A study of the nutritive value of toprina G in the diet of two hybrid strains of caged laying hens

An experiment is reported in which the hydrocarbon‐grown yeast Toprina G was used at levels of 0, 20, 40, 60, 80, 100 and 120 g kg −1 of diet to replace mainly soybean meal in a fishmeal‐free control diet fed to two lightweight hybrid strains of caged layers. The Toprina G had a very low Se content (14 μg kg‐ −1 ) and a high Mn content (325 mg kg −1 ). Replacement of the soy‐bean meal of the control diet and also, at the highest level of Toprina G addition, the meat and bone meal by the hydrocarbon‐grown yeast did not statistically affect total egg weight or mean egg weight significantly (total egg weight/total number of eggs laid). Total food intake tended to be higher for the birds fed the diets containing Toprina G although for the full experimental period this effect was not statistically significant. For one of the hybrid strains the food conversion efficiency was poorer for all the treatments receiving Toprina G than for the control. This effect was statistically significant at the 60 and 100 g Toprina G inclusion per kg of diet. The results indicate that Toprina G may be used as the major protein source in the diet of caged layers up to a level of 12 %.