Resumen
We investigated growth performance and ruminal fermentation associated with gastrointestinal nematode (GIN) Haemonchus contortus in lambs and in vitro ruminal fermentation of mallow, chamomile, fumitory, wormwood (Herbmix), and chicory using inoculum from GIN-infected lambs. Twelve lambs were equally divided into two groups: uninfected animals (CON) and animals infected (INF) with approximately 5000 third-stage larvae derived from the MHCo1 strain of GIN H. contortus. Two lambs per group were killed on days 48, 49, and 50 after infection and ruminal content was collected separately from each lamb. Batch cultures of ruminal fluid from CON and INF were incubated for 24 h in vitro with 0.25 g meadow hay, Herbmix, and chicory using an in vitro gas production technique. Daily weight gain was relatively lower in the INF than the CON group, but not significantly (72.6 vs. 130.1 g/day). The ruminal populations of protozoa, bacteria, total Archaea, Methanobacteriales, and Methanomicrobiales were significantly higher in the INF than in the CON group. The substrates affected the concentrations of n-butyrate, iso-butyrate, n-valerate, iso-valerate, ammonia-N, total gas, and methane (p < 0.001) in vitro. GIN infection affected fermentation and microbial population in the rumens of the lambs, and chicory was a promising substrate to modulate ruminal fermentation in vitro.