TRIGG Progeny Test Format

Dr Patricia Johnson and Rebecca Gale
Institute of Veterinary, Animal and Biomedical Sciences
Massey University

Background

TRIGG (Terminal Romney for Improved Genetic Gain) are a group of six Romney breeders from the greater Manawatu area, who came together in 1999 to establish a breeder group.  They recognise that in addition to selecting on the maternal characteristics they also need to assess and select on carcass attributes of their sheep.  To assess this they have established a progeny test, whereby they select rams based on their normal selection index and mate the rams to commercial ewes and monitor their progeny from birth through slaughter.  Such an approach is one of the best ways to estimate the genetic merit of the rams, especially for carcass traits (given you can’t kill the rams!).  The rams that come out top from the progeny test are then used extensively throughout the flocks.

History

The first progeny test was carried out in 2000/2001 in conjunction with Richmonds and has since been carried out yearly.  In the first year 12 rams were tested, but subsequently about 24 have been tested per year.  Table 1 outlines the measurements that have been taken in each of the years.

Table 1.  Summary of Measurements Made Each Year

For the first three years of the progeny test, ultrasound measurements were taken prior to slaughter and all carcass cuts were weighed, and a total carcass value (based on the sum of the weights and values for each cut) was calculated.  From the outset it was known that weighing every cut would be time consuming both for the TRIGG group and the Richmonds team, however, in the first three years it was felt that all information should be collected from which an alternative carcass value model could be developed.  After analysis of the data it was determined that by measuring only the french rack, boneless leg and striploin an accurate estimate of carcass value could be obtained.  This is because these three cuts contribute the most to overall carcass value.  This analysis was presented at the New Zealand Society of Animal Production Conference in 2002. 

Variation in carcass value between sires has been observed in each of the years, with the dollar value difference between the best and worst sires presented in Table 2.  Although the majority of variation between sires is due to differences in carcass weight, there have definitely been instances where a sire has ranked higher than another sire with a similar carcass weight due to differences in cut distribution.  An additional point to note is that the sires chosen for this trial have been selected from a population of several thousand potential rams and represent the better rams for growth etc, so the difference in carcass value across the entire population of rams would likely be even larger.

Table 2. Difference in carcass value between top and bottom sire per year of the trial