Nutritional strategies to cope with reduced litter weight gain and total tract digestibility in lactating sows.

Twelve lactating sows were used to evaluate the effects of reducing dietary crude protein (CP) (14% vs. 12%) and increasing neutral detergent fibre (NDF) levels (18% vs. 22%) on litter performance, total tract apparent digestibility and manure composition in a 4 × 4 latin square arrangement during a 36-day lactation period. Diets were isoenergetic (2.9 Mcal ME/kg) and had similar total lysine content (0.9%). In addition, a second aim was to compare a reference external marker method (Cr2 O3 ) with an internal feed marker [acid-insoluble ash (AIA)] for the calculation of apparent total tract digestibility of nutrients in lactating sows. The reduction of dietary CP level in lactating sows had no effect on either live-weight or backfat thickness or apparent total tract digestibility of nutrients. However, the piglets' average daily gain (ADG) was reduced in low dietary CP diets, which suggests that sows reduced milk production due to an underestimation of certain essential amino acid requirements (e.g. valine). The increase of dietary NDF level did not affect sow and litter performance. Nevertheless, the total tract apparent digestibility of organic matter, CP and carbohydrates was reduced, and ether extract digestion was increased in high NDF compared to normal NDF diets equally balanced for ME and lysine content. The coefficients of total tract apparent digestibility of nutrients in lactating sows were greater when using AIA compared to Cr2 O3 marker, regardless of dietary CP or NDF level, but their coefficients of variation were lower in the former than in the latter. In lactating sows, a trade-off between litter performance and nutrient digestion is established when reducing dietary CP or increasing NDF levels while maintaining similar lysine content through synthetic amino acids and balancing metabolizable energy through dietary fat sources.

Simulation of dose deposition in stereotactic synchrotron radiation therapy: a fast approach combining Monte Carlo and deterministic algorithms.

A hybrid approach, combining deterministic and Monte Carlo (MC) calculations, is proposed to compute the distribution of dose deposited during stereotactic synchrotron radiation therapy treatment. The proposed approach divides the computation into two parts: (i) the dose deposited by primary radiation (coming directly from the incident x-ray beam) is calculated in a deterministic way using ray casting techniques and energy-absorption coefficient tables and (ii) the dose deposited by secondary radiation (Rayleigh and Compton scattering, fluorescence) is computed using a hybrid algorithm combining MC and deterministic calculations. In the MC part, a small number of particle histories are simulated. Every time a scattering or fluorescence event takes place, a splitting mechanism is applied, so that multiple secondary photons are generated with a reduced weight. The secondary events are further processed in a deterministic way, using ray casting techniques. The whole simulation, carried out within the framework of the Monte Carlo code Geant4, is shown to converge towards the same results as the full MC simulation. The speed of convergence is found to depend notably on the splitting multiplicity, which can easily be optimized. To assess the performance of the proposed algorithm, we compare it to state-of-the-art MC simulations, accelerated by the track length estimator technique (TLE), considering a clinically realistic test case. It is found that the hybrid approach is significantly faster than the MC/TLE method. The gain in speed in a test case was about 25 for a constant precision. Therefore, this method appears to be suitable for treatment planning applications.

Traceability of extensively produced Iberian pigs using visual and electronic identification devices from farm to slaughter.

A total of 351 Iberian pigs with equal numbers of both sexes from 2 commercial farms were used to study the ability of various identification devices to guarantee the traceability required for labeled meat products from Iberian pigs reared under extensive production conditions in Spain. The performance of tattoos, visual ear tags, electronic ear tags, and i.p.-injected transponders of half duplex and full duplex technologies were compared during a production cycle from nursery to slaughter at 15 mo of age (156 +/- 3 kg of BW). No major health reactions to any of the identification methods were detected. Results showed that tattooing was not an adequate identification procedure due to reading difficulties as a consequence of dark skin, soiled appearance, and figure deformation. Ear tag losses and failures were affected by fencing type and increased in one of the farms (20.4 and 15.7% for losses and failures, respectively; P < 0.05) as a consequence of using barbed-wire fences. Ear tag losses decreased when fences changed to stone blocks at 365 d of age. Visual and electronic ear tag losses during transport and slaughter were low (3.7% for visual and 3.1% for electronic tag). Results of injectable transponders during the growing-fattening period were variable and were more readable for the half duplex than for the full duplex i.p. transponders (92.0 vs. 68.7% +/- 1.5; P < 0.05). Handheld transceivers worked properly under extensive conditions, although the body size and skin characteristics of the Iberian breed might limit the performance of reading devices, and the use of transceivers with longer reading distances is recommended. The main problem observed with i.p. transponders was their low recovery rate at slaughter due to the lack of adherence of the transponders to the omentum.

Comparison of visual and electronic identification devices in pigs: slaughterhouse performance.

Traceability during slaughter was studied in 1,581 pigs identified by different devices. Treatments were visual ear tags (n = 1,300), electronic ear tags of different technologies (half-duplex, n = 636; full-duplex, n = 632), and intraperitoneally injected transponders of different technologies (half-duplex 32 mm, n = 645; full-duplex 34 mm, n = 642). Piglets were individually identified at weaning and intensively fed until 100 kg of BW. Pigs were slaughtered in 2 commercial slaughterhouses (including scalding, flaming, and peeling) at different throughputs (450 and 550 pigs/h). Readability during slaughtering was checked visually and using standardized hand-held transceivers. No effect of slaughterhouse was detected (P > 0.05). Ear tag losses in the slaughtering line were similar for visual (3.7%) and half-duplex (3.5%) but were increased for full-duplex (11.5%; P < 0.05). Moreover, electronic failures during slaughtering did not differ (P > 0.05) between ear tags (half-duplex, 1.1%; full-duplex, 0.6%). Intraperitoneally injected transponders were not affected by slaughtering (retention 100%, no failures), and 89.0% of the transponders were manually recovered from the abdominal viscera in the offal trays. The remaining transponders (11.0%) were lost on the floor, but none were found in the carcasses. No differences (P > 0.05) in recovery were observed between intraperitoneal transponders. Considering on-farm and slaughterhouse data, total traceability from farm to carcass release was greater (P < 0.05) for intraperitoneally injected transponders (98.2%) than for ear tags. Between ear tags, the greatest traceability was obtained with visual tags (95.7%), which differed (P < 0.05) from electronic tags (half-duplex, 91.4%; full-duplex, 84.5%; P < 0.05). Intraperitoneally injected transponders were an efficient and reliable identification system for tracing pigs from farm to the end of the slaughter line, allowing the transfer of pig identification to the carcass. Adherence of intraperitoneally injected transponders to the viscera should be improved to reduce risks of loss in the meat chain. A dual system based on intraperitoneally injected transponders and plastic ear tags would allow a redundant and automatic reading system that is efficient and reliable for data management and traceability in the swine industry.

Comparison of visual and electronic identification devices in pigs: on-farm performances.

A total of 1,822 pigs from 2 farms (farm A, n = 1,032; farm B, n = 790) were used to evaluate pig traceability under on-farm conditions by using identification devices (n = 4,434) of different technologies. The devices were visual ear tags (n = 1,533; Model 1, n = 776; Model 2, n = 757), electronic ear tags (n = 1,446; half-duplex, n = 702; full-duplex, n = 744), and intraperitoneally injected transponders (n = 1,455; half-duplex, n = 732; full-duplex, n = 723). A group of 790 pigs wore 3 types of devices, and 1,032 wore 2 devices. Piglets were identified before (wk 1 to 3 of age; farm A) or after (wk 3 to 4 of age; farm B) weaning and intensively fattened until approximately 100 kg of BW. Readability of devices was checked at each farm operation by using standardized handheld transceivers. No negative effects of the identification devices on animal health (mortality rate, 8.4%) or performance were detected. On-farm losses averaged 1.6% for ear tags (visual, 0.8%; half-duplex, 1.9%; full-duplex, 2.7%; P > 0.05) and 1.8% for intraperitoneally injected transponders (half-duplex, 1.7%; full-duplex, 1.9%; P > 0.05). Moreover, 1.4% electronic failures occurred in the electronic ear tags (half-duplex, 2.2%; full-duplex, 0.6%; P < 0.05) but not in the intraperitoneally injected transponders. Final on-farm readability was greater (P < 0.05) for visual ear tags (99.2%) than for electronic ear tags (half-duplex, 95.9%; full-duplex, 96.7%; P > 0.05). Readability for intraperitoneally injected transponders was intermediate (half-duplex, 98.3%; full-duplex, 98.1%; P > 0.05). Electronic devices were in all cases easier and faster to read than the visual ear tags. Visual ear tags and intraperitoneally injected transponders were efficiently retained under conditions of commercial pig farms, which agrees with the minimum values recommended by the International Committee for Animal Recording (> 98%). When readability and reading ease were also included as decision criteria, injectable transponders were preferred.

Quantitative trait locus mapping for meat quality traits in an Iberian x Landrace F2 pig population.

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.

Multivariate analysis of litter size for multiple parities with production traits in pigs: I. Bayesian variance component estimation.

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.

Multivariate analysis of litter size for multiple parities with production traits in pigs: II. Response to selection for litter size and correlated response to production traits.

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.

Correlated response to selection for litter size in pigs: I. Growth, fat deposition, and feeding behavior traits.

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.

QTL mapping for growth and carcass traits in an Iberian by Landrace pig intercross: additive, dominant and epistatic effects.

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.

A QTL on pig chromosome 4 affects fatty acid metabolism: evidence from an Iberian by Landrace intercross.

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.

An investigation of segmentation methods and texture analysis applied to tomographic images of human vertebral cancellous bone.

The goal of this study is to determine architectural and textural parameters on computed tomographic (CT) images, allowing us to explain the mechanical compressive properties of bone. Although the resolution (150 microm) is of the same order of magnitude as the trabecular thickness, this method enables the possibility of perfecting an in vivo peripheral CT system with an acceptable radiation dose for the patient. This study was performed on L2 vertebrae cancellous bone specimens taken after necropsy in 22 subjects aged 47-95 years (mean: 79 years). The segmentation process is a crucial point in the determination of accurate architectural parameters. In this paper the use of two different segmentation methods is investigated, based on an edge enhancement and a region growing approach. The images are compared and the architectural parameters extracted from the images segmented by both methods lead to a quantitative evaluation. The parameters are found to be globally robust towards the segmentation process, although some of them are much more sensitive to the approach used. Highly significant correlations (P < 0.0005) have been obtained between the two segmentation methods for all the parameters, with rho ranging from 0.70 to 0.93. In order to improve the assessment of bone architecture, texture analysis (run length method) was investigated. New features are obtained from an image reduced to 16 grey-levels. Textural parameters in addition to architectural parameters in a multivariate regression model increase significantly (P = 0.01) the prediction of the maximum compressive strength (variation of r2 from 0.75 up to 0.89).

Mechanical properties of ewe vertebral cancellous bone compared with histomorphometry and high-resolution computed tomography parameters.

The goal of the present study was to determine if a high-resolution computed tomography (HRCT) system with 150 microns resolution was sufficient to predict mechanical properties in ewe lumbar vertebrae. To answer this question, we used a triangular comparison between: HRCT; biomechanics (compression and shear tests); and histomorphometry, which was the reference method for the measurements of morphometric parameters. Two dissected lumbar vertebrae (L-4 and L-5) from 32 ewes were used. Both compressive and shear properties correlated significantly with amount of bone and structural parameters evaluated by histomorphometry (bone volume/tissue volume, trabecular thickness, trabecular separation), but no significant correlation was found with the trabecular number. With our shear test involving the trabecular architecture itself more significant correlations were found with the node-strut analysis parameters than from the compressive test. Significant correlations were also found between HRCT and histological parameters (bone volume/tissue volume, bone surface/bone volume, trabecular separation, trabecular number, total strut length, number of nodes, and number of termini). Correlations between HRCT structural parameters and mechanical properties on L-4 were of the same magnitude as the correlations between the histomorphometric structural parameters and mechanical results on L-5 but with the remarkable advantage the HRCT is a noninvasive method. In spite of the resolution (150 microns) of our HRCT system, which entailed mainly an enlargement of the thinnest trabeculae or their loss during the segmentation process, we obtained coherent relationships between mechanical and tomographic parameters. The thinnest trabeculae probably had little effect on the mechanical strength. Also, this type of resolution allows us to consider the possibility of perfecting an in vivo HRCT system. However, physical density and bone mineral density correlated much better with strength than either classical histomorphometric or tomographic parameters. The current conclusion is fairly negative with respect to the ability of HRCT to assess mechanical properties nondestructively as compared with dual-energy X-ray absorptiometry. But, the noninvasive nature of the imaging modality and the capacity for three-dimensional imaging at arbitrary orientation make HRCT a promising tool in the quantitative assessment of cancellous architecture.

High-resolution x-ray computed tomography using a solid-state linear detector.

In this paper we present an original low cost acquisition system for computed tomographic imaging. On the first hand, the use of a linear detector consisting of sensitive elements 0.225 mm × 0.5 mm in size allows one to obtain a resolution of about 150 µm after magnification. Image quality has been assessed in terms of spatial resolution and contrast sensitivity by imaging test objects. The images of in vitro vertebrae acquired by this experimental system show great improvement compared to the images acquired by a conventional medical scanner. On the other hand, an even better resolution (25 µm) has been obtained by using an x-ray sensitive Vidicon camera, and an industrial application is presented with advanced composite materials.

A comparison of the ball, wire, edge, and bar/space pattern techniques for modulation transfer function measurements of linear x-ray detectors.

Actual assessment of the modulation transfer function (MTF) of a physical system requires objective experimental data to be obtained. This paper presents four practical methods for measuring the MTF of a linear x-ray detector. These methods are based on using the ball, wire, edge, and bar/space pattern as stimuli. The measurement procedure and experimental conditions are described in detail. The MTF results obtained with these different techniques are analyzed and compared.

Modulation transfer function evaluation of linear solid-state x-ray-sensitive detectors using edge techniques.

The exact determination of the modulation transfer function (MTF) of a physical system is a persistent problem. We present a practical method of measuring numerically the MTF of linear solid-state x-ray-sensitive detectors. The method is based on the use of edge techniques and allows us to obtain the MTF of a linear detector from its edge-spread function (ESF). ESF measurement techniques are discussed in detail, and calculation of the corresponding MTF's are shown.