B. Carré

Digestion of plant cell walls from four different sources in growing pigs

Abstract Large White pigs of about 40 kg were grown on six diets (4 pigs per diet) that contained 40% wheat and soya bean protein as protein source. In the control diet (W) the only added carbohydrate source was starch; in the five other diets this was partly replaced by 22% wheat bran (WB), 44% wheat bran (2WB), 16% sugar beet pulp (SBP), 19% soya bean hulls (SBH) or 22% wheat straw (WS). The animals were given similar amounts of digestible energy. The apparent digestibility (AD) of dry matter (DM), nitrogen (N), energy (E), neutral detergent fibre (NDF), acid detergent fibre (ADF) and non-starch polysaccharides (NSP) of the diets was determined. Whatever the fibre source added to the diets, the AD of N and E was significantly reduced relative to the control diet. In diets with similar NSP contents (2WB, SBP, SBH, WS diets), the AD of E was higher in SBP and SBH diets (0.841 and 0.834 for E, respectively) and lower in the WS diet (0.736). No significant change in AD of N (0.810 on average) was observed. The AD of NDF varied with that of total NSP (WS

European reference method for the in vivo determination of metabolisable energy with adult cockerels: Reproducibility, effect of food intake and comparison with individual laboratory methods

1. A common reference procedure adopted by several European laboratories to determine apparent metabolisable energy corrected to zero-nitrogen balance (AMEn) is described. 2. Reproducibility has been estimated by comparing results from 4 diets measured in 7 laboratories. The standard deviations between laboratories of dry matter, gross energy, Kjeldahl nitrogen and AMEn were respectively, on average, 11.29 g/kg, 0.242 MJ/kg, 1.56 g/kg and 0.380 MJ/kg dry matter; the corresponding coefficients of variation between laboratories were 1.27, 1.29, 4.39 and 2.92%. 3. Effect of food intake was tested by comparing AMEn from birds fed either 0.90 or 0.45 of ad libitum: the amount of food intake had a negligible effect on AMEn values. Endogenous energy losses corrected (EELn) or not (EEL) to zero nitrogen balance were estimated either by regression between excreted energy and ingested energy or in fasted and glucose-fed cockerels. EELn estimated by regression was, on average, 8.7 kJ/bird/d.; it was independent of diet composition. EEL and EELn determined in fasted or glucose-fed birds were higher than those determined by regression. 4. AMEn values measured by individual laboratory procedures were very close to those obtained by the reference method, except from laboratories using a tube feeding procedure, where deviations were probably a consequence of overestimated EEL.

Contribution of oligosaccharide and polysaccharide digestion, and excreta losses of lactic acid and short chain fatty acids, to dietary metabolisable energy values in broiler chickens and adult cockerels

1. Two experiments were conducted, using both adult cockerels from a layer strain and 3-week-old broiler chickens. In the first experiment, one of the 2 diets investigated was composed mainly of maize and soyabean meals, the other one containing the latter ingredients diluted with 475 g/kg mature pea seeds. For these 2 diets, the apparent metabolisable energy values corrected to 0 nitrogen retention (AMEn) were derived, together with the apparent digestibilities of nitrogen, amino acids, total lipids, starch, individual oligosaccharides, and non-starch polysaccharides (NSP). Excretions of lactic acid and short chain fatty acids (SCFA) were also determined. 2. In the first experiment, the mean apparent digestibilities of starch, lipids, total amino acids, NSP, sucrose and alpha-galacto-oligosaccharides in adult cockerels were 0.946, 0.785, 0.835, 0.045, 0.99 and 0.99, respectively. In broiler chickens, they were 0.938, 0.675, 0.830, -0.016, 0.988 and 0.867, respectively. The bird type effects were significant (P < 0.05) for the digestibilities of starch, lipids, NSP (for the maize-soyabean meal diet, only) and alpha-galacto-oligosaccharides. Broiler chickens excreted a mean of 11.032 g organic acids/kg diet against 4.190 in adult cockerels (P < 0.001). These digestibility measurements enabled the contribution made by each dietary component to the AMEn value of the diets to be calculated. AMEn values were lower in broiler chickens than in adult cockerels, with on average 0.8 MJ/kg dry matter difference resulting from bird type. This difference was accounted for by differences between bird types in energy supplied by lipids (34.0%), starch (7.5%), alpha-galacto-oligosaccharides (8.7%), NSP (14.2%), and in energy losses from lactic acid excretion (16.4% of the difference in AMEn between bird types). 3. In the second experiment 2 diets were studied, consisting of a basal and the basal diluted with 30 g/kg lactose (a fermentable sugar in chickens) and 12 g/kg of a water-soluble gel-forming component containing 50% polygalacturonic acids. Lactose digestibilities reached 0.928 and 0.712 in adult cockerels and chickens, respectively. The digestibilities of the water-soluble polygalacturonic acids were similar in cockerels and broiler chickens, with a mean value of 0.672. Figures similar to those of the first experiment were found in the comparison between cockerels and broiler chickens, for the AMEn values of diets, the digestibilities of starch and lipids and the excretion of lactic acid. Broiler chickens excreted 4.580 g lactic acid/kg dry food intake, compared with 0.740 g in the adult.(ABSTRACT TRUNCATED AT 400 WORDS)

Relationships between digestibilities of food components and characteristics of wheats ( Triticum aestivum ) introduced as the only cereal source in a broiler chicken diet

1. The aim of the experiment was to establish relationships between chemical or physical characteristics of wheats ( Triticum aestivum ) and digestibilities of food components in broiler chickens fed on wheat-based diets. Twenty-two wheat samples, each differing by their cultivar origin, were included at 550 g/kg in diets offered to male Ross broiler chicks. The other main ingredients were soya bean meal (340 g/kg) and rapeseed oil (68.5 g/kg). Diets were given as pellets. 2. In vitro viscosities of wheats measured as potential applied viscosity (PAV) or real applied viscosity (RAV) varied between 1.91 and 6.03, or between 0.95 and 3.81 ml/g (dry matter basis), respectively. Hardness of wheats varied between 17 (soft) and 95 (very hard), and lipase activity of wheats varied from 1 to 13.6 (relative scale). 3. PAV and RAV values were not significantly correlated with hardness. PAV and RAV values were correlated with (80:20) ethanol:water insoluble.961, 0.932, respectively), with the amount of water retained by cell walls ( r .656, 0.492, respectively), and with lipase activity ( r = 0.600, 0.532, respectively. 4. Hardness was correlated with ash ( r = -0.484), nitrogen ( r = 0.534), mean particle size of wheat flours ( r = 0.631), and specific energy of pelleting ( r = -0.574). 5. Wheat diets were evaluated in two assays with 3-week-old chicks, with 11 diets per assay. In each assay, a balance experiment was carried out using the total collection method. Growth performance was also measured during the balance experiment. 6. In vitro viscosity parameters were negatively correlated with diet AME n .05), lipid digestibility ( P < 0.05) and, to a lesser extent, protein digestibility ( P < 0.05). In vitro viscosity data were positively correlated with food:gain ratio ( P < 0.05) and water loss parameters ( P < 0.05), and were not significantly ( P > 0.05) correlated with starch digestibility. 7. Wheat hardness-related parameters were correlated ( P < 0.01) wi.273, -0.305, 0.212, respectively). 8. Wheat lipase activity was negatively c.179; P < 0.05) and starch ( r = -0.225; P < 0.01) digestibilities and with individual diet AME n ( r = -0.266; P < 0.001). Individual diet AME n .175) with the values calculated by the EU AME n prediction equation (Fisher and McNab, 1987). Among the correlations observed between the individual measured AME n :EU predicted AMEn ratio and wheat parameters ( P .05), the correlation obtained with wheat lipase was the highest ( r = -0.195). The correlations with lipase could be explained in part by strong correlations between lipase and in vitro viscosity parameters.

Composition of cell walls from cotyledons of Pisum sativum, Vicia faba and Glycine max

Abstract Cell walls from cotyledons of smooth field pea, broad bean and soya bean contain ca 55% pectic polysaccharides associated with 9% cellulose. Arabinose is the major pectic sugar of pea and broad bean walls whereas soya bean pectic polymers are constituted of galactose and arabinose in the ratio (2:1). Galacturonic acid represents ca 20% of the walls. In addition, pea and broad bean cell walls contain, respectively, 12% and 6% of non-starchy and non-cellulosic glucans bearing 4,6-linked and 3-linked glycosyl units. EDTA-soluble acidic pectic substances are distinct rhamnogalacturonans bearing decreasing proportions of interrupting rhamnose from highly interrupted moieties to nearly homogenous homogalacturonans. Pea and broad bean rhamnogalacturonans are associated with arabinose-containing polymers of average DP ca 30–35 whereas soya bean ones have side chains of arabinose and galactose of DP ca 40.

European reference method of in vivo determination of metabolisable energy in poultry: Reproducibility, effect of age, comparison with predicted values

1. Apparent metabolisable energy corrected to zero-nitrogen retention (AMEn) was measured using the European reference procedure in 9 European laboratories. Seven pelleted diets were evaluated. AMEn was measured with adult cockerels and young birds. 2. Between-laboratory standard deviations were for dry matter (DM) 12.5 g/kg, gross energy 0.085 MJ/kg DM, Kjeldahl nitrogen 0.768 g/kg DM, AMEn (adults) 0.256 MJ/kg DM, and AMEn (young) 0.337 MJ/kg DM. Corresponding coefficients of variation between laboratories were 1.42, 0.45, 2.15, 1.88 and 2.60% respectively. 3. AMEn values of experimental diets were always significantly lower when measured with young birds. This effect was more pronounced when diets contained added fat. 4. Tallow or soyabean oil were incorporated into two basal diets at 40 g/kg inclusion rate. No significant differences were observed between AMEn values of either diet with adults or young birds, suggesting that AMEn energy values of these fats are indistinguishable at this inclusion rate. 5. Similar AMEn values were obtained in young birds by estimating nitrogen accretion, either by the difference between intake and excreta nitrogen or by measuring body weight gain. Determined AMEn values were very similar to those predicted using three different regression equations.

Effects of food deprivation and particle size of ground wheat on digestibility of food components in broilers fed on a pelleted diet

1. The first aim of the experiment was to study the effect of wheat (Triticum aestivum) particle size on the digestibility of starch in a pelleted diet given to broilers. The second aim was to study the consequences of food deprivation before the excreta collection period (from 21 to 24 d). Wheat from a strong hardness cultivar was incorporated at 546·1 g/kg in diets. The other main ingredients were soybean meal (353·5 g/kg) and rapeseed oil (55·0 g/kg). Diets were given as pellets. The experimental design was a 2 × 2 factorial design testing two particle sizes of wheat flour and two procedures of a balance experiment (with or without food deprivation). 2. Birds given diet C (wheat coarse grinding before pelleting) had significantly greater gizzard weight than birds fed on diet F (wheat fine grinding before pelleting). 3. Starch digestibility value was significantly increased when birds were fed on diet F. This effect was halved by food deprivation. No significant effect of grain particle size was observed for protein and lipid digestibility values. However, food deprivation decreased apparent protein digestibility, with an effect which was more pronounced for fine than for coarse grinding. 4. AMEN of the diet was significantly improved by fine grinding of wheat and decreased by food deprivation. However, no significant differences in growth performance were induced by differences in wheat grinding. 5. No significant effect of grinding was observed on the water excretion:feed intake ratio. No significant difference was observed for vent score between treatments. 6. There was over-excretion of starch in the first hours of refeeding following food deprivation.

Causes for variation in digestibility of starch among feedstuffs

Reasons for starch digestibility variations are reviewed by considering starch granule structure, antinutritional factors and access problems in coarse particles. Feed technology treatments that can overcome low starch digestibilities are also reviewed. Before considering these factors, the particular features of the digestive system of chickens are briefly reviewed. The digestive system of chickens for starch hydrolysis is characterised by a high enzymatic potential. However, in contrast with mammals, the potential of chickens for completing starch digestion by microbial degradation in the distal part of the digestive tract is very low. Variations in starch granule structure especially concern legume seeds compared to cereals, with greater resistance observed for the former. Plant mutants may result in variations in amylose contents of starch granules. Those with high amylose content (70%) produce low starch digestibilities. Cereals with no amylose (waxy starch) do not show strong evidence of benefit despite lower resistance of starch granules. In practical conditions, antinutritional factors such as proteinaceous α-amylase inhibitors, condensed tannins and viscous water-soluble non-starch polysaccharides generally result in low effects on starch digestibility. However, viscosity may induce a noticeable effect with high viscosity barleys. There is much less evidence that viscosity can explain the low starch digestibilities (< 94%) which are observed with some wheat samples. Positive effects of enzyme additives on starch digestibility of cereals probably result from effects both on viscosity and on disruption of coarse particles. Access problems in coarse particles are responsible for low starch digestibilities observed with legume seeds. However, mechanical treatments such as fine grinding and pelleting can readily overcome this problem. Access problem in coarse particles is also probably the reason that explains low starch digestibilities in some cereal samples, as shown by negative relationships between hardness and starch digestibility of wheats. However, grinding and pelleting of cereals seem to be less efficient than with legume seeds. Interactions with feeding behaviour and genetic origin of birds have also to be considered for explaining variations in starch digestibility of cereals.

Nutrient digestibility and intestinal viscosities in broiler chickens fed on wheat diets, as compared to maize diets with added guar gum

1. Three maize diets containing 0, 1 or 3 g of guar gum per kg and 2 wheat diets were given to male broiler chickens for measurements of growth performance and nutrient digestibility. 2. The intestinal viscosities found with wheat diets were within the range of those observed with the 3 maize diets. The correlations between in vivo and in vitro viscosities were higher with real than with potential applied viscosity. 3. The gain:food ratio decreased (P<0.05) with the addition of 3 g guar gum/kg. The mean gain:food ratio observed for wheat diets was lower (P=0.007) than the mean value found for the 3 maize diets. 4. The negative effects of increased intestinal viscosity due to guar gum addition on nutrient digestibility were highest for lipids and lowest for starch. 5. Wheat diets resulted in much lower (P<0.001) starch apparent digestibility compared to maize diets with added guar gum despite similar mean intestinal viscosities in the 2 groups of diets. Apparent lipid digestibility with wheat diets was lower (P<0.01) than the value predicted from intestinal viscosity, the predictive model having been calculated with the guar gum added maize diets. Apparent protein digestibility did not differ between wheat diets and guar gum added maize diets. 6. It was concluded that the low apparent digestibilities of starch and lipid observed with wheats could not be attributed only to intestinal viscosity and that other factors appear to be implicated in the low digestibilities observed with the wheat samples tested in the present experiment.

Effects of diet particle size on digestive parameters in D+ and D− genetic chicken lines selected for divergent digestion efficiency

The aim of this experiment was to compare the D(+) and D(-) chicken lines genetically selected for divergent digestion efficiency by testing the effects of diet particle size on growth performances, digestion efficiencies, and digestive organ weights in both lines. A 2 x 3 factorial arrangement of treatments was used to test the D(+) and D(-) lines (sixth generation) and 3 diets, namely a pelleted standard corn diet (S), a pelleted hull diet (H) made by diluting S diet with 7% coarse cereal hulls, and a coarse corn diet (C) identical to the S diet, distributed as 30% coarsely crushed corn mixed with the 70% pelleted remaining part. Experimental diets were fed from 7 to 26 d of age. Combining results from all diets obtained at 26 d of age, D(+) birds showed 9% heavier (P < 0.0001) gizzard and 10% lighter (P < 0.0001) small intestine than D(-) birds. The AME(n) and digestibilities of lipids, protein, and starch measured at 3 wk of age were, on average, 3.5, 5.6, 5.8, and 0.5% higher (P < 0.0002) in D(+) than in D(-) birds, respectively. Significant (P </= 0.05) interactions between lines and diets were observed for AME(n) and digestibility values. Measured:calculated AME(n) ratio and digestibilities of protein and starch were improved (P < 0.05) by dietary coarse particles in D(-) birds, not in D(+) birds. Measured:calculated AME(n) ratio differed between lines by 6.0% with S diet versus 2.3% with H and C diets. In D(-) birds, the digestion increases due to coarse particles were associated with increased weights of gizzard (P < 0.0001) and pancreas (P < 0.05). In D(+) birds, coarse particles resulted in increased weights of gizzard (P < 0.0001) only. In conclusion, growth and functions of gizzard and pancreas needed to be stimulated by dietary coarse particles for optimum digestion efficiencies in D(-) chickens, whereas such stimulations were not needed in D(+) chickens. The D(+) chickens showed high digestion efficiencies in all cases, independently of diet particle size.