Comparison of three methods for gastrointestinal nematode diagnosis determination in grazing dairy cattle in relation to milk production

MEJIA,M.E.; PERRI, A.E.; LICOFF, N.; MIGLIERINA, M.M.; CSEH.,S; ORNSTEIN AM; BECU VILLALOBOS, DAMASIA; LACAU-MENGIDO, I. M

VETERINARY PARASITOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2011 vol. 183 p. 174 - 177

0304-4017

Development of resistance to anthelmintic drugs has motivated the search for diagnostic methods to identify animals for targeted selective treatments. We compared three methods for the diagnosis of nematode infection in relation to milk production in a fully grazingdairy herd of 150 cows in the humid Pampa (Argentina). Animals had feces, blood and milksampled during the first postpartum month for EPG, pepsinogen and anti-Ostertagia antibodydetermination, respectively. With the results obtained two groups of cows, divided inhigh and low parasite burden, were conformed for each method, and milk production wasthen compared between groups. When cows were separated by the EPG method (EPG = 0(N = 106) vs. EPG > 0 (N = 44)) a difference of nearly 800 l of milk per cow per lactation wasfound (P < 0.05). On the other hand, milk production between groups separated by Pepsinogen(mUtyr≤1000 vs. mUtyr > 1000) or by anti-Ostertagia (ODR≤0.5 vs. ODR > 0.5) resultsdid not differ. Interestingly, proportion of cows in each group differed between methods(P < 0.0001), and the anti-Ostertagia method yielded significantly more cows in the highindex group compared to results using the EPG or Pepsinogen method. No correlations werefound between parasite indexes determined by the different methods. High parasite burdenestimation found may be ascribed to the production system, fully grazing all year round, andto the sampling time, at the beginning of lactation with cows in negative energy balanceand depressed immunity. The fact that the cows were born and reared outside, on pasturewith continuous nematode larvae exposure, may also account for the results obtained.In conclusion, EPG counting during the first postpartum month may be a useful tool forthe diagnosis of production impairment induced by high nematode burden in adult grazingdairy cows. The anthelmintic treatment of only the EPG-positive recently calved cowswould improve milk production, while reducing selective pressure on nematode populationfor the development of resistance.