The growing demand for sustainable animal production is compelling researchers to explore the potential approaches to reduce emissions of greenhouse gases from livestock that are mainly produced by enteric fermentation. Some potential solutions, for instance, the use of chemical inhibitors to reduce methanogenesis, are not feasible in routine use due to their toxicity to ruminants, inhibition of efficient rumen function or other transitory effects. Strategies, such as use of plant secondary metabolites and dietary manipulations have emerged to reduce the methane emission, but these still require extensive research before these can be recommended and deployed in the livestock industry sector. Furthermore, immunization vaccines for methanogens and phages are also under investigation for mitigation of enteric methanogenesis. The increasing knowledge of methanogenic diversity in rumen, DNA sequencing technologies and bioinformatics have paved the way for chemogenomic strategies by targeting methane producers. Chemogenomics will help in finding target enzymes and proteins, which will further assist in the screening of natural as well chemical inhibitors. The construction of a methanogenic gene catalogue through these approaches is an attainable objective. This will lead to understand the microbiome function, its relation with the host and feeds, and therefore, will form the basis of practically viable and eco-friendly methane mitigation approaches, while improving the ruminant productivity.

The aim of the present investigation is to determine the nutritional composition of various insects and their potential uses as alternative protein sources in animal diets. The feeding industry requires production systems that use accessible resources, such as feed resources, and concentrates on the potential impacts on production yield and nutritional quality. Invertebrate insects, such as black soldier flies, grasshoppers, mealworms, housefly larvae, and crickets, have been used as human food and as feed for nonruminants and aqua culture while for ruminants their use has been limited. Insects can be mass-produced, parti­cipating in a circular economy that minimizes or eliminates food- and feed-waste through bioconversion. Although the model for formula-scale production of insects as feed for domestic animals has been explored for a number of years, significant production and transformation to being a conventional protein resource remains to be deeply investigated. This review will focus on the nutritional composition of various insects and their potential use as alternative protein sources, as well as their potential use to promote and support sustainable animal production. Furthermore, nutritional compositions, such as high protein, lauric acid omega 6, and omega 3, and bioactive compounds, such as chitin, are of great potential use for animal feeding.

Animal agriculture has been an important component in the integrated farming systems in developing countries. It serves in a paramount diversified role in producing animal protein food, draft power, farm manure as well as ensuring social status-quo and enriching livelihood. Ruminants are importantly contributable to the well-being and the livelihood of the global population. Ruminant production systems can vary from subsistence to intensive type of farming depending on locality, resource availability, infrastructure accessibility, food demand and market potentials. The growing demand for sustainable animal production is compelling to researchers exploring the potential approaches to reduce greenhouse gases (GHG) emissions from livestock. Global warming has been an issue of concern and importance for all especially those engaged in animal agriculture. Methane (CH4) is one of the major GHG accounted for at least 14% of the total GHG with a global warming potential 25-fold of carbon dioxide and a 12-year atmospheric lifetime. Agricultural sector has a contribution of 50 to 60% methane emission and ruminants are the major source of methane contribution (15 to 33%). Methane emission by enteric fermentation of ruminants represents a loss of energy intake (5 to 15% of total) and is produced by methanogens (archae) as a result of fermentation end-products. Ruminants׳ digestive fermentation results in fermentation end-products of volatile fatty acids (VFA), microbial protein and methane production in the rumen. Rumen microorganisms including bacteria, protozoa and fungal zoospores are closely associated with the rumen fermentation efficiency. Besides using feed formulation and feeding management, local feed resources have been used as alternative feed additives for manipulation of rumen ecology with promising results for replacement in ruminant feeding. Those potential feed additive practices are as follows: 1) the use of plant extracts or plants containing secondary compounds (e.g., condensed tannins and saponins) such as mangosteen peel powder, rain tree pod; 2) plants rich in minerals, e.g., banana flower powder; and 3) plant essential oils, e.g., garlic, eucalyptus leaf powder, etc. Implementation of the -feed-system using cash crop and leguminous shrubs or fodder trees are of promising results.