Livestock waste management and policy through the utilization of aquatic feedstuffs

Production agriculture is faced with the prospect of having to produce enough food to keep pace with the needs of the world's population, while meeting waste treatment and disposal standards for public health and aesthetic quality (Goldman and Ryther, 1976). With increased levels of scrutiny on production practices, animal agriculture began paying attention to its by-products of production, particularly from its waste products.

Aquatic plants have been recognized as having potential for animal feed and other uses. Aquatic plants have the ability to utilize the effluent generated by municipalities and the often nutrient-rich wastes from agricultural operations. Aquatic plants that have been utilized in research include water hyacinths (Eichhornia crassipes), cattail (Typha latifolia), algae, seaweed, and duckweed (Lemnacaea). Duckweed is a tiny, free-floating, vascular aquatic plant. It is among the smallest and simplest of flowering plants, a worldwide family(Lemnaceae) of floating monocotyledons. Duckweed has the ability to utilize ammonia, nitrates and minerals from natural and wastewater and convert them to feedstuffs with usable proteins and minerals. Duckweed has a crude protein potential as high as 40 percent depending upon the type of media in which it is grown.

Cattle and sheep were fed duckweed as a portion of the crude protein supplement. In sheep, dry matter digestibilities ranged from 67-71 % and crude protein digestibility was similar to soybean meal (77.5 vs. 69.3%). Acceptance as a feed source was excellent in both sheep and cattle. Average daily gain and gain efficiency was similar in cattle fed duckweed to gain and gain efficiency in cattle fed soybean meal. Plasma urea-nitrogen concentrations were lower (P < 0.03) for cattle on a diet containing duckweed as the crude protein supplement than concentrations than cattle on diets including soybean meal as the crude protein supplement (4.66 vs. 7.15 mg/dl, respectively). No differences were noted for yield grade, hot carcass weight, rib eye area and liver abscesses in cattle on duckweed treatments and those on soybean meal treatments. Duckweed has the potential to be utilized as a crude protein source in the diets of ruminant animals.