Effect of viscosity on digestion of nutrients in conventional and germ-free chicks.

A study was conducted with conventional and germ-free broiler chicks to obtain more information on the role of the intestinal microflora in the anti-nutritive effects of NSP in broiler chicks. As the NSP source, highly methylated citrus pectin (HMC) was used at a dose level of 30 g/kg in a maize-based diet. The diets fed to the germ-free chicks were gamma-irradiated, whereas those fed to the conventional chicks were not. Feeding the HMC diet to conventional birds depressed weight gain and food utilization (P < 0.05), whereas in germ-free birds only weight gain was reduced (P < 0.05). Feeding the HMC diet to conventional birds reduced digestibilities of energy and starch at the end of the jejunum. Ileal digestibilities of starch and energy were not strongly affected when birds were fed on the HMC-containing diet. Faecal digestibilities of organic matter, crude fat, starch and amino acids, N retention and metabolizable energy were reduced when conventional chicks were fed on the HMC diet. Feeding the HMC diet to germ-free birds hardly affected faecal digestibility of nutrients and N retention, whereas metabolizable energy was increased. Feeding the HMC diet to conventional or germ-free birds increased the viscosity of the digesta in the small intestine. This increase in digesta viscosity was more pronounced in conventional than in germ-free birds. The pH of ileal digesta was reduced when HMC was added to the diet of conventional chicks, but not in germ-free chicks. Feeding the HMC diet to conventional birds markedly affected morphology of the gut wall, whereas in germ-free chicks very little effect was found on gut morphology. Based on the results of the present study, it is concluded that the gastrointestinal microflora mediates the magnitude of the anti-nutritive effects of HMC in broiler chicks. However, the exact role of the microflora in chicks in the magnitude of the anti-nutritional effects of HMC could not be derived from the present study, since the results might have been influenced by gamma-irradiation of the diets fed to the germ-free chicks.

Effect of dietary high- and low-methylated citrus pectin on the activity of the ileal microflora and morphology of the small intestinal wall of broiler chicks.

1. A study was conducted with broiler chicks to evaluate the effects of dietary high-methylated citrus pectin (HMC) or low-methylated citrus pectin (LMC) on the performance, nutrient digestibility, morphology of the small intestinal wall and ileal microbial activity. 2. Both pectin products were tested at a dietary content of 30 g/kg using a diet based on maize and soya flour. 3. Inclusion of HMC in the diet depressed weight gain and food utilization significantly. With a dietary addition of LMC there were only small decreases in weight gain and food utilisation. 4. Digestibility of dry matter, organic matter, crude fat, starch and amino acids, nitrogen retention and metabolisable energy value were reduced significantly when HMC was added to the diet. The addition of LMC to the diet reduced fat and ash digestibility and metabolisable energy value significantly. 5. Inclusion of LMC in the diet increased ileal viscosity marginally, whilst HMC had such an effect that the supernatant could not be extracted. Microbial activity in the ileum, particularly that of Enterococci, Bacteroidaceae, Clostridia and E. coli, was increased significantly with dietary addition of HMC. Inclusion of LMC in the diet did not greatly affect microbial activity as only the number of Clostridia was increased. 6. The addition of HMC to the diet markedly affected the morphology of the intestinal wall and significantly increased the number of goblet cells per 100 villus cells and the sucrase isomaltase activity was increased significantly. However, the morphology of the intestinal wall was hardly affected by LMC, whereas the number of goblet cells per 100 villi cells was significantly increased. 7. Results of the present study indicate that the inclusion of water-soluble pectins in diets of chicks changes ileal microbial activity and the morphology of the small intestinal wall. The magnitude of these changes depends on the degree of methylation of the pectins.

Ideal amino acid profile and dietary lysine specification for broiler chickens of 20 to 40 days of age.

1. The aim of the study was to determine the ideal ratio of the essential amino acids lysine (Lys), methionine (Met), threonine (Thr), tryptophan (Trp), arginine (Arg), valine (Val) and isoleucine (Ile) and to assess the required dietary lysine concentration for optimum performance in broiler chickens of 2 commercial strains from 20 to 40 d of age. 2. An identical basal diet was used throughout all experiments. It consisted mainly of maize and soyabean meal and contained 172 g crude protein and 13.2 MJ AME(N) per kg. For each experiment, the basal diet was adequately supplemented with all essential amino acids except the one to be tested, which was supplemented in 6 graded concentrations in exchange for maize starch. One (Met, Trp, Arg, Val, Ile) or 2 (Lys, Thr) growth trials were conducted per amino acid tested and the response in weight gain, food: gain ratio, breast meat yield and abdominal fat were examined. 3. The ideal amino acid ratio relative to Lys (expressed as a percentage) was calculated to be 75% Met+Cys, 63% Thr, 19% Trp, 112% Arg, 71% Ile and 81% Val on a true faecal digestible basis when the data were subjected to broken-line regression analysis. From both lysine studies the concentration for optimum food: gain ratio was calculated, by exponential regression analysis, to be 11.5 g true faecal digestible lys per kg diet.

Requirement of the laying hen for apparent fecal digestible lysine.

A study was conducted to determine the requirement for lysine of a White Leghorn strain of hens with a body weight of approximately 1,600 g. Before starting the experiment, apparent fecal digestibility of amino acids of the basal diet was determined in an in vivo digestibility trial with six individually housed hens. The basal diet used was based on corn and soybean meal and contained 0.65% total and 0.49% apparent fecal digestible lysine. To the basal diet, seven graded dose levels (0.04, 0.08, 0.12, 0.16, 0.20, 0.24, and 0.28%) of lysine as L-Lysine x HCl were added. The experimental diets were fed for 12 wk, covering the early stage of laying from 24 to 36 wk of age. Each experimental diet was fed to 60 individually caged housed birds. The dietary lysine requirement was found to be higher for maximizing efficiency of feed utilization than for obtaining maximum egg mass yield. Based on the feed conversion efficiency and at an egg mass yield of 57 g/hen-d, the requirement for total lysine was estimated to be about 900 mg/hen-d. From the results of the digestibility trial, it was calculated that the estimated requirement for total lysine was equivalent to 720 mg apparent fecal digestible lysine per hen-day.

Replacement value of betaine for DL-methionine in male broiler chicks.

The effect of DL-methionine and betaine supplementation on growth performance of 2,400 male broilers in the age period of 1 to 38 d, and on carcass composition of a subsample of 384 birds was examined. Three dose levels of DL-methionine (0, 0.05, and 0.10%) and two doses of betaine (0 and 0.04%) were supplemented in different combinations to methioninedeficient diets. Two types of diets were fed as starters and growers: either corn-soybean diets or practical diets typical for the Dutch broiler industry. All diets were fortified with 220 ppm choline in order to avoid a deficiency in methyl groups. Increasing DL-methionine supplementation significantly improved daily weight gain and feed conversion efficiency. Supplemental betaine did not affect bird growth. Betaine slightly improved feed conversion in diets without supplemental DL-methionine, but did not affect this parameter in diets with added DL-methionine. Breast meat yield was significantly increased by about 1.5 percentage points by the addition of 0.05% DL-methionine, whereas 0.04% betaine only tended to increase breast meat yield in the range of 0.3 to 0.6 percentage points. The type of diet did not have any effect on the responses obtained. In summary, there was no evidence for betaine to spare DL-methionine as an essential amino acid supplement in broiler diets.

Effects on chick performance and nutrient digestibility of an endo-xylanase added to a wheat- and rye-based diet in relation to fat source.

1. A study with growing chicks investigated the effects of an inclusion of an endo-xylanase preparation (LYXASAN) to a wheat- and rye-based diet on performance and nutrient digestibility in relation to the fat source. 2. The basal diet contained 500 g wheat and 100 g rye/kg of diet. The basal diet was supplemented with either 65 g soya oil/kg or 60 g blended animal fat and 5 g soya oil/kg. 3. Endo-xylanase added to the soya oil diet did not affect weight gain, but there was a numerical improvement in food conversion efficiency which was not statistically significant. When the endo-xylanase preparation was added to the blended animal fat diet, both weight gain and food utilisation were improved by 9.5% and 6.0%, respectively (P < 0.05). 4. Digestibilities of organic matter, crude fat, crude fibre and NFE were not significantly affected by adding endo-xylanase to the soya oil diet. However, when endo-xylanase was included in the blended animal fat diet, digestibility of organic matter, crude fat, crude fibre and NFE were improved (P < 0.05). The improvement in fat digestibility was the most pronounced, amounting to 9.4%. Nitrogen retention and metabolisable energy content were improved significantly by the addition of an endo-xylanase to the animal fat diet (P < 0.05), by 6.6% and 6.5% respectively. 5. From the results of this study, it can be concluded that the effects on chick performance and nutrient digestibility of a dietary endo-xylanase in a wheat- and rye-based diet are influenced to a considerable degree by the type of fat in the diet.

Nutritional implications of pectins in chicks in relation to esterification and origin of pectins.

An experiment was conducted to examine the effect of feeding high-methylated (HM) and low-methylated (LM) pectin on performance and physiological characteristics in broiler chicks. Two levels each (1.5 and 3%) of HM citrus pectin (HMC), LM citrus pectin (LMC), or HM sugar beet pectin (HMS) were added to a semi-purified basal diet. The experiment was conducted in battery brooders, and chicks received the diets as pellets from 6 to 27 d of age. The inclusion of LMC or HMS in the diet had little or no effect on the performance of chicks; however, when HMC was added to the diet growth and feed utilization were reduced significantly (P < 0.05). Water intake and water:feed ratio were increased (P < 0.05) after inclusion of all three pectin products in the diet. The effect on water consumption was more pronounced in the HMC-containing diets than in the LMC or HMS diets, and was dose-dependent. In vitro viscosity was increased significantly by incorporating HMC or LMC into the diet, whereas HMS had no effect on this parameter. Waterholding capacity of the diets and the excreta were increased significantly by including one (P < 0.05) of the three pectin products in the diet. The concentration of some of volatile fatty acids (VFA) in the cecal chyme was markedly decreased (P < 0.05) by feeding HMC, whereas LMC had no effect (P > 0.05) on the concentration of VFA. In contrast, inclusion of HMS in the diet significantly increased the concentration of VFA in the cecal content (P < 0.05) dose-dependently. Based on the results of the present study, it can be concluded that the effect of dietary pectin on chick performance is dependent on the degree of carboxyl groups that is esterified, the origin of the pectin product, and the amount added to the diet.

Energy metabolism in relation to physical activity in growing pigs as affected by type of dietary carbohydrate.

The effect of dietary carbohydrate source on physical activity in relation to metabolic rate in pigs was studied. Six groups of 12 pigs (50-kg, castrated males) were fed one of two diets: a starch diet or a non-starch polysaccharide (NSP) diet. Both diets had a similar calculated net energy content. The starch diet contained 13% tapioca, and the NSP diet contained 17% sugar beet pulp silage. Pigs were housed in groups and fed at approximately two times maintenance (approximately 900 kJ ME.kg-.75.d-1). Nitrogen and energy balances were measured per group during a 7-d experimental period, which was preceded by a 2-wk adaptation period. Heat production and physical activity were measured during successive discrete 9-min intervals. Metabolizability of gross energy was 79.4% and 78.2% for the starch-fed and NSP-fed pigs, respectively (P < .10). Activity differed between treatments. Activity-related heat production tended to be higher for the starch-fed pigs than for those fed the NSP diet (P < .10); 118 and 90 kJ.kg-.75.d-1, respectively. During the dark phase of the day (from 2000 to 0800) activity-related heat production was 8 kJ.kg-.75.d-1 higher for the starch fed pigs than for those fed the NSP diet (P > .1) whereas during the light phase, this difference was 48 kJ.kg-.75.d-1 (P < .10). Retained energy was similar for both treatments. These results show that dietary composition can change physical activity of pigs and thereby affect their energy utilization.

Effects of dietary sulphur-containing amino acids on performance and breast meat deposition of broiler chicks during the growing and finishing phases.

1. Two growth trials were performed to measure the effects of dietary methionine and cystine (SAA) on growth rate, food conversion efficiency and breast meat deposition in male broilers. 2. In experiment 1, broilers were grown on 6 experimental diets covering a range from 6.9 to 9.6 g SAA/kg. The diets were fed from 15 to 33 d of age. Similarly, in experiment 2, 6 diets containing 6.0 to 8.5 g SAA/kg were fed to finishing broilers 33 to 43 d of age. In each experiment 60 birds per treatment were processed, and carcase yield and breast meat percentage were determined. 3. Significant responses in weight gain, efficiency of food conversion and breast meat percentage were detected, which could be described well by exponential regression curves. Dietary SAA requirements to obtain maximum efficiency of food utilisation and maximum breast meat deposition were estimated to be about 9.0 g/kg from 15 to 33 d of age, and about 8.0 g/kg from 33 to 43 d of age. 4. Economic aspects were considered to calculate optimum SAA specifications from the results. In both trials, the dietary optimum of SAA was found to be higher for birds to be further processed than for birds to be marketed as whole carcases.

Sulfur amino acid requirement of broiler chicks from fourteen to thirty-eight days of age. 1. Performance and carcass yield.

Two experiments were conducted to evaluate increasing dietary levels of methionine and TSAA on broiler performance and carcass yield. In Experiment 1, the corn-soybean basal diet contained .75% TSAA, to which increasing dose levels of DL-methionine were added, providing at the highest supplemental level .95% TSAA. The experimental diets were fed for 20 d, covering the age period of 14 to 34 d. In Experiment 2, a corn-soybean basal diet containing .70% TSAA was used along with DL-methionine supplements to determine TSAA requirement during the age period of 14 to 38 d. The highest supplemental level of DL-methionine in this experiment provided .94% TSAA. The TSAA requirement was found to be higher for maximum efficiency of feed utilization and breast meat yield than for obtaining maximum weight gain. Based on feed conversion efficiency and breast meat yield, the requirement for TSAA was estimated to be at least .88% for the age period of 14 to 34 or 38 d. It was calculated that the estimated TSAA requirement was equivalent to approximately .75% apparent digestible SAA or .78% true digestible SAA.

Sulfur amino acid requirement of broiler chicks from fourteen to thirty-eight days of age. 2. Economic evaluation.

A calculation model was developed that can be used to derive dietary methionine and cystine (TSAA) levels for maximum profitability in growing broilers. Based on dose-response curves from two broiler experiments, the model calculates additional income from improved feed conversion and from increased breast meat yield. From the comparison of additional income to the additional cost associated with increasing dietary TSAA levels, the TSAA content giving maximum profit can be estimated. Under European price conditions, a dietary level of .95% TSAA was found to be most profitable for broilers grown to 1.7 kg (Experiment 1, 14 to 34 d of age), when only the feed conversion response to dietary TSAA was considered. In broilers grown to 2.2 kg (Experiment 2, 14 to 38 d of age), two situations were simulated. If only the feed conversion response was evaluated, the most profitable TSAA level would be .85%. If both feed conversion and breast meat responses were considered, a higher level of .89% TSAA would be optimum. Changing prices of input and output variables (broiler feed, breast meat, DL-methionine) affected the respective economic optimum level of dietary TSAA only slightly.

Response of broiler chicks to threonine-supplemented diets to 4 weeks of age.

1. Two experiments were carried out to determine the response of broiler chicks to threonine-supplemented diets between 10 and 28 d and 7 and 21 d of age, respectively. 2. In the first experiment female broiler chicks were fed on 11 experimental diets. Two iso-energetic basal diets (diets 1 and 2) were prepared with 200 and 160 g CP/kg and 7.6 and 6.0 g threonine/kg respectively. Both diets contained 11.5 g lysine and 8.7 g sulphur-containing amino acids/kg. Diet 3 was composed of diet 2, supplemented with all essential and non-essential amino acids (EAA and NEAA, respectively) except threonine, to the concentrations of the amino acids in diet 1. The NEAA were added as a combination of glutamic acid and glycine. Diets 4 to 11 had the same compositions as diet 3, but contained increasing amounts of threonine. 3. For birds fed on diet 2, gain was significantly lower and food/gain ratio was significantly higher than for birds fed on diet 1. Supplementation with EAA, NEAA and threonine to the same concentrations in diet 1 resulted in a performance similar to that found on diet 1. 4. In experiment 2, male and female broiler chicks both received 10 experimental diets. Diet 1 contained 220 g CP/kg and 8.5 g threonine/kg, diet 2 contained 160 g CP/kg from natural raw materials and 6 g threonine/kg. Both diets contained 12.4 g lysine and 9.3 g sulphur-containing amino acids/kg. Basal diet 2 was supplemented with all EAA and NEAA to the concentrations of basal diet 1, except for threonine. Diets 3 to 10 had the same compositions as the supplemented diet 2, but contained increasing amounts of threonine. 5. For male and female chicks on diet 2, gain was significantly lower and food/gain ratio significantly higher than those on diet 1. Diet 10 (160 g CP/kg plus all EAA, including threonine, and NEAA supplemented to the concentrations of diet 1) resulted in the same performance as diet 1. 6. The results indicate that, when low protein maize-soyabean meal diets supplemented with EAA and NEAA with 13.31 MJ ME/kg were fed to male and female broiler chicks until 21 d of age, improvements in gain and food/gain ratio were obtained when the dietary threonine content was increased to 7.25 g/kg. When female chicks were fed threonine-supplemented diets to 28 d of age, improvement in gain and food/gain ratio was obtained when the threonine concentrations were increased to 6.32 g/kg diet.(ABSTRACT TRUNCATED AT 400 WORDS)

Requirement of the laying hen for sulfur amino acids.

Two experiments with individually caged laying hens were conducted to determine the requirement for TSAA. In Experiment 1, the corn-soybean basal diet contained .48% TSAA to which increasing dose levels of DL-methionine were added providing at the highest supplemental level .645% TSAA. The experimental diets were fed for 12 wk, covering the early stage of laying from 25 to 37 wk of age. In Experiment 2, a corn-soybean basal diet containing of .51% TSAA was used along with DL-methionine supplements to determine TSAA requirement during the entire laying cycle of 52 wk (25 to 77 wk of age). The highest supplemental level of DL-methionine in this experiment provided .76% TSAA. The TSAA requirement was found to be higher for maximum efficiency of feed utilization than for obtaining maximum egg production. Based on feed conversion efficiency and at an egg mass yield of 55 g per hen-day, the requirement for TSAA was estimated to be about 740 mg per hen-day, of which about 440 mg was methionine, throughout a laying period of 52 wk. It was calculated that the estimated TSAA requirement was equivalent to approximately 660 mg true digestible SAA per hen-day.

Biological efficacy of L-lysine preparations containing biomass compared to L-lysine-HCl.

In two growth experiments on broilers of 6 to 27 days of age, the biological efficacy of three L-lysine preparations containing biomass was evaluated in comparison to L-lysine.HCl. L-lysine from the different sources was added in graded levels to a basal diet deficient in lysine, but adequate in all other nutrients. From multi-exponential regression analysis of weight gain and feed conversion responses, biological efficacy of the three L-lysine preparations containing biomass was estimated to be 97%, 103%, and 113%, respectively. None of these estimates was significantly different from 100%. Thus, it is concluded that the efficacy of the L-lysine preparations to deliver lysine is equivalent to L-lysine.HCl.

Nutritional implications of L-arabinose in pigs.

The pentose sugar L-arabinose is one of the most abundant components released by complete hydrolysis of non-starch polysaccharides of feed ingredients of vegetable origin. Two studies were conducted to investigate the apparent ileal digestibility and urinary excretion of L-arabinose at dietary inclusion levels of 50 and 100 g/kg, and 25, 50, 75 and 100 g/kg respectively, in pigs. As a reference, D-glucose was included in the studies. Water intake, ileal flow of volatile fatty acids and ileal and faecal digestibilities of dietary nutrients in pigs fed on the different diets were also examined. Castrated pigs were prepared with a post-valvular T-caecum cannula to measure ileal digestibility. Faecal digestibility was measured in non-cannulated pigs. Apparent ileal digestibility of L-arabinose was found to be approximately 70%. The presence of L-arabinose in the diet increased ileal flow of volatile fatty acids and lactic acid, suggesting the occurrence of microbial degradation of L-arabinose in the pig small intestine. L-arabinose was partly excreted in the urine. The extent of this urinary excretion as a percentage of intake increased linearly (P < 0.01) as the dietary level increased. In pigs fed on the 25 g L-arabinose/kg diet, 10.9% of the L-arabinose consumed appeared in the urine. This level was increased to 14.7% when pigs were fed on a diet containing 100 g L-arabinose/kg diet. Faecal digestibility and retention of nitrogen decreased significantly in pigs fed on the L-arabinose diets.

Nutritional value of D-xylose and L-arabinose for broiler chicks.

1. Two experiments were conducted to examine the effect of feeding D-xylose and L-arabinose on broiler performance, body composition, caecal length and weight, and liver weight. 2. Graded amounts (25, 50 and 75 g/kg) of D-xylose or L-arabinose were added to either a practical type (Exp. A) or a semi-purified (Exp. B) basal diet. As reference, a diet containing 75 g D-glucose/kg was included in both experiments, which were conducted in battery brooders, the birds receiving the isocaloric [on metabolisable energy (ME) basis] diets as dry mash ad libitum from 6 to 27 d of age. 3. A negative dose-dependent effect of both pentose sugars on weight gain and feed utilisation was observed. The same was true for daily food intake of the D-xylose diets. Water intake increased linearly (P less than 0.05) as the dietary concentrations of both pentose sugars was increased. Consequently, dry matter content of the droppings decreased. 4. Fat content of the chick body tended to decrease when either D-xylose or L-arabinose was included in the diets. 5. Caecal weight was increased markedly by feeding L-arabinose. Liver weight was not affected by feeding either D-xylose or L-arabinose to birds. 6. From data for ME intake and gain in body energy it was estimated that utilisation of the ME of both pentose sugars was inferior to that of D-glucose.

Nutritional implications of D-xylose in pigs.

Hemicellulose consists primarily of pentose sugars, joined together in a polysaccharide chain with D-xylose as the most abundant component. Ileal digestibility and urinary excretion of D-xylose and associated effects of this pentose sugar on ileal and faecal digestibility of dry matter (DM), organic matter (OM), gross energy (GE) and nitrogen were studied in pigs. Castrated pigs were prepared with a post-valvular T-caecum cannula to measure ileal digestibility. Faecal digestibility was measured in non-cannulated pigs. D-Xylose was given at dietary inclusion levels of 100 and 200 g/kg, and the control sugar, D-glucose, at a rate of 200 g/kg diet. Ileal digestibility of D-xylose as well as that of D-glucose was found to be close to 100%. The presence of D-xylose in the diet decreased ileal digesta pH and increased ileal flow of volatile fatty acids, suggesting the occurrence of microbial degradation of D-xylose in the pig small intestine. In pigs fed on the 100 g D-xylose/kg diet, 44.5% of the D-xylose intake appeared in the urine. This percentage increased significantly to 52.6 when pigs were fed on the 200 g D-xylose/kg diet. Ileal and faecal digestibility of DM, OM, GE and N, as well as N retention, decreased significantly in pigs fed on the 200 g D-xylose/kg diet.

Ileal digestibility and urinary excretion of D-xylose and L-arabinose in ileostomized adult roosters.

An experiment with ileostomized adult roosters was conducted to determine the ileal digestibility and urinary excretion of D-xylose and L-arabinose. As a reference, D-glucose was included in the experiment. The sugars were tested at graded dietary levels of 2.5, 5.0, 7.5, and 10.0%. Mean ileal digestibility of D-glucose and D-xylose was nearly 100%. Ileal digestibility of L-arabinose decreased linearly (P less than .05) with increasing dose level. The corresponding ileal digestibilities for L-arabinose at dietary levels of 2.5, 5.0, 7.5, and 10.0% were 95.5, 93.6, 80.3, and 74.6%. Both pentose sugars were partly excreted in the urine. The extent of this urinary excretion in percentage of intake increased linearly (P less than .05) as the dietary level increased. In roosters fed the 2.5% D-xylose diet, 7.2% of the D-xylose consumed appeared in the urine. This level increased to 20.2% when roosters were fed a diet containing 10.0% D-xylose. Corresponding values for L-arabinose at these dietary inclusion levels were 8.7 and 16.6%.

Nutritional implications and metabolizable energy value of D-xylose and L-arabinose in chicks.

An experiment was conducted to examine the effects of graded levels (2.5, 5.0, 7.5, 10.0, and 15.0%) of dietary D-xylose or L-arabinose on chick performance. As reference, D-glucose was included in the experiment. A second experiment was performed to determine the AMEn of D-xylose and L-arabinose. Results of Experiment 1 showed a significant linear decrease (P less than .05) in weight gain and efficiency of feed utilization when the dietary level of either D-xylose or L-arabinose was increased. The same was true for daily feed intake of the D-xylose treatments. Water intake was linearly (P less than .05) increased as dietary level of both pentose sugars increased, and, as a result, dry matter content of the droppings decreased. Results of Experiment 2 showed that the AMEn value of either pentose sugar was dose related. The AMEn values for D-xylose at 5 and 10% dietary inclusion were 2,660 and 2,020 kcal/kg, respectively. Those for L-arabinose at these inclusion levels were 2,300 and 1,360 kcal/kg, respectively. Feeding equal dietary levels of either pentose sugar resulted in higher concentrations of xylose than of arabinose in blood plasma. Concentration of glucose in blood was not affected by feeding either D-xylose or L-arabinose. Cecal length and weight were markedly increased by feeding L-arabinose and intermediately by D-xylose.

Cholesterol metabolism, digestion rates and postprandial changes in serum of swine fed purified diets containing either casein or soybean protein.

Swine fitted with re-entrant ileo-cecal cannulas were fed purified diets containing either casein or soybean protein to study possible relations between cholesterol metabolism, digestion of dietary constituents and postprandial patterns of various serum components. Compared with soybean protein, dietary casein produced an increase in serum total cholesterol in which the excess cholesterol was located in the low density lipoprotein fraction. Ileal and fecal excretion of neutral steroids was diminished in pigs fed casein, suggesting that cholesterol absorption was stimulated. The apparent ileal absorption of protein was increased in pigs fed casein. The enhanced absorption of cholesterol and protein was associated with a reduced rate of flow of chyme through the ileum. The output of bile acids in the feces of pigs fed casein was decreased, whereas the ileal output was not significantly affected. This could be attributed to increased uptake of bile acids from the cecum and/or colon, which may in part be related to the indirectly observed decreased formation of secondary bile acids. Postprandial serum concentrations of insulin and glucose were temporarily increased in pigs fed casein, whereas those of triglycerides were decreased. We suggest that the decreased excretion of cholesterol and bile acids is the major determinant of casein-induced hypercholesterolemia in swine.