Digestibility of crude fat and energy from a micro-algae meal for nursery pigs

Abstract Text: Alltech SP1 is derived from a heterotrophically-grown micro-algae meal that contains at least 67% fat (CCAP 4087/2; Alltech, Inc.). Fats are commonly added to swine diets as sources of energy to support growth and optimize feed efficiency. However, for accurate feed formulation, knowledge of the energy and fat digestibility of a feedstuff is needed. The objective of this study was to quantify the digestibility of crude fat and energy from SP1 for nursery pigs. Diets containing 0, 2, or 4% SP1, with no other added fat, were fed to 12 individually housed nursery pigs over 3 one-week periods in a Latin square design, thus providing 12 replicates of each diet. Pigs were acclimated to the metabolism pens and dry diets for one week immediately post-weaning before the first dietary treatment began. Grab samples of feces were collected on days 6 and 7 of each dietary treatment period. The apparent total tract digestibility (ATTD) was determined by analyzing for the concentration of acid insoluble ash (AIA) in the feed and feces. Diets were formulated based on the predicted energy content of SP1 (calculated based on chemical composition and according to Powles et al., 1995) by decreasing the inclusion of corn as the inclusion of SP1 increased. As expected, the gross energy of the diets increased with the inclusion of SP1 (3,726 vs. 3,809 vs. 3,898 kcal/kg; P < 0.01). The ATTD of energy did not differ (P > 0.10) between dietary treatments, averaging 82%. Therefore, the diet containing 4% SP1 provided 35 kcal/kg more metabolizable energy (ME) than the 0% SP1 diet. Crude fat concentration was highest (P < 0.05) in fecal samples from the pigs fed the 4% SP1 diet. However, digestibility of crude fat was not different (P > 0.30) between dietary treatments. Although, there were no differences in pig performance within each period, the ATTD of energy was greater (P < 0.05) in period 3 compared to period 1, demonstrating the effect of the growth and development of the gastrointestinal tract on energy digestibility. Dietary supplementation with up to 4% SP1 did not alter ATTD of crude fat or energy in nursery pigs. Consequently, the predicted energy value for SP1 – 5,300 kcal ME/kg was demonstrated to be an appropriate value to utilize for feed formulation.

Keywords: algae, energy, digestibility