Mitochondrial abundance and function in muscle from beef steers with divergent residual feed intakes

The objective of this study was to evaluate the relationship between muscle mitochondrial function and residual feed intake (RFI) in growing beef cattle. A 56-day feeding trial was conducted with 81 Angus × Hereford steers (initial BW = 378 ± 43 kg) from the University of California Sierra Foothills Research Station (Browns Valley, CA, USA). All steers were individually fed the same finishing ration (metabolizable energy = 3.28 Mcal/kg DM). Average daily gain (ADG), DM intake (DMI) and RFI were 1.82 ± 0.27, 8.89 ± 1.06 and 0.00 ± 0.55 kg/day, respectively. After the feeding trial, the steers were categorized into high, medium and low RFI groups. Low RFI steers consumed 13.6% less DM (P < 0.05) and had a 14.1% higher G : F ratio (P < 0.05) than the high RFI group. No differences between RFI groups were found in age, ADG or BW (P > 0.10). The most extreme individuals from the low and high RFI groups were selected to assess mitochondrial function (n = 5 low RFI and n = 6 high RFI). Mitochondrial respiration was measured using an oxygraph (Hansatech Instruments Ltd., Norfolk, UK). State 3 and State 4 respiration rates were similar between both groups (P > 0.10). Respiratory control ratios (RCRs, i.e., State 3 : State 4 oxygen uptakes) declined with animal age and were greater in low RFI steers (4.90) as compared to high RFI steers (4.26) when adjusted for age by analysis of covariance (P = 0.003). Mitochondrial complex II activity levels per gram of muscle were 42% greater in low RFI steers than in high RFI steers (P = 0.004). These data suggest that skeletal muscle mitochondria have greater reserve respiratory capacity and show greater coupling between respiration and phosphorylation in low RFI than in high RFI steers.     

Review: divergent selection for residual feed intake in the growing pig

This review summarizes the results from the INRA (Institut National de la Recherche Agronomique) divergent selection experiment on residual feed intake (RFI) in growing Large White pigs during nine generations of selection. It discusses the remaining challenges and perspectives for the improvement of feed efficiency in growing pigs. The impacts on growing pigs raised under standard conditions and in alternative situations such as heat stress, inflammatory challenges or lactation have been studied. After nine generations of selection, the divergent selection for RFI led to highly significant (P<0.001) line differences for RFI (−165 g/day in the low RFI (LRFI) line compared with high RFI line) and daily feed intake (−270 g/day). Low responses were observed on growth rate (−12.8 g/day, P<0.05) and body composition (+0.9 mm backfat thickness, P=0.57; −2.64% lean meat content, P<0.001) with a marked response on feed conversion ratio (−0.32 kg feed/kg gain, P<0.001). Reduced ultimate pH and increased lightness of the meat (P<0.001) were observed in LRFI pigs with minor impact on the sensory quality of the meat. These changes in meat quality were associated with changes of the muscular energy metabolism. Reduced maintenance energy requirements (−10% after five generations of selection) and activity (−21% of time standing after six generations of selection) of LRFI pigs greatly contributed to the gain in energy efficiency. However, the impact of selection for RFI on the protein metabolism of the pig remains unclear. Digestibility of energy and nutrients was not affected by selection, neither for pigs fed conventional diets nor for pigs fed high-fibre diets. A significant improvement of digestive efficiency could likely be achieved by selecting pigs on fibre diets. No convincing genetic or blood biomarker has been identified for explaining the differences in RFI, suggesting that pigs have various ways to achieve an efficient use of feed. No deleterious impact of the selection on the sow reproduction performance was observed. The resource allocation theory states that low RFI may reduce the ability to cope with stressors, via the reduction of a buffer compartment dedicated to responses to stress. None of the experiments focussed on the response of pigs to stress or challenges could confirm this theory. Understanding the relationships between RFI and responses to stress and energy demanding processes, as such immunity and lactation, remains a major challenge for a better understanding of the underlying biological mechanisms of the trait and to reconcile the experimental results with the resource allocation theory.     

Mitochondrial abundance and function in skeletal muscle and liver from Simmental beef cattle divergent for residual feed intake

Cellular mitochondrial function has been suggested to contribute to variation in feed efficiency (FE) among animals. The objective of this study was to determine mitochondrial abundance and activities of various mitochondrial respiratory chain complexes (complex I (CI) to complex IV (CIV)) in liver and muscle tissue from beef cattle phenotypically divergent for residual feed intake (RFI), a measure of FE. Individual DM intake (DMI) and growth were measured in purebred Simmental heifers (n = 24) and bulls (n = 28) with an initial mean BW (SD) of 372 kg (39.6) and 387 kg (50.6), respectively. All animals were offered concentrates ad libitum and 3 kg of grass silage daily, and feed intake was recorded for 70 days. Residuals of the regression of DMI on average daily gain (ADG), mid-test BW^0.75 and backfat (BF), using all animals, were used to compute individual RFI coefficients. Animals were ranked within sex, by RFI into high (inefficient; top third of the population), medium (middle third of population) and low (efficient; bottom third of the population) terciles. Statistical analysis was carried out using the MIXED procedure of SAS v 9.3. Overall mean ADG (SD) and daily DMI (SD) for heifers were 1.2 (0.4) and 9.1 (0.5) kg, respectively, and for bulls were 1.8 (0.3) and 9.5 (1.02) kg, respectively. Heifers and bulls ranked as high RFI consumed 10% and 15% more (P < 0.05), respectively, than their low RFI counterparts. There was no effect of RFI on mitochondrial abundance in either liver or muscle (P > 0.05). An RFI × sex interaction was apparent for CI activity in muscle. High RFI animals had an increased activity (P < 0.05) of CIV in liver tissue compared to their low RFI counterparts; however, the relevance of that observation is not clear. Our data provide no clear evidence that cellular mitochondrial function within either skeletal muscle or hepatic tissue has an appreciable contributory role to overall variation in FE among beef cattle.     

Evaluating environmental impacts of selection for residual feed intake in pigs

To identify a proper strategy for future feed-efficient pig farming, it is required to evaluate the ongoing selection scenarios. Tools are lacking for the evaluation of pig selection scenarios in terms of environmental impacts to provide selection guidelines for a more sustainable pig production. Selection on residual feed intake (RFI) has been proposed to improve feed efficiency and potentially reduce the associated environmental impacts. The aim of this study was thus to develop a model to account for individual animal performance in life cycle assessment (LCA) methods to quantify the responses to selection. Experimental data were collected from the fifth generation of pig lines divergently selected for RFI (low line, more efficient pigs, LRFI; high line, less efficient pigs, HRFI). The average feed conversion ratio (FCR) and daily feed intake of LRFI pigs were 7% lower than the average of HRFI pigs (P < 0.0001). A parametric model was developed for LCA based on the dietary net energy fluxes in a pig system. A nutritional pig growth tool, InraPorc®, was included as a module in the model to embed flexibility for changes in feed composition, animal performance traits and housing conditions and to simulate individual pig performance. The comparative individual-based LCA showed that LRFI had an average of 7% lower environmental impacts per kilogram live pig at farm gate compared to HRFI (P < 0.0001) on climate change, acidification potential, freshwater eutrophication potential, land occupation and water depletion. High correlations between FCR and all environmental impact categories (>0.95) confirmed the importance of improvement in feed efficiency to reduce environmental impacts. Significant line differences in all impact categories and moderate correlations with impacts (>0.51) revealed that RFI is an effective measure to select for improved environmental impacts, despite lower correlations compared to FCR. Altogether more optimal criteria for efficient environment-friendly selection can then be expected through restructuring the selection indexes from an environmental point of view.     

Genetic markers on BTA14 predictive for residual feed intake in beef steers and their effects on carcass and meat quality traits

With the high cost of feed for animal production, genetic selection for animals that metabolize feed more efficiently could result in substantial cost savings for cattle producers. The purpose of this study was to identify DNA markers predictive for differences among cattle for traits associated with feed efficiency. Crossbred steers were fed a high‐corn diet for 140 days and average daily feed intake (ADFI), average daily gain (ADG), and residual feed intake (RFI) phenotypes were obtained. A region on chromosome 14 was previously associated with RFI in this population of animals. To develop markers with the highest utility for predicting an animal's genetic potential for RFI, we genotyped additional markers within this chromosomal region. These polymorphisms were genotyped on the same animals (n = 1066) and tested for association with ADFI, ADG and RFI. Six markers within this region were associated with RFI (P ≤ 0.05). After conservative correction for multiple testing, one marker at 25.09 Mb remained significant (P = 0.02) and is responsible for 3.6% of the RFI phenotypic variation in this population of animals. Several of these markers were also significant for ADG, although none were significant after correction. Marker alleles with positive effects on ADG corresponded to lower RFI, suggesting an effect increasing growth without increasing feed intake. All markers were also assessed for their effects on meat quality and carcass traits. All of the markers associated with RFI were associated with adjusted fat thickness (AFT, P ≤ 0.009) and three were also associated with hot carcass weight (HCW, P ≤ 0.003). Marker alleles associated with lower RFI were also associated with reduced AFT, and if they were associated for HCW, the effect was an increase in weight. These markers may be useful as prediction tools for animals that utilize feed more efficiently; however, validation with additional populations of cattle is required.     

Longitudinal analysis of residual feed intake and BW in mink using random regression with heterogeneous residual variance

The aim of this study was to determine the genetic background of longitudinal residual feed intake (RFI) and BW gain in farmed mink using random regression methods considering heterogeneous residual variances. The individual BW was measured every 3 weeks from 63 to 210 days of age for 2139 male+female pairs of juvenile mink during the growing-furring period. Cumulative feed intake was calculated six times with 3-week intervals based on daily feed consumption between weighing’s from 105 to 210 days of age. Genetic parameters for RFI and BW gain in males and females were obtained using univariate random regression with Legendre polynomials containing an animal genetic effect and permanent environmental effect of litter along with heterogeneous residual variances. Heritability estimates for RFI increased with age from 0.18 (0.03, posterior standard deviation (PSD)) at 105 days of age to 0.49 (0.03, PSD) and 0.46 (0.03, PSD) at 210 days of age in male and female mink, respectively. The heritability estimates for BW gain increased with age and had moderate to high range for males (0.33 (0.02, PSD) to 0.84 (0.02, PSD)) and females (0.35 (0.03, PSD) to 0.85 (0.02, PSD)). RFI estimates during the growing period (105 to 126 days of age) showed high positive genetic correlations with the pelting RFI (210 days of age) in male (0.86 to 0.97) and female (0.92 to 0.98). However, phenotypic correlations were lower from 0.47 to 0.76 in males and 0.61 to 0.75 in females. Furthermore, BW records in the growing period (63 to 126 days of age) had moderate (male: 0.39, female: 0.53) to high (male: 0.87, female: 0.94) genetic correlations with pelting BW (210 days of age). The result of current study showed that RFI and BW in mink are highly heritable, especially at the late furring period, suggesting potential for large genetic gains for these traits. The genetic correlations suggested that substantial genetic gain can be obtained by only considering the RFI estimate and BW at pelting, however, lower genetic correlations than unity indicate that extra genetic gain can be obtained by including estimates of these traits during the growing period. This study suggests random regression methods are suitable for analysing feed efficiency and BW gain; and genetic selection for RFI in mink is promising.     

Effects of the Crotalus durissus terrificus snake venom on hepatic metabolism and oxidative stress

Snake venoms present different action mechanisms because of their complex composition, represented mainly by toxins and enzymes. This work aimed to investigate the effects of the Crotalus durissus terrificus(Cdt) venom in the liver. Wistar rats were inoculated intraperitoneally with saline (control) or Cdt venom. After 3, 4, or 6 h, the following parameters were analyzed: (a) hepatic function, (b) oxidative stress parameters, and (c) the metabolism of alanine in the isolated perfused liver. Plasma activities of alanine aminotransferase and aspartate aminotransferase and hepatic glutathione S‐transferase and catalase presented significant elevation in rats inoculated with 300 μg ? kg^?1 Cdt venom. Liver lipoperoxidation was enormously increased by venom doses of 100, 200, and 300 μg ?kg^?1, whereas glutathione S‐transferase was not changed. Perfused livers from rats inoculated with 1500 μg ?kg^?1 venom showed increased production of lactate, pyruvate, and ammonia when alanine was the metabolic substrate. These results demonstrate that the Cdt venom can produce several changes in hepatocytes. The causes of the changes are possibly related to the disequilibrium in the redox homeostasis but also to specific needs of the poisoned organism, for example, an increased supply of lactate and pyruvate in response to an increased activity of the Cori cycle. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 25:195–203, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.20376     

Genome‐wide association analysis of residual feed intake in Junmu No. 1 White pigs

Residual feed intake (RFI) is a measure of feed efficiency. Pigs with low RFI have reduced feed costs without compromising their growth. For marker‐assisted selection, it is helpful to identify genes or genetic markers associated with RFI in animals with improved feed efficiency at an early age. Using Illumina's PorcineSNP60 BeadChip, we performed a pilot genome‐wide association study of 217 Junmu No. 1 white male pigs phenotyped for RFI. Two‐step and one‐step methods were used separately to identify associated SNPs. Both methods obtained similar results. Twelve SNPs were identified as significantly associated with RFI at a Bonferroni adjusted P‐level < 9.7 × 10^?7, and 204 were found to have suggestive (moderately significant) association with RFI at P < 5 × 10^?5. NMBR, KCTD16, ASGR1, PRKCQ, PITRM1, TIAM1 and RND3 were identified as candidate genes for RFI.     

Effect of iron supplementation on oxidative stress and antioxidant status in iron-deficiency anemia

This study was designed to measure the effect of iron supplementation on antioxidant status in iron-deficient anemia, including the time for hemoglobin normalization and at the time of filling of iron body stores. The extent of plasma lipid peroxidation was evaluated by measuring the levels of malondialdehyde and glutathione peroxidase (GSH-Px), and the activities of superoxide dismutase (SOD) and catalase in 63 patients with iron-deficiency anemia before and after 6 wk of iron supplementation and at the time when body iron stores are saturated. After 6 wk of iron supplementation, a significant decrease of oxidative stress was observed in the treated subjects relative to controls (p<0.05). No significant differences existed between treated patients at 6 wk and at the end of the study. The erythrocyte levels of catalase, SOD, and GSH-Px were significantly lower in treated patients relative to controls (p<0.05). These levels increased after 6 wk of supplementation (p<0.05) and showed no significant differences with those at the end of the study.     

Effect of Terminalia chebula aqueous extract on oxidative stress and antioxidant status in the liver and kidney of young and aged rats

We evaluated the preventive effects of Terminalia chebula (T. chebula) aqueous extract on oxidative and antioxidative status in liver and kidney of aged rats compared to young albino rats. The concentrations of malondialdehyde (MDA), lipofuscin (LF), protein carbonyls (PCO), activities of xantione oxidase (XO), manganese‐superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione‐S‐transferase (GST), and glucose‐6‐phosphate dehydrogenase (G6PDH), levels of glutathione (GSH), vitamin C and vitamin E were used as biomarkers. In the liver and kidney of aged animals, enhanced oxidative stress was accompanied by compromised antioxidant defences. Administration of aqueous extract of T. cheubla effectively modulated oxidative stress and enhanced antioxidant status in the liver and kidney of aged rats. The results of the present study demonstrate that aqueous extract of T. cheubla inhibits the development of age‐induced damages by protecting against oxidative stress. Copyright © 2009 John Wiley & Sons, Ltd.     

Compromised antioxidant status and persistent oxidative stress in lung transplant recipients

Oxidative stress may be a key feature, and hence important determinant, of tissue injury and allograft rejection in lung transplant recipients. To investigate this, we determined the antioxidant status (urate, ascorbate, thiols and α-tocopherol) and lipid peroxidation status (malondialdehyde) in bronchoalveolar lavage (BAL) fluid and blood serum of 19 consecutive lung transplant recipients 2 weeks and 1, 2, 3, 6, and 12 months post-surgery. BAL fluid and blood samples from 23 control subjects and blood from 8 patients two days before transplantation were obtained for comparison. Before surgery, the antioxidant status of patients was poor as serum ascorbate and total thiol concentrations were significantly (p < 0.05) lower than control subjects. Two weeks post-surgery, ascorbate and total thiol concentrations were still low and urate concentrations had fallen compared to control subjects (p < 0.01). At this time, BAL fluid urate concentration was higher (p < 0.01), ascorbate concentration was lower (p < 0.01) and reduced glutathione concentrations were similar to control subjects. MDA, a product of lipid peroxidation, was higher (p < 0.01) in both BAL fluid and serum obtained from transplant patients compared to control subjects. During the first 12 months post-surgery, little improvement in antioxidant status or extent of lipid peroxidation was seen in transplant recipients. Regression analysis indicated no difference in serum or BAL fluid antioxidant status in patients with acute rejection compared to those without. In conclusion, lung transplant recipients have a compromised antioxidant status before surgery and it remains poor for at least the first year following the operation. In addition, these patients have elevated MDA concentrations in both their lung lining fluid and blood over most of this time. Oxidative stress is not, however, a sufficiently sensitive endpoint to predict tissue rejection in this group.     

Current knowledge on oxidative stress in hepatic ischemia/reperfusion

Abstract

Ischemia/reperfusion (I/R) injury associated with hepatic resections and liver transplantation remains a serious complication in clinical practice, despite several attempts to solve the problem. The redox balance, which is pivotal for normal function and integrity of tissues, is dysregulated during I/R, leading to an accumulation of reactive oxygen species (ROS). Formation of ROS and oxidant stress are the disease mechanisms most commonly invoked in hepatic I/R injury. The present review examines published results regarding possible sources of ROS and their effects in the context of I/R injury. We also review the effect of oxidative stress on marginal livers, which are more vulnerable to I/R-induced oxidative stress. Strategies to improve the viability of marginal livers could reduce the risk of dysfunction after surgery and increase the number of organs suitable for transplantation. The review also considers the therapeutic strategies developed in recent years to reduce the oxidative stress induced by hepatic I/R, and we seek to explain why some of them have not been applied clinically. New antioxidant strategies that have yielded promising results for hepatic I/R injury are discussed.     

Genomic dissection and prediction of feed intake and residual feed intake traits using a longitudinal model in F2 chickens

Feed efficiency traits (FETs) are important economic indicators in poultry production. Because feed intake (FI) is a time-dependent variable, longitudinal models can provide insights into the genetic basis of FET variation over time. It is expected that the application of longitudinal models as part of genome-wide association (GWA) and genomic selection (i.e. genome-wide selection (GS)) studies will lead to an increase in accuracy of selection. Thus, the objectives of this study were to evaluate the accuracy of estimated breeding values (EBVs) based on pedigree as well as high-density single nucleotide polymorphism (SNP) genotypes, and to conduct a GWA study on longitudinal FI and residual feed intake (RFI) in a total of 312 chickens with phenotype and genotype in the F₂ population. The GWA and GS studies reported in this paper were conducted using β-spline random regression models for FI and RFI traits in a chicken F₂ population, with FI and BW recorded for each bird weekly between 2 and 10 weeks of age. A single SNP regression approach was used on spline coefficients for weekly FI and RFI traits, with results showing that two significant SNPs for FI occur in the synuclein (SNCAIP) gene. Results also show that these regions are significantly associated with the spline coefficients (q₂) for 5- and 6-week-old birds, while GWA study results showed no SNP association with RFI in F₂ chickens. Estimated breeding value predictions obtained using a pedigree-based best linear unbiased prediction (ABLUP) model were then compared with predictions based on genomic best linear unbiased prediction (GBLUP). The accuracy was measured as correlation between genomic EBV and EBV with the phenotypic value corrected for fixed effects divided by the square root of heritability. The regression of observed on predicted values was used to estimate bias of methods. Results show that prediction accuracies using GBLUP and ABLUP for the FI measured from 2^nd to 10^th week were between 0.06 and 0.46 and 0.03 and 0.37, respectively. These results demonstrate that genomic methods are able to increase the accuracy of predicted breeding values at later ages on the basis of both traits, and indicate that use of a longitudinal model can improve selection accuracy for the trajectory of traits in F₂ chickens when compared with conventional methods.     

Divergence for residual feed intake of Holstein-Friesian cattle during growth did not affect production and reproduction during lactation

Residual feed intake (RFI) is the difference between actual and predicted dry matter intake (DMI) of individual animals. Recent studies with Holstein-Friesian calves have identified an ~20% difference in RFI during growth (calf RFI) and these groups remained divergent in RFI during lactation. The objective of the experiment described here was to determine if cows selected for divergent RFI as calves differed in milk production, reproduction or in the profiles of BW and body condition score (BCS) change during lactation, when grazing pasture. The cows used in the experiment (n=126) had an RFI of −0.88 and +0.75 kg DM intake/day for growth as calves (efficient and inefficient calf RFI groups, respectively) and were intensively grazed at four stocking rates (SR) of 2.2, 2.6, 3.1 and 3.6 cows/ha on self-contained farmlets, over 3 years. Each SR treatment had equal number of cows identified as low and high calf RFI, with 24, 28, 34 and 40/11 ha farmlet. The cows divergent for calf RFI were randomly allocated to each SR. Although SR affected production, calf RFI group (low or high) did not affect milk production, reproduction, BW, BCS or changes in these parameters throughout lactation. The most efficient animals (low calf RFI) lost similar BW and BCS as the least efficient (high calf RFI) immediately post-calving, and regained similar BW and BCS before their next calving. These results indicate that selection for RFI as calves to increase efficiency of feed utilisation did not negatively affect farm productivity variables (milk production, BCS, BW and reproduction) as adults when managed under an intensive pastoral grazing system.     

The use of different models for the estimation of residual feed intake (RFI) as a measure of feed efficiency in meat sheep

The concept of residual feed intake (RFI), in determining differences among animals in converting feed into body tissue, was first raised in 1963. Feed efficiency is typically calculated as a function of liveweight gain (LWG) and feed intake (FI). Historically two versions of the same model were proposed, one where FI was adjusted for liveweight (LW) and LWG, and the other where LWG was adjusted for FI and LW. Variation in LWG or FI could then be partitioned into two parts; that which is expected and can be attributed to differences in FI or LWG; and that which is the residual portion, which is the deviation from the expected value based on regression, and therefore not accounted for by differences in FI or LWG. Based on this definition, it is the residual portion which is the measure of efficiency. Both within a livestock industry and between different livestock industries there is no set model for calculating RFI. This paper evaluated four models used to calculate RFI and one model used to calculate residual LWG (RLWG) at a standard level of nutrition. They were the main model currently in use in the Australian beef cattle industry (RFI_B), the original models proposed in 1963 (RFI₁₉₆₃; RLWG₁₉₆₃); a French model which included ultrasound measures of muscle and fat depth (RFI_F) and the use of the Australian feeding standards to calculate predicted intake and thus RFI (RFI_SCA). Using feed intake, liveweight and body composition data generated from the same group of sheep (n = 52) at two ages (6 mo, 13 mo), the relative merits of each model were evaluated and compared to the other models, to determine the most appropriate model to calculate RFI for sheep. For all the models except that used to calculate RLWG, over half of the variation in FI could be explained by the model. The amount of variation in FI accounted for depended on the parameters included and the dataset, with less variation in FI explained by the specific models in the older animals. The RFI_F model, which included measures of body composition, accounted for the greatest proportion of the variation in FI and as such suggests that the inclusion of body composition parameters is likely to more accurately reflect true biological efficiency.