Variability in the infection of F1 Katahdin x Pelibuey crossbred lambs to gastrointestinal parasitic nematodes in a warm humid climate
González Garduño, RobertoGives, Pedro Mendoza deTorres Hernández, Glafiro
Background: In sheep production systems based on grazing, gastrointestinal nematodes (GIN) are one of the main problemsfaced by farmers. The occurrence of anthelmintic resistance in GIN has endangered the productive activity of sheep, sothat one alternative has been through the selection of sheep. The selection programs are based on evaluation of parasitismby measuring the fecal egg counts (FEC) of GIN due to the high correlation between the FEC and worm burdens. Theidentification of resistant and susceptible lambs requires knowing the FEC after the infection. The aim of this research wasto determine the intra-breed variability on FEC of GIN in Katahdin x Pelibuey grazing sheep.Materials, Methods & Results: The experiment was conducted in Tabasco, Mexico in a warm humid climate. The studywas carried out in three stages: in stage I, the FEC was recorded in newly weaned lambs experimental infected with 1600infective larvae (L3) of Haemonchus contortus and Cooperia curticei (85% and 15% respectively). Twenty lambs weredrenched with albendazole and 20 more lambs were considered as control without any anthelmintic treatment. In stage IIacquired resistance was determined in the same animal group after a break period following the same treatments. In stageIII new lambs were introduced to paddocks and the FEC was recorded in their first infection. Every 15 days fecal sample,live weight and blood samples were taken to determine FEC, daily gain weight and packed cell volume. Data were analyzed with a model of repeated measures over time. In order to establish the level of anti-parasitic resistance in the lambs,a categorization of the lambs according to their FEC was performed based on the EPG mean and standard deviation. Subsequently another statistical analysis was performed by category to determine the EPG, PCV and DWG values per group.In primary infection, both lambs treated with albendazole and control group reached a maximum elimination at 32 days...(AU)
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