A critical review and meta-analysis of the magnitude of the effect of anthelmintic use on stocker calf production parameters in Northern US States

- A critical review and meta-analysis.
- Aimed at quantifying the effect of use of anthelmintic products on production metrics in stockers.
- Compared average daily gain in stockers in northern US climates, treated compared with placebo.
- Conclusion was made that anthelmintic use is associated with an increased weight gain.
- However, reporting was poor throughout all studies included in the review.

Parasitism of the gastrointestinal tract of cattle leads to diminished health and productivity of grazing livestock. Anthelmintics are used to decrease parasite loads in cattle for improved weight gain. This critical review and meta-analysis aims to quantify the magnitude of the effect of use of anthelmintic products on production metrics in beef stocker calves. Four databases were searched in March 2013. Eligible studies compared average daily gain (ADG), or weight gain in stocker calves in northern climates of the United States that received anthelmintic treatments compared with placebo or an alternative anthelmintic treatment. Study results were extracted, and where possible, summary effect measures were calculated. Of 512 citations identified by the search, 9 manuscripts with 23 relevant individual studies were selected. Risk of bias was assessed for all studies included in the review and assessed to be unclear for the majority of the studies. There were 23 studies that assessed the magnitude of effect of anthelmintic use on ADG (summary mean difference in ADG = 0.05 kg (50 g), 95% CI = 0.03-0.07 kg, p < 0.00001). The magnitude of weight gain associated with anthelmintic use could not be assessed, as measures of precision (standard errors or standard deviations) were not reported in these studies. Overall, the conclusion was made that anthelmintic use is associated with an increased weight gain. However, the approach to reporting employed by authors for this type of study means that many studies could not be included in the meta-analysis and the magnitude of effect not determined.