The Rhythm of Milk Yield in Dairy Cattle

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  • 乳牛の泌乳リズム
  • ニュウギュウ ノ ヒニュウ リズム

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Abstract

This experiment was designed to investigate the rhythm of milk yield in dairy cattle and relationships between the mean square successive differences (δ2)indicating the amplitude in the fluctuation of milk yield and milk performance (total milk yields for 305 days), using the time serial analysis. Records of 108 lactations in total on milk production were adopted in Holstein herd of the Central Farm of the Rakuno-Gakuen. Results obtained are summarized as follows. 1. Close inspection revealed a fairly irregular change in daily milk yields in a cow, while lactation curve exhibited a general tendency showing a peak between the first and second month andsmooth decrease thereafter. 2. It is satisfactory to regularize time series of milk yields by applying the weighed moving average method of five terms, as a result of some considerations. 3. Fluctuations of daily milk yields of all cows showed recurrent changes. From an analysis of their correlograms, it was recognized that their fluctuations were periodic in all recurrent cows. Appearances of significant serial correient Coefficient γk(k=1, 2, ……., n days) were irregular in each indivdual, howeverr γ1 and γ2 showed high negatlve and positive correlations in all individuals, respectively. In consequence, it seems that their fluctuations consist of shortly periodical change having an interval of two days. 4. Correlation coefficient between the mean square successive differences(δ2) and total milk yields for 305days was-0.260∗∗.It is considered that there is no relationship between calving time on parity and the mean square successive differences(δ2).

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