Low viability and germinability of commercial pasture seeds ingested by goats

Endozoochory by domestic ruminants has been proposed as a method to disseminate pasture seeds for rangeland rehabilitation in Mediterranean regions. The objective of this study was to investigate whether seeds of two common Mediterranean forage species: Trifolium subterraneum (legume) and Lolium rigidum (grass) were able to pass undestroyed through the gut of the goats and germinate afterwards and thus if the goats can disseminate these two forage pastures. The seeds were fed on a single dose to six individually housed goats, mixed with different meals in order to see if the passage of the seeds through the goat's gut had any effect. Faeces were collected every 24 h after seed ingestion for five days. Seeds not eaten by the goats along with seeds retrieved from faeces were tested for viability and germinability. The effect of being embedded in faeces on germination and seedling growth was also tested. Very few seeds of both species were retrieved from faeces (1.5% in T. subterraneum and 2% in L. rigidum). They were less viable, between 40% in T. subterraneum and 70% in L. rigidum, and germinated less, around 30% in T. subterraneum and 60% in L. rigudum, than the seeds not eaten by the goats. The latter ones showed percentages of viability and germination over 90%. These results support those obtained by other researchers that currently available commercial seeds are not suitable for endozoochorus seed dispersal. Seedling emergence was significantly lower in intact dung pellets than in broken-down dung ones in both species, specially in L. rigidum. The dung inhibited seed germination in L. rigidum, where seedling emergence was lower than seed germination. Seedlings grown in dung were significantly larger than those grown in vermiculite, showing the fertilizing effect of dung. Trampling of grazing animals, rainfall and coprophagous insects that break up the dung are needed for seedling establishment, specially for species that cannot emerge from intact dung. Dung is a fertilizer but also can inhibit germination of some species, as L. rigidum.