1. The effects of different dietary concentrations of calcium (24 to 56-9 g/kg) and phosphorus (4-5 to 14-2 g/kg) on production and some aspects of metabolism were studied in laying hens. 2. Treatments did not affect egg numbers, food consumption, conversion efficiency of food to egg, bodyweight gain or mortality. 3. Increasing dietary calcium (Ca) significantly increased plasma Ca and inorganic phosphorus (P), breaking strength at the radius and egg specific gravity and significantly decreased plasma alkaline phosphatase and egg weight. 4. Increasing dietary phosphorus increased plasma P and decreased egg specific gravity significantly. 5. Plasma Ca, P and alkaline phosphatase and radius breaking strength were suitable indices of the Ca status of the hens.

No abstract

The nutritional potential of an ancient food grain, A. edulis, was appraised by chemical analyses and in two feeding experiments with chickens and rats. The outstanding feature of the grain was its very favourable essential amino acid composition. The sample of grain used in these experiments contained 0.94% lysine, 0.66% methionine plus cystine, 1.54% arginine and 0.59% threonine in the dry matter. Raw and heat-treated grain contained 13.1 6 and 14.54 MJ kg-1 dry matter of nitrogen-corrected metabolizable energy. The raw grain contained a heat-labile toxin that affected hepatic function and depressed growth. Heat-treated A. edulis supported both chicken and rat performance, which approached or equalled that on a control diet. The heat-treated grain replaced over 70% of the grain and protein concentrate components of the control diet.

The grains of three sorghum varieties varying in tannin content were fed to growing chickens as 70 per cent of their diet in three experiments. Tannic acid per se was also fed as 0.1 per cent and 1.0 per cent of the grain component in one of these experiments. There was a marked growth retardation as the tannin content of the grain component rose. This retardation, whether produced by an increase in plant tannin or the addition of tannic acid per se, could only be partially alleviated by supplementation with high levels of methionine and choline. Raising the tannic acid or plant tannin level of a ration appears to have two detrimental effectsdepressing feed intake and a toxic effect. Addition of tannic acid significantly depressed liver fat content and testis weight. Additional methionine plus choline supplementation prevented the liver fat depression but did not prevent the reduction in testis weight.

The significance of fat accumulation during physiological development of layers was studied using White Leghorn X Australorp pullets from 12 weeks of age. 2. Liver fat, carcass fat, liver weight and body weight increased markedly at the onset of sexual maturity. 3. Within the liver, the protein to DNA ratio did not alter significantly during development; glycogen was not consistently depleted by egg production. 4. Liver fat content was significantly correlated with carcass fat, liver weight and DNA concentration, and plasma total lipid and cholesterol, independent of stage of development; with body weight, liver protein, moisture, and protein to DNA ratio, excluding the period prior to commencement of sexual maturation; and with plasma phospholipid during lay. 5. Obesity was a feature of faster growing fowls which matured earlier, consumed more, utilised food less efficiently for egg production and produced fewer saleable eggs.