The sexual maturity of growing pullets can be retarded either by restricting calorie intake or by feeding a diet deficient in one or more essential amino acids, Several methods have been proposed for achieving either of these objectives. In this review the methods have been classified as (a) limiting the birds' time of access to food, (b) quantitative food restriction, (c) the use of low energy diets and (d) dietary protein restriction.Food restriction by limiting the time of access to food has given inconsistent results and is an unsatisfactory technique. Birds quickly learn to eat normal quantities of food in a very short space of time.Quantitative food restriction has been widely used in experiments and is usually applied from about 6 to about 20 weeks of age. The available evidence enables relationships to be established between the degree of food restriction and subsequent body weight and sexual maturity. The effect of rearing treatment on mortality and rate of lay is also examined.The ad libitum feeding of a low-energy growing diet has always resulted in greater rearing food costs. This is because moderate reductions in energy content of the diet are offset by higher food intake. Diets sufficiently low in energy to cause a reduction in calorie intake will involve the purchase and handling of very large proportions of non-nutritive material.The use of protein-deficient diets during the growing period, or from one day of age, offers a suitable means of delaying sexual maturity. The effects of such a treatment are apparently very similar to those of restricted feeding, but there is a lack of suitable comparisons of the alternative methods.

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Mushroom compost was prepared using an enclosed, environmentally controlled composting (ECC) method, designed to promote rapid substrate d e c o n~p o s i t i o n and subsequent establishment of ecological conditions favourable to mushroom culture. Composting aerobically. usually at 54OC early in processing followed by 47OC for the majority of processing. produced a compost ready for spawning in 6-8 days. Final c o m p o s t had a bulk density of 486 kg/ni.i (range 440-510 kg/ni3) at 70.4% moisture (range 66-75%) and produced average fresh mushroom yields of 19.4 kg per bed m2 (range 22.7-17.3/m2), or 0.66 kg per kg dry compost, in a 3 flush cropping cycle. Disease, or growth of competitive fungi, was not observed. Composting odours were greatly reduced compared to traditional methods. The processing control and uniformity of the ECC method offer much potential for detailed investigation into compost production and ecological and chemical factors in mushrooni nutrition.

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