Integrating the control of helminths in dairy cattle: Deworming, rotational grazing and nutritional pellets with parasiticide fungi

Highlights

• Deworming only is insufficient to control helminths affecting grazing cattle.

• Control of helminths in grazing cows needs to integrate deworming plus prevention.

• Long pasture resting periods are needed to prevent helminth infection in grazing ruminants.

• Daily ingestion of fungal chlamydospores improves the usefulness of rotational grazing.

Abstract

Thirty-two Friesian cattle under a leaders/followers four-day rotation and passing eggs of trematodes and gastrointestinal nematodes (GIN) were studied in two trials for the integrated control of these helminths over two years. In the first trial, the effect of rotational pasturing was assessed on a group of leaders (milking cows, G-L1) and followers (dried-off cows and heifers, G-F1) supplemented daily with commercial nutritional pellets. In the second trial, leaders (G-L2) and followers (G-F2) were maintained under a rotational pasturing regime; the cows received daily commercial pelleted feed and heifers pellets manufactured with a blend of parasiticide fungi (3 × 10⁵ chlamydospores of both Mucor circinelloides and Duddingtonia flagrans/kg pellet). Deworming via closantel and albendazole was performed in cows in each trial at the beginning of their drying periods, and fourteen days later, the fecal egg-count reductions (FECR) of Calicophoron daubneyi and GIN were from 94 to 100% (average 98 %), while the percentages of reduction of cattle shedding eggs (CPCR) were from 50 to 100% (average 77 % and 82 %, respectively). The heifers were dewormed one time only, at the beginning of each trial, and the values of FECR and CPCR were 100 % against C. daubneyi and 96 % and 83 %, respectively, against GIN. Over a period of 24 months, significantly higher numbers of helminth egg-output were observed in G-L1, with the lowest numbers in G-F2. C. daubneyi egg output was reduced by 5 % (G-L1) and 42 % (G-F1) at the end of trial 1 and by 83 % (G-L2) and 100 % (G-F2) at the end of trial 2; the numbers of GIN egg-output decreased by 13 % (G-L1) and 18 % (G-F1) at the end of trial 1, and by 72 % (G-L2) and 85 % (G-F2) at the end of trial 2. No adverse effects were detected in cattle taking pellets enriched with fungal spores (G-F2). It is concluded that long-term ingestion of spores of M. circinelloides and D. flagrans provides a valuable tool to improve the effect of rotational grazing and to lessen the risk of infection by C. daubneyi and GIN in dairy cattle, and accordingly, the performance of integrated control programs.

Introduction

The numbers of grazing cattle have increased markedly, partly because this is a cost-effective regime, and partly because of the preoccupation on animal welfare in food production (Thornton, 2010). Trematodes belonging to Fasciolidae and Paramphistomidae and can frequently affect ruminants on humid habitats, where appropriate conditions are present for the development of the external phase in their life cycle (Szmidt-Adjidé et al., 2000). Gastrointestinal nematodes (GIN) are helminths that often infect grazing ruminants through the ingestion of third larvae (the infective stages) (Smith and Sherman, 2009; Craig, 2009).

Control of helminths in dairy cattle becomes especially difficult because deworming is only allowed during the dry period, which occurs consecutively on farms throughout the year. Therefore, treated and untreated cows can share the same pastures, and untreated ruminants continue to shed eggs in the feces, increasing the risk of all cows ingesting infective stages of helminths (e.g., eggs, larvae) while feeding on grass.

With the aim to diminish the presence of infective stages in the soil, rotational grazing regimes characterized by ruminants feeding on grass for a time interval (grazing period), followed by other rest periods, are advised (Undersander et al., 2002). In the last years, biological strategies for the control of helminths based on the use of certain soil saprophytic fungi have been reported. Some species (Duddingtonia flagrans, Monacrosporium thaumassium) are able to trap the infective stages of GIN (Araújo et al., 2004), and others can produce antagonistic effects on helminth eggs as trematodes, cestodes and nematodes (Pochonia chlamydosporia, Mucor circinelloides, Purpureocillium lilacinum) (Cazapal-Monteiro et al., 2015; Cortiñas et al., 2015); they can also act against the miracidia of C. daubneyi (Arroyo et al., 2017). Former studies have stated the usefulness of providing cattle chlamydospores in water solutions (Assis et al., 2013; Silva et al., 2014; Saumell et al., 2015), mass mycelia of D. flagrans or M. thaumassium in alginate pellets (Dias Luns et al., 2018), or as a blend of spores of D. flagrans and M. circinelloides in industrially manufactured pellets (Hernández et al., 2016). Recently, a commercial formulation containing chlamydospores of D. flagrans was registered (Healey et al., 2018). The efficacy and safety of combining rotation of grasslands with providing pellets enriched with chlamydospores of M. circinelloides and D. flagrans were successfully tested on horses (Hernández et al., 2018a).

In the current investigation, the helpfulness of the integrated control of helminths among dairy cattle based on anthelmintic treatment, pasture rotation and feeding on pellets manufactured with chlamydospores of M. circinelloides and D. flagrans was analyzed.