Digestibility and Nutritional Value of Microalga Tetraselmis sp. for Weaner Piglets

Twenty-four male piglets were randomly assigned to four dietary treatments, with increasing Tetraselmis sp. incorporation levels (0%, 5%, 10%, and 15%). Following a 4-day adaptation period to metabolic cages, the animals were used in a 2-week digestibility trial and slaughtered for digestive tract measurements and sampling. The apparent total tract digestibility (ATTD), N balance, small intestine digesta viscosity and histomorphology, and hindgut digesta volatile fatty acid (VFA) profile were determined. Polynomial contrasts were employed to examine linear and quadratic effects of Tetraselmis sp. dietary incorporation. The ATTD of most macronutrients and N retention efficiencies decreased linearly (p < 0.05) with Tetraselmis sp. dietary inclusion. The ileum villi height increased linearly (p < 0.001) and the hindgut VFA concentration increased linearly (p < 0.05) with dietary Tetraselmis sp. inclusion. The ATTD values estimated for Tetraselmis sp. biomass using the regression method were 68.3% ± 3.86 for dry matter (DM), 66.1% ± 5.11 for N, and 61.3% ± 4.28 for gross energy. The values calculated for digestible and metabolizable energy (MJ/kg DM) and digestible crude protein (% DM) for Tetraselmis sp. were 9.0, 8.8, and 18.3, respectively. Tetraselmis sp. biomass had lower ATTD values when compared to protein sources commonly used in swine nutrition.