Methodological impact of starch determination on starch content and ileal digestibility of starch in grain legumes for growing pigs

Background: Grain legumes represent a valuable energy source in pig diets due to their high starch content. The present study was conducted to determine the content and apparent ileal digestibility(AID) of starch in different grain legume cultivars for pigs by means of both a polarimetric and enzymatic method for starch determination.Methods: Three experiments were conducted with six barrows each which were fitted with ileal T-cannulas. In total, 18 diets including six different cultivars of faba beans(Vicia faba L.) and peas(Pisum sativum L.), five different cultivars of lupins(Lupinus luteus L., Lupinus angustifolius L.), and one diet with a soybean meal(SBM) were fed.Results: The starch content of faba beans and peas was greater(P 0.05) when determined polarimetrically than enzymatically(438 vs. 345 g/kg dry matter(DM) in faba beans and 509 vs. 390 g/kg DM in peas, respectively).Considerable lower starch contents were obtained in lupins and SBM, with 82 and 48 g/kg DM(analyzed polarimetrically) and 1.1 and 3 g/kg DM(analyzed enzymatically), respectively. Mean values for contents of neutral detergent fiber(NDF) and acid detergent fiber(ADF) in grain legumes ranged from 111 and 79 g/kg DM in peas to248 and 207 g/kg DM in lupins, respectively. Contents of condensed tannins in the colored flowered faba bean cultivars ranged from 2.1 to 7.4 g/kg DM. The AID of starch was greater(P 0.05) in pea than in faba bean cultivars,and using the polarimetric starch determination method resulted in greater(P 0.05) digestibility values than using enzymatic starch analysis(84 vs. 80% in faba beans and 86 vs. 83% in peas). Moreover, AID of starch differed(P 0.05)within pea cultivars and starch digestibility in faba beans decreased linearly(P 0.05) as the content of condensed tannins increased. However, there was no relationship between contents of NDF and ADF and AID of starch in pea and faba bean cultivars.Conclusion: Both contents and AID of starch in grain legumes can vary as influenced by the analytical method used for starch determination. Generally, starch digestibility is greater when measured by polarimetric rather than enzymatic methods.     

Self-regulation of intake of polyethylene glycol by sheep fed diets varying in tannin concentrations

Tannins occur in many plant species, and they often suppress intake by reducing nutrient availability or by causing malaise. Polyethylene glycol (PEG) binds to tannins and may thereby increase the availability of macronutrients and decrease malaise. Supplemental PEG increases intake of tannin-containing plants by sheep, goats, and cattle. Given the strong response to supplemental PEG, we speculated that animals might self-regulate their intake of PEG when offered foods high in tannins. The objective of the first experiment was to determine if the amount of supplemental PEG (0, 25, 50, 75, or 100 g; molecular weight, 3,350) affected intake by lambs of a food (milo-tannin mix) containing 20% quebracho tannin. There was a linear relationship (Y = 272 + 1.2X; R2 = .86; P = .023) between the amount of supplemental PEG ingested and the subsequent intake of milo-tannin food by lambs. The objective of the second experiment was to determine whether lambs self-regulated intake of PEG when fed a ration that contained 0, 5, 10, 15, or 20% quebracho tannin and whether they adjusted their intake of PEG when tannin was removed from the diet. There was a positive relationship between the amount of PEG ingested and intake of food and tannin (P = .0001). Lambs fed high-tannin diets ate more PEG than controls (P = .03). Lambs fed the 20% tannin diet ate the most PEG, and controls ate the least PEG. Tannin limited intake of the diets, but PEG attenuated the response to a great degree (P = .065). Immediately after tannin was removed from the ration, lambs that formerly had been fed the 20% tannin ration ate more PEG than lambs fed the other rations (P = .0075). Ten of the lambs (5 from the 20% tannin group, 1 from the 15% tannin, and 2 each from the 10 and 5% groups) continued to eat PEG for 7 d after tannin was removed from their ration. When they were tested again 6 wk after the trial and offered tannin-free diets, their intake of PEG had decreased.     

The possible role of methionine in the detoxification of faba bean (Vicia faba L.) tannins in chick diets

1. A metabolism trial was designed to investigate the role of methionine as a specific detoxifying agent of the condensed tannins present in faba beans (Vicia faba L.).

2. A 5 x 5 factorial approach was employed where 5 concentrations of dietary methionine were obtained (ranging from 3.9 to 12.15 g/kg diet dry matter) by the addition of DL‐methionine, and 5 concentrations of condensed tannins (ranging from 0.5 to 19.7 g/kg diet dry matter) by altering the ratio of tannin‐free and tannin‐containing faba bean hulls added to a basal diet.

3. The intake of condensed tannins had a significant, depressive effect on apparent available nitrogen (P< 0.001) and nitrogen corrected apparent metabolisable energy (AME_n ) (P< 0.001). There was no interaction between methionine and tannin (P>0.05). Thus the depressive effect of tannin was independent of methionine levels in the diet.

4. Methionine does not act as a specific detoxifier of faba bean condensed tannins.     

Effects of toasting,inclusion levels and different enzyme supplementations of faba beans on growth performance of broiler chickens

Faba beans (Vicia faba) are an alternative protein source that likely can be used to a higher extent in broiler diets. White-flowered faba beans contain antinutritional substances (ANS) such as non-starch polysaccharides (NSP), trypsin inhibitors, and lectins, which might limit its inclusion level. Lectins and trypsin inhibitors are heat labile and previous studies have shown that steam-pelleting and enzyme treatment improves the nutritional value of faba beans. However, alternative to pelleting would facilitate for farmers to add faba beans on-farm. Currently, there are machines available for toasting faba beans on-farm, which might be used for broiler mash diets. The objective of this study was to investigate the effect of inclusion level (0, 10, 20 and 30%), toasting (140°C 5.5 min) and different enzymes (xylanase + phytase vs. xylanase, phytase, amylase, protease) of faba bean diets on growth performance and organ parameters in broilers. To test this, 2 experiments 34 and 35 days, using a total of 480 chickens were performed. Feed intake, body weight (BW) and feed conversion ratio were registered weekly, in addition, organ and carcass weights were registered at slaughter. The results showed that inclusion of 20% faba beans is possible in a pelleted diet with maintained broiler growth performance. When 20% was included in a mash diet, feed intake and BW decreased compared to chickens fed pelleted diets, irrespectively of pre-toasting of the beans. It can be concluded that toasting cannot replace pelleting. Supplementation of protease and amylase in addition to xylanase and phytase did not improve the nutritional value of faba beans.     

Optimum inclusion of field peas, faba beans, chick peas and sweet lupins in poultry diets. I. Chemical composition and layer experiments

1.Experiments were undertaken to determine the chemical composition and apparent metabolisable energy (AME) of field peas, faba beans, sweet lupins and chick peas and the production of hens when each was included in nutritionally similar diets at 250 g/kg in 2 experiments. 2. Amino acid composition, crude protein and AME agreed well with previously published measurements. Detailed analysis of the non-starch polysaccharides (NSPs) showed that sweet lupins were much higher than the other grain legumes in the soluble NSPs and that the NSPs were particularly high in arabinose. The condensed tannin content was highest in field peas followed by faba beans. 3. In the 1st layer experiment over 40 weeks, hen-day egg production was lowest on the faba bean-based diet and egg weight and egg mass were also lowest. Relative viscosity of digesta in the small intestine of hens fed on the sweet lupin-based diet was highest, followed by that of hens fed on field peas. Enlargement of the pancreas was observed in hens consuming chick peas. 4. In experiment 2, in which only sweet lupins and faba beans were used, steam or cold pelleting showed few effects, nor did dehulling of faba beans but egg weight was lower when diets were steam pelleted. Daily food intake was 5.7 g/bird lower on the steam than cold pelleted diets and food conversion ratio tended to be improved (P=0.082). 5. It was concluded that field peas could support good production at 250 g/kg of layer diet. Although chick peas and sweet lupins supported good performance, there was concern about the increased weight of the pancreas and high gut viscosity respectively. Faba beans showed similar hen-d egg production in the 2nd experiment to that of sweet lupins but egg weight tended to be about 0.8 g lower than when on the sweet lupin-based diets.     

The effect of protease and Bacillus licheniformis on nutritional value of pea,faba bean,yellow lupin and narrow-leaved lupin in broiler chicken diets

ABSTRACT

1. This study investigated the nutritional value (digestibility of ileal crude protein and amino acids (AAs)) and the AME_N value of legumes (pea, faba bean, yellow lupin, and narrow-leaved lupin) with or without protease.

2. Two hundred, one-day-old, male Ross 308 broiler chickens were randomly allocated to ten groups. Each group received one of five different protein raw materials – either peas, faba beans, yellow lupins or narrow-leaved lupins, with or without protease produced from Bacillus licheniformis. The birds were kept in individual cages. Nutrient digestibility was calculated using the difference method. The total duration of the study was 23 d, and the study involved two phases – accommodation phase (d 1–18) and experimental phase (d 18–23).

3. The effect of protease on response traits was not consistent between the legumes. The enzyme increased the digestibility of some AAs in the pea (arginine, leucine, phenylalanine, histidine, tyrosine, alanine, and proline), faba bean (lysine, arginine, glycine, and asparagine), and yellow lupin diets (lysine, valine, and serine), but this effect was not observed in the narrow-leaved lupin diet. The change in AME_N values due to protease addition was only statistically significant for the pea diet (P < 0.05), whereas in the case of other legume species, the difference was insignificant (P > 0.05).

4. Exogenous protease increased the digestibility of AAs present in pea, faba bean, and yellow lupin seeds but not in narrow-leaved lupin diets. The AME_N value of peas increased with protease supplementation, but no effect of protease was found for the AME_N values of faba bean and both the lupin diets.     

Effect of tannins on starch digestibility and tmen of triticale and semipurified starches from triticale and field beans

1. The effects of field bean tannin‐containing hulls (T‐hulls), non‐tannin hulls (NT‐hulls) and tannin extract on starch digestibilities and TMEn of triticale and semipurified starches from triticale and field beans were evaluated with adult cockerels and 3‐week‐old‐chicks.

2. For both cockerels and chicks, the digestibility and TMEn of semipurified starches from triticale were higher than those from beans. Starch digestibilities of triticales (range 99.1 to 97.7%), of semipurified starches from triticales (range 96.5 to 89.9%) and from field beans (range 75.4 to 71.6%) were similar for both cockerels and chicks.

3. The addition of NT‐hulls improved, in general, the digestibility of semipurified starches for both chicks and cockerels, which suggests that fibre improves the digestion of semipurified starches.

4. The effects of tannins of T‐hulls on semipurified starch from beans and from triticale were different. Tannins always decreased the digestibility and TMEn of semipurified starch from field beans but only decreased the digestibility and TMEn of semipurified starch from triticale when fed to chicks, but not when fed to cockerels.

5. The addition of tannin extract always decreased the digestibility of semipurified starches by a greater amount than T‐hulls, which supports the idea that the effect of tannins depends on the quantity of tannin ingested.     

The enhancement of the nutritive value of mango seed kernels for poultry by thermal treatment and radiation processing.

Raw seed kernels of local mango varieties (Magnifera indica L.) were analyzed for composition, levels of trypsin inhibitors, tannins, cyanogenetic glucosides, in vitro protein digestibility and apparent metabolizable energy (AMEN) as being effected by boiling, autoclaving as well as irradiation at 5, 10, 15, and 20 kGy. The air-dry mango seed kernels (MSK) contained CP 70 g kg-1, EE 128 g kg-1, and tannins 67 g kg-1. Compared with raw kernels the contents of trypsin inhibitory activity (30 TIU g-1) and cyanogenetic glucosides, measured as hydrocyanic acid (71 mg kg-1), were lowered by boiling, autoclaving and radiation treatments. Tannin content (67.2 g kg-1 in raw kernels) was decreased only by boiling or autoclaving, but irradiation did not introduce any effect. The low in vitro protein digestibility and AMEN values of raw MSK were enhanced by processing. The improvements were paralleled to reductions in trypsin inhibitory activity, cyanogenetic glucosides and tannin contents. Greater improvements were noticed with boiling and autoclaving than with irradiation alone. Autoclaving for 30 min plus irradiation treatment up to 20 kGy increased the in vitro protein digestibility and AMEN by 139% and 72%, respectively. These results indicate that tannins, trypsin inhibitors and cyanogenetic glucosides are responsible for the poor nutritive value of MSK. The effects of feeding 200 g kg-1 raw or processed MSK on the performance of broiler chicks were examined. The inclusion of raw kernel affected body weight gain and feed consumption, while weight gain of birds fed the autoclaved (30 min) plus irradiated (20 kGy) kernels was significantly more improved than by the other treatments. However, feed conversion ratio was not significantly different between groups fed the processed MSK. The results showed that the combination of autoclaving for 30 min plus irradiation up to 20 kGy upgraded the nutritive value more than the other tested treatments and that this method is most effective in processing MSK to be used as animal feed.     

Effect of inclusion level of linseed on the nutrient utilisation of diets for growing broiler chickens

1. Diets containing linseed at inclusions of 0, 80, 120 and 160 g/kg were evaluated for digestibility of nutrients and AMEn content with male broiler chickens. 2. Increasing the concentration of linseed decreased the retention of nitrogen and the digestibility of amino acids, crude fat and fatty acids of diets. 3. Dietary AMEn (MJ/kg) was also affected by the rate of inclusion of linseed, values decreasing from 14.39 to 12.49. 4. In general, a linear regression model explained the relationship between dietary linseed content and nutritive parameters. However, the quadratic response found for the digestibility of several amino acids and fatty acids indicated a non-additive change in their digestibility. 5. Viscosity ofjejunal digesta was markedly increased by each increment of linseed in the diets. This is attributable to the presence of mucilage in linseed and it might explain many of the results obtained in this study.     

Attempts to eliminate from field beans the anti‐nutritive factor which reduces egg production

1. In a series of experiments with laying hens, attempts were made to eliminate the anti‐nutritive factor which reduces egg production when feeding field beans (Vicia faba L.) as a source of supplementary protein in cereal‐based diets.

2. Neither pelleting diets nor heat processing the beans by autoclaving proved beneficial. A continuous‐flow process for infra‐red heating of the seeds at 150 °C for 70 s followed immediately by flaking (micronisation) gave inconsistent results.

3. Beans having a white skin with associated low tannin content, did not support significantly higher egg production than did a normal brown‐skinned bean, thus indicating that tannin was not the main anti‐nutritive factor.

4. A cotyledon fraction, obtained by mechanical removal of the tannin‐containing skin from brown beans, did not support higher egg production than did the whole bean, and the corresponding brown‐skin fraction did not reduce egg production when substituted for cereal in the control diet. Again this indicated that tannin was not implicated.     

Polyethylene glycol as a means for reducing the impact of condensed tannins in carob pulp: effects on lamb growth performance and meat quality

We conducted an experiment to evaluate the effects that a diet containing condensed tannins with and without polyethylene glycol (PEG) has on lamb growth and meat quality. Twenty-three male Comisana lambs were introduced to the three experimental diets between 45 and 50 d of age. Eight were given a diet containing 56% of Ceratonia siliqua (carob) pulp (tannin group), another eight received the same diet with a supplement of 40 g of PEG for each kilogram of diet (PEG group), and the remaining seven lambs were given a conventional maize-based diet (maize group). Voluntary feed intake and live weights were measured until slaughter at 105 d of age, and digestibility measurements were undertaken toward the end of the feeding trial. Carcass yield, meat quality characteristics, and a taste panel evaluation were conducted. The tannin-based diet contained 2.5% condensed tannins (DM basis), and lambs given this diet had lower growth rates and poorer feed efficiencies (P < .01) compared with the other treatment groups. Daily gain was similar between the maize and PEG lambs, although the efficiency of feed conversion was highest in the maize group. The digestibility of DM, N, and fiber was reduced (P < .05) by the condensed tannins. Lambs fed the tannin diet had a lower carcass yield (P < .05) and had less fat (P < .05), and the meat had a higher ultimate pH (P < .01) than those given the PEG or maize diets. Condensed tannins affected meat color, which was lighter (L*) than meat from lambs given the PEG-containing diet (P < .01). Sensory evaluation showed that panelists preferred meat from lambs receiving PEG and maize treatments compared with those receiving the tannin diet, and this could be related to differences in meat ultimate pH and carcass fatness. These results show that condensed tannins from carob pulp are very detrimental to feed digestibility and lamb performance. Inclusion of 40 g of PEG/kg diet eliminated the effects of condensed tannins so that lamb performance and meat quality were similar to lambs given a maize-based diet.     

The effect of autoclaving and methionine supplementation on the growth of chicks given diets containing field beans (Vicia Faba L.)

Three experiments are described. The first two show that a beneficial effect on live‐weight gain and food conversion efficiency may be obtained when beans are autoclaved before feeding to chicks at levels up to 75% of the diet. However, much of the response obtained may have been due to an increase in amino acid availability after autoclaving. When no amino acids were limiting, the response in live‐weight gain to autoclaving was small and it is unlikely to justify commercial adoption. In the third experiment it was found that the gain was similar whether the beans were autoclaved for 15, 30, 60 or 90 min. No response to the removal of tannins by ethanol extraction was obtained.     

饲料中抗营养因子--单宁的含量分析方法

针对近年来单宁在动物营养上的最新研究成果,本文重点阐述了饲料中缩合单宁、可水解单宁和总酚类化合物的分析方法。旨在为更好地利用含单宁饲料提供参考。     

2种指示剂测定玉米干酒糟及其可溶物生长猪标准回肠氨基酸消化率的比较研究

本试验旨在研究三氧化二铬和氧化钛2种指示剂对测定玉米干酒糟及其可溶物(D D G S)生长猪标准回肠氨基酸消化率的影响。试验选用6头安装简单T型瘘管的三元杂交(杜洛克×大白×长白)去势公猪,初始体重为(35.1±2.1)kg,应用6×6拉丁方试验设计,分为6期,6种日粮,分别以三氧化二铬和氧化钛配制4种含D D G S日粮,2种无氮日粮。结果表明:玉米D D G S的赖氨酸和色氨酸标准回肠消化率最低;除组氨酸和苯丙氨酸外,2种指示剂对测定其他必需氨基酸和非必需氨基酸标准回肠消化率均无显著影响(P>0.05)。结果提示,三氧化二铬和氧化钛均可用于测定玉米D D G S氨基酸消化率。     

Optimum inclusion of field peas, faba beans, chick peas and sweet lupins in poultry diets. II. Broiler experiments

1.Three experiments were undertaken to determine the optimum inclusion rates of field peas, faba beans, chick peas and sweet lupins in broiler starter and finisher diets in amounts up to 360 g/kg. 2. In experiment A chickens in cages grown to 21 d on diets with field peas and faba beans gave better growth rate and feed efficiency than those with sweet lupins and chick peas. Growth rate and Food conversion ratio (FCR) improved with increasing amounts of faba beans in the diet while for chick peas growth rate and FCR declined. Digesta viscosity and excreta stickiness scores were much higher on diets with sweet lupins. Steam pelleting improved growth rate and FCR on all diets. 3. In experiment B birds were in cages and grown from 21 to 42 d. There were no differences between grain legumes (when combined for all inclusions) for growth rate, food intake or FCR. Viscosity was again much higher on the sweet lupin-based diets while the pancreas was significantly enlarged on the diets with chick peas, as observed previously in chickens grown to 21 d. Steam pelleting of diets gave a consistent and positive response for weight gain and FCR. 4. Experiment C was carried out in pens each holding 60 birds under semi-commercial conditions and grown to 42 d on starter and finisher diets with the same grain legumes as used previously but each at 2 rates of inclusion similar to those in commercial practice. Field peas at 200 to 300 g/kg and chick peas at 150 to 220 g/kg gave inferior growth to faba beans (150 to 180 g/kg) and sweet lupins (120 g/kg). 5. The results of these experiments allowed tentative recommendations to be made to industry for inclusion rates of these cultivars of the 4 grain legumes. These were: field peas 300 g/kg; faba beans 200 g/kg, chick peas 100 g/kg and sweet lupins <100 g/kg. Wet droppings and high gut viscosity were serious problems with sweet lupins although these were not so obvious in experiment C.     

A comparative study of nutrients utilization, alkaline phosphatase activity and creatinine concentration in the serum of sheep and goats fed diets based on olive leaves

The aim of this study was to compare, in goats and wethers, the nutritive utilization of diets including olive leaves (OL) and the possible detrimental effect of that by-product. Three different diets were studied: OL, OL plus polyethylene glycol (PEG) (OLP) and OL supplemented with barley [164 g/kg dry matter (DM)] and faba beans (59 g/kg DM) (OLSUP). Apparent digestibility of nutrients and energy and nitrogen balances were determined along with creatinine concentrations and alkaline phosphatase (ALP) activity in the serum. The apparent digestibility of OL was low and similar in goats and wethers (54.4% and 53.5%, 22.2% and 21.6% and, 47.7% and 46.6% for DM, crude protein and neutral detergent fibre in goats and wethers, respectively). The addition of PEG did not improve (p > 0.05) digestibility of OL, although a slightly beneficial effect on the digestion of structural carbohydrates was observed (up to 8.4% and 7.10% in goats and wethers, respectively). The supplementation of OL with barley and faba beans increased (p < 0.001) the apparent digestibility of nutrients and the energy value. The consumption of the OL led to high ALP activity in the serum. Despite the higher sensitivity of wethers to Cu levels, our results show a similar digestive use of OL by wethers and goats and suggest the need of further comparative investigations focusing on the effect of the presence of high Cu levels in the by-product on the animal health.     

Comparative aspects of plant tannins on digestive physiology,nutrition and microbial community changes in sheep and goats: A review

Comparative aspects of plant tannins on digestive physiology, nutrition and microbial community in sheep and goats are discussed in the context of differences due to feed intake, digestibility, utilization of nutrients and microbial community. The purpose of this review was to present an overview of the potential benefits of tannin‐containing diets for sheep and goats and specie differences in their response to tannins. It is well established that moderate level of tannins in the diet (3%–4% tannins DM) can precipitate with soluble proteins and increase protein supply to the sheep, but comparative aspects of tannin‐containing diets in sheep and goats on animal performance, digestive physiology, rumen microbial changes and potential benefits to sustainable animal production by those compounds have received little attention. In addition, developing plant‐based tannin‐containing diets for control of rumen microbiota and rumen fermentation (e.g., methane gas) would be expected to have a greater impact on the ruminant health, productivity and emission of greenhouse gasses. The positive impacts of the plant tannin compounds mainly depend on their influence on the gut microbiome diversity and ability to generate fermentation end products (short‐chain fatty acids) that have diverse biological roles. Diets which contain optimal levels of tannins have potential benefits for sustainability of small ruminant production systems. However, there is a need for an improved understanding of the utilization of tannin‐containing forages to improve their management. This implies investigations of animal responses to tannin‐containing forages or browse species and, in particular, a better understanding of the interactions that can arise between sheep and goats on digestion, DMD, rumen fermentation and microbial community changes. This knowledge could help to improve current feeding systems in terms of efficiency of feed use and environmental impacts (reduce methane gas production) and thus contribute to the development of a sustainable sheep and goat production.     

Effect of pelleting and associations with maize or wheat on the nutritive value of smooth pea (Pisum sativum) seeds in adult cockerels

Four types of diet were tested: 960 g maize/kg (M), 960 g wheat/kg (W), 463 g maize added to 497 g of smooth peas/kg (PM) and 463 g wheat added to 497 g smooth peas/kg (PW). Three treatments were applied to each of these 4 diets: grinding (OP), one steam pelleting (1 P) and two successive steam pelleting (2 P). The pelleted diets were ground before feeding. Adult cockerels received all the diets whereas rats received only W and PW diets. Apparent metabolisable energy values corrected for N-equilibrium (AMEn), protein and starch digestibilities were measured in adult cockerels. Digestible energy (DE) values were measured in rats. The AMEn values of cereals remained practically unchanged by pelleting, whereas that of smooth peas was increased by between 1.8-4.6% after pelleting. Pelleting also induced 3.5 and 5.4% increases respectively in the digestibilities of pea protein and starch. Pelleting did not change the DE values measured in rats. The AMEn values of smooth peas mixed with maize were 4.6% higher than those of smooth peas mixed with wheat. The true digestibility of pea protein was 8.4% higher in the former mixture, whereas the pea starch digestibility remained unchanged. Calculation showed that most of the pea AMEn variations could be explained in terms of variations in protein and starch digestibilities.     

Variation in seed protein digestion of different pea (Pisum sativum L.) genotypes by cecectomized broiler chickens: 1. Endogenous amino acid losses, true digestibility and in vitro hydrolysis of proteins

The aim of this study was to investigate the cause of variation in the digestibility of pea protein in poultry and to find a tool to select genotypes with high digestibility potential by using an in vitro hydrolysis assay. Eight pea genotypes were selected for their difference in seed protein content and composition. To reduce the variation due to tannins and particle size, seeds from these 8 genotypes were dehulled and micro-ground. They were incorporated as the only protein source in 8 different experimental isoproteinaceous diets with similar metabolisable energy content. The amino acid digestibility was studied in cecectomized chickens. A balance method was used to obtain apparent digestibility, and the isotope dilution technique was used to determine endogenous losses and true digestibility, after feeding a double labelled test meal containing chromic oxide and ¹⁵N-labelled peas. The 8 diets showed differences in apparent amino acid digestibility. The average apparent digestibility for all amino acids varied between 79.5 and 86.3%, with the highest values for arginine (85.2 to 90.8%) and glutamic acid (85.2 to 90.5%), and the lowest values for cystine (63.3 to 69.7%) and tryptophan (69.1 to 80.3%). This variability of apparent amino acid digestibility was due to variations in endogenous losses and true digestibility among the 8 pea genotypes. The average endogenous losses as determined for 9 amino acids ranged from 3.6 to 5.4% of ingested amino acids, with the highest value for threonine (8.0 to 11.0%). The average true digestibility varied between 84.4 and 90.2%, with the highest values for lysine (89.0 to 95.0%), and the lowest for isoleucine (81.0 to 88.7%) and valine (82.4 to 88.7%). In vitro hydrolysis of protein from micro-ground seeds was performed for the 8 pea genotypes using three proteases (pepsin, trypsin and chymotrypsin). The quantity of small peptides (< 3 kDa) that appeared after the combined hydrolysis with pepsin (3 h) followed by trypsin and chymotrypsin (15 min) was significantly correlated with the average true digestibility of the 8 genotypes (R = 0.74; P < 0.05).     

Yttrium oxide (Y2O3) as an inert marker in digestibility studies with dogs, blue foxes and mink fed diets containing different protein sources

The study evaluated the use of yttrium oxide (Y(2)O(3)) as an inert marker in studies of apparent total tract digestibility in dogs, blue foxes and mink. Comparison was made with total faecal collection, and use of chromic oxide (Cr(2)O(3)) as marker respectively. Four experimental diets were added 0.1 g/kg yttrium oxide and 10 g/kg chromic oxide and fed to four animals of each species. Faecal recovery of yttrium oxide was 94.4% (SEM +/- 1.0), and of chromic oxide 105.8% (SEM +/- 1.5). The digestibilities of dry matter, crude protein, crude fat, starch and total carbohydrates obtained by total collection and yttrium oxide as marker showed close similarity, and in most cases not significant differences, independent of species and diets. In dogs, overall digestibilities of main nutrients with chromic oxide as marker were not significantly different from overall means obtained with yttrium oxide (p > 0.05). Overall digestibility of dry matter, crude protein and total carbohydrates in blue foxes and mink was significantly higher with chromic oxide than with yttrium oxide (p < 0.05). In dogs and blue foxes, digestibilities of individual amino acids determined by use of yttrium oxide were not different from values obtained using total collection of faeces, both within diets and for overall mean (p > 0.05). Overall amino acid digestibilities in dogs determined with chromic oxide as marker were similar to corresponding figures for yttrium oxide, whereas use of chromic oxide resulted in significantly higher digestibilites for a number of amino acids compared with yttrium oxide in foxes and mink (p < 0.05). The digestibilities of most main nutrients and amino acids revealed no interaction between diet and method (p > 0.05). The study showed that yttrium oxide can be used in low concentration in the feed, and allows high accuracy of analyses and thereby precise digestibility determination. It is concluded that yttrium oxide is an alternative inert marker to chromic oxide in the studied species.