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255. A study of persistency in a herd of Ayrshire cows

Published online by Cambridge University Press:  01 June 2009

G. Pontecorvo
G. Pontecorvo
Affiliation:
Institute of Animal Genetics, University of Edinburgh
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Extract

Connecting the trend of the different parts of the lactation curve with what is believed to be the underlying hormonal mechanism, it has been pointed out that any analysis of the curve must deal separately with three parts. The central portion, lying between the peak of daily production and the rapid decline (drying off) has been the object of investigations in an inbred Ayrshire herd. Coefficients of persistency were obtained by fitting exponential curves to this central portion. When first lactations were excluded and correction for month of calving applied, the coefficients (P) were found to be reasonably consistent for different lactations of the same cow. Month of calving accounted in this herd for about one-third of the variance of P. Of the remaining variance approximately one-half is attributed to differences among cows. A possible physiological explanation of the cause of the well-known negative correlation between maximum yield and persistency has been suggested. No conclusions can be drawn from this material on the relative importance of heredity and environment in determining persistency.

Type
Original Articles
Information
Journal of Dairy Research , Volume 11 , Issue 2 , May 1940 , pp. 113 - 120
Copyright
Copyright © Proprietors of Journal of Dairy Research 1940

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References

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