The cornerstone of efficient feed conversion in cattle, sheep and other ruminants is the rumen. As the primary organ responsible for the conversion of feed to nutrients that the animal can use, there is considerable focus on rumen fermentation to increase yields and feed efficiency. Feed costs are the largest variable cost in beef production. New genomics techniques present an opportunity to understand better how the ruminant microbiome contributes to feed conversion so that it can be steered towards higher yields.

In one extensive study that investigated differences in the rumen microbiome of beef cattle in the context of feed conversion efficiency and weight gain, several interesting differences were found between high-yielding and low-yielding groups.2 In particular, animals with a higher daily bodyweight gain had a significantly higher proportion of Firmicutes phylum bacteria. Interestingly, a higher relative abundance of Firmicutes in humans is associated with obesity, a result of more efficient production of short chain fatty acids from dietary fibre, which increases the available energy content of the diet.3 Firmicutes was also positively associated with weight gain in meat goats.4 Similar results were found in a study of dairy cattle: milk fat content increased in animals with a higher proportion of Firmicutes, therefore increasing milk yield.5 Changing the macronutrient composition of the ruminant diet was able to favourably change the composition of the rumen microbiota towards a higher Firmicutes content,6 showing that it is plausible to modulate the rumen microbiome towards a more energy efficient profile.

Rumen microbiome in health & disease

Ruminants such as cows, sheep goats and deer are named for the rumen, the first and largest stomach, and primary fermentation “tank” for these animals. The rumen microbiome is incredibly diverse and complex, with a high number of different microbes including protozoa, bacteria, fungi and archaea. The rumen affects namely feed conversion and emissions, and can also influence the health of the animal. Genomic techniques have been instrumental in the first steps towards unravelling the complexity of the rumen.

Ruminants on a grass-based diet are dependent on the ability of the rumen microbiome to break down the cellulose in this relatively nutrient-poor feed to short chain fatty acids, the primary source of energy for the grazer. Certain bacteria, such as some Fibrobacter and Ruminococcus species, are considered to be desirable due to higher ability to digest cellulose and increasing their activity should result in better ruminant performance. However, it has been difficult to actually improve yields by feeding microbes shown to be efficient cellulose converters. Competition with other microbes is thought to be the reason behind poor establishment of probiotics in ruminants.

On the other hand, some techniques to modify the ruminant microbiome have proven to be useful for animal health. For example, it is possible to avoid intestinal problems that arise from switching a grass-fed animal to a grain diet by inoculating with rumen fluid from a grain-fed animal. Anti-nutritive factors from some pasture animals can also be broken down by inoculating with bacterial strains that have been developed for this task, thus assisting in keeping ruminants healthy. Commensal microbes are essential in normal immune function of ruminants: they stimulate intestinal cells to maintain their barrier function and can block the attachment of pathogens to the gut. Microbiome modulation could strengthen these functions.

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Meet Aleksandrina Patyshakuliyeva!

Aleksandrina Patyshakuliyeva is one of our PhD-level product managers. She did a PhD in fungal physiology at Westerdijk Institute, investigating plant biomass utilization by fungi. She has gained a lot of experience working as a postdoctoral researcher at Utrecht University, Wageningen University and NIOO-KNAW and was a visiting researcher in INRA, France and Helsinki University, Finland. During this time, her research centred on applications in sustainable food production, sustainable agriculture and bioremediation. She has explored production of extracellular enzymes, organic acids, siderophores, metabolic pathways and regulators controlling the microbial response to the substrates.

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