The application of embryo transfer in herd improvement for small-scale milk production systems in south-east Brazil

Abstract

Abstract The results of a simulation-based analysis of the use of superovulation and embryo transfer (ET) in the small-scale dairy systems of south-east Brazil are reported. In common with changes in other management factors, the application of ET to these systems provokes a series of modifications to the herd structure and dynamics. But in contrast to alterations in nutritional management, those effects are not confined to an initial period of system perturbation and a state of herd equilibrium is only effectively re-established with the termination of ET. The continuing system disturbance whilst ET is in operation, plus the long time-scale for herd improvement by this means, make for considerable delays in a return on the investment incurred. Critical factors in the application of ET in this context are the number of viable embryos per collection and the success rate in the process of implantation. Judging from experience elsewhere (Ruane, 1988), an appropriate R & D effort might raise the current mean values in commercial practice of four embryos per collection and an implantation rate of 50% to levels of six embryos per collection and an implantation rate of 70%. Such technical improvements could increase the overall efficiency of the process substantially, attaining a mean annual genetic gain of 1% of the mean over a period of 35 years. But, even so, the producer faces a waiting period of some 15–20 years for the first significant returns from the use of ET. The economic viability during that period depends, critically, on the development of a market for the surplus embryos that are produced by the process.