A1 Optimize the protein intake of cattle
Measure | Sector | Net Effect | Impact | Reliability | Tech. rqmt. | |||||
---|---|---|---|---|---|---|---|---|---|---|
NH3 | N2O | NOx | Nr to water | N2 | ||||||
A1 Optimize the protein intake of cattle | Sector Livestock farming | Net Effect 1 | NH3 1 | N2O 1 | NO2 | Nr to water 1 | N2 1 | Reliability Robust | Tech. rqmts. Medium |
Overview
Animal feed often incorporates protein levels that exceed minimal growth requirements (Bittman et al., 2014; Sutton et al., 2022). Lowering protein consumption in cattle for effective nitrogen mitigation entails the strategic manipulation of dietary components (Figure 1). By finely tuning the protein content of cattle feed to align with the precise nutritional requirements of the animals, excessive nitrogen excretion can be curbed. This goal can be attained through the implementation of precision feeding strategies that tailor protein intake to the distinct growth stage, physiological demands, and production objectives of the cattle. Employing advanced nutritional modelling and analysis, alongside a judicious selection of protein-rich feed ingredients, allows for the formulation of diets that optimise amino acid profiles and overall nutrient utilisation. Additionally, the integration of cutting-edge technologies, such as rumen-protected amino acids and additives that enhance microbial protein synthesis, contributes to the reduction of nitrogen wastage while simultaneously promoting optimal cattle performance and welfare (Tan et al., 2021). This holistic approach not only mitigates nitrogen emissions but also reflects a commitment to sustainable and resource-efficient cattle production systems.
Lowering protein consumption of predominantly grazing livestock, can be more difficult to apply as feeding can be difficult to regulate. However, emissions from pastures are generally low (increased grazing itself is a nitrogen mitigation measure). Grasslands containing leguminous species (like clover or lucerne) tend to have elevated protein content, potentially leading to excessive dietary nitrogen for livestock. Strategies aimed at reducing herbage protein content include: maintaining a balanced nitrogen fertilisation approach; allowing animals to graze or harvest the grassland at a later physiological growth stage; and adjusting the composition of grassland-based systems, which might involve incorporating supplementary feeding with low-protein feeds.
This measure is considered a robust and intermediate tech measure to reduce nitrogen losses from cattle farming systems.
Figure 1. Cows feeding in barns in Hamberg, Germany. Photograph by guvo59 on www.pixabay.com
Measure Efficiency
Taking into account animal welfare and production concerns, a reduction of 1% in the absolute protein content of animal feed generally corresponds to a potential decrease in ammonia emissions of 5%–15% from animal housing, manure storage, and manure application to land (Sutton et al., 2022). This is influenced by urine and manure pH levels. In addition to curbing ammonia, adopting a low-protein animal feeding approach also effectively reduces nitrous oxide emissions and boosts nitrogen utilisation efficiency in animal production.
The average crude protein content of diets for dairy cattle should not exceed 15–16% in the dry matter (DM) (Broderick, 2003; Swensson, 2003). Young animals and high-productive animals require more protein concentration than older, less-productive animals. Special emphasis is placed on the nutritional needs of lactating cattle, requiring higher levels of nutrients, due to the demands of milk production. Dairy cattle in early lactation may consume >30 kg feed/day with a crude protein concentration of 16-18%. For beef cattle over six months old, protein intake could be further reduced to 12% (Sutton et al., 2022). Phase feeding can gradually decrease dairy diet protein content from 16% of DM before parturition to below 14% in late lactation; Phase feeding in beef cattle can gradually lower diet protein from 16% to 12% over time. Bittman et al., (2014) provide further details on recommended ranges broken down into low, medium and high ambition levels. These values serve as indicative target ranges, subject to potential adjustments based on local conditions.
Increasing energy/protein ratio via older grass or supplemented grass with high-energy feeds (e.g., maize silage) effectively cuts crude protein, yet this might be limited in grassland systems due to grass quality issues and purchase costs. Grass-based diets tend to have a protein surplus due to rich grass content, contributing to high nitrogen excretion, which is highest with intensively fertilised young grass or grass-legume mixtures. Extending grazing periods reduces ammonia emissions per animal offering a strategy to curb emissions, although careful grazing management should be followed to avoid potential elevation of nitrate leaching and nitrous oxide emissions.
For grassland-based ruminant production systems, the feasibility of this strategy may be limited, as older grass may reduce feeding quality. However, certain low-protein diets might contain elevated levels of fibre, which can stimulate the production of methane in ruminants (Dalgaarda et al., 2015). Methane is a potent greenhouse gas, and ruminants are major contributors to global methane emissions. The objective here is to identify the optimal protein and fibre levels within ruminant diets to minimise both ammonia and methane emissions (Hristov et al., 2019; van Gastelen et al., 2019). Particularly for ruminants, achieving a balance between protein degradability (and potentially tannins) and energy levels, including high sugar concentrations, is crucial. These measures may enhance palatability, intake, and even contribute to the ensiling process, thereby reducing losses due to spoilage.
How to implement
The following steps should be considered when developing plans to decrease the dietary protein intake of cattle to mitigate ammonia emissions from manures:
- Nutritional Evaluation: Assess the current nutritional requirements of the cattle based on their age, growth stage, and production goals. Consult with a qualified livestock nutritionist to determine the optimal dietary protein levels that meet the animals' needs while minimising excess nitrogen excretion.
- Gradual Transition: Implement changes gradually to avoid sudden disruptions in cattle health and performance. Gradually reduce the protein content of the diet over a period of time, allowing the rumen microbes and cattle's digestive system to adapt to the new composition.
- Balancing Amino Acids: While reducing protein levels, ensure that essential amino acids required for optimal cattle growth and productivity are adequately provided. This helps maintain animal performance while lowering the overall protein content.
- Precision Feeding: Utilise precision feeding techniques to customise diets for individual cattle, optimising protein levels according to each animal's specific needs and production stage.
- Appropriate Feed Ingredients: Select feed ingredients that are lower in protein but still provide necessary nutrients. Incorporate alternative protein sources that align with the reduced protein target.
- Rumen Health and Function: Monitor and manage rumen health during the transition to lower protein diets. Ensuring proper rumen function supports efficient digestion and utilisation of nutrients.
- Supplements and Additives: Consider using additives or supplements that enhance nitrogen utilisation and reduce ammonia emissions. These could include feed additives that promote microbial protein synthesis in the rumen.
- Record Keeping: Keep detailed records of feed formulations, cattle performance, and health during the transition. This data will help evaluate the effectiveness of the dietary changes.
- Environmental Management: Implement manure management practices that complement the lower protein diet. Properly manage manure storage, handling, and application to minimise nitrogen losses.
- Monitoring and Adjustments: Continuously monitor cattle performance, health, and manure quality post-dietary change. Make adjustments as needed to ensure both cattle well-being and ammonia reduction goals are met.
- Research and Expertise: Collaborate with livestock nutritionists, veterinarians, and extension services to ensure that the dietary adjustments align with best practices and scientific insights.
- Cost-Benefit Analysis: Evaluate the economic implications of lowering protein intake, considering potential savings in feed costs and potential improvements in environmental performance.
Benefits
Implementing a strategy to decrease the dietary protein intake of cattle in order to mitigate ammonia emissions from manures offers several significant benefits, which include:
It's essential to weigh these benefits against the associated costs and challenges to make informed decisions about adopting this approach. Collaborating with experts in cattle nutrition, environmental management, and livestock health will help optimise the implementation of this strategy for maximum positive impact.
Costs
Captial Costs
The capital costs of decreasing the dietary protein intake of cattle to mitigate ammonia emissions from manures can vary depending on the specific strategies and changes implemented. Potential capital costs to consider include the following.
Balancing these capital costs with the potential benefits in terms of ammonia emission reduction and overall operational efficiency will help inform decisions.
Operational Costs
The following potential operational costs should be considered.
It's important to conduct a thorough analysis of operational costs specific to the cattle operation, considering factors such as the scale of the operation, regional variations, and the chosen strategies for lowering protein intake and mitigating ammonia emissions.
Risks
Implementing a strategy to decrease the dietary protein intake of cattle to mitigate ammonia emissions from manures comes with certain risks and challenges that need to be carefully considered:
To mitigate these risks, it's crucial to collaborate closely with experts in cattle nutrition, veterinary care, and environmental management. Conducting trials, monitoring cattle health and performance, and making gradual adjustments can help minimise potential negative outcomes.
References
Bittman, S., M. Dedina, C.M. Howard, O. Oenema, and M.A. Sutton, editors. 2014. Options for Ammonia Mitigation: Guidance from the UNECE Task Force on Reactive Nitrogen. Centre for Ecology and Hydrology, Edinburgh, UK.
Broderick, G.A. 2003. Effects of Varying Dietary Protein and Energy Levels on the Production of Lactating Dairy Cows. J. Dairy Sci. 86(4): 1370–1381. doi: 10.3168/jds.S0022-0302(03)73721-7.
Dalgaarda, T., J.E. Olesena, T. Misselbrook, C. Gourley, E. Mathiasd, et al. 2015. Methane and Ammonia Air Pollution. Policy Br. Prep. by UNECE Task Force React. Nitrogen.
van Gastelen, S., J. Dijkstra, and A. Bannink. 2019. Are dietary strategies to mitigate enteric methane emission equally effective across dairy cattle, beef cattle, and sheep? J. Dairy Sci. 102(7): 6109–6130. doi: 10.3168/jds.2018-15785.
Hristov, A.N., A. Bannink, L.A. Crompton, P. Huhtanen, M. Kreuzer, et al. 2019. Invited review: Nitrogen in ruminant nutrition: A review of measurement techniques. J. Dairy Sci. 102(7): 5811–5852. doi: 10.3168/jds.2018-15829.
Sutton, M., C. Howard, K. Mason, W. Brownlie, and Cm. Cordovil, editors. 2022. Nitrogen Opportunities for Agriculture, Food & Environment. UNECE Guidance Document on Integrated Sustainable Nitrogen Management. UK Centre for Ecology & Hydrology, Edinburgh, UK.
Swensson, C. 2003. Relationship between content of crude protein in rations for dairy cows, N in urine and ammonia release. Livest. Prod. Sci. 84(2): 125–133. doi: 10.1016/j.livprodsci.2003.09.009.
Tan, P., H. Liu, J. Zhao, X. Gu, X. Wei, et al. 2021. Amino acids metabolism by rumen microorganisms: Nutrition and ecology strategies to reduce nitrogen emissions from the inside to the outside. Sci. Total Environ. 800: 149596. doi: 10.1016/j.scitotenv.2021.149596.
Authors
Will Brownlie
UK Centre for Ecology and Hydrology, Scotland