Embryo Transfer (ET): Data Collection And Utilization
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Care should be taken when using observations in genetic evaluations from animals resulting from embryo transfer (ET) to ensure that sufficient knowledge about the recipient females is available and any potential preferential treatment is identified. Seedstock animals resulting from ET are potentially influential and reflect additional investment to achieve genetic progress. Therefore, maximizing the accuracy of genetic predictions early in the animals' lives by using the animals' own observations has increased importance. But for maternally influenced traits such as weaning weight knowledge of the recipients' breed composition, age, and other factors must be considered. Because of the increased investment, breeders are motivated to provide preferential treatment that must be accounted for. Additionally, genetic evaluation of birth weight and calving difficulty requires special considerations because of the potential influences of alternative ET technologies.
Recipient dam considerations
Effects on the phenotype due to the dam of the animal are present in traits measured up to weaning, but generally not seen on phenotypes measured post-weaning. These include both genetic and non-genetic effects. For animals produced using ET, these maternal influences are due to the recipient dam, and not the embryo donor dam. Therefore, information on the recipient dam for these maternally influenced traits is necessary to reliably include the observations in genetic evaluation. Both age of the recipient dam and its breed composition will affect maternally influenced traits - i.e. weaning weight.
Ideally, pedigree information on the recipient would be important to include but is not always available, as recipients are often commercial females. Some organizations producing genetic evaluations will not use observations resulting from non-registered recipient females. Other organizations will use these observations when age and breed composition of the recipient are known.
Recipients in genetic evaluation
Methods for modelling the effects of recipient dams are in the literature and can be easily incorporated in genetic evaluations if sufficient information about the recipient dams is available.
Researchers have reported effects of alternative embryo transfer technologies on birth weight. Literature indicates that birth weight can vary according to whether the embryo was produced using in vivo or in vitro (IVF) fertilization, the type of medium used, and incubation process (e.g., oxygen tension). In one study the calves produced using IVF were 10% heavier than calves born from artificial insemination.. In another report, relatively small differences in the length of the incubation period had a significant impact on birth weight of calves. Additionally, the oxygen concentration during incubation can affect birth weight..
Not all organizations producing embryos for implantation use the same technologies. In an ideal world, capturing data on these variables would permit the utilization of birth weight data for genetic evaluation. However, collecting and recording these data are likely infeasible to reliably allow the use of birth weight and calving difficulty observations from ET calves. The literature also indicates that these effects have not been detected in traits measured later in life. The literature contains mixed reports of the impact of alternative embryo technologies on gestation length.
BIF recommends that observations from animals resulting from ET for traits that do not have maternal effects be used in genetic evaluations as long as any preferential treatment, if given, is accounted for by assigning an appropriate contemporary group.
BIF recommends that observations from animals resulting from ET for traits that have maternal effects be used in genetic evaluations as long as the recipient dams' ages and breed compositions are available, and any preferential treatment, if given, is accounted for.
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