Poll Dorset and Dorset Horn breeders now have a better tool to help identify their most profitable sheep thanks to a new Signet Maternal Breeding Index.

The index, produced by SAC scientist Kirsty Moore, places a greater emphasis on the Estimated Breeding Values (EBVs) for litter size (prolificacy) and maternal ability (milk) – aiming to identify those breeding lines where females regularly rear a high proportion of twin lambs.

Signet, which is part of EBLEX, records more than 4000 Dorset lambs a year. High levels of genetic progress has already been achieved using their Terminal Sire Breeding Index.

The breeding potential for lamb growth rate to 21 weeks of age has increased by nearly 6kg since 1990, along with significant changes in muscling. The degree to which the recorded population has changed during this time is massive; the genetic merit for growth rate of the top 5% of the lambs recorded in 1990 is now equivalent to the bottom 5% of lambs born this year.

The Poll Dorset and Dorset Horn breeding programme focuses on economically important traits – so that commercial sheep producers using Dorset genetics can increase their returns, says EBLEX breeding specialist Samuel Boon.

“Lambs sired by performance recorded Dorset rams are faster to finish and can be taken to higher weights without risk of penalty for fatness. The new Maternal Index will enable more focus on the identification of sires whose daughters are more productive.”

Using this index to select more prolific breeding lines is far more effective than simply selecting a ram born as a twin or triplet, as the Litter Size EBV takes into account hundreds of lambing records from female relatives and provides a more accurate overview of a ram’s maternal genetics.

The new index is a useful guide, but Mr Boon still encourages ram buyers to use all the EBV information that is available when selecting a ram. “Different flocks have different breeding objectives, so select the ram with the right combination of EBVs for your specific flock.”

Robert Hole, from the Sherborne Poll Dorset flock, is delighted with the changes. “An increasing number of ram buyers are looking for performance recorded rams. The new Maternal Index will be a real asset when it comes to selecting sires whose daughters will be more productive and ultimately more profitable.”

Breeding information from the latest analysis can be found on the Signet website www.signetfbc.co.uk and performance records will be available for the Signet recorded rams at the main sale for the breed – the May Fair – on Wednesday 4 May 2011.