Techniques have becn developed to produce microbial phytase for addition to diets for simple-stomached animals, with the aim to improve phosphorus availability from phytate-P in plant sources. The activity of the crude microbial phytase showed pH optima a t pH 5.5 and 2.5. The enzyme was able to degrade phytate in vitro in soya-bean meal, maize and a liquid compound feed for pigs. When microbial phytase was added to low-P diets for broilers the availability of P increased to over 60% and the amount of P in the droppings decreased by 50%. The growth rate and feed conversion ratio on the low-P diets containing microbial phytase were comparable to or even better than those obtained on control diets. Addition of microbial phytase to diets for growing pigs increased the apparent absorbability of P by 24%. The amount of P in the faeces was 35% lower.Phosphorus availability : Microbial phytase: Broilers: Pigs Feeds for poultry and pigs mainly contain ingredients of plant origin. About two-thirds of the phosphorus in these products is present as phytate-P which has a low availability in simple-stomached animals. It therefore contributes to the P pollution problems in areas having an intensive livestock production such as The Netherlands.Many fungi, bacteria and yeasts produce the enzyme phytase which is needed for the hydrolysis of phytate to inositol and inorganic phosphate. Nelson et ul. (1968) were the first to add phytase, produced by a culture of Aspergillusficuum, to liquid soya-bean meal. The feed was incubated for 2-24 h at 50". After drying, it was fed to 1-d-old chicks, Thc birds showed a considerable increase in bone ash percentage over controls receiving no inorganic phosphate. In a second experiment (Nelson rt ul.

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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 corn-soybean 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 0 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.

The nutritive value of meat and bone meals (MBM) was assessed for broilers. The MBM was produced according to the revised (pressure) processing system ordered by the European Union (EC 96/449). Three batches of MBM from cattle (MBMcattle) and three from pigs (MBMpig) with different ash contents (224, 306, 387, and 209,293, 430 g/kg, respectively) were tested for digestibility at a 10% inclusion level. The MBMcattle and MBMpig with the lowest ash (224 and 209 g/kg, respectively) were tested also at 20% inclusion. A basal diet (corn-soybean meal) was used as a control. Two-week-old broiler chickens were used in four replicates per treatment (14 to 32 d of age). The AMEn of MBM was high (10.51 to 13.04 MJ/kg DM). Species origin had no significant effect, whereas more ash and a higher inclusion level decreased the AMEn. The factors investigated showed no significant effect on the excretal digestibility of CP or on total AA. Excretal digestibility of total amino acids (AA) ranged from 60 to 65%. The ileal digestibility of CP and AA of MBMpig with 209 g/kg ash was also tested at 10 and 20% inclusion. Excretal digestibility was significantly higher than ileal digestibility of CP (63.8 and 55.8%, respectively) and total AA (60.9 and 56.2%, respectively). The 20% inclusion level resulted in a lower digestibility for both methods. The digestibility of CP was measured by four different in vitro techniques, based on pepsin digestibility. The data showed a large variation and did not correlate at all with the in vivo digestibility values.

Techniques have been developed to produce microbial phytase for addition to diets for simple-stomached animals, with the aim to improve phosphorus availability from phytate-P in plant sources. The activityof the crude microbial phytase showed pH optima at pH 5-5 and 2·5. The enzyme was able to degradephytate in vitro in soya-bean meal, maize and a liquid compound feed for pigs. When microbial phytasewas added to low-P diets for broilers the availability of P increased to over 60 % and the amount of Pin the droppings decreased by 50%. The growth rate and feed conversion ratio on the low-P dietscontaining microbial phytase were comparable to or even better than those obtained on control diets.Addition of microbial phytase to diets for growing pigs increased the apparent absorbability of P by24%. The amount of P in the faeces was 35% lower.