Repeatability and heritability of response to superovulation in Holstein cows

The objective of this study was to estimate the relative effects of genetic and phenotypic factors on the efficacy and efficiency of superovulation fo r Holstein-Friesian cows reared in Brazil. A database, established by the A ssociacao Brasileira de Criadores de Bovines da Raca Holandesa, consisting of a total of 5387 superovulations of 2941 cows distributed over 473 herds and sired by 690 bulls was used for the analysis. The records were analyzed by MTDFREML (Multiple Trait Derivative-Free Restricted Maximum Likelihood) , using a repeatability animal model. The fixed effects included in the mod el were contemporaneous group (veterinarian, herd, year and season of the s uperovulation); number of semen doses; cow age; and superovulation order. T he estimated repeatability of the number of the transferable embryos was lo w (0.13), and the estimated heritability was 0.03. These results indicate t hat environmental factors play a critical role in the response of a cow to a superovulation treatment. There is little evidence that future responses to superovulation by individual females can be predicted by previous treatm ent(s) or that superovulation response is an heritable trait. (C) 1999 by E lsevier Science Inc.