Search

For their glucose supply, ruminants are highly dependent on the endogenous synthesis in the liver, but despite the numerous studies that evaluated hepatic glucose production, very few simultaneously measured hepatic glucose production and uptake of all precursors. As a result, the variability of precursor conversion into glucose in the liver is not known. The present study aimed at investigating by meta-analysis the relationships between hepatic glucose net release and uptake of precursors. We used the FLuxes of nutrients across Organs and tissues in Ruminant Animals database, which gathers international results on net nutrient fluxes at splanchnic level measured in catheterized animals. Response equations were developed for intakes up to 41 g DM intake/kg BW per day of diets varying from 0 to 100 g of concentrate/100 g DM in the absence of additives. The net hepatic uptake of propionate, α-amino-N and l-lactate was linearly and better related to their net portal appearance (NPA) than to their afferent hepatic flux. Blood flow data were corrected for lack of deacetylation of the para-aminohippuric acid, and this correction was shown to impact the response equations. To develop response equations between the availability of precursors (portal appearance and hepatic uptake) and net glucose hepatic release, missing data on precursor fluxes were predicted from dietary characteristics using previously developed response equations. Net hepatic release of glucose was curvilinearly related to hepatic supply and uptake of the sum of precursors, suggesting a lower conversion rate of precursors at high precursor supply. Factors of variation were explored for the linear portion of this relationship, which applied to NPA of precursors ranging from 0.99 to 9.60 mmol C/kg BW per h. Hepatic release of glucose was shown to be reduced by the portal absorption of glucose from diets containing bypass starch and to be increased by an increased uptake of β-hydroxybutyrate indicative of higher body tissue mobilization. These relationships were affected by the physiological status of the animals. In conclusion, we established equations that quantify the net release of glucose by the liver from the net availability of precursors. They provide a quantitative overview of factors regulating hepatic glucose synthesis in ruminants. These equations can be linked with the predictions of portal absorption of nutrients from intake and dietary characteristics, and provide indications of glucose synthesis from dietary characteristics. [ABSTRACT FROM AUTHOR]

Animal's feed efficiency in growing cattle (i.e. the animal ability to reach a market or adult BW with the least amount of feed intake), is a key factor in the beef cattle industry. Feeding systems have made huge progress to understand dietary factors influencing the average animal feed efficiency. However, there exists a considerable amount of animal-to-animal variation around the average feed efficiency observed in beef cattle reared in similar conditions, which is still far from being understood. This review aims to identify biological determinants and molecular pathways involved in the between-animal variation in feed efficiency with particular reference to growing beef cattle phenotyped for residual feed intake (RFI). Moreover, the review attempts to distinguish true potential determinants from those revealed through simple associations or indirectly linked to RFI through their association with feed intake. Most representative and studied biological processes which seem to be connected to feed efficiency were reviewed, such as feeding behaviour, digestion and methane production, rumen microbiome structure and functioning, energy metabolism at the whole body and cellular levels, protein turnover, hormone regulation and body composition. In addition, an overall molecular network analysis was conducted for unravelling networks and their linked functions involved in between-animal variation in feed efficiency. The results from this review suggest that feeding and digestive-related mechanisms could be associated with RFI mainly because they co-vary with feed intake. Although much more research is warranted, especially with high-forage diets, the role of feeding and digestive related mechanisms as true determinants of animal variability in feed efficiency could be minor. Concerning the metabolic-related mechanisms, despite the scarcity of studies using reference methods it seems that feed efficient animals have a significantly lower energy metabolic rate independent of the associated intake reduction. This lower heat production in feed efficient animals may result from a decreased protein turnover and a higher efficiency of ATP production in mitochondria, both mechanisms also identified in the molecular network analysis. In contrast, hormones and body composition could not be conclusively related to animal-to-animal variation in feed efficiency. The analysis of potential biological networks underlying RFI variations highlighted other significant pathways such as lipid metabolism and immunity and stress response. Finally, emerging knowledge suggests that metabolic functions underlying genetic variation in feed efficiency could be associated with other important traits in animal production. This emphasizes the relevance of understanding the biological basis of relevant animal traits to better define future balanced breeding programmes. [ABSTRACT FROM AUTHOR]

Animal proteins are naturally 15N enriched relative to the diet and the extent of this difference (Δ15Nanimal-diet or N isotopic fractionation) has been correlated to N use efficiency (NUE; N gain or milk N yield/N intake) in some recent ruminant studies. The present study used meta-analysis to investigate whether Δ15Nanimal-diet can be used as a predictor of NUE across a range of dietary conditions, particularly at the level of between-animal variation. An additional objective was to identify variables related to N partitioning explaining the link between NUE and Δ15Nanimal-diet. Individual values from eight publications reporting both NUE and Δ15Nanimal-diet for domestic ruminants were used to create a database comprising 11 experimental studies, 41 treatments and individual animal values for NUE (n =226) and Δ15Nanimal-diet (n =291). Data were analyzed by mixed-effect regression analysis taking into account experimental factors as random effects on both the intercept and slope of the model. Diets were characterized according to the INRA feeding system in terms of N utilization at the rumen, digestive and metabolic levels. These variables were used in a partial least squares regression analysis to predict separately NUE and Δ15Nanimal-diet variation, with the objective of identifying common variables linking NUE and Δ15Nanimal-diet. For individuals reared under similar conditions (within-study) and at the same time (within-period), the variance of NUE and Δ15Nanimal-diet not explained by dietary treatments (i.e. between-animal variation plus experimental error) was 35% and 55%, respectively. Mixed-effect regression analysis conducted with treatment means showed that Δ15Nanimal-diet was significantly and negatively correlated to NUE variation across diets (NUE=0.415 −0.055×Δ15Nanimal-diet). When using individual values and taking into account the random effects of study, period and diet, the relationship was also significant (NUE=0.358 −0.035×Δ15Nanimal-diet). However, there may be a biased prediction for animals close to zero, or in negative, N balance. When using a novel statistical approach, attempting to regress between-animal variation in NUE on between-animal variation in Δ15Nanimal-diet (without the influence of experimental factors), the negative relationship was still significant, highlighting the ability of Δ15Nanimal-diet to capture individual variability. Among the studied variables related to N utilization, those concerning N efficiency use at the metabolic level contributed most to predict both Δ15Nanimal-diet and NUE variation, with rumen fermentation and digestion contributing to a lesser extent. This study confirmed that on average Δ15Nanimal-diet can predict NUE variation across diets and across individuals reared under similar conditions. [ABSTRACT FROM AUTHOR]

Animal tissues are naturally 15N enriched relative to their diet and the extent of this difference (Δ15N animal-diet) has been correlated to the efficiency of N assimilation in different species. The rationale is that transamination and deamination enzymes, involved in amino acid metabolism are likely to preferentially convert amino groups containing 14N over 15N. However, in ruminants the contribution of rumen bacterial metabolism relative to animal tissues metabolism to naturally enrich animal proteins in terms of 15N has been not assessed yet. The objective of this study was to assess the impact of rumen and digestion processes on the relationship between Δ15N animal-diet and efficiency of N utilization for milk protein yield (milk N efficiency (MNE); milk N yield/N intake) as well as the relationship between the 15N natural abundance of rumen bacteria and the efficiency of N use at the rumen level. Solid- and liquid-associated rumen bacteria, duodenal digesta, feces and plasma proteins were obtained (n =16) from four lactating Holstein cows fed four different diets formulated at two metabolizable protein supplies (80% v. 110% of protein requirements) crossed by two different dietary energy source (diets rich in starch v. fiber). We measured the isotopic N fractionation between animal and diet (Δ15N animal-diet) in these different body pools. The Δ15N animal-diet was negatively correlated with MNE when measured in solid-associated rumen bacteria, duodenal digesta, feces and plasma proteins, with the strongest correlation found for the latter. However, our results showed a very weak 15N enrichment of duodenal digesta (Δ15N duodenal digesta-diet mean value=0.42) compared with that observed in plasma proteins (Δ15N plasma protein-diet mean value=2.41). These data support the idea that most of the isotopic N fractionation observed in ruminant proteins (Δ15N plasma protein-diet) has a metabolic origin with very little direct impact of the overall digestion process on the existing relationship between Δ15N plasma protein-diet and MNE. The 15N natural abundance of rumen bacteria was not related to either rumen N efficiency (microbial N/available N) or digestive N efficiency (metabolizable protein supply/CP intake), but showing a modest positive correlation with rumen ammonia concentration. When using diets not exceeding recommended protein levels, the contribution of rumen bacteria and digestion to the isotopic N fractionation between animal proteins and diet is low. In our conditions, most of the isotopic N fractionation (Δ15N plasma protein-diet) could have a metabolic origin, but more studies are warranted to confirm this point with different diets and approaches. [ABSTRACT FROM AUTHOR]

The objective of this study was to test whether the greater milk N yield usually observed when feeding diets based on starch versus fiber was the consequence of a higher efficiency of AA use across the mammary gland and whether this effect depended on dietary crude protein (CP) content. Five midlactation multicatheterized Jersey cows were fed 4 isoenergetic diets to provide 2 different carbohydrate compositions (CHO; rich in starch vs. rich in fiber) crossed by 2 different protein levels (12.0 vs. 16.5% CP) and according to a 4 x 4 Latin square design. Blood samples were collected at the end of each treatment period from the mesenteric artery and mammary vein to determine mammary net nutrient fluxes. The nature of nutrients taken up by the mammary gland differed between starch and fiber diets: mammary net uptake of acetate increased with fiber versus starch diets, whereas mammary net uptake and clearance rate of glucose increased with starch versus fiber diets but only at a normal CP level. In addition, the mammary net uptake of total, essential, and branched-chain A A (BCAA) was significantly enhanced (12, 11, and 26% on average, respectively) when feeding starch versus fiber diets, in line with a greater milk protein yield (7% on average) and regardless of the CP level. The conversion efficiency of plasma essential AA into milk protein was improved with starch diets (33.7% on average) compared with fiber diets (27.5% on average). This higher mammary efficiency use of AA with starch diets was accompanied by a greater fractional extraction and clearance rate of AA belonging to group 2 (BCAA, Lys, Thr) by the mammary gland in absence of effects of CHO on either the mammary blood flow or the mammary AA metabolism. The positive effect of starch diets on mammary clearance rate and uptake of BCAA observed in this study was further improved when increasing dietary CP from 12.0 to 16.5%. Concerning the individual AA, Leu was the only whose mammary uptake accounted for a higher proportion of total essential AA in diets based on starch versus fiber and whose mammary uptake to milk output ratio was modified (together with Pro). Diets rich in starch versus fiber improved the mammary AA utilization; however, some CHO x CP interactions on mammary metabolism support the concept of different metabolic pathways by which starch diets improve milk protein yield at the 2 studied CP levels. Results from this study suggest that mammary Leu and glucose metabolism can be modulated by the supply of glucogenic nutrients to the mammary gland. [ABSTRACT FROM AUTHOR]

Objectives Avalanche victims are subjected to a number of physiological stressors during burial. We simulated avalanche burial to monitor physiological data and determine whether wearing head and face insulation slows cooling rate during snow burial. In addition, we sought to compare 3 different types of temperature measurement methods. Methods Nine subjects underwent 2 burials each, 1 with head and face insulation and 1 without. Burials consisted of a 60-minute burial phase followed by a 60-minute rewarming phase. Temperature was measured via 3 methods: esophageal probe, ingestible capsule, and rectal probe. Results Cooling and rewarming rates were not statistically different between the 2 testing conditions when measured by the 3 measurement methods. All temperature measurement methods correlated significantly. Conclusions Head and face insulation did not protect the simulated avalanche victim from faster cooling or rewarming. Because the 3 temperature measurement methods correlated, the ingestible capsule may provide an advantageous noninvasive method for snow burial and future hypothermia studies if interruptions in data transmission can be minimized. [ABSTRACT FROM AUTHOR]

For energy feeding systems for ruminants to evolve towards a nutrient-based system, dietary energy supply has to be determined in terms of amount and nature of nutrients. The objective of this study was to establish response equations of the net hepatic flux and net splanchnic release of acetate, butyrate and β-hydroxybutyrate to changes in diet and animal profiles. A meta-analysis was applied on published data compiled from the FLuxes of nutrients across Organs and tissues in Ruminant Animals database, which pools the results from international publications on net splanchnic nutrient fluxes measured in multi-catheterized ruminants. Prediction variables were identified from current knowledge on digestion, hepatic and other tissue metabolism. Subsequently, physiological and other, more integrative, predictors were obtained. Models were established for intakes up to 41 g dry matter per kg BW per day and diets containing up to 70 g concentrate per 100 g dry matter. Models predicted the net hepatic fluxes or net splanchnic release of each nutrient from its net portal appearance and the animal profile. Corrections were applied to account for incomplete hepatic recovery of the blood flow marker, para-aminohippuric acid. Changes in net splanchnic release (mmol/kg BW per hour) could then be predicted by combining the previously published net portal appearance models and the present net hepatic fluxes models. The net splanchnic release of acetate and butyrate were thus predicted from the intake of ruminally fermented organic matter (RfOM) and the nature of RfOM (acetate: residual mean square error (RMSE)=0.18; butyrate: RMSE=0.01). The net splanchnic release of β-hydroxybutyrate was predicted from RfOM intake and the energy balance of the animals (RMSE=0.035), or from the net portal appearance of butyrate and the energy balance of the animals (RMSE=0.050). Models obtained were independent of ruminant species, and presented low interfering factors on the residuals, least square means or individual slopes. The model equations highlighted the importance of considering the physiological state of animals when predicting splanchnic metabolism. This work showed that it is possible to use simple predictors to accurately predict the amount and nature of ketogenic nutrients released towards peripheral tissues in both sheep and cattle at different physiological status. These results provide deeper insight into biological processes and will contribute to the development of improved tools for dietary formulation. [ABSTRACT FROM PUBLISHER]

• Robustness is a complex trait of importance for livestock production systems. • Short-term feed restriction is relevant to investigate adaptation in suckling cows. • Milk yield and plasma non-esterified fatty acid changes are relevant variables for exploring responses. • Functional data analysis is appropriate for detecting between-cow variability. • Variables resulted from functional data analysis allow the ranking of cows based on their responses. Animal robustness is a complex trait of importance for livestock production systems and genetic selection. Phenotyping is essential for evaluation of the adaptation of different genotypes to changing environments. This study tested an experimental framework to induce marked deviations in the adaptive responses of suckling beef cows and to identify relevant indicators of responses to characterise individual differences in the robustness of cows. The production and metabolic responses of primiparous suckling Charolais cows to two periods of feed restriction (FR , 50% of their net energy requirements) of different durations were monitored. After calving, 13 cows (aged 39 ± 2 months, BW of 680 ± 42 kg at calving) had ad libitum access to a diet composed of hay and supplemented with concentrate to meet their energy and protein requirements. Starting at 54 ± 6 days postcalving, the cows underwent two periods of FR: 4 days of FR (FR4), which was followed by 17 days of ad libitum intake to study the recovery from FR4, and 10 days of FR (FR10), which was followed by 18 days of ad libitum intake to study the recovery from FR10. The milk yield (MY), BW, body condition score and plasma non-esterified fatty acid (NEFA), β-hydroxybutyrate, glucose and urea concentrations were measured before, during and after each FR. Among all measured variables, the MY and NEFA concentrations showed the most significant changes in response to FR. A functional data analysis approach was applied to the MY and NEFA data to model the adaptive responses and extract quantifiable indicators of deviation and recovery. Linear correlations (P < 0.03–0.07) between FR4 and FR10 were found for some indicators describing MY and NEFA levels before and after FR. The overall repeatability of MY and NEFA responses between both FR accounted for 46% based on quartile analysis performed on average responses. Moreover, the variance in both the MY and NEFA variables did not differ significantly between FR4 and FR10, despite a trend for higher variances in FR10. Altogether, (1) the calculated variables derived from the functional data analysis of the time patterns of the MY and NEFA accounted for the differences in the cow responses to FR, and (2) the animal responses appeared to show concordance between FR4 and FR10. In conclusion, short-term FR is a relevant framework for studying productive and metabolic adaptive responses in suckling cows and allows the identification of potential robustness indicators. [ABSTRACT FROM AUTHOR]

Nitrogen emissions from dairy cows can be readily decreased by lowering the dietary CP concentration. The main objective of this work was to test whether the milk protein yield reduction associated with low N intakes could be partially compensated for by modifying the dietary carbohydrate composition (CHO). The effects of CHO on digestion, milk N efficiency (milk N/N intake; MNE) and animal performance were studied in four Jersey cows fed 100% or 80% of the recommended protein requirements using a 4×4 Latin square design. Four iso-energetic diets were formulated to two different CHO sources (starch diets with starch content of 34.3% and NDF at 32.5%, and fiber diets with starch content of 5.5% and NDF at 49.1%) and two CP levels (Low=12.0% and Normal=16.5%). The apparent digestible organic matter intake (DOMI) and the protein supply (protein digestible in the small intestine; PDIE) were similar between starch and fiber diets. As planned, microbial N flow (MNF) to the duodenum, estimated from the urinary purine derivatives (PD) excretion, was similar between Low and Normal CP diets. However, the MNF and the efficiency of microbial synthesis (g of microbial N/kg apparently DOMI) were higher for starch v. fiber diets. Milk and milk N fractions (CP, true protein, non-protein N (NPN)) yield were higher for starch compared with fiber diets and for Normal v. Low CP diets. Fecal N excretion was similar across dietary treatments. Despite a higher milk N ouput with starch v. fiber diets, the CHO modified neither the urinary N excretion nor the milk urea-N (MUN) concentration. The milk protein yield relative to both N and PDIE intakes was improved with starch compared with fiber diets. Concentrations of β-hydroxybutyrate, urea and Glu increased and those of glucose and Ala decreased in plasma of cows fed starch v. fiber diets. On the other hand, plasma concentration of albumin, urea, insulin and His increased in cows fed Normal compared with Low CP diets. This study showed that decreasing the dietary CP proportion from 16.5% to 12.0% increases and decreases considerably the MNE and the urinary N excretion, respectively. Moreover, present results show that at similar digestible OM and PDIE intakes, diets rich in starch improves the MNE and could partially compensate for the negative effects of Low CP diets on milk protein yield. [ABSTRACT FROM PUBLISHER]

N-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) are subject of growing interest as they are of particular relevance for meat quality and human health. However, their content in the muscles of cattle is generally low probably as the complex result of their biosynthesis from dietary n-3 PUFA in the muscle and/or in other tissues/organs and of their subsequent uptake by the muscle. In view of this, this study aimed at understanding whether the changes in the muscle n-3 LCPUFA content, depending on the diet (maize silage v. grass) or the muscle type (Rectus abdominis, RA v.Semitendinosus, ST) in 12 Charolais steers, were related to variations in the gene expression of proteins involved in n-3 LCPUFA biosynthesis or cellular uptake. Tissue fatty acid composition was analysed by gas-liquid chromatography and mRNA abundance of proteins by quantitative real-time PCR. The grass-based diet resulted in a 2.3-fold (P < 0.0002) increase in both RA and ST n-3 LCPUFA content compared with the maize silage-based diet, whereas no difference in the expression of genes involved in n-3 LCPUFA biosynthesis and uptake was observed between diets. ST exhibited a 1.5-fold higher n-3 LCPUFA content than RA (P < 0.003), whereas the gene expression of proteins involved in n-3 LCPUFA biosynthesis and uptake was 1.3- to 18-fold higher in RA than in ST (P < 0.05). In conclusion, diet- or muscle type-dependent changes in the muscle n-3 LCPUFA content of Charolais steers did not seem to be mediated by the gene expression regulation of proteins involved in the biosynthesis or uptake of these fatty acids. [ABSTRACT FROM PUBLISHER]

Carbohydrates are the main source of energy in ruminants. Their site, extent and kinetics of digestion highly impact the amount and profile of nutrients delivered to peripheral tissues, and the responses of the animal, i.e. ingestion, efficiency of production, N and methane excretion, quality of products and welfare. Development of multi-objective feed evaluation systems thus requires a more integrated quantitative knowledge on carbohydrate digestion and yield of terminal products, as well as on their metabolism by splanchnic tissues. The objective of this paper is to review (i) quantitative knowledge on fibre, starch and sugar digestion, volatile fatty acids (VFA) and glucose production and splanchnic metabolism and (ii) modelling approaches which aim at representing and/or predicting nutrient fluxes in the digestive tract, portal and hepatic drainage. It shows that the representation of carbohydrate digestion and VFA yield is relatively homogeneous among models. Although published quantitative comparisons of these models are scarce, they stress that prediction of fibre digestion and VFA yield and composition is still not good enough for use in feed formulation, whereas prediction of microbial N yield and ruminal starch digestion seems to be more satisfactory. Uncertainties on VFA stoichiometric coefficients and absorption rates may partly explain the poor predictions of VFA. Hardly any mechanistic models have been developed on portal-drained viscera (PDV) metabolism whereas a few exist for liver metabolism. A qualitative comparison of these models is presented. Most are focused on dairy cows and their level of aggregation in the representation of nutrient fluxes and metabolism highly differs depending on their objectives. Quantitative comparison of these models is still lacking. However, recent advances have been achieved with the empirical prediction of VFA and glucose production and fluxes through PDV and liver based on the current INRA feed evaluation system. These advances are presented. They illustrate that empirical prediction of ruminal VFA and intestinal glucose production can be evaluated by comparison with measured net portal net fluxes. We also illustrate the potential synergy between empirical and mechanistic modelling. It is concluded that concomitant empirical and mechanistic approach may likely help to progress towards development of multi-objective feed evaluation systems based on nutrient fluxes. [ABSTRACT FROM AUTHOR]

This work set out to establish the response equations for hepatic blood flows in sheep and the contribution of hepatic arterial flow to hepatic venous blood flow due to changes in intake levels at constant diet composition. The FLORA (FLuxes across Organs and tissues in Ruminant Animals) database was used, and meta-analysis performed. The meta-analysis involved selection of published papers, identification of studies, description and coding of the selected dataset and statistical analysis using a covariance model. Meta-analyses were carried out using a within-study approach. To ensure absence of bias, the analysis incorporated interfering variables and factors studied in between-study comparisons. Variables concerned diet composition; qualitative factors concerned the physiological state of the animals and the methods used to measure blood flow. The results obtained showed that hepatic blood flows were positively related to intake in sheep. The magnitude of the response (as indicated by the slope) varied with the level of intake and the blood vessel (portal, hepatic venous or arterial). Nine linear relationships were established for the portal, hepatic venous and arterial blood flows as a function of dry matter intake (DMI) with below- and above-maintenance levels considered separately. Data obtained at below- and above-maintenance levels were considered together and four quadratic relationships were established for hepatic blood flows as a function of DMI. These relationships expressed a strong effect of intake on hepatic blood flows. The contribution of hepatic arterial to hepatic venous blood flow averaged 18.2%, with a wide variability. It did not vary significantly with level of intake. Although in between-study comparisons the arterial/venous blood flow was positively influenced by the organic matter digestibility of the diet, the relationships we obtained were robust. They can be used in models of net hepatic nutrient fluxes to predict variations and absolute values of hepatic blood flows from variations and absolute values of DMI. [ABSTRACT FROM AUTHOR]

Abstract: Chow JW, Millikan TA, Carlton LG, Chae W, Lim Y, Morse MI. Kinematic and electromyographic analysis of wheelchair propulsion on ramps of different slopes for young men with paraplegia. Objective: To gain insight into the biomechanics of upslope wheelchair stroking by examining the changes in kinematic and electromyographic characteristics of wheelchair propulsion over ramps of different slopes. Design: Repeated-measures design. Each subject pushed up a wooden ramp (7.3m long) 3 times at self-selected normal and fast speeds for each of these slopes: 0°, 2°, 4°, 6°, 8°, 10°, and 12°. Setting: A biomechanics laboratory. Participants: Young men (N=10) with paraplegia. Interventions: Not applicable. Main Outcome Measures: Electromyographic activity of extensor carpi radialis, triceps brachii, antero-middle and postero-middle deltoids, pectoralis major, and latissimus dorsi, and stroking kinematics. Results: Forward lean of the trunk increased as the slope increased. The triceps brachii, antero-middle deltoid, and pectoralis major were more active during the push phase, while the postero-middle deltoid was more active during the recovery phase. Both extensor carpi radialis and latissimus dorsi were active throughout a stroke. Major adjustments in stroking kinematics and significant increases in muscle activity occurred at slopes between 4° and 10°. Conclusion: In addition to a decrease in stroking speed, the stroking pattern becomes more compact (decreased push angle and relative recovery time, increased stroke frequency) and the trunk becomes more active with increasing slope. [Copyright &y& Elsevier]

Improved understanding of the genetic and physiological control of quality traits could be helpful for identifying new technological or genetic targets to improve tomato fresh fruit quality and shelf life. This study aimed at screening for genes whose expression varied between lines genetically close but differing for fruit quality, using subtractive and selective hybridization (SSH). A set of 310 unigenes was isolated. The differential expression pattern of the SSH clones between LCx and Levovil, the two lines of the trial, was assessed by macroarray screening, and for 14 of them, by real-time PCR. Their putative functions were identified by BLAST comparison with public EST databases, and were classified on the basis of their function. Thirty nine percent of the unigenes corresponded to proteins which had never been isolated in fruit or with functions in fruit that were not clear or unknown. Among the others, proteins related to oxidative stress responses, calcium-binding proteins, a few cell-wall-related proteins, and several transcription regulators were identified. The SSH unigenes were then compared to the EST set of the tomato array Tom2 developed from public resources. The BLAST comparison revealed that 41% of the unigenes were not included in this set. This result revealed that our study emphasizes genes that would not have been considered with commercially available microarrays, and that constitute new targets for fruit quality control. [Copyright &y& Elsevier]

Tubular aggregates are observed in various muscle disorders and appear as densely packed tubules believed to arise from sarcoplasmic reticulum of striated muscle. They are found both in human skeletal muscle, especially from patients suffering from ‘tubular aggregate myopathy’ and in fast twitch skeletal muscle of the male inbred mouse during aging. In this work, we studied tubular aggregates present in inbred male mouse skeletal muscle using electron microscopy as well as histochemistry and Western blotting with the main markers of the sarcoplasmic reticulum. We show that mouse tubular aggregates include the proteins SERCA 1, sarcalumenin (longitudinal sarcoplasmic reticulum), calsequestrin (terminal cisternae) and RyR1 (junctional sarcoplasmic reticulum). We demonstrate also that 95 and 51 kDa triadin isoforms are present in mouse skeletal muscle and are both components of tubular aggregates. These results support the hypothesis that tubular aggregates form a tubular arrangement of a complete sarcoplasmic reticulum containing the junctional, cisternae and longitudinal components of sarcoplasmic reticulum implicated in calcium homeostasis. During mouse skeletal muscle aging, however, densitometry of Western blots reveals a persistent decrease in the expression of the calcium binding protein calreticulin as well as a continuous increase in calsequestrin-like protein expression which both appear unrelated to the tubular aggregate formation. [Copyright &y& Elsevier]

Identifying animals that are superior in terms of feed efficiency may improve the profitability and sustainability of the beef cattle sector. However, measuring feed efficiency is costly and time-consuming. Biomarkers should thus be explored and validated to predict between-animal variation of feed efficiency for both genetic selection and precision feeding. In this work, we aimed to assess and validate two previously identified biomarkers of nitrogen (N) use efficiency in ruminants, plasma urea concentrations and the 15N natural abundance in plasma proteins (plasma δ15N), to predict the between-animal variation in feed efficiency when animals were fed two contrasted diets (high-starch vs high-fibre diets). We used an experimental network design with a total of 588 young bulls tested for feed efficiency through two different traits (feed conversion efficiency [ FCE ] and residual feed intake [ RFI ]) during at least 6 months in 12 cohorts (farm × period combination). Animals reared in the same cohort, receiving the same diet and housed in the same pen, were considered as a contemporary group (CG). To analyse between-animal variations and explore relationships between biomarkers and feed efficiency, two statistical approaches, based either on mixed-effect models or regressions from residuals, were conducted to remove the between-CG variability. Between-animal variation of plasma δ15N was significantly correlated with feed efficiency measured through the two criteria traits and regardless of the statistical approach. Conversely, plasma urea was not correlated to FCE and showed only a weak, although significant, correlation with RFI. The response of plasma δ15N to FCE variations was higher when animals were fed a high-starch compared to a high-fibre diet. In addition, we identified two dietary factors, the metabolisable protein to net energy ratio and the rumen protein balance that influenced the relation between plasma δ15N and FCE variations. Concerning the genetic evaluation, and despite the moderate heritability of the two biomarkers (0.28), the size of our experimental setup was insufficient to detect significant genetic correlations between feed efficiency and the biomarkers. However, we validated the potential of plasma δ15N to phenotypically discriminate two animals reared in identical conditions in terms of feed efficiency as long as they differ by at least 0.049 g/g for FCE and 1.67 kg/d for RFI. Altogether, the study showed phenotypic, but non-genetic, relationships between plasma proteins δ15N and feed efficiency that varied according to the efficiency index and the diet utilised. [ABSTRACT FROM AUTHOR]

A better assessment of digestible protein and AA flows is required to improve the predictions of animal performance in ruminants (e.g., growth and yields of milk and milk protein). In that respect, 2 recent meta-analyses were conducted in our laboratory to establish the relationships between net portal appearance of AA nitrogen (NPA-AAN) and dietary characteristics either from the National Research Council (Washington, DC) or Institut National de la Recherche Agronomique (INRA; St Genès Champanelle, France). Three prediction equations were selected from these meta-analyses: one equation based only on N intake (NI) and 2 equations based on NI, the intake of neutral detergent fiber, plus the dietary concentration of either total digestible nutrients or digestible organic matter. In the current meta-analysis, 2 new equations were developed to predict NPA-AAN from the estimated supply of metabolizable protein (MP) and the protein truly digestible in the intestine (PDI). The reliability of these 5 equations to predict NPA-AAN was evaluated using an independent database. On average, NPA-AAN predictions based on the supply of MP or PDI had the highest coefficient of determination and the lowest root of mean square prediction error and mean and regression biases compared with predictions based on dietary characteristics, suggesting better reliability with the former. No major difference was detected between NPA-AAN predictions based on parameters from the National Research Council or INRA, except that predictions based on MP had the lowest mean and regression biases. In each equation, mean of residual NPA-AAN (observed NPA-AAN minus predicted values) was lowest and negative for sheep compared with dairy cows, suggesting that NPA-AAN were overpredicted in sheep. Many continuous variables biased NPA-AAN predictions based on NI only, but none of the tested variables biased the predictions based on the supply of MP or PDI, corroborating the better reliability for the prediction equations based on the supply of digestible protein. Of the tested continuous variables, only the dietary concentration of crude protein (CP) biased NPA-AAN predictions based on NI plus dietary characteristics. The NPA-AAN responses to dietary CP concentration were overpredicted as dietary CP concentration increased and underpredicted as CP decreased, suggesting that ruminants were more efficient at converting ingested N into digestible protein when fed low-CP diets compared with high-CP diets. [ABSTRACT FROM AUTHOR]

This study aimed to establish the quantitative relationship between metabolisable energy intake (MEI) and growth performance, carcass tissue composition and internal fat, taking into consideration animal precocity, maturity and tail nature. Data from 67 publications were used in the meta-analysis. Diets were characterized and three classes were identified (low medium and high energy density diets). Breeds were characterized according to tail nature, precocity and maturity stage. Average daily gain (ADG) responded to MEI in all animals weighing less than 60% of their adult weight regardless their precocity or their tail nature. At the same level of MEI, the higher the diet energy density, the higher the ADG. In animals weighing less than 42% of adult weight and receiving a high starch diet, carcass muscle and internal fat responded to MEI. Whereas, for animals that weighed between 43% and 75% of adult weight, increases in MEI influenced carcass adipose tissue. • Response of ADG and carcass quality to energy intake was quantified by metaanalysis. • Maturity stage affects growth and carcass quality response to energy intake in sheep. • ADG increases with energy intake for sheep weighing less than 60% of adult weight. • Carcass muscle and internal fat increase with energy for weight lower than 42% of adult weight. • Carcass fat increases with energy for weight between 43% and 75% of adult weight. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: The coupling between the stimulation of a muscle fibre and the massive intracellular calcium release, that is the molecular basis of muscle contraction, is fulfilled by a macromolecular complex, the calcium release complex (CRC). Exegesis: A very precise molecular architecture is required for CRC correct function, as well as a specific membrane organisation in muscle cells. Conclusion: Several muscle pathologies are associated with mutations in the two calcium channels of the CRC. However, elucidation of mechanisms involved in CRC function are still required to characterise muscle pathologies of unknown origin. [Copyright &y& Elsevier]

Management practices can contribute to improving carcass quality if carcass quality could be simply evaluated under a wide range of conditions. The objective of this study was to derive quantitative relationships between the most accurate (but laborious) measurements of carcass chemical composition and proxy traits easily obtainable at slaughter (yield grade, subcutaneous fat thickness, marbling, ribeye area and hot carcass weight) by meta-analysis. Data from 34 publications using male beef cattle were used to develop and validate the models. The breeds were characterized according to origin, rate of maturity, production purpose and frame size. The results indicated that the changes in carcass fat and protein can be predicted from the yield grade or subcutaneous fat thickness, and hot carcass weight, with prediction errors ranging between 9 and 12%. Including the breed characteristics in the models did not improve the fit. The relationships are applicable to group values of male beef cattle having light and fatty carcasses from early-maturing British breeds. [ABSTRACT FROM AUTHOR]

Five mid-lactation multicatheterized Jersey cows were used in a 4 x 4 Latin square design to investigate whether the increase in milk N yield associated with diets rich in starch versus fiber could originate from changes in the splanchnic AA metabolism and if these changes depended upon the dietary crude protein (CP) content. Four isoenergetic diets were formulated to provide 2 different carbohydrate compositions [diets rich in starch (350 g of starch and 310 g of neutral detergent fiber/kg of dry matter) versus rich in fiber (45 g of starch and 460 g of neutral detergent fiber/kg of dry matter)] crossed by 2 different CP contents (12.0 vs. 16.5% CP). At the end of each treatment period, 6 hourly blood samples were collected from the portal and hepatic veins as well as the mesenteric artery to determine net nutrient fluxes across the portal-drained viscera (PDV), liver, and total splanchnic tissues. Dry matter and calculated energy intake as well as total absorbed energy were similar across treatments. However, the net portal appearance (NPA) of acetate, total volatile fatty acids, and (3-hydroxybutyrate were higher with diets rich in fiber versus starch, whereas that of oxygen, glucose, butyrate, and insulin were lower. Concomitant to these changes, the percentage of N intake recovered as total AA (TAA) in the portal vein was lower for diets rich in fiber versus starch (42.3 vs. 51.4%, respectively), without, however, any difference observed in the NPA of the main AA used as energy fuels by the PDV (Glu, Gln, and Asp). Despite a higher NPA of TAA with starch versus fiber diets, no differences in the net hepatic flux of TAA, essential and nonessential AA were observed, resulting in a higher (+22%) net splanchnic release of AA and, hence, a greater (+7%) milk N yield. The net hepatic flux and hepatic fractional removal of none of the individual AA was affected as the main carbohydrate changed from fiber to starch, except for Gly and Lys, which were higher for the latter. After correcting for differences in NPA of TAA, the net hepatic uptake of TAA tended to be lower with starch versus fiber diets. The higher transfer of N from feed to milk with diets rich in starch is not the consequence of a direct sparing AA effect of glucogenic diets but rather the result of lower energy requirements by the PDV along with a higher microbial N flow to the duodenum. A better AA use by peripheral tissues with starch versus fiber diets was also hypothesized but more studies are warranted to clarify this issue. [ABSTRACT FROM AUTHOR]

This study was conducted to establish how AA supplied in a free form or as protein (casein, CN) affect the whole-body rate of appearance (WB Ra) of glucose, splanchnic and mammary glucose kinetics, and milk lactose secretion in lactating dairy cows. Five Holstein cows fitted with a rumen cannula and permanent indwelling catheters in the abomasum, portal, hepatic, and mesenteric veins, and one mesenteric artery, were used in a Youden square with 4 periods of 14 d each. Cows were fed a hay-based diet providing 100 and 70% of their net energy and metabolizable protein (MP) requirements, respectively. Treatments consisted of abomasal infusions of water (70% of MP requirements: control, Con), free AA (95% of MP requirements: AA1; and 120% of MP requirements: AA2), or CN (95% of MP requirements: CN1). The free AA mixture had the same profile as CN. On d 14 of each period, [6,6-2H2] glucose (25.8 mmol/h) was infused into a jugular vein, and blood samples (n = 8) were taken over 4 h from arterial, portal, hepatic, and mammary sources to measure glucose enrichment and concentration. Splanchnic and mammary plasma flows were determined by downstream dilution of para-aminohippurate and with the Fick principle, respectively. The last 6 milkings of each period were weighed and sampled to measure the yields of milk and components. The AA1 and CN1 treatments were not different for any of the measured parameters. Supplying AA linearly increased glucose WB Ra (AA2 vs. Con: +151 mmol/h) and liver net flux (+149 mmol/h). Utilization of glucose from the plasma compartment by the portal-drained viscera and liver and true portal absorption were not affected by AA supply. From these observations, we suggest that the increased WB Ra was due to increased net hepatic production. The AA from the infusion, in excess of that used to cover the increase in milk protein, were converted to glucose with an apparent efficiency close to 100% of maximum theoretical efficiency. Milk and lactose yields increased linearly with infusions of AA, by 14 and 16% with AA2 treatment, respectively. However, mammary glucose uptake was not significantly altered by AA infusions; this suggests that the mammary gland exerts active control on the uptake and utilization of glucose. For all treatments, the sum of true portal glucose absorption and true hepatic glucose production contributed more than 99% of WB Ra in the lactating cow; this would suggest that renal glucose synthesis makes only a small contribution to WB Ra under these conditions. [ABSTRACT FROM AUTHOR]

Abstract: In a research programme aiming at characterising the energy value of ruminant diets by the net portal energy fluxes in ruminants, the present work focused on the relationships between intakes of both dry matter (DMI) and digestible organic matter (DOMI) and the portal blood flow and the net portal fluxes of oxygen (O2), volatile fatty acids, β-hydroxybutyrate, glucose and lactate in sheep and growing cattle. Response equations were generated, expressed as a function of liveweight (LW), using meta-analysis on published that were compiled into the FLORA (FLux of nutrients through the Organs and tissues of Ruminant Animals) database and that investigated changes in intake at constant dietary metabolisable energy (ME) contents within experimental groups. The experimental groups in the selected data set were predominantly adult sheep (n =17), with nine experimental groups on growing cattle and only one experimental group on lactating dairy cows. Intake range was larger in sheep than in growing cattle (0–35g/d/kg LW versus 0–23g/d/kg LW, respectively), and the types of diets fed also differed, with sheep predominantly being fed forage-rich diets (60% of experimental groups). Blood flow and portal O2 consumption showed curvilinear relationships; however the response equations generated for nutrients were best described by linear relationships. With the exception of glucose net portal flux, 70–95% of variation was explained by the models generated. The magnitude of the response equations was largely different between species, and this may also include differences in diets and/or physiological state between the datasets. Both DMI and DOMI were good predictors of the influence of a change in intake level on net portal fluxes of energy metabolites. Subsequent work needs to focus on the influence of diet composition (i.e., dietary ME content). [Copyright &y& Elsevier]

Central Core Disease is a myopathy resulting generally from a mutation in the RYR1 gene, encoding the skeletal muscle calcium release channel RyR1. No treatment is currently available for this disease. We studied a pathological situation in which an affected child harbors two recessive mutations, resulting in a massive reduction in the RyR1 amount. The paternal mutation inducing the inclusion of a new in frame exon in the mRNA of RyR1, resulted in the insertion of additional amino-acids and destabilization of the protein. We hypothesized that inducing the skipping of this exon would be sufficient to restore RyR1 expression and normalization of calcium releases. We developed U7-AON lentiviral vectors to induce exon-skipping on affected primary muscle cells. The efficiency of the exon skipping at the mRNA level, at the protein level and at the functional level using calcium imaging were evaluated. We observed in these affected primary muscle culture a reduction in the inclusion of the additional exon, an increase in the RyR1 protein expression, and a restoration of normal calcium releases. This study is the first demonstration of the potential of exon skipping for the therapy of Central Core Disease, from the molecular to the functional level. [Copyright &y& Elsevier]