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.     

Nutritional utilization by rats of chickpea (Cicer arietinum) meal and its isolated globulin proteins is poorer than that of defatted soybean or lactalbumin

The effects on performance, digestibility, N utilization and plasma amino acid concentrations of dietary chickpea (Cicer arietinum, var. Kabuli) seed meal, globulin proteins or buffer-insoluble residue [starch + non-starch polysaccharides (NSP) + lignin] were studied in growing rats. Chickpea meal, defatted soybean meal, chickpea globulins and lactalbumin were each incorporated into diets as the sole source of dietary protein (100 g/kg). In addition, chickpea insoluble residue was included in a control diet in the same proportion found in the chickpea meal. Rats were killed while under halothane anesthesia after 10 d of consuming the diets, and ileal contents were washed out and freeze-dried for digestibility measurements. Weight gains and gain:feed ratios of rats fed chickpea diets for 10 d did not differ from those of rats fed defatted soybean but were significantly lower than those of rats given the control (lactalbumin) diet. However, ileal and fecal N digestibilities and N retention by rats fed the chickpea diet were significantly lower than those obtained with the lactalbumin or soybean diet. The inclusion of both chickpea meal or its globulin proteins in the diet significantly increased the amount of N excreted, primarily as urea, through the urine. However, although ileal N digestibility values for chickpea meal were significantly lower, those for its constituent globulins did not differ from control values. Urea levels in plasma in rats fed diets containing chickpea meal, globulins or soybean meal were significantly higher than in those fed lactalbumin. Furthermore, the concentrations of glycine, phenylalanine, histidine, arginine and ornithine in the plasma of rats fed chickpea meal, its globulins or defatted soybean were significantly higher, whereas those of threonine, leucine, lysine and tryptophan were significantly lower than lactalbumin-fed controls. The chickpea insoluble residue had no adverse effects on performance or N utilization by rats. We conclude that the low nutritional value of chickpea meal is likely to be due mainly to adverse effects of its globulin proteins on growth and N metabolism rather than to the action of any known antinutritional factor present in the diet.     

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.     

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.     

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.     

The effects of excessive amounts of protein on lysine utilization in growing pigs

Two experiments were conducted to investigate whether the utilization of lysine in growing pigs is affected by the level of excess protein in the diet. Nine lysine-deficient diets containing 100, 200 or 300 g crude protein/kg and between 1.2 and 6.8 g ileal digestible lysine/kg were prepared. In the first experiment the apparent ileal digestibility of lysine in three of the nine diets was determined using pigs with simple T-cannulas and Cr2O3 as an indigestible marker. Ileal digestibility of lysine in the other diets was calculated by interpolation. In the second experiment N retention, as a measure of lysine utilization, was determined in all nine diets using growing pigs over the weight range 30-50 kg. The effect of excess protein on lysine utilization was assessed by comparing the regression of N retention v. lysine (ileal digestible) intake at the three levels of protein. Increasing ileal digestible lysine in the diets resulted in a linear increase in N retention with all three protein levels and there was no significant difference amongst the three regressions, indicating that lysine utilization was not affected by the level of protein. Therefore, all data were pooled together to calculate a single regression for all treatments. An increase of 1.0 g ileal digestible lysine led to an increase of 1.43 g N or 8.96 g protein (N x 6.25) retained. Assuming a lysine concentration in the retained body protein of 65-72 mg/g, lysine was utilized with an efficiency of 0.58-0.65.     

The action of retinoic acid on psoriatic skin

15 trials were carried out with 600 young pigs receiving a type of liquid skim milk diet from the 12th to the 28th day of age. 0% to 75% of the proportion of dietary milk were replaced by wheat and fish meal. The experimental rations used in the trial exhibited a high digestibility of crude nutrients. No transitional feeding period was necessary between the feeding of the milk diet and that of the substituted ration. Whole meal from crude wheat was found to be equivalent in quality to whole meal made from cooked wheat. A liquid feed in which about 50% of the dietary milk is replaced by wheat and fish meal is well suited for being fed to young pigs when these are between 13 and 28 days of age.     

High dietary calcium level decreases colonic phytate degradation in pigs fed a rapeseed diet

The degradation of phytate (inositol hexaphosphate) in rapeseed meal diet not containing phytase activity was studied in 15 growing ileum-fistulated pigs. Stomach and small intestinal degradation and total gastrointestinal degradation were compared. The effect of addition of calcium carbonate to the rapeseed meal diet at two levels (9.2 and 18.5 g/kg diet) was investigated. A commercial barley-wheat-soybean diet with intrinsic phytase activity was used as reference. Phytate and its hydrolysis products in diets, ileal digesta and feces were determined by HPLC ion-pair chromatography. Hydrolysis of phytate in the stomach and small intestine was 35-45% in pigs fed the rapeseed meal diet independent of calcium addition, and 65% in pigs fed the reference diet. Total gastrointestinal degradation of phytate in pigs fed the rapeseed diet was 97, 77 and 42% (P < 0.001) when calcium intakes were 4.5, 9.9 and 15 g/d, respectively; total gastrointestinal degradation was 72% in pigs fed the reference diet. The intestinal phytate degradation pattern, when rapeseed diet was fed, indicated the activity of an unspecific phosphatase, whereas that of the reference diet indicated intrinsic dietary phytase activity. We conclude that dietary supplementation of calcium carbonate decreases the phytate degradation in the colon of pigs, but not in the stomach and small intestine.     

Apparent ileal digestibilities of amino acids in newly weaned pigs fed diets with protease-treated soybean meal

Apparent ileal digestibilities of amino acids were determined in pigs fed cornstarch-based diets with untreated or protease-treated soybean meal as the protein source. Sixteen pigs were fitted with a modified post valve T-cecum cannula on d 14, 15, and 16 after birth and then returned to their sows until d 20 when they were weaned. Twelve of the pigs were selected for the study, which was conducted according to a two-period balanced change-over design. Treatments consisted of soybean meal that was 1) untreated (SBM), 2) processed by incubation (1:2 wt/vol distilled water adjusted to pH 4.5, for 16 h at 50 degrees C; CI-SBM), 3) sprayed with protease (supplied at 1 microL/g of soybean meal; PS-SBM), and 4) processed by incubation, as for CI-SBM, with protease in the water at the rate of 1 microL/g of soybean meal (PI-SBM). Each period consisted of 5 d of adaptation to diets followed by three 8-h collection periods (total of 24 h) that alternated with 8-h periods in which digesta were not collected. Apparent CP digestibilities were similar (P > .05) at 70.4, 72.4, 65.2, and 70.3% for the SBM, CI-SBM, PS-SBM, and PI-SBM diets, respectively. Corresponding amino acid digestibilities were also similar (P > .05), ranging from 62.5, 67.5, 57.9, and 65.0% for alanine to 83.5, 83.4, 78.7, and 84.7% for arginine. Apparent digestibilities were less (P < .05) for Period 1 (on d 7 after weaning) than for Period 2 (on d 16 after weaning). In conclusion, protease treatment of soybean meal had no effect on ileal digestibilities of CP and amino acids in newly weaned pigs.     

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

The digestibility and bioavailability of amino acids (AA) in meat and bone meals (MBM) may vary greatly due to different processing conditions. In the present study, two experiments were conducted to evaluate formulation of diets containing high or low quality MBM on a total AA basis vs a digestible or bioavailable AA basis compared to a corn-soybean meal control diet. Lysine, methionine, and cystine digestibilities (precision-fed cecectomized rooster assay) were 92, 91, and 71%, respectively, for high quality MBM and were 71, 83, and 31%, respectively, for the low quality MBM. Bioavailability values (slope-ratio chick growth assay) for TSAA in the two MBM were approximately 15 percentage units lower than the digestibility values. Male crossbred chicks were fed a 20% CP corn-SBM diet or corn-SBM diets containing 10 or 20% high or low quality MBM that were formulated to be equal in total, digestible, or bioavailable AA to the corn-SBM diet. All diets contained 3,200 kcal of TMEn/kg, 1.4% Ca, and 0.7% nonphytate P and were fed to chicks from 8 to 22 d posthatching. Growth performance of chicks fed 10 or 20% high or low quality MBM on a total AA basis was lower (P < 0.05) than that of chicks fed the corn-SBM diet. Growth of chicks fed 10% low quality MBM or 10 or 20% high quality MBM on a digestible or bioavailable basis was equivalent to that of chicks fed the corn-SBM diet; however, dietary inclusion of 20% low quality MBM depressed growth (P < 0.05) even on a digestible or bioavailable AA basis. Further supplementation of the latter diet with additional AA yielded growth that was similar to the corn-SBM control diet. The results indicated that formulation of diets containing MBM on a digestible or bioavailable AA basis is superior to formulation on a total AA basis. However, feeding high levels of a low quality MBM may require additional AA supplementation to obtain maximum chick growth.     

Effect of dietary neutral detergent fiber on ileal digestibility and portal flux of nitrogen and amino acids and on nitrogen utilization in growing pigs

Two experiments were conducted to determine the effects of dietary NDF on apparent ileal and fecal digestibility and portal flux of nitrogen (N) and amino acids, and on N retention in growing pigs. In four equal portions (at 0600, 1200, 1800, and 2400) barrows on Treatment B received a basal diet, based on casein, cornstarch, and dextrose, at a feeding level of 2.6 times energy for maintenance. Barrows on Treatment B+NDF received an additional amount of 15% (wt/wt) of purified wheat bran NDF (pNDF). In Exp. 1, four ileally cannulated barrows (40 to 75 kg) were used in a crossover arrangement comprising two treatments and three periods. The addition of pNDF decreased ileal N digestibility from 94.1 to 88.9% (P < .001), whereas ileal digestibility of most amino acids was 2 to 5.5 percentage units lower (P < .001). Utilization of ileally digested N increased from 64 to 72% with the addition of pNDF, presumably because of the contribution of pNDF to the energy supply. In Exp. 2, three barrows (30 to 54 kg) fitted with catheters in the portal vein and the mesenteric vein and artery were used in a crossover arrangement comprising two treatments and five periods. Portal absorption of nutrients was derived by multiplying the porto-arterial plasma concentration differences by portal vein plasma flow. The pNDF did not significantly affect the absorption of ileally digested amino acids and the portal flux of ammonia and urea. The results showed that addition of NDF reduced amino acid digestibility, but not the portal flux of digested amino acids, and NDF energy presumably improved utilization of ileally digested amino acids.     

Ruminal degradation, amino acid composition, and estimated intestinal digestibilities of four protein supplements

Blood meal, canola meal, corn gluten meal, and menhaden fish meal were weighed into dacron bags for incubation in the rumens of two ruminally cannulated Holstein cows on 3 d for 0, 3, 6, 12, 18, and 24 h. Both the original feeds and the residues remaining after 12 h were analyzed for amino acid (AA) content. Canola meal was degraded the most extensively in the rumen, and blood meal was degraded the least extensively. Intestinal digestibilities estimated using an enzymatic in vitro technique were all high; canola meal was estimated to have the lowest intestinal digestibility, and corn gluten meal was estimated to have the highest intestinal digestibility. The AA profile of the 12-h residues differed only slightly from the AA profile of the original protein supplements. A comparison of the AA profiles of feed residues with milk protein showed that isoleucine was the first-limiting AA in blood meal, canola meal, and fish meal, and lysine was the first-limiting AA in corn gluten meal. Although canola meal was extensively degraded in the rumen, its 12-h residue still provided an estimated AA profile to the intestinal tract that was closest to the AA profile of milk protein. Blood meal and corn gluten meal are good sources of ruminally undegradable protein but are deficient in some AA and should probably be fed only in combination with other protein sources that complement their AA profiles.     

Supplementation of milk replacers containing soy protein with threonine, methionine, and lysine in the diets of calves

An attempt was made to improve the protein quality supplied in milk replacers containing soy protein by supplementing Thr, Met, and Lys to the milk replacers fed to calves. Six Holstein x indigenous male calves were fitted with single cannulas at the end of the ileum. Calves were fed milk replacers containing skim milk (86%) and whey (14%) proteins or skim (43%), whey (14%), and soy (43%) proteins either with or without amino acid (AA) supplementation according to a double 3 x 3 Latin square design. Average daily gain, N retention, and ileal digestibilities of dry matter, N, and AA were significantly higher for calves fed the milk replacer containing skim milk protein than for calves fed the milk replacer containing soy protein. Average daily gain, N retention, and ileal digestibilities of dry matter, N, and AA were significantly higher for calves fed the milk replacer containing soy protein plus AA supplementation than for calves fed the milk replacer containing the soy protein without AA supplementation. Therefore, supplementation of a milk replacer containing the soy protein without AA supplementation. Therefore, supplementation of a milk replacer containing soy protein with limiting AA that correspond to the AA found in milk protein can considerably improve the protein quality of that milk replacer for the preruminant calf.     

Effects of species raw material source, ash content, and processing temperature on amino acid digestibility of animal by-product meals by cecectomized roosters and ileally cannulated dogs

We conducted experiments to determine amino acid (AA) digestibility of nine animal by-product meals using precision-fed cecectomized roosters and ileally cannulated dogs. The products initially evaluated in roosters were meat and bone meals (MBM) containing 24 or 34% ash, poultry by-product meals (PBP) containing 7 or 16% ash, lamb meals (LM) containing 15 or 24% ash, a LM analog containing a mixture of LM and turkey meal, and two MBM processed at either a low or high temperature. The MBM and PBP differing in ash, low-ash LM, and low-temperature MBM then were incorporated into extruded dry dog foods and evaluated in cecectomized roosters and ileally cannulated dogs. True digestibility of total AA in roosters averaged 76% for the nine meals fed alone, with the low-temperature MBM being highest at 84% and the low-ash LM being lowest at 66% (P < .05). No consistent differences in rooster AA digestibility were observed between pairs of meals differing in ash content. Digestibilities of AA were higher in the low-temperature MBM than in the high-temperature MBM. Differences in rooster AA digestibility values among the six extruded dog foods containing selected animal meals were similar to those observed when the animal meals were fed alone. The ileally cannulated dog assay yielded results for AA digestibilities that were highly correlated (r = .87 to .92) with those of the rooster assay, whereby the high-ash MBM and low-temperature MBM foods had the highest mean AA digestibility at 82% and the low-ash LM food had the lowest mean AA digestibility at 62% (P < .05). Again, no consistent differences in AA digestibilities for dogs were observed between pairs of dog foods containing MBM or PBP differing in ash content. Results of this study indicated that processing temperature influenced AA digestibility of MBM, but species raw material source and ash content had no consistent effect on AA digestibility. Results also indicated that the precision-fed cecectomized rooster assay could be used to predict differences in AA digestibility among animal by-product meals for dogs.     

True digestibility of amino acids and protein in pigs with 13C as a label to determine endogenous amino acid excretion

The objective of this study was to determine whether differential labeling of 13C occurs in pigs fed diets with different 13C abundances and, if so, to use 13C as a label to determine true amino acid digestibility. Forty-eight pigs averaging 10.5 kg BW were fed dietary treatments consisting of a corn-corn gluten meal-crystalline amino acid diet (C-CGM) and a wheat-soybean meal diet (W-SBM). The 13C abundance of the amino acid fraction (AAF) of the C-CGM and W-SBM diets averaged delta 13C -14.19 and -26.36/1000, respectively. Three pigs/treatment group were killed when groups averaged 10.5 (initial), 22.9, and 46.6 kg BW, and AAF of organs were analyzed for 13C abundance. Carbon 13 in empty body AAF increased (-18.14, -13.98, and -12.66/1000) with increasing body weight in pigs fed the C-CGM diet and decreased (-18.06, -22.78, and -24.76/1000) in pigs fed the W-SBM diet. Liver, small intestine, and longissimus muscle tissues showed similar trends. Each tissue had dietary treatment effects (P < .001) and dietary treatment x weight group (P < .001) interactions. Ten pigs averaging 55.0 kg BW from each treatment group were assigned to metabolism cages and fed at 0700 and 1900. Six of these pigs from each treatment group were implanted with T-cannulas in the ileum and given a 17-d recovery period. At 1900 on d 0 of the collection phase, pigs were switched to the opposite diet that contained chromic oxide.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Roost selection in the pipistrelle bat, Pipistrellus pipistrellus (Chiroptera: Vespertilionidae), in northeast Scotland

The aim of the present study was to determine the composition of amino acids that were truly digestible in the ileum. Several bovine milk products and two soy protein products were tested using the newly developed enzymatically hydrolyzed casein-ultrafiltration (UF) method. This method provides a novel approach for determining endogenous flows of amino acids at the terminal ileum, which are required for correcting apparent ileal digestibility values to true digestibility values. Digestibility was determined by sampling digesta of Sprague-Dawley male rats at the end of the small intestine (ileum). Chromic oxide was used as an indigestible marker. The traditional protein-free method for determining endogenous losses of amino acids was also used for comparison with the enzymatically hydrolyzed casein-UF method. Flows of endogenous amino acids at the terminal ileum of the rat following peptide alimentation were generally higher (1.8-fold) than those determined after a protein-free diet was fed. Compared with values for true amino acid digestibility, apparent values underestimated digestibility by 2 to 30%. True amino acid digestibility was high (79 to 102%) for all of the protein sources. The digestible amounts of methionine and lysine were 2 and 1.3 times higher, respectively, in dairy proteins than in soy proteins. The enzymatically hydrolyzed casein-UF method provides a physiological estimate of endogenous amino acid flow and appeared to be an appropriate method for correcting apparent digestibility values to true digestibility values. The data for true ileal digestibility of amino acids obtained using this technique demonstrated the high quality of bovine milk proteins.     

Protein density and its influence on metabolite concentration and nitrogen retention by Holstein cows in late gestation

Multiparous Holstein cows in late gestation were used in a completely randomized design to test the effects of prepartum protein supply on prepartum N balance, blood metabolite and hormone concentrations, and postpartum intake and milk production. Cows were assigned to one of three isocaloric diets that differed in amount of total dietary crude protein (CP) (10.6, 12.7, or 14.5% of dry matter) but not in CP degradability or solubility. All diets contained the following ingredients: corn silage, chopped grass hay, ground corn, soybean meal, expeller soybean meal, minerals, and vitamins. Following parturition, all cows were offered a similar diet. Nitrogen balance was measured on d 12 to 7 prior to the expected calving date. Cows were bled on d 5 prior to the expected calving date from just prior to feeding to 8 h postfeeding. As dietary CP increased, plasma glucose concentrations increased linearly, but no change was detected in plasma nonesterified fatty acids or serum insulin concentrations. Nitrogen intake, apparent and true digestibilities, fecal and urinary concentration of and N balance increased as the concentration of dietary protein increased. The efficiency of absorbed protein utilization decreased as protein intake increased. No change in postpartum intake or milk production was observed. An increase in N retention in late gestation cows that were in positive N balance did not increase postpartum milk production.     

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 efficacy of Aspergillus niger phytase in rendering phytate phosphorus available for absorption in pigs is influenced by pig physiological status

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, 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 or 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.