Resistance of sheep from different genetic groups to gastrointestinal nematodes in the state of São Paulo, Brazil

Abstract

Infections by gastrointestinal nematodes cause large losses to sheep breeders. In the study reported here, the resistance to gastrointestinal nematodes was analyzed in sheep of adapted and non-adapted breeds, maintained in naturally infected pastures. A total of 134 females from seven genetic groups were monitored during 20 months: Santa Inês (OSI), Dorper (ODO), Texel (OTX), Ile de France (OIF), and animals from crosses of Santa Inês ewes with Dorper (ODS), Texel (OTS) and Ile de France (OIS) rams. Blood samples were collected monthly to determine the packed cell volume (PCV), and feces were collected at the same time to count the eggs per gram (fecal egg counts = FEC) and identify the genera of the prevalent parasites. The statistical analyses of the data showed significant differences (p < 0.05) regarding the genetic group, collection month and interaction of month with the genetic group on the FEC. The correlation estimates between FEC and PCV were negative and significant (p < 0.01).The OTS genetic group presented the lowest mean of FEC value. Concerning the nematode genera, the greatest prevalence was observed for Haemonchus spp. (85.6%), followed by Trichostrongylus spp. (10.8%), Oesophagostomum spp. (2.9%) and Cooperia spp. (0.7%). The results obtained in this study show that the crossing of the Texel and Santa Inês breeds can be considered an alternative for sheep production in the Southeast region of Brazil due to the lower egg output by gastrointestinal nematodes.

Morada Nova sheep breed: Resistant or resilient to Haemonchus contortus infection?

“…In the present study, natural infection with a predominance of H. contortus was detected, corresponding to almost all of the L 3 recovered from the lamb and ewe fecal cultures, similar to previous reports for other sheep flocks raised at CPPSE/Embrapa ( Chagas et al, 2008 , Chagas et al, 2015 , Gonçalves et al, 2018 ), as well as in other regions of São Paulo state ( Amarante et al, 2004 , Louvandini et al, 2006 ).…”

Novel Strategies for the Control of Gastrointestinal Nematodes in Sheep

“…Thus, it was shown earlier that the selection of animals with the lowest number of eggs in feces could be a selection criterion, considering that the FEC was reduced by 69% after the testing (Eady et al, 2003). Also, the degree of nematode burden can vary depending on the breed, as shown by the results of the study done by Goncalves et al (2018), where Texel and Santa Inés had lower FEC compared to Ile de France and Dorper breeds. There is also an option to assess the genetic correlation between features that indicate body development (e.g.…”

Fighting the Deadly Helminthiasis without Drug Resistance

“…Gastrointestinal nematode infections have led to severe economic stresses in goat and sheep production systems and caused the search for different means of control than the series of pharmaceutical drug treatments, which have already developed growing resistance to the chemicals in the treated helminths against goats and sheep. The genetic selection of resistant breeds of small ruminants is considered [31], especially since heritability values of up to 0.65 of different animal breeds against fecal egg counts have been reported in previous studies. The Santa Ines sheep are considered to be highly resistant to internal parasites.…”