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PubMed1976

The effect of cold exposure of sheep on digestion, rumen turnover time and efficiency of microbial synthesis.

1. Six closely shorn sheep were given brome grass (Bromus inermis) pellets at 1 h intervals and maintained at ambient temperatures of --I to Idegree and 18--21degrees for 28 d. Measurements of digestion were made during the last 10 d of temperature exposure. 2. Cold exposure resulted in a reduction in apparent dry matter (DM) digestibility from 0-482 to 0-450, and of apparent digestibility of organic matter (OM) from 0-511 to 0-477. Neither apparent digestibility nor retention of nitrogen was affected. 3. Apparent digestibility of OM in the rumen decreased from 0-300 to 0-242 with cold exposure, and was highly correlated with turnover time in the rumen of 103Ru, which was used as a particulate marker. 4. The efficiency of microbial synthesis (g N incorporated into microbial cells/kg OM apparently digested) was correlated with the dilution rate of the solute marker (51Cr) and with the turnover time of the particulate marker (103Ru) in the rumen. 5. Digestion in the intestine of DM and OM accounted for significantly more of apparent digestion in the whole gastrointestinal tract for sheep kept in the cold than for sheep kept in the warm. The apparent digestibilities of DM and OM entering the intestine were similar in sheep on both treatments, but significantly more non-ammonia-N was digested in the intestines of cold-exposed sheep. 6. The influence of dilution rate of rumen fluid on the efficiency of synthesis of microbial cells in the rumen is discussed.

Abomasum↗
PubMed1980

The nutritive value of silages. Digestion of organic matter, gross energy and carbohydrate constituents in the rumen and intestines of sheep receiving diets of grass silage or grass silage and barley.

1. Two experiments were conducted to study the digestion of organic matter, gross energy and carbohydrate constituents in the rumen, small intestine and caecum and colon of sheep given grass silage diets. Three silages made from perennial ryegrass (Lolium perenne) with formic acid as an additive were used. One was made from first-harvest grass in the spring and the others from regrowth grass cut from a single sward in either early autumn or late autumn. Expt 1 involved a comparison between the spring silage given alone or supplemented with barley (silage:barley, 4:1 dry matter (DM) basis). Expt 2 involved a comparison between the early-cut and late-cut autumn silages. 2. In Expt 1, supplementation of the silage with barley resulted in a non-significant (P > 0.05) reduction in the proportion of digestible energy (DE) and digestible organic matter digested in the rumen and an increase in the proportions digested in the small intestine. There were also pronounced effects of barley on ruminal cellulolysis and the proportion of digestible cellulose broken down in the rumen was reduced (P < 0.05) from 0.90 to 0.77. There was an increased passage of alpha-linked glucose polymers to the duodenum but even with the supplemented diet 0.91 of the dietary polymers were digested in the rumen. The molar proportion of propionic acid in the rumen tended to be reduced and there were increases in the proportions of butyric acid (P < 0.01) and acetic acid. 3. Expt 2, the digestibility of organic matter, gross energy and cellulose in the early-cut silage was higher (P < 0.01) than in the late-cut silage but there were no significant (P < 0.05) differences between silages in sites of digestion of these constituents. However, the molar proportion of acetic acid in the rumen was higher (P < 0.01) and the molar proportion of propionic acid was lower (P < 0.01) with the late-cut silage than the early-cut silage. 4. The results are discussed in relation to the voluntary intake and utilization of high-digestibility silages.

Animal Feed↗
PubMed1992

True protein digestibility and amounts of endogenous protein measured with the 15N-dilution technique in piglets fed on peas (Pisum sativum) and common beans (Phaseolus vulgaris).

The faecal and ileal true protein digestibilities of the raw pea (Pisum sativum) varieties finale and frijaune and the ileal true protein digestibility of steam-processed common beans (Phaseolus vulgaris) were measured in piglets using the 15N-dilution technique. The faecal true protein digestibility of both pea varieties was about 97. The ileal true protein digestibility was between 93 and 95, indicating that the pea protein is almost completely enzymically digested in the small intestine. The faecal apparent protein digestibility was 85 for both varieties while at the ileal level it was 79 and 74 respectively. The lower ileal apparent protein digestibility of peas can be attributed completely to the excretion of endogenous protein. The ileal apparent protein digestibility of toasted common beans was about zero (-4); the ileal true protein digestibility was about 66. This indicates that the protein of the common bean, although toasted, was highly resistant to enzymic digestion. It was calculated that per kg ingested bean protein, 340 g undigested bean protein and 700 g endogenous protein passed the terminal ileum. The results of the present study explain why in previous experiments a strongly reduced weight gain and even weight loss was observed in piglets fed on raw and toasted common beans.

Animals↗
PubMed1993

An integrated, dynamic model of feed hydration and digestion, and subsequent bacterial mass accumulation in the rumen.

Hydration of feeds and bacterial attachment to feed particles are thought to play major roles in rumen digestion of fibrous feedstuffs. The objective of the present study was to integrate these phenomena in a mechanistic model that could be used for data analysis. The proposed model was based on the conversion of biomass, where digestion end-products can be used for the synthesis of bacterial mass. Digestion of the potentially digestible fraction and subsequent accumulation of bacterial mass was based on a sequential, three-compartment model. These compartments represented substrate undergoing hydration, digestion, and bacterial mass accumulation. A fraction of the substrate was used for synthesis of bacterial mass. It was assumed that these bacteria associate either temporarily or permanently with the remaining substrate. Dacron bags containing either dry or fully-hydrated lucerne (Medicago sativa), maize (Zea mays) cobs, orchard grass (Dactylis glomerata), and wheat straw were incubated in the rumen of a steer that was infused continuously with (15NH4)2SO4. The 15N-enrichments of isolated particle-associated bacteria and residue remaining in the bags were used to estimate bacterial attachment. Substrate remaining and microbial mass accumulation were analysed simultaneously. Hydration did not appear to limit digestion. Fractional rate of digestion and appearance of attached bacterial mass was fastest for lucerne. For lucerne, 5% of the digestion end-products were used for synthesis of bacteria that associated with the substrate, whereas for maize cobs, orchard grass, and wheat straw this was 16, 14, and 19% respectively. Less than 2% of digestion end-products were used for synthesis of bacteria that permanently remained associated with the substrate. Permanent association can occur only with the indigestible fraction, and probably represents bacterial debris. Lysis and/or detachment of bacterial cells was highest for lucerne, and was indicative of the rapid dynamics of lucerne digestion.

Animal Feed↗
PubMed1993

Digestion of polysaccharides and other major components in the small and large intestine of pigs fed on diets consisting of oat fractions rich in beta-D-glucan.

The digestibility of polysaccharides and other major components and the metabolic response of the microflora in the small and large intestines to oat diets varying in mixed linked beta(1-->3; 1-->4)-D-glucan (beta-glucan) were studied in experiments with ileum-cannulated pigs. The oat fractions for diets were prepared in a dry milling process in which oat groats were milled into two endosperm fractions (oat flour 1 and oat flour 2) and oat bran. The digestibility of polysaccharides and the metabolic response of the microflora were followed for the two contrasting diets, oat flour 1 and oat bran, from ingestion to excretion while the digestibility of oat groats and oat flour 2 were estimated only at the ileum and in faeces. There was no degradation of beta-glucan from either oat flour 1 or bran in the stomach and the first, middle and distal thirds of the small intestine (average digestibility approximately 0), while in the terminal ileum digestibility increased to 0.30 to 0.17 respectively. The digestion of starch in the first third of the small intestine was lower for the high-beta-glucan oat-bran diet (0.49) than for the low-beta-glucan flour diet (0.64). However, digestibility differences between the two diets levelled out as the digesta moved aborally in the small intestine and the digestibility at the terminal ileum was almost complete (0.970-0.995) for all diets. Oat non-starch polysaccharides (NSP) were an easily digestible energy source for the microflora in the large intestine less than 13% of dietary NSP being recovered in faeces. The bulk of beta-glucan which survived the small intestine was degraded in the caecum and proximal colon while arabinoxylan was more slowly degraded. The amount of residues passing the ileo-caecal junction has little impact on the density of micro-organisms in the large intestine, which on the flour and bran diets were in the range of 10(10)-10(11) viable counts/g digesta, but a high impact on the activity of the flora in colon. Oat bran resulted in a higher proportion of butyric acid in large intestinal content compared with the flour diet. The faecal bulking effect of oat bran was mainly caused by an increased excretion of protein and fat, presumably of bacterial origin. Of all the diets tested the oat-bran diets had the lowest digestibilities of protein and fat at the terminal ileum and in the faeces.

Animals↗
PubMed1995

Intake, digestion and small intestinal protein availability in sheep in relation to ammoniation of wheat straw with or without protein supplementation.

The effects of ammoniation of wheat straw with or without supplementation of protein sources of either high (casein) or relatively low (potato protein) rumen degradability on intake and digestion were studied with four sheep in a 4 x 4 Latin square design. Rations offered were: (1) untreated wheat straw (UWS), (2) ammoniated wheat straw (AWS), (3) AWS supplemented with 3.2 g casein/kg live weight (W)0.75 per d (AWSC) and (4) AWS supplemented with 3.9 g potato protein/kg W0.75 per d (AWSP). Straw was offered ad lib. and all rations were supplemented with sugarbeet pulp and a mineral mixture. NH3 treatment increased intake and digestion. Supplementation of AWS with potato protein increased total digestible organic matter intake (DOMI) compared with AWS whereas supplementation with casein did not affect total DOMI. Protein supplementation of AWS significantly reduced rumen digestion of cellulose, and when the supplementation was with casein it reduced rumen digestion of neutral-detergent fibre and hemicellulose also. This lower rumen digestion was compensated by a higher proportion of digestion occurring in the hindgut for hemicellulose (P < 0.05 for AWSC, P > 0.05 for AWSP), but not for cellulose. Across all rations, rumen fluid volume increased with increasing cell-wall intake. The efficiencies of microbial protein synthesis were (average of three different methods of estimation) 23.3, 26.2, 34.8 and 31.7 g N/kg apparently-rumen-degraded organic matter for UWS, AWS, AWSC and AWSP respectively. The difference between UWS and AWS was not significant, but values for AWSC and AWSP were significantly higher than that for AWS. The rumen digestion of feed amino acid-N (AA-N) was significantly higher for AWSC than for the other rations. The apparent small-intestinal digestion of AA-N and N was significantly higher for AWSP than for the other rations. The true small-intestinal digestion values were 0.86, 0.84 and 0.68 for AA-N, N and non-protein-N respectively. Ileal endogenous losses of AA-N were approximately 6 mg/g duodenal non-protein dry-matter flow. Linear relationships were observed between DOMI and N balance and truly absorbed AA-N, indicating that DOMI could have been limited by small-intestinal amino acid availability. Regression of N balance v. truly absorbed AA-N resulted in an estimate of net efficiency of utilization of truly absorbed AA-N or 0.54.

Ammonia↗
PubMed2003

Wood digestion in Pselactus spadix Herbst--a weevil attacking marine timber structures.

Pselactus spadix tunnels timber structures in the marine environment. Recent studies reported a cosmopolitan distribution for this weevil, which is frequently found in harbour and port areas. P. spadix feeds on timber (hardwood and softwood) in immature and adult life stages, but its digestion of wood components had not been investigated. Using dry weight analyses of tunnel walls and frass produced, P. spadix adults consumed Scots pine with soft rot decay at a rate of 1.59 +/- 0.37 mg d-1 and the digestibility of this substrate was 57.96 +/- 5.89 (i.e. for 100 mg consumed SR-pine, 58 mg was digested). Using gravimetric analysis to quantify structural wood components in tunnel walls and frass, P. spadix adults were found to digest cellulose, lignin and hemicellulose with digestibility coefficients of 82.2, 41.2 and 14.5 respectively. Fourier Transform Infrared (FTIR) spectroscopy analyses of tunnel walls and frass of adults and larvae from soft rotted pine also indicated digestion of all structural components, with larvae digesting cellulose and lignin more efficiently than adults. When FTIR was employed to analyse adult tunnel walls and frass from undecayed pine, cellulose and hemicellulose were digested, but no evidence of lignin digestion was found. This study shows that adults digest lignin when soft rot is present and suggests a symbiotic function of wood degrading microorganisms.

Animals↗
PubMed1980

[The influence of various feedstuffs containing fat and protein on the digestibility of crude nutrients in young calves].

Digestibility trials were carried out with calves, aged 3, 5, 7, 9, and 11 weeks, which were fed with feedstuffs of various energy and protein levels (various amounts of dried skim milk supplement with 146, 219, 323 g per day of the milk replacer Laktin) plus concentrate and hay. The purpose of the experiment was to find out what effect the amount of milk replacer varying daily had on the digestibility of the nutrients. The experiments confirm that the amount of milk replacer has a great influence on the digestibility of the crude fat. The amount of digestible crude fat consumed with the feed considerably influcenced the digestibility of the energy, it had little influence on the digestibility of the other nutrients, however. With increasing age the calves received more plant protein sources with a lower biologic value. Thus the digestibility of the protein in the complete ration was diminished as well. This shows that the digestibility was influenced by the protein quality, not, however, by the amount of crude protein. The digestibility of the dry matter andthe organic matter as well as of the N-free extractives in the feed ration diminished according to the changed composition with the increasing age of the animals; in constrast to this the digestibility of the crude fibres increased gradually.

Age Factors↗
PubMed1993

Digestion characteristics by beef cattle consuming bermudagrass or bromegrass hay alone or with alfalfa and(or) corn.

Cannulated beef cattle (four cows: 556 kg initial weight; four steers: 504 kg initial weight) were used in an experiment with two simultaneous Latin squares to determine effects of substituting alfalfa and(or) corn for vegetative bermudagrass (BER; 77% neutral detergent fibre and 5.5% acid detergent lignin) or mature bromegrass (BRO; 70% neutral detergent fibre and 6.6% acid detergent lignin) hay on digestion characteristics. For Controls, BER or BRO was fed at 1.32 or 1.54% body weight of cows and steers, respectively; other treatments entailed substitution for hay DM of alfalfa cubes (17%) or ground corn (33%). A protein supplement was given to all animals. In vitro neutral detergent fibre (NDF) digestion was slightly greater for BER than BRO. Supplement treatments did not affect the concentration of total volatile fatty acids or the molar proportion of propionate in ruminal fluid. True ruminal organic matter (OM) digestion was similar among diets; greater duodenal microbial OM flow and postruminal NDF digestion for BRO than BER diets were responsible for higher (P < 0.05) postruminal OM digestion for BRO diets. Supplement treatment did not affect duodenal microbial nitrogen flow or efficiency of microbial growth. Corn supplementation increased total tract OM digestion (P < 0.05). Alfalfa addition depressed total tract OM and NDF digestibilities more when added to BER than BRO; depressions in total tract NDF digestion with alfalfa and corn substitutions were additive. With constant DM intake, slightly less than ad libitum, alfalfa or corn substituted alone or together for hay did not improve characteristics of digestion by cattle consuming vegetative bermudagrass or mature bromegrass other than increased postruminal and total tract OM digestibilities with corn.

Animal Feed↗
PubMed1996

Digestibilities of energy, protein, fat and nonstarch polysaccharides in a low fiber diet and diets containing coarse or fine whole meal rye are comparable in rats and humans.

The apparent digestibility of energy, protein, fat and nonstarch polysaccharides (NSP) of a low fiber diet and two high fiber diets containing coarse or fine whole meal rye bread was studied in experiments with humans and rats. Human subjects consumed the experimental diets for 3 wk each in a 3 x 3 cross over design. For the rat diets, duplicate portions of the foods consumed by the human subjects were mixed together, freeze dried and ground. There was a good agreement in the digestibility of energy (humans: 94.7 +/- 0.9, 91.2 +/- 1.2 and 91.6 +/- 1.4%; rats: 95.0 +/- 0.8, 92.5 +/- 1.4 and 91.7 +/- 1.8%) and fat (humans: 95.2 +/- 1.5, 94.4 +/- 1.0 and 94.8 +/- 2.5%, rats: 95.4 +/- 0.9, 94.0 +/- 0.4 and 94.0 +/- 0.4%) for the low fiber diet and the diets containing coarse or fine whole meal bread, respectively. Apparent and true digestibility of protein was consistently lower (P < 0.0001) in humans (apparent digestibility: 90.6 +/- 1.5, 86.2 +/- 1.4 and 86.3 +/- 2.3%; true digestibility: 95.1 +/- 1.5, 90.7 +/- 1.4 and 90.8 +/- 2.2%) than in rats (apparent digestibility: 92.3 +/- 1.1, 89.4 +/- 0.9 and 88.9 +/- 1.0%; true digestibility: 98.3 +/- 1.1, 94.9 +/- 0.9 and 94.2 +/- 1.0%) for all three diets. The digestibility of NSP tended to be lower (P < 0.066) in rats than in humans for the diet containing fine whole meal bread (rats: 59.6 +/- 8.0%, humans: 68.0 +/- 5.2%) and the low fiber diet (rats: 72.1 +/- 10.8%; humans: 80.5 +/- 7.1%), whereas it was similar in both species for the diet containing the coarse whole meal bread (rats: 66.1 +/- 6.0%; humans: 65.8 +/- 9.3%). In spite of some differences in digestibility values, our results suggest that the rat is a suitable model for humans to predict digestibility of nutrients in mixed diets containing cereal fiber sources.

Adult↗
PubMed1997

Plant limitations to fiber digestion and utilization.

Energy availability from forages is limited by fiber concentration because fiber is slowly and incompletely digested, whereas cell solubles are almost completely digested. Thus, the proportion of fiber to cell solubles is a major determinant of energy availability in forages. Grasses normally have more fiber than legumes, especially in leaves. Grass fiber is more digestible than that of legumes, but that of legumes digests at a faster rate. Ruminants digest 40-50% of legume fiber and 60-70% of grass fiber. Some fiber cannot be digested no matter how long it remains in the rumen. Lignin is thought to interfere with microbial degradation of fiber polysaccharides by acting as a physical barrier and by being cross-linked to polysaccharides by ferulate bridges. In addition to the effects of lignin, physical and structural barriers may limit fiber digestibility. Because the middle lamella and primary wall of thick-walled cells are so highly lignified, many cells can be digested only from the interior of the cell. For many cells, access to cell interiors is limited because of large particle sizes. Forage digestibility could be improved by reducing the amount of lignified cells or by developing improved cultivars so that lignified cells are more digestible.

Animal Feed↗
PubMed2000

Digestion of fat does not differ in growing pigs fed diets containing fish oil, rapeseed oil or coconut oil.

We studied the digestion of fat and fatty acids in diets containing oils with different fatty acid composition. Four barrows (initial weight 35 kg) were fitted with a simple T-cannula at the terminal ileum. Three wheat starch and fish meal-based diets were formulated to contain either 150 g fish oil, rapeseed oil or coconut oil/kg. A basal diet, which did not contain oil, was also prepared. The diets were fed according to a 4 x 4 Latin square design. Each experimental period comprised 5 d adaptation to the diets, 3 d fecal collection and 2 d digesta collection. The apparent ileal and fecal digestibilities of fat were relatively high (88 - 93%). The ileal digestibilities of total, saturated and monounsaturated fatty acids did not differ among the diets. However, the digestibilities of polyunsaturated fatty acids (PUFA) in the fish and rapeseed oil diets were higher (P < 0.05) than in the coconut oil diet. The ileal digestibilities of 18:1, 18:2 and 18:3 in the rapeseed oil diet ranged from 94 to 97%. The ileal digestion of the unsaturated long-chain fatty acids 20:5(n-3) and 22:6(n-3) in the fish oil diet was nearly complete (97 - 98%). Apparent fecal digestibilities of saturated fatty acids (76 - 89%) were lower than apparent ileal digestibilities (89 - 94%). The digestibilities of fat and fatty acids were relatively high when pigs were fed diets containing fish oil, rapeseed oil or coconut oil. There were few differences in the digestibilities of saturated, monounsaturated and PUFA in the fish oil, rapeseed oil or coconut oil diets.

Animals↗
PubMed1998

Effect of raw material source, processing systems, and processing temperatures on amino acid digestibility of meat and bone meals.

Experiments were conducted to evaluate amino acid digestibility of 32 commercial meat and bone meals (MBM) varying in raw material source and produced in seven different commercial cooking systems and at two processing temperatures (low vs high) that differed by 15 to 20 C. Raw material sources included all beef, all pork, mixed species, and high bone MBM. True digestibilities of amino acids were determined using the precision-fed cecectomized rooster assay. Protein efficiency ratio (PER) of six MBM varying greatly in amino acid digestibility was determined with chicks fed 10% CP diets containing a MBM as the sole source of dietary protein. The 32 MBM samples averaged 53.2% CP, 2.73% Lys, 0.6% Cys, and 0.75% Met on a DM basis. True digestibility averaged 82% for Lys, 87% for Met, and 47% for Cys. True digestibilities of amino acids varied substantially among processing systems and temperatures, particularly for Lys and Cys. For example, Lys and Cys digestibility ranged from 68 to 92% and from 20 to 71%, respectively, among different MBM. The higher processing temperature generally yielded lower amino acid digestibility than did the low processing temperature. A smaller, less consistent, effect was observed for raw material source. The PER values of the six selected MBM varied from 0.97 to 2.68 and were highly correlated with amino acid digestibility. These results indicated that very high amino acid digestibility MBM can be produced in commercial rendering systems. However, differences in processing systems and temperatures can cause substantial variability in amino acid digestibilities.

Amino Acids↗
PubMed1998

Bioavailability of the digestible lysine and total sulfur amino acids in meat and bone meals varying in protein quality.

Experiments were conducted to determine whether the digestible Lys, Met, and TSAA in a high and low quality meat and bone meal (MBM) were totally bioavailable for protein synthesis in chicks. True digestibility of amino acids (AA) in the two MBM was determined by the precision-fed cecectomized rooster assay. Bioavailability of the digestible AA was then assessed in three slope-ratio chick growth assays using Lys-, Met-, or TSAA-deficient crystalline AA basal diets that were supplemented with varying levels of the test AA, high or low quality MBM, or AA mixtures simulating the mean digestible AA composition of the high and low quality MBM. Response parameters were weight gain, feed efficiency, body N gain, and body Lys gain in the Lys assay and weight gain and feed efficiency in the Met and TSAA assays. Bioavailability values for the digestible Lys, Met, and TSAA in the MBM and AA mixtures simulating MBM varied depending on response parameter, with values based on feed efficiency generally being highest. No consistent differences in bioavailability of the digestible AA were observed between the two MBM when all AA were considered; however, the bioavailability of the digestible Lys in the low quality MBM was lower than that in the high quality MBM for two of four performance criteria. When considering all response parameters and the AA mixture results, bioavailability of the digestible Lys and Met in the two MBM was generally 90% or greater, whereas bioavailability of the digestible TSAA was only 80% or less. The results of this study indicated that essentially all of the digestible Lys and Met in MBM were bioavailable for protein synthesis and metabolism but suggested that a significant amount of the TSAA, particularly Cys, was not bioavailable.

Amino Acids, Sulfur↗
PubMed1998

Effect of acute heat stress on amino acid digestibility in laying hens.

An experiment was conducted to determine the effect of acute heat stress exposure on amino acid digestibility in laying hens. A total of 30 commercial laying hens were singly housed in an environmentally controlled facility, fed a standard laying ration, and exposed to a constant thermoneutral temperature (21 C) for 12 d. The hens were then randomly fed one of three diets (10 hens per diet) and exposed to three consecutive temperature periods (8 d each), which consisted of: 1) a constant 21 C temperature, 2) a cycling temperature of 35 C for 12 h and 29 C for 12 h, and 3) a constant 21 C temperature. The three isonitrogenous (18% CP) diets fed were: 1) a corn-soybean meal diet, 2) a corn-soybean meal diet containing 15% meat and bone meal, and 3) a corn-soybean meal diet containing 5% alfalfa meal and 20% wheat bran. Excreta were collected from all hens during the last 4 d of each temperature period and apparent amino acid digestibility was determined. There was a significant diet effect (P < 0.05) on amino acid digestibility. Digestibility of amino acids in Diet 2 (corn-soybean meal/meat and bone meal) was higher (P < 0.05) than in the other two diets. In addition, digestibility of amino acids in Diet 3 (corn-soybean meal/alfalfa meal/wheat bran) was significantly lower (P < 0.05) than in Diets 1 or 2. Heat stress generally had no significant effect on amino acid digestibility except for His and Lys digestibility. Histidine digestibility was higher during the heat stress period than during the initial and recovery thermoneutral periods, whereas Lys digestibility was higher during the heat stress period than during the initial thermoneutral period. These results indicated that acute heat stress (8 d) had no adverse effects on dietary amino acid digestibility in laying hens.

Amino Acids↗
PubMed1999

Effects of feeding high carbohydrate or fat diets. 2. Apparent digestibility and apparent metabolizable energy of the posthatch poult.

An experiment was conducted with turkey poults to determine the apparent digestibility and derivation of ME from diets containing a high proportion of carbohydrate from corn (CHO; 60% of diet) or 10%) supplemental fat from an animal-vegetable blended fat (FAT) or a synthetic medium-chain triglyceride (MCT). Poults fed the FAT diet consumed more feed from 6 to 8 and 9 to 11 d of age than poults fed the CHO diet, intake of the MCT diet was intermediate. From 3 to 11 d of age, the percentage apparent digestibility of nonlipid DM by poults fed the CHO diet was greater than that observed for either the FAT or MCT diets (P < or = 0.05). The percentage apparent digestibility of lipid was consistently greater for poults fed the MCT diet (> or = 90%) and could be attributed to the high apparent digestibility of C8:0 (>95%), which accounted for 76% of total MCT dietary fatty acids. Over the course of the experiment, the mean percentage apparent digestibility of lipid in the CHO and FAT diets was 76.4 and 70.8%, respectively, and did not change with increasing age. The lower percentage apparent digestibility of lipid in the CHO and FAT diets was attributed to the low apparent digestibility of C16:0 (70.4, 52.7%) and C18:0 (58.4, 26.8%), respectively. The apparent digestibility of the polyunsaturated fatty acids, C18:2 (n-6) and C18:3 (n-3), was consistently high and ranged from 72 to 85% and 81 to 88%, respectively. The CHO diet resulted in an approximate 6% increase in determined AMEn compared with either the FAT or MCT diets. The results of this study showed that commercial feed-grade fats are poorly digested by very young poults. The digestibility of polyunsaturated fatty acids, however, was shown to be quite high, and the data suggest that vegetable oils containing high proportions of polyunsaturated fatty acids or alternative fat sources containing high proportions of medium-chain fatty acids could be well utilized by the very young poult.

Aging↗
PubMed1999

Influence of microbial phytase on apparent ileal amino acid digestibility of feedstuffs for broilers.

The influence of microbial phytase on the ileal amino acid digestibilities in three cereals (corn, sorghum, and wheat), four oilseed meals (soybean meal, canola meal, cottonseed meal, and sunflower meal) and two cereal by-products (wheat middlings and rice polishings) was determined using 5-wk-old broilers. Supplementation of microbial phytase (1,200 FTU/kg) improved (P < 0.001 to 0.10) the digestibilities of protein and amino acids in all feedstuffs, but the magnitude of response varied depending on the feedstuff and the amino acid considered. Mean digestibility of the 15 amino acids in the feedstuffs without and with phytase were: corn, 78.0 and 80.4%; sorghum, 74.7 and 79.4%; wheat, 77.7 and 84.6%; soybean meal, 82.2 and 85.5%; canola meal, 78.7 and 80.7%; cottonseed meal, 70.8 and 74.2%; sunflower meal, 76.7 and 80.2%; wheat middlings, 70.8 and 73.4%; and rice polishings 62.1 and 66.9%, respectively. When individual amino acids were considered, the increments in digestibility were relatively higher for threonine and valine. This effect was consistent across all feedstuffs. The observed variations in response among feedstuffs were influenced by the inherent protein digestibility, but not by dietary phytic acid concentration. No correlations were determined between the dietary concentrations of phytic acid and phytase responses in terms of protein digestibility (r = 0.20; P > 0.31) and mean amino acid digestibility (r = 0.12; P > 0.51); however a significant negative correlation was observed between inherent protein digestibility and phytase responses in protein digestibility (r = -0.42; P < 0.03). It appears that solubilities of phytate salts and protein, and their influence on the degree of phytate-protein complexing in different feedstuffs, may be more relevant than total phytic acid concentrations. Interestingly, dietary phytic acid concentrations were negatively correlated with inherent protein (r = -0.81; P < 0.001) and mean amino acid (r = -0.85; P < 0.001) digestibilities of the feedstuffs evaluated in this study.

6-Phytase↗
PubMed2002

Effects of age on nutrient digestibility in chicks fed different diets.

Three experiments were conducted to determine the effects of age on apparent MEn and apparent amino acid (AA) digestibility of various diets for New Hampshire x Columbian (Experiments 1 and 2) and commercial broiler (Experiment 3) male chicks. Excreta were collected at 0 to 2, 3 to 4, 7, 14, and 21 d of age in all experiments, and nutrient digestibility was determined using acid-insoluble ash as a marker. The first experiment evaluated a corn-soybean meal (SBM) diet. Both MEn and digestibility of AA increased with age, and broken-line regression analysis predicted a plateau at 14 d for MEn and 10 d of age for AA digestibility. For example, MEn increased from 2,970 to 3,430 kcal/kg DM, and lysine digestibility increased from 78 to 89% between 0 and 14 d of age. The second experiment evaluated cornstarch-crystalline AA, dextrose-casein, corn-SBM, and corn-canola meal diets. The MEn of the corn-SBM, corn-canola meal, and cornstarch-crystalline AA diets increased from 0 to 14 d of age. In contrast, the MEn of the dextrose-casein diet was high (3,800 kcal/kg DM) immediately after hatching and did not increase substantially with increasing age. Digestibility of AA increased with age for the corn-SBM and corn-canola meal diets, and broken-line regression analysis again predicted a plateau at approximately 10 d of age. Conversely, AA digestibility of the dextrose-casein and cornstarch-crystalline AA diets was high immediately after hatching (93 to 96%) and increased only slightly with age. The results of Experiment 3 with commercial broiler chicks also showed significant (P < 0.05) increases in MEn and AA digestibility with increasing age. The results of this study indicated that the MEn and AA digestibility of corn-SBM and corn-canola meal diets increase with age for young chicks. The results also showed that MEn and AA digestibility were very high for a dextrose-casein diet immediately after hatching. Thus, the latter ingredients may have beneficial effects for very young chicks.

Aging↗