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The impact of exercise and swimming on the gastrointestinal blood flow and postprandial metabolism in the sea bass, Dicentrarchus labrax is discussed. The analysis proves that swimming, hypoxia and general stress leads to a considerable decrease in the gastrointestinal blood flow, while maintaining the specific dynamic action (SDA) of the food.

The overall objective of the studies reported here was to evaluate the growth and nutrient utilization responses of pigs to dietary supplementation of phytate- or nonstarch polysaccharide-degrading enzymes. In Exp. 1, growth performance and nutrient digestibility responses of forty-eight 10-kg pigs to dietary supplementation of phytase or a cocktail of xylanase, amylase, and protease (XAP) alone or in combination were evaluated. The growth response of one hundred fifty 23-kg pigs to dietary supplementation of phytase or xylanase individually or in combination was studied in Exp. 2 in a 6-wk growth trial, whereas Exp. 3 investigated the nutrient digestibility and nutrient retention responses of thirty 24-kg pigs to dietary supplementation of the same enzymes used in Exp. 2. In Exp. 1, the pigs were used in a 28-d feeding trial. They were blocked by BW and sex and allocated to 6 dietary treatments. The treatments were a positive control (PC) diet; a negative control (NC) diet marginally deficient in P and DE; NC with phytase added at 500 or 1,000 phytase units (FTU)/kg; NC with xylanase at 2,500 units (U)/kg, amylase at 400 U/kg, and protease at 4,000 U/kg; and NC with a combination of phytase added at 500 FTU/kg and XAP as above. In Exp. 2 and 3, the 5 dietary treatments were positive control (PC), negative control (NC), NC plus 500 FTU of phytase/kg, NC plus 4,000 U of xylanase/kg, and NC plus phytase and xylanase. In Exp. 1, low levels of nonphytate P and DE in the NC diet depressed (P < 0.05) ADG of the pigs by 16%, but phytase linearly increased (P < 0.05) ADG by up to 24% compared with NC. The cocktail of XAP alone had no effect on ADG of pigs, but the combination of XAP and phytase increased (P < 0.05) ADG by 17% compared with the NC treatment. There was a linear increase (P < 0.01) in Ca and P digestibility in response to phytase. In Exp. 2, ADG was 7% greater in PC than NC (P < 0.05); there were no effects of enzyme addition on any response. In Exp. 3, addition of phytase alone or in combination with xylanase improved (P < 0.05) P digestibility. Phosphorus excretion was greatest (P < 0.01) in the PC and lowest (P < 0.05) in the diet with the combination of phytase and xylanase. The combination of phytase and xylanase improved P retention (P < 0.01) above the NC diet to a level similar to the PC diet. In conclusion, a combination of phytase and carbohydrases improved ADG in 10-kg but not 23-kg pigs, but was efficient in improving P digestibility in pigs of all ages. Key words: carbohydrase, digestibility, growth, phytase, pig, retention

Study of epithelial-mesenchymal interactions, based on development of proventricular gland in digestive tract of stomach, is presented.

Two experiments were conducted using 2 ruminally and duodenally fistulated steers to determine the digestibility of undegradable intake protein (UIP) of smooth bromegrass (Bromis inermis), birdsfoot trefoil (Lotus coniculatus L.), and heat-treated alfalfa (Medicago sativa) using the mobile nylon bag technique. Undegradable intake protein was determined using neutral detergent insoluble CP at a single in situ incubation time point based on 75% of the total mean retention time estimated from IVDMD plus a 10-h passage lag. In Exp. 1, UIP (% DM) of smooth bromegrass in June and July were 1.82 and 1.71, respectively (P = 0.11). Undegradable intake protein (% DM) of birdsfoot trefoil increased from 1.30 in June to 1.94 in July (P < 0.01). Total tract indigestible protein of smooth bromegrass and birdsfoot trefoil increased in July (P < 0.05). Digestibility of UIP decreased in July for smooth bromegrass (P < 0.01) but tended to increase for birdsfoot trefoil (P = 0.07). In Exp. 2, alfalfa from plots fertilized with low (66 kg of N/ha) or high (200 kg of N/ha) amounts of N were dried to simulate 3 preservation methods: dehydrated (100[degrees]C, 10 h), sun-cured (50[degrees]C, 15 h), and lyophilized (-50[degrees]C, 72 h) alfalfa. Undegradable intake protein (% DM) was estimated as in Exp. 1 and was 3.13, 2.10, and 1.84 for dehydrated, sun-cured, and lyophilized alfalfa, respectively. Total tract indigestible protein (% DM) was increased (P < 0.05) for dehydrated alfalfa (1.66) compared with sun-cured (1.54) or lyophilized (1.57) alfalfa. As a result of greater UIP flow to the lower tract, digestibility (%) of UIP was greater (P < 0.01) for dehydrated (46.4) than for sun-cured (25.6) or lyophilized (14.7) alfalfa. Heat-treated alfalfa samples increased net UIP absorption in the lower tract because 1.47, 0.56, and 0.27 percentage units of UIP (% DM) of dehydrated, sun-cured, and lyophilized alfalfa, respectively, disappeared. Overall, the digestibility of the UIP of these forages was low in the lower tract. Key words: forage, heat-treated alfalfa, mobile nylon bag, undegradable intake protein digestibility

Soy proteins have been shown to result in lower postprandial nitrogen retention than milk proteins, but the mechanisms underlying these differences have not been elucidated. To investigate this question, we measured the postprandial kinetics of the appearance of individual [sup.15]N-amino acids in the serum of healthy adults after the ingestion of either [sup.15]N-soy (n = 8) or [sup.15]N-milk proteins (n = 8) in a mixed single meal (46 kJ/kg). The kinetics of total and dietary amino acids (AA) in the peripheral circulation were characterized by an earlier and higher peak after soy protein ingestion. Dietary AA levels peaked at 2.5 h in the soy group vs. 3.9 h in the milk group (P < 0.02). This time interval difference between groups was associated with a faster transfer of dietary N into urea in the soy group (peak at 3 vs. 4.75 h in the milk group, P < 0.005) and a higher level of incorporation into the serum protein pool from 3 to 8 h after the soy meal. The dietary AA pattern in the peripheral blood closely reflected the dietary protein AA pattern. Postprandial glucose, insulin, and glucagon levels and profiles did not differ between groups. Soy AA were digested more rapidly and were directed toward both deamination pathways and liver protein synthesis more than milk AA. We conclude that differences in the metabolic postprandial fates of soy and milk proteins are due mainly to differences in digestion kinetics; however, the AA composition of dietary proteins may also play a role. KEY WORDS: * dietary protein * amino acids * postprandial metabolism * GC-C-IRMS * humans

Research has been conducted on the isopod species found in the intertidal and supratidal zones of the North American Pacific coast. The symbiotic microbiota found on the midgut glands of these isopods has been investigated and the results are discussed.

Twelve ruminally cannulated steers (Angus x Holstein; average initial BW = 533 +/- 3.28 kg) were randomly allotted to one of three treatments (four steers/treatment) to evaluate the use of pretanned leather shavings as a component of a protein supplement for steers grazing dormant intermediate wheatgrass (Thinopyrum intermedium Host). Steers were allotted to one of three treatments: 1) no supplement (control); 2) supplementation intraruminally at 0700 with soybean meal at .2% of BW (as-fed basis); 3) supplementation intraruminal]y with soybean meal and pretanned leather shavings (17:8 ratio, respectively) at .16% of BW (as-fed basis). Supplements were formulated so that intakes were isonitrogenous and were placed intraruminally once daily (0700). Sampling periods were conducted February 3 to 16 and February 17 to March 5, 1995. In situ organic matter disappearance of the soybean meal supplement was greater (P > .05) than that of the leather shavings supplement at all incubation times (1, 3, 6, 9, 12, 24, and 48 h). Data suggested that pretanned leather shavings within the leather shavings supplement were only 25% degradable within the rumen. Forage OM intake (control = 12.7, soybean meal = 12.7, and leather shavings = 13.4 g/kg of BW), grazing time, and grazing efficiency were not altered (P > .10) by supplementation or type of supplement provided but did increase between the February and March samplings. Total intake was increased (P = .09) with supplementation and reflected the addition of the protein supplements. Particulate and fluid passage estimates were unaffected (P > .10) by the supplements; however, gastrointestinal fill increased (P = .01) between the February and March samplings. Ruminal pH was lower (P = .04) and ruminal NH3 N concentration was greater (P = .02) for supplemented steers than for control steers, and supplementation treatments did not differ (P > .10). Total VFA concentrations were increased (P = .01) by supplementation but were not affected by type of supplement provided (P > .10). Ruminal molar proportions of acetate and propionate and the ratio of these two VFA did not differ (P > .10) between supplementation types. Nonetheless, supplementation increased molar proportions of butyrate (P = .04), valerate (P = .02), and isovalerate (P = .05), and leather shavings supplementation increased (P = .10) isobutyrate proportions over those in steers supplemented with soybean meal. Combining pretanned leather shavings with soybean meal seemed to have no deleterious effects on forage intake, digesta passage, grazing behavior, or ruminal fermentation and seemed to provide effects similar to those of soybean meal alone. Key Words: Cattle, Digestion, Protein Supplements

Two digestion studies were conducted to evaluate the use of pretanned leather shavings as a component of a protein supplement. In Exp. 1, the in situ and in vitro disappearance of pretanned leather shavings and soybean meal was evaluated. Results revealed that less than 18.4% of the pretanned leather shavings was solubilized and disappeared when exposed to McDougall's buffer for 48 h, but there was 90.0% disappearance with 48-h exposure to a .1 N HC1/ pepsin treatment and 97.0% disappearance with exposure to a two-stage digestion. In situ disappearance following 72 h in the rumen allowed 6.8% disappearance. Thus, leather shavings seem to be relatively indigestible in the rumen, but postruminal digestion may be possible. In Exp. 2, six Angus x Holstein steers, fitted with ruminal and duodenal cannulas, were used in a replicated 3 x 3 Latin square to evaluate ruminal and digestion effects of the following supplements combined with fescue hay at 1.7% of BW (DM basis): no supplementation (control); supplementation intraruminally with soybean meal at .07% of BW (as-fed basis); and supplementation intraruminally with a combination of soybean meal and pretanned leather shavings (17:8 ratio) at .05% of BW (isonitrogenous to soybean meal; as fed basis). Ruminal fluid passage rate was greater and fluid turnover time was shorter in steers fed leather shavings than in those fed soybean meal (P =. 10). Ruminal pH was lower (P = .04) for supplemented steers than for control steers and ruminal NH(sub 3) N concentration was greater (P = .01) in steers fed soybean meal than in those fed leather shavings. Total VFA concentration was increased (P = .02) by supplementation. Supplementation with soybean meal increased (P < .05) ruminal molar proportions of butyrate, valerate, and isovalerate compared with leather shavings. Duodenal OM flow and OM disappearing in the intestines were increased by supplementation (P < .10), but not by the type of supplement fed (P > .10). Ruminal digestion of OM and total tract OM digestion were unaffected (P > .10) by supplementation and the type of supplement fed. Flow and digestion of NDF were unaffected (P > .10) by the treatments. Flow of N and the quantity of N disappearing in the intestines were increased (P < .05) by supplementation but did not differ (P > .10) between supplementation groups. Microbial N flow, N utilization for net microbial protein synthesis, and ruminal N disappearance were unaffected (P > .10) by supplementation and the type of supplement provided. Combining pretanned leather shavings with soybean meal seemed to have no deleterious effects on digestion or fermentation and to allow for escape of some N to the lower tract. Key Words: Cattle, Digestion, Protein Supplements, Festuca arundinacea

In vitro digestion and growth studies were conducted to evaluate the effects of level of soybean oil inclusion in forage-based diets. In Exp. 1, diets were bromegrass hay (H), bromegrass hay and cornsoybean meal supplement (C), C with 3% added soybean oil (O3), and C with 6% added soybean (O6). Diets containing supplements were formulated to be isonitrogenous and isocaloric. Treatment means were compared using a single-degree-of-freedom contrast (H vs C, O3, and O6) and orthogonal polynomial contrasts within diets C, O3, and O6. Diet H had the lowest (P = .0003) IVDMD and a linear decline (P = .0001) in IVDMD was observed from C to O6, but 24-h IVDMD disappearance was greatest (P = .001; quadratic) for O3. Total VFA increased from C to O3 and then decreased from O3 to O6 (quadratic; P = .001), and acetate:propionate ratio decreased linearly (P = .0001) from C to 06. Changes in long-chain fatty acids reflected biohydrogenation by ruminal microbes; however, only 18:3 was hydrogenated to the same extent across all diets. In Exp. 2, 36 Angus x Gelbvieh heifers (260.0 +/- 6.0 kg initial BW) were individually fed C, O3, or O6 as mixed rations for 104 d. Diets were formulated to be isonitrogenous and provide ADG of .91 kg. Feed efficiency and ADG was greatest (P < .02; quadratic) for O3 heifers. Serum NEFA increased linearly (P = .02) and serum glucose (P = .02), cholesterol (P = .002), and GH (P = .04) showed a quadratic response to level of dietary soybean oil. Plasma proportions of 16:0, 16:1, 18:0, and 18:1 increased quadratically (P < .03), and 18:2 increased linearly (P < .001) from C to O6. In Exp. 3, 42 Angus x Gelbvieh heifers (288.7 +/- 6.6 kg initial BW) were divided into six pens (two pens/treatment) in a randomized complete block designed experiment. Rations were delivered as hay plus a top-dressed supplement (C, O3, or O6). Heifers fed O3 conceived 10 d earlier (quadratic; P = .06) than heifers fed C and O6. Other production estimates did not differ (P > .10) among dietary treatments. Inclusion of soybean oil at 3% of a forage-based diet increased total VFA, many blood metabolites, ADG, and feed efficiency, and it decreased time to conception. Adding soybean oil as 3% of a forage-based diet is an acceptable feeding strategy for developing beef heifers. Key Words: Digestion, Fatty Acids, Heifers, Metabolites, Hormones

The established calculation of ruminal extent of degradation using the polyester bag method overestimates extent. The wash fraction, at least in part, is subject to losses from the rumen due to passage. Four formulae are proposed to minimize this risk of overestimation. Four options are considered: 1) passage losses for particulate matter escaping from the bag at zero time are according to the particulate fractional passage rate, 2) the liquid rate, and 3) the average of the two, and additionally 4) there is no instantly degradable fraction. The established and proposed formulae were examined using polyester bag data for six forages: grass silage, fresh ryegrass, fresh white clover, alfalfa hay, mixed grasses hay, and hay from a permanent mountain meadow. The established formula gave appreciably higher estimates of extent of degradation in all cases. Overestimation was at least 6.9, 4.9, 2.9, 2.1, 2.4, and 4.5%, respectively, for the six forages. Key Words: Rumen Digestion, Ruminant Feeding, Mathematical Models, Dry Matter Digestion

In situ and in vivo digestibility experiments were conducted to determine the acceptability, digestibility, and safety of a return chewing gum/packaging (G/P) material mixture when fed to steers. In the in situ experiment, both ruminal and intestinal disappearances were measured. Two ruminally and duodenally cannulated steers, which were given free access to alfalfa hay (AH), were used in this study. Duplicate Dacron bags containing the G/P were incubated in the rumen for 0, 3, 6, 12, 24, and 48 h. After ruminal incubation, the 12-, 24-, and 48-h bags were placed in the duodenum and collected in the feces to determine intestinal disappearance. In situ ruminal DM disappearance was greater than 70% for all substrates tested at 0 h, indicating high solubility of the substrates in water, and began to reach a plateau after 12 h of incubation. Intestinal in situ disappearance was not different (P > .25) from zero. In the digestion trial, four ruminally cannulated steers (337 +/- 21.3 kg BW; mean +/- SD) were used in a 4 x 4 Latin square design with the following treatments: 0) 50% corn (C), 50% AH; 10) 45% C, 45% AH, 10% G/P; 20) 40% C, 40% AH, 20% G/P; 30) 35% C, 35% AH, 30% G/P. Steers fed G/P-containing diets had greater (P < .01) DMI than the control steers. Increasing the G/P resulted in a linear (P < .05) increase in DMI. Apparent DM digestibility tended to be higher (P < .10) for the G/P-containing diets than for the control. A quadratic effect (P < .05) on digestible DMI was observed, with greater (P < .01) digestible DMI values for G/P-containing diets (4.8 vs 5.8 kg/d). Digestible organic matter and total nonstructural carbohydrate intakes followed trends similar to those of DM. Apparent aluminum digestibility of G/P-containing diets was not different (P > .13) from zero. The level of G/P in the diet had no effect (P > .2) on total VFA concentration or ruminal pH. There was a linear decrease (P < .01) in the molar percentage of isobutyrate and isovalerate in addition to a linear increase (P < .01) in butyrate and valerate with increasing levels of G/P. There was a quadratic effect (P < .01) on molar proportions of acetate and propionate and on the acetate:propionate ratio. Results of both experiments suggest that G/P may be fed to safely replace up to 30% of corn-alfalfa hay diets for growing steers with advantages in improving DMI and digestibility. Key Words: Confectionery By-products, Chewing Gum, Steers, Digestion

Our objective was to determine the impact of supplemental energy, N, and protein on feed intake and N metabolism in sheep fed low-quality forage. Six Texel x Dorset wethers (16 mo, 63 +/- 3.1 kg) fitted with mesenteric, portal, and hepatic venous catheters were used in a Latin square design with five sampling periods. Lambs were fed chopped bromegrass hay (4.3% CP) to appetite, and a mineral mixture was given. Treatments were 1) control (no supplement), 2) energy (cornstarch, molasses, and soybean oil), 3) energy plus urea, 4) energy plus soybean meal (SBM), and 5) energy plus ruminally undegraded protein (RUP; 50:50 mixture of blood and feather meals). Supplements were fed once daily (.3% BW). Forage DMI did not differ (P = .13), but intake of total DM, N, and energy differed (P < .01) among treatments. Apparent digestibilities of DM, OM, and energy were less (P < .01) for control than for other treatments. Apparent N digestibility was least for control and energy and greatest for urea treatments (P < .05). As a result, digested DM, OM, and energy ranked from least to greatest were control, energy, urea, SBM, and RUP, respectively. Apparently digested N was 2.44, 2.24, 11.39, 9.80, and 11.25 g/d for control, energy, urea, SBM, and RUP (P < .01; SE = .10). Hour of sampling x treatment was a significant source of variation for blood concentrations of ammonia N and urea N, net ammonia N release from portal-drained viscera (PDV) and liver, and urea N release from splanchnic tissues. These results were primarily because patterns through time for the urea treatment differed from the other treatments. Net PDV release of (alpha)-amino N did not differ (P > .05) between control and energy treatments. Values for those treatments were about one-half of values for urea, SBM, and RUP treatments, which did not differ (P > .05). Hepatic net uptake (negative release) of (alpha)-amino N for control was 53% of values for the other treatments, which did not differ (P > .05). Net release of (alpha)-amino N from splanchnic tissues did not differ among treatments (P = .34) and did not differ from zero. The data indicate that arterial (alpha)-amino N concentration, hepatic (alpha)-amino N uptake, PDV release and hepatic uptake of ammonia N, and hepatic release of urea N were greater in energy than in control treatments. We also found that hepatic uptake of (alpha)amino N was 187% of PDV release in energy-supplemented lambs. These results suggest that energy supplementation of a protein-limiting diet stimulated mobilization of body protein. Key Words: Sheep, Forage, Nitrogen Metabolism

Two experiments were conducted to evaluate the impacts of increasing levels of supplemental soybean meal (SBM) on intake, digestion, and performance of beef cattle consuming low-quality prairie forage. In Exp. 1, ruminally fistulated beef steers (n = 20; 369 kg) were assigned to one of five treatments: control (forage only) and .08, .16, .33, and .50% BW/d of supplemental SBM (DM basis). Prairie hay (5.3% CP; 49% DIP) was offered for ad libitum consumption. Forage OM intake (FOMI) and total OM intake (TOMI) were increased (cubic, P = .01) by level of supplemental SBM, but FOMI reached a plateau when the daily level of SBM supplementation reached .16% BW. The concomitant rises in TOMI and OM digestibility (quadratic, P = .02) resulted in an increase (cubic, P = .03) in total digestible OM intake (TDOMI). In Exp. 2, spring-calving Hereford x Angus cows (n = 120; BW = 518 kg; body condition [BC] = 5.3) grazing low-quality, tallgrass-prairie forage were assigned to one of three pastures and one of eight treatments. The supplemental SBM (DM basis) was fed at .08, .12, .16, .20, .24, .32, .40, and .48% BW/d from December 2, 1996, until February 10, 1997 (beginning of the calving season). Performance seemed to reach a plateau when cows received SBM at approximately .30% BW/d. Below this level, cows lost approximately .5 unit of BC for every .1% BW decrease in the amount of supplemental SBM fed. Providing supplemental SBM is an effective means of improving forage intake, digestion, and performance of beef cattle consuming low-quality forages. Key Words: Beef Cattle, Forage, Intake, Digestibility, Protein

Experiments were conducted to determine the effect of fumaric acid supplementation and buffering capacity of the diet on ileal and fecal digestibilities of CP, GE, and amino acids in early-weaned pigs. In two experiments, 12 pigs each were weaned at 14 d of age and fitted with a simple T-cannula at the distal ileum between 15 and 17 d of age. In both experiments, the pigs were fed four diets, based on wheat and soybean meal without (control) or with 1, 2, or 3% fumaric acid according to a balanced two-period changeover design. In Exp. 2, the buffering capacity of the diets was increased by supplementation of 3% sodium bicarbonate. The pigs were fed three times daily: equal amounts at 8-h intervals. The diets were supplied at a rate of 5% (wt/wt) of body weight. The inclusion of fumaric acid to the diet with a low buffering capacity increased (P < .05) the ileal digestibilities of CP, GE, and the majority of amino acids. The highest responses were found at an inclusion level of 2% fumaric acid. The improvements in apparent ileal amino acid digestibilities ranged from 4.9 to 12.8 percentage units. Supplementation of fumaric acid to a diet with a high buffering capacity led only to numerical increases in ileal digestibilities of CP, GE, and amino acids. In both studies, fumaric acid supplementation had no effect (P > .05) on the fecal digestibilities of CP, GE, and amino acids, except histidine. A high buffering capacity of the diet decreased the ileal amino acid digestibilities by 1 to 10 percentage units compared with diets with the low buffering capacities. In both experiments, ileal and fecal digestibilities were higher (P < .05) in Period 2 (on d 24 after weaning) than in Period 1 (on d 11 after weaning). A positive correlation (P < .05) between ileal digestibilities and fumaric acid supplementation to the diets with the low buffering capacities was observed in Period 1 (on d 11 after weaning), but not in Period 2 (on d 24 after weaning). No relationship (P > .05) between ileal digestibilities and fumaric acid supplementation to the diets with a high buffering capacity could be established. In conclusion, supplementation of fumaric acid to starter diets during the first 3 to 4 wk after weaning increases the ileal digestibilities of GE, CP, and amino acids. Key Words: Pigs, Amino Acids, Digestibility, Fumaric Acid, Buffering Capacity

Tests indicate that repeated ingestion of an 8% CHO driink during exercise significantly lowers the rate of gastric emptying at these carbohydrate concentrations, but lower carbohydrate concentrations do not. Beverage osmolality is less important than beverage enrgy content in influencing gastric emptying rate at these carbohydrate concentrations.

The creation of a finely dispersed lipid emulsion is essential for efficient hydrolysis of dietary triglycerides. The effectiveness of emulsification within the stomach depends upon the shear force generated by gastric motility and the concentration of emulsifiers present in the gastric contents. Other dietary constituents can modify these factors, and previous studies have suggested that the presence of soluble non-starch polysaccharides (NSP) during digestion might increase the average size of intraluminal emulsion droplets. In the present study, we developed a new technique for the isolation and analysis of intraluminal lipid emulsions by optical diffraction analysis. The method was applied to rats fed powdered semipurified diets that were free of all NSP or supplemented with insoluble cellulose, guar gum, or NSP derived from apple, carrot or rolled oats. Cellulose had no significant effect on emulsion size, and there was no evidence that the average sizes of lipid droplets in the gastric fundus or antrum were higher than control values in rats fed diets supplemented with any source of soluble NSP. In the groups fed oats and cooked carrot NSP, the mean droplet diameters approached half the values for diets free of NSP or containing insoluble cellulose. The difference between rats fed NSP from cooked carrot and those fed cellulose was significant in the proximal stomach (P < 0.05), and that between rats fed raw oats and rats fed cellulose was significant in the distal stomach (P < 0.05). Soluble dietary fiber does not inhibit lipid or cholesterol absorption via any inhibition of lipid emulsification. KEY WORDS: lipids; dietary fiber; non-starch polysaccharide; digestion; rats

The complexity of ruminant digestion necessitates a greater variety and complexity of experimental methods than with any other species. The fact that dietary ingredients are first subjected to microbial fermentation requires elaborate measures to ascertain nutrients presented for absorption. Numerous approaches have been attempted to obtain representative samples of digesta at sites throughout the gastrointestinal tract. The choices of a researcher before an experiment include animal(s), site(s) for cannula placement, style of cannula, cannula material, and numerous other more subtle factors that may contribute to the success of an experiment. This review compares the advantages and disadvantages of various approaches, cannula types, and cannula materials that should be considered before experiments are conducted. Key Words: Surgery, Cannulation, Ruminants, Small Intestine, Digestion

Hydroxyethylsoyamide (HESA) was reported previously to protect soybean oil from ruminal biohydrogenation and increase plasma unsaturated fatty acids in sheep. Two digestibility trials with sheep and a rumen in vitro trial were conducted in this study to determine the effects of HESA on ruminal VFA and nutrient digestibility. Trial I was a 4 x 4 Latin square with 17-d periods in which four wethers were fed either a control diet (CON) with no added fat, 2.5% soybean oil (SBO), 5% butylsoyamide (BuSA), or 5% HESA. The HESA diet was ground with a mortar and pestle before feeding to disperse fat lumps that formed during diet mixing. Compared with the CON diet, the HESA diet reduced DMI, acetate/propionate (A/P), and total tract fiber digestibility, but these were not affected by SBO or BuSA. Trial 2 was a 24-h rumen in vitro study showing that total VFA concentration and A/P in cultures were reduced by 10% linoleic acid but not by 10% ethanolamine or 10% HESA. In Trial 3, four wethers were fed the CON and HESA diets in a replicated 2 x 2 Latin square to determine digestibility responses to HESA when grinding was avoided. Fiber digestibilities and A/P were not affected by HESA in Trial 3. The HESA in this study had variable effects on fiber digestibility that may have been related to physical attributes of the diet, including particle size. Substitution of ethanolamine for butylamine during synthesis of the amide increased fatty acid digestibility but reduced dry matter intake. Key Words: Soybean Oil, Digestibility, Volatile Fatty Acids, Sheep

A variety of factors influence the results of digestion studies designed to measure ruminal disappearance of nutrients arid flow of nutrients to the intestine. Feed intake, marker usage, sample collection, statistical design, and computation methods are among the factors discussed in this review. Guidelines are provided for presentation and interpretation of data from digesta flow studies. The scientific value of such studies often is limited because 1) replication, relative to expected variation, is inadequate and 2) experimental animals are not maintained under conditions similar to those used in normal production. Because studies conducted with inappropriate methods or inadequate replication are of little value and waste resources, validation of techniques is critical, and individual researchers should strive to verify their techniques. Key Words: Ruminants, Digestibility Markers, Experimental Design

The site of nutrient digestion in the gastrointestinal tract of ruminants affects nutrient availability and the nature of digestive end-products supplied to the host animal. Methods to study site of digestion in vivo provide a tool to obtain data that enhance the ability to interpret or predict animal responses to some feeding practices. Examples are discussed for which site of digestion data provided insights that might not have been evident from other approaches. The use of site of digestion techniques may provide interpretations regarding digestion of N by ruminants different from those derived from measurement of total tract N digestion. Site of digestion measurements have been particularly important in studying effects of heat processing of protein sources and in understanding the nature of digestion of N in high-quality, fresh forages. Moreover, site of digestion techniques have been instrumental in interpreting the influences of supplemental fat sources on ruminal digestion and ruminal biohydrogenation and small intestinal digestion of long-chain fatty acids. Key Words: Digestion, Rumen, Small Intestine, Nitrogen, Long-Chain Fatty Acids

In two experiments, we investigated various factors that affect the estimation of the apparent total tract digestibility (ATTD) of DM, Ca, and total P in diets for growing-finishing pigs. In Exp. 1, the effects of age, housing, and calculation method (indicator [[Cr.sub.2][O.sub.3]] vs 10-d total collection) were determined. Eighteen barrows and gilts (40 to 95 kg BW) were housed in six pens, and ATTD was estimated using the indicator method. Twelve barrows were housed in metabolic crates, and ATTD was estimated using both calculation methods. Dietary treatments were 1) a tapioca-soybean-barley-based diet, 2) Diet I supplemented with 400 FTU microbial phytase/kg of diet, and 3) a corn-soybean meal-based diet. In Exp. 2, six barrows (95 to 120 kg BW) were fed a phytase-deficient diet to investigate the effects of coprophagy (40 g fresh feces/kg of diet) and movement. Pigs were fed at 2.8 times maintenance requirement (418 kJ [ME/BW.sup..75]); water supply was 2.5 L/kg of feed. The ATTD increased as BW increased. Phytase enhanced total P ATTD by an average of 18.1 percentage units. The ATTD of DM was higher and the ATTD of Ca and total P (P < .001) were lower in pigs housed in pens than in pigs housed in metabolic crates. Fecal consumption and movement led to numerical increases in Ca (P = .217) and total P (P =. 103) ATTD. Estimates of Ca and total P ATTD using pigs in metabolic crates are lower than estimates in practice. Key Words: Pigs, Digestibility, Phosphorus, Calcium, Coprophagy, Housing

We have developed a system for chronically catheterizing 10- to 25-d-old pigs that permits stable isotope tracer studies of intestinal or colonic assimilation of nutrients. This model also can be used to ensure constant enteral feeding or to assess the rate of entry into the terminal ileum of carbohydrates, fats, and amino acids. A plastic cannula with a luminal flange can be surgically placed in the stomach for tracer studies of sugar digestion or for controlled infusion of any formula diet. A similar cannula can be placed in the cecum for infusion of tracer and(or) substrates for studies of fermentation. The cannula has been machined so that a washer and nut can be threaded onto it, allowing the entire apparatus to be fixed to the abdominal wall. The distal end protruding above the skin was tapered to fit standard i.v. extension tubing. A carotid arterial catheter was used to sample substrates for isotopic enrichment measurements. Key Words: Pigs, Digestion, Fermentation

Ninety-six (Finnish Landrace x Dutch Landrace) reproductive sows were used at parities 1, 3, 5, and 7 + 8 from d 107 of gestation to d 21 of lactation to investigate the effects of diet and parity on apparent total tract digestibility (ATTD). Animals were randomly assigned to one of four dietary treatments. Dietary treatments were 1) a P-deficient (1.1 g digestible P [dP]/kg) Dutch semipractical diet; 2) Diet I supplement.ed with 400 FTU Aspergillus niger phytase per kilogram of diet (1.7 g dP/kg); 3) a corn-soybean meal-based diet (1.3 g dP/kg); and 4) Diet 3 supplemented with extra monocalcium phosphate (MCP; 2.4 g dP/kg of diet). Animals were fed twice daily at 2.8 times maintenance (418 kJ ME/ BW.75) from d 8 to the end of lactation. Feces and urine were collected during d 11 to 13 and d 18 to 20 of lactation. The ATTD of DM, OM, ash, CP, Ca, Mg, and total P (P < .01) were higher for the corn-soybean meal-based diets than for the Dutch semipractical diet not supplemented with phytase. Addition of MCP enhanced total P ATTD by an average of 6.7 percentage units. Addition of microbial phytase improved Ca, Mg, and total P ATTD, but the effects were dependent on the stage of lactation. Lower ATTD of OM and CP were seen for first parity animals compared with higher parity sows. The ATTD of Mg increased with increasing parity. Parity had little effect on the ATTD of minerals during lactation, and dietary effects were prominent and followed a similar trend to those seen in growing-finishing pigs. Key Words: Pigs, Digestibility, Lactation, Parity, Calcium, Phosphorus

Limited information is available on the utilization of different types of diets by captive exotic felid species. Utilization of diets by small exotic felids may differ depending on the diet fed. Eight sand cats (Felis margarita), which are small, 2- to 4-kg cats, were used to examine the digestibility of two types of diets: a raw meat-based diet and a dry kibble diet. Dry matter, crude protein and energy intakes and digestibilities were evaluated. Digestibilities for dry matter, energy, and crude protein were 83.5 [+ or - ]4.8, 89.6 [+ or -] 5.2, 92.4 [+ or -] 5.3% for the raw meat-based diet and 72.7 [+ or -] 12.3, 76.8 [+ or -] 14.5, and 77.9 [+ or -] 13.5% for the kibble diet. Physiological variables also were examined and included plasma taurine, vitamin A, retinyl palmitate, [Beta]-carotene, calcium, and phosphorus. Plasma taurine means were 91.4 [+ or -] 8.4 [[micro]mol]/L in cats consuming the raw meat-based diet and 248.0 [+ or -] 23.2 [[micro]mol]/L in cats consuming the kibble diet. Plasma phosphorus was 5.2 [+ or -] .1 and 4.5 [+ or -] .1 mg/dL, respectively, in cats consuming raw meat-based and kibble diets. [Beta]-Carotene was 25.2 [+ or -] 2.9 and 2.9 [+ or -] .3 [[micro]gram]/dL, respectively, for cats consuming the raw meat-based and kibble diets. These results indicate that diets formulated for small captive exotic felid species should be evaluated with respect to diet type and nutrient utilization. Key Words: Felis, Cats, Digestibility, Intake, Utilization

We performed an experiment with 112 piglets, 32 growing-finishing pigs, and 12 sows during pregnancy and lactation to test the hypotheses that apparent total tract digestibilities of P and Ca as well as the efficacy of Aspergillus niger phytase in rendering phytate P available in pigs depend on pig physiological status. All pigs were fed diets with identical feedstuff composition either without or with added microbial phytase (Natuphos[R], 500 FTU/kg diet). The diets contained 6.2 g Ca, 4.8 g total P, and 3.7 g phytate P per kilogram, and intrinsic phytase activity of 120 FTU/kg. The digestibility of P increased by 8.3 percentage units when BW of pigs increased from 30 to 60 kg and then remained stable until 100 kg. Pregnant sows had a lower efficiency of P absorption than piglets and growing-finishing pigs. During lactation, the efficiency of P absorption was 3.4 percentage units higher than during pregnancy but was still 6.6 percentage units lower than for growing-finishing pigs. The efficacy of the phytase in generating digestible P decreased in the order of lactating sows, growing-finishing pigs, sows at the end of pregnancy, piglets, and sows at midpregnancy; the average amounts of generated digestible P were 1.03, .83, .74, .66, and .32 g/kg diet, respectively. The addition of phytase to the diet raised apparent Ca digestibility in the piglets and growing-finishing pigs (by 4.6 and 4.0 percentage units, respectively) but not in the sows. We conclude that in the formulation of swine diets the amount of phytase to be added should be tailored to the target category. Key Words: Pigs, Animal Physiology, Phytase, Digestibility, Phosphorus, Calcium

Adaptations to and consequences of an herbivorous diet in grouse and waterfowl were studied using a diet selection in the context of their herbivorous diets. It was discovered that both grouse and waterfowl prefer plant foods with higher concentrations of protein. Grouse and waterfowl have slightly different digestive morphology and structure. Meanwhile, the ceca which is a part of their digestive structure, plays an important role in the nitrogen balance for grouse. This explains the reason why they are able to survive in habitats with poor quality food.

One hundred twenty medium-frame crossbred steers (364 kg) were used in a 106-d feedlot trial to compare the feeding value of Condor, a hulless barley (HB), with Leduc, a conventional covered barley (CB). Dietary treatments consisted of a finishing diet containing 77% grain (DM basis) as 1) steam-flaked corn (SFC); 2) dry-rolled HB (DRB-H); 3) steam-flaked HB (SFB-H); 4) dry-rolled CB (DRB-C); and 5) steam-flaked CB (SFB-C). Feed intake was lower (8.6%, P < .01) for HB than for CB. Diet NE was greater for HB than for CB (P < .01) and for SFB than for DRB (P < .01). Incidence of liver abscess was greater for DRB than for SFB (239%, P < .05) and for HB than for CB (167%, P < .10). Diet NE were greater (P < .10) for SFC than for barley treatments. Treatment effects on characteristics of digestion were evaluated using five Holstein steers (202 kg) with cannulas in the rumen and proximal duodenum. There were barley variety x grain processing interactions on ruminal digestion of OM (P < .10), ADF (P < .05), and starch (P < .05). Ruminal OM digestion increased (9.0%) with steam flaking HB and decreased slightly (1.9%) with steam flaking CB. Ruminal digestion of starch was enhanced more dramatically (21.5 vs 8.4%, respectively) with steam flaking HB than with CB. Steam flaking decreased ruminal ADF digestion of HB only slightly (6.2%), whereas with CB the decrease was more dramatic (54.3 %). Ruminal degradable N was greater (P < . 10) for CB than for HB and for DRB than for SFB (19.8%, P < .05). Estimates of ruminal degradable N in DRB-H, SFB-H, DRB-C, and SFB-C were 69.7, 53.9, 78.5, and 65.0%, respectively. Postruminal digestion of OM (P < .01), starch (P < .05), and N (P < .10) were greater for HB than for CB. Steam flaking barley increased (P < .01) postruminal N digestibility. Total tract digestibility of OM (P < .01), ADF (P < .05), starch (P < .01), and energy (P < .01) were greater for HB than for CB. Digestibility of ADF in barley hulls was only 6.4%. Steam flaking increased (P < .01) total tract digestibility of starch. Ruminal digestibility of OM and feed N was lower (P < .01) for SFC than for barley diets. Ruminal pH was lower (P < .10) for HB than for CB and for SFB than for DRB (P < .01). Ruminal propionate was higher (24.1%, P < .01), and methane was lower (17.9%, P < .01) for HB than for CB. Key Words: Barley, Maize, Processing, Cattle, Dry Lot Feeding, Metabolism

Conventional and stable isotopic methods, or physiological or metabolic effects fail to distinguish intrinsic and non-milk extrinsic sugars, but ingestion of these sugars has implications for the overall diet. The food source and the way in which food is eaten provides an estimate of whether it has intrinsic or non-milk extrinsic sugar. Foods with intact sugars are digested and absorbed more slowly. Reduced intake of extrinsic sugar-rich food also reduces the intake of micronutrients and other biologically active constituents.

A study conducted to determine the relationships between the composition of dietary fibre in several agro-industrial by-products and the digestion and transit time in rats find that glucose increases the stools' weight and decreases the mean retention time and digestibility in water-soluble dietary fibers. Regression analysis between the dietary fibre (DF) constituents are difficult to perform due to the different composition of the DF sources.

Electron microscopic studies of the digestion of banana starch granules in the small intestine of humans reveal encapsulation and resistance of the granules to be the cause for the low digestibility of banana starch. Irregular shape of the granules is also responsible for the resistance of banana starch to amylase hydrolysis.

The lysosomal indopeptidase cathesin L mediates the leupeptin-sensitive intracellular degradation of gastric intrinsic factor (IF). Antiserum against a human kidney cDNA cathepsin L fusion protein indicates the presence of cathepsin L in rat intestinal mucosa. Cathepsin L-mediated degradation of IF is partially blocked upon binding of cobalamin.

Digestibility data generally are analyzed as ratio variables, but to be useful this method requires that animals consume large quantities of food. If little is eaten, as may occur with novel or unpalatable foods, apparent digestibility estimates can be seriously biased and statistical analyses may suffer from very low power to detect digestibility differences among foods. Moreover, ratio variables are undesirable for statistical analyses. We suggest that for many wildlife studies, true digestibility estimated from regression analysis is preferable to apparent digestibility estimated from ratio variables. True and apparent digestibilities were determined from the same data set. The regression method for estimating true digestibility was more applicable to wildlife species, provided greater statistical power, and avoided the unreliability of ratio variables used to estimate apparent digestibility. The advantages of the regression method are illustrated using data on digestibility of three woody forage species eaten by beavers (Castor canadensis).

Altered DNA reveals two lesions, (+)-trans-anti-BPDE-N2-dG and (-)-trans-anti-BPDE-N2-dG which are the mononucleotide trans incorporation of two anti-BPDE enantiomers. The lesions reveal variations in enzymatic processing which are determined by basic exonucleases. The working of direction-responsive enzymes are influenced in various ways by organizations of bulky pyrenyl residues.

A study of the digestion of chitin by Northern Bobwhites and American Robins was presented. Results show that Northern Bobwhites metabolize energy in a significantly higher rate than that of American Robins. The chitin digestibility in both species was measured. The observed chitin digestibility was higher in Bobwhites. However, it was higher with American Robins after acclimation.