Ruminant Nutrition: Ruminal Metabolism

Cultivation of algae for biofuel would result in the production of significant amounts of post-extraction algal residue (PEAR). The economic viability of algae as source of biofuel is dependent on deriving value from PEAR. Livestock feed is an attractive option for PEAR because of the successful utilization of other co-products by ruminants. While sufficient quantities of PEAR were not available for analysis, we evaluated 2 strains of algae that, based on their lipid content and growth characteristics, possess potential as a source of biofuel. Algae samples, unknown wild algae (WA) and Neochloris oleoabundans (NO), were analyzed for ash, crude protein, amino acid profile, total fat content (ether extract), fatty acid profile, fat soluble vitamins, macroand micro-minerals, and heavy metals (n = 1). Samples were observed to have relatively high levels of ash, 30.5 and 43.2% for WA and NO, respectively. As expected, Na content of each sample was high, 10.3 (WA) and 10.8% (NO). The Ca and P contents were 0.67 and 0.43% for WA and 1.02 and 0.26% for NO, accordingly. Algae samples WA and NO contained 34.2 and 48.6 ppm Cu, 848 and 756 ppm Fe, and 20.1 and 62.3 ppm Zn, respectively. WA and NO contained significant quantities of aluminum at 840 and 858 ppm, accordingly. Analysis of algal CP content, 17.4 WA and 20.6% NO, indicates that PEAR may serve as a source of N in ruminant diets. Samples contained similar amounts of methionine (0.31 and 0.32%; WA and NO, respectively) and lysine (1.00 and 1.18%; WA and NO, respectively). Total fat content was 9.1 and 11.8% WA and NO, respectively. Fatty acids (% total fat) were profiled for WA and NO, correspondingly: Palmitic, 21.3 and 32.0; Oleic, 34.1 and 15.6; Trans-vaccenic, 7.7 and 5.6; Linoleic, 11.3 and 19.8; α-Linolenic, 16.3 and15.4%. Vitamin A content was high for both samples, with WA measuring 6614 and 5203 IU/kg for NO. Vitamin E content was 56.5 for WA and 87.7 IU/kg for NO. Future nutritive evaluations of algae and the resulting PEAR should focus on its value as a source of N in ruminant diets.