Variation in phenotypic resistance to gastrointestinal nematodes in hair sheep in the humid tropics of Mexico
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The objective of the study was to evaluate phenotypic resistance against gastrointestinal nematodes in Blackbelly, Pelibuey and Katahdin ewes before pregnancy in the humid tropics of Mexico. Individual faecal and blood samples were taken in 59 Pelibuey, 69 Blackbelly and 73 Katahdin ewes. The egg count per gram of faeces (EPG) of gastrointestinal nematodes (GINs) was determined. The percentage of packed cell volume (PCV) and body condition score (BCS) of each animal were also recorded. The ewes were segregated as susceptible, intermediate or resistant based on the EPG using the quartile method. The data were analysed using the general linear method, and the means between breeds were compared by Tukey’s test. The relationships between the EPG, PCV and BCS were evaluated by Spearman correlation. The Katahdin ewes showed the highest EPG counts (3613.6 ± 5649) compared to the Blackbelly and Pelibuey ewes (576.1 ± 1009 and 56.8 ± 187, respectively, P < 0.01). The PCV values between breeds were similar (P > 0.05). The susceptible ewes had the highest EPG counts and the lowest PCV percentage (5069 ± 6404 and 22.8% ± 8.1% respectively) compared to the resistant ewes (P < 0.01). A higher percentage of Katahdin ewes were susceptible compared to the other breeds (P < 0.05). The main GIN species were Haemonchus contortus, Trichostrongylus colubriformis and Cooperia curticei. In conclusion, Katahdin ewes showed susceptibility to GIN compared to Blackbelly and Pelibuey ewes before the pregnancy period in the humid tropics of Mexico.
KeywordsResistance Susceptibility EPG Pelibuey Blackbelly Katahdin
The authors thank the Centre for Training and Reproduction of Minor Species (CECAREM) of Tabasco, Government, the Santa Martha and San Francisco farms for the facilities and animals granted. Claudia Virginia Zaragoza Vera received a scholarship from SEP-MEXICO (DSA/103.5/16/5835) to carry out her PhD studies at the Autonomous University of Yucatan, Mexico.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
Statement on the welfare of animals
The Bioethics Committee of the Campus of Biological and Agricultural Sciences of the Autonomous University of Yucatan, Mexico, approved the development of the present study under authorisation number CB-CCBA-D-2017-001.
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