Genetic Analysis Of Daily Milk Yields Of Holstein Dairy Cows In Southern China

Function-valued traits have received considerable attention during recent years, and become one of the hottest themes of the quantitative genetics. There have been numerous studies about the lactation curve of the dairy cow and the animal growth curve in the animal production, which attribute to function-valued traits. This research uses two methods to study the genetic analysis of daily milk yields of Holstein dairy cows' in southern China. The data comprise records of 507 dairy cows during first lactation from the Changde Herd calving between 2002 and 2004, and from the Chengbu Herd calving between 2003 and 2004, and daily milk yields are recorded with 30 day interval. One method: The lactation curve is fitted by the equation of Wood using SAS. Parameters of the model obtain by the nolinear least square. Then values of the model's parameters are considered as traits, which are analyzed genetic characters using the MTDFREML. Another method: Firstly, qualify the best Legendre polynomial orders of the fit for the genetic and permanent environmental effect. Then genetic parameters estimates are studied and covariance functions detain through running with DXMRR program in software DFREML 3.1. At last, estimate the covariance of the arbitrary two times using the interpolation, and then map the 3-D graph.The main results of this study are followed:1. Lactation curves are fitted by the equation of Wood. The average R~2 value is 0.9754, and the range is 0.8062~0.9996. The results of estimating parameters of the model by using MTDFREML are as below. (1) Heritabilites of a, b and c are 0.1104, 0.1423 and 0.1813, respectively, and their proportions of permanent environmental effect variance to phenotypic variance are 0.0752, 0.0650 and 0.0533, respectively. (2) A has negative correlation with b and has high correlation with c, and correlation coefficients are -0.2513 and 0.7214, respectively. B has low correlation with c, and the correlation coefficient is 0.7061. (3) The permanent environmental correlation between a and b is negative, whose coefficient is -0.3297. The permanent environmental correlation coefficient is 0.7001 between a and c, which is high, while...