PS2-4. Viability of Kummerowia Stipulacea Seeds After In-vitro Rumen and Abomasal Digestion

Limited information exists on the extent to which cattle contribute to the relocation of viable invasive plant seeds through fecal excretion after being moved between regions. The trial objective was to determine viability of Kummerowia stipulacea (KL) seeds after a two-step in-vitro procedure simulating ruminant rumen and gastric digestion. Daycron polyester bags (5 cm x 5 cm; n = 10) were each filled with KL seeds (n = 200) and sealed. Each bag was incubated along with a total mixed ration substrate (TMR) for 48 h in an In vitro culture using an ANKOM RF gas production system (ANKOM Technology, Macedon, NY) inoculated with fresh rumen fluid. Gas production was recorded continuously during the incubation and substrate was recovered at the end via filtration for DMD calculations. Also after In vitro rumen incubation, dacryon polyester bags were washed and seeds were split into two equal groups. One group was used for germination at end point of rumen, and second group was placed in a dacryon polyester bag (5 cm x 5 cm) and incubated for 4 h in a solution containing HCl and pepsin, representing abomasal digestion. After incubation in the abomasal simulation solution, seeds were washed and germinated. Both Rumen and Abomasal endpoint seeds were germinated on petri dishes in a 20ºC incubator for 7 days. Results for germination, DMD, and gas production were analyzed using lmer package in R. Gas production data was modeled using R to determine gas kinetics for TMR alone compared to TMR plus seeds. Based on germination rate and extent, it was concluded that seed viability was reduced after ruminal and ruminal + abomasal digestion, when compared to undigested seeds (P < 0.01). Digested seeds demonstrated 0.1% germination after both ruminal and abomasal digestion conditions which was significantly reduced from undigested seeds (P < 0.01). Total gas production was greater for jars containing KL seeds and TMR (240 mL ± 2) compared to TMR alone (189 mL ± 3)(P < 0.01). This result suggests that KL seeds are digestible by rumen microbes. The modeled fractional rate constant (k) was reduced in the seed treatment (0.11 h-1 ± 0.001) compared to control (0.19 h-1 ± 0.002; P < 0.01). A decreased fractional rate constant, coupled with increased total gas production and the recovery of intact seeds after digestion, suggests that while complete seed digestion did not occur in vitro, some seed-associated materials were degraded by rumen microbes, potentially influencing seed viability following ruminant digestion without negatively influencing rumen digestion. Results indicate cattle ingestion is not a major pathway for spreading invasive KL, as post-digestion seed viability was minimal (0.1%), though further research on other plant species with differing seed characteristics is warrented.