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1. The amino acid composition of the whole body protein of 28- and 56-day-old turkeys is reported. 2. There were some differences between the two ages; these could largely be reconciled by considering the likely differences in the proportion of feather protein. 3. The results were compared with similar values for the chicken and goose; overall there is a striking similarity, both in absolute concentrations and relative proportions of amino acids.

Glucosinolates were removed from whole rapeseed by a hot-water extraction procedure or depleted by heat treatment. When laying hens were maintained for three months on diets containing about 300 g kg-1 of these rapeseed cakes, the incidence of liver haemorrhages detected at post mortem examination was similar to that in birds maintained on 300 g kg-1 commercial rapeseed meal and significantly greater than in control birds fed soya-based diets. The effectiveness of glucosinolate extraction or depletion was determined by chemical analysis and by histological examination of the thyroid glands. Histologically the haemorrhages were similar after feeding extracted and commercial rapeseed meals. Diets containing mixtures of nitriles and glucosinolates severely depressed food intake and egg production but did not cause a greater incidence of haemorrhages than the other rapeseed products tested. Mortality from causes other than liver haemorrhage was higher with the diets containing rapeseed and this suggests that rapeseed has a more generalised effect on the body's defence mechanisms. These observations suggest that other factors in rapeseed meal, alone or acting with glucosinolates, may be responsible for inducing liver haemorrhages in laying hens.

The occurrence of liver haemorrhages was compared when diets containing 30 or 40 per cent rapeseed meal (RSM) or 30 per cent soybean meal (SBM), with and without experimental additives, were fed to in-lay hens of a commercial egg-producing strain for 12 weeks. The incidence of haemorrhages was significantly greater when the birds were maintained on the basal (unsupplemented) RSM diet than on the equivalent SBM diet. Haemorrhages were either small and infrequent, minute and multiple as in peliosis hepatis, or large enough to rupture the liver capsule. They might be recent or old and encapsulated, sometimes both varieties affecting the same specimen, and they occurred in any part of the liver. Histologically, hepatocyte necrosis and reticulin derangement were not detected in livers without gross haemorrhages and even in those with haemorrhages these abnormalities were only seen closely adjacent to haemorrhages or to foci of eosinophilic fibrinoid. In some instances there was sinusoidal ectasia. Separate additions of 50 g dried skimmed milk powder, 0.5 g zinc oxide, 0.25 g ferrous sulphate or 2.0 mg selenium (as sodium selenite) kg-1 to the basal RSM diet did not significantly modify the incidence of haemorrhage. Ferrous sulphate slightly reduced goitrogenicity. Supplements of 2.2 mg menadione and 1.0 g sodium phenobarbital kg-1 RSM diet induced slight reductions in the number of cases of liver haemorrhage or their severity, indicating that the multifunction oxidase system may be involved in rapeseed hepatotoxicity. The addition of 0.5 g methimazole kg-1 to the basal SBM diet induced severe colloid goitre but did not induce liver haemorrhage. Both thiouracil (0.5 g kg-1 diet) and beta-aminopropionitrile (0.5 g and 2.5 g kg-1 diet) when added to the basal SBM diet induced liver haemorrhages which did not differ in incidence or histological appearance from those induced by RSM. Hyperplastic goitre was caused by thiouracil. Intrahepatic cholestasis induced by sodium taurolithocholate, bilirubin and alpha-naphthylisothiocyanate and extrahepatic cholestasis induced by bile duct ligation resulted in hepatocyte necrosis but not gross liver haemorrhages. Spontaneous deaths due to conditions other than liver haemorrhages were significantly more numerous in RSM-fed than SBM-fed hens.(ABSTRACT TRUNCATED AT 400 WORDS)