In vitro effect of seven seaweed extracts on gastrointestinal nematodes

The exploitation of seaweed for animal feed (i.e. protein) and health promoting purposes is becoming more and more important – especially in countries where large amounts of biomass can be produced (e.g. northern countries such as Norway). Many seaweed species contain plant secondary compounds (PSMs) with broad bioactivity and potential animal health and welfare impacts. We report preliminary data on the effect of 7 seaweed extracts on the gastrointestinal nematode species Trichostrongylus colubriformis and Teladorsagia circumcincta which are responsible for considerable morbidity in sheep. For each seaweed species, 50 g of dried and grinded (1 mm) seaweed was extracted with 500 mL of EtOH/H₂0 (50:50 v/v) for 2h. After elimination of all particulate matter, EtOH was evaporated and the EtOH free extract was mixed with 50 g Amberlite XAD-2 in order to absorb PSMs. After that, the extract was washed again to eliminate NaCl and iodine (present because of marine origin) which both interfere with larval stages (L3) used for in vitro tests. After eluting with 100% EtOH, water was added and the EtOH/H₂O extract was subjected to evaporation and lyophilisation. A larval exsheathment test as described by Brunet et. al. (2007) [1] was used for in vitro evaluation of the respective extract efficacies. The test dose (table 1) was calculated considering both the respective extract yield and an estimate of extract concentration available within the rumen of sheep having consumed 25% of dry seaweed within a daily ration. None of the extracts reduced the exsheathment of either T. colubriformis or T. circumcincta (Table 1) significantly.

Tab. 1: Seaweed species and extract concentrations testet for larval exsheathment of Trichostrongylus colubriformis and Teladorsogia circumcincta. Larval exsheathment results are given as percent reduction compared to the respective controls (controls not shown). Six replicates were run per tested seaweed and parasite species as well as for respective controls.

Seaweed species	Extract (mg/mL)	GIN species	larval exsheathment reduction (%)
Acrosiphonia sp.	0.282	T. circumcincta	0,0
Acrosiphonia sp.	0.282	T. colubriformis	5,5
Alaria esculenta	0.293	T. circumcincta	0,0
Alaria esculenta	0.293	T. colubriformis	0,6
Laminaria sp.	0.564	T. circumcincta	0,5
Laminaria sp.	0.564	T. colubriformis	0,0
Mastrocarpus stellatus	0.487	T. circumcincta	8,2
Mastrocarpus stellatus	0.487	T. colubriformis	0,0
Palmaria palmata	0.762	T. circumcincta	0,0
Palmaria palmata	0.762	T. colubriformis	0,0
Pelvetia canaliculata	0.339	T. circumcincta	1,4
Pelvetia canaliculata	0.339	T. colubriformis	1,6
Porphyra sp.	0.285	T. circumcincta	3,3
Porphyra sp.	0.285	T. colubriformis	0,0

References:

[1] Brunet S, Aufrere J, El Babili F, Fouraste I, Hoste H. The kinetics of exsheathment of infective nematode larvae is disturbed in the presence of a tannin-rich plant extract (sainfoin) both in vitro and in vivo. Parasitol 2007; 134: 1253 – 1262