Dinâmica da parasitose gastrintestinal em ovinos naturalmente infectados e a influência de efeitos climáticos sobre a recuperação de larvas infectantes (L3) em campo nativo

Abstract

The objective of the present study was to observe the effects of climate on the infective larvae infestation on native pastures in spring and summer and the correlation with the dynamics of intestinal parasitism in naturally infected ewe lambs. The experiment was carried out between October 2013 March 2014 on private property within the municipality of Dom Pedrito-RS with 50 sheep of Corriedale breed and initial average weight 28 kg in a paddock of nine hectares of native field without divisions. At intervals of 21 days were evaluated in the animals body condition score (ECC), count of eggs per gram of feces (EPG), stool test and FAMACHA ®. Measurements were performed to verify the pasture height (cm), collects the same for recovery of infectious larvae (L3) and availability of pasture (kg/MS/ha), besides being observed precipitation (mm), temperature (°C), direct sunlight (KJ/m²) and relative humidity (%). The animals were dewormed as needed according to the degree of parasitic infection. It was observed at the end of the trial period that OPG greater than 500 demonstrated less weight gain (2.03kg) (p=0.000), FAMACHA > 3 (p=0.005) and ECC < 3 (p=0.027) in summer with significant difference compared to the spring. In relation to larval culture one can observe higher prevalence of the genus Haemonchus spp. (72.79%) during the entire experimental period. It was possible to verify the relationship between OPG and infective larvae recovery of grazing with the climate data, noting significant difference to OPG (> 500) and greatest amount of L3 retrieved (> 19.17 L3/kg/MS) in temperature up to 22.5° C (p=0.000), summer (p = 0.000), precipitation > 120 mm (p=0.003), relative humidity > 73% (p=0.005) and solar radiation < 890 KJ\/m² (p=0.000). It was observed significant difference between OPG and availability of pasture > 2.600 kg/MS/ha and pasture height > 14.5 cm (p=0.000). Significant difference was observed compared to 500 > OPG amount of larvae on pasture (> 19.17 L3/kg/MS) (p=0.000). The climatic factors may influence the development of infective larvae on pasture, favoring greater ingestion and consequently greater parasite burden in animals. The ewe lambs failed to achieve minimum weight and body condition score for the reproductive period probably influenced by gastrointestinal parasitism during the summer. Further studies are needed to provide continuity in this area to better understand the dynamics of infective larvae in natural pastures.