The effect of feeding animals ad libitum versus at maintenance level on the in vivo digestibility of two permanent grasslands across the first cycle of growth

International audienceThe aim of this experiment was to study the effect of feeding level (FL) on the digestibility of unconserved forage obtained from two permanent grasslands cut at three different dates during the first cycle of growth. Forage was offered to Texel sheep (wethers), at maintenance level and at ad libitum level. Differences in voluntary intake (VI) between grasslands were also tested. Organic matter digestibility (OMD) measured at ad libitum level and at VI was 13% higher on harvested forage from grassland rich in forbs (GRF) than grassland rich in grasses (GRG) at early herbage growth stages, but these differences were no longer found at later maturity stages. In GRF, there were no differences for OMD, at either FL at the young growth stages, but at the end of the cycle the OMD obtained at ad libitum level (0·56) was higher than that at maintenance level (0·50). However, in GRG, at an early stage of forage maturity, OMD at ad libitum level (0·67) was lower than that at maintenance level (0·70), but this difference was no longer found at the end of the growth cycle. In conclusion, the effect of FL on the digestibility of unconserved forage from permanent grasslands depends on the type of grassland. These differences are mainly explained by the different botanical composition of the grassland types

Near infrared reflectance spectroscopy to predict energy value of compound feeds for swine and ruminants

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Mixing sainfoin and lucerne to improve the feed value of legumes fed to sheep by the effect of condensed tannins

International audienceThe aim of this study was to investigate whether the use of sainfoin-based condensed tannins (CT) enhances feed value when given with tannin-free legumes (lucerne) to sheep. The experiments were conducted with fresh sainfoin and lucerne harvested at two stages (vegetative stage as compared with early flowering) in the first growth cycle. Fresh sainfoin and lucerne forages were combined in ratios of 100 : 0, 75 : 25, 25 : 75 and 0 : 100 (denoted S100, S75, S25 and S0, respectively). Voluntary intake, organic matter digestibility (OMD) and nitrogen (N) retention were measured in sheep fed the different sainfoin and lucerne mixtures. Loss of dry matter (DM) and N from polyester bags suspended in the rumen, abomasum and small intestine (SI) was also measured using rumen-fistulated sheep and intestinally fistulated sheep. The CT content in sainfoin (S100) decreased with increasing percentage of lucerne in the mixture (mean value from 58 g/kg DM for S100 to 18 g/kg DM for S25) and with growth stage (S100: 64 to 52 g/kg DM). OMD did not differ between different sainfoin/lucerne mixture ratios. Sainfoin and lucerne had an associative effect (significant quadratic contrast) on voluntary intake, N intake, total-tract N digestibility, N in faeces and urine (g/g N intake) and N retained (g/g N intake). Compared with lucerne mixtures (S0 and S25), high-sainfoin-content mixtures (S100 and S75) increased the in situ estimates of forage N escaping from the rumen (from 0.162, 0.188 for S0 and S25 to 0.257, 0.287 for S75 and S100) but decreased forage N intestinal digestibility (from 0.496, 0.446 for S0 and S25 to 0.469, 0.335 for S75 and S100). The amount of forage N disappearing from the bags in the SI (per g forage N) was the highest for high-sainfoin mixtures (from 0.082, 0.108 for S100 and S75 to 0.056, 0.058 for S25 and S0, P inférieur à 0.001). Rumen juice total N (tN) and ammonia N (NH3-N) values were the lowest in the high-sainfoin diet (mean tN 0.166 mg/g in S100 as compared with 0.514 mg/g in S0; mean NH3-N 0.104 mg/g in S100 as compared with 0.333 mg/g in S0, P inférieur à 0.001)

Estimation of organic matter digestibility of whole maize plants by laboratory methods

International audienc

Une démarche intégrée pour prévoir la valeur des aliments pour les ruminants : PrévAlim pour INRAtion

National audienceThis paper presents the bases of an integrated tool developed to estimate the feed value of forages and concentrates from their laboratory analysis. The computer program PrevAlim, available with the new version of INRAtion software, calculates the nutritive value of feed (feed unit UF and protein value PDI) and the fill unit (UE) of forages from the measurement of some characteristics of each feed. To calculate the nutritive value, a sequential approach is used, based on estimates of organic matter digestibility (dMO) and rumen degradability of feed protein (DT). UF and PDI values are then calculated using stepwise equations of the INRA (1988) systems. Estimates of the dMO are preferentially achieved from the enzymatic degradability method using pepsin-cellulase (dCs or dCo), or determined using the chemical composition of feed or the age of the plant. Estimates of the DT and the PDI values of concentrate feeds are achieved from the enzymatic degradability method using a protease (DE1). Fill values of forages are calculated from the estimates of their voluntary intakes based on their chemical composition or dMO. Equations for different types of forages are calculated from the INRA (1988) feed tables. PrevAlim integrates, co-ordinates and updates different tools already available (prediction of nutritive value) and a new one that estimates fill values of forages. The computer program ensures that the calculated values (UF, PDI and UE) are coherent with themselves and with the feed tables. The hierarchical approach we used allows 1- to estimate feed value even in case of some missing information 2- to choose the most relevant estimates in case of redundant information.Cet article présente les principes retenus pour élaborer le module de prévision de la valeur d’un aliment à partir des résultats de son analyse. Le module PrévAlim, proposé avec la nouvelle version d’INRAtion, permet de calculer à la fois la valeur nutritive (UF, PDI) et pour les fourrages la valeur d’encombrement (UE) à partir de la nature de l’aliment et de la mesure de certaines de ces caractéristiques. Pour la valeur nutritive, une démarche séquentielle a été adoptée, centrée sur l’estimation de la dMO et de la dégradabilité de l’azote (DT) ; le calcul des valeurs UF et PDI utilise ensuite la séquence des équations des systèmes INRA 1988. L’estimation de la dMO se fait soit préférentiellement à partir de la méthode de digestibilité enzymatique pepsine-cellulase (dCs ou dCo), soit à partir de la composition chimique ou de l’âge de la plante. L’estimation de la DT et de la valeur PDI des concentrés est basée sur la méthode enzymatique avec une protéase (DE1). La valeur d’encombrement des fourrages est calculée à partir de l’ingestibilité estimée directement à partir de la composition chimique ou de la dMO ; les équations par grandes classes d’aliments ont été déterminées sur la base des Tables INRA 1988. Ce module rassemble, coordonne et met à jour des outils déjà disponibles (Tables de prévision de 1981 et équations publiées depuis) et des outils créés spécialement (estimation des UE). Les valeurs calculées (UF, PDI et UE) sont cohérentes entre elles ainsi qu’avec celles des Tables. L’approche hiérarchisée adoptée permet de calculer les valeurs même avec des informations manquantes et de retenir la méthode d’évaluation la plus pertinente en cas d’informations redondantes

The effect of condensed tannins in wrapped silage bales of sainfoin (Onobrychis viciifolia) on in vivo and in situ digestion in sheep.

International audienceThe objective of this study was to characterize the condensed tannins (CTs) in wrapped silage bales of sainfoin (Onobrychis viciifolia) and examine their potential action on in vivo and in situ digestive characteristics in sheep. Silage was made from sainfoin, cut at two phenological stages. The first phenological stage, at which silage was made, was from the first vegetation cycle at the end of flowering and the second stage silage was made from regrowth, 5 weeks after the first cut, but before flowering. The silages made from the two phenological stages were fed to 12 rumen-fistulated sheep in a crossover design. Of the 12 sheep, six received polyethylene glycol (PEG) to bind with and remove the effects of CT, whereas the other six were dosed with water. Organic matter digestibility, total-tract N digestibility and N (N) balance were measured over 6 days. Kinetic studies were performed on total N, ammonia N (NH3-N) and volatile fatty acids (VFAs) in rumen fluid before and 1.5, 3 and 6 h after feeding. The kinetics of degradation of dry matter and N from Dacron bags suspended in the rumen were also determined. Biological activity of CT (protein-binding capacity) and CT concentration were greater for the silage made from sainfoin at the early flowering stage. Total-tract N digestibility was increased by the addition of PEG (P < 0.001) to the sainfoin silage before flowering (P < 0.001). CTs decreased N excretion in urine (P < 0.05) and increased faecal N excretion (P < 0.001), but had no effect on body N retention, which is beneficial for the animal. Ruminal N degradability was smaller in the presence of active CT (P < 0.001) at both phenological stages; however, soluble N (P = 0.2060) and NH3-N (P = 0.5225) concentrations in rumen fluid remained unchanged. The results of this experiment indicate that CT in the sainfoin retain their ability to affect the nutritive value of preserved forage legumes

Prévision de la valeur énergétique des aliments composés pour les ruminants

National audienceUntil now net energy (NE) value of compound feeds for ruminants had been calculated from a data bank of single concentrate feed. This study concerned 83 compound feeds, as representative as possible of the variety generally in use : for example, their cereal content varied from 0 to 90 %. In vivo organic matter (OM) or energy digestibility was measured in France by INRA (Theix and INA-PG, Paris,) in UK by the Rowett Research Institute, and in the Netherlands by IVVO, Lelystad. In addition, urinary energy losses and methane losses were measured by Theix and the Rowett Institute. Contents were determined for example, for the cell wall, lignocellulose, lignin (methods of Van Soest and Christian), as well as enzymatic degradabilities. Net energy value of compound feeds was calculated by a step-wise analytical procedure. At each step, the maximum amount of in vivo data was used, after their reliability had been checked. The validity of the estimation criteria necessary at each step was discussed with respect to both to their precision and reliability. This approach led to the formulation of equations predicting the content in NE expressed in feed units (UFL and UFV) with residual standard deviations respectively varying from 0.05 to 0.06 UFL/kg OM and from 0.06 to 0.08 UFV/kg OM according to the analytical criteria considered The association « direct lignin, crude protein, ether extract », which, at first sight seems to be the easiest one to obtain reliably, gave a residual standard deviation of 0.056 UFL and of 0.068 UFV/kg OM. In conclusion, the interest of this study lies in the fact that numerous in vivo measurements were performed, that the compound feeds were representative of those generally in use, and that a large number of laboratory methods were used.La prévision de la valeur énergétique des aliments composés destinés aux ruminants était basée, jusqu’à présent, sur des données moyennes concernant des matières premières. Cette étude porte sur 83 aliments composés, les plus représentatifs possibles de l’éventail des types utilisés en pratique, et dont, par exemple, la teneur en céréales a varié de 0 à 90 %. Les mesures in vivo de digestibilités de la matière organique ou de l’énergie ont été effectuées par l’une des quatre équipes de recherche travaillant à Theix (INRA, France), à l’INA-PG (INRA, France), au Rowett Research Institute (Royaume-Uni) ou à Lelystad (IVVO, Pays-Bas). De plus, les pertes en énergie urinaire et sous forme de méthane ont été mesurées à Theix et au Rowett. Différents constituants ont été dosés suivant des méthodes utilisables par des laboratoires de routine : paroi cellulaire, lignocellulose, lignine (méthodes de Van Soest et de Christian), dégradabilités enzymatiques. Le calcul et la prévision de l’énergie nette procèdent d’une démarche par étapes successives. A chacune d’entre elles, le maximum de données mesurées in vivo, et dont la fiabilité a été préalablement testée, a été intégré. La validité des critères d’estimation nécessaires à chaque étape a été discutée tant au niveau de leur prévision que de leur fiabilité. Cette approche a conduit à proposer des équations de prévision des UFL et des UFV avec des écarts-types résiduels (E.T.R.) variant respectivement de 0,05 à 0,06 UFL/kg MO et de 0,06 à 0,08 UFV/kg MO suivant les critères analytiques considérés. Les trois dosages (lignine « directe », matières azotées totales, extrait éthéré) qui s’appuient sur des méthodes déjà appliquées en routine, conduisent à un E.T.R. de 0,056 UFL et de 0,0068 UFV/kg MO. L’intérêt de cette étude réside dans le nombre important de mesures effectuées in vivo, dans la représentativité des aliments étudiés, ainsi que dans la variété des méthodes de laboratoire impliquées

Une démarche intégrée pour prévoir la valeur des aliments pour les ruminants : PrévAlim pour INRAtion

National audienceThis paper presents the bases of an integrated tool developed to estimate the feed value of forages and concentrates from their laboratory analysis. The computer program PrevAlim, available with the new version of INRAtion software, calculates the nutritive value of feed (feed unit UF and protein value PDI) and the fill unit (UE) of forages from the measurement of some characteristics of each feed. To calculate the nutritive value, a sequential approach is used, based on estimates of organic matter digestibility (dMO) and rumen degradability of feed protein (DT). UF and PDI values are then calculated using stepwise equations of the INRA (1988) systems. Estimates of the dMO are preferentially achieved from the enzymatic degradability method using pepsin-cellulase (dCs or dCo), or determined using the chemical composition of feed or the age of the plant. Estimates of the DT and the PDI values of concentrate feeds are achieved from the enzymatic degradability method using a protease (DE1). Fill values of forages are calculated from the estimates of their voluntary intakes based on their chemical composition or dMO. Equations for different types of forages are calculated from the INRA (1988) feed tables. PrevAlim integrates, co-ordinates and updates different tools already available (prediction of nutritive value) and a new one that estimates fill values of forages. The computer program ensures that the calculated values (UF, PDI and UE) are coherent with themselves and with the feed tables. The hierarchical approach we used allows 1- to estimate feed value even in case of some missing information 2- to choose the most relevant estimates in case of redundant information.Cet article présente les principes retenus pour élaborer le module de prévision de la valeur d’un aliment à partir des résultats de son analyse. Le module PrévAlim, proposé avec la nouvelle version d’INRAtion, permet de calculer à la fois la valeur nutritive (UF, PDI) et pour les fourrages la valeur d’encombrement (UE) à partir de la nature de l’aliment et de la mesure de certaines de ces caractéristiques. Pour la valeur nutritive, une démarche séquentielle a été adoptée, centrée sur l’estimation de la dMO et de la dégradabilité de l’azote (DT) ; le calcul des valeurs UF et PDI utilise ensuite la séquence des équations des systèmes INRA 1988. L’estimation de la dMO se fait soit préférentiellement à partir de la méthode de digestibilité enzymatique pepsine-cellulase (dCs ou dCo), soit à partir de la composition chimique ou de l’âge de la plante. L’estimation de la DT et de la valeur PDI des concentrés est basée sur la méthode enzymatique avec une protéase (DE1). La valeur d’encombrement des fourrages est calculée à partir de l’ingestibilité estimée directement à partir de la composition chimique ou de la dMO ; les équations par grandes classes d’aliments ont été déterminées sur la base des Tables INRA 1988. Ce module rassemble, coordonne et met à jour des outils déjà disponibles (Tables de prévision de 1981 et équations publiées depuis) et des outils créés spécialement (estimation des UE). Les valeurs calculées (UF, PDI et UE) sont cohérentes entre elles ainsi qu’avec celles des Tables. L’approche hiérarchisée adoptée permet de calculer les valeurs même avec des informations manquantes et de retenir la méthode d’évaluation la plus pertinente en cas d’informations redondantes