Effectiveness of alternative breeding schemes for a dairy cattle population of limited size.

摘要

There are many dairy cattle populations of approximately 100,000 cows in size in the world that have sought genetic improvement. The geographically isolated dairy cattle population in Taiwan was used to demonstrate alternative breeding schemes for their rates of genetic improvement in production and their economical efficiency. Since the source of germplasm. import was from the U.S., the first study was to estimate genetic responses in individual traits, yield merit functions, and total merit functions when selection was based on criteria that were currently available to the U.S. dairy cattle breeders.; To maximize genetic improvement in milk yield, several practical breeding schemes were designed in the second study. Each of the alternative breeding schemes focused on the generation of genetically superior bulls that are to be use to breed cows in the population, and each involved the use of semen imported from the U.S. These breeding schemes belonged to three categories. The first had breeding bulls produced by using local genetic resources but their sires were foreign. The second used imported germplasms to produce breeding bulls, which would not go through progeny test. The third category included each of the schemes in the first two categories plus a supplement of additional imported germplasms. Ranking of cumulated genetic progress after 25 years showed that the best breeding scheme was the one which used imported embryos to produce bulls that would be screened by the performance of their paternal-half-sibs before used for artificial insemination purposes. This scheme included a supplement of 5% imported pregnant heifers.; Economic efficiency of the same breeding schemes was assessed in the third study, since in practice, a mere consideration of their ability to maximize genetic progress would be insufficient. In this study, the appropriate governmental agencies would be expected to bear all costs for the infrastructure and operation of a breeding scheme. Therefore, the cost factors of a scheme would include only those that would incur to farmers such as costs of semen, artificial insemination, importing heifers, and the increased costs of feeds and health and fertility problems due to increased milk production. The economic efficiency of a breeding scheme was calculated as Net Present Value of accumulated benefit over a 25 years time horizon. The ranking of schemes by economic efficiency was different from that by rate of genetic progress. However, the exact same breeding scheme was deemed to be the best according to both criteria.