shoheil mirhabibi; nasser Emam jomeh kashan; shahabodin gharahveysi
Volume 18, Issue 4 , December 2016, , Pages 671-678
Abstract
The present investigation was undertaken to study reason of culling, non genetic effects and genetic parameters of longevity with two method linear model and Weibull. A data set of information from Holstein dairy cows of Isfahan province (Iran) was used for this study. The culling date of 36340 animals ...
Read More
The present investigation was undertaken to study reason of culling, non genetic effects and genetic parameters of longevity with two method linear model and Weibull. A data set of information from Holstein dairy cows of Isfahan province (Iran) was used for this study. The culling date of 36340 animals from 65 herds recorded in 1993-2014 was used. From 33219 culled cows in these years were 27.9 and 72.1 percent for voluntary and involuntary culling respectively. Lifespan and Length of productive life (LPL) were analyzed for longevity. Functional productive life (FPL) was estimated by adjusting LPL for first lactation milk yield relative to herd average. The mean of lifespan and length of productive life were estimated to be 954 and 1710 (days) respectively. The results with GLM procedure showed that HYS and age at the first calving had significant on length of productive life. The results with Lifereg procedure with Weibull function showed that effects of herd, year of first calving (p