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document
Predicting the effect of anthelmintic treatment on milk production of dairy cattle in Canada using an Ostertagia ostertagi ELISA from individual milk samples . Gastrointestinal nematodes , such as Ostertagia ostertagi and several species of Cooperia , are ubiquitous in temperate climates and have been shown to have detrimental effects on production in adult dairy cattle . A published meta-analysis demonstrated that overall , producers lose approximately 0.35 kg of milk per parasitized cow per day . Enzyme-linked immunosorbent assays ( ELISAs ) have the ability to quantify nematode infections in cattle , and thus , could be used to estimate the amount of milk production loss due to differing levels of parasitism at the individual cow level . ELISA results from individual cow milk samples were used to predict milk production response following a randomized anthelmintic treatment in a large field trial . To increase statistical power , the data collected from this field trial was pooled with data from two other published field trials to form an individual patient data meta-analysis ( IPDMA ) . The ability to predict the effect of anthelmintic treatment on milk production depends on the level of parasitism quantified by an ELISA measuring milk antibodies against O. ostertagi , and reported as optical density ratios ( ODRs ) . Therefore , the estimates from the interaction between ODR and treatment on milk production were used to determine how well the ODR predicted the response of the treatment . It was anticipated that the relationship between milk production and ODR was unlikely to be linear , so fractional polynomials were applied to the continuous ODR values . The interaction in the field trial showed a trend ( p=0.138 ) toward a beneficial treatment effect when the individual ODR values , measured in late lactation and using Svanovir ( ® ) , were greater than 0.12 . When individual data from two other similar studies were included in an IPDMA , the interaction terms became statistically significant ( p=0.009 ) indicating that there is a beneficial treatment effect when ODR values are slightly elevated . A graph was used to demonstrate the treatment effect ( the estimated difference of kg/cow/day of milk yield between the treated and placebo cows ) , with 95 % confidence intervals , as the ODR values increase . It is important to note that the methods of quantifying the ODR values differed between the three studies in the IPDMA , therefore some caution should be used when using these final estimated values . However , the shape and magnitude of the treatment effects , as well as the other fixed model estimates , were very similar between the field trial and the IPDMA suggesting that any bias would likely be minimal .
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Intervention_Pharmacological
anthelmintic treatment
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Intervention_Physical
Enzyme-linked immunosorbent assays
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Outcome_Physical
milk production of dairy cattle
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Outcome_Physical
milk antibodies
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Outcome_Other
optical density ratios ( ODRs )
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Outcome_Physical
milk production
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Outcome_Other
ODR
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Outcome_Physical
ODR values
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Outcome_Other
ODR values
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Participant_Condition
Gastrointestinal nematodes
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Participant_Condition
Ostertagia ostertagi
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Participant_Condition
several species of Cooperia
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Participant_Age
adult dairy cattle