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

## TL;DR

This study evaluates the nutritional value of Tetraselmis sp. microalga for weaner piglets, finding it has lower digestibility than common protein sources.

## Contribution

The study provides the first detailed characterization of Tetraselmis sp. as a feedstuff for swine, filling a critical knowledge gap.

## Key findings

- Digestibility of macronutrients and nitrogen retention decreased with higher Tetraselmis sp. inclusion.
- Ileum villi height and hindgut volatile fatty acid concentration increased linearly with Tetraselmis sp. inclusion.
- Digestibility values for Tetraselmis sp. were lower than those of conventional protein sources in swine diets.

## Abstract

One of the most significant challenges in present-day animal nutrition is the establishment of novel sustainable ingredients, particularly protein sources. Due to their promising composition and local production, microalgae are considered a suitable alternative feedstuff. However, a significant gap in the available information about the feeding value of microalgae still remains, with no thorough characterization of their nutritional value in the framework of swine nutrition. This information is nonetheless essential for its practical use in diet formulations for this species. This research addresses this gap by evaluating the nutritional value of Tetraselmis sp. biomass when included in the diets of weaner piglets up to 15%, thus ascertaining its relevance to the nutrition of these animals.

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.