Comparison of some functions describing the shape of the lactation curve for Holstein cows

Document Type : Scientific - Research Articles

Authors

Hossein Mehraban ¹

Homayoon Farhangfar ²

Javad Rahmaninia ³

Hossein Ali Soltani ⁴

¹ Department of Animal Science, Faculty of Agriculture, Zabol University, Zabol, Iran

² Department of Animal Science, Birjand Faculty of Agriculture, Birjand, Iran

³ Department of Animal Sciences, Faculty of Agriculture, Zabol University, Zabol, Iran

⁴ Khorasan Razavi Jahad – e – Keshavarzi

10.22067/ijasr.v1i2.1974

Abstract

A total of 260709 monthly test day milk records of 30903 first lactation Holstein cows was used to determine the best
function to describe the lactation curve. The records were obtained from first lactation Holstein of 216 herds from 1988 to
2006 in Khorasan province. The functions used in current study were Wood’s incomplete gamma function, Ali and Schaeffer
function, and Legendre function of fifth order. Six criteria including error sum of squares, mean error sum of squares,
coefficient of determination, adjusted coefficient of determination, correlation coefficient and variance inflation factor were
used to compare the performance of the functions. The results indicated that Ali and Schaeffer function was more preferable
than other functions when the variance inflation factor was ignored. However the Legendre function was found to be more
appropriate than other functions when the variance inflation factor was considered.

Keywords

Holstein cow

Shape of lactation curve

Mathematical functions

Inflation variance factor

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References

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