The effect of paragenetic factors on longevity traits of simmental cows
Biotechnology in Animal Husbandry
The effects of fixed non-genetic factors (farm, season of birth, year of birth, total number of lactations) and a continuous non-genetic factor (age at first conception) on the expression and variability of longevity traits such as age at culling, length of productive life, days in milk and cow efficiency index were investigated in 2548 Simmental cows in three farming areas. Based on the model used for the analysis of the effects of non-genetic factors, including the environment and cow age at
... ent and cow age at first conception, on the expression and variability of longevity traits, the overall means for age at culling, length of productive life, days in milk and cow efficiency index were 2445.21±17.49 days, 1562.55±17.71 days, 1094.17±12.28 days and 58.68±0.32%, respectively. The effect of farming area, year of birth and lactation group on longevity traits was very significant (P<0.01), whereas the effect of season of birth was significant (P<0.05). Age at first conception had a highly significant (P<0.01) effect on age at culling, length of productive life and cow efficiency index, and no significant effect on days in milk (P>0.05). Based on the model used, the coefficients of determination (R 2 ) were very significant (P<0.01) for all longevity traits, and ranged from 0.898 for age at culling to 0.959 for days in milk.