Observing Kelp as a Methane-Reducing Feed Additive in Ruminants

Abstract

Research has focused on reducing methane emissions in ruminants through feed additives like kelp. This study investigates the effects of different kelp doses (0, 1, 3, and 5% on a dry-matter basis) on nutrient digestibility, rumen fermentation, and methane emissions in vitro, using a total mixed ration (TMR) for lactating dairy cattle. We hypothesized that kelp inclusion, regardless of dose, would lower methane production. Rumen fluid was collected from 3 ruminally cannulated Holstein dairy cows, 2h after morning feeding, and added to buffered medium. TMR was substituted with kelp according to treatment percentages and incubated with 52mL of buffered ruminal fluid under CO2 at 39°C for 24 or 48h. The experiment utilized a completely randomized block design, with three independent runs as the blocking factor each with three replicates per treatment. Measurements, including gas production, pH, and dry matter disappearance (DMD), were analyzed using PROC GLIMMIX in SAS 9.4. Kelp inclusion did not affect methane production (P = 0.85), with similar values seen across treatments. Likewise, DMD (P = 0.85) and ruminal pH (P = 0.49) were not influenced by kelp supplementation, indicating no adverse effects on nutrient digestibility or fermentation conditions. Ammonia-N concentrations were also largely unaffected, although a tendency for reduced ammonia-N at the low inclusion level was observed (P = 0.08). Overall, kelp supplementation up to 5% of dietary dry matter did not reduce methane production or alter rumen fermentation characteristics in vitro, suggesting limited efficacy of kelp as a methane mitigation strategy under these conditions.