Lemna Protein Concentrate (LPC) is derived from the leaves of duckweed, one of several rapidly-growing aquatic plants of the genus Lemna. LPC is produced by de-oiling and de-hydrating leaves and stems of the duckweed plant. Duckweed has a number of advantages as a protein source. It is relatively inexpensive to produce and requires less growing area and fewer inputs than other plant protein sources such as soybean products. In addition, LPC has a favorable amino acid profile for use in swine diets. No published data exist on the nutritional value of LPC as fed to pigs. Therefore, two experiments were conducted to determine the concentration of digestible and metabolizable energy and the digestibility of phosphorus in Lemna Protein Concentrate.

The first experiment was designed to determine the apparent total tract digestibility of gross energy and the concentration of digestible and metabolizable energy in Lemna Protein Concentrate, and to compare it with fish meal and soybean meal. Thirty-two weanling barrows with an average initial body weight of 16.8 kg were fed four diets. The basal diet contained 96.4% corn (as-fed basis). The three experimental diets contained 25.0% LCP, 25.0% fish meal, and 35.0% soybean meal respectively.

The apparent total tract digestibility of gross energy did not differ between corn, fish meal, and soybean meal, and was greater (P < 0.01) in those ingredients than in LPC (Table 2). The concentration of digestible energy did not differ between LPC and soybean meal on either an as-fed or dry matter basis. DE concentration was greater on an as-fed basis (P < 0.01) in LPC than in fish meal, and greater (P < 0.01)  on a dry matter basis in soybean meal than in fish meal. Corn contained the least DE on both an as-fed and dry matter basis.

The concentration of metabolizable energy was greatest (P = 0.03) on an as-fed basis in LPC, fish meal, and soybean meal, which did not differ from each other. The concentration of ME in corn was less than in soybean meal on an as-fed basis, but not significantly different than the ME in LPC and fish meal. ME concentration was the same on a dry matter basis between the four experimental ingredients.

Experiment 2 was designed to determine the apparent (ATTD) and standardized (STTD) total tract digestibility of phosphorus in Lemna Protein Concentrate, fish meal, and soybean meal. Twenty-four weanling barrows with an average initial body weight of 10.5kg were fed three cornstarch-based diets. The 3 diets were formulated by mixing cornstarch and sugar with either LPC, fish meal, or soybean meal.

Daily phosphorus intake, phosphorus excretion, and absorbed phosphorus were greater (P < 0.01) in pigs fed soybean meal than in pigs fed LPC, and greatest in pigs fed fish meal (Table 3). Apparent and standardized total tract digestibility of phosphorus did not vary among pigs fed the three experimental diets, although there was a tendency (P = 0.07) for the STTD of phosphorus to be greater in LPC than in soybean meal.

• The concentration of digestible energy in LPC is comparable to that in soybean meal, and greater than the DE in fish meal and corn.
• The concentration of metabolizable energy in LPC is comparable to that in fish meal, soybean meal, and corn.
• The digestibility of phosphorus in LPC is comparable to that in fish meal and soybean meal.

Table 1. Analyzed nutrient composition of corn, Lemna protein concentrate, fish meal, and conventional soybean meal (SBM), as-fed basis

¹AEE = acid hydrolyzed ether extract.

Table 2. Concentration of digestible and metabolizable energy and apparent total tract digestibility (ATTD) of energy in corn, Lemna Protein Concentrate (LPC), fish meal, and soybean meal (SBM), as-fed basis

^a-c Means within a row lacking a common superscript letter differ (P < 0.05).

Table 3. Apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of phosphorus in Lemna protein concentrate (LPC), fish meal, and soybean meal (SBM)

^a-c Means within a row lacking a common superscript letter differ (P < 0.05).

¹Basal EPL = basal endogenous phosphorus loss.

This research report is based on unpublished research by O. J. Rojas and H. H. Stein.