Body condition score as a selection tool for targeted selective treatment-based nematode control strategies in Merino ewes

Abstract

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Multiple anthelmintic resistance in Southern Brazil sheep flocks

“…This will become worse as none of the monitored properties have more than two drug options to define an effective chemical parasitic control strategy. There is no doubt that this scenario should also be a concern for other regions (GETACHEW et al, 2007;VÁRADY et al, 2011;CORNELIUS et al, 2014;FALZON et al, 2014), especially for those countries that border the state (Argentina and Uruguay).…”

Application of a body condition score index for targeted selective treatment in adult Merino sheep—A modelling study

“…Recent investigations observed that anthelmintic treatments provide a differentially-greater effect in low-BCS ewes in preventing further weight and condition decline (Cornelius et al, 2014), suggesting that BCS can therefore serve as an appropriate index for TST strategies. Earlier studies within this Mediterranean environment also utilised BCS as a TST selection index (Besier et al, 2010).…”

“…This outcome was based on in vivo data from flocks representative of commonly-occurring nutritional and parasitological situations observed in Mediterranean regions of Australia. However, given the results from previous work (Cornelius et al, 2014) it would be advised that sheep below a pre-determined BCS be included in the treatment group to minimise the risk of losses and compromised welfare in low-BCS sheep. The present studies also confirmed that substantial proportions of an adult ewe flock in good body condition could be left untreated without significant production loss, at least where environmental conditions that minimise re-infection from pastures are present.…”

“…One refugia-based strategy under development is Targeted Selective Treatment (TST) which restricts anthelmintic treatment either to the animals judged most likely to suffer significant production loss or health effects if not treated, while leaving others in the group unexposed to anthelmintics (van Wyk and Bath, 2002;Kenyon et al, 2009;Leathwick et al, 2009;Besier, 2012). Recent investigations into the TST concept for non-haematophagous nematodes in small ruminants have considered animal production traits, such as body condition score (BCS) and body weight, as indicators of which individuals in a flock are likely to benefit from anthelmintic treatments (Hoste et al, 2002;Leathwick et al, 2006;Cringoli et al, 2009;Greer et al, 2009;Stafford et al, 2009;Gaba et al, 2010;Cornelius et al, 2014).…”

“…Recent investigations in Western Australia demonstrated that mature sheep (ewes) in the lowest BCS showed a greater BCS response to treatment than their higher BCS counterparts where nutrition was low and worm burdens high (Cornelius et al, 2014). The study by Cornelius et al (2014) confirmed that BCS provides a simple (but effective) index for TST decisions and suggested a benefit in committing the effort required to select sheep on this criterion, as opposed to simple random selection, to minimise the possibility that some sheep in low BCS may escape treatment and suffer adverse consequences. Furthermore, Cornelius et al (2014) also indicated that selecting sheep for treatment on the basis of high faecal worm egg count (WEC) was not an appropriate index, as there was no consistent relationship between egg counts and production-based indices.…”