Biological control is a strategy to decrease parasitic populations, and the action takes place through natural antagonists in the environment. We studied the predatory activity of the fungus Duddingtonia flagrans in infective larvae (L3) of gastrointestinal nematodes after gastrointestinal transit. Ten heifers were divided into two groups: treated (animals received pellets containing fungus) and control (animals received pellets without fungus). Twelve hours after administration, faeces samples were collected for in vitro efficacy tests. The animals then remained for 7 h in the experimental pasture area. At the end of this period, 20 faecal pads (ten treated and ten control) were selected at random. Pasture, faecal pad and soil collections occurred with an interval of 7 days, totalling four assessments. In vitro activity demonstrated that fungi effectively preyed on L3, achieving a reduction percentage of 88%. In the faecal pad of the pasture area, there was a difference (P < 0.05) between collections 3 and 4 for both groups; in the treated group a reduction of 65% was obtained, while in the control group there was an increase of 217% in the number of L3. The recovery of L3 in the soil and in the pasture was similar in both groups. There was no influence (P = 0.87) of the passage time on the fungus predatory activity. Duddingtonia flagrans demonstrated the ability to survive gastrointestinal transit in the animals, reducing the number of L3 in the faeces, indicating that this biological control has great potential in the control of worm infections.

The resistance of gastrointestinal nematodes (GIN) of sheep to anthelmintic treatment has motivated researchers to seek alternatives to reduce the use of these drugs in sheep farming and decontaminate pastureland based on knowledge about the survival dynamics of larvae. The aim of this work was to evaluate the migration of the infective larvae (L3) of Haemonchus contortus at different times of the day, strata, and sward heights, with and without shade after the deposition of contaminated sheep feces. The grass species used here was Cynodon dactylon cv. Tifton 85 in four treatments: low sward height shade; low sward height sunshine; high sward height shade; and high sward height sunshine. The number of L3 recovered from the pasture at different times of the day did not differ. The highest number of L3 recovered was in shade. The number of L3 at different times and strata occurred uniformly, confirming that L3 remain in the same place after migrating from dung at the hottest times of the day. Infective larvae of H. contortus were able to migrate across all the strata regardless of the time of day in the summer season in humid subtropical climate.

This study aimed to evaluate the resistance of Texel (Tx) and Ile de France (IF) sheep to gastrointestinal nematode infections in the periparturient period and after weaning, and the performance of their lambs. Fecal samples were collected from 19 IF and 17 Texel ewes to determine fecal egg counts (FEC) and larval cultures were prepared to determine the prevalence of nematodes. The ewes were weighed to determine body weight (BW) and blood samples were taken to determine the packed cell volume (PCV) and plasm protein values (PPV). The ewes were classified into two groups by FEC (heavy and moderate infection). The IF presented higher FECs than Tx 28 and 14 days before parturition; 14, 28, and 56 days after parturition; and 28 days after weaning (P<0.05). In the weaning and dry periods, the IF presented higher PCVs than Tx (P<0.05). The PPV did not differ between the groups (P>0.05). The IF presented a higher BW than Tx 14, 28, and 42 days after parturition, and in the weaning and dry periods (P<0.05). The ewes of both breeds classified as moderately infected had the highest BW at weaning (P<0.05). IF ewes with a moderate infection produced weaning lambs that were heavier than those of Tx with the same level of infection (P<0.05). Overall, Tx ewes presented a better ability to withstand infections during the periparturient period and after weaning. Although the IF ewes presented the highest FEC and more intense periparturient rise, they managed to maintain their level of production.

The objective of this study was to evaluate the predatory activity of the nematophagous fungus Duddingtonia flagrans on infective larvae of gastrointestinal nematodes from dairy heifers in different conditions (shaded and sunny) of a silvopastoral system (SPS) on an agroecological farm. Ten Jersey heifers were divided into two groups: treated (received pellets containing fungus); and control (received pellets without fungus). Twelve hours after fungus administration, faeces samples were collected for in vitro efficacy tests. The animals then remained for 8 h in the experimental pasture area. At the end of this period, 20 faecal pads (10 treated and 10 control) were selected. Pasture, faecal pad and soil collections occurred at intervals of seven days (d), totalling four assessments over 28 d. To evaluate the influence of the conditions shaded and sunny, we registered the condition of the location of each faecal pad per hour. After 12 h of gastrointestinal transit in dairy heifers, a reduction of 65% was obtained through the in vitro test. The treated group presented a lower number of infective larvae (L3) in the faecal pad and upper pasture. Differences in numbers of L3 were observed between the conditions (sunny and shaded) in the faecal pad of the control group; while in the treated group there were no differences between the conditions. The predatory activity of the fungus was efficient over time in the shaded and sunny conditions of an SPS, decreasing the parasite contamination during the pasture recovery time in a subtropical climate.

O controle biológico é por definição uma estratégia para diminuir as populações parasitárias em níveis aceitáveis, ou seja, que não se tornem prejudiciais ao hospedeiro. A ação se dá através de antagonistas naturais no ambiente como bactérias, artrópodes e fungos, os quais atuam controlando a propagação parasitária (CORREDOR, 2016). Dentre eles, os fungos nematófagos têm demonstrado maior potencial, sendo a espécie Duddingtonia flagrans considerada a mais promissora (WANG et al., 2015). Desta maneira, o objetivo do trabalho foi avaliar a atividade predatória do fungo D. flagrans sobre o desenvolvimento de larvas infectantes (L3) em distintos estratos da pastagem sob diferentes incidências solares. O experimento foi realizado no Centro Paranaense de Referência em Agroecologia (CPRA) em Pinhais-PR. Foram utilizadas vinte novilhas da raça Jersey divididas em dois grupos. No grupo tratado os animais receberam 150g de pellets em dose única contendo massa micelial (0.2g de micélio) do fungo misturado a 500g de concentrado. No grupo controle os animais receberam 150g de pellets sem o fungo e 500g de concentrado. Após 10 horas da administração do fungo os animais foram direcionados ao piquete experimental onde ficaram das 6:00h até 14:00h. Durante este período foram selecionados ao acaso 10 bolos fecais de animais tratados e 10 bolos fecais de animais controle. Cada bolo fecal foi delimitado e dividido em quatro subdivisões iguais por meio de ligações entre as extremidades. As coletas do pasto foram realizadas por meio das subdivisões, a cada sete dias, totalizando quatro avaliações. Foram coletadas amostras de pasto com distância de 10 cm do bolo fecal em dois estratos (A:50% da parte superior da pastagem e B:50% da parte inferior da pastagem). Para avaliar o efeito da incidência solar na atividade predatória foi medido a cada hora a posição da amostra em relação à incidência solar (permaneceu no sol mais de 50% do dia ou permaneceu na sombra mais de 50% do dia). O delineamento experimental utilizado foi em blocos inteiramente casualizados com 2 tratamentos e 20 repetições. Para as análises estatísticas os dados foram transformados em log (x+1) pelo teste Tukey a 5% de significância. Houve diferença (P<0,05) na recuperação de L3 entre os grupos tanto no estrato A (Controle: 714 L3/kg MS; Tratado: 57,3 L3/kg MS) quanto no estrato B (Controle: 732 L3/kg MS; Tratado 136,6 L3/kg MS) demonstrando a efetividade de predação e migração vertical do fungo. A incidência solar não interferiu (P>0,05) na recuperação de L3 tanto no grupo controle quanto no grupo tratado nos dois estratos avaliados. Contudo pode-se observar uma maior contagem de L3 nas amostras que permaneceram mais de 50% do dia no sol (Controle A:1063 L3/kg MS, B:986 L3/kg MS /Tratado A:81 L3/kg MS, B:150 L3/kg MS) do que nas amostras que permaneceram mais de 50% do dia na sombra (Controle A: 191 L3/kg MS, B: 350 L3/kg MS/ Tratado: A:0 L3/kg MS, B:104 L3/kg MS). O fungo D. flagrans demonstrou ser capaz de suportar o trânsito gastrintestinal e reduzir o número de L3 nos diferentes estratos da pastagem.