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 summer

O 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 m² 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 fezes foram recolhidas manualmente dos canteiros. O número de larvas infectantes recuperado foi muito pequeno em comparação com a quantidade de larvas produzidas nas culturas controle, mantidas no laboratório (máximo de 6,7 por cento no capim Aruana com 30 cm de altura). Arecuperação de L3 das amostras fecais foi maior quando as fezes foram depositadas em meio ao capim alto (com 30 cm - P<0,05). Porém, a recuperação de L3 das forragens foi similar em ambos os cortes. Em relação à concentração de L3 (número de L3/kg de matéria seca), não houve diferença entre o corte baixo e alto (P>0,05) em nenhuma das semanas experimentais. Dentre as espécies forrageiras, o capim aruana foi o que, no geral, apresentou maiores concentrações de L3 de T. colubriformis.

The purpose of the experiment was to evaluate infective Trichostrongylus colubriformis larvae (L3) survival in three forage species. Experimental plots, planted with Brachiaria decumbens cv. Australian, Cynodon dactilon cv. Coast-cross, and Panicum maximum cv. Aruana, were used in the study, totaling two plots for each species. Each plot (32.4 m²) 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 compa6rison with the amount of larvae produced in cultures maintained in laboratory (maximum 6.7 percent 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.

[Recovery of Trichostrongylus colubriformis infective larvae from three grass species contaminated in summer]. / Recuperação de larvas infectantes de Trichostrongylus colubriformis em três espécies de gramíneas contaminadas no verão.

The purpose of the experiment was to evaluate infective Trichostrongylus colubriformis larvae (L3) survival in three forage species. Experimental plots, planted with Brachiaria decumbens cv. Australian, Cynodon dactilon cv. Coast-cross, and Panicum maximum cv. Aruana, were used in the study, totaling two plots for each species. Each plot (32.4 m(2)) 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.

[Trichostrongylus colubriformis larvae recovery from different Brachiaria decumbens and Panicum maximum strata]. / Recuperação de larvas de Trichostrongylus colubriformis EM diferentes estratos de Brachiaria decumbens E Panicum maximum.

The purpose of the experiment was to evaluate infective Trichostrongylus colubriformis larvae vertical migration in two forage grass species. Experimental modules formed by eight plots, established with Brachiaria decumbens cv. Australian and Panicum maximum cv. Aruana, were used in the study, totaling four plots for each grass species. Each plot was divided into six 30 x 30 cm subplots. Larval migration was evaluated in the four seasons of the year, in different plant strata (0-7, 7-14, 14-21, 21-28 and above 28 cm). Four feces deposits were made, one in each season of the year, in the middle of 30-cm tall forage. The feces were collected from the forage ten days after each feces deposit in the experimental subplots. Grass height was measured in each of the strata immediately before the collections. The forage of the different strata was cut from an area measuring 10-cm in radius. The feces were collected manually from the subplots. There was a grass species and grass stratum interaction in the deposit made in autumn (P<0.05). During that season, most of the larvae were recovered from the Brachiaria grass base; meanwhile, at the forage apex, the biggest average was registered in the aruana grass. Infective larvae (L3) recovery was similar among the different strata during spring. In springtime, the biggest L3 recovery occurred at the 21-28 cm stratum from both forage species. No L3 was recovered from any of the No L3 was recovered from any of the grass strata during winter and summer. Study results show that migration of T. colubriformis larvae was more influenced by weather conditions than by forage species.

Relationship of intestinal histology with the resistance to Trichostrongylus colubriformis infection in three breeds of sheep

The study was carried out to evaluate the relationship of inflammatory intestinal cells with the resistance to Trichostrongylus colubriformis infections in three breeds of sheep (Santa Ines, Suffolk and Ile de France), naturally infected. Mast cells, eosinophils, and globule leucocytes were enumerated in intestinal mucosa. Histamine concentration was estimated in intestinal tissue samples and the length of male and female specimens were determined. The three breeds of sheep showed similar cellular response in the small intestine mucosa (P>0.05). There was extensive variation among sheep in the parasitological and inflammatory cell variables, even in lambs of the same breed. In general, animals presenting less inflammatory cells had a larger worm burden, higher fecal egg counts, and larger T. colubriformis worms. The inflammatory cells possibly impaired the parasite's establishment, development, and survival.

Avaliaram-se a associação entre o número de células inflamatórias no intestino delgado e a resistência à infecção por Trichostrongylus colubriformis em ovinos de três raças (Santa Inês, Suffolk e Ile de France), naturalmente infectados. Mastócitos, eosinófilos e leucócitos globulares foram quantificados na mucosa intestinal. A concentração de histamina foi estimada em amostras teciduais do intestino, bem como foi determinado o comprimento de machos e fêmeas de T. colubriformis. A resposta celular foi similar na mucosa intestinal das três raças ovinas (P>0,05). Houve grande variação entre os ovinos em relação aos resultados parasitológicos e celulares, mesmo nos animais de mesma raça. Em geral, os animais que apresentaram número menor de células inflamatórias tiveram cargas parasitárias maiores, contagens de ovos por grama de fezes mais altas e exemplares de T. colubriformis maiores. Os resultados indicaram que mastócitos, eosinófilos e leucócitos globulares prejudicaram o estabelecimento, o desenvolvimento e a sobrevivência dos parasitas.

Resistance of Santa Inês and Ile de France suckling lambs to gastrointestinal nematode infections.

A trial was carried out to determine the resistance to natural infection by gastrointestinal nematodes in 12 Santa Inês and nine Ile de France lambs before weaning. Faecal samples were obtained for faecal nematode egg counts (FEC). Blood samples were collected to determine packed cell volume (PCV), total plasma protein levels and peripheral eosinophil counts. Most Ile de France lambs (77.8%) were treated with an anthelmintic at 43 days of age, while 50% off Santa Inês lambs were treated at weaning, 57 days of age. The mean PCV values were normal in Santa Inês lambs, while in Ile de France lambs showed lower values reaching 22.3% at 43 days of age. The lowest mean plasma protein values were observed in Ile de France lambs (4.13 g/dl) at 43 days of age and in Santa Inês lambs (5.0 g/dl) at 57 days of age. Before weaning, Santa Inês lambs were susceptible to natural infections by gastrointestinal nematodes but with a greater capacity to stand the adverse effects of parasitism compared to Ile de France lambs.