Special edition: organic feed

Fungal supplement may reduce parasite load in organic dairy calf systems

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Dietary treatments of fungal spores may help manage gut parasites in calves reared organically, say researchers.

A team of researchers in Mexico examined the use of chlamydospores of a fungal strain in dairy calves raised in an organic production system as a way to manage intestinal parasites, like the gastrointestinal nematode (GIN).

The group published their work in the journal of Experimental Parasitology.

Study summary 

  • A method of bio-control of cattle nematodes in an organic milk farm was assessed.
  • Duddingtonia flagrans chlamydospores were orally administered in grazing calves.
  • Fungi reduced 53.8% (average) and 75.3% (highest) the GIN faecal larvae population.

“This research was aimed [at] assess[ing] the effect of using D. flagrans chlamydospore in reducing the GIN larval population in feces of calves maintained under an organic milk production system in Chiapas, Mexico,” they said.

The team found that the D. flagrans chlamydospore could be used to reduce the generation of nematode larvae.

“From the present study, it can be concluded that the progressive treatment of American brown Swiss zebu calves with D. flagrans chlamydospores reduces the means of gastrointestinal nematode larvae in fecal cultures and in grazing areas,” they said. 

“This method can be considered in future programs of integrated control as a possible tool of control of gastrointestinal parasitic nematodiasis in organic milk production systems," concluded the researchers.

Disease management in organic production?

Disease management in an organic production system requires attention as the use of chemical anthelmintic drugs is restricted, only limited de-worming treatments are permitted, and deworming animals for slaughter has been banned, said the researchers.

The focus on disease prevention is important for infective diseases and gastrointestinal parasitic nematodiasis (GIN), he said.

Using nematophagous fungi as a biological control agent has been suggested as an acceptable alternative to manage nematode parasitic infections, they said. “The use of nematophagous fungi is based on the fact that these organisms are able to form trapping devices especially designed to trap nematodes and destroy them and eventually feed on the nematodes inner tissues,” they added.

“Using natural nematode enemies such as nematophagous fungi for controlling nematodiasis of cattle offers a number of advantages over the use of chemical anthelmintic drugs ;ie., does not cause resistance in the parasites, it does not contaminate soil and does not remain as toxic residues in milk, meat or animal sub-products for human consumption, and they are considered as harmless to animals and human beings,” they said.

The species Duddingtonia flagrans is thought to be the most promising strain of nematophagous fungus in both calves and small ruminants, said the researchers. Feeding chlamydospores of the species has been effective in the control of parasites for other ruminant species.

Methods

In the study, 50 male and female calves were tested for infection with GIN and 17 were selected, said the researchers.

Selected, infected calves were then fed an oral supplement containing the chlamydospore or kept as the negative control, they said. The supplement was given every two days for 30 days.

Animals in the trial were kept in the same grazing system from before the start of the trial, but grazed in separate areas, they said. No concentrate was included in the diet.

Fecal matter was collected from every animal every two days after the start of the study, said the researchers. Fecal cultures were done to note GIN infective larvae and grass samples were taken near fecal matter deposits so GIN larvae could be identified and counted every three days.

“Viability of fungal chlamydospores after passing the gastrointestinal tract of calves was visualized under the microscope after depositing one fecal pellet of the experimental animals on the surface of water agar plates and adding free-living nematodes as bait,” they said. “Germinating spores, trapping devices, trapped nematodes and retention of their fungal predatory activity was considered as the indicators of viability.”

The efficacy of the fungal predatory behavior also was calculated.

Results

It took several days for live chlamydospores to be found in the fecal matter of the supplemented calves, said the researchers. And none were found in the control group calves.

“From 12th day of treatments and until the end of the experiment (day 30th), most samples were positive to the presence of D. flagrans,” they said. “The samples corresponding to the 18th, 20th, 24th and 30th days after starting treatments were the days with more positive plates to the presence of D. flagrans.”

A reduction in amount of GIN infective larvae found was recorded starting on day 14 of the trial, they said. “During this period 53.8% of GIN larvae population was reduced by action attributed to the fungal administration,” they added.

“Statistical differences were found only at the 14th, 18th, 28th and 30th days after starting the treatments,” said the researchers. “The highest values in the reduction of the GIN larval population were found at the end of the experiment (day 28th) with values higher than 75% compared with the control group records.”

Reduction in the amount of GIN larvae found in the grass was also seen, they said. At the end of the study, larvae was reduced by about 42.5% for the group getting the fungal supplement.

Source: Experimental Parasitology

Title: Using Duddingtonia flagrans in calves under an organic milk farm production system in the Mexican tropics

DOI: 10.1016/j.exppara.2017.02.009

Authors: D Perez, B Munoz, J Tora, M Zebadúa, J Lopez, M García, P de Gives

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