Recovery and germination rates of seeds of Mediterranean medics and clovers offered to sheep at a single meal or continuously

Abstract

SUMMARY Measurements were made of the recovery and germination rates of seed of eight species of annual medic ( Medicago spp.) and three of clover ( Trifolium spp.) after ingestion by sheep. Recovery of medic seed was measured as the number of seeds collected from faeces after feeding, in addition to a basal diet, either (i) 200 g of pods at a single meal, or (ii) a quantity of pods estimated to contain 30000 seeds at a single meal or (iii) 200 g of pods daily for 21 days. Only the first method was applied to the clovers. There were large differences ( P < 0·001) in seed recovery between species, from < 2% to nearly 20% in medics, and up to 59% in T. campestre , which has low single-seed mass. Although there was a curvilinear decrease in seed recovery as single-seed mass increased ( r 2 = 0·80), the high recovery of M. rotata , a fairly large-seeded species, suggests that there are important differences between species, irrespective of seed size. When 200 g of medic pods was offered to sheep at a single meal, mean seed recovery was slightly lower than when 200 g of medic pods was offered daily for 21 days. Seed recovery of medics was much higher ( P < 0·001) when 30000 seeds were offered at one meal. Germination rate before ingestion was 1·9–6·5% ( P < 0·001) for hard-seeded medics and 2·7–9·7% ( P < 0·001) for clovers with low single-seed mass; passage through the digestive tract increased ( P < 0·001) germination rate in both medics and clovers.