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Beyond the Bale : September 2019
higher pasture availability with a predominance of perennial pasture species tends to be associated with more dag. In south-western Australia, the risk of dag increases in late winter or early spring with higher availability of mixed pastures (annual grasses and legumes).” There are also circumstances in which scouring is associated with low worm burdens. “Hypersensitivity to recently-ingested larval worms has been shown to occur in south-eastern and south-western Australia, chiefly in sheep old enough to have developed immunity to worms,” Dr Larsen said. “Worm hypersensitivity scouring should be considered when all other potential causes of scouring have been ruled out in sheep with low faecal worm egg counts. Over time, breeding programs that select against dag will help minimise the problem.” It is noteworthy that the ASBVs for worm resistance and for dag formation are different, and that selection for both traits needs to be included in breeding programs to help move towards lower dag scores in a flock. Dr Jacobson said that when faecal worm egg counts are low, the presence of other risk factors should be considered and sampling for protozoa or bacteria may be warranted. “Scouring due to bacterial or protozoal infections may require veterinary treatments, or changes to management routines and plans for paddock use,” she said. “Protozoa and bacteria infections rarely cause scouring in older sheep. For older sheep with low worm egg counts, close examination of the diet of the sheep may uncover a cause for scouring. “The relationship between pasture and scouring is complicated. The specific nutritional components of pasture that may trigger scouring have not been clearly identified. There also appears to be a complex relationship between diet and infections that influence severity of scouring, but these have not been well studied. Nutritional scouring is often a diagnosis of last resort, after other common causes of scouring have been excluded.” Two new documents from AWI are available to help with managing dag: DEALING WITH DAG ADVISOR MANUAL This 44-page manual reviews the causes, diagnosis, management and treatment of dags in sheep and provides a guide for people helping woolgrowers to manage and prevent scouring and dag formation in their animals. DEALING WITH DAGS – A FACTSHEET FOR WOOLGROWERS A two-page summary document for woolgrowers of the Dealing with Dag manual. Sudden changes in diet, grain feeding and specific pasture plants may be associated with scouring. Due to the many and varied factors involved, the best option for producers is to seek expert advice from an animal health advisor or veterinarian. Regardless of the cause of scouring in sheep, it is important to remember that in southern Australia scouring and dag formation are the major risk factor for breech flystrike, making dealing with dags a priority for sheep producers. MORE INFORMATION The 44-page Dealing with Dag manual and 2-page fact sheet are available at www.wool.com/flystrikelatest or by phoning the AWI Helpline on 1800 070 099. For more information, contact Eastern Australia: Dr John Larsen 0408 534 361 and Western Australia: Dr Brown Besier 0427 778 406 or Dr Caroline Jacobson 0418 953 173. ITEM DAG SCORE 0 1 2 3 4 5 A. Cost of crutching (c/head) 10 20 30 60 90 90 B. Dag-weight (g) 68 115 204 380 737 1225 C. Wool yield (%) 36.4 28.5 22.9 19.8 13.6 14.4 D. Clean wool in crutchings (g) (B x C) 25 33 47 75 100 176 E. Foregone value of crutched wool* (c/head) 14 19 42 67 89 156 TOTAL COST OF DAG (C/HEAD) (A + E) 24 39 72 139 179 246 * Price of fleece wool 1200 c/kg clean, crutchings from ewes with a dag score ≤ 1 and ≥2 are 52% and 26% of this price, respectively. TABLE 1. THE TOTAL COST OF DAG FOR EWES IN EACH DAG SCORE CATEGORY. Adapted from Larsen et al. (1995a) using 2019 wool prices and 2018/2019 recommended wages 55 ON FARM
In the Shops - September 2019