Evaluation of Duckweed as a Protein Supplement for Ruminants

Abstract

The general purpose of the experiments reported in this thesis was to investigate whether duckweed, a protein-rich aquatic plant of the family 'Lemnaceae', is a potentially valuable dietary amino acid source for ruminants, especially in tropical and sub-tropical regions. As all dietary proteins ingested by ruminants are subjected to major modification in the rumen, the general features of degradation and synthesis of protein in the rumen are presented and discussed in Chapter 2. Background information on duckweed is also reviewed and included in this chapter. Determination of rumen degradability of a potential protein supplement is generally the initial approach taken in assessing its value for ruminants. This view was adopted in this thesis, and the rumen degradability of fresh and oven-dried duckweed, in comparison with that of cottonseed meal (chosen to represent an 'escape' protein supplement of about 60 % degradability) was evaluated using various techniques (Chapter 4). Results obtained in sacco showed that the effective N degradability at a rumen outflow rate of 5 %/h was 36 and 40 % for fresh and dried duckweed, respectively. The corresponding estimate for cottonseed meal was 67 %. This in sacco experiment suggested that about 62 % of duckweed protein would normally escape rumen fermentation.