Effect of Spirulina on the Rumen Microbiota and Serum Biochemical Parameters of Lambs

Spirulina (<i>Arthrospira platensis</i>) is rich in a variety of fermentable fibers and prebiotics, which can promote the proliferation of beneficial flora in the intestinal tract of ruminants and optimize the balance of microorganisms in the rumen. The aim of this study was to evaluate whether dietary supplementation with Spirulina has a beneficial effect on the rumen microbial community and serum indices in lambs. For this purpose, 36 lambs with a mean weight of 21.68 kg (standard deviation 1.04 kg) and an age of approximately 5 months (standard deviation 4 days) were selected for the study. The same scale was used for age standard deviation, i.e., 4 days/30.5 days (1 month) = 0.13 months. All lambs were randomly assigned into two treatments, and received non-Spirulina diet as the control (CK treatment) and the Spirulina added diet (Spirulina was added at a rate of 3% of the fresh weight of the diet). The results indicated that the triacylglycerol (<i>p</i> < 0.0001), alanine transaminase (ALT) (<i>p</i> < 0.0001), aspartate aminotransferase (AST) (<i>p</i> < 0.0001), glucose (<i>p</i> < 0.0001), immunoglobulin G (<i>p</i> = 0.0066) and insulin (<i>p</i> = 0.0025) levels were markedly increased in the Spirulina treatment compared to those in the CK treatment. The principal coordinates analysis showed that the bacterial community did not cluster separately between the CK and Spirulina treatments. Firmicutes, Bacteroidetes and Actinobacteria were the dominant members of the community in two treatments. <i>Prevotella</i> were the primary genera, followed by the <i>Lachnospiraceae</i>_NK3A20_group, <i>Olsenella</i>, <i>Succinivibrionaceae</i>_UCG-001 and <i>Ruminococcus</i>, and a significant (<i>p</i> < 0.05) difference was found in <i>Olsenella</i> between the two treatments. These results suggest that the addition of Spirulina is more beneficial for serum biochemical parameters and rumen microbiota of lambs. Overall, these findings contribute to the development of strategies to improve rumen microbial communities for healthy ecosystems on the Mongolian Plateau and provide a scientific basis for the use of Spirulina in feed.