Title: Development and Validation of a Multi Trait Selection Index for Assisted Propagation of Adaptable and Productive Cattle Genetics
Authors: JESSICA OKONKWO, CONFIDENCE JOHN, OLORUNNISOLA ADEOLA OLUWASEGUN
Volume: 10
Issue: 9
Pages: 38-55
Publication Date: 2026/09/28
Abstract:
Assisted reproduction, particularly ovum pickup coupled to in vitro embryo production, has changed the rate-limiting step in cattle genetic improvement from the number of calves a cow can produce to the number of donor animals a breeding program chooses to propagate from. This shift raises the stakes of a question selection-index theory has addressed since its original formulation but that assisted-reproduction programs frequently answer by default rather than by design: which traits enter the aggregate genotype, and at what economic weight, when a nucleus scheme can multiply a chosen donor's genetics an order of magnitude faster than natural service. Indices built primarily around production traits risk propagating unfavorable genetic correlations with fertility and environmental adaptation at the accelerated rate the technology itself enables, compounding rather than correcting a known antagonism. This paper develops and specifies, without reporting completed genetic-evaluation results, a multi-trait selection index for assisted propagation programs that combines production, fertility, environmental adaptation, and donor propagation-efficiency traits within a single aggregate genotype, following Hazel's original index formulation extended with genomic information. The index construction protocol specifies trait definitions, heritability and genetic-correlation parameterization, economic and biological weighting procedures, and a cross-validation design comparing pedigree-based and genomic-enhanced index accuracy. A companion validation protocol specifies simulated correlated response, sensitivity analysis of weighting assumptions, and monitoring of realized genetic trend against predicted response once the index is deployed. The central proposition is that omitting adaptation and donor propagation-efficiency traits from an assisted-reproduction breeding index does not leave genetic progress on those traits merely stagnant but drives it backward, because assisted reproduction concentrates selection intensity on a small donor population whose unweighted trait values are, by construction, not selected for. Falsifiable hypotheses concerning correlated response, genomic accuracy gain, and weighting sensitivity close the paper.