Genomic Prediction for Twin Pregnancies

Twinning is a multifactorial trait influenced by both genetic and environmental factors that can negatively impact animal welfare and economic sustainability on commercial dairy operations. To date, using genetic selection as a tool for reducing twinning rates on commercial dairies has been proposed, but not yet implemented. In response to this market need, Zoetis (Kalamazoo, MI, USA) has developed a genomic prediction for twin pregnancies, and included it in a comprehensive multitrait selection index. The objectives of this study were to (1) describe a genetic evaluation for twinning in Holstein cattle, (2) demonstrate the efficacy of the predictions, (3) propose strategies to reduce twin pregnancies using this information. Data were retrieved from commercial dairies and provided directly by producers upon obtaining their permission. The twin pregnancies trait (TWIN) was defined as a pregnancy resulting in birth or abortion of twin calves, classified as a binary (0,1) event, and analysed using a threshold animal model. Predictions for a subset of cows were compared to their on-farm twin records. The heritability for twin pregnancies was 0.088, and genomic predicted transmitting abilities ((g)PTAs) ranged from −7.45–20.79. Genetic correlations between TWIN and other traits were low, meaning that improvement for TWIN will not negatively impact improvement for other traits. TWIN was effectively demonstrated to identify cows most and least likely to experience a twin pregnancy in a given lactation, regardless of reproductive protocol used. Effective inclusion of the prediction in a multitrait selection index offers producers a comprehensive tool to inform selection and management decisions. When combined with sound management practices, this presents a compelling opportunity for dairy producers to proactively reduce the incidence of twin pregnancies on commercial dairy operations.

A Proposed Selection Index for Jersey Cattle in Zimbabwe

A multitrait selection index for Zimbabwean Jersey cattle was constructed. The breeding objective was defined in terms of production and functionality traits. The production component of the index included milk yield , butterfat yield , protein yield , butterfat percent , and protein percent , while the functional component included the somatic cell count (SCC). The index was termed as . The accuracy of the index was 91.1%, and the correlation between this index and the aggregate breeding objective was 0.954. A selection index is more important in the selection of sires and cows. This leads to the greatest genetic progress and hence productivity in the dairy sector. Therefore, the application of the selection index developed is necessary if the dairy cattle industry is to maximise the exploitation of genetics and to improve its relative competitive position.

The impact of differential success of somatic embryogenesis on the outcome of clonal forestry programs. I. Initial comparison under multitrait selection

A breeding program where clones or clone mixtures are deployed through somatic embryogenesis of superior genotypes produced from elite-parent crosses was evaluated by simulation. A recurrent-selection scheme for general combining ability was considered with a breeding population size of 100 individuals. The population was assortatively pair-crossed with offspring cloned in a progeny test to facilitate forward selection of the next generation. Apart from crosses for the population advancement, "elite" crosses were made among 10 top-ranking individuals in each generation. These crosses differed in their propensity to produce somatic embryos (defined as induction success rate); the impact of this variable propensity on genetic response for two traits in selected 10-clone deployment mixtures was evaluated. The two traits considered in this study can be regarded as "productivity" and "quality". The results revealed that variation in success of clonal propagation does not necessarily lead to a reduction in potential genetic gains from selected clonal mixtures. This can be explained by the relatively small variation that exists among elite crosses, as opposed to large within-family variation. This large within-family variation provides ample potential for selecting superior offspring genotypes, even though they may have not originated from crosses among the very best of the elite parents. This conclusion holds for a range of heritability, correlations between traits, and their relative economic importance.

Genetic and economic evaluation of genetic improvement schemes in pigs – I. Methodology with an application to a three-way crossbreeding scheme

A method is presented for evaluating selection strategies for a three-way cross in pigs. Multitrait selection is considered. The criteria of evaluation are the annual genetic gains in the breeding objeetive and its component traits, and the profit which is the net present value of return from investment in the scheme. Selection in the sire line (Pietrain) contributes higher returns than selection in the dam lines. Meat percentage is the dominant trait in the sire line and has the highest impact on the breeding objective. The sire line is characterised by a negligible economic weight for the reproduction trait and has higher weights than dam lines for growth and carcass traits. The higher discounted economic values of these traits for Pietrain compared to those for dam lines deviate considerably from the equal weighting often applied in practical breeding programmes.