Effects of phyto-oestrogens on veal calf prostate histology.
In veal calf production plant-based proteins are frequently included in milk replacer fed to the animals. Since soy products, which are mostly used, are known for their high levels of phyto-oestrogens, the effects of these feeds on the veal calf prostate were examined. Goal was to determine whether these compounds could interfere with histological screening for oestrogenic growth promoters. In a feeding experiment, four groups of veal calves fed plant-based protein-supplemented milk replacer (PBM), containing 5% soy concentrate, 5% soy isolate, 5% wheat gluten and 2% potato protein, for 4 weeks were compared to animals fed dairy-based control feed (DBM); animals treated with estradiol benzoate, diethylstilbestrol and ethinylestradiol served as positive controls. Daidzein and genistein levels measured in feed and urine showed high levels of genistein and daidzein in the soy isolate and soy concentrate supplemented feeds. Genistein and daidzein were also found in the urine of the animals that were fed these feeds. Haematoxylin-eosin-stained prostate sections of PBM-fed animals showed slight hyperplasia and some dilated tubules as compared to the DBM-fed group, but no metaplasia, which is used for screening for oestrogenic hormones. The positive controls showed extensive squamous metaplasia. Immunohistochemical staining for cytokeratin 5 (using RCK 103 monoclonal antibody) in basal cells showed a normal staining pattern of basal cells in the DBM-fed calves and extensive basal cell proliferation and squamous metaplasia in the oestrogen-treated positive control animals. PBM-fed calves showed no increase of basal cell staining but showed elongations of the basal cells in most animals, sometimes resulting in circular figures. It is concluded that the feeds examined in this study did not interfere with histological screening for oestrogens in male veal calves.