Evaluating the performance of Dorper, Damara, Wiltshire Horn and Merino breeds in the low rainfall wheatbelt of Western Australia Tanya Kilminster

Transcription

1 Evaluating the performance of Dorper, Damara, Wiltshire Horn and Merino breeds in the low rainfall wheatbelt of Western Australia Tanya Kilminster Department of Agriculture and Food WA, Merredin In the March 2005 edition of the Ovine Observer we reported on a ewe productivity trial involving new breeds commencing at the Department of Agriculture and Food WA s Merredin Research Station (MRS). Ewes from four breeds, the Dorper, Damara, Wiltshire Horn and Merino are included in the trial. The trial aims to evaluate the productivity of the ewes by measuring reproductive performance, lamb survival and lamb production of all ewe breed groups. An economic analysis of the different enterprises will take place on completion of the trial. The ewes are being run as one mob for three years to assess the productivity of the various ewes under the same environment and management. The sheep producers who donated their animals to the trial will be able to benchmark the genetic performance of their sheep flock. Knowing their flocks reproduction ability and lamb productivity will enable them to make more informed decisions on meeting breeding objectives and improving flock profitability. A Merino link team is included to enable results from this trial to be compared with other past and future linked ewe productivity trials. The information obtained from this trial and from other linked trials will also allow across-flock comparisons to be made. General management The ewe mob is being run according to normal practice for eastern wheatbelt farming systems, grazing stubbles after harvest and volunteer and improved pastures during the growing season with supplementary feeding during feed gap periods. The ewes are regularly weighed and condition scored to assess their general performance and worm egg counts are monitored throughout the trial to determine the requirement for drenching and as another measure of the flock s general health. Each year the ewes will be mated to one sire breed and the ewe performance will be measured in terms of reproductive performance including conception and potential lambing rates, marking percentages and the percentage of lambs surviving to market from each team. Measurements of wool for the Merino team will be collected at shearing each year. Lambs produced each year will be weighed and condition scored regularly until market weights are achieved.

2 Year One 2005 Forty three Dorper, 48 Damara, 48 Wiltshire Horn and 48 Merino (bare shorn) ewe weaners from a number of Western Australian flocks were brought to the MRS in February The ewes were mated to Damara rams at 3% for 6 weeks in March, when the average age of the ewes was 8 to 9 months. The ewes were pregnancy scanned in May and in July the Merino ewes were crutched. Prior to lambing in August, the ewes were drafted into their breed groups and placed into four lambing paddocks. Lambing began in August and was complete by mid-september. One hundred and fifty days after joining the lambs were identified to breed group, marked, vaccinated (3 in 1), weighed and condition scored, then all ewes and lambs were combined into one mob. Lambs were weaned four weeks later and a booster vaccination was given. The lambs were weighed and condition scored monthly until the lambs were approximately five months old. The ewes continued to be weighed and condition scored regularly to monitor their performance. The Merino ewes were shorn in January 2006 at the end of the first year of the trial. Mid side samples were collected and analysed for fibre diameter, yield, staple length and strength. Greasy fleece weight was measured and the fleece value determined. Core samples from the wool bales are being analysed to determine the extent of dark and medullated fibre contamination for the Merino ewes running with fleece shedding sheep. Year Two 2006 The ewes were mated to Dorper rams at 2% for 6 weeks from mid-february. The average age of the ewes was 20 months. In all other respects the same protocol as followed in year one is being repeated. Management issues No drenching was required for ewes or lambs as worm egg counts were below 300 eggs per gram in all monitoring. Two Merino ewes were culled from trial at beginning due to being poor animals and three Dorper ewes died in year one, 2 from unknown causes and 1 was euthanased due to a severe rectal prolapse. Two Dorper ewes have since been observed with small, intermittent rectal prolapses. One Damara ewe had severe fly strike on the tail, the ewe took some time to recover but is now fully fit and one Damara ram lamb died post-marking of unknown causes. Results The trial has now been running for eighteen months. Results from year one show that ewe lambs in good condition, mated during the natural breeding season (February to April), can produce lambs. Previous research has shown that maiden ewes below 40 kg or at or below condition score 2 will have a low reproductive rate or may not cycle. The differences in liveweights in the ewe lambs is likely to be the main cause of the differences in reproductive performance between breeds (Table 1). Using poly-oestrous breeds such as the Dorper and Damara, may enable farmers to produce more lambs out of season and at a younger age, which can provide an extra income to the farm enterprise. Table 1. Ewe weights and condition scores at the first joining, numbers of ewes with zero, single or multiple foetuses at scanning, ewe conception rates, potential lambs per ewes mated, lamb mortalities and lambs marked

3 Dam Dorper Damara Wiltshire Horn Merino Number of ewes Liveweight (kg) Condition Score Dry ewes Single foetus Multiple foetus Conception rates (%) 88 93* 0 22 Potential lambs 42 47* 0 10 Potential lamb rates (%) * 0 22 Lamb mortalities Lambs marked Marking percentage (%) 81 71* 0 13 Note: 1. All ewes scanned with multiple foetuses were assumed to have twins. 2. *Two Damara ewes were not pregnancy scanned so potential lamb numbers, conception rates and potential lamb rates were determined using 46 ewes (scanned) while actual marking rates were determined using 48 ewes (mated). There was a 20 30% difference between potential lambs measured by pregnancy scanning and actual lambs marked in year one (Table 1), despite very low lamb mortalities being observed between lambing and marking. The high rate of reproductive loss identified at this stage may highlight an opportunity to improve reproductive performance of ewe lambs if the cause of the problem can be identified and overcome. Table 2. Lamb weights and growth rates for the lambs dropped in 2005 sired by Damara rams

4 Ram lambs Ewe lambs Dam Damara Dorper Merino Damara Dorper Merino 40 day weight (kg) 5 month weight (kg) Growth rate 40 days to 5 months (g/h/d) The wool was classed as AAAM with no discounts. The spot price for the wool sold through the Australian Wool Exchange in Fremantle (AWEX report 13 January), was 666 cents/kg clean. To determine the value of the wool the total amount of wool greasy ( kg) was multiplied by the yield (67.6%) and divided by 100, this value was then multiplied by the wool price clean to give the total value for the wool fleeces as $1120. Table 3. The average wool measurements for the Merino team, 18 month-old hoggets with 12 months wool Greasy fleece weight (kg) 5.4 Fibre diameter (µm) 20.3 Yield (%) 67.6 CV (%) 19.0 Comfort factor (%) 98.8 Staple length (mm) 92.3 Staple strength (N/ktx) 28.2 A local stock agent valued the lambs and provided an on-farm price for their sale in February All ram lambs were valued at $52/head and were saleable to the live export trade or domestic saleyards while the ewe lambs were valued at $40/head and saleable only to the domestic saleyards. Table 4. Lambs surviving to market and the spot price on day of sale Breed group Lamb survival Number Live weight (kg) Market value ($) Total ($) Damara rams 14/ Damara ewes 19/ Dorper x Damara rams 14/ Dorper x Damara ewes 20/ Merino x Damara rams 3/ Merino x Damara ewes 3/ Total 73 $3292

5 A basic economic comparison of the four breeds using data from year one has shown that the mating of ewe weaners from earlier maturing breeds producing 70% lambs marked will provide a greater income than from a later maturing meat breed such as the Wiltshire Horn or from Merinos producing wool only. Table 5. Profits per team for year one Costs Dorper Damara Wiltshire Horn Merino Shearing ($4.80/h) Crutching ($1/h) Transport ($2.30/h) Revenue Wool sales Lamb sales Profit $1450 $1412 $0 $1115 Note: Lamb transport costs are from Merredin to the Midland saleyards Results from year two show that ewes in good condition (scores 2.8 to 3.2) have the potential to produce greater than 100% lambing when mated in February and March in this region (Table 6). The low pregnancy rate for the Damara ewes is attributed to the fat tail impeding mating by a non-damara sire. Ten of the 17 pregnant ewes have docked tails (a management technique performed by the donating producer). Three of the remaining seven pregnant ewes were only in early pregnancy, indicating they were mated late in the joining period. This suggests the rams mated these ewes once the other ewes were already mated. We do not recommend tail docking as a suitable management technique when considering joining fat tail ewes to non-damara rams however this result does pose some questions. Some suggestions on managing mating Damara ewes to non-damara rams include mating single breeds, using experienced rams or higher ram rates or joining the ewes for a longer period which may be a practical technique for producers who run Damaras and Dorpers with rams year-round. Due to the low conception rate for the Damara ewes, we have rejoined them to Damara rams at 2% to determine if these ewes are able to conceive.

6 Table 6. Ewe weights and condition scores at the second joining in 2006, numbers of ewes with zero, single or multiple foetuses at scanning, ewe conception rates and potential lambs per ewes mated Dam Dorper Damara Wiltshire Horn Merino Number of ewes Liveweight (kg) Condition score Dry ewes Single foetus Multiple foetus Conception rates (%) Potential lambs Potential lamb rates (%) Note: All ewes scanned with multiple foetuses were assumed to have twins. This trial is only in its second year. By the conclusion of the trial at the end of its third year the trial will provide sheep farmers in the low rainfall areas of Australia with objective information comparing the reproductive and economic performance of these alternative breeds in meat and combined meat and wool production systems. The Department of Agriculture and Food gratefully acknowledge Jason and Kim Batten, Lance Ludgate, David Thorn, Tamesha Gardner, Adrian Veitch/ Aaron Foster, John Hall, Keryn Cooper, David Auld, the Manjimup Research Station and Badgingarra Research Station for the kind donation of the ewes and rams to this trial.