Rumen Manipulation Strategies towards Enhancing Feed Efficiency and Reducing Methane Emissions in Ruminants Fed Low Quality Feeds: A Review

Rumen manipulation is a specialized technique employed to modify or optimize the rumen environment and its microbial ecosystem to enhance the efficiency of feed utilization, thereby improving animal productivity and reducing the production of undesirable byproducts, such as methane. This methane loss is 5-12% of gross energy intake of animal and contribute to the global warming. India's 20th livestock census documented that India has the world's largest livestock population. Maintaining such a large number of livestock using green fodder and hay is not possible because less than 5 percent of the total cultivated land is used for fodder production. Therefore, livestock feeds in India primarily comprises cereal crop residues, low-quality roughages (tropical forages), and lignocellulosic agro-industrial byproducts, due to their abundance and low cost. However, these materials exhibit low digestibility, lower energy value and also contain toxicants resulting in a significant portion of the feed remaining undigested. These factors are significant contributors to the low productivity of dairy animals. Therefore, manipulating ruminal fermentation is very crucial. This article explores various genetic and non-genetic approaches to optimize rumen function. Genetic interventions, such as genetic engineering of naturally occurring rumen bacteria and the introduction of novel microbial species or strains, offer promising avenues for enhancing cellulose degradation, neutralizing toxins, and mitigating ruminal acidosis. However, challenges such as low microbial viability, substantial expertise requirements, limited efficacy rates, and ethical concerns about potential risks to animal and human consumers hinder their widespread adoption. Non-genetic approaches include Use of Ionophore compounds, Organic acids, Defaunation agents, and Probiotcs. These approaches provide practical solutions to tackle the nutritional challenges associated with tropical forages and low-quality feeds. These methodologies enhance feed efficiency, reduce methane emissions, and improve overall animal productivity.