Development of a maternal breeding goal and tools to select for this goal in UK beef production

Abstract

AbstractA maternal breeding goal for the UK beef industry is described and economic selection indexes are developed to assist in the selection of animals for the goal. The breeding objective is made up of general maternal ability traits, cow size, calving and carcass traits. The general maternal ability traits include calving interval, age at first calving, lifespan, maternal weaning weight and maternal calving difficulty. The calculations of economic values for the traits are outlined and discounted genetic expression coefficients are presented. Three selection indexes are illustrated. The first provides a general dualpurpose index for the selection of bulls to produce replacement heifers in most situations. The second, the hardy breed index, is designed to allow selection for improved maternal performance in extensive and hardy environments. The third, the fertile herd index, allows producers who do not have herd fertility problems to place more selection emphasis on objectives other than fertility. A sample of data from the Limousin breed was used to calculate estimated breeding values (EBVs) which were used to investigate response to the three indexes when the top 20% of sires were selected from either sires with 50 or more grand-maternal progeny or bulls with no recorded progeny. Approximately two thirds of the economic response seen in the selection of heavily used bulls was observed in bulls with no progeny for the hardy and dual-purpose indexes. Bulls were also selected using the existing UK terminal sire index and the resulting bulls assessed in the dual-purpose maternal index. There was found to be a negative economic response to the maternal aspect of the index, though a positive response was seen in the carcass objective. The indexes are presented as the sum of four subindexes emphasizing the contribution of maternal ability, cow size, calving and carcass, respectively to the total index. This further assists commercial producers in selection decisions.