Gene flow in a national cross-breeding beef population

Abstract

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.

Genomic selection using beef commercial carcass phenotypes

“…In practice, these offspring would most likely be cross-bred in the United Kingdom (Todd et al, 2011). Another option would be to genotype the cross-bred progeny directly.…”

“…There are three categories of beef sire that have commercial progeny: AI sires, NS bulls used in commercial herds, and NS bulls used in both commercial and pedigree herds. The commercial progeny of AI sires rarely have sire information recorded in BCMS (Todd et al, 2011), and therefore currently cannot be included in genetic evaluations. The offspring of pedigree NS bulls that are only used in commercial herds are effectively the grand progeny of elite sires in the pedigree population, and it is unrealistic to think that selection could be made on this basis, given the large generation interval involved.…”

“…For example, in the United Kingdom, the influence of AI companies in beef breeding is low, with commercial beef herds almost exclusively using natural service (NS) bulls (Todd et al, 2011). Furthermore, no one breed dominates the market for these bulls; with the top four each contributing between 10% and 30% of the total (Todd et al, 2011).…”

“…Furthermore, no one breed dominates the market for these bulls; with the top four each contributing between 10% and 30% of the total (Todd et al, 2011). Moreover, correlations between the market value of these bulls and their terminal index (TI) values are modest (Todd et al, 2011). Evidence of selection through positive genetic trends is generally only seen in terminal growth and muscle traits (Garrick, 2011;Todd et al, 2011).…”

“…Moreover, correlations between the market value of these bulls and their terminal index (TI) values are modest (Todd et al, 2011). Evidence of selection through positive genetic trends is generally only seen in terminal growth and muscle traits (Garrick, 2011;Todd et al, 2011). The potential financial benefit from genotyping NS bulls is therefore less clear than with the genotyping of elite Holstein AI candidates in the dairy sector.…”