2002 TRIALS
NARROGIN AGRICULTURAL COLLEGE MATERNAL BREEDS EVALUATION
By Rob Davidson, Steve Madson & Sarah Wiese
The Narrogin Agricultural College has been the site for a maternal breed's demonstration involving Merino and first cross South African Meat Merino (SAMM) and Dohne ewes since January 2000. The demonstration had two key objectives, to compare the growth and carcase attributes of the Merino and first cross wether progeny and to compare the performance of the first cross South African breeds as prime lamb dams in terms of both reproduction and wool production to the typical Australian Merino. The following reports on the reproductive potential, lamb growth rate through to slaughter, carcase quality, wool production and economics of running either pure Merino or a crossbred ewe flock during 2002. Previous results from this demonstration have already been published in the Ovine Observer (issue 11, 14 and19) See trials in 2000, 2001 section below.
Gracefield Ewes
The black tag ewes of either pure Merino or Merino crosses of SAMM and Dohne genotypes were purposely born and reared at the College for this project. The ewes were teased by testosterone injected wethers and then mated to four Suffolk rams for 8 weeks commencing on 6th December 2001. The Suffolk rams were from the LAMBPLAN tested Cheeryna stud, Williams. Scanwest Livestock Services using real time ultrasound to determine the conception rate and the number of fetuses in utero scanned the ewes on 18th March 2001. The pre-joining liveweight and pregnancy scanning results along with the number of potential lambs for the Merino and first cross ewes are shown in Table 1.
Table 1
The pre-joining liveweight, number of ewes of each sire genotype with zero, single and multiple fetuses at scanning, ewe conception rate and the number of potential lambs per ewe mated.| Genotype | No | Liveweight (kg) | Dry ewes | Single fetus | Multiple fetuses | Potential lambs | Conception rate (%) |
Potential lambs per ewe mated |
|---|---|---|---|---|---|---|---|---|
| Merino | 49 | 49.1 | 9 | 37 | 3 | 43 | 82 | 0.88 |
| SAMM | 50 | 59.6 | 0 | 45 | 5 | 55 | 100 | 1.10 |
| Dohne | 60 | 53.1 | 5 | 44 | 11 | 66 | 92 | 1.10 |
At mating, the first cross ewes were significantly heavier than the pure Merino ewes. The SAMM cross ewes were significantly heavier than the Dohne cross ewes that were in turn heavier than the Merino ewes.All of the SAMM cross ewes were scanned as being pregnant whereas 5 Dohne cross ewes and 9 Merino ewes scanned as being dry. The conception rate (ewes pregnant per ewes mated) of the SAMM cross ewes (100%) was significantly higher than the conception rate of the Merino ewe (82%). Both the SAMM and Dohne cross ewes (1.1) were scanned as having significantly more potential lambs in utero per ewe mated than the Merino ewe (0.88).
The ewes commenced lambing in May in individual genotype lambing paddocks with similar pasture levels to determine lamb survival to marking. At marking (26th June 2002) all lambs (age approx 5 weeks) were tagged, vaccinated (Glanvac 6S), ear marked, tail docked (elastrator rings), castrated and weighed. The ewes and lambs were returned to the one mob to monitor lamb growth rates to weaning and slaughter.
Table 2
The potential and actual number of lambs marked and weight of lambs at marking| Genotype | Potential lambs | Actual lambs marked | Marking % | Marking Wt |
|---|---|---|---|---|
| Merino | 43 | 38 | 78 | 15.2 |
| SAMM | 55 | 49 | 98 | 18.4 |
| Dohne | 66 | 47 | 78 | 15.5 |
Approximately 11% of the lambs scanned as being in utero to the Merino and SAMM cross ewes were either lost prior to birth or failed to survive to marking, however 29% of the lambs scanned as being in utero in the Dohne cross ewes failed to make marking. The Narrogin Agricultural College averages between 60-70% marking for the Merino maidens. By 5 weeks of age (marking) the progeny from the SAMM cross lambs were significantly heavier than the progeny from the Merino or Dohne cross ewes. This difference continued through to week 20 prior to the slaughter of the first draft of lambs (Table 3). There was no difference in the growth rate of the lambs post marking.
Table 3
The liveweight at marking and 20 weeks plus growth rate from marking to 20 weeks of first and second cross lambs.| Genotype | Marking Wt | 20 Week Wt | Growth rate from marking |
|---|---|---|---|
| Merino | 15.2 | 42.1 | 256 |
| SAMM | 18.4 | 47.1 | 273 |
| Dohne | 15.5 | 42.0 | 252 |
Table 4
Final liveweight, carcase weight and fatness and $ returns for 69 cross bred lambs sold in the first draft| Genotype | No | Final Wt | Hot carcase Wt | GR | Dress % | $/Head * |
|---|---|---|---|---|---|---|
| Merino | 15 | 48.0 | 21.0 | 9.1 | 43.6 | $71.26 |
| SAMM | 35 | 51.2 | 23.4 | 11.1 | 45.5 | $77.86 |
| Dohne | 19 | 47.7 | 20.8 | 9.4 | 43.5 | $72.16 |
*Includes a $6.00 skin
Creative SAMM Lamb cuts courtesy MONDO Meats
Mr Peter Trefort, proprietor of Hillside Meats abattoir, Narrogin encouraged the project team to produce heavier sucker lambs. With this in mind, the liveweight of the first draft of suckers averaged 49.5kg (Table 4). Seventy percent of the SAMM cross progeny, 42% of the Merino progeny and 41% of the Dohne cross progeny were slaughtered in the first draft. The SAMM cross progeny were significantly heavier, fatter, dressed higher and returned more per head than the Dohne cross or Merino progeny. Whilst being fatter, the SAMM cross carcases were still graded as being in the fat score 2/3 premium category. There were no differences in any of the carcase attributes between the progeny of the Merino and Dohne corss ewes. During spring, Q Lamb's price schedule paid premium returns per kilogram for carcases weighing 17-24kg fat score 2 or 3. Some of the SAMM cross progeny were discounted up to 70c/kg (approx $20/head) for being too heavy for market specifications. If the schedule didn't discount the heavier lambs, then the $6.60 difference per head between the price received for the SAMM cross progeny and the Merino progeny would have been even larger.
Table 5
Final liveweight, carcase weight and fatness and $ returns for 52 cross bred lambs sold in the second draft.| Genotype | No | Final Wt | Hot carcase Wt | GR | Dressed % | $/Head* |
|---|---|---|---|---|---|---|
| Merino | 18 | 46.8 | 18.9 | 8.9 | 40.4 | $65.67 |
| SAMM | 14 | 49.4 | 20.7 | 10.6 | 42.0 | $71.80 |
| Dohne | 20 | 47.2 | 19.0 | 9.4 | 40.3 | $65.54 |
* Includes a $6.00 skin - the lambs were paid at the same price as those in draft
The lambs sold in the second draft were lighter, leaner and dressed lower than those slaughtered in the first draft (Table 5). The SAMM cross progeny however, still produced heavier carcase weights, with higher dressing percents and returned more per head than the Dohne cross and Merino progeny. Like in the first slaughter there were no differences in any of the carcase attributes measured between the progeny of the Merino and Dohne cross ewes. The lower dressing percentage recorded in the second draft of lambs seems to be due to the sharp cut off to the season producing bulkier dry feed or lower nutritive quality.
Table 6
Percentage of lambs slaughtered on either of the 2 dates or rejected for not meeting market specifications.| Genotype | 1ST Draft (%) | 2nd Draft (%) | Not Slaughtered (%) |
| Merino | 42 | 50 | 8 |
|
SAMM |
70 | 28 | 2 |
| Dohne | 41 | 44 | 15 |
98% of the SAMM cross, 92% of the Merino and 85% of the Dohne cross progeny met the market specifications and were slaughtered at Hillside Meat Abattoirs (Table 6).
Table 7
Lambs not making market specifications (rejected)| Genotype | Number | Final Wt | Carcase Wt | Dress % | GR | $/hd (incl $6 skin) |
|---|---|---|---|---|---|---|
| Merino | 3 | 40.3 | 15.2 | 37.7 | 5.3 | 26.43 |
| SAMM | 1 | 39.8 | 15.8 | 39.7 | 8.0 | 37.60 |
| Dohne | 7 | 38.9 | 15.0 | 38.5 | 5.7 | 21.63 |
The lambs failing to meet the Q Lamb market specifications were slaughtered at Narrogin Agricultural College on the same day as the 2nd draft were slaughtered (20th November). Hot carcase weights and GR tissue depths were measured on all carcases. The WA Q Lamb price schedule was used to assign a value per head for the lambs slaughtered at the College (Table 7).
Table 8
Meat and skin $ returns/head| Genotype | 1st draft | Carc Wt | $/hd* | 2nd draft | Carc Wt | $/hd* | Rejected | Carc Wt | $/hd* | Ave $/hd* |
|---|---|---|---|---|---|---|---|---|---|---|
| Merino | 15 | 21.0 | 71.26 | 18 | 18.9 | 65.67 | 3 | 15.2 | 26.43 | $64.73 |
| SAMM | 35 | 23.4 | 77.86 | 14 | 20.7 | 71.80 | 1 | 15.8 | 37.60 | $75.36 |
| Dohne | 19 | 20.8 | 72.16 | 20 | 19.0 | 65.54 | 7 | 15.0 | 21.63 | $61.59 |
* Price per head includes a $6.00 skin
Table 8 provides a summary of the number of lambs per genotype group slaughtered per draft, their average hot carcase weight and $ returns per head. The SAMM cross progeny were the most valuable over the 2002 season averaging $75.36/lamb whilst the Dohne cross progeny returned the least, $61.59/lamb.
Table 9
Greasy fleece weight, wool quality attributes from mid side fleece samples and the economic value of fleeces of Merino and SAMM and Dohne crossbred ewes.| Genotype | No | Greasy Wt | Micron | CV of micron | Comfort factor | Staple length | Min micron | Max micron | Greasy c/kg | $/hd |
|---|---|---|---|---|---|---|---|---|---|---|
| Merino | 49 | 5.05 | 20.7 | 21.1 | 96.9 | 92.0 | 18.1 | 23.2 | 750 | 37.88 |
| SAMM | 49 | 3.91 | 22.7 | 19.0 | 94.9 | 81.7 | 20.2 | 24.8 | 720 | 28.15 |
| Dohne | 60 | 5.04 | 21.1 | 22.0 | 95.6 | 88.7 | 18.4 | 23.8 | 745 | 37.55 |
The Merino and Dohne cross ewes cut more greasy wool of a finer micron than that produced by the SAMM cross ewe. The CV of micron, indicating the spread of micron variation n relation to the mean was lowest for the SAMM cross ewes and highest for the Dohne cross ewes. The merino ewe produced the most comfortable fleece with the longest staple.The greasy price received (c/kg) was similar between the breeds however, the heavier fleeces ensured that the Merino and Dohne cross ewes returned more per head than the SAMM cross ewes.
Table 10
Basic economic analysis for 100 ewes per breed group utilising reproduction, meat and wool trial data.| Genotype | Marking % | Meat $/hd | Meat returns | Wool $/hd | Wool returns | Total returns | Ave $/hd |
|---|---|---|---|---|---|---|---|
| Merino | 78 | 64.73 | 5048.94 | 37.88 | 3788 | 8836.94 | $88.37 |
| SAMM | 98 | 75.36 | 7385.28 | 28.15 | 2815 | 10200.28 | $102.00 |
| Dohne | 78 | 61.59 | 4804.02 | 37.55 | 3755 | 8559.02 | $85.59 |
The main profit drivers during the 2002 season were the higher marking percentage and carcase value per head. The SAMM cross genotype per 100 ewes returned $2581.26 more than the Dohne cross genotype for meat returns and even though the SAMM cross ewes returned $973 less than the Merino enterprise for wool production, overall the SAMM cross ewes returned $16.41 per ewe more than the Dohne cross enterprise and $13.63 more than the Merino enterprise.
The authors gratefully acknowledge the generous support of Department of Agriculture - Meat Program, Cullam Prime SAMMs, Summerfield Dohne Merino Stud, Hillside Meat Abattoirs, Primaries of WA Pty Ltd, Scanwest Livestock Services and the Narrogin Agricultural College staff and students.
Gracefield SAMM
PO Box 726
Katanning WA 6317
Phone: 08 9821 2181 Fax: 08 9821 4240
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