Suffolk

NSIP Notebook

August 7, 2005 Number 6

David Notter, Randy Borg, and Larry Kuehn

Department of Animal and Poultry Sciences

Virginia Tech

Genetic analysis of the 2005 Suffolk lamb crop has now been completed. Results of the analysis have been sent to the breed coordinator for distribution to participating NSIP Suffolk flocks. Genetic trends in Suffolk performance traits are again included in the report.

The entire NSIP Suffolk across-flock database now contains records from 83 flocks with 26,141 weaning weights, 11,295 postweaning gains, and 16,597 litter sizes. EPDs were calculated for a total of 40,659 animals, including 11,370 breeding ewes and 2,525 sires.

Means for reported traits are shown below. Weaning weights were adjusted to a single birth and rearing, adult dam, and ewe lamb basis. Litter sizes were adjusted to an adult ewe basis.

60-day adjusted weaning weight 73.9 lb

postweaning gain .87 lb/day

litter size 1.90 lambs

The 2005 Suffolk data were received at the genetic evaluation center on July 7, 2005. The results of the EPD analysis were provided to the breed coordinator on August 3 to give a turnaround time of 27 days.

The 2005 NSIP Suffolk Sire Summary is also now available for distribution to breeders and other interested parties. In order to be eligible for the Sire Summary, a ram must have at least 5 offspring with weaning weight records or at least 5 daughters with lambing records. Prediction errors of 1.9 or less for weaning weight, 3.7 or less for 120-d postweaning weight, or 1.0 or less for maternal milk are also required. These values approximately correspond to the minimum accuracy value of .20 required in previous years. This year’s sire summary contained EPDs for 534 rams, an 7% increase over last year. From these, only rams born after Jan. 1, 1998 were listed in the main sire summary, which contained EPDs for approximately 190 rams.

Patterns of change in EPDs since establishment of NSIP in 1986 are shown in Figure 1. These results document the traits that have received emphasis in participating Suffolk flocks. Each point represents the average EPD of all animals born in each year since 1986. Consistent and significant increases were observed for 60-day weaning weight and 120-day postweaning weight. Maternal milk EPDs also increased significantly over this period, but by much less than the EPDs for growth traits. EPDs for number of lambs born, in contrast, exhibited only a slight positive trend over this period. These patterns are consistent with the primary role of the Suffolk as a terminal sire breed used to add growth and leanness in crosses with other breeds. It is not expected or desirable that changes in EPDs be observed for all traits. For example, the mean litter size of adult Suffolk ewes is 1.9 lambs born per ewe lambing. There may be little value in increasing prolificacy beyond this point and the stability in EPDs observed over time for this trait in Figure 1 confirm that most Suffolk breeders see little value in selecting for further increases in prolificacy.

Since implementation of the across-flock genetic analysis in 1995, changes in EPDs for weaning and postweaning weights have averaged 0.10 to 0.12% per year. In contrast, the average EPD for maternal milk and percent lamb crop have hardly increased at all over this period. These trends could certainly be increased, if desired, by more intense selection. However, the observed trends in EPDs are generally similar to those reported for beef cattle and represent gradual and consistent changes in the breed as a whole. By comparison, over the past 20 years six of the largest beef cattle breeds (Angus, Hereford, Charolais, Limousin, Red Angus, and Simmental) have achieved average annual increases in EPDs of about 0.2% per year for weaning weight and yearling weight and 0.1% per year for maternal milk.