The impact of forage on carbon emissions in ruminants

As the commitment to net zero by 2050 grows ever stronger, so does the spotlight and pressure on producers to reduce livestock emissions. Improving overall efficiency – specifically, efficiency fibre utilisations – helps honour this commitment, while acting as a means to support the sustainability of livestock production.

For many years enteric methane emissions have been pointed out as the main source of carbon emissions in the livestock industry, hence the growing pressure for reducing methane emissions associated with ruminants. Although fibre highly contributes to enteric methane emissions, fibre remains a key component in maintaining rumen function and cow health, and an extremely important energy source – a substantial part of the energy for milk production is extracted from fibre.

So, producers are faced with ongoing environmental pressures, while balancing commercial pressures of having to increase performance and harvest more energy. Suggestions for the industry for the former issue have included reducing methane through alternative feeds, and reducing food loss and waste – which is where forage presents an interesting solution, producing more from less and making the best use of resources.

Ingesting forage – grass, silages, legumes and more – allows ruminants to transform these non-human-edible energy sources into energy, as they can digest carbohydrates contained in plant cell walls. And, in turn, humans consume this in the form of meat and milk. Making greater use of forage also allows the use of resources which would not be consumed otherwise – a unique form of “upcycling”.

FORAGE QUALITY CHARACTERISATION
Forage is essential to promote rumen function and health in cattle. We know plant cell wall digestibility is often lower than 50%. With a proper characterisation and valorisation of the nutrients and digestible energy contained in forage, forage utilisation efficiency and ration formulation can be improved, and in turn contribute to a better feed efficiency and feed cost.

Portable near infrared (NIR) instruments are now used on farm to determine forage quality. When analysing forage by NIR, nutritionists can quickly adjust formulation. As an example, we compared the quality of grass silage from the UK in 2021 and 2022. Figure 1 shows the lower metabolizable energy (ME) content as a percentage of dry matter and Figure 2 shows neutral detergent fibre (NDF) content as a percentage of dry matter – which were promptly noticed upon harvest with the NIR. This coincided with a dry season in 2022, which negatively impacted the ME content of grass silage, while the NDF level was higher as compared to 2021.

PRE-DIGESTION OF FIBRE WITH VISTAPRE-T TO RELEASE MORE ENERGY
A crude fermentation extract from Trichoderma reesei (VistaPre-T) can be used in total mixed rations to get more energy from forage by forming pits and roughening the fibre surface, hence speeding up the microbial attachment and colonisation, assuring reduced lag time, and greater fibre digestion. A study demonstrated an increase in NDF and ADF digestibility in an in vitro rumen fermentation model. This was associated with a faster attachment and colonisation of fibre-degrading microbes in the rumen, then resulting in a greater utilization of both the hemicellulose and cellulose.

FECAL NDF AND STARCH TO EVALUATE CARBOHYDRATE UTILISATION
Fecal starch analysis is a method used to evaluate total tract starch digestibility (TTSD). When fecal starch content is lower than 3%, the value is associated with good TTSD. Portable NIR can now be used to measure the fecal starch content in fresh feces, on farm. This enables a quick evaluation of the quality of the ration, and eventually adjust formulation.

Beyond starch, fecal NDF level can be used to evaluate the efficiency of energy utilization. As an example, fresh fecal samples were collected in 8 groups of cows from 4 different dairy farms in the UK. The NIR predictions indicated an optimal fecal starch levels below 3% in all the groups of cows, whereas fecal NDF levels were high relative to dietary NDF. After VistaPre-T application, the NIR predictions indicated an 8% average reduction in fecal NDF, which demonstrated the efficiency of VistaPre-T in increasing fibre utilisation.

TWO FORMULATION STRATEGIES TO INCREASE THROUGHPUT AND LOWER CARBON FOOTPRINT WITH VISTAPRE-T
VistaPre-T can be formulated into the total ration to save cost. In dairy diets, VistaPre-T can generate approximately 10 MJ of additional energy (coming from 0.8 MJ energy uplift per kg of forage DM, given a cow consumes 12.5kg of forage DM per day on average). This extra energy iu equivalent to 300g of protected fat per cow/day.

A study was performed involving 147 Holstein-Friesian dairy cows in the UK. After assigning the energy uplift value to VistaPre-T, the least-cost reformulation allowed to reduce the ground maize, molasses and protected fat usage, while adding more grass silage. In addition to a 9% increase in milk yield with no effect on milk composition, VistaPre-T resulted in a 15% reduction in the carbon footprint of fat and protein corrected milk.

Alternatively, VistaPre-T can be applied on the top of the ration to enable extra energy supply and improved performance. In another study, 350 milking cows maintained as one group were fed a maize and grass silage-based ration, with VistaPre-T applied on the top of the ration. The average milk yield (kg/cow/day) in the pre-trial period and after feeding VistaPre-T was recorded and indicated increased milk yield in every stage of lactation.

Average milk yield increase with VistaPre-T per lactation stage. Transition: 0-50 days in milk (DIM), early: 51-100 DIM, Mid: 101-200, Late: 201-400.

CONCLUSION
As the commitment to net zero by 2050 grows ever stronger, so does the spotlight and pressure on producers to reduce livestock emissions. Improving overall efficiency – specifically, efficiency fibre utilisations – helps honour this commitment, while acting as a means to support the sustainability of livestock production. An effective pre-treatment like VistaPre-T helps extract more energy from feed and forage – critical to not only maximising feed efficiency, but also helping producers reduce costs and improve farm profitability; in the long-term, ensuring the sustainability of livestock production.

About Virginie Blanvillain Rivera
Born and raised in France, Virginie Blanvillain Rivera lives in Quebec, Canada. She developed an international experience in the animal feed industry by working in research and development, technology transfer, nutrition and quality assurance. Over the past years, she has been actively involved in the development and implementation of innovative tools and services for nutritionists, producers, integrators and feed mills. She provides training and technical support to the AB Vista network worldwide, while leading the development and continuous improvement of NIR, carbon emissions and lab services.