Bayes factor analyses of heritability for serum and muscle lipid traits in Duroc pigs

Posted in: Meat Quality, Production by admin on July 29, 2011 | No Comments

Concern about pork quality has increased during last decades. Given the influence of fat content and composition on sensorial, nutritional, and technological variables of pork meat, an accurate knowledge about genetic control of pig lipid metabolism is required. This study focused on providing a broad characterization for serum and meat lipid trait heritability estimates in pigs. Analyses were performed on a population of 370 Duroc barrows and measured the additive polygenic background for the serum concentrations of cholesterol, triglyceride, and low- and high-density lipoproteins at 45 and 190 d of age (at slaughter), as well as intramuscular fat, cholesterol content, and C:12 to C:22 fatty acid content in longissimus thoracis et lumborum and gluteus medius muscles at slaughter. These traits were analyzed under Bayesian univariate animal linear models, and the statistical relevance of heritability estimates was evaluated through Bayes factor (BF); the model with polygenic additive effects was favored when BF >1. All serum lipid traits showed relevant genetic determinism, but the BF reached greater values at 190 d of age. Serum lipid traits displayed moderate modal estimates for heritability that ranged from 0.18 to 0.30. On the other hand, the genetic determinism for meat quality traits showed a heterogeneous behavior with large and less-than-1 BF. In general, longissimus thoracis et lumborum and gluteus medius muscles showed a similar pattern, with strong evidence of polygenic additive effects for intramuscular fat and palmitic, stearic, and cis-vaccenic fatty acids content, whereas oleic and muscle cholesterol content showed moderate to weak BF with moderate heritabilities. Similarly, results regarding linoleic, arachidonic, n-3, and n-6 fatty acids suggested a moderate genetic determinism, but only in gluteus medius muscle. For the remaining traits (myristic and palmitoleic fatty acids in both muscles, along with linoleic, arachidonic, n-3, and n-6 fatty acids in the longissimus thoracis et lumborum muscle), no statistical evidence for genetic control was observed in this study. As a whole, these results confirm the complexity of lipid metabolism in pigs.

For more information the full article can be found at http://jas.fass.org/

Genetics of growth in piglets and the association with homogeneity of body weight within litters

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The objective of this study was to examine the genetic basis of homogeneity in piglets and the genetic correlations with litter size and growth during lactation. Genetic parameters for variation in piglet BW within litters at birth and at 3 wk of age, and in the BW of individual piglets at 3 wk (BW3) were estimated from the Norwegian Landrace nucleus population. Data on BW3 were collected from 146,572 piglets from 14,045 litters in 58 herds. Body weight at birth and at 3 wk of age was recorded for 13,318 piglets from 5 nucleus herds. Litter data were evaluated using multivariate trait models. The heritability estimates for the SD of BW at birth and at 3 wk (SDBW3) were in agreement with the literature (0.10 and 0.08, respectively). The genetic correlation for the number of piglets born alive and the mean BW at 3 wk was negative (−0.40), and the correlation of number of piglets born alive with SDBW3 was close to zero (−0.03). The genetic correlation between the SD of BW at birth and SDBW3 was moderate (0.51). The mean BW at birth was genetically correlated with mean BW at 3 wk (0.59) but was independent of SDBW3 (0.08). The estimates of direct and maternal heritability for BW3 were 0.03 and 0.07, respectively, and the genetic correlation between the 2 components was negative (−0.43). The genetic correlation of SDBW3 with the maternal effect on BW3 was positive and strong (0.66), whereas a negative correlation was found with the direct effect on BW3 (−0.18). These results suggest that it is possible to select for mean BW at birth without an increase in within-litter heterogeneity at 3 wk of age. A more efficient strategy would be to consider both the direct and the maternal effects on BW3 in the genetic evaluation, together with SDBW3. Thus, it is possible to avoid the increase in within-litter heterogeneity that would occur as a result of selection performed at 3 wk on a litter trait such as mean BW.

For more information the full article can be found at http://jas.fass.org/

Impact of lactation length and piglet weaning weight on long-term growth and viability of progeny

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A total of 1,034 pigs produced by breeding PIC sows to 2 different PIC terminal sires were used to create 3 distinct weaning weight populations so that post-weaning growth to 125 kg could be studied. The rearing strategies resulted in BW that ranged from 4.1 to 11.5 kg by 20 d of age. Sows and corresponding litters were allocated to 3 treatments: sow reared (SR; n = 367) for 20 d, sow reared for 14 d (14W; n = 330), and sow reared for 2 d (2W; n = 337). Sows were removed from 2W and 14W groups, but progeny remained in the crates and received milk replacer ad libitum (for 18 and 6 d, respectively) until the contemporary SR pigs were weaned at 20 d of age. The SR pigs (6.49kg) weighed 1.01 kg less than 14W pigs (7.5kg) and 2.26 kg less than 2W pigs (8.75kg). The 14W pigs weighed 1.25 kg less than 2W pigs. Nursery ADG for the 2W group (547 g/d) was 35 g/d less than 14W pigs. The 14W pigs (165 d) required 3 fewer days to reach 125 kg of BW compared with SR pigs. The SR and 14W pigs gained BW 24 and 20 g/d faster in the postnursery period when compared with 2W pigs. The SR and 2W pigs consumed 0.10 and 0.12 kg/d less during this period when compared with 14W pigs (2.32 kg/d). Gain:feed of SR was improved when compared with the 14W and 2W pigs over 167 d of age (0.44 vs. 0.42 and 0.42, respectively). Lean percentage was 0.7% greater in carcasses from SR pigs (55.0%) compared with carcasses from 2W pigs (54.3%) when adjusted to a constant HCW. A study of the effect of weaning weight on days to 125 kg was limited to SR and 14W groups because maternal deprivation compromised the 2W group postweaning growth. Six weaning-weight groups were defined using a normal distribution: 4.6, 5.5, 6.4, 7.3, 8.2, and 9.5 kg. Pigs weighing 5.5 kg at 20 d of age were able to reach 125 kg 8 d sooner (168.8 d) than those weighing 4.6 kg (176.8 d). There was a linear relationship between weaning weight and ADG in the postnursery phase of growth. We conclude that  a weaning weight of less than 5.0 kg imposes the greatest marginal loss in production output for a 20-d weaning and lactation length influences long-term growth, composition of growth, and viability of progeny.

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Selection to reduce residual feed intake in pigs produces a correlated response in juvenile insulin-like growth factor-I concentration

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Data from a selection experiment for residual feed intake (RFI) were used to estimate genetic correlations between measures of efficiency and performance traits with juvenile IGF-I, and to demonstrate direct and correlated responses to selection. The heritability of IGF-I was 0.28 and genetic correlations of IGF-I with feed intake (0.26), backfat (0.52), and feed conversion ratio (0.78) were moderate to large. The estimated and realized genetic correlations between RFI and IGF-I were 0.63 and 0.84. In contrast, genetic correlations between IGFI and lifetime or test period growth did not differ significantly from zero (0.06 and −0.19). Selection for decreased RFI produced a direct response in RFI, as expected, and was accompanied by downward correlated responses in ADFI, juvenile IGFI, backfat, and growth traits, listed in order of decreasing relative magnitude, and an increased loin muscle area. The correlated response in IGF-I to selection on RFI demonstrates that this physiological measure is genetically associated with efficiency, and is thus useful as an early information source to estimate genetic merit for efficiency before performance testing. Decreased juvenile IGF-I is associated with leaner, more efficient animals.

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Influence of benzoic acid and phytase in low-phosphorus diets on bone characteristics in growing-finishing pigs

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In 2 simultaneous experiments (Exp.1 and Exp. 2), the effects of benzoic acid (BA) and phytase (Phy) in low-P diets on bone metabolism, bone composition, and bone stability in growing and growing- finishing pigs were examined. Experiment 1 was conducted with 16 crossbred gilts in the BW range of 25 to 66 kg of BW, whereas in Exp. 2, 32 crossbred gilts (25 to 108 kg of BW) were used. All pigs were individually housed in pens and restrictively fed 1 of 4 diets throughout the experiment. Total P content of the wheat-soybean diets was 4 g/kg (all values on an as-fed basis). The experimental diets were 1) unsupplemented control diet; 2) control diet with 0.5% BA; 3) Phy diet with 750 Phy units (FTU) of Phy/kg and no BA; and 4) PhyBA, control diet with 750 FTU of Phy/kg and 0.5% BA. Blood samples were taken at the beginning of the experiment, wk 3 (only for pigs in Exp. 1), wk 6, and before slaughter to determine P and Ca in serum and concentrations of total alkaline phosphatase, serum crosslaps (marker for bone resorption), and osteocalcin (marker for bone formation). Ash, P, and Ca contents of bones and bone stability were examined using the left metatarsal bones and tibia of the pigs after slaughter. Benzoic acid did not influence any of the blood variables. The addition of Phy increased P concentration in serum from 2.71 to 3.03mmol/L at wk 3 and content of serum crosslaps from 0.39 to 0.45ng/mL at wk 6 and decreased osteocalcin at wk 6 by 160 ng/mL. No long-term effect of diets on serum mineral concentrations, alkaline phosphatase, and bone markers in serum could be detected. Benzoic acid negatively affected Ca content in bones and distal bone mineral density, especially in the younger pigs. In the control diet with 0.5% BA and the control diet with 750 FTU of Phy/kg and 0.5% BA, the CA content in bones and distal bone mineral density were reduced by 6 and 11%, respectively. Throughout the whole growing and finishing period, Phy increased ash, P, and Ca contents in bones by 29.4, 4.8, and 11.6 g/kg of DM, respectively. Bone mineral density and bone mineral content were greater in diets with Phy, as well as breaking strength of tibia (+22%) and metatarsal bones (+27%). The results of this study indicate that for a healthy skeleton, BA should not be used in low-P diets without the addition of Phy.

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Detection of a quantitative trait locus for ham weight with polar over-dominance near the ortholog of the callipyge locus in an experimental pig F2 population

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 The distal part of SSC7, which contains the ortholog to the ovine region encompassing the callipyge locus, was analyzed in a Pietrain F2 resource population comprising more than 2,700 offspring. The aim of the study was to map QTL affecting carcass traits comparable with the callipyge phenotype in sheep. We applied an interval mapping approach using 14 microsatellite markers and detected 3 QTL with small effects. The first QTL affects fat thickness on the middle of the back, with no detectable impact on fat sizes at other places on the back, whereas the second QTL affects side fat thickness. The third QTL influences the ham weight and shows a clear parent-of-origin dependent effect in the form of maternal polar over-dominance. It is not located at the position of the imprinting cluster including the callipyge locus, but 7 cM proximal.

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Maternal and social genetic effects on average daily gain of piglets from birth until weaning

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The aim of this study was to investigate whether there is heritable social variation in ADG from birth until weaning in piglets. Nursing and the establishment of teat order are sources of social interaction among suckling piglets nursed by the same sow. If a heritable social effect is present, but ignored, the selected animals might be the most competitive ones with negative effects on growth of their group mates, resulting in less response to selection than expected. The social interaction model was extended with a maternal component to estimate genetic maternal and social effects. Four different animal models were compared: a basic model with a direct heritable effect only; a social model accounting for direct and social heritable effects; a maternal model with a heritable maternal effect in addition to the basic model; and a social-maternal model accounting for direct, social, and maternal heritable effects. Estimates of direct, maternal, and social heritability were 0.07, 0.06, and around 0.0007, respectively. Total heritable variance, including direct, social, and maternal heritable variance and their covariances ranged from 0.07 to 0.15 of the phenotypic variation. Both maternal models were significantly better than equivalent nonmaternal models. The social model was not significantly better than the basic model, and the social-maternal model was also not significantly better than the maternal model. There was no evidence for heritable social effects among piglets in a group. The generally used maternal model fit the data as well as the social-maternal model. Sufficient cross-fostering is needed to partition social and maternal variation.

Intrauterine crowding decreases average birth weight and affects muscle fiber hyperplasia in piglets

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High prolificacy of sows and increased fetal survival lead to greater incidence of intrauterine crowding (IUC), which may then affect pre- and postnatal development of the progeny. The aim of the study was to assess the impact of IUC, using unilaterally hysterectomized- ovariectomized gilts (UHO), on organ and muscle development of their progeny at birth. In the study, 7 UHO and 7 intact control (Con) Swiss Large White gilts were used. At farrowing, if available, 3 male and 3 female progeny with a low (>0.8 and <1.2 kg), medium (>1.2 and <1.4 kg), and high (>1.6 kg) birth weight (BtW) were killed. Internal organs and brain were weighed, and semitendinosus (STN), psoas major (PM), and rhomboideus (RH) muscles were collected. Histological analyses were performed in PM, RH, and STN (dark and light portion) using myofibrillar ATPase staining after preincubation at pH 10.3. Myosin heavy chain (MyHC) polymorphism was determined in the PM using SDS-PAGE gel electrophoresis. Despite that only one-half of the uterine space was available, litter size was smaller only by 35% inUHO compared with Con gilts. However, UHO progeny tended to be lighter than Con progeny. Theaverage BtW of the selected piglets did not differ between the 2 sow groups, whereas PM and kidneys tended to be lighter in UHO than in Con progeny. Compared with Con progeny, the PM and the STNdark of UHO progeny had fewer secondary and total myofibers as well as fewer primary myofibers in the PM. In the RH, the secondary-to-primary myofiber ratio was smaller in UHO than in Con progeny, whereas the total number of myofibers did not differ. The relative abundance of fetal MyHC was less and that of type I MyHC tended to be greater in UHO than in Con offspring. With increasing BtW, organ and brain weights increased. Muscle cross-sectional area and total number of myofibers in the light portion of the STN were greater in high and medium than in low piglets. In conclusion, IUC reduced hyperplasia of secondary and total myofibers in the STNdark and PM. These effects were independent of the BtW and sex.

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Interaction of Bacillus species and Salmonella enterica serovar Typhimurium in immune or inflammatory signaling from swine intestinal epithelial cells

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Previous research evaluated a laboratory strain of Bacillus licheniformis (BL) in a model swine epithelium and found it exerted anti-inflammatory effects on Salmonella enterica serovar Typhimurium (Sal)-induced secretion of IL-8. The current investigation evaluated the antiinflammatory actions of Bacillus bacteria available commercially as feed additives for the swine industry. Three isolates were obtained from the product, 2 Bacillus subtilis (BS1 and BS3) and 1 BL (BL2). Swine jejunal epithelial IPEC-J2 cells were seeded into wells on permeable membrane supports and allowed to form confluent monolayers. Treatments included apical pretreatment with BL, BS1, BL2, or BS3 for 17 h without Sal, and the same Bacillus treatments but with 108 cfu of Sal added in the final hour of Bacillus incubation. Two additional treatments included negative control wells receiving no bacteria (control) and positive control wells receiving only Sal (10 total treatments). After bacterial incubation, wells were washed and fresh medium containing gentamicin was added. Cells were incubated for an additional 5 h, after which apical and basolateral media were recovered for determination of IL-8 and bacitracin. In addition, inserts with epithelial cells that had received Sal were lysed and lysates were cultured to determine treatment effects on Sal invasion. Exposure to Sal alone provoked an increase in IL-8 secretion from IPEC-J2 cells compared with control wells. Pretreatment with each Bacillus isolate followed by challenge with Sal reduced Sal-induced IL-8 secretion in both the apical and basolateral compartments compared with wells receiving only Sal. The residual presence of bacitracin could be detected only in BL2 and BL2+Sal. Fewer Sal colonies could be cultured from lysates of BL2+Sal than from the Sal, BS1+Sal, and BS3+Sal treatments. Results indicate that B. subtilis and BL have the ability to intervene in secretion of the neutrophil chemoattractant IL-8 from swine intestinal epithelial cells. This effect on chemokine secretion by gastrointestinal epithelial cells in vitro could not be explained solely by reduced invasion of epithelial cells by Sal.

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Impact of piglet birth weight, birth order, and litter size on subsequent growth performance, carcass quality, muscle composition, and eating quality of pork

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The objective of this study was to investigate the relationships among birth weight, birth order, or litter size on growth performance, carcass quality, and eating quality of the ultimate pork product. Data were collected from 98 pig litters and, with the addition of recording birth weight and birth order, farrowing and piglet management were according to normal barn practices. In the nursery and during growout, the pigs received the normal feeding program for the barn and, with the addition of individual tattooing, were marketed as per standard procedure. From 24 litters, selected because they had at least 12 pigs born alive and represented a range of birth weights, 4 piglets were chosen (for a total of 96 piglets) and sent to Agriculture and Agri-Food Canada–Lacombe Research Centre when they reached 120 kg for extensive meat quality and sensory analysis. Individual BW was measured at birth, on the day of weaning, 5 wk after weaning, at nursery exit, at first pull, and at the time of marketing. Litter sizes were divided into 3 categories: small (3 to 10 piglets), medium (11 to 13 piglets), and large (14 to 19 piglets). There were 4 birth-weight quartiles: 0.80 to 1.20, 1.25 to 1.45, 1.50 to 1.70, and 1.75 to 2.50 kg. Increased litter size resulted in reduced mean birth weight, but had no effect on within litter variability or carcass quality when slaughtered at the same endpoint. Lighter birth-weight pigs had reduced BW at weaning, 5 and 7 wk postweaning, and at first pull and had increased days to market. Birth weight had limited effects on carcass quality, weight of primal cuts, objective quality, and overall palatability of the meat at the same slaughter weight. In conclusion, increased litter size resulted in decreased mean birth weight but no change in days to market. Lighter birthweight pigs took longer to reach market. Despite some differences in histological properties, birth weight had limited effects on carcass composition or final eating quality of the pork when slaughtered at the same BW and large litter size resulted in more pigs weaned and marketed compared with the smaller litters. We concluded that based on the conditions of this study, other than increased days to market, there is no reason based on pig performance or pork quality to slow down the goal of the pork industry to increase sow productivity as a means to increase efficiency.

For more information the full article can be found at http://jas.fass.org/