誘起泌乳による乳牛の泌乳能力の推定-2-

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This is an interim report on a study on the possibility of predicting the dairy performance of cows by investigating correlations between the yields of induced lactation in heifers on three farms administered with synthetic estrogen before mating and those of normal lactation in the same individuals after insemination and calving.In Fukushima, Hokkaido and Univ. Farm, 12 Holstein and graded-up heifers, aged 17.6 months on the average, were injected subcutaneously with 5mg (105 I.U.) of synthetic estrogen (p, p'-dicarboe-thoxy-oxytrans-α, β-diethylstilbene with the proprietary name Euvestin) in oil every three days for 10 times, and the yields of induced lactation were recorded. After examined for the influence of the estrogen treatment upon the ovaries, estrus, and growth, the heifers were inseminated and calved, and the yields of normal lactation were recorded. Then correlations of yields between the two types of lactation were investigated. Since there were wide diversities of age and milking period among individuals, corrections between these factors were examined.The results obtained are summarized as follows.(1) Concerning the dairy records, the yields of induced lactation were about one-third or one-fourth of those of normal lactation.(2) When the results obtained in Fukushima were compared with those in Hokkaido, there were little differences in the yield of normal lactation, but in the case of induced lactation the results in Hokkaido showed a shorter milking period, lower peak production, earlier peak period, and consequently less total yield, and a little larger variation in various characters.(3) The correlation coefficients of the yields between the two types of lactation were fairly high in such combinations as between peak productions, between average daily productions, between peak production and total yields, and between average butter fat percentages. Particularly, between peak productions, the coefficient was +0.6007 with the actual yields and +0.6989 with the corrected yields and between average butter fat percentages, it was +0.7875 and +0.7513, respectively.(4) In general, the correlation coefficients with corrected yields were higher than those with actual yields, and those given in the results in Fukushima were higher than those in the results in Hokkaido.(5) The correlation coefficients between yields for 30, 60, and 90 days of induced lactation and various yields of normal lactation were not rather high, but those for 30 days were the highest of them. In these cases, those of the results in Hokkaido were a little higher than those of the results in Fukusima, and those of the actual yields were higher than those of the corrected yields. Thus, the relations became reverse to the facts mentioned above. Possible discussion was made about the causes.(6) From these facts, the peak production, average daily production, and average butter fat percentage in the case of induced lactation may serve enough for the prediction of yields of normal lactation.(7) The influences of the estrogen treatment upon the ovaries, estrus, and growth may be present, but it needs further experiments to draw any conclusions on this matter. Genetical and environmental factors may play some roles.
社団法人日本畜産学会の論文

誘起泌乳による乳牛の泌乳能力の推定-2-

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