Diagnosis of multiple sclerosis using optical coherence tomography supported by explainable artificial intelligence.

BACKGROUND/OBJECTIVES: Study of retinal structure based on optical coherence tomography (OCT) data can facilitate early diagnosis of relapsing-remitting multiple sclerosis (RRMS). Although artificial intelligence can provide highly reliable diagnoses, the results obtained must be explainable. SUBJECTS/METHODS: The study included 79 recently diagnosed RRMS patients and 69 age matched healthy control subjects. Thickness (Avg) and inter-eye difference (Diff) features are obtained in 4 retinal layers using the posterior pole protocol. Each layer is divided into six analysis zones. The Support Vector Machine plus Recursive Feature Elimination with Leave-One-Out Cross Validation (SVM-RFE-LOOCV) approach is used to find the subset of features that reduces dimensionality and optimises the performance of the classifier. RESULTS: SVM-RFE-LOOCV was used to identify OCT features with greatest capacity for early diagnosis, determining the area of the papillomacular bundle to be the most influential. A correlation was observed between loss of layer thickness and increase in functional disability. There was also greater functional deterioration in patients with greater asymmetry between left and right eyes. The classifier based on the top-ranked features obtained sensitivity = 0.86 and specificity = 0.90. CONCLUSIONS: There was consistency between the features identified as relevant by the SVM-RFE-LOOCV approach and the retinotopic distribution of the retinal nerve fibres and the optic nerve head. This simple method contributes to implementation of an assisted diagnosis system and its accuracy exceeds that achieved with magnetic resonance imaging of the central nervous system, the current gold standard. This paper provides novel insights into RRMS affectation of the neuroretina.

Early diagnosis of multiple sclerosis by OCT analysis using Cohen's d method and a neural network as classifier.

BACKGROUND: The consequences of inflammation, demyelination, axonal degeneration and neuronal loss in the central nervous system, typical of the development of multiple sclerosis (MS), are manifested in thinning of the retina and optic nerve. The purpose of this work is to diagnose early-stage MS patients based on analysis of retinal layer thickness obtained by swept-source optical coherence tomography (SS-OCT). METHOD: OCT (Triton® SS-OCT device -Topcon, Tokyo, Japan-) recordings were obtained from 48 control subjects and 48 recently diagnosed MS patients. The following thicknesses were measured on a 45 × 60 grid: retinal nerve fibre layer (RNFL), ganglion cell layer (GCL+), GCL++, retinal thickness and choroid. Using Cohen's d effect size, it was determined the regions and layers with greatest capacity to discriminate between control subjects and patients. Points exceeding the threshold set were used as inputs for an automatic classifier: support vector machine and feed-forward neural network. RESULTS: In MS at clinical onset the layer with greatest discriminant capacity is GCL++ [AUC = 0.83] which exhibits a horseshoe-like macular topographic distribution. It is followed by retina, GCL+ and RNFL; choroidal thicknesses do not provide discriminatory capacity. Using a neural network as a classifier between controls and MS patients, obtains sensitivity of 0.98 and specificity of 0.98. CONCLUSIONS: This work suggest that OCT may serve as an important complementary role to other clinical tests, particularly regarding neurodegeneration. It is possible to characterise structural alterations in retina and diagnose early-stage MS with high degree of accuracy using OCT and artificial neural networks.

A computer-aided diagnosis of multiple sclerosis based on mfVEP recordings.

INTRODUCTION: The aim of this study is to develop a computer-aided diagnosis system to identify subjects at differing stages of development of multiple sclerosis (MS) using multifocal visual-evoked potentials (mfVEPs). Using an automatic classifier, diagnosis is performed first on the eyes and then on the subjects. PATIENTS: MfVEP signals were obtained from patients with Radiologically Isolated Syndrome (RIS) (n = 30 eyes), patients with Clinically Isolated Syndrome (CIS) (n = 62 eyes), patients with definite MS (n = 56 eyes) and 22 control subjects (n = 44 eyes). The CIS and MS groups were divided into two subgroups: those with eyes affected by optic neuritis (ON) and those without (non-ON). METHODS: For individual eye diagnosis, a feature vector was formed with information about the intensity, latency and singular values of the mfVEP signals. A flat multiclass classifier (FMC) and a hierarchical classifier (HC) were tested and both were implemented using the k-Nearest Neighbour (k-NN) algorithm. The output of the best eye classifier was used to classify the subjects. In the event of divergence, the eye with the best mfVEP recording was selected. RESULTS: In the eye classifier, the HC performed better than the FMC (accuracy = 0.74 and extended Matthew Correlation Coefficient (MCC) = 0.68). In the subject classification, accuracy = 0.95 and MCC = 0.93, confirming that it may be a promising tool for MS diagnosis. CONCLUSION: In addition to amplitude (axonal loss) and latency (demyelination), it has shown that the singular values of the mfVEP signals provide discriminatory information that may be used to identify subjects with differing degrees of the disease.

Prevalencia de los factores de riesgo vascular entre los casos con diabetes mellitus tipo 2 y sin diabetes hospitalizados de 2011 a 2013 por accidentes cerebrovasculares / Prevalence of vascular risk factors in patients with and without type 2 diabetes mellitus admitted to hospital for stroke in the 2011-2013 period

Introducción: Los accidentes cerebrovasculares (ACV) y la diabetes tipo 2 (DMT2) representan algunas de las principales causas de morbi-mortalidad en Europa. Objetivo: Describir los factores de riesgo vascular (FRV) de mayor prevalencia entre la población española con diabetes mellitus tipo 2 y sin diabetes que ha sufrido un ingreso hospitalario relacionado con ACV durante el periodo 2011-2013. Material y método: Usando los datos del Conjunto Mínimo Básico de Datos (CMBD) del periodo 2011 - 2013 se ha realizado un estudio epidemiológico observacional descriptivo comparando las prevalencias de los FRV de la población española hospitalizada por un ACV. La muestra se ha estratificado por la existencia o no de un diagnóstico de DMT2. Otras variables estudiadas han sido: mortalidad intrahospitalaria o MIH, duración de la estancia hospitalaria o EH y otras variables clínicas y sociodemográficas. Resultados: La hipertensión resultó el factor de riesgo vascular más prevalente en todos los grupos de población. El sexo femenino, la edad y la DMT2 presentaron una asociación estadísticamente significativa (p<0,05) con la MIH en los ACV. Conclusiones: La HTA es el FRV más común seguido de la hipercolesterolemia en la muestra estudiada. Existen diferencias significativas entre las prevalencias de la HTA en la población con DMT2 y la población sin DMT2. Además, la DMT2 es un factor independiente de riesgo de la MIH en cualquier caso de hospitalización relacionada con ACV

Introduction: Stroke and type 2 diabetes mellitus (T2DM) are among the leading causes of morbidity and mortality in Europe. Objective: To describe the vascular risk factors most prevalent in the Spanish population with and without type 2 diabetes mellitus admitted to hospital for a stroke during the 2011-2013 period. Material and Methods: Using the Spanish Minimum Basic Data Set from 2011 to 2013, a descriptive, observational epidemiological study was conducted comparing the prevalence rates of vascular risk factors in Spanish patients admitted to hospital for stroke. The sample was stratified by the presence or absence of a diagnosis of type 2 diabetes mellitus. Other variables studied included in-hospital mortality, length of hospital stay, and other clinical and sociodemographic variables. Results: Hypertension was the most prevalent vascular risk factor in all population groups. Female sex, age, and T2DM had a statistically significant association (p<0.05) to hospital mortality in stroke. Conclusions: Hypertension was the most common vascular risk factor in the study sample, followed by hypercholesterolemia. There were no differences in prevalence of hypertension between patients with and without T2DM. However, T2DM is an independent risk factor for hospital mortality in any hospitalization for stroke

Prevalence of vascular risk factors in patients with and without type 2 diabetes mellitus admitted to hospital for stroke in the 2011-2013 period. / Prevalencia de los factores de riesgo vascular entre los casos con diabetes mellitus tipo 2 y sin diabetes hospitalizados de 2011 a 2013 por accidentes cerebrovasculares.

INTRODUCTION: Stroke and type 2 diabetes mellitus (T2DM) are among the leading causes of morbidity and mortality in Europe. OBJECTIVE: To describe the vascular risk factors most prevalent in the Spanish population with and without type 2 diabetes mellitus admitted to hospital for a stroke during the 2011-2013 period. MATERIAL AND METHODS: Using the Spanish Minimum Basic Data Set from 2011 to 2013, a descriptive, observational epidemiological study was conducted comparing the prevalence rates of vascular risk factors in Spanish patients admitted to hospital for stroke. The sample was stratified by the presence or absence of a diagnosis of type 2 diabetes mellitus. Other variables studied included in-hospital mortality, length of hospital stay, and other clinical and sociodemographic variables. RESULTS: Hypertension was the most prevalent vascular risk factor in all population groups. Female sex, age, and T2DM had a statistically significant association (p<0.05) to hospital mortality in stroke. CONCLUSIONS: Hypertension was the most common vascular risk factor in the study sample, followed by hypercholesterolemia. There were no differences in prevalence of hypertension between patients with and without T2DM. However, T2DM is an independent risk factor for hospital mortality in any hospitalization for stroke.

A signal-to-noise-ratio-based analysis of multifocal visual-evoked potentials in multiple sclerosis risk assessment.

OBJECTIVE: To study the value of using the signal-to-noise ratio (SNR) of multifocal visual-evoked potentials (mfVEPs) in assessment of subjects at risk of developing multiple sclerosis (MS). METHODS: MfVEP signals were obtained from 15 patients with radiologically isolated syndrome (RIS), from 28 patients with clinically isolated syndrome (CIS), from 28 with clinically definite MS and from 24 control subjects. The CIS and MS groups were divided into two subgroups: those with eyes affected by optic neuritis (ON) and those without (non-ON). The mfVEPs' SNR was obtained for both the whole visual field and at various eccentric rings. The area under the curve (AUC) was calculated by comparing the control subjects' mfVEP SNR values with those of the RIS, CIS and MS groups. RESULTS: In whole visual field analysis, risk of developing MS increased as SNR decreased (SNRCONTROL=0.70, SNRRIS=0.62, SNRCIS-nonON=0.54, SNRCIS-ON=0.40, SNRMS-nonON=0.52, SNRMS-ON=0.40). Ring 5 (9.8°-15° eccentricity) was most affected by the SNR decrease, as indicated by its higher AUC values (AUCFULL_EYE=0.81, AUCRING_5=0.89). A significant relationship (Spearman correlation, ρRING_5=0.61) between SNR values and disability severity on the Expanded Disability Status Scale (EDSS) was observed in clinically definite MS patients. CONCLUSION: A new method based on analysis of the SNR of mfVEP signal amplitude improves assessment of patients at risk of developing MS. SIGNIFICANCE: Improved mfVEP assessment of MS-risk patients was achieved by using SNR values at 9.8°-15° eccentricity of the visual field.

Continuous-wavelet-transform analysis of the multifocal ERG waveform in glaucoma diagnosis.

The vast majority of multifocal electroretinogram (mfERG) signal analyses to detect glaucoma study the signals' amplitudes and latencies. The purpose of this paper is to investigate application of wavelet analysis of mfERG signals in diagnosis of glaucoma. This analysis method applies the continuous wavelet transform (CWT) to the signals, using the real Morlet wavelet. CWT coefficients resulting from the scale of maximum correlation are used as inputs to a neural network, which acts as a classifier. mfERG recordings are taken from the eyes of 47 subjects diagnosed with chronic open-angle glaucoma and from those of 24 healthy subjects. The high sensitivity in the classification (0.894) provides reliable detection of glaucomatous sectors, while the specificity achieved (0.844) reflects accurate detection of healthy sectors. The results obtained in this paper improve on the previous findings reported by the authors using the same visual stimuli and database.

Software for analysing multifocal visual evoked potential signal latency progression.

BACKGROUND: This paper describes a new non-commercial software application (mfVEP(2)) developed to process multifocal visual-evoked-potential (mfVEP) signals in latency (monocular and interocular) progression studies. METHOD: The software performs analysis by cross-correlating signals from the same patients. The criteria applied by the software include best channels, signal window, cross-correlation limits and signal-to-noise ratio (SNR). Software features include signal display comparing different tests and groups of sectors (quadrants, rings and hemispheres). RESULTS: The software's performance and capabilities are demonstrated on the results obtained from a patient with acute optic neuritis who underwent 9 follow-up mfVEP tests. Numerical values and graphics are presented and discussed for this case. CONCLUSIONS: The authors present a software application used to study progression in mfVEP signals. It is also useful in research projects designed to improve mfVEP techniques. This software makes it easier for users to manage the signals and allows them to choose various ways of selecting signals and representing results.

Physical impairments and quality of life of colorectal cancer survivors: a case-control study.

The aim of the study is to determine the physical performance, quality of life and fatigue in colorectal cancer survivors compared with healthy controls. Twenty-three colorectal cancer survivors and 22 matched controls were recruited for this case-control study. Fitness level (muscle trunk flexor endurance test, 6-min walk test, chair sit and reach test and flamingo test) was assessed in both groups. Participants completed the European Organization of Research and Treatment of Cancer, the Quality of Life Questionnaire (QLQ-C30), the Piper Fatigue Scale (PFS) and the International Fitness Scale (IFIS). Significant differences between groups were found for all fitness parameters (P < 0.05). In addition, the anova revealed significant differences in all of the IFIS scores (P < 0.001), PFS (P < 0.01) and functioning scores of the QLQ-C30 (P < 0.05) between colorectal cancer survivors and the control group. The Mann-Whitney U-test showed a significant increase in symptom scores such as fatigue, dyspnoea and diarrhoea in the cancer survivors (P < 0.05). This study shows the existence of perceived and objective deterioration of health-related fitness level, presence of moderate cancer fatigue and reduced perceived quality of life in colorectal cancer survivors compared with healthy controls.

Filtering multifocal VEP signals using Prony's method.

BACKGROUND: This paper describes use of Prony's method as a filter applied to multifocal visual-evoked-potential (mfVEP) signals. Prony's method can be viewed as an extension of Fourier analysis that allows a signal to be decomposed into a linear combination of functions with different amplitudes, damping factors, frequencies and phase angles. METHOD: By selecting Prony method parameters, a frequency filter has been developed which improves signal-to-noise ratio (SNR). Three different criteria were applied to data recorded from control subjects to produce three separate datasets: unfiltered raw data, data filtered using the traditional method (fast Fourier transform: FFT), and data filtered using Prony's method. RESULTS: Filtering using Prony's method improved the signals' original SNR by 44.52%, while the FFT filter improved the SNR by 33.56%. The extent to which signal can be separated from noise was analysed using receiver-operating-characteristic (ROC) curves. The area under the curve (AUC) was greater in the signals filtered using Prony's method than in the original signals or in those filtered using the FFT. CONCLUSION: filtering using Prony's method improves the quality of mfVEP signal pre-processing when compared with the original signals, or with those filtered using the FFT.

Improved measurement of intersession latency in mfVEPs.

PURPOSE: The purpose of the study is to present a method (Selfcorr) by which to measure intersession latency differences between multifocal VEP (mfVEP) signals. METHODS: The authors compared the intersession latency difference obtained using a correlation method (Selfcorr) against that obtained using a Template method. While the Template method cross-correlates the subject's signals with a reference database, the Selfcorr method cross-correlates traces across subsequent recordings taken from the same subject. RESULTS: The variation in latency between intersession signals was 0.8 ± 13.6 and 0.5 ± 5.0 ms for the Template and Selfcorr methods, respectively, with a coefficient of variability CV_TEMPLATE = 15.83 and CV_SELFCORR = 5.68 (n = 18, p = 0.0002, Wilcoxon). The number of analyzable sectors with the Template and Selfcorr methods was 36.7 ± 8.5 and 45.3 ± 8.7, respectively (p = 0.0001, paired t test, two tailed). CONCLUSIONS: The Selfcorr method produces smaller intersession mfVEP delays and variability over time than the Template method.

Growth of body components and carcass composition of Iberian pigs of 10 to 150 kg body weight as affected by the level of feeding and dietary protein concentration.

A total of 211 growing-finishing Iberian (IB) pigs from 4 separate and independent sets of trials were slaughtered at several stages of growth from 10 to 150 kg BW to determine growth and development of chemical and physical components of the cold eviscerated carcass (CC; without head, feet, and tail). Within each set of trials, a factorial arrangement of treatments, involving several concentrations of ideal protein in the diets as 1 factor and 2 or 3 levels of feed intake as the other, was used. The main objective of the present study was to provide information on the relative growth of physical and chemical components of the CC of IB pigs, which differed because of the dietary treatment imposed, involving a wide range of protein-to-energy ratios and feeding levels. Allometric relationships (P < 0.001) were established between the weight of a chemical component in the CC and empty BW or CC weight. Irrespective of the adequacy of the dietary protein-to-energy ratio, the growth coefficient for CC weight relative to empty BW was >1 (P < 0.001), whereas those for protein, water, and ash relative to empty BW or CC weight were <1 (P < 0.001). In contrast, relative growth coefficients >1 (P < 0.001) were obtained for fat mass and total energy, reflecting the increase in fat relative content that occurs with increasing weight. Multiple-regression equations (P < 0.001) were developed using a stepwise procedure, which estimates the chemical (g/kg) or energy (MJ/kg) composition of CC as a function of empty BW, dietary protein-to-energy ratio, and feeding level, expressed as a multiple of the ME required for maintenance. It is concluded that even if the pattern of developmental growth for the IB pig may show some similarities (increased fat content or decreased proportional weight of some primal cuts with BW or age) with that observed for pigs of different genetic background, relevant differences were detected. They are related to a much smaller relative size of the IB pig lean tissues and cuts, their slower rates of growth, and the increased total body fat, with marked changes in its distribution among depots. Consequently, relationships obtained for lean or conventional genotypes are not applicable to the IB pig.

Evolution of the fatty acid profile of subcutaneous back-fat adipose tissue in growing Iberian and Landrace × Large White pigs.

The lipid content and fatty acid (FA) profile in pig tissues are strongly influenced by genotype and nutrient supply, with implications in meat quality. The de novo lipid synthesis and pattern of FA unsaturation could be an important cause of variation in the overall efficiency of energy utilization among breeds. To test the effects of pig genotype and CP supply on the evolution of back-fat tissue FA profile throughout the growing and finishing stages, 32 Iberian (IB) and Landrace × Large White (LR × LW) barrows were offered one of two diets differing in CP content (13% or 17% as fed). A pair-fed procedure (0.8 × ad libitum intake of IB pigs) was used. Subcutaneous fat samples were taken at the dorso-lumbar region at ∼38, 50, 65, 90 and 115 kg BW. Higher proportions of total monounsaturated FA (MUFA; P < 0.01) and lower proportions of total saturated FA (SFA; P < 0.01 to 0.05) were found in the outer back-fat layer of pigs both at 50 and 115 kg BW. Pig genotype affected the FA composition of both subcutaneous back-fat layers. The proportions of C18:0 and SFA in fat tissue were higher in IB than in LR × LW pigs from 38 to 65 kg BW, especially in the outer layer. In addition, MUFA contents were higher in IB pigs at 115 kg BW in both layers (+5% on average; P < 0.01). Increased proportions of C18:2 n-6 and polyunsaturated FA (PUFA) were found in LR × LW pigs, irrespective of the stage of growth and back-fat layer (P⩽0.02). At 50 kg BW, pigs receiving the high-protein diet presented the highest C18:2 n-6, C18:3 n-3, C20:5 n-3 and PUFA contents. A significant genotype × CP content interaction was observed for C18:3 n-3 because of the increased concentration of this FA in LR × LW pigs when offered the 17% CP diet (P < 0.05). Higher C16:0 and SFA contents (+5%; P = 0.03) were found in pigs offered the 13% CP diet and slaughtered at 115 kg BW. There was a genotype × CP interaction for MUFA concentration because of the higher MUFA content observed in IB pigs offered the highest protein content diet (P = 0.03). Our results suggest that genetic variation in de novo lipid synthesis and pattern of FA unsaturation might contribute to explain differences in back-fat FA profile of IB and LR × LW pigs under identical nutritional management. They could be also relevant to explain the low efficiency of nutrient and energy utilization in the IB pig.

Response analysis of the Iberian pig growing from birth to 150 kg body weight to changes in protein and energy supply.

A total of 251 growing-finishing Iberian (IB) pigs, 32 of which were suckling piglets, were used in 5 separate sets of trials. The comparative slaughter procedure was used to determine nutrient and energy retention at several stages of growth from birth to 150 kg BW. A factorial arrangement was used within each set of trials, involving several concentrations of ideal protein in the diets as 1 factor and 2 or 3 levels of feed intake as the other. The main objective of these studies was to derive the optimal protein-to-energy ratio in the diet to allow for the expression of maximum protein deposition rates. The effect of feed restriction on growth performance, protein deposition, and fat deposition was also assessed. According to allometric equations, empty BW (EBW) was related to whole body components or total chemical constituents of empty body mass (P < 0.001). For pigs receiving solid feed, highly statistically significant multiple regression equations were constructed, which derived nutrient (g/kg) or energy (MJ/kg) composition as a function of EBW, dietary protein-to-energy ratio, and level of feeding (P < 0.001). In pigs offered adequate protein-to-energy diets, ADG at each stage of production was predicted as a function of the average BW and feeding level (P < 0.001). It was observed that the estimates of ME required for maintenance and net efficiency of utilization of ME for growth change were within rather narrow ranges throughout the growth stages studied. Preferred values (413 kJ/kg BW(0.75) × d(-1) and 0.593 for ME(m) and k(g), respectively) were obtained by regressing total energy retention (kJ/kg BW(0.75) × d(-1)) against ME intake (kJ/kg BW(0.75) × d(-1)). A multiple-regression approach revealed that in the IB pig, ME costs for protein deposition and fat deposition reach 60 and 62 kJ/g, which is considerably greater than in conventional or lean pig genotypes. In the IB pig, the maximum daily rate of protein deposition (PD(max), g) seemed to follow a linear-plateau shape with a breaking point at 32.5 kg BW, beyond which PD(max) remained at an average rate of 75 g × d(-1). The marginal efficiency of body protein deposition was estimated at each growth stage. In pigs fed on optimal or suboptimal protein-to-energy diets, the relationship between PD and ME intake declined, following a curvilinear pattern with increasing BW; thus, implying relative increases in lipid gain as BW increased.

mfERG_LAB: Software for processing multifocal electroretinography signals.

The multifocal electroretinography technique consists of performing sectorized light excitation of the retina and capturing the resulting evoked potential. This provides functional localized information about the state of the retinal neurons. Analysis of multifocal electroretinography signals can be used for diagnosing different types of optic neuropathies (glaucomatous, demyelinating and ischemic ethiology). In order to obtain a reliable diagnosis, it is necessary to apply advanced processing algorithms (morphological, frequency and time-frequency analysis, etc.) to the multifocal electroretinography signal. This paper presents a software application developed in MATLAB(®) (MathWorks Inc., MA) designed to perform advanced multifocal electroretinography signal analysis and classification. This intuitive application, mfERG_LAB, is used to plot the signals, apply various algorithms to them and present the data in an appropriate format. The application's computational power and modular structure make it suitable for use in clinical settings as a powerful and innovative diagnostic tool, as well as in research and teaching settings as a means of assessing new algorithms.

Effects of pig genotype (Iberian v. Landrace × Large White) on nutrient digestibility, relative organ weight and small intestine structure at two stages of growth.

Although the effects of pig genotype on total-tract apparent digestibility (TTAD) have been widely reported in the literature, there is controversial information on the digestive capacity of indigenous breeds compared with lean-type pigs. The strategy of this study was to test the effects of pig genotype and crude protein (CP) supply on performance, digestive utilization of nutrients, relative organ weight and morphometric analysis of the small intestine. Thirty-eight Iberian (IB) and Landrace × Large White (LD) pigs were used. Three pigs per genotype were slaughtered at approximately 15 kg BW. The remaining pigs were fed one of two diets differing in CP content (13% or 17% as fed) using a pair-fed procedure. Feeding level was restricted at 0.8 × ad libitum of IB pigs. Nutrient digestibility and nitrogen (N) balance trials were performed at 30 and 80 kg BW. Four pigs per dietary treatment and genotype were slaughtered at approximately 50 and 115 kg BW. The gastrointestinal tract and the rest of the visceral organs were weighed and samples of the small intestine were taken to carry out histological and histometrical studies. Daily gain and gain-to-feed ratio were higher in LD than in IB pigs during the fattening and growing-fattening periods (P < 0.01). N TTAD was significantly higher for LD pigs at 30 kg BW (P < 0.05), whereas at 80 kg BW we observed greater values for digestibility of organic matter and energy in IB pigs (averaging 1.5%, P < 0.01). Both N retention (NR) and efficiency of NR were increased in LD pigs at 30 and 80 kg BW (30% as mean value). The proportional weight of the small intestine was greater in LD than in IB pigs at 50 and 115 kg BW. Histometry showed that IB presented a lower muscle layer thickness than LD pigs in ileum, irrespective of the BW (P < 0.05). In contrast, LD pigs showed approximately 10% higher ileal villi length and villi-to-crypt ratio than IB pigs at 115 kg BW. CP supply affected to a larger extent the small intestinal micro-anatomical structure of LD pigs at 50 kg BW. In conclusion, our results suggests that although the higher growth rate, NR and efficiency of NR observed in LD pigs might be associated with presumably more efficient structural aspects of the small intestine, the main differences between the two genotypes should be attributed to a larger extent to protein and energy utilization in tissues with consequences for the overall efficiency of energy use.

Response of piglets to the valine content in diet in combination with the supply of other branched-chain amino acids.

The branched-chain amino acids (BCAA) valine (Val) and isoleucine (Ile) are considered to be among the next-limiting amino acids for growth in piglets. In earlier studies, we estimated the standardized ileal digestible (SID) Val : Lys (lysine) requirement to be at least 70%, whereas the Ile : Lys requirement may be as low as 50%. Because the BCAA partially share a common route of catabolism, the supply of one BCAA may affect the availability of the other BCAA. Four experiments were conducted to determine the response of 6-week-old piglets to the Val supply in relation to the other BCAA. A deficient supply of Val or Ile typically results in a reduction in average daily feed intake (ADFI). Experiment 1 was designed to determine the effect of a limiting Val supply, independent of the effect on feed intake. In a dose-response study using restrictively fed piglets, nitrogen retention did not increase for an SID Val : Lys supply greater than 64%. In the remaining experiments, piglets were offered feed ad libitum using ADFI, average daily gain (ADG) and gain-to-feed ratio as response criteria. The interaction between the Val and leucine (Leu) was studied in Experiment 2 in a 2 × 2 factorial design (60% and 70% SID Val : Lys, and 111% and 165% SID Leu : Lys). Performance was considerably lower in piglets receiving 60% Val : Lys compared with those receiving 70% Val : Lys and was lowest in piglets receiving the diet with low Val and high Leu content. To further evaluate the interaction between Val and Leu, a dose-response study was carried out in which the response to Val supply was studied in combination with high Leu supply (165% Leu : Lys). Using a curvilinear-plateau model, the average SID Val : Lys requirement was 72%. However, low Val supply (60% SID Val : Lys) reduced performance by 13% to 38%, which was much greater than what we observed in earlier studies. Experiment 4 was carried out to test the hypothesis that the Val requirement is not affected by low Ile supply (50% SID Ile : Lys). Performance was not improved for Val : Lys supplies greater than 65%, which may indicate that Ile (and not Lys) was second-limiting in this study. In conclusion, the first response of piglets to deficient Val supply appears to be a reduction in ADFI, rather than a reduction in ADG or nitrogen retention. A large supply of Leu may not affect the Val requirement per se, but may aggravate the consequences of Val deficiency.

Energy utilization in pigs selected for high and low residual feed intake.

Genetic selection on residual feed intake (RFI) can be used as an alternative method to G:F to improve feed efficiency in pigs. The objective of this study was to determine the effects of selection for RFI on digestive and metabolic utilization of energy in 2 lines of purebred French Large White castrated male pigs obtained from a divergent selection experiment over 6 generations. The RFI(+) (high RFI) line consumed more feed than predicted from performance compared with the RFI(-) (low RFI) line. Digestibility of energy and nutrients, total heat production (HP), HP related to physical activity, and energy and N balance were measured in respiration chambers for a 6-d period in pigs offered feed ad libitum. Pigs remained in the chamber for an additional day and did not receive any feed to estimate the fasting HP and calculate the thermic effect of feeding. Five pairs of 2 littermates from the same farrowing batch were used in each line. Because 2 respiration chambers were available for the trial, pigs were measured regularly during the 25- to 95-kg growing period. Two pigs per chamber were used until pigs reached 45 kg of BW, and 1 pig per chamber was used thereafter. Individual feed intake and BW gain were measured continuously from weaning to the end of the trial. Pigs were fed 3 diets with decreasing CP contents during the 25 to 45 (period 1), 45 to 65 (period 2), and 65 to 95 (period 3) kg of BW periods. Average daily feed intake was greater in RFI(+) pigs than in RFI(-) pigs between 25 and 65 kg of BW (2,128 vs. 1,891 g/d; P < 0.01) and G:F was 8% greater in RFI(-) pigs compared with RFI(+) pigs (P < 0.01). There was no line effect on digestibility coefficients or N retention, irrespective of the experimental period studied. Nitrogen retention was 31.2, 28.7, and 20.8 g/d at periods 1, 2, and 3, respectively (P < 0.001). The HP was greater in RFI(+) pigs than in RFI(-) pigs (1,497 vs. 1,383 kJ.kg of BW(-0.60).d(-1); P < 0.01), with no subsequent line effect on energy retention. The activity-related HP tended to be greater in RFI(+) pigs than in RFI(-) pigs (250 vs. 218 kJ.kg of BW(-0.60).d(-1); P = 0.09), and the fasting HP was 10% greater (P = 0.04) in RFI(+) pigs than in RFI(-) pigs (846 vs. 771 kJ.kg of BW(-0.60).d(-1)). The thermic effect of feeding, expressed as a percentage of ME intake, was the same for both lines of pigs (average, 14.7%). In conclusion, the RFI(+) pigs are energetically less efficient because of their greater HP related to physical activity and basal metabolic rate.

A sulfur amino acid deficiency changes the amino acid composition of body protein in piglets.

Experiments carried out to determine the amino acid requirement in growing animals are often based on the premise that the amino acid composition of body protein is constant. However, there are indications that this assumption may not be correct. The objective of this study was to test the effect of feeding piglets a diet deficient or not in total sulfur amino acids (TSAA; Met + Cys) on nitrogen retention and amino acid composition of proteins in different body compartments. Six blocks of three pigs each were used in a combined comparative slaughter and nitrogen balance study. One piglet in each block was slaughtered at 42 days of age, whereas the other piglets received a diet deficient or not in TSAA for 19 days and were slaughtered thereafter. Two diets were formulated to provide either 0.20% Met and 0.45% TSAA (on a standardized ileal digestible basis) or 0.46% Met and 0.70% TSAA. Diets were offered approximately 25% below ad libitum intake. At slaughter, the whole animal was divided into carcass, blood, intestines, liver, and the combined head, tail, feet and other organs (HFTO), which were analyzed for nitrogen and amino acid contents. Samples of the longissimus muscle (LM) were analyzed for myosin heavy chain (MyHC) and actin contents. Nitrogen retention was 20% lower in piglets receiving the TSAA-deficient diet (P < 0.01). In these piglets, the nitrogen content in tissue gain was lower in the empty body, carcass, LM and blood (P < 0.05) or tended to be lower in HFTO (P < 0.10), but was not different in the intestines and liver. The Met content in retained protein was lower in the empty body, LM and blood (P < 0.05), and tended to be lower in the carcass (P < 0.10). The Cys content was lower in LM, but higher in blood of piglets receiving the TSAA-deficient diet (P < 0.05). Skeletal muscle appeared to be affected most by the TSAA deficiency. In LM, the Met content in retained protein was reduced by 12% and total Met retention by more than 60%. The MyHC and actin contents in LM were not affected by the TSAA content of the diet. These results show that a deficient TSAA supply affects the amino acid composition of different body proteins. This questions the use of a constant ideal amino acid profile to express dietary amino acid requirements, but also illustrates the plasticity of the animal to cope with nutritional challenges.

The standardized ileal digestible isoleucine-to-lysine requirement ratio may be less than fifty percent in eleven- to twenty-three-kilogram piglets.

Most studies concerning the Ile requirement in pigs have been carried out using blood products as a protein source, and these have a relatively low Ile content relative to the other branched-chain AA (BCAA). There are indications that an excess supply of one BCAA can affect the utilization of the other BCAA. Little information is available concerning the Ile requirement in pigs when the supply of the other BCAA is moderate (e.g., in cereal- and soybean meal-based diets). The objective of the present study was to evaluate the response of piglets to Ile supplementation under different nutritional conditions. In all experiments, piglets were housed individually and had ad libitum access to feed during a 3-wk period. The first experiment was carried out to study the response of piglets to an increasing Ile supply by using 2 sources of l-Ile differing in degree of purity. Piglets received either a control diet with 48% standardized ileal digestible (SID) Ile:Lys or 1 of 4 other diets containing graded levels of either source of l-Ile to provide 52 or 56% SID Ile:Lys. All diets were formulated to provide 1.00% SID Lys in the diet. Feed intake and growth were not affected by Ile level or Ile source. Experiment 2 was performed to exclude a possible interaction between Ile and Lys supply. In a 2 x 2 factorial arrangement, 2 levels of Lys (1.00 and 1.15% SID Lys) and 2 levels of Ile (48 and 60% SID Ile:Lys) were used. Growth and G:F were 8 and 7% greater in piglets receiving the diet with the greater Lys content, but the Ile:Lys did not affect performance. No interactions were observed between the Lys and Ile supplies. In Exp. 3, a 2 x 2 factorial arrangement was used to test the effect of protein source (spray-dried blood cells or corn gluten meal) and Ile supply (50 or 65% SID Ile:Lys) on performance in piglets. Both protein sources had an elevated BCAA content but differed in Leu and Val contents. Protein source or Ile supply did not affect feed intake, growth, or G:F in the piglets. Plasma concentrations after an overnight fast reflected the difference in AA concentrations of the diets. In conclusion, the results of these experiments indicate that the SID Ile:Lys requirement may be not greater than 50% in piglets receiving cereal- and soybean meal-based diets with a moderate BCAA content. In contrast to other studies, we could not confirm that the Ile requirement was affected by BCAA content of the diet.