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PubMed1989

Ultrastructure of the midgut and blood meal digestion in the adult tick Dermacentor variabilis.

Digestive cells in the midgut of male and female Dermacentor variabilis (Say) took up the blood meal in coated vesicles and smooth flask-shaped vesicles, and deposited it in endosomes which were digested via heterophagy. Iron was concentrated in residual bodies. Digestion occurred in three distinct phases in mated females: (1) continuous digestion (initiated by feeding) occurred during slow engorgement; (2) reduced digestion (initiated by mating) occurred in mated females during the period of rapid engorgement; (3) a second continuous digestion phase (initiated by detachment from the host) occurred throughout the post-feeding periods of preoviposition and oviposition. It proposed that the stem cells in the midguts of unfed females were progenitor of digestive, replacement, and presumed vitellogenic cells in midguts of mated feeding females. Digestive cells were present in all three digestion phases. Only during the first continuous digestion phase did digestive cells fill up with residual bodies, rupture and slough into the lumen, or did whole cells slough into the lumen. During the other two digestion phases no sloughing of digestive cells was observed. At the end of oviposition the digestive cells were filled with residual bodies. Replacement cells were present only during the first continuous-digestion phase. Presumed vitellogenic cells were present only during the reduced-digestion phase and during the second continuous-digestion phase. Stem cells in unfed males developed only into digestive cells in feeding males. Fed males and fed unmated females had only the first continuous-digestion phase. After being hand-detached from the host, unmated 13-day-fed females went through cellular changes associated with the reduced-digestion phase and second continuous-digestion phase of fed mated females, then began ovipositing. Maximum development of the basal labyrinth system and lateral spaces matched the known time of maximum water and ion movement across the midgut epithelia. Spectrophotometric analyses of lumen contents and midgut cells, sampled after detachment from the host, showed that concentrations of protein and hemoglobin at day 1 post-detachment decreased by one-half at the beginning of oviposition, while hematin increased about twofold by the end of oviposition. This supported the idea of the presence of a second continuous-digestion phase.

Animals↗
PubMed1994

The effect of heat on amino acids for growing pigs. 1. A comparison of ileal and faecal digestibilities of amino acids in raw and heat-treated field peas (Pisum sativum cultivar Dundale).

Three experiments were conducted to examine the effect of heating field peas (Pisum sativum cultivar Dundale) on (1) proximate analysis and total amino acid composition, (2) ileal and faecal digestibilities of amino acids, and (3) digestible energy content. Alternative techniques for assessing ileal and faecal digestibilities and digestible energy respectively, were also investigated. Forced-air dehydrators were used to heat field peas at temperatures of 110 degrees, 135 degrees, 150 degrees or 165 degrees. In the first experiment the apparent ileal and faecal digestibilities of amino acids and the faecal digestibility of energy in the raw and heated field peas were determined using pigs fitted with 'T'-shaped cannulas. In the second, apparent ileal digestibility of amino acids and the faecal digestibility of energy were determined using the direct ileal and rectal sampling technique. This involved a single collection of digesta and faeces from the digestive tract of the pig while it was anaesthetized. The faecal digestibilities of amino acids and energy were determined using total faeces collection in the third experiment. In all experiments the respective field-pea treatments comprised 400 g/kg sugar-based diets and were the only source of amino acids. Heat significantly decreased the lysine (14.6-8.7 g/kg; P < 0.001), cystine (3.2-2.6 g/kg; P < 0.01) and arginine (16.7-14.5 g/kg; P < 0.05) contents of the heated peas. The 'reactive' lysine content of the field peas, as measured using the Silcock technique, was decreased by 0.11 and 0.30 with the application of heat at 150 degrees and 165 degrees respectively. Heat treatments did not alter the ileal digestibility of most amino acids. Only aspartic acid (0.72-0.58), glutamic acid (0.80-0.65) and the basic amino acids, lysine (0.79-0.56) and arginine (0.85-0.75), showed a significant linear decrease (P < 0.05) in ileal digestibility over the heat treatments, determined using the ileal cannulation procedure. Heating significantly (P < 0.05) decreased faecal digestibility for all amino acids. Faecal digestibility was consistently greater than ileal digestibility for the raw field peas; however, this difference decreased with heat application until faecal digestibility was equal or less than ileal digestibility at the 165 degrees treatment. Heat linearly depressed digestible energy, diet dry-matter digestibility and diet energy digestibility. Losses in lysine, cystine and arginine are likely to be due to early and advanced Maillard reactions. Considerable binding of the remaining lysine also occurred as indicated by a decline in Silcock-reactive lysine.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗
PubMed2005

Ileal and total tract nutrient digestibility in blue foxes (Alopex lagopus) fed extruded diets containing different protein sources.

This study compared apparent ileal and total tract digestibility of macronutrients and amino acids in blue foxes (Alopex lagopus) fed dry extruded diets. The control diet contained fish meal as the main protein source, while in the other diets 50% of the fish meal protein was replaced by not de-hulled solvent-extracted soybean meal, meat meal or bacterial protein meal. Ileal digestibility was obtained with animals modified with ileorectal anastomosis (IRA method). There were no significant differences in the average digestibility of CP, Lys, Trp, Val, Ala or Glu between IRA modified and intact animals. Average ileal digestibilities of His, Thr, Asp, Cys, Gly, Hyp, Pro, Ser, starch and total carbohydrates (CHO) were significantly lower compared with total tract values. Average ileal digestibility of Arg, Ile, Leu, Met, Phe, Tyr and crude fat was significantly higher than total tract digestibility. Digestibility measured in IRA modified animals showed less variability compared with values from intact animals. There were significant differences among diets in ileal as well as total tract digestibility of orude protein, most amino acids, starch and CHO, and in ileal digestibility of crude fat. Ileal crude protein digestibility of the diets ranged from 81.0-86.4% and total tract digestibility from 82.5-86.4%. Ileal amino acid digestibilities ranged from 70.1 (Asp) to 93.3% (Arg) and total tract values ranged from 72.8 (Cys) to 92.2% (Arg). Both ileal and total tract digestibilities of crude protein and most amino acids were significantly lower for diets containing meat meal or bacterial protein meal compared with the control fish meal-based diet and the diet with soybean meal. Although ileal digestibility may be more accurate than total tract digestibility in estimating the protein and amino acid supply in blue foxes, total tract digestibility may be acceptable because of numerically small differences between ileal and total tract digestibilities for protein and most amino acids. It was further concluded that ileal digestibilities of starch and CHO in the blue fox are lower than corresponding total tract digestibilities.

Amino Acids↗
PubMed1977

Dietary fiber components: relationship to the rate and extent of ruminal digestion.

A mathematical model can serve as a useful reference for describing the mechanisms involved in digestion and for discussing the factors that influence the rate and extent of ruminal digestion. Ruminal digestion can be divided into four components: digestion rate, digestion lag, potential extent of digestion, and passage rate. Each component affects the apparent extent of digestion in a distinct manner and is influenced by separate factors. Digestion rate is directly related to apparent extent of digestion. It is not influenced by chemical entities presently being measured, but may be related to the morphological, crystalline, or physical nature of fiber. It may also be influenced by factors that inhibit or stimulate ruman microbial growth and their fiber-degrading enzymes. Digestion lag is inversely related to apparent extent of digestion; however, factors influencing it are poorly defined. The may include factors affecting microbial populations and their attachment to fiber prior to digestion; or the digestion lag may be related to the chemical or physical alteration of fiber that must occur before digestion can begin. The potential extent of digestion is directly related to apparent extent of digestion and is influenced by plant fiber composition, primarily. Lignin, and possibly silica, functions to limit the potential extent of digestion. Rate of passage essentially competes with rate of digestion for fiber particles as they pass through the rumen; therefore it is inversely related to the apparent extent of digestion. Passage rate is associated with feed intake level and particle size, although other factors such as type of diet and animal physiology may be important.

Animals↗
PubMed2001

Starch digestion rate in the small intestine of broiler chickens differs among feedstuffs.

Dietary starch is the major energy source for broiler chickens, and knowledge about its digestive behavior can be important. In a digestibility trial with 720 broiler chickens, site, rate and extent of starch digestion were measured for 12 feedstuffs. Starch digestion was determined using the slaughter technique, which involves removal of the small intestine from the recently killed chicken, with manual collection of the contents. Starch digestion coefficients were calculated from remaining starch in three segments of the small intestine and in excreta. Mean retention time in four segments of the small intestine was measured. This enabled calculations for starch digestion rate (k(d)). Ileal starch digestibility varied from 33% (potato starch) to 99% (tapioca). Retention time for digesta in the postduodenal small intestine varied from 136 min (barley diet) to 182 min (potato diet). On the basis of starch digestion rates, a distinction was made between slowly digestible starch (k(d) < 1 h(-1)), gradually digestible starch (k(d):1-2 h(-1)) and rapidly digestible starch (k(d) > 2 h(-1)). Starch from common beans was digested most slowly (k(d): 0.5 h(-1)), and starch from tapioca was digested most rapidly (k(d): 4.3 h(-1)). Starch digestion rates of potato starch and legume seeds were lower than those of cereal grains and tapioca. Degradation of starch entering the hind gut of the birds did not occur. Milling of corn affected rate, but not the extent of starch digestion. We concluded that site of starch digestion within the small intestine is not an accurate indicator for starch digestion rate.

Absorption↗
PubMed2006

Impact of corn vitreousness and processing on site and extent of digestion by feedlot cattle.

Eight cannulated Holstein steers (average BW: 251 kg) were used in 2 simultaneous 4 x 4 Latin squares in a split-plot arrangement to test the effects of processing method [dry-rolled (DR) vs. steam-flaked (SF); main plot] and vitreousness (V, %; subplot) of yellow dent corn (V55, V61, V63, and V65) on site of digestion of diets containing 73.2% corn grain. No vitreousness x processing method interactions were detected for ruminal digestion, but ruminal starch digestion was 14.4% lower (P < 0.01) for DR than for SF corn. Interactions were detected between vitreousness and processing method for postruminal (P < 0.10) and total tract digestion (P < 0.05). With DR, vitreousness tended to decrease (linear effect, P < 0.10) postruminal OM and starch digestion. With SF, vitreousness did not affect (P > or = 0.15) postruminal digestion of OM and starch. Postruminal N digestion tended to decrease (linear effect, P = 0.12) as vitreousness increased. Postruminal digestion was greater for SF than for DR corn OM (25.7%, P < 0.05), starch (94.3%, P < 0.10), and N (10.7%, P < 0.01). Steam flaking increased total tract digestion of OM (11%, P < 0.05), starch (16%, P < 0.01), and N (8.4%, P < 0.05) but decreased total tract ADF digestion (26.7%, P < 0.01). With DR, total tract starch digestion was lower for V65 (cubic effect, P < 0.10) than for the other hybrids. With SF, total tract starch digestion was not affected (P > or = 0.15) by vitreousness. Fecal starch and total tract starch digestion were inversely related (starch digestion, % = 101 - 0.65 x fecal starch, %; r2 = 0.94, P < 0.01). Ruminal pH was greater for steers fed DR than for steers fed SF corn (6.03 vs. 5.62, P < 0.05). Steam flaking decreased (P < 0.01) the ruminal molar proportion of acetate (24%), acetate:propionate molar ratio (55%), estimated methane production (37.5%), and butyrate (11.3%, P < 0.05). There was a vitreousness x processing interaction (P < 0.01) for acetate:propionate. For DR, acetate:propionate tended to increase (linear effect; P < 0.10) with increasing vitreousness. With SF, acetate:propionate was greater (cubic effect, P < 0.01) for V65. Starch from more vitreous corn grain was less digested when corn grain was DR, but this adverse effect of vitreousness on digestion was negated when the corn grain was SF. Of the 19% advantage in energetic efficiency associated with flaked over rolled corn grain, about 3/4 can be attributed to increased OM digestibility, with the remaining 1/4 ascribed to reduced methane loss.

Animal Feed↗
PubMed1998

Suppressive effect of globin digest on postprandial hyperlipidemia in male volunteers.

We have reported previously that various edible protein digests inhibit dietary hyperlipidemia in mice, rats, pigs and dogs. Of the various digests tested, globin digest had the most potent inhibitory activity, and a tetrapeptide extracted from globin digest, Val-Val-Tyr-Pro, had activity 7000-fold greater than that of the parent digest. In this clinical study, we investigated the influence of globin digest on serum chylomicron triglyceride concentrations as an indicator of the effect of globin digest on fat absorption and catabolism in humans. Parallel and crossover trials were conducted in which men consumed a control high fat diet (25 g fat, 7.6 g carbohydrate, 1.9 g protein and 0.7 g sodium chloride) or the same diet supplemented with globin digest. The supplemented dosages were 1 and 4 g globin digest. In the parallel trial, 22 men were divided into three groups: control, globin digest 1 g and globin digest 4 g. The increases in chylomicron triglyceride concentrations at 1 h after ingestion of 1 or 4 g globin digest were significantly lower (P < 0.05) compared with the control group. The crossover trial involved six subjects who consumed the control high fat diet and the same diet supplemented with 4 g globin digest. Serum chylomicron triglyceride levels increased in both groups at 1 and 2 h after ingestion, but when subjects consumed 4 g globin digest the increases were suppressed to 75 (P < 0.05) and 42% (P < 0.05) of the increases in controls at the corresponding times, respectively. The areas under the curves of chylomicron and serum total triglyceride concentrations during the 4 h after ingestion of 4 g globin digest were 46 (P < 0.05) and 34% (P < 0.05) lower, respectively, than when the men consumed the high fat control diet. In these trials, globin digest reduced the increase in serum chylomicron triglyceride concentrations as a result of the ingestion of a high fat diet. This hypotriglyceridemic effect of globin digest may be valuable for preventing obesity and in lowering the incidence of cardiovascular diseases.

Adult↗
PubMedDate not supplied

Aerobic sludge digestion under low dissolved oxygen concentrations.

Low dissolved oxygen (DO) concentrations occur commonly in aerobic digesters treating thickened sludge, with benefits of smaller digester size, much reduced aeration cost, and higher digestion temperature (especially important for plants in colder areas). The effects of low DO concentrations on digestion kinetics were studied using the sludge from municipal wastewater treatment plants in Akron, Ohio, and Los Lunas, New Mexico. The experiments were conducted in both batch digestion and a mixed mode of continuous, fed-batch, and batch operations. The low DO condition was clearly advantageous in eliminating the need for pH control because of the simultaneous occurrence of nitrification and denitrification. However, when compared with fully aerobic (high DO) systems under constant pH control (rare in full-scale plants), low DO concentrations and a higher solids loading had a negative effect on the specific volatile solids (VS) digestion kinetics. Nonetheless, the overall (volumetric) digestion performance depends not only on the specific digestion kinetics, but also the solids concentration, pH, and digester temperature. All of the latter factors favor the low DO digestion of thickened sludge. The significant effect of temperature on low DO digestion was confirmed in the mixed-mode study with the Akron sludge. When compared with the well-known empirical correlation between VS reduction and the product (temperature x solids retention time), the experimental data followed the same trend, but were lower than the correlation predictions. The latter was attributed to the lower digestible VS in the Akron sludge, the slower digestion at low DO concentrations, or both. Through model simulation, the first-order decay constant (kd) was estimated as 0.004 h(-1) in the mixed-mode operations, much lower than those (0.011 to 0.029 h(-1)) obtained in batch digestion. The findings suggested that the interactions among sludges with different treatment ages may have a substantially negative effect on digestion kinetics. The use of multistage digesters, especially with small front-end reactors, may be advantageous in both "process" kinetics and "biological reaction" kinetics for sludge digestion.

Bacteria, Aerobic↗
PubMed1989

Apparent digestibility of nitrogen and amino acids in protein feedstuffs by growing pigs.

Eight digestion trials were conducted with pigs fitted with ileal T-cannulas to determine the apparent digestibilities of N and amino acids in common protein feedstuffs. Trial-to-trial variation was minimal as determined by the variation in digestibilities for soybean meal, which was evaluated in each trial. Apparent digestibilities varied widely; ileal N digestibility ranged from 88 to 63%, and ileal lysine digestibility ranged from 93 to 40%. In general, ring-dried blood meal, corn gluten meal, Menhaden fish meal, poultry-by-product meal and extruded whole soybeans were the most digestible, followed by canola meal, sunflower meal, peanut meal and meat and bone meal. Cottonseed meal and feather meal were the least digestible. Mean values for each feedstuff agree well with published data. Variation in digestibilities among samples of the same feedstuff was greater for the meat and bone meals. Regression of ileal essential amino acid digestibilities on ileal and fecal N digestibility indicated that amino acid digestibilities can be predicted more precisely from ileal N digestibility than from fecal N digestibility. However, neither ileal nor fecal N digestibility could be used with a high degree of certainty to predict ileal amino acid digestibilities.

Amino Acids↗