Integrated parasite management for sheep reduces the effects of gastrointestinal nematodes on the Northern Tablelands of New South Wales

Abstract

An experiment was conducted over 2 years on six commercial farms to quantify the costs of gastrointestinal nematode parasitism on grazing Merino ewes on the Northern Tablelands of New South Wales. To determine the effect of worm management practices, three farms implemented integrated parasite management (IPM) strategies and three farms continued to implement regionally typical industry practice (TYP). On each farm, 120 ewes born in 2006 and 120 mature age ewes were selected at shearing in 2007. Of these, 60 in each flock were serially treated with anthelmintics (CAP treatment) to suppress worm populations and the other 60 ewes were managed according to their respective farm management strategies (NOCAP treatment). Among NOCAP ewes, worm egg counts were significantly reduced over both years by IPM compared with TYP despite IPM farms requiring fewer anthelmintic treatments (3.5 vs 4.5 per year). In Year 1, mortality of sheep because of worms (CAP vs NOCAP) was significant on TYP farms (10.5%, P < 0.01) but was not apparent on IPM farms. Throughout the study, NOCAP ewes had significantly lower growth rates (-2.8 AE 0.1 kg/year, P < 0.01), produced less greasy wool (-170 AE 20 g, P < 0.01) and had reduced fibre diameter (-0.28 AE 0.05 mm, P < 0.01) when compared with CAP ewes. These effects were apparent for both TYP and IPM management. The results confirm the significant production loss caused by worms in a northern, summer rainfall region and show that IPM reduces the effect of worms and frequency of anthelmintic treatment compared with typical methods currently used by the industry.

Environmental and genetic factors affecting faecal worm egg counts in Merinos divergently selected for reproduction

“…It results in substantial losses through reduced growth rates, poor production performance and reduced reproductive efficiency (Chiezey et al, 2008;Kelly et al, 2010;Van Houtert & Sykes, 2010). There is thus reduced overall production efficiency stemming from high costs of anthelmintic drenches used for prevention and treatment (Pathak & Tiwari, 2013), and, in severe cases, the death of infested animals (Barger & Cox, 1984).…”

Grazing systems and worm control in sheep: a long-term case study involving three management systems with analysis of factors influencing faecal worm egg count

“…To prevent such spikes, the frequency of WEC sampling during the high-risk months in late spring and summer may need to be increased, and more sophisticated treatment thresholds adopted. Adoption of a tactical integrated parasite management program based on routine WEC monitoring has been shown in other studies to reduce the adverse impact of worms and frequency of anthelmintic treatment (Kelly et al 2010) and such an IPM approach is central to the recommendations of WormBoss, Australia's national sheep worm control program (http://www. wormboss.com.au/, accessed 1 April 2013).…”

“…Resistance to anthelmintic drenches is a major and widespread problem that is getting worse (Love 2012). Gastrointestinal worm infection is the most economically important disease of sheep in Australia (McLeod 1995;Sackett et al 2006) and the impact has recently been described in detail for the Northern Tablelands of NSW by Kelly et al (2010). The major worm species in this region are the abomasal Haemonchus contortus (Barber's pole worm) and the small intestinal Trichostrongylus colubriformis (Black scour worm) with some presence of other species including the abomasal Teladorsagia circumcincta (small brown stomach worm).…”

Findings from an ovine parasitological monitoring service provided by a rural veterinary practice in New South Wales, Australia

“…Gastrointestinal nematodiasis represents a key area of economic loss to the Australian sheep industry, estimated in 2006 as A$369 million per annum . In winter and year‐round rainfall zones where the major internal parasites are Trichostrongylus spp.…”

“…Production losses may be attributable to reduced milk and wool production, compromised weight gain and deaths . Costs are also associated with the methods used to control gastrointestinal parasitism, particularly the use of anthelmintics . The reliance on anthelmintics has led to the development of widespread resistance, with more than 90% of Australian sheep displaying resistance to at least one anthelmintic class in their worm populations …”