Assessment of molasses-based additives for methane mitigation in beef cattle

Abstract

Enteric methane (CH₄) mitigation is a priority for pasture-based beef systems, where practical delivery of antimethanogenic additives to grazing cattle remains challenging. Molasses lick blocks (MLBs) have been proposed as a practical strategy to regulate intake and improve additive delivery in extensive systems.

This thesis evaluated novel molasses-based formulations intended for incorporation into MLBs by (i) screening their in vitro antimethanogenic effects and (ii) assessing in vivo responses in growing beef cattle over 70 days. Due to commercial confidentiality and pending intellectual property protection, ingredient identities are not disclosed.

In vitro, four formulations were assessed for effects on rumen fermentation and methane production. One formulation (“Product 3”) showed the strongest response. At 6% inclusion, CH₄ production was reduced by >90%, although digestibility declined. At 4% inclusion, Product 3 reduced CH₄ production by 62% without impairing digestibility, demonstrating the importance of dose optimisation.

The in vivo experiment evaluated Product 3 delivered as a grain-based pellet to growing steers at target intakes of 0, 100, or 200 g/head/day. Methane emissions were measured using a GreenFeed system. Compared with control pellets, CH₄ yield was reduced (P < 0.01) by up to 11.7%, with no adverse effects on dry matter intake, liveweight gain, or feed efficiency.

Overall, Product 3 demonstrated a dose-dependent antimethanogenic effect, achieving substantial methane reductions without compromising animal performance. These findings highlight its potential as a dietary strategy for low-emission beef production and support further evaluation in grazing systems using final MLB formulations.