Substantial gains are being made in genetic progress for terminal sheep populations in the UK
Genetic gain in recorded and unrecorded populations has increased dramatically since the initial sire reference scheme began in 1990, as demonstrated by the Terminal Sire Index (Figure 1) for Suffolk and Texel breeds. It is important to recognise that the rate of genetic gain is around 50% greater for recorded populations. It is thought that the purchase of breeding stock from recorded flocks that are improving has helped those non-recorded flocks to develop, particularly where semen from the top 10% sires has been used.
With an emphasis being placed on commercial farmers to reduce the ‘days to slaughter’ of their lambs, the increase in genetic gain for scan weight EBVs (figure 2) for three of the main terminal sires (Texel, Suffolk and Hampshire Down) is pleasing to see. This will translate to a proportional economic advantage. This has also coincided with an increase in muscle depth EBV (figure 3), which would indicate that not only are lambs growing faster, but their carcases will have a better conformation with a greater proportion of the meat at the higher value areas.
At an industry level, the impact of a successful breeding programme is not solely about genetic change, but also the penetration rate of recorded rams within the industry.
While the proportion of flocks in the UK that record with Signet may not be high, by targeting the larger flocks selling rams to other people, the national impact of performance recording is significant.
The proportion of the Texel lamb crop sired by a Signet recorded ram has now reached 40% of all lambs born. The proportion of Suffolk lambs by a recorded ram has stabilised at about 25% of lambs born. More than 60% of Hampshire Down lambs are by a Signet-recorded ram.