Weight Of Digesta Research Articles

Effect of forage particle length on rumen fermentation, sorting and chewing activity of late-lactation and non-lactating dairy cows

The objective of this study was to determine the effects of varying forage particle length on chewing activity, sorting behavior, rumen pH and rumen fill in late lactation and dry dairy cattle, fed rations with similar physically effective NDF but different mean particle length. Treatments consisted of three diets differing only in geometric mean length of forage: hay (5.40, 8.96 and 77.90 mm, for short (S), medium (M) and long (L) diets, respectively) for Experiment 1 (E1), and straw (10.16, 24.68 and 80.37 mm) for S, M and L diets, respectively, for Experiment 2 (E2). Hay or straw comprised the sole source of forage (50% and 75% of ration dry matter (DM) for E1 and E2, respectively). Both experiments used three rumen cannulated Holstein dairy cows, in late lactation for E1 and dry in E2, with 3 × 3 Latin square designs with 14 day periods. In E1, DM intake (DMI; 18.3 ± 2.1 kg/day; mean ± s.e.), pH (6.4 ± 0.1), time spent eating (280 ± 22.5 min/day), time spent ruminating (487 ± 17 min/day), and total time spent chewing (767 ± 34 min/day) were not different, whereas eating minutes per kilogram of DMI and NDF intake (NDFI) tended to increase linearly as forage length increased. Rumen digesta volume (l; 113.3 S, 117.8 M and 114.4 L ± 17.1) had a quadratic response, and rumen digesta weight tended to respond quadratically; however, differences were numerically small. In E2, DMI (8.3 ± 1.3 kg/day), pH (6.7 ± 0.1), time spent eating (236 ± 23.5 min/day), time spent ruminating (468 ± 45.2 min/day), total time spent chewing (704 ± 67.7 min/day) and minutes per kilogram NDFI were not different, whereas minutes per kilogram of DMI had a trend for a quadratic effect. Rumen digesta volume (111 ± 18.8 l) and weight (103 ± 17.4 kg) were not different. In both experiments, cows sorted against longer particles as determined by a particle length selection index; this behavior increased linearly as particle length increased. Greater forage particle length increased sorting behavior, but had no effect on rumen fermentation or chewing behavior.

Fructan extracts from wheat stem and barley grain stimulate large bowel fermentation in rats

The benefits of inulin-type fructans for bowel health are well established, but less so for other fructan sources. In vitro data suggest that fructans extracted from cereals are readily fermented and produce favorable short-chain fatty acid profiles; however, whether this occurs in vivo is unknown. We hypothesized that in rats, fructans extracted from wheat stem and barley grain would have similar effects on fermentation as oligofructose (OF). Fifty-six male Sprague-Dawley rats were randomly assigned to 1 of 7 dietary treatments that contained either 2% or 5% fructan, provided by a barley grain fructan extract (BGFE), a wheat stem fructan extract, or OF or no added fructan (control). The duration of the feeding study was 14 days. Rats fed diets containing 5% fructan had higher cecal digesta weights; larger acetate, propionate, and total short-chain fatty acid pools; and lower pHs in comparison with the control group. In addition, only the 5% OF and 5% BGFE groups increased cecal butyrate pools, and 5% BGFE was the only group in which colonic digesta pH was lower than that of the control. Diets containing 2% fructan did not affect any of these fermentation end points. Whereas bifidobacteria numbers in cecal digesta of 2% and 5% OF were higher than that in the control group, they were not different from those in rats fed diets containing BGFE and wheat stem fructan extract. Barley grain and wheat stem fructans produced similar large bowel fermentation patterns to OF when fed to rats at 5% of the diet.

Gastrointestinal Protozoa and Digestive Tract Parameters of Wild South African Warthogs (Phacochoerus aethiopicus)

The warthog (Phacochoerus aethiopicus) is a grazer and hindgut fermenter with an apparent unique population of protozoa; however, only a limited number of specimens have been studied to date. In addition to having a very low number of protozoal species, little is known about temporal (seasonal) variation and geographic variation in protozoan diversity. Forty-one warthogs were harvested over a two-year period (2003–2005) from a wildlife area owned by the South African Air force (Ditholo). Additional samples were obtained from three animals at a farm near Northam (2004), plus three animals from a game ranch (Knapdaar) near Ellisras (2010). Several physical parameters of the digestive tract were measured, i.e. pH, temperature, organ length, weight of organ contents, dry matter, density and digesta in vitro gas production. Samples were collected from the caecum and colon for protozoal counts. In the animals from Ditholo and Northam, Telamodinium onyx was present in 42 of the 44 animals and was the predominant species. Megadinium aethiopicum was observed in 33 animals and Teratodinium sphaeredon was present in 10 of the warthogs. Blepharoconus krugerensis was present in four animals. A single species of both Cyclopostidae and Isotricha were present in two separate animals. In the warthogs harvested at Knapdaar, T. onyx, M. aethiopicum and B. krugerensis were present in all three animals, while M. sphaeredon was present in only two. Unexpectedly, the species Blepharosphaera intestinalis and Charonina equi were found in all three animals. Concentration of protozoans in caecum/colon fluid averaged about 25 × 103 per ml. In conclusion, the larger number of animals studied established that there can be considerable protozoan diversity among animals and that both seasonal and geographic variation occur.

Gastrointestinal protozoa and digestive tract parameters of wild South African warthogs (Phacochoerus aethiopicus)

The warthog (Phacochoerus aethiopicus) is a grazer and hindgut fermenter with an apparent unique population of protozoa; however, only a limited number of specimens have been studied to date. In addition to having a very low number of protozoal species, little is known about temporal (seasonal) variation and geographic variation in protozoan diversity. Forty-one warthogs were harvested over a two-year period (2003–2005) from a wildlife area owned by the South African Air force (Ditholo). Additional samples were obtained from three animals at a farm near Northam (2004), plus three animals from a game ranch (Knapdaar) near Ellisras (2010). Several physical parameters of the digestive tract were measured, i.e. pH, temperature, organ length, weight of organ contents, dry matter, density and digesta in vitro gas production. Samples were collected from the caecum and colon for protozoal counts. In the animals from Ditholo and Northam, Telamodinium onyx was present in 42 of the 44 animals and was the predominant species. Megadinium aethiopicum was observed in 33 animals and Teratodinium sphaeredon was present in 10 of the warthogs. Blepharoconus krugerensis was present in four animals. A single species of both Cyclopostidae and Isotricha were present in two separate animals. In the warthogs harvested at Knapdaar, T. onyx, M. aethiopicum and B. krugerensis were present in all three animals, while M. sphaeredon was present in only two. Unexpectedly, the species Blepharosphaera intestinalis and Charonina equi were found in all three animals. Concentration of protozoans in caecum/colon fluid averaged about 25 × 103 per ml. In conclusion, the larger number of animals studied established that there can be considerable protozoan diversity among animals and that both seasonal and geographic variation occur.

An arabinoxylan-rich fraction from wheat enhances caecal fermentation and protects colonocyte DNA against diet-induced damage in pigs

Population studies show that greater red and processed meat consumption increases colorectal cancer risk, whereas dietary fibre is protective. In rats, resistant starches (a dietary fibre component) oppose colonocyte DNA strand breaks induced by high red meat diets, consistent with epidemiological data. Protection appears to be through SCFA, particularly butyrate, produced by large bowel carbohydrate fermentation. Arabinoxylans are important wheat fibre components and stimulate large bowel carbohydrate SCFA production. The present study aimed to determine whether an arabinoxylan-rich fraction (AXRF) from wheat protected colonocytes from DNA damage and changed colonic microbial composition in pigs fed with a diet high (30 %) in cooked red meat for 4 weeks. AXRF was primarily fermented in the caecum, as indicated by higher tissue and digesta weights and higher caecal (but not colonic) acetate, propionate and total SCFA concentrations. Protein fermentation product concentrations (caecal p-cresol and mid- and distal colonic phenol) were lower in pigs fed with AXRF. Colonocyte DNA damage was lower in pigs fed with AXRF. The microbial profiles of mid-colonic mucosa and adjacent digesta showed that bacteria affiliating with Prevotella spp. and Clostridial cluster IV were more abundant in both the mucosa and digesta fractions of pigs fed with AXRF. These data suggest that, although AXRF was primarily fermented in the caecum, DNA damage was reduced in the large bowel, occurring in conjunction with lower phenol concentrations and altered microbial populations. Further studies to determine the relationships between these changes and the lowering of colonocyte DNA damage are warranted.

Dose-dependent Effects of Polyphenolic Extracts from Green Tea, Blue-Berried Honeysuckle, and Chokeberry on Rat Caecal Fermentation Processes

The physiological status of the colon or ceacum is known to be very important for the host organism. Therefore, the aim of this study was to estimate the influence of high doses of polyphenolic extracts from chokeberry (CH), blue-berried honeysuckle (H), and green tea (GT) on fermentation processes in the caecum and caecal parameters of rats fed casein diets. In a 4-week experiment, 35-day-old rats were fed diets containing 0.4, 0.8, and 1.2 % of pure polyphenols. The greatest weight of digesta was recorded in rats fed 1.2 % of GT extract, and these animals were also characterised by having the lowest content of dry matter. Supplementation of diets with the extracts of interest caused a reduction in pH values and ammonia concentrations in caecal digesta in comparison to control animals. The results of a two-way analysis of variance indicated dose-dependent (except for 0.4 % supplementation) inhibition of enzymatic activity compared to control animals. Introduction of CH and H extracts significantly reduced the activity of β-glucuronidase compared to rats fed tea diets. Two-way analysis of variance showed a significant decrease in volatile fatty acids concentration in rats fed diets supplemented with H and CH extracts in comparison to control and tea-fed rats. The obtained results showed that the extracts tested can distinctly influence caecal parameters and metabolism.

Fasting and refeeding modulate the expression of stress proteins along the gastrointestinal tract of weaned pigs

The gastrointestinal tract (GIT) of young mammals is submitted to aggressions early in life and GIT stress proteins are up-regulated in pigs following weaning. We hypothesized that transient food deprivation may contribute to these changes. Therefore, the effects of fasting and refeeding on GIT stress proteins in weaned pigs were investigated. A complete block experimental design with three groups of five pigs each was set up with the following treatments: A - food offered, B - fasted for 1.5 days, C - fasted for 1.5 days and then re-fed for 2.5 days. After slaughter, the GIT was removed, weighed and sampled. Intestinal villi and crypts were measured and alkaline phosphatase activity was determined. GIT tissue stress protein concentrations were measured by Western blotting. Fasting led to intestinal mucosa and villous-crypt atrophy (p < 0.01) and reduced mucosal alkaline phosphatase total activity in the proximal small intestine (p < 0.05). Heat shock proteins HSP 27 and HSP 90 (but not HSP 70) and neuronal NO synthase (nNOS) increased (p < 0.01) in the stomach, mid-intestine and proximal colon with fasting. Inducible NOS (iNOS) did so in the stomach (p < 0.001). Refeeding partially or totally restored GIT characteristics and stress protein concentrations, except for gastric HSP 90 and iNOS. Significant correlations (p < 0.05 to p < 0.0001) were found among stress proteins, between nNOS and digesta weight, between HSP 27 or HSP 90 and intestinal mucosa weight, and between intestinal or colonic HSP or nNOS and alkaline phosphatase. In conclusion, fasting and refeeding modulate GIT HSP proteins and nNOS in pigs following weaning. Changes in digesta and intestinal mucosa weights and alkaline phosphatase activity may be involved in the modulation of stress proteins along the GIT.

Butyrylated starch increases large bowel butyrate levels and lowers colonic smooth muscle contractility in rats

The short-chain fatty acids acetate, propionate, and butyrate are produced by colonic bacterial fermentation of carbohydrates. Butyrate is important in the regulation of the colonocyte cell cycle and gut motility and may also reduce the risk of large bowel cancer. We have shown that dietary butyrylated starch can deliver butyrate to the large bowel in a sustained manner. We hypothesized that ingestion of butyrylated starch increases large bowel butyrate levels and decreases colonic contractility. Groups of male Sprague-Dawley rats (n = 8) were fed AIN-93G-based diet containing a highly digestible low-amylose maize starch (LAMS) control or 5% or 10% butyrylated LAMS (LAMSB) for 10 days. We found that cecal but not colonic tissue weight as well as cecal and distal colonic digesta weights and fecal output were higher in LAMSB fed rats. Butyrylated LAMS lowered digesta pH throughout the large bowel. Cecal, proximal, and distal colonic butyrate pools and portal venous butyrate concentrations were higher in rats fed LAMSB. Electrically stimulated and receptor-dependent carbachol and prostaglandin E(2)-induced isotonic contractions were lower in isolated intact sections of proximal colon (P < .05) but not the terminal ileum after 10% LAMSB ingestion. These results demonstrated that elevation of butyrate levels in the large bowel of the rat correlated with reduction of contractile activity of the colonic musculature, which may assist in the reabsorption of water and minerals.

Evaluation of Faba Beans, White Lupins and Peas as Protein Sources in Broiler Diets

2 Abstract: The aim of the present study was to evaluate the effect of the inclusion of faba beans (Vicia faba), white lupins (Lupinus albus) and peas (Pisum sativum) in two different basal diets on the performance, digestive tract development and carcass characteristics of broilers housed in floor pens over a 35 d grow-out period. The experimental design was a 2 x 4 factorial arrangement of treatments which evaluated two basal wheat-soy diets (with or without meat meal) and legume grains (no legume grain, or faba beans, white lupins and peas at 200 g/kg inclusion). All diets were formulated to contain similar levels of metabolizable energy and digestible amino acids. A 3-phase feeding programme (starter, grower and finisher) was employed. The starter, grower and finisher diets were offered from day 1-7, 8-21 and 22-35, respectively. During the starter period, legume x meat meal interaction was significant (p 0.05) on the performance and carcass recovery of broilers and the litter score. Weight gain and feed per gain of birds fed diets without meat meal were better (p<0.05) than those with meat meal. The main effect of legumes was significant (p<0.01 to 0.05) for the relative weight of liver and gizzard and the relative digesta weight of the crop and proventriculus. Birds fed meat meal diets had lower (p<0.05) relative weights of liver, pancreas and small intestine and relative digesta weight of small intestine than those fed diets with no meat meal diets. It was concluded that, when balanced for metabolizable energy and digestible amino acids, dietary inclusion of faba beans, white lupins and peas at 200 g/kg either in wheat-soybean meal or wheat-soybean meal-meat meal basal diets could support a good performance of birds over the 35-day grow-out period.

Winter diet and digestive tract of the Golden Pheasant (Chrysolophus pictus) in the Qinling Mountains, China

The winter diet and morphological structure of the gastrointestinal tract of the Golden Pheasant (Chrysolophus pictus) was investigated in the Qinling Mountains, Shaanxi Province in 2002/2003. Individual food items in crops were identified by species, where possible, using standard taxonomic methods. The Golden Pheasant consumes exclusively vegetarian foods in the winter, of at least 14 plant species, such as crops and other vegetable species. The digestive tract of the Golden Pheasant is composed of an oesophagus, a stomach, a relatively long intestine measuring 3.4 × standard body length, two fully-developed caeca and a relatively short colon, typical for herbivorous birds. Pebbles of different sizes (0.5-3 mm in diameter) were very frequent in the gizzard. The average dry weight of the pebbles was 10.4±2.5 g and was positively correlated with the weight of digesta in the gizzard (Pearson r=0.747, p＜0.01, n=37). The mucosa surface pH of the digestive tract of the Golden Pheasant was slightly acidic, but higher in the crop and gizzard.

Nutritional value of faba beans ( Vicia faba L.) for broilers: Apparent metabolisable energy, ileal amino acid digestibility and production performance

Two experiments were conducted to evaluate the nutritional value of four cultivars (PGG Tic, Spec Tic, South Tic and Broad) of faba beans ( Vicia faba L.) for broilers. In experiment 1, the apparent metabolisable energy (AME) and ileal amino acid digestibility coefficients of these four cultivars were determined. The cultivar effects were significant (P<0.05) for AME, but ileal amino acid digestibility coefficients were not different (P>0.05) between the four cultivars. The AME value of South Tic cultivar was higher (P<0.05) than those of Spec Tic and Broad cultivars, but similar (P>0.05) to that of PGG Tic. In Experiment 2, using the AME and ileal digestible amino acid values determined in Experiment 1, diets containing 200 g kg −1 of the four cultivars of faba beans were formulated and the effects of feeding these diets on the performance and the digestive tract development of broiler starters were investigated. Weight gain, feed intake and feed per gain of broilers fed faba bean diets were similar (P>0.05) to those fed the maize–soybean meal diet. The performance of birds fed diets containing different cultivars of faba beans was similar (P>0.05). In general, the digestive tract development was unaffected (P>0.05) by the inclusion of faba beans. The exceptions were the relative empty weight and digesta weight of gizzard which were found to be higher (P<0.05) in birds fed diets containing faba beans than those fed the maize–soy diet. Birds fed faba bean diets had better (P<0.05) excreta quality scores than that of the basal diet. These results suggest that faba beans are good sources of energy and amino acids, and that faba beans can be included at 200 g kg −1 inclusion level as a partial replacement for soybean meal in broiler diets without any adverse effects on the performance.

Cecal parameters of rats fed diets containing grapefruit polyphenols and inulin as single supplements or in a combination

Objective We compared the effects of grapefruit flavonoids and inulin, as single dietary components or in a combination, on cecal fermentation in rats adapted to a semipurified diet. Methods The experimental diets contained 0.3% flavonoid extract and 5% or 10% inulin and a combination of both supplements. The large bowel metabolism assessment was based on cecal parameters: bulk effect, pH, microbial enzymes activity, and short-chain fatty acid production. Results Both supplements induced significant enlargement of the cecal digesta weight. Acidification of cecal digesta was more pronounced, with a higher inulin addition to the diet. Cecal pH was the highest with the flavonoid-rich diets and lowest in the case of a simultaneous addition of flavonoids and a high content of inulin. The flavonoid extract applied as a single dietary supplement was observed to decrease the activity of bacterial β-glucosidase and β- and α-galactosidases in the cecal digesta. In contrast, addition of the grapefruit extract to inulin-containing diets increased the activity of α-glucosidase, α-galactosidase, and β-galactosidase. Great accumulation of cecal digesta in rats consuming the flavonoid-diet caused a considerable increase in the short-chain fatty acid pool, mainly acetic acid. Inulin added to the diet decreased the excessive enlargement of digesta caused by dietary flavonoids. Dietary addition of inulin to the flavonoid-diet also normalized hydration of cecal digesta and significantly decreased the pH of digesta. The presence of polyphenols in the inulin-containing diets did not change total short-chain fatty acid production in the cecum of rats. Conclusion Our results suggested that simultaneous intake of inulin and polyphenols can decrease the detrimental effects of the latter on cecal fermentation.

GASTROINTESTINAL MORPHOLOGY OF FEMALE WHITE-TAILED AND MULE DEER: EFFECTS OF FIRE, REPRODUCTION, AND FEEDING TYPE

We assessed variation in length, width, density, and surface enlargement factor of papillae; rumen and intestinal digesta weight; intestinal length; and intestinal tissue weight of reproductive and nonreproductive female whitetailed (Odocoileus virginianus) and mule deer (O. hemionus) using similar burned and unburned habitat. Deer were collected from study areas in Custer and Pennington counties, South Dakota, in and adjacent to a wildfire burn. Length of papillae and enlargement factor of papillae surface of white-tailed deer and mule deer were greater in burned than unburned habitat, and dry weight of rumen digesta of white-tailed deer was greater in unburned than burned habitat. Papillae surface enlargement factor, papillae length and width, and dry weight of rumen and intestinal digesta were greater for lactating than nonlactating white-tailed deer. Papillae density, intestinal digesta dry weight, and intestinal length were greater in mule deer than white-tailed deer. The mosaic pattern of the burned habitat was beneficial at the mucosal level for white-tailed and mule deer within 3 years postfire. Enhanced papillae morphology of lactating compared with nonlactating and pregnant deer was attributed to high nutritional demands associated with reproductive status. Papillae density may be more important in mule deer because of feeding strategy (concentrate selector‐intermediate feeder) compared to white-tailed deer (concentrate selector), whereas greater rumen digesta dry weight and intestinal length may be directly associated with size.

Effects of Fatty Acid Supplements on Feed Intake, and Feeding and Chewing Behavior of Lactating Dairy Cows

Saturated and unsaturated fatty acid supplements (FS) were evaluated for effects on feed intake, meal patterns, and chewing behavior. Eight ruminally and duodenally cannulated cows were used in a replicated 4×4 Latin square design experiment with 21-d periods. Treatments were control and a linear substitution of 2.5% fatty acids from supplemented saturated FS (SAT; prilled, hydrogenated free fatty acids) for partially unsaturated FS (UNS; calcium soaps of long-chain fatty acids). All rations contained identical forage and concentrate components including 37.2% forage and 13.5% cottonseed. Dry matter intake for SAT was not different from control, whereas increasing unsaturated FS linearly decreased dry matter intake by 3.2kg. Wet weight of ruminal digesta decreased linearly up to 11.3kg (13%) with increasing unsaturated FS. Adding supplementary fatty acids did not change meal number, meal length, or time between meals compared with control, but increasing unsaturated FS decreased meal size 0.22kg (9%) within FS. The SAT treatment increased time spent ruminating by 56 (10%) and 42 (7%) min/d compared with control and UNS, respectively. Increasing saturated FS did not affect frequency of rumination bouts or interval between bouts, but increased rumination bout length by 5.6min. Water intake was not affected by treatment, but increasing saturated FS linearly decreased the number of drinking bouts per day by up to 2.9 bouts (23%). Increased unsaturated fatty acid flow to the duodenum decreased feed intake by decreasing meal size, and increased saturated fatty acid flow to the duodenum increased rumination time per day by increasing rumination bout length.

A protein-free diet alters small intestinal architecture and digestive enzyme activities in rats

The consequences of feeding a protein-free (PF) diet, as compared to casein, on gut characteristics were studied in slightly energy-restricted rats fed similar amounts of feed for 10 d. The weight and pH of fresh digesta in the stomach were lower (P = 0.045 and P = 0.016). However, the weight of fresh digesta in the other segments and gut tissue weight were not significantly affected by the diet (P > 0.05). Small intestinal crypt depth, width and area were reduced by 13, 23 and 37%, respectively (P = 0.011, P = 0.004 and P = 0.001), and villus width tended to be smaller (P = 0.057), with the PF diet. Villus height to crypt depth ratio was also lower with the PF diet in the duodenum and ileum, respectively (P < 0.05). Finally, the specific activities of alkaline phosphatase and aminopeptidase N were reduced by 36 to 38% at different sites of the small intestine in the rats fed the PF diet (P < 0.05). In conclusion, chronic consumption of a protein-free diet altered the intestinal villus-crypt architecture and enzyme activities in rats.

Genotype, dietary manipulation and food allocation affect indices of welfare in broiler breeders

1. An experiment was performed to compare the welfare of three broiler breeder genotypes (Label Rouge (LA), experimental dwarf (ER) and standard (SR)) fed on a Control or high Fibre diet. The LA birds were fed ad libitum and the other groups were reared to their recommended body weight targets. A group of standard broiler breeders was also fed a restricted amount of food, but to a lesser degree than SR, to achieve the same proportion of body weight (SE) as ER relative to ad libitum-fed dwarfs based on previous research. LA, ER, SR and SE are referred to as ‘groups’ in the text. 2. Welfare was assessed by comparing time budgets and heterophil–lymphocyte ratios (HL ratios) at 5, 10 and 15 weeks and immune responses at 15 weeks of age. In addition the weight and water content of the gastrointestinal tract at 4-h intervals at the end of the experiment were studied in LA and SR fed on both diets. 3. Body weights of LA, ER and SR fed on the Fibre diets were depressed and LA ate less of the Fibre than the Control diet. The coefficient of variation of body weight at 15 weeks was 7·9% in LA and similar (10·8 to 11·6%) in the other groups. 4. Drinking, litter-directed behaviour, resting and standing were affected by a group × age interaction with restricted birds showing increased drinking over time and less time spent resting compared to LA. The behaviour of ER birds was similar to SE. 5. HL ratios were within the normal biological range although all restricted-fed birds had an elevated HL ratio at 10 weeks of age relative to week 5 whereas LA birds had a reduced HL ratio at 15 weeks relative to 5 and 10 weeks of age. Immune responses were lower in ER and SE and the highest response was in SR. 6. No effects of diet were identified on behaviour, white blood cell counts or HL ratio. 7. With the exception of the crop, the dry weights of digesta in each section of the gut were similar in LA and SR birds. The results suggest that drinker-directed activity might be a substitute for foraging rather than an attempt to increase gut fill. 8. It is concluded that the replacement of standard with dwarf broiler breeders may improve the welfare of commercial flocks of broiler breeders by decreasing the degree of food restriction resulting in favourable changes in behaviour, for example, reduced ‘drinker-directed’ behaviour.

The effect of feeding regimen on apparent and true ileal nitrogen digestibility for rats fed diets containing different sources of protein

AbstractA standard protocol is required for carrying out routine ileal nitrogen (N) digestibility rat bioassays. The aim of this study was to determine the effects of feeding regimen on ileal N digestibility in rats fed diets containing different protein sources and chromic oxide as an indigestible marker. The experimental design was seven diets (protein‐free (PF), enzyme‐hydrolysed casein (EHC), lactalbumin (LAC), wheat gluten (GLU), fish fillets (FIS), soy protein isolate (SOY), zein) by three feeding regimens (frequent, meal, ad libitum) with 10 rats per diet. In frequent feeding, food was provided for eight 10 min periods between 09:00 and 16:00; in meal feeding, food was provided for one 3 h period at 09:00; in ad libitum feeding, food was available at all times. Rats were fed for 8 days, killed and digesta were collected from the terminal 20 cm of the ileum. The diets and freeze‐dried digesta were then analysed for N and chromium (Cr). There were statistically significant effects of feeding regimen on ileal digesta weight, ileal N/Cr ratio and apparent (AND) and true (PF TND, EHC TND) N digestibility. Mean N digestibilities, averaged over four dietary treatments (LAC, GLU, FIS, SOY), for the frequent, meal and ad libitum feeding regimens respectively were: AND, 88.8, 90.4, 85.8; PF TND, 94.9, 96.4, 97.0; EHC TND, 92.7, 94.0, 95.6. Although the N digestibilities were higher for rats on meal feeding compared with frequent feeding, the only statistically significant differences were for the lactalbumin treatment, and these were small in absolute terms. This study demonstrated that meal feeding was suitable and frequent feeding was unnecessary for most protein sources tested, and that ad libitum feeding was not ideal because of the smaller and more variable quantities of digesta collected and the more variable ileal N/Cr ratios.© 2002 Society of Chemical Industry

The effect of digesta sampling time and dietary protein source on ileal nitrogen digestibility for the growing rat

AbstractThe effect of time that digesta were collected on the quantity and representativeness of ileal digesta and on the determination of apparent and true ileal nitrogen (N) digestibility for growing rats was investigated. Semi‐synthetic diets containing chromic oxide as an indigestible marker were given to 200 g live weight rats for 8 days as a single daily meal. The experimental treatments comprised six diets (lactalbumin, soy protein isolate, wheat gluten, fish, protein‐free (PF), enzymically hydrolysed casein (EHC)) and four ileal digesta sampling times (3, 4, 5 and 6 h after the start of feeding). On the eighth day the rats were fed and slaughtered according to treatment, and digesta were sampled from the terminal ileum. Endogenous ileal nitrogen excretion was determined using both the protein‐free and peptide alimentation methods. There was a significant (P = 0.027) effect of experimental diet averaged across sampling times for chromium recovery (CrRec). The CrRec was higher for the rats fed the PF diet than for the other diets. Responses to sampling time varied significantly (P &lt; 0.05) among diets for ileal digesta weight (IDW), nitrogen/chromium (N/Cr) ratio, ileal digesta weight relative to dry matter intake (IDW/DMI), CrRec, N flow, apparent N digestibility and true N digestibility (determined using the protein‐free method). The optimal digesta sampling times for each of the diets were 3 h for PF, EHC, lactalbumin and fish and 4 h for soy protein isolate and wheat gluten. Consequently, 3 or 4 h after the start of feeding is recommended as the optimum ileal digesta sampling time for most purified protein sources when fed to the growing rat as a single daily meal.© 2002 Society of Chemical Industry

Dietary carbohydrates affect caecal fermentation and modify nitrogen excretion patterns in rats II. Studies with diets differing in protein quality

In 2 two‐factorial experiments, each conducted on 80 growing male rats, the effects of substituting 10% raw potato starch (PS), pectins (PEC), or cellulose (CEL) for wheat starch (WS) and the addition of tannic acid to WS (WSTA) were studied using diets differing in protein quality. Casein unsupplemented or supplemented with DL‐methionine and gluten unsupplemented or supplemented with lysine, methionine and tryptophan were used as protein sources in Experiment 1 and 2, respectively. Parameters indicative of caecal fermentation intensity (pH, acetic, propionic and butyric acid contents, digesta and tissue weight) and of protein metabolism (urea blood concentration, faecal and urinary nitrogen excretion) were determined. Ten‐day balance experiments were preceded by a 10‐day adaption period to respective carbohydrates given in a diet containing balanced protein. In both experiments the type of carbohydrates affected the caecal concentration of individual and total SCFA and other parameters of fermentation intensity. Pectins and potato starch were fermented more intensively than cellulose. Faecal N excretion was increased by all carbohydrates substituted for cereal starch, and by tannic acid. Urinary excretion was greater on CEL than on PEC and WSTA containing casein and on other diets containing gluten. In both experiments urinary N excretion was the lowest on PEC diets. Protein quality had the greatest effect on apparent biological value and net protein utilization but all indices of protein utilization were also affected by carbohydrates. It is concluded that not only the amount of N excreted in faeces but also in urine is affected by the type and fermentability of carbohydrates.

Dietary carbohydrates affect caecal fermentation and modify nitrogen excretion patterns in rats I. studies with protein‐free diets

In a two‐factorial experiment on 96 young male rats, the effects of substituting 10% raw potato starch (PS), pectins (PEC), or cellulose (CEL) for corn starch (CS) were studied using an unsupplemented protein‐free (PF) diet or a PF diet supplemented either with DL‐methionine or urea. The pH and the short chain fatty acids (SCFA) content in caecal digesta, as well as caecal digesta and tissue weights were determined and used as the criteria of caecal fermentation intensity. Blood urea level, amount of N excreted via faeces and urine, DAPA content, and amino acid composition of faecal protein were analyzed as indices of protein metabolism. A 10‐day adaptation period to the carbohydrates fed with the casein diet preceded the experimental period of feeding the respective carbohydrates with protein‐free diets. Dietary carbohydrates significantly influenced total and individual SCFA content in caecal digesta, as well as other parameters related to the intensity of fermentation. Potato starch and pectins were more intensively fermented than cellulose. Supplementation of the PF diet with methionine and urea affected only caecal isobutyric and valeric acid content in a way dependent on the carbohydrates present in the diet. Carbohydrates significantly altered the routes of N excretion. Faecal excretion was increased by all carbohydrates studied compared to corn starch, pectins had the most marked effect. Urinary excretion was significantly increased by cellulose (as compared with the PEC and PS groups) and decreased by pectins as compared with all other groups. There was an interaction between the effects of carbohydrates and type of protein‐free diet on faecal and urinary excretion. The sum of amino acids in faecal protein was the lowest on the PEC diet, but the amino acid composition expressed as a per cent of total amino acid content was similar in all groups. It can be concluded that dietary carbohydrates alter the excretion patterns of endogenous nitrogen in rats in different ways and that this effect is related to the intensity of their fermentation in the hind gut.