Do<strong>rp</strong>e<strong>rn</strong><strong>uus</strong> <strong>•</strong> Do<strong>rp</strong>er news 2012 36
This article was placed in a magazine called “Prograzier” and passed on from Dr. Adrian Veitch (from Australia) to Gideon Vivier and then to me. I hope that you will find it interesting. UNDERSTANDING HOW MATURE EWE WEIGHT affects your production system and can have a significant influence on whole farm profits Size does matter but what’s right for ewe? Andrew Kennedy, PhD student with the University of WA and the Sheep CRC has spent the past year investigating the relationship between mature ewe size and whole farm profitability. From this word, he has produced some useful guidelines to help producers unlock their flocks’ potential. “Leading producers who are pushing the limits are already aware that mature ewe size impacts on profitability, but it is a hard thing to quantify because it’s a trade-off between ewe efficiency and lamb growth,” he said. “We want to understand how selecting for growth affects mature size in mate<strong>rn</strong>al lines, as selecting for growth and muscling is providing some big gains in reproduction and resilience, particularly for Merinos.” According to Sheep CRC Program Leader and WA Department of Agriculture and Food Senior Scientist Dr Andrew Thompson the average live weights of Merino and cross-bred ewes have increased between by 6 % and 8 %, respectively, since 1990. Andrew Kennedy said that, given ewes consumed 60 – 70 % of their energy in maintenance alone each year, any compromise in ewe efficiency was likely to affect farm profit. Mature ewe size and profit Andrew’s bioeconomic modeling was based on ‘n selfreplacing Merino ente<strong>rp</strong>rise producing slaughter lambs in Victoria’s weste<strong>rn</strong> district (typically high rainfall with a long growing season). By exploring the relationship between ewe size and profit, Andrew found that a moderate-sized 60kg ewe was the standout performer under those conditions (Table 1). “In general, profit was maximized when stocking rates were between 12 and 14 ewes/ha, ewe mature size was between 60 kg and 70 kg, potential reproductive rate was between 125 % and 150 % and lambs were marketed at 45 – 50kg live weight (22-24 kg carcass weight),” he said. In practical terms, he said there was little difference in the outcome for ewes between 60 kg and 80 kg, with retu<strong>rn</strong>s varying by only 2 – 3 %. As ewes started to exceed 80 kg, their maintenance feed costs began significantly eating into profits. Conversely, ewes below 60 kg required more time and feed to finish their lambs, as they lacked the growth potential to meet market specifications. “The research shows that under the reasonably ideal conditions of our Weste<strong>rn</strong> District ente<strong>rp</strong>rise, the 60 kg ewe produced a superior result and the 80 kg-plus ewes were far more expensive to maintain,” he said. “However, producers need to consider those results in terms of their own environments and ente<strong>rp</strong>rise needs. The 80 kg-plus ewes had the lowest lamb finishing costs. If you’re in an area that has a tougher climate and shorter growing periods, then a bigger ewe, run at a lower stocking rate, might well ea<strong>rn</strong> you better dividends. We need to continue to explore this.” Andrew recommended that producers know their mature ewe weight and be aware of the available options to increase profit. “If you have a smaller ewe, there may be scope to increase stocking rate. However, if you have a large ewe already at maximum stocking rate, then improving the reproductive rate of these ewes may be your next goal.” Mature size (also referred to as standard reference weight) is defined as the weight of the animal when skeletal development is complete; the ewe is not pregnant, minus wool weight and in condition score 3. “This is the criteria producers need to keep in mind when thinking about mature size, commercially. I think producers see 90 – 100 kg ewes going over the scales and get worried, but often these ewes are probably well above condition score 3 or carrying twins,” Andrew said. “Producers wishing to manage mature size can use the adult weight Australian Sheep Breeding Value (ASBV) when selecting rams in their breeding program or when purchasing rams at sale.” Ewe size and farm labour Andrew said ewe size also had ramifications for ente<strong>rp</strong>rise labour costs, with larger ewes requiring more feed, time and labour to maintain. PhD student Gus Rose, who focused on labour issues facing the WA sheep industry for his Masters at the University of WA, said the right type and size of ewe could decrease labour inputs and increase profitability. “There is a need to identify the genetic and economic 37 Do<strong>rp</strong>e<strong>rn</strong><strong>uus</strong> <strong>•</strong> Do<strong>rp</strong>er news 2012