ABSTRACT Yucca schidigera extract (YSE) has received much interest in the application of manure deodorization and hazardous gas mitigation in livestock rearing conditions. The main objective of this review article was to summarize the current knowledge regarding YSE towards its gas mitigation from livestock excrement. Saponins have been considered to be vital components of YSE in odor control and gas reduction in intensive farming industry due to their potentials in lowering methane for ruminants and ammonia for monogastric animals. This review article mainly covered the studies in ruminants, especially focused on in vitro environment. It also summarized possible reasons of the conflicting results among studies from the perspective of experimental design such as incubation time (in vitro) or storage time of manure, and some other factors such as feed source and dietary composition. In addition to traditional dietary inclusion of YSE alone, recent studies prone to apply YSE in new ways such as combining it with other natural compounds or using it to treat manure directly. Until now, there are still controversies in terms of the effectiveness of YSE in intensive-farming environment among researches, therefore further deeper studies on the expression of YSE bioactivity are needed, especially on the molecular level.
An in vitro experiment was conducted to study the effects of chitosan on the secretion of cytokines and expression of inducible nitric oxide synthase mRNA in peritoneal macrophages of broiler chicken. In the experiment, peritoneal macrophages were incubated for 24 h in culture medium supplemented with 0 (control), 40, 80, 160 and 320 µg/mL chitosan. The results showed that chitosan tended to increase quadratically the levels of interleukin-1 (P = 0.093) and interleukin-2 (P = 0.106) in the culture fluid of peritoneal macrophage. Chitosan also significantly enhanced inducible nitric oxide synthase mRNA expression of peritoneal macrophage in a quadratic dose-dependent manner (P < 0.05) and tended to promote quadratically the secretion of nitric oxide (P = 0.053) and inducible nitric oxide synthase (P = 0.157) in peritoneal macrophages. This result implied that one of the mechanisms by which chitosan modulated immune functions in chickens might be chitosan activating expression of inducible nitric oxide synthase and then improving the secretion of nitric oxide.