Heifer Fertility in Norwegian Dairy Cattle: Variance Components and Genetic Change

• Published in: Journal of dairy science 2003-08, Vol.86 (8), p.2706-2714
• Main Authors: A.-Ranberg, I.M., Heringstad, B., Klemetsdal, G., Svendsen, M., Steine, T.
• Format: Article
• Language: English
• Subjects: animal breeding; animal genetics; Animal productions; Animals; Biological and medical sciences; Breeding; breeding value; Cattle - genetics; Cattle - physiology; dairy bulls; Dairy cattle; dairy cows; data analysis; equations; Female; female fertility; Fertility; Fertility - genetics; Fundamental and applied biological sciences. Psychology; genetic change; genetic trend; genetic variance; Genetic Variation; heifers; heritability; Lactation - genetics; Linear Models; Models, Genetic; nonreturn rate; Norway; Norwegian Red; prediction; Predictive Value of Tests; pregnancy rate; progeny testing; selection criteria; selection index; sire evaluation; Terrestrial animal productions; variance components; Vertebrates
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(03)73866-1

Variance components and genetic change were estimated for 56-d nonreturn rate in virgin heifers using first insemination records of a total of 1,632,961 Norwegian Dairy Cattle daughters of 2945 sires. Six univariate mixed linear sire models were compared. The heritabilities varied from 1.2% to 1.4%. All models gave favorable, although different, estimates of genetic change of 56-d nonreturn rate. The method used to validate the genetic trend did not detect bias in any of the models. Goodness-of-fit and predictive ability were used to further validate the models. Three models included service sire, but this effect had little influence on the results. Models treating the herd-year effects as random showed smaller prediction error and higher correlation between observed and predicted values than the models treating herd-year effect as fixed. To avoid confounding of environmental and genetic effects, the model including fixed effect of month-year was preferred over a model with only month of first insemination to estimate the genetic change. Female fertility has been successfully included in the total merit index of Norwegian Dairy Cattle for 20 yr. This has resulted in genetic improvement and the chosen model showed annual genetic change of 0.04% for 56-d nonreturn rate in heifers between 1979 and 2000.