The determination of dry matter in silages by distillation with toluene gives satisfactory results when an allowance is made for volatiles present in the aqueous distillate. A simple correction procedure, involving a single titration of the distillate, has been developed, and the method is considered suitable for routine purposes.

DEWAR et a1.-HEMICELLULOSE HYDROLYSIS I N SILAGE 41 1pinned discs was much the finer, it is noteworthy that in both cases discontinuities occur a t approximately the sizes mentioned above, where the nature of the particles changes. Thus, although it is possible that some air-classified fractions may exhibit a log normal size distribution, there is little to be gained by plotting results for samples covering a wide particle size range in this way.The production of reducing sugars, resulting from the incubation of a hemicellulose prepared from Lolium pevenne (perennial ryegrass), with enzymes extracted from Loliuin perenne, Lolium italicnnz (Italian ryegrass) and Dactylis glomevata (cocksfoot) was measured over a range of temperature, pH and time. Each of the three enzymes had an optimum pH of 6 but the optimum temperature ranged from 30" to 43". There was a significant interaction between high temperature and low pH, both tending to suppress enzyme activity. Appreciable amounts of reducing sugars were also produced from hemicelluloses by acid hydrolysis (pH 4) over a go-day period.Attempts to grow a number of strains of lactic acid bacteria using hemicellulose as an energy source were unsuccessful. The importance of these findings on the ensilage process is discussed.

The apparent digestibility of a diet can be calculated from the amounts of food eaten and excreta voided. This ‘total collection’ method is laborious because it requires a period lasting several days. It can be circumvented by the inclusion in the diet of a suitable reference substance (Kotb & Luckey, 1972). From the concentration of the reference substance (marker) in the diet and in the droppings, apparent dry-matter digestibility can be calculated.

The effects of high dietary concentrations of zinc oxide on chicks and hens were studied in four experiments. Chicks given 2000, 4000 or 6000 mg zinc/kg diet from 2 to 6 weeks of age grew poorly, many showing gizzard erosion and lesions of the exocrine pancreas. Dissecting aneurysms occurred in a few birds receiving 6000 mg zinc/kg. Pancreatic lesions were found in chicks maintained on 1000, 2000 or 4000 mg zinc/kg from 0 to 4 weeks and the two higher concentrations reduced body weight and increased the incidence of gizzard erosion. Histologically, gizzard lesions varied from excessive desquamation of epithelial cells, heterophils and erythrocytes into an abnormally spongiform koilin, to erosion of koilin, glands and pits. Pancreatic lesions could be detected only microscopically and consisted of dilation of the acinar lumina, cytoplasmic vacuolation, cytoplasmic globule formation and necrosis of the exocrine cells with interparenchymal fibrosis. Similar lesions of the gizzard and pancreas were found in hens after they had received 10000 or 20000 mg zinc/kg diet for only 4 d. Hens given 10000 mg zinc/kg for 4 d followed by a normal zinc intake for 28 d had normal gizzards and pancreata.