title: Bio-economic model to evaluate twinning rate using sexed embryo transfer in dairy herds.
abstract: A stochastic bio-economic model has been used to determine the effects of new reproductive technologies over a 15-year period. A strategy of using conventional artificial insemination (AI) or embryo transfer (ET) using two sex-controlled embryos at different conception rates (CRs) and herd sizes resulted in a 24 state model. The genetic means of AI population increased over the years, and the genetic means of milk production for all of the embryo strategies were greater than those of AI. In addition, the genetic means of milk yield using different embryo-based scenarios in the expanding herds were greater than those for the fixed herds. The net profit of using sexed ET in the expanding herds was greater (P < 0.05) than that of fixed size herds. In general, there was a roughly consistent trend in net profit per cow for sexed ET strategies in the expanding herds over the years, but there was an increasing trend in net profit per cow for sexed ET strategies in the fixed herds over the years. Medium to high CRs for ET and the use of sex-controlled embryo systems, especially for induction of twin births to produce dairy replacements, will be critical elements of a system that produces significant numbers of female calves. The greater number of female calves produced in the sex-controlled scenarios allows the farmer to select animals with the best genetic potential as dairy replacement heifers; therefore, the rate of genetic gain increased in the dairy herd. Results of sensitivity analyses showed that a significant decrease in the production costs and increase in the ET performance are essential for embryo-based technologies to be profitable.
authors.affiliation: Department of Animal Science, Faculty of Agriculture, University of Guilan, Rasht, Iran. nhosseinzadeh@guilan.ac.ir
authors.forename: N
authors.initials: N
authors.lastname: Ghavi Hossein-Zadeh
authors.forename: A
authors.initials: A
authors.lastname: Nejati-Javaremi
authors.forename: S R
authors.initials: SR
authors.lastname: Miraei-Ashtiani
authors.forename: H
authors.initials: H
authors.lastname: Kohram
authors.forename: M
authors.initials: M
authors.lastname: Honarvar