2007/N03 - Managing Grass Seeds in Weaner Sheep

Summary

The 'Central West Sheep Producers' (CWSP) group evolved from the existing Cumnock Wool4Wealth group (established 2006). Additional members joined this core to establish the CWSP group. Grass seed contamination presents major problems to sheep producers in the central west of NSW. The major problem is the infestation of weaner sheep with Barley, Silver, Spear and Wire grass seeds over their first summer. The majority of weaner sheep in the region are born during the late winter/early spring and graze grass seed contaminated pastures during November to February. This has lead to problems such as reduced weight gains, eye problems, wool, skin and meat contamination. 
To address the problem most producers have traditionally prematurely shorn weaner sheep to minimise the pickup of grass seeds over their first summer. This has been effective but has incurred severe discounts for short wool from their first shearing and has increased the cost of producing both wool and sheep meat. Alternative management techniques such as preparing grass seed free (or reduced) pastures, using coats to reduce pickup, and using Bioclip shearing (pre pick-up) to remove any chance of grass seed pickup; has been investigated in an adhoc manner. The problem is to identify what management systems provide the most cost effective and profitable method of managing grass seeds in both prime lamb and merino weaner sheep. 
This PIRD project's overall aim was to optimise both meat production and life time wool/reproductive performance from merino & XB weaner sheep through the effective and economic management of grass seed problem pastures. Through the control of seed contamination on growing lambs, the CWSP group set out to: Increase prime lamb and merino carcass turn off weights from an average of 18kg to 20.7kg carcass weight. 
Reduce the number of lambs contaminated by seeds (% with grass seed penetration) from 25% to less than 10%. 
To increase the net value of wool production (after the cost of harvesting) from an estimated $38 to $44 over their first 28 months of life. 
For all group members to identify to what extent seed contamination is reducing production and profitability on their properties. 
To have all 10 group members develop a cost effective strategy to manage the impact of seed contamination on either their wool or lamb producing enterprises. 

The project methodology was developed to address the issues and provide practical solutions to achieve these objectives. The overall project was set-up to be undertaken in two stages. The first stage of the trial investigated the effectiveness of reduced wool length in managing the grass seed problem, as earlier work displayed the benefits of shearing to reduce wool length prior to the main period of grass seed pickup in late spring and summer. Wool removal methods were compared by investigating the biological effectiveness of the Bioclip method of wool harvesting to conventional shearing and not shearing, in reducing the impact of grass seed contamination on wool and meat production in weaners. 
The second stage aimed to collate both field data on the levels of problem seed species contamination of pastures in the Cumnock/Yeoval district, and do co-operator trials to determine benchmarks and thresholds for the pro-active management of problematic species. Using co-operator trials a combination of strategic (preparing seed-safe pastures) and tactical methods (e.g. Bioclip or shearing) were to be tested in order to determine pasture composition benchmarks and economic thresholds. The project methodology is detailed in the following section.