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

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.

A critical review and meta-analysis of the efficacy of whole-cell killed Tritrichomonas foetus vaccines in beef cattle.

This review assesses the efficacy of whole cell Tritrichomonas foetus vaccine to prevent and treat trichomoniasis in beef cattle. Three databases were searched in June 2012. Eligible studies compared infection risk, open risk, and abortion risk in heifers or infection risk in bulls that received vaccine compared with no vaccine. Study results were extracted, summary effect measures were calculated, and the quality of the evidence was assessed. From 334 citations identified, 10 were relevant to the review. For heifers, there was limited evidence of moderate quality to assess the impact of vaccination on infection risk (RR, 0.89; P = .16; 95% CI, 0.76-1.05; 6 randomized and 4 nonrandomized studies; 251 animals) and open risk (RR, 0.80; P = .06; 95% CI, 0.63-1.01; 6 randomized and 5 nonrandomized studies; 570 animals). The quality of the body of work describing the impact of vaccination on abortion risk was low (summary RR, 0.57; P = .0003; 95% CI, 0.42-0.78; 3 randomized and 2 nonrandomized studies; 176 animals). The quality of evidence was very low for duration of infection (mean difference, -23.42; P = .003; 95% CI, -38.36 to -7.85; 2 randomized and 3 nonrandomized studies; 163 animals). Although the summary effect measures suggest a benefit to vaccination, due to publication bias the effect reported here is likely an over estimate of efficacy. For bull-associated outcomes, the evidence base was low or very low quality.