炭化水素酵母が飼料蛋白質給源として種鶏の繁殖能力におよぼす影響

Growing and laying perfermance of total 1, 290 hens and cocks of the fourth and the fifth generations fed either the control diet or the diet containing 15% of one of four kinds of yeast grown on n-paraffin in four domestic manufacturers, their reproducibility tested on total 6, 550 eggs, and growth rate of total 740 chicks of the sixth generation fed a conventional chick starter diet in the collaborative research in National Institute of Animal Industry and six Prefectural Experiment Stations for succesive generations were as follows:<br>1) Growth rate of the chicks of the fourth generation and feed intake of the chicks of the fifth generation on the yeast diet tended to be inferior to those on the control diet. Normal growth of the offspring of the hens of the fifth generation suggests that the delay in growth of the chicks on the yeast diet was mainly due to the unbalance of nutrients in the yeast diet, not due to the fault of yeast itself.<br>2) Little difference between the control and yeast groups was observed on laying performance, i.e. egg production, feed intake, feed conversion, egg weight and viability. Body weight of the hens of the fourth generation on the yeast diet at 36 weeks of age was significantly lighter than that on the control diet, but little difference was observed on body weight between the two groups of the hens of the fifth generation.<br>3) Fertility of the yeast group of the fourth and the fifth generations and hatchability of fertile eggs of the yeast group of the fourth generation were higher and that of the fifth generation was lower than those on the control diet, though the differences were not significant statistically.<br>4) Abnormally large variation in body weight and feed conversion were observed between two lots of the hens of the fifth generation fed the same diet in the same station. Abnormally low fertility was also observed in both of the two groups of the hens of the fifth generation fed either the control or yeast diet in two stations out of six. Adverse effect of inbreeding in a closed flock was suspected from these findings. However, normal growth of the offspring indicate that the hens of the fifth generation has normal ability to produce normal chicks.