Recuperação de larvas infectantes de Trichostrongylus colubriformis em três espécies de gramíneas contaminadas no verão

Abstract

RESUMOO experimento teve como objetivo avaliar a recuperação de larvas infectantes (L3) de Trichostrongylus colubriformis em Brachiaria decumbens cv. Australiana, Cynodon dactilon cv. Coast-cross e Panicum maximum cv. Aruana. Foram utilizados módulos experimentais constituídos por seis canteiros de 32,4 m 2 cada, perfazendo dois canteiros por espécie forrageira.Cada canteiro foi dividido em 36 parcelas, de 30 x 30 cm, de forma a permitir seis repetições por espécie e por altura da forragem em cada semana de colheita de material. A sobrevivência larval foi avaliada do meio do verão e até meados do outono, sob o efeito de duas alturas de poda das forragens: baixa, 5 cm e alta, 30 cm. A poda foi realizada imediatamente antes da deposição das fezes contaminadas com ovos de T. colubriformis, obtidos de ovinos, que ocorreu no dia 05/02/ 2004. A colheita das fezes e da forragem foi realizada uma, duas, quatro, oito, 12 e 16 semanas após a deposição das fezes nos canteiros experimentais. A altura da forragem foi medida em cada uma das subdivisões imediatamente antes da colheita. A forragem foi cortada rente ao solo, de uma área delimitada com o auxílio de um círculo de 10 cm de raio. As ) was divided into 36 subplots (30 x 30 cm) in order to allow six replicates per forage species and per herbage height in each week of material collection. Larval recovery was evaluated from middle summer to middle autumn under the effect of two forage paring heights: low, 5 cm, and high, 30 cm. The paring was carried out immediately before the fecal samples with T. colubriformis eggs, taken from sheep, were deposited on pasture in 05/Feb/2004. Feces and forage collection was performed one, two, four, eight, 12 and 16 weeks after feces deposition in the experimental plots. Forage grass height was measured in each subdivision immediately before the collections. The forage sample was cut, close to the soil, from an area delimited with a circle with a 10-cm radius. The feces were collected from the subplots. The number of infective larvae recovered from pasture was very small in comparison with the amount of larvae produced in cultures maintained in laboratory (maximum 6.7% on Aruana grass with 30 cm). L3 recovery rates from fecal samples were bigger when the feces were deposited on high grass (measuring 30 cm -P<0.05). L3 recovery from pasture and L3 concentration on herbage (L3/Kg dry matter) were similar for both cuts (P> 0.05). Among the forage species, the Aruana grass was the one that, in general, harbored the biggest concentrations of infective T. colubriformis larvae. RECUPERAÇÃO DE LARVAS INFECTANTES DE Trichostrongylus colubriformis EM TRÊS ESPÉCIES DE GRAMÍNEAS CONTAMINADAS NO VERÃO

Recovery of Trichostrongylus colubriformis infective larvae from three grass species contaminated in the autumn

“…Carneiro and Amarante (2008), in a study carried out in the same site of the present experiment, also observed higher recovery of H. contortus L3 from 30 cm high Aruana herbage at the moment of contamination. Rocha et al (2008), however, did not find influence of the herbage height on the recovery of T. colubriformis L3 in the summer. Such results indicate that the variation in the climate conditions may change the migration of gastrointestinal nematodes.…”

“…Fecal pellets act as reservoirs of infective larvae, especially during dry periods (CARRATORE, 2004;ROCHA, 2006). However, in rainy periods, the degradation of feces is higher (ROCHA et al, 2008). Rocha et al (2008) recovered, on average, only 20%, 31.5% and 36.6% from the feces deposited among Brachiaria, Aruana and Coast-cross herbage, respectively, in the last sampling (16 weeks after deposition of feces in the summer).…”

“…Details about the experimental module were described by Rocha et al (2008). The experimental module comprised six plots of 32.4 m 2 each, established with B. decumbens cv.…”

“…A total of 221 samples were prepared and each one contained 15 grams of feces. Details about coproculture and fecal deposition were described by Rocha et al (2008). Of the 221 samples, 216 were deposited on the plots and the remaining five were destined to coproculture in Petri dishes (control group).…”

“…All collections were performed between 6:30 AM and 7:30 AM. Details about L3 recovery from herbage and fecal samples were described by Rocha et al (2008).…”