| Estimation of covariance functions and genetic parameters for test day milk yield records of Chinese Simmental cows (ABSTRACT) 20415 observations of test day milk yields in 1438 lactation of Chinese Simmental cows 380 from a herd between 1980-2000 were collected from Gaolintun farm in Inner Mongolia. Day-in-milk was recorded into 15 classes with 7day-intemal for first ten classes, with 28day-internal for next three classes, with 42day-interval for final two classes. In estimating parameters -using random regression test-day model with data of 5700 in first lactation, 9 order of fit for Lengendre polynomial of DIM is better in the model by means of 13 runs with DxMiu~ program in software DFREML 3.1. Results were shown that the additive genetic covariance and permanent environment covariance turned up peaks at the peak of milk yields while other test-day covariance curved surface were equal. All the heritabilities of test day milk yields are between 0.0730.8566. The heritability in first lactation of cows is lower and heritability on day56 is the highest. In fourth lactation of cows the higher heritability is at day42 and at day3s, 0.8566 and 0.8556 respectively. Both of genetic correlation of the day7 yield with day2s yield and day7 yield with day35 yield of the test day in first lactation are negative correlation, and those are .1750 and .0842 respectively, but all the genetic correlation of test day yields are negatively correlative. All the genetic correlation of test day yields in second lactation are positively correlative and all the phenotypic correlation of day7 with other 12 test-day yields are negatively correlative. All the genetic correlation of test day yields in third, fourth, fifth lactation are positively correlative. They are all negative correlation in phenotypic correlation of day2s-. day126 with day7 in third lactation, and day7 with all test day milk yields in the fourth lactation, and day35 day7o with day3o1 in the fifth lactation. |
PDF Full Text Request