The effect of condensed tannins from heated and unheated cottonseed on the ileal digestibility of amino acids for the growing rat and pig

The effect of condensed tannins (CT) from heated and unheated cottonseed on the apparent ileal digestibility of amino acids for the growing rat and pig was determined. In Expt 1, twenty-four rats were allocated to four semi-purified diets which contained cottonseed kernel and hulls as the only protein source. Two of the diets contained unheated solvent-extracted cottonseed kernel and hulls, while the remaining two diets contained similar material but which had been heat-treated by autoclaving at 110 degrees for 120 min. In Expt 2, twelve rats and twelve pigs were fed on four semi-purified diets containing commercial cottonseed meal (CSM) as the only protein source. Cr2O3 was added to all diets as an indigestible marker. For each pair of diets in both experiments, PEG was either included or excluded. The effect of CT was assessed by comparing control animals (-PEG; CT acting) with PEG-supplemented animals (+PEG; CT inactivated). Ileal contents from the terminal 150 and 450 mm of ileum were collected at slaughter, 7 h from the start of feeding, for the rats and pigs respectively. Apparent ileal amino acid digestibility for rats fed on the diet containing cottonseed kernel and hulls was significantly depressed by the heat treatment, particularly for lysine and threonine. On average, apparent ileal amino acid digestibility in the diets without PEG was decreased from 0.80 to 0.70 by heat treatment. Dietary cottonseed CT depressed apparent ileal protein digestibility in the pig and in the rat. The addition of PEG to the diets significantly increased the apparent ileal digestibility of N and some amino acids for the pigs and the rats. The mean increase in apparent ileal digestibility due to PEG addition for the fourteen amino acids was 2 percentage units in both species fed on the commercial CSM diets, and 2 or 4 percentage units in rats fed on the unheated or the heated cottonseed kernel and hull diets respectively. The effect of PEG was similar in the heated and unheated cottonseed kernel and hulls for most amino acids, but apparent ileal digestibilities of threonine, tyrosine and lysine were increased more by PEG in heated than in unheated CSM. Apparent ileal N digestibility was lower in the pig than in the rat. For several of the amino acids there were significant animal species differences in apparent ileal digestibility. Studies into the effects of cottonseed CT should be carried out in the target animal species. The commercial CSM had a low apparent ileal amino acid digestibility overall, particularly for the essential amino acids lysine and threonine. It was concluded that effects of heating did not eliminate the reversible reactivity of cottonseed CT on amino acid digestion in rats and pigs but rather appeared to increase it for threonine, tyrosine and lysine in Expt 1, causing large reductions in apparent ileal digestibility of these amino acids.     

Nitrogen utilization in pigs fed diets with soybean and rapeseed products leading to different ileal endogenous nitrogen losses

Nitrogen (N) balance was determined in 36 pigs (BW 24 to 30 kg) fed diets inducing different ileal endogenous N losses (ENL). We tested the hypothesis that enhanced ENL may be indicative of a higher recycling of endogenous proteins that will induce a greater urinary N loss and a lower efficiency of the dietary N utilization for retention. The cornstarch-based diets contained either soy concentrate (SC), soybean meal (SBM), a mixture of toasted and untoasted soybean meal (mSBM), dehulled-toasted rapeseed cake (RC1), non-dehulled-toasted rapeseed cake (RC2), or dehulled-untoasted rapeseed cake (RC3). The diets were balanced for their content of apparent ileal digestible (ID) CP (108 g/kg feed) and apparent ID of Lys, Thr, Met+Cys, Trp, and Ile. Feeding level was 2.7 times ME for maintenance per kilogram BWx75 and restricted to 88% of the requirements for ID Lys as the first-limiting amino acid. During a 5-d period, urine and feces were collected daily in metabolism cages. Compared with the SC diet (low ENL), the diets with SBM (medium ENL) and mSBM (high ENL) resulted in a greater (P < .05) urinary N excretion. Nitrogen retention tended to be less (P = .08) in pigs fed diets that caused greater ENL. The utilization of ID N for retention in pigs fed the mSBM diet was lower (P < .05) than for those fed the SC diet. There were no differences in urinary N excretion, N retention, and the utilization of ID N for retention in pigs fed the rapeseed diets of different fiber contents (hulls as the NDF source). We concluded that, at similar intakes of the first-limiting ID amino acid, N retention in pigs fed soybeans tended to be reduced by greater ENL as induced by antinutritional factors (e.g., trypsin inhibitors). Rapeseed hulls, as the predominant fiber source, do not affect N retention and the utilization of ID N for retention.     

Effect of amount of dietary supplement and source of protein on milk production, ruminal fermentation, and nutrient flows in dairy cows

An experiment with a multiple Latin square design using 36 midlactation Friesian cows was carried out to determine the effect of fish meal or soybean meal in a supplement fed at two amounts (3.5 or 7 kg/d) with grass silage. The diets were also fed to four ruminally and duodenally cannulated cows to determine digestibility, ruminal fermentation, and nutrient flows. Dry matter intake, milk production, milk constituent yields, and concentrations of protein and lactose were significantly increased by the supplements when provided at 7 kg/d. The supplement containing fish meal increased milk production, protein and lactose yields, and milk protein concentration, but the increases were smaller than those obtained by increasing the amount of supplement fed. Neither the type nor the amount of supplement fed affected digestibility of dry matter or organic matter, and few significant effects on ruminal fermentation were observed. Supplements fed at the higher allowance significantly increased the flow of dry matter, organic matter, all nitrogenous components, and amino acids to the duodenum. The supplement containing fish meal significantly increased the duodenal flow of nonammonia nonmicrobial N and some amino acids. Results indicated that an increase in the concentration of supplement in the diet is more effective in increasing milk production, protein concentration and yield, and flow of amino acids to the duodenum than is increasing the concentration of ruminally undegradable protein in the supplement.     

Utilization of ileal digestible amino acids by growing pigs: methionine

An experiment was conducted to determine the utilization of ileal digestible methionine by growing pigs. Three methionine-deficient diets (0.09 g ileal digestible methionine/MJ digestible energy (DE)) were formulated using cottonseed meal, meat-and-bone meal and soya-bean meal respectively as the only source of methionine in the diet. An additional three diets were formulated with supplements of methionine to confirm that methionine was limiting in the first three diets. The growth performance and retention of methionine by pigs given the six diets over the 20-45 kg growth phase was then determined. Growth rates (g/d) of pigs given the three diets formulated to 0.09 g ileal digestible methionine/MJ DE were significantly different (P < 0.01): cottonseed meal 411, meat-and-bone meal 442, soya-bean meal 496 (SED 24.6). The response of pigs to the addition of methionine confirmed that methionine was limiting in these diets. Crude protein (N x 6.25) deposited by the pigs (g/d) was significantly higher (P < 0.05) for those given soya-bean meal (61) and meat-and-bone meal (57) relative to cottonseed meal (47; SED 3.3). The proportion of ileal digestible methionine retained by pigs given the three protein concentrates was: cottonseed meal 0.39, meat-and-bone meal 0.45, soya-bean meal 0.47 (SED 0.019). These results indicate that values for the ileal digestibility of methionine in protein concentrates do not reflect the proportion of methionine that can be utilized by the pig. It appears that, with heat-processed meals, a considerable proportion of the methionine is absorbed in a form(s) that is (are) inefficiently utilized.     

Resistant proteins alter cecal short-chain fatty acid profiles in rats fed high amylose cornstarch

The objective of this study was to examine the physiologic importance of undigested protein on cecal fermentation in rats fed a low (LAS) and high (HAS) amylose cornstarch. In Experiment 1, rats were fed diets containing LAS (655 g/kg diet) with one of four protein sources: casein, rice (RP), potato (PP) or soybean protein (SP) at 250 g/kg diet for 15 d. Apparent digestibilities of casein, RP, SP and PP were 96, 94, 93 and 92%, respectively. In rats fed the LAS diet with casein, acetate, propionate and succinate were the major cecal organic acids. The succinate pools in rats fed RP or SP were significantly lower than in those fed casein, whereas butyrate did not differ. Butyrate was significantly higher in rats fed PP, but succinate was the same as in rats fed casein. In Experiment 2, rats were fed diets containing HAS (200 g/kg diet) with one of the four protein sources at 250 g/kg diet for 10 d. HAS was substituted for the same amount of LAS. In rats fed the HAS diet, succinate was the major acid in rats fed casein; in rats fed RP or PP, however, the pools of this acid were significantly lower than in those fed casein, whereas butyrate was significantly higher in rats fed RP or PP. Fecal starch excretion was significantly lower in rats fed RP or PP than in those fed casein. In Experiment 3, rats were fed the casein-HAS diet with graded levels of PP (0, 10, 30, 50, 100 and 250 g/kg diet) for 14 d. The PP was substituted for the same amount of casein. Cecal butyrate was low in rats fed up to 100 g of PP/kg diet and then rose with 250 g of PP/kg diet. In Experiment 4, ileorectostomized rats were used and fed the same diets described in Experiment 3 for 9 d. The ileal starch/nitrogen ratio declined with increasing dietary PP, due solely to greater nitrogen excretion, whereas starch excretion was unaffected. In Experiment 5, rats were fed the casein-HAS diet with or without 60 g of artificial resistant protein/kg diet for 10 d. The resistant protein (apparent digestibility, 63%) was substituted for the same amount of casein. Rats fed the casein-HAS diet with resistant protein had significantly greater cecal butyrate and lower succinate than those fed the casein-HAS diet. These data show that large bowel fermentation of starch is altered by dietary protein. They support the hypothesis that nondigested protein, namely, resistant protein, may control fermentation efficiency as well as the fermentation profile of HAS, possibly as a result of a change in microflora through the change in the ratio of starch to nitrogen in the cecum.     

Effects of supplemental protein source on intraruminal fermentation, protein degradation, and amino acid absorption

Cannulated steers were used to determine the effects of supplemental soybean meal, heated soybean meal, fish meal, and a combination of fish meal, heated soybean meal, and corn gluten meal on intraruminal protein degradation and absorption of AA from the small intestine. Organic matter digestion in the reticulo-rumen was greater in steers fed diets supplemented with soybean meal, but whole tract digestibility was not affected by protein source. Total and bacterial CP flows to the abomasum were lower in steers fed diets supplemented with fish meal than in steers fed diets supplemented with heated soybean meal or the combination supplement. Dietary CP flow was 33.5% higher in steers fed diets supplemented with heated soybean meal than in steers fed diets supplemented with soybean meal, fish meal, or the combination supplement. Less essential and nonessential AA flowed to the abomasum and were absorbed from the small intestine of steers receiving diets supplemented with soybean meal. Digestibility of small intestine AA was 21.9% lower in steers receiving the soybean meal treatment. Abomasal flows of Met and Thr and absorption of Lys, Met, and Thr were increased in steers fed diets containing heated soybean meal, fish meal, and the combination supplement. These results suggest that the supply of AA deficient in microbial CP (Lys, Met, and Thr) can be increased and that absorbed AA balance can be changed markedly by selection of rumen escape protein supplements.     

The effects of roasting temperature applied to whole soybeans on site of digestion by steers: II. Protein and amino acid digestion

A 4 x 5 Youden square design was used to determine the effect of roasting temperature of whole soybeans on escape of CP from the rumen and disappearance of N from the small intestine in steers. Four steers (average BW 373 kg +/- 30.7) cannulated at the rumen, duodenum, and ileum were fed each of five diets (1.8% of BW) over five periods. The basal diet contained corn silage (50% of diet DM), alfalfa hay (24%), corn-urea premix (6%), corn starch grits (16.6%), and soybean oil (3.4%). Soybeans (16% of diet DM), either raw or heated to an exit temperature of 141, 149, or 157 degrees C in a commercial roaster, replaced the soybean oil and most of the corn starch grits in the soybean-containing diets. Ruminal ammonia N was lower (P < .05) for the basal diet than for the soybean-containing diets. Roasting temperature of whole soybeans had no significant impact on ruminal ammonia N. Total N reaching the duodenum was greater (P < .05) for steers fed the soybean diets than for steers fed the basal diet. Non-bacterial N (dietary N) at the duodenum was increased (P < .05) by feeding soybeans. Soybean N reaching the duodenum decreased with increased roasting temperature. Increased roasting temperature of whole soybeans seemed to make the soybeans more brittle, subsequently increasing degradation of CP in the rumen. However, disappearance of soybean N in the small intestine, as a proportion of the soybean N entering the small intestine, increased with increased roasting temperature. Apparent total tract N digestibility was increased (P < .05) by feeding soybeans. Flow to the duodenum and small intestinal digestibility of total, essential, and nonessential amino acids increased (P < .05) when soybeans were fed and when roasted vs raw soybeans were fed. Under normal roasting conditions, it seemed that little potential for heat damage to the soybean protein existed. Instead, undesirable effects of heating on handling characteristics of the soybeans were reached before the point at which loss of nutritive value occurred. Feeding steers diets containing roasted whole soybeans increased the N and amino acids available to steers over steers fed diets containing raw soybeans due to increased ruminal soybean nitrogen escape and increased small intestinal digestibility.     

Effect of protein-induced calciuria on calcium metabolism and bone status in adult rats

45Ca-labeled adult male rats were fed diets high in protein to determine long-term effects on calcium metabolism and bone status. Factors influencing renal excretion of calcium were examined for their involvement in protein-induced hypercalciuria. Control rats were fed a 6% casein diet. Test diets contained 6% casein plus 24% protein as lactalbumin, beef, casein, soy, egg white or gelatin. All diets were equal in Mg, P, and Ca. Collections made during the 20-week feeding regimen indicated a transient but marked calciuria (greater than or equal to 200% of control) occurring at or prior to days 56-59 by rats fed the lactalbumin, egg white, gelatin (P less than or equal to 0.001) and 30% casein (P less than or equal 0.01) diets. Soy and beef diets were not calciuric. At days 56-59, rats fed lactalbumin, 30% casein, soy and egg white exhibited significantly depressed urinary specific activity of calcium (P less than or equal to 0.001), and all rats fed test diets produced higher fecal endogenous calcium, suggesting an increased absorption. No compositional differences indicative of bone resorption were present in the femur or mandibles of any rat fed test protein, dismissing bone as the source of calciuria. End-products of protein metabolism known to chelate calcium or compete with its renal reabsorption were significantly correlated with urinary calcium; these included sulfate, oxalate and sodium.     

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.     

Cholestyramine and a fat-free diet lower apolipoprotein A-IV mRNA in jejunum and cholestyramine lowers apolipoprotein A-I mRNA in ileum of rats

To investigate the effect of bile acids or dietary lipid on the expression of intestinal apolipoproteins, the mRNA levels of apolipoprotein A-I and A-IV in the intestine from rats fed a diet containing cholestyramine or a fat-free diet were compared with those from rats fed a control diet containing 25% casein and 5% corn oil. Plasma total cholesterol concentration was lower after 16 h in rats fed a diet containing cholestyramine or a fat-free diet than in rats fed a control diet. In rats fed the fat-free diet, HDL cholesterol concentration also was lower than in those fed the control diet. The pool of bile acid in intestinal contents was significantly lower in rats fed cholestyramine than in both other groups. The relative abundance of jejunal apolipoprotein A-I mRNA did not differ between groups. Jejunal apolipoprotein A-IV mRNA abundance was significantly lower than in controls in rats fed the fat-free and cholestyramine-containing diets. Abundance of apolipoprotein A-I mRNA in ileal mucosa was comparable to controls in rats fed a fat-free diet but was significantly lower in rats fed cholestyramine. Ileal apolipoprotein A-IV mRNA tended to be lower in rats fed cholestyramine and a fat-free diet than in controls. We propose that decreased absorption of dietary lipid may modulate changes in jejunal apolipoprotein A-IV mRNA level and low levels of bile acids in the lumen may modulate changes in ileal apolipoprotein A-I mRNA level.     

The use of 15N-labeled dietary proteins for determining true ileal amino acid digestibilities is limited by their rapid recycling in the endogenous secretions of pigs

We assessed the use of 15N-labeled dietary proteins as a possible tool for the determination of the true ileal amino acid (AA) digestibility in pigs. The first experiment was designed to study the dietary N excretion pattern at the ileum subsequent to the ingestion of a single 15N-labeled meal. In a second experiment, we compared ileal endogenous AA outputs and true AA digestibility estimates obtained in pigs ingesting 15N-labeled dietary proteins in a single meal vs. intravenous infusion of [15N]leucine for 10 d during the ingestion of a pea-based diet and a protein-free starch diet. The proportion of endogenous N found in the ileal digesta differed when the label was delivered orally (50%) vs. intravenously (72%) and changed with time. As a consequence, the true ileal AA digestibilities measured with labeled diets were lower. A third experiment demonstrated that this was due to the rapid recycling of labeled dietary N in endogenous moieties, because 15N was found in blood within 10 min of consuming the labeled meal, within 50 min of consumption in pancreatic enzymes, 90 min in bile and 4 h in ileal mucins. We conclude that the use of 15N-labeled meals for determination of true ileal AA digestibilities is limited by the fast recycling of dietary N in endogenous secretions following a single 15N-labeled meal. The accuracy of results will depend on meaningful estimates of AA flow during a limited period and accurate estimates of 15N in AA.     

The effect of dietary fat content on amino acid digestibility in young pigs

Studies were carried out with 12 pigs (Yorkshire x Landrace) to determine the effect of dietary fat content on amino acid digestibility. The pigs were weaned at 21 d of age and fitted with a simple T-cannula at the distal ileum at 27 or 28 d of age. After a 7-d recuperation period, the pigs were fed one of four isonitrogenous cornstarch-based soybean meal diets (22.5% CP) containing 3.2, 6.2, 9.2, or 12.2% canola oil according to a balanced two-period change-over design. The pigs were fed four times daily, equal amounts, at 6-h intervals. The diets were supplied at a rate of 5% of the average body weight that was determined at the initiation of the first (11.0 kg) and second (12.5 kg) experimental period. Each experimental period consisted of 10 d. Feces were collected for 48 h on d 6 and 7 and ileal digesta for 24 h during d 8, 9, and 10. Chromic oxide was used as digestibility marker. The apparent ileal digestibilities of most of the amino acids increased linearly (P < .05) with increasing dietary fat levels. There were differences (P < .05) in the ileal digestibilities of most of the amino acids between the diets containing 3.2 and 12.2% canola oil. Conversely, the dietary level of inclusion of canola oil did not affect (P > .05) the fecal amino acid digestibilities. The protein-sparing effect of additional canola oil inclusion results, in part, from an increase in ileal amino acid digestibility.     

Apparent digestibility of nutrients in diets with different energy density, as estimated by direct and marker methods for pigs with or without ileo-cecal cannulas

The objective of this study were a) to compare the apparent total tract digestibility (TD) between non-cannulated (intact) and cannulated (steered ileo-cecal valve technique, SICV) pigs fed diets differing in energy density (Exp. 1) and b) to compare the direct vs marker (Cr2O3) methods for estimation of the TD and apparent ileal digestibility (ID) in SICV-cannulated pigs (Exp. 2). In Exp. 1, 24 intact and 18 SICV-cannulated castrates of approximately 40 kg initial BW were randomly assigned to six treatments in a 2 x 3 x 2 factorial arrangement (two pig types, three carbohydrate sources, and two fat levels). In Exp. 2, the same SICV-cannulated pigs from Exp. 1 were given those treatments in a 2 x 3 x 2 factorial arrangement (two methods of digestibility estimation, three carbohydrates sources, and two fat levels). In both experiments either cornstarch, soybean hulls, or pure cellulose, without or with fat, were incorporated into a barely-soybean meal based diet to alter energy density. Daily diets were isoenergetic (based on NEf), and water supply was .33 L/MJ of NEf. In Exp. 1, the pig type effect on the TD of DM, OM, CP, and the pig type x carbohydrate interactions for the TD of DM, OM, and crude fiber (CF) were significant (P < .05), merely due to a larger difference found for the diet enriched with cellulose. In Exp. 2, the TD and ID evaluated with the marker method were significantly lower (except for the TD of CF) than with the direct method, mainly because Cr recovery was below 100%. Overall, the marker method seems to be superior because the TD means obtained from Cr ratios were closer to the TD obtained from intact pigs. In general, the SICV technique seems to be suitable for long-term digestibility studies to measure the TD and ID in the same pig fed low-or high-fiber diets.     

Milk production and plasma gossypol of cows fed cottonseed and oilseed meals with or without rumen-undegradable protein

Twenty-four multiparous Holstein cows were randomly assigned at calving to treatment diets using a modified split-plot design to determine the effects of protein source on milk production and composition. The treatment diets consisted of an 80:20 combination of corn and alfalfa silages and whole cottonseed at 12% of the dietary dry matter (DM). The treatment diets were formulated to contain 17% crude protein (CP) and 20% acid detergent fiber on a DM basis. One of the following sources of supplemental CP was included in each treatment diet: 1) cottonseed meal, 2) cottonseed meal plus a rumen-undegradable protein (RUP) supplement, 3) soybean meal, and 4) soybean meal plus an RUP supplement. Cows were fed the initial treatment diet for 6 wk and then were switched to the other oilseed meal source but continued to receive the same amount of RUP during the second period of the study. Milk production and composition were not affected by treatment diet. Cows fed treatment diets without RUP supplementation consumed more DM and thus more CP. Supplementation with RUP resulted in greater milk production efficiency per unit of DM consumed. Cows fed treatment diets containing cottonseed meal had higher plasma gossypol concentrations than did cows fed treatment diets containing soybean meal. Plasma gossypol concentrations for all cows in each group were below the recommended upper limit that is considered to be safe. Data suggest that cottonseed meal in the diet can be substituted for soybean meal, resulting in similar milk production and composition.     

Strategies to improve the nutritive value of rice bran in poultry diets. IV. Effects of addition of fish meal and a microbial phytase to duckling diets on bird performance and amino acid digestibility

1. Ducklings were given diets with vegetable protein (VP) and 0 or 600 g rice bran/kg; fish meal (60 g/kg) and a phytase (+, -) were added to the diets (VP + AP). An additional 40 g soyabean meal/kg was added to the diet with rice bran (VP ++). Amino acid digestibility and mineral retention were measured in the lower ileum of ducklings killed at 23 d of age. Acid insoluble ash was used as an inert marker. Trypsin and amylase activities were also measured and weights of the pancreas and small intestine recorded at slaughter. 2. Addition of soyabean meal (VP ++) to the diet with rice bran improved growth rate and food intake compared to the diet without (VP) and gave the same food intake and growth rate as the comparable basal diet (VP) without rice bran. Fish meal improved growth rate on the diets without rice bran and improved food intake on this diet (VP + AP). Rice bran depressed growth rate and food conversion ratio (FCR); protein source affected growth rate, food intake and FCR; phytase increased food intake only. There were several interactions. 3. Determined total amino acid composition of the diets appeared to meet the essential amino acid requirements of ducklings. Rice bran depressed the ileal digestibility of virtually all amino acids and phytase had no direct effect, although there were interactions. Fish meal addition to diets with rice bran improved the apparent digestibility of several essential amino acids as well as that of dry matter and crude protein. 4. Ileal retention of some minerals and tibia ash content were reduced by rice bran. Fish meal and phytase inclusion increased P retention and ash in tibia. 5. Higher intestinal trypsin activity and increased pancreas size were seen in ducklings on diets with rice bran compared to those without. Intestinal amylase activity was reduced in ducklings given rice bran, probably because of its low starch content. 6. The stimulating effect of fish meal on duckling performance was probably caused in part by the improvement in the digestibility of some amino acids. The addition of small amounts of minerals in fish meal may have increased mineral retention. Phytase gave benefits anticipated from our previous work, but also improved lysine and threonine digestibility in diets containing vegetable protein only.     

Growth is compromised in rats fed ozone-treated casein

Modified casein containing few phenylalanine residues and no other aromatic amino acid residues was obtained by ozonolysis of casein. Although 68% of phenylalanine was decomposed by ozonolysis of casein, ozonolysis caused alterations beyond the destruction of aromatic amino acid residues. Nearly the same degree of decomposition of amino acid residues was observed in casein ozonated after predigestion by pepsin. Rats were fed diets containing 8% casein supplemented with methionine and aspartic acid (8C-AA), 8% ozonated casein supplemented with methionine and free amino acids lost by ozonolysis (8OC-AA), 8% casein ozonated after predigestion by pepsin supplemented with methionine and free amino acids lost during preparation (8POC-AA) or 7.6% amino acid mixture. The growth of rats fed the 8OC-AA diet was significantly lower than that of those fed 8C-AA or 7.6AA diets. The growth of rats fed the 8POC-AA diet was comparable to growth of those fed 8OC-AA. The biological values of the 8OC-AA and 8POC-AA were comparable to that of 8C-AA, but true digestibility of 8OC-AA was significantly lower than that of 8C-AA. True digestibility 8POC-AA was significantly improved relative to 8OC-AA, but the growth of rats fed 8POC-AA was not improved relative to that of those fed 8OC-AA. Kidney and cecum weights of rats fed 8OC-AA and 8POC-AA were significantly heavier than those of the 8C-AA-fed group, although histopathological examination of kidneys showed no deterioration compared to that of the 8C-AA-fed group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficacy of phytase in improving the bioavailability of phosphorus in soybean meal and corn-soybean meal diets for pigs

Four experiments involving 225 pigs were conducted to assess the efficacy of a microbial phytase (FINASE, Alko Ltd. Biotechnology, Rajam?ki, Finland) produced by Aspergillus niger in corn-soybean meal or dextrose-cornstarch-soybean meal-based diets. In two experiments with growing-finishing pigs, fortified corn-soybean meal diets were formulated to be adequate (.50%) or inadequate (.40 or .30%) in P during the growing phase followed by adequate (.40%) or inadequate (.30%) P in the finishing phase. Mono-dicalcium phosphate was the source of supplemental P. Half the diets were supplemented with phytase (500 phytase units/g). Rate and efficiency of gain and bone breaking strength were decreased when P-deficient diets were fed. Phytase supplementation of the low-P diets restored growth rate and feed:gain to levels that approached those of pigs fed the adequate-P control diet. Bone strength was partially restored to that of the controls. In two additional experiments, pigs were fed low-P basal diets in which all the dietary P came from soybean meal or a corn-soybean meal blend. Both diets contained .05% available P. Graded levels of monosodium phosphate were added to these diets, up to .15% added P, to establish a standard curve. Phytase was added to the basal diet at 250, 500, or 1,000 units/g. Growth rate and bone strength improved linearly (P < .01) with added monosodium phosphate and with increasing levels of supplemental phytase. Based on estimates of total and available P intakes, the highest level of phytase (1,000 units/g) increased the bioavailability of the P from 25% in the soybean meal diet to 57% in the phytase-supplemented diet, and from 15% in the corn-soybean diet to 43% in the phytase-supplemented diet. Expressed on the basis of the improvement in phytate P availability, this level of phytase converted approximately one-third of the unavailable P to an available form. The results indicate that the phytase was efficacious in improving the bioavailability of phytate P for pigs.     

The feeding value of soybeans fed to rats, chickens, catfish and dairy cattle is not altered by genetic incorporation of glyphosate tolerance

Animal feeding studies were conducted with rats, broiler chickens, catfish and dairy cows as part of a safety assessment program for a soybean variety genetically modified to tolerate in-season application of glyphosate. These studies were designed to compare the feeding value (wholesomeness) of two lines of glyphosate-tolerant soybeans (GTS) to the feeding value of the parental cultivar from which they were derived. Processed GTS meal was incorporated into the diets at the same concentrations as used commercially; diary cows were fed 10 g/100 g cracked soybeans in the diet, a level that is on the high end of what is normally fed commercially. In a separate study, laboratory rats were fed 5 and 10 g unprocessed soybean meal 100 g diet. The study durations were 4 wk (rats and dairy cows), 6 wk (broilers) and 10 wk (catfish). Growth, feed conversion (rats, catfish, broilers), fillet composition (catfish), and breast muscle and fat pad weights (broilers) were compared for animals fed the parental and GTS lines. Milk production, milk composition, rumen fermentation and nitrogen digestibility were also compared for dairy cows. In all studies, measured variables were similar for animals fed both GTS lines and the parental line, indicating that the feeding value of the two GTS lines is comparable to that of the parental line. These studies support detailed compositional analysis of the GTS seeds, which showed no meaningful differences between the parental and GTS lines in the concentrations of important nutrients and antinutrients. They also confirmed the results of other studies that demonstrated the safety of the introduced protein, a bacterial 5-enolpyruvyl-shikimate-3-phosphate synthase from Agrobacterium sp. strain CP4.     

Protein requirements of growing steers limit-fed corn-based diets

In Exp. 1, six steers (254 kg) were used in a 6 x 4 incomplete Latin square to determine the effects of solvent-extracted soybean meal alone or in combination with rumen-protected methionine and lysine on N balance in steers limit-fed a high-corn diet to gain 1.1 kg/d. The basal diet contained (DM basis) 80% rolled corn, 15% alfalfa, and .9% urea (13.9% CP), and 2 or 4% soybean meal replaced corn to give CP concentrations of 14.8 and 15.6%, respectively. Each diet was fed with and without 5 g/d of Smartamine-ML (.75 and 2.0 g of rumen-protected methionine and lysine, respectively). Nitrogen retention increased linearly (P = .09) with level of soybean meal. Rumen-protected methionine and lysine had no effect on N balance. In Exp. 2, seven steers (233 kg) were used in a 7 x 4 incomplete Latin square experiment to investigate optimal levels and sources of CP for steers limit-fed to gain 1 kg/d. Treatments included a negative-control diet (urea; 11.7% CP) and six diets containing either 13.5, 15.4, or 17.2% CP with either solvent-extracted or expeller-processed soybean meal. Diets provided 75, 87.5, 100, or 112.5% of estimated CP requirement for a gain of 1 kg/d. The basal diet contained 83% rolled corn, 15% alfalfa, and .2% urea. Nitrogen retention increased linearly (P = .006) with soybean meal addition, and no differences were observed between CP sources. The CP system underpredicted the protein requirements of limit-fed steers under our conditions.     

Dimethylarsinic acid, a main metabolite of inorganic arsenics, has tumorigenicity and progression effects in the pulmonary tumors of A/J mice

Protective effects of diets containing cruciferous seed meals or hulls against chemically-induced colon tumors were examined in male CF1 mice. When commercial crambe meal, autolyzed crambe meal, crambe hulls, high glucosinolate rapeseed meal, or canola meal were fed as 12% of the diets of mice injected with 1,2-dimethylhydrazine, 25-80% of the animals developed colon tumors. Animals fed a soybean meal control diet had a 100% tumor rate. Data suggest that cruciferous seed meals may contain a number of compounds that can exert protective effects against tumor formation and growth.