L.PDS.1905 - PDS: The Sense in Supplementation

Summary

During a previous PDS on lamb finishing systems it was identified that for one of the pasture finishing systems (Cobana) the use of energy rich supplements had enabled more complete utilisation of the available herbage without compromising per head animal performance. Despite the extra cost of feeding this strategy had enabled larger profits per ha exceeding the profit achieved on most other forage systems which were tested in the absence of feed supplements.

It was decided to test the utility of feeding supplements in lamb finishing enterprises to more fully utilise pasture biomass and increase profits across a range of forage types including grass based pasture, Lucerne and forage brassicas. Many Monaro producers now seek to finish lambs to slaughter specification on specialist forages but often they are moved off paddocks before the biomass is fully utilised. The work is intended to show the cost benefit to feeding supplements at pasture achieved through being able to finish more lambs per ha and improve the feed efficiency of the forage base. The work was to be conducted over two summers and commenced in December 2020.

Objectives

The aim of this work was to demonstrate the benefit of supplementing lambs at pasture through the ability to retain lambs longer and utilise the sources of forage to levels below the benchmark for good unsupplemented lamb growth without compromising the ongoing growth of the lambs.

While previous work had suggested higher utilisation of pasture could be achieved by using energy based supplements this work was done in more average to below average seasonal conditions.

The extraordinary good seasonal conditions of Summer 2020-21 created two conditions which made it difficult to show any benefit to supplementation due to the constraints to stock numbers carried forward from the long run of poor seasons preceding it. The cooperating farmers found it difficult to

Manage biomass properly before lamb entry

Stock at an appropriate density to cause the biomass to decline over the grazing period.

Overall there was no clear benefit in the kg/ha of lambs produced.

Key findings

For all demonstrations where animals were properly randomised between treatments there was no difference in weight gain between supplemented and un-supplemented lambs. This is undoubtedly related to the very good seasonal conditions experienced which meant that the quality of the herbage diet of the lambs was already as good or better than the supplements provided. As a result the lambs had very low voluntary intake of supplements and no difference in weight gained.

Benefits to industry

While the premise of routine provision of supplements to lambs was not useful under the prevailing seasonal conditions this does not mean that the strategy would not be successful in more normal seasons or for circumstances where the stock numbers could be bolstered to ensure much higher utilisation of available herbage.

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

Use of supplements to maintain animal performance while achieving higher utilisation of pasture is still likely to be effective but to be tested properly it would be best done in more average to below average seasonal condition and with sufficient stock numbers to properly test the hypothesis. Results are likely to be more definitive if an additional treatment was included so that the lambs could be run at a much higher stock density in addition to the baseline stock density.