| Abstract | In vitro digestion studies were conducted to examine the potential nutritional value of whole (WAB) and lipid-extracted biomass (LEB) from freshwater microalgae from Alberta, Canada. For WAB, protein solubility (PS) was statistically highest and the same (P = 0.109) for Chlorellavulgaris at 84% and Micractiniumreisseri at 78%, lowest (P < 0.001) for Nannochlorisbacillaris at 64% and intermediate for Tetracystis sp. at 73%. Dilute pepsin digestibility (DPD) was highest (P < 0.001) for C. vulgaris at 80% and lowest (P < 0.001) for N. bacillaris and Tetracystis sp. at 60–64%, which were the same (P = 0.075) and M. reisseri was intermediate at 72%. Two-phase gastric/pancreatic digestibility of protein (GPDProtein) and energy (GPDEnergy) were highest (P < 0.001) for M. reisseri at 78 and 57%, respectively, lowest (P < 0.001) for N. bacillaris and Tetracystis sp. at 49–52 and 41–43%, respectively, which were the same (P = 0.101 and 0.058, respectively) and C. vulgaris was intermediate at 69 and 52%, respectively. For LEB, PS was highest (P < 0.001) and the same (P = 0.088) for C. vulgaris and M. reisseri at 72–76%; which were higher (P < 0.001) than N. bacillaris and Tetracystis sp. at 60–62%, which were the same (P = 0.405). Similarly, DPD was highest (P < 0.001) and the same (P = 1.000) for C. vulgaris and M. reisseri both at 69%; which were higher (P < 0.001) than N. bacillaris and Tetracystis sp. at 58–62%, which were the same (P = 0.083). GPDProtein was highest (P < 0.001) and the same (P = 0.944) for M. reisseri and C. vulgaris at 79–80%, lowest (P < 0.001) for N. bacillaris at 50% and intermediate for Tetracystis sp. at 55%. GPDEnergy was highest (P < 0.001) for C. vulgaris at 69%, followed by M. reisseri at 61%, Tetracystis sp. at 48% and lowest (P = 0.006) for N. bacillaris at 45%. Organic matter digestibility (OMD) of a ruminant control diet was 45% and not significantly affected (P ≥ 0.071) by dietary algal supplementation with an average OMD of 36% when incorporated at 50% forage replacement (equivalent to 25–43% of the diet); except Tetracystis sp. LEB which decreased (P = 0.020) OMD to 28%. Dietary inclusion of all biomass at 100% forage replacement (equivalent to 51–85% of the diet) decreased (P ≤ 0.026) OMD to an average of 28%; except M. reisseri LEB which did not significantly affect (P = 0.921) OMD at 41%. Apparent metabolizable energy (aME) content of the control diet was 3.7 MJ kg− 1 and was not affected (P ≥ 0.179) by algal supplementation at an average of 3.1 MJ kg− 1, although a general trend of decreased aME with increased dietary levels was noted. Methane production from 48 h in vitro fermentation of diets with varying levels of WAB was 2.8–3.3 mol− 10 and was the same (P ≥ 0.429) as the control diet at 2.9 mol− 10. However, LEB at all levels decreased (P < 0.001) methane production by about 50% to 0.9–1.2 mol− 10, which suggests the potential for abating enteric methane emissions from ruminants by feeding microalgae, unrelated to its lipid content. |
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