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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SummaryThe crystal and molecular structure of cyclopentadienyltin(I1) chloride has been determined from three-dimensional X-ray data. The crystals are orthorhombic, space group Pc~~Tz. The unit cell, of dimensions a = 5.711(5), b = 6.225(5), c = 17.24(2) a, contains four molecules. The structure has been refined by full matrix least squares techniques to a final R value of 0.083 for 717 independent reflections. In the crystal unsymmetrical tin-chlorine bridges are present between the units of &H,SnCl.It is suggested that in cyclopentadienyltin(I1) compounds the cyclopentadienyl group occupies more than one coordination site as a result of the donation of x electron density from the cyclopentadienyl ring into an empty acceptor orbital of the tin atom having 7r symmetry.