1998 Volume 44 Issue 3 Pages 266-271
The present study was examined to utilize the aquatic fern Azolla species as a feed resource effectively in southern Kyushu. The influence of culture solution pH, growing season, introduction of ducks on multiplication of Azolla, chemical composition and palatability of Azolla for ducks, and the effect of Azolla feeding on meat production were investigated. The results obtained were as follow : An experiment using culture solution of pH2.8-9.2 indicated that the A. japonica had a similar pattern of growth rate in each level of pH 5.5-8.5. Five Azolla species i.e. ; A. pinnata 103, A. filiculoides 1006, A. caroliniana 3004, A. microphylla 4018, and A. japonica showed a slower growth during 1-2 weeks after inoculation in April (mean air temp. 14.6℃) than in May (mean air temp. 21.4℃) 1996. Though there was no significant difference of growth during 0-5 weeks after inoculation among the 5 species, A. filiculoides 1606 and A. japonica tended to grow rapidly to some extent. The biomass of Azolla mixture inoculated in the paddy field (with free-ranged ducks and without ducks) was not over 2000 kg/10 a during 0-40 days due to furrow shading in the paddy field after rice transplanting. However, pest injuries, reddening, over-luxuriant growth, and moulds were not found in plants in the paddy field with ducks. The Azolla mixture contained 25.1% crude protein on DMbasis. The palatability (FWbasis) of A. japonica for ducks was significantly higher than those of Artemisia vulgaris L., Trifolium repens L., Vicia angustifolia L., Rumex obtusifolias L., Lolium multiflorum Lam. and Brassica oleracea var. (p<0.01). Duckling fed with Azolla mixture along with formula feed, had significantly greater growth rates during 2-8 weeks of age than those fed with formula feed only. The feed conversion of the former was lower during 6-4 weeks of age than the latter, however, it tended to be higher afterwards. These findings suggested that Azolla had higher palatability (FWbasis) for the ducks, and also its supplementation to the animals resulted in better meat production as well as faster growth.
