Abstract

ESTEBAN-ANDRES, D et al. DEVELOPMENT OF RESISTANCE TO GASTROINTESTINAL NEMATODE IN HAIR SHEEP CHALLENGED WITH DIFFERENT LEVELS OF INFECTION. Rev. Med. Vet. Zoot. [online]. 2013, vol.60, n.3, pp.169-181. ISSN 0120-2952.

24 Katahdin x Pelibuey male lambs were used. The lambs were random in four groups with the following treatments: a) 25 infective larvae (L₃) of gastrointestinal nematodes (GIN) per kg of body weight (BW), b) 50 L₃ BW, c) 100 L₃ BW and the control group (0 L₃). The experiment was divided into three stages: 1) Experimental infection in stabling, 2) grazing infection and 3) housed lambs. At each stage were determined the number of nematode eggs per gram of feces (EPG), body weight and packed cell volume (PCV). The data analysis was performed using a repeated measures model in time. The lambs infected with 100 L₃ had higher EPG (1642 ± 1183) in comparison with the treatment of 50 L₃ (1140 ± 1313 EPG) and 25 L₃ (458 ± 371 EPG). With 50 L₃ the lambs had the lowest PCV (23.7 ± 4.8%). With the application of 100 L₃ also had lower PCV than control group and 25 L₃ (26.2 ± 3.9, 28.0 ± 4.1 and 27.3 ± 4.2%, respectively). It was observed a decrease in weight gain of all infected groups compared to the control group, by 22% in lambs with 25 larvae, 60% in the 50 larvae and 61% in animals of 100 larvae. During the second stage, the group infected with 100 larvae there was a reduction of EPG (2033 ± 2553 EPG), an increase in PCV (27.8%) and increased kg (3.7 kg) with respect to other infected for this reason was concluding that lambs receiving 100 L3 had lowest nematode faecal egg count, highest PCV and gain daily weight during the grazing reinfection.

Keywords : Cooperia curticei; Haemonchus contortus; live weight; packed cell volume.

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