the first time morphological anorectal changes in patients with irritable bowel syndrome compared to healthy subjects, in addition to showing that morphological changes are independent of physiological ones. Therefore both transrectal ultrasonography to determine anorectal morphology and electromanometry to assess anorectal function are important measures in the evaluation of patients with irritable bowel syndrome.

Background: In patients with IBS, many symptoms have their origin in the recto-anal segment, with motility changes in the rectum and in the internal anal sphincter, and alterations in rectal sensitivity. However, up to now, it is not known if these clinical and physiological changes are equated with morphological changes in the recto-anal segment., Methods: Sixteen consecutive patients with IBS (mean age 22, range 18-33 years; 13 females) and 10 healthy volunteers (mean age 34.5, range 19-50 yr.; 6 males) were evaluated prospectively with defaecography., Results: 1) Anorectal angle: No significant differences were observed in the anorectal angle during rest (91.6 +/- 3.5 degrees vs 92.6 +/- 2.5 degrees) and during defaecation (92 +/- 5.5 degrees vs 98.7 +/- 2.6 degrees) between patients with IBS and healthy volunteers. However, patients with IBS were unable to widen the angle during defaecation, remaining the same at rest (91.6 +/- 3.5 degrees) as during defaecation (92 +/- 5.5 degrees). IBS patients with constipation (n = 2) compared to those with normal frequency defaecation (n = 13) showed no significant differences at rest (95 +/- 6 vs 89.8 +/- 4.1 degrees) and during defaecation (100 +/- vs 88.9 +/- 6.4 degrees). Healthy volunteers widened the angle by more than 5 degrees during defaecation. 2) Perineometry: although not significant, patients with IBS had less perineal descent during the simulated defaecation (1.98 +/- 0.37 cm) than healthy subjects (2.1 +/- 0.3 cm). Nevertheless, during squeeze there was significantly less mobility or perineal descent in patients with IBS than in control subjects (0.21 +/- 0.17 vs 0.95 +/- 0.21 cm; P = 0.01)., Conclusions: The findings of this study suggest that patients with IBS as a whole, whether constipation predominant or not, showed changes in pelvic-floor mobility.