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In this study, an industry terminal breeding goal was used in a deterministic simulation, using selection index methodology, to predict genetic gain in a beef population modelled on the UK pedigree Limousin, when using genomic selection (GS) and incorporating phenotype information from novel commercial carcass traits. The effect of genotype–environment interaction was investigated by including the model variations of the genetic correlation between purebred and commercial cross-bred performance (ρX). Three genomic scenarios were considered: (1) genomic breeding values (GBV)+estimated breeding values (EBV) for existing selection traits; (2) GBV for three novel commercial carcass traits+EBV in existing traits; and (3) GBV for novel and existing traits plus EBV for existing traits. Each of the three scenarios was simulated for a range of training population (TP) sizes and with three values of ρX. Scenarios 2 and 3 predicted substantially higher percentage increases over current selection than Scenario 1. A TP of 2000 sires, each with 20 commercial progeny with carcass phenotypes, and assuming a ρX of 0.7, is predicted to increase gain by 40% over current selection in Scenario 3. The percentage increase in gain over current selection increased with decreasing ρX; however, the effect of varying ρX was reduced at high TP sizes for Scenarios 2 and 3. A further non-genomic scenario (4) was considered simulating a conventional population-wide progeny test using EBV only. With 20 commercial cross-bred progenies per sire, similar gain was predicted to Scenario 3 with TP=5000 and ρX=1.0. The range of increases in genetic gain predicted for terminal traits when using GS are of similar magnitude to those observed after the implementation of BLUP technology in the United Kingdom. It is concluded that implementation of GS in a terminal sire breeding goal, using purebred phenotypes alone, will be sub-optimal compared with the inclusion of novel commercial carcass phenotypes in genomic evaluations. [ABSTRACT FROM PUBLISHER]

Future progress in genetic improvement and the monitoring of genetic resources in beef cattle requires a detailed understanding of the population under selection. This study examines the gene flow in the UK beef population with an uncommon breeding structure involving interaction between the beef and dairy populations. British Cattle Movement Service records were used as the primary source of information, and these data were triangulated with UK government statistics, other industry information sources and existing literature to build up a profile of the UK beef industry. Estimates were made of the breed composition of suckler cows, breeding bulls and the prime slaughter population. Cross-bred animals made up 85% and 94%, respectively, of the commercial beef breeding cow and prime slaughter populations. Holstein/Friesian (through cross-breeding) made up the largest proportion of genes in both these populations with 33% and 28%, respectively. The next five most popular breeds were specialist beef breeds: Limousin (22% and 18%), Charolais (11% and 6%), Simmental (9% and 11%), Angus (7% and 8%) and Belgian Blue (6% and 6%). Combined, the top seven beef breeds accounted for 94% of beef genetics in the prime slaughter population, and 80% of this came from non-native breeds. The influence of dairy breeds in the commercial beef breeding population was highlighted by the fact that 44% of replacement commercial beef breeding females were sourced from beef-sired crosses in the dairy herd, and in total 74% of all maternal grand dams of prime slaughter animals were Holstein/Friesian. The use of selection index technology was also investigated by analysing breeding bull sale results, with the correlation between the terminal sire index and sale price of young breeding bulls being generally moderate but significant, ranging from 0.21 to 0.38 across the major beef breeds. The most influential source of genetics in the commercial suckler beef herd was natural service breeding bulls. These were mostly sourced from pedigree breeders, and accounted for 47.8% of the genetics in the prime beef population. Artificial insemination sires were responsible for 16.6% of prime beef genetics, with the remaining 35.6% coming from dairy breeds, 95% of which was Holstein/Friesian. [ABSTRACT FROM AUTHOR]

A 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 dual-purpose 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. [ABSTRACT FROM AUTHOR]

Focuses on a study that derived combined estimates of purebred breed values of predominant temperate beef breeds using published information on relative performance of beef breed crosses. Materials and methods used; Results and discussion; Implications.