04/W01 Increase Merino Lambs Weaned

Summary

​The aim of PIRD WA/01 was to improve the reproductive performance and efficiency of Merino ewes mated from early February to mid March in the Great Southern region of Western Australia. In light of the recent interests of animal activist groups in the livestock industry, it was important to achieve these goals in a 'clean, green and ethical' manner. The study therefore attempted to synchronize the timing of reproductive events using the ''ram or male effect'' so ''focused feeding'' strategies could be implemented at mating to improve fertility and fecundity, and just prior to the commencement of lambing to enhance lamb survival and quality. 
A total of 9315 ewes where mated on five farms within the Kojonup, Woodanilling and Broomehill Shires of Western Australia between early February and mid March in 2004 and 2005.  Ewe age varied from 2.5 to 4.5 across the five farms.  Trial mobs were selected and allocated to a control or treatment group.  In 2004 the trial mobs were also tagged using Primarylink Technology electronic ear tags.  If mixed age groups were used the proportion of ages were kept consistent across the treatment and control groups.  Treatment ewes were teased with testosterone injected wethers at 3% for 6 weeks prior to mating.  Teasers remained in with the treatment ewes during the 32 day mating period.  Rams were put in at 3% in treatment groups and normal percentages in control groups.  T1 ewes were fed a Lupin supplement, 500g/head/day for 14 days, during mating in 2004 and a Lupin/Oat (300g Lupins:200g Oat supplement every second day for a 12 day period in the 2005 mating.  After pregnancy scanning all ewes where allocated to either an early or a late group (2004 only) and recorded as single, twin or dry.  All dry ewes were drafted off at pregnancy scanning and took no further part in the study.   
At lambing single bearing treatment ewes where run as a separate group, as were the control group which consisted of a mixture of single and twin bearing ewes. Twin bearing treatment ewes were split into either a fodder and barley group, a barley only group or a normal pasture group depending on the development of the fodder crop, individual farm management system and group mob size. All treatment twin mobs remained separate until marking.  After marking and initial lamb body weighing and identification, single and twin treatment groups were run together.  In 2004 a follow up body weight was recorded on 20 individually identified lambs from each treatment and control group at weaning.
In summary, the ram effect is capable of synchronising the mating of Merino ewes as late as mid-February in the Great Southern region of Western Australia.  Nutrition supplements implemented at strategic times during pregnancy can lift the reproductive performance of Merino ewes and the quality and number of twin lambs born.  An economic analysis of this strategy shows that a profitable response to teasing and flushing was achieved more often than from managing twin bearing ewes.  These results suggest that further development of the protocol is required to develop a 'cheaper' system before a profitable response is consistently achieved.