L.PDS.1803 - To wean or not to wean

Summary

The St Arnaud BestWool/BestLamb (BWBL) group were interested to investigate whether weaning their autumn drop prime lambs at 12 weeks of age would lead to production benefits or cause any adverse effects to lamb weight gain. In 2019, the group embarked on a two-year farm demonstration co-funded by Agriculture Victoria and Meat & Livestock Australia (MLA) to weigh up the benefits of weaning.

Many producers in the Wimmera region sell terminal lambs directly from the ewe, however weaning is a common practice for replacement (maternal) ewe lambs. Some of the group members were concerned that with increasing climate variability, unreliable water availability and high fodder costs (culminating in variable rainfall and annual pasture production), lamb growth rates could be compromised through the weaning process. Although producers have been sceptical about weaning terminal lambs, all have looked at or considered alternative systems and/or more efficient finishing systems.

Objectives

The aim of this demonstration was to evaluate if there are production benefits for both ewes and lambs by weaning them at 12-14 weeks from the start of lambing as opposed to not weaning the lambs and leaving them on the ewes until they are at a marketable kill weight. The specific objectives were to:
1. Demonstrate the impact of weaning lambs on lamb growth rate.
(Hypothesis: 10% increase in growth rate of weaned versus un-weaned lambs)
This was not fully achieved. On some farms and across years weaned lamb growth rate outperformed the unweaned lambs; however, this growth rate was not statistically significant. The results of the trial did, however, demonstrate that there was no adverse outcome in growth rates of weaned lambs compared to unweaned lambs.
2. Demonstrate the impact on carcase weight at sale date of weaned and unweaned lambs.
(Hypothesis: Higher carcase weight in weaned versus un-weaned lambs at sale date)
This was not achieved. There was no significant difference in the carcass weight of weaned lambs compare to unweaned lambs. The data set was small and only contained lambs from one property and one year. Further investigation into carcase traits between weaned and unweaned lambs that incorporates a larger sample size across multiple genetic lines and seasons is warranted.
3. Demonstrate the impact on dressing % of weaned and unweaned lamb carcases
(Hypothesis: No difference in the dressing % of weaned or unweaned carcases)
This was achieved. There was no significant difference in the lean meat yield between weaned and unweaned lambs, although the sample size was small and data was only obtained for one property in one year.
4. Demonstrate the impact on ewe reproductive rate of weaning compared to not weaning.
(Hypothesis: 5% improvement in reproductive rate of ewes that had lambs weaned vs ewes that did not have lambs weaned at their subsequent mating.)
This was not achieved. On-farm management practices of the participants meant that ewes that had lambs weaned versus ewes that carried lambs at foot further through the investigation had to be co-mingled over the summer period and these ewes were not adequately identified. As a result, at scanning, ewes that were enrolled in the trial could not be easily identified.
5. To increase skills in condition scoring ewes, lamb management and FOO estimation.
This was achieved as evidenced by pre and post surveys suggesting an increase in skills from 4/10 to 7.3/10. However COVID-19 prevented three planned producer meetings, so less time was spent on these activities than was hoped.
6. To increase awareness and adoption of weaning practices for the benefits of lamb production and ewe management.
This was achieved through three group meetings, one webinar, one radio article, two online presentations and one media article. All producer hosts have adopted weaning and their knowledge of weaning practices had increased from 3.9/10 to 8.1/10.

Key findings

The project demonstrated that there were no adverse outcomes from weaning lambs and highlighted that the perceived disadvantages of weaning lambs are unfounded. The results showed that growth, weight, dressing percentage and lean meat yield of weaned lambs were not negatively affected by weaning compared to unweaned lambs. Anecdotally, producers found weaning led to better, simpler management of ewes and lambs and all producers involved in the demonstration had adopted weaning practices or intended to after the second year of the project.

Benefits to industry

The information obtained from this demonstration can be used to inform other producers across the region that there are no penalties for weaning lambs. In fact, participants of this study found there were additional benefits to weaning lambs such as managing spring pastures effectively, allowing ewes to regain condition before summer and having flexibility in their lamb marketing strategy. The results provide grounds for adoption of weaning, leading to improved ewe and lamb management.

MLA action

MLA continues to deliver the Producer Demonstration Site (PDS) program, supporting livestock producers working in peer-to-peer groups to pursue new skills, knowledge and management practices applicable to their own commercial livestock production systems.

Future research

The protocols and benefits of weaning lambs have been well established in the published literature. In terms of future research specifically related to this project, identifying differences from sire effects and time of birth and their impact on growth rates to weaning would enhance the accuracy of the data collected. For example, some lambs could have been born to higher growth rate sires or born in the first few days of lambing and this could have an effect on growth to weaning. Furthermore, assessing the condition score of ewes at various time points post weaning to pre-joining could show differences in conception rate between ewes that have had lambs weaned versus ewes that have had lambs unweaned. Additionally, recording when ewes lamb throughout the lambing process (eg. early (first two weeks of lambing) versus late (last three weeks of lambing)) might allow identification of which lambs to wean first to optimise greater weaner survival outcomes or to target specific meat or re-stocker markets.

Further results extension and communication work with livestock agents would have been advantageous not only in the St Arnaud district but also further afield. Additionally, abattoir tours for group members and those outside the group to visualise the difference between weaned and unweaned lambs would have been well received.