Development of a genetic evaluation system for structural soundness traits in Angus cattle

Abstract

Three options comprising a generalized threshold model and two linear animal models were explored to predict and express breeding values for structural soundness traits in Angus cattle, using front feet angle as an example trait. Front feet angle scores (scored on a 1 to 9 scale, with 5 being the most desirable score) from 2926 Angus cattle under three years of age were used. Estimated breeding values (EBVs) predicted from a generalized threshold model by grouping animals with scores 1 to 4 as category 1, representing steep foot angle (%STE), category 2 with score of 5, representing desirable score (%DESI) and category 3 with scores 6 to 9, representing shallow foot angle (%SHA). These were compared with EBVs from a conventional linear animal model with the original scores of 1 to 9 or after assigning scores according to Snell's procedure to differentiate desirable scores. EBVs obtained as %DESI was identified as an appropriate way to express EBVs in a manner that would allow breeders to identify differences in Angus cattle for expected progeny structural soundness.