Under heat stress conditions, selenium nanoparticles promote lactation through modulation of rumen microbiota and metabolic processes in dairy goats

This study aimed to investigate the effects of dietary supplementation with Selenium nanoparticles (SeNPs) on lactation performance, rumen microbial communities, and metabolism in dairy goats under heat stress conditions. Twenty Guanzhong dairy goats with the same parity, similar lactation period (120 ± 15 days), and similar milk yield (1.20 ± 0.16 kg/day) were randomly divided into two groups, with 10 replicates in each group. The control group was fed a standard diet, while the experimental group was supplemented with 0.5 mg SeNPs/kg DM based on the standard diet. The pretrial period lasted for seven days, followed by a 30-day trial period. The results showed that dietary supplementation with SeNPs significantly increased milk yield, milk fat and lactose content in dairy goats, under heat stress conditions. SeNPs significantly altered the composition of the rumen microbiota, increasing the relative abundance of Prevotella and Ruminococcus while decreasing the relative abundance of Succiniclasticum. This enhanced the rumen's ability to degrade starch and fiber under heat stress conditions. Non-targeted metabolomic analysis revealed a total of 119 differential metabolites between the two groups, indicating changes in rumen metabolism. Further correlation analysis indicated that Rumen bacterium R-21 was positively correlated with propionate, while Ralstonia insidiosa was negatively correlated with γ-glutamylcysteine. Additionally, several differential microbes, including Succinivibrio dextrinosolvens, Rummeliibacillus pycnus, Ralstonia insidiosa, and Prevotella sp BP1-56, were significantly correlated with milk composition. In conclusion, dietary supplementation with SeNPs can positively impact milk yield, milk components, and metabolism in dairy goats by improving the composition of the rumen microbiota under heat stress conditions.