Phytase studies in pigs and poultry: effect on protein digestion and energy utilization

Phytase is applied for improving digestibility of phosphorus in pig and poultry diets. Indepen-dently, phytase also improves animal performance. The mechanisms to explain this effect were investigated and quantified. Protein can be complexed with phytate, especially under the acid conditions that occurs in the stomach of animals. Dietary phytase supplementation pre-vents formation of such complexes or, if such complexes are formed, helps to release protein faster and to a larger extent from phytate. Consequently, protein digestibility may increase. This effect was confirmed in a meta-analysis of digestibility experiments, both in poultry and pigs. The higher protein digestibility explains, only in part, the improved performance. In poultry, the apparent metabolizable energy level increased with dietary phytase, mainly as the result of higher protein and fat digestion. Because in literature no effect of phytase on energy digestibility in pigs was shown, post-absorptive energy utilization was investigated. Using indirect calorimetry, no clear effect of phytase could be shown on energy partitioning. Phytase improved, however, energy utilization during the first two weeks post-weaning of ad libitum fed piglets. This may indicate that adaptation of piglets is somewhat facilitated by phytase. In an experiment with restrictedly-fed piglets, three weeks post-weaning, energy digestibility increased with phytase, but not energy metabolizability. A number of observations indicated, however, that energy metabolism of the piglets was affected. Processes that increase or de-crease heat production balance each other out. Phytase increased digestibility of minerals considerably, including the monovalent cations sodium and potassium. Mineral absorption and excretion are, in part, active processes, increasing heat production. Using a mathematical model, this effect was estimated at about 1% of energy requirements for maintenance. A lower energy requirement may result from a reduced produc-tion of endogenous protein. In growing pigs, dietary phytase supplementation decreased gastric mucin production. Possibly, the for-mation of inositol mono-, di- or tri-phosphates may act positively on the growth of animals, but this remains to be confirmed. In conclusion, phytase improved digestibility of amino acids, both in poultry and pigs. It also improved energy metabolizability in poultry. Energy utilization in pigs is probably affected, but the mechanism needs further clarification and quantification

Interaction between Protein, Phytate, and Microbial Phytase. In Vitro Studies

The interaction between protein and phytate was investigated in vitro using proteins extracted from five common feedstuffs and from casein. The appearance of naturally present soluble protein-phytate complexes in the feedstuffs, the formation of complexes at different pHs, and the degradation of these complexes by pepsin and/or phytase were studied. Complexes of soluble proteins and phytate in the extracts appeared in small amounts only, with the possible exception of rice pollards. Most proteins dissolved almost completely at pH 2, but not after addition of phytate. Phytase prevented precipitation of protein with phytate. Pepsin could release protein from a precipitate, but the rate of release was increased by phytase. Protein was released faster from a protein-phytate complex when phytase was added, but phytase did not hydrolyze protein. Protein was released from the complex and degraded when both pepsin and phytase were added. It appears that protein-phytate complexes are mainly formed at low pH, as occurs in the stomach of animals. Phytase prevented the formation of the complexes and aided in dissolving them at a faster rate. This might positively affect protein digestibility in animal

The efficacy of phytase in corn-soybean meal-based diets for laying hens

Microbial phytase hydrolyzes poorly degradable vegetable phytate P in the gastrointestinal tract of poultry; thereby increasing the availability of organic P to an extent that remains to be established. For this purpose, the P equivalency value of phytase in cornsoybean meal layer diets was assessed in three experiments (two short-term absorption studies and one performance trial lasting a complete production period). In the first absorption study, two basal diets containing 30 or 40 g Ca/kg diet were supplemented with either phytase [0, 250, or 500 phytase units (FTU)/kg diet] or with monocalcium phosphate (MCP; 0,0.5, or 1.0 g P/kg diet) and fed to layers from 20 to 24 wk of age. The ileal absorption of Ca and P was measured during the last week. It was shown that 250 FTU/kg diet hydrolyzed an amount of phytate P that was equivalent to 1.3 g P from MCP. At the highest phytase inclusion level (500 FTU/ kg diet), a lower value of equivalency was observed, as P absorption was almost maximal at the lower level of phytase inclusion (250 FTU/kg diet). Phytase hydrolyzed phytate-bound P effectively at both Ca levels, although this degradation was significantly reduced by 12 percentage units at the higher dietary Ca level. The second absorption study, used 0, 250, and 500 FTU phytase/kg diet and O and 1.0 g P/kg diet of MCP. All diets were standardized at 35 g Ca/kg diet. The ileal absorption of Ca and P was determined at 24 and 36 wk of age. These values were significantly reduced in 36-wk-old hens compared to 24-wk-old hens. At 24 wk of age, phytic acid P degradation was significantly improved with increasing levels of phytase up to the maximum inclusion level of 500 FTU/kg diet (maximum phytic acid-P degradation at the end of the small intestine was 66%). In this experiment, the dose of 250 FTU/kg diet was equivalent to 0.8 g MCP-P. In Experiment 3, either phytase or MCP-P was added to a corn-soybean meal layer diet, containing 40 g Ca/kg diet and 3.6 g P/kg diet, at levels of 0, 100, 200, and 300 FTU/kg or levels of 0, 0.3, 0.6, and 0.9 g MCP-P/kg, respectively. Production performance was measured from 18 to 68 wk of age. Diets were consumed ad libitum. Growth, production performances (except kilograms of feed per kilogram of egg), and tibia parameters were significantly improved by dietary supplementation of the negative control diet with either phytase or MCP-P. Growth, egg production, and feed conversion ratio of the hens from the supplemented groups remained good throughout the experiment. No phytase dose effects on the production characteristics or tibia parameters were observed, indicating that the P requirements of the laying hens were met throughout the production period even at the lowest level of supplementation

Effects of emulsified policosanols with different chain lengths on cholesterol metabolism in heterozygous LDL receptor-deficient mice.

Policosanol mixtures have been postulated as promising functional food ingredients to lower serum LDL cholesterol, and increase HDL cholesterol concentrations. We evaluated whether policosanol chain-length [tetracosanol (C24), hexacosanol (C26), octacosanol (C28), triacontanol (C30)] was relevant for its cholesterol lowering effects in heterozygous LDL-receptor deficient mice (LDLr +/-). In addition, effects of individual policosanols varying in chain-length and their respective long-chain fatty acids, and aldehydes on expression of genes involved in lipoprotein metabolism and apoA-I production, were evaluated in vitro. After a run-in period, LDLr +/- mice received experimental western-type diets without policosanols, or similar diets enriched with 30 mg/100 g individual policosanol, or a natural policosanol mixture (Lesstanol60). No significant effects on serum cholesterol concentrations, lipoprotein profiles, or hepatic and small-intestinal mRNA expression of lipoprotein metabolism related genes were found for any of the policosanol diets. In HepG2 and differentiated CaCo-2 cells, policosanols did not change de novo apoA-I protein production. In HepG2 cells, Lesstanol60 elevated gene expression of ABCA1 and HMG CoA synthase-1, however since effects were not observed in vivo, absorption of the responsible components seems to low. We conclude that individual policosanols as well as Lesstanol60 have no potential in reducing CHD risk through effects on serum lipoprotein concentrations

The digestion of grass and alfalfa silages in the forestomachs and intestines of sheep.

Onderzoek naar het verteringsproces van celwandbestanddelen en eiwi

Effect of graded doses and a high dose of microbial phytase on the digestibility of various minerals in weaner pigs

An experiment with 224 weaner pigs (initial BW of 7.8 kg) was conducted to determine the effect of dose of dietary phytase supplementation on apparent fecal digestibility of minerals (P, Ca, Mg, Na, K, and Cu) and on performance. Four blocks, each with 8 pens of 7 pigs, were formed. Eight dietary treatments were applied to each block in the 43-d experiment: supplementation of 0 (basal diet), 100, 250, 500, 750, 1,500, or 15,000 phytase units (FTU) or of 1.5 g of digestible P (dP; monocalcium phosphate; positive control) per kilogram of feed. The basal diet, with corn, barley, soybean meal, and sunflower seed meal as the main components, contained 1.2 g of dP per kilogram of feed. Fresh fecal grab samples were collected in wk 4 and 5 of the experiment. Average daily feed intake, ADG, G:F, and digestibility of all of the minerals increased (P <0.001) with increasing Phytase dose. Digestibility of P increased from 34% in the basal diet to a maximum of 84% in the diet supplemented with 15,000 FTU, generating 1.76 g of dP per kilogram of feed. At this level, 85% of the phytate phosphorus was digested, compared with 15% in the basal diet. Compared with the basal diet, digestibility of the monovalent minerals increased maximally at 15,000 FTU, from 81 to 92% (Na) and from 76 to 86% (K). In conclusion, phytase supplementation up to a level of 15,000 FTU/kg of a dP-deficient diet improved performance of weaner pigs and digestibility of minerals, including monovalent minerals. Up to 85% of the phytate-P was digested. Thus, dietary phytase supplementation beyond present day standards (500 FTU/kg) could further improve mineral use and consequently reduce mineral output to the environment

An in vitro model for caecal proteolytic fermentation potential of ingredients in broilers

Fermentation of protein in the caeca of chickens may lead to the production of potentially detrimental metabolites, which can reduce gut health. A poor precaecal digestion is expected to increase protein fermentation (PF), as more proteins are likely to enter the caeca. It is unknown if the undigested protein that enters the caeca differs in fermentability depending on their ingredient source. In order to predict which feed ingredients increase the risk of PF, an in vitro procedure was developed, which simulates the gastric and enteric digestion, subsequent caecal fermentation. After digestion, amino acids and peptides smaller than 3.5 kD in the soluble fraction were removed by means of dialysis. These amino acids and peptides are assumed to be hydrolysed and absorbed in the small intestine of poultry and therefore not used in the fermentation assay. The remaining soluble and fine digesta fractions were inoculated with caecal microbes. In chicken, the soluble and fine fractions enter the caeca, to be fermented, while insoluble and coarse fractions bypass them. The inoculum was made N-free to ensure bacteria would require the N from the digesta fractions for their growth and activity. The gas production (GP) from the inoculum, therefore, reflected the ability of bacteria to use N from substrates and was an indirect measure for PF. The Maximum GP rate of ingredients averaged 21.3 ± 0.9 ml/h (mean ± SEM) and was in some cases more rapid than the positive control (urea, maximum GP rate = 16.5 ml/h). Only small differences in GP kinetics were found between protein ingredients. Branched-chain fatty acids and ammonia concentrations in the fermentation fluid after 24 hours showed no differences between ingredients. Results indicate that solubilised undigested proteins larger than 3.5 kD are rapidly fermented independent of its source when an equal amount of N is present

The efficacy of phytase in corn-soybean meal-based diets for laying hens

Microbial phytase hydrolyzes poorly degradable vegetable phytate P in the gastrointestinal tract of poultry; thereby increasing the availability of organic P to an extent that remains to be established. For this purpose, the P equivalency value of phytase in cornsoybean meal layer diets was assessed in three experiments (two short-term absorption studies and one performance trial lasting a complete production period). In the first absorption study, two basal diets containing 30 or 40 g Ca/kg diet were supplemented with either phytase [0, 250, or 500 phytase units (FTU)/kg diet] or with monocalcium phosphate (MCP; 0,0.5, or 1.0 g P/kg diet) and fed to layers from 20 to 24 wk of age. The ileal absorption of Ca and P was measured during the last week. It was shown that 250 FTU/kg diet hydrolyzed an amount of phytate P that was equivalent to 1.3 g P from MCP. At the highest phytase inclusion level (500 FTU/ kg diet), a lower value of equivalency was observed, as P absorption was almost maximal at the lower level of phytase inclusion (250 FTU/kg diet). Phytase hydrolyzed phytate-bound P effectively at both Ca levels, although this degradation was significantly reduced by 12 percentage units at the higher dietary Ca level. The second absorption study, used 0, 250, and 500 FTU phytase/kg diet and O and 1.0 g P/kg diet of MCP. All diets were standardized at 35 g Ca/kg diet. The ileal absorption of Ca and P was determined at 24 and 36 wk of age. These values were significantly reduced in 36-wk-old hens compared to 24-wk-old hens. At 24 wk of age, phytic acid P degradation was significantly improved with increasing levels of phytase up to the maximum inclusion level of 500 FTU/kg diet (maximum phytic acid-P degradation at the end of the small intestine was 66%). In this experiment, the dose of 250 FTU/kg diet was equivalent to 0.8 g MCP-P. In Experiment 3, either phytase or MCP-P was added to a corn-soybean meal layer diet, containing 40 g Ca/kg diet and 3.6 g P/kg diet, at levels of 0, 100, 200, and 300 FTU/kg or levels of 0, 0.3, 0.6, and 0.9 g MCP-P/kg, respectively. Production performance was measured from 18 to 68 wk of age. Diets were consumed ad libitum. Growth, production performances (except kilograms of feed per kilogram of egg), and tibia parameters were significantly improved by dietary supplementation of the negative control diet with either phytase or MCP-P. Growth, egg production, and feed conversion ratio of the hens from the supplemented groups remained good throughout the experiment. No phytase dose effects on the production characteristics or tibia parameters were observed, indicating that the P requirements of the laying hens were met throughout the production period even at the lowest level of supplementation

Microbial phytase improves performance, apparent metabolizable energy, and ileal amino acid digestibility of broilers fed a lysine-deficient diet

An experiment was conducted to examine the effects of adding microbial phytase (Natuphos(R)) on the performance in broilers fed a phosphorus-adequate, lysine-deficient diet. A wheat-soybean meal-sorghum-based diet, containing 1.00% lysine and 0.45% nonphytate phosphorus, was supplemented with L-lysine monochloride to provide 1.06, 1.12, or 1.18% lysine or with 125, 250, 375, 500, 750, or 1,000 phytase units (FTU)/kg diet. Each diet was fed to six pens of 10 chicks each from Day 7 to 28 posthatching. Addition of lysine to the lysine-deficient diet linearly increased (P < 0.001) weight gain and gain per feed of broilers. The response in weight gain to added phytase reached a plateau at 500 FTU/kg diet (quadratic effect, P < 0.001). Phytase had no effect on gain per feed to 250 FTU/kg diet and then increased (quadratic effect, P < 0.05) with further additions. Assuming that the observed responses in weight gain and gain per feed to added phytase were due to the release of lysine alone and by solving linear or nonlinear response equations of lysine and phytase levels, the lysine equivalency value was calculated to be 500 FTU phytase/kg diet = 0.074% lysine. Addition of increasing levels of supplemental phytase to the lysine-deficient diet improved (P < 0.001) the digestibilities of nitrogen and all amino acids. Phytase also increased the AME, and the response reached a plateau at 750 FTU/kg diet (quadratic effect, P < 0.001). These results showed that amino acid and energy responses are responsible for the performance improvements observed when phytase was added to a wheat-soybean meal-sorghum-based diet