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Brazilians Evaluate TST Alternatives

Brazilian researchers designed a study to evaluate the effectiveness of both productive and clinical indicators in the targeted selective treatment (TST) of gastrointestinal parasites in growing lambs. Two experiments were carried out between 2015 and 2016.

In the first experiment, lambs (n=70) were raised exclusively on pasture and evaluated from 60 to 180 days of age. In the second experiment, lambs (n=48) were raised on pasture and fed a commercial supplement. They were evaluated from 60 to 150 days of age. Parasitological, productive, and clinical parameters were measured every 14 days.

Lambs were divided into four experimental groups, based on different criterion for anthelmintic treatment. The control group was dewormed every 30 days. In the FAMACHA© group, lambs with FAMACHA© scores of 3, 4, or 5 were dewormed. In the daily weight gain group, lambs that gained less than the average of the control group (minus one standard deviation) were treated. The 4th group combined FAMACHA© scores with average daily gain for making deworming decisions.

In the first experiment, there were no significant differences in weight gain and hematocrit (PVC) among lambs in the different experimental groups. The control group had the lowest FEC. In the second experiment, control lambs had the lowest FEC (1045 epg), while lambs in the FAMACHA© group had the highest (4846 epg).

The group which combined gain with FAMACHA© had the highest average daily gain (200 g/d), while the FAMACHA© group had the lowest (90.5 g/d). The control and weight gain groups were intermediate, 198.4 and 151.8 g/d, respectively. The fewest number of anthelmintic treatments were administered to lambs in the FAMACHA© group. The other non-control groups were similar in the number of treatments administered.

Based on the results of their experiments, the researchers recommend that FAMACHA© not be used as the exclusive criterion for TST in growing lambs, even when Haemonchus contortus is the primary parasite. They further suggest that daily gain can be used effectively in the TST of growing lambs.

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