Polypay

 NSIP Notebook

January 10, 2007                                                                                                                   Number 10

The Fall, 2006 Polypay National Genetic Evaluation  

David Notter and Bindu Vanimisetti

Department of Animal and Poultry Sciences

Virginia Tech 

Introduction

The Fall, 2006 Polypay genetic analysis is now complete and results are available for distribution.    

The Data 

Data were received on 418 breeding ewes and 592 live lambs from 16 flocks, including one newly enrolled flock.  The lambs represented offspring of 44 Polypay rams.  Following editing, valid records were received for 352 weaning weights, 187 postweaning gains, and 306 litter sizes.

The entire NSIP Polypay across-flock database now contains records from 42 flocks with 18,571 weaning weights, 11,649 postweaning gains, and 16,170 litter sizes.  EPDs were calculated for a total of 32,544 animals, including 7,950 breeding ewes and 925 sires. 

Means for reported traits are shown below.  Weaning weights were adjusted to a weaning age of 60 days and to a twin birth and rearing, adult dam, and ewe lamb basis.  Litter sizes were adjusted to an adult-ewe basis. 

                Trait                                                                                      Mean                     

    60-day adjusted weaning weight—twin lamb basis                                47.3 lb

                postweaning gain                                                                                  .63 lb/day

                litter size                                                                                            2.21 lambs             

 The current performance records were received at the genetic evaluation center on November 14, 2006.  The results of the EPD analysis were provided to the breed coordinator on December 21 to give a turnaround time of 37 days. 

 EPD Reports

Results of the genetic analysis were provided in a single spreadsheet containing animal identification and EPDs for all animals in each flock.   Animals in the spreadsheet were listed in the following order: 

·         Breeding ewes

·         Yearling ewes

·         Breeding rams

·         Yearling rams 

The listing contains all breeding animals listed on the preprinted data entry spreadsheet, any breeding animals that were added to inventory, and all surviving lambs from the current lamb crop. Animals that were culled or died were identified; EPDs will be provided for these animals, but they will not appear on next year's spreadsheet.   

The 2006 Polypay Sire Summary

The 2006 NSIP Polypay Sire Summary is now also available for distribution to breeders and other interested parties.   In order to be eligible for the Sire Summary, a ram must have at least five progeny with weaning weight records or at least 10 daughters with litter size records.  Rams listed in the Sire Summary must also have a prediction error of not more than 0.95 pounds for weaning weight, 2.5 pounds for 120-d postweaning weight, or 0.95 pounds for maternal milk.  The current sire summary contains EPDs for 272 sires.  Of these, 128 met accuracy requirements for listing and were born after July 1, 1998.  This is a 10% increase over the number of sires listed in the June, 2006 Sire Summary.

 Genetic Trends in the Polypay Breed

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 Polypay flocks.  Each point represents the average EPD of all animals born in each year since 1986.  Since 1990, consistent and significant changes have been observed for 60-day weaning weight, maternal milk, and 120-day postweaning weight EPDs.  EPDs for number of lambs born changed less rapidly over this period, but have had a gradual positive trend since 1997.  As discussed before in this Notebook series, these values could be increased further by more intense selection, but represent gradual and consistent changes in the breed that are appropriate to its role as a general purpose maternal breed.