Ferdowsi University of MashhadIranian Journal of Animal Science Research2008-31061220090622Comparison of some functions describing the shape of the lactation curve for Holstein cowsComparison of some functions describing the shape of the lactation curve for Holstein cows2814310.22067/ijasr.v1i2.1974FAHossein MehrabanDepartment of Animal Science, Faculty of Agriculture, Zabol University, Zabol, IranHomayoon FarhangfarDepartment of Animal Science, Birjand Faculty of Agriculture, Birjand, Iran0000-0000-0000-0000Javad RahmaniniaDepartment of Animal Sciences, Faculty of Agriculture, Zabol University, Zabol, IranHossein Ali SoltaniKhorasan Razavi Jahad – e – KeshavarziJournal Article20091026A 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.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.https://ijasr.um.ac.ir/article_28143_3d8bc475c13fc7c8045abe8c522fac23.pdf