Increase starch content of the diet
System: Dairy Cattle
Applicability
Mainly applicable for: TMR systems, zero- or low-grazing systems
Not or less applicable for: Less applicable in fully grass-based systems because of limited possibilities to feed starch (during and around milking)
Description
Increasing the amount of starch in the feed ration of animals, for example by feeding more maize silage, whole plant silages or other sources of starch (grains).
Mechanism of effect
Increasing starch in the diet reduces enteric methane emissions because starch is rapidly degraded in the rumen and the rumen environment becomes more acidic with high starch diets which limits methane production. Because of the higher feed intake that can be achieved and the reduced retention time in the digestive system there is less opportunity for the microorganisms in the rumen to degrade the starch and produce methane. In addition, feeding starch improves feed efficiency, with starch being digested rather completely and with lower feed requirements and less undigested material excreted. Also, diets rich in starch lead to shifts in the microbial population and rumen fermentation profile that leads to less hydrogen production and less methane emitted, and less manure.
Methane emitted from manure can increase due to an impaired fibre digestibility with high starch inclusion in the diet leading to increased faecal output that can be fermented in stored manure.
Increase maize silage may reduce overall N content of diet and thus the amount of N in excreta and subsequent nitrous oxide (N2O) emissions.
Effects on GHG emissions
Reference situation: Average starch level in the diet
Effect on total greenhouse gas (GHG) emissions
| Mean effect and range in kg CO2-equivalents | per kg product | per farm | |||
| Mean | Min-Max | Mean | Min-Max | Level of evidence | |
| Increase share of silage maize in diet | ● | o – ●● | ● | o-●● | Low |
Legend
| ● – Small effect (<5%) | o – No effect | ? – Effect unknown |
| ●● – Medium effect (5-20%) | ● – Unfavourable effect | |
| ●●● – Large effect (>20%) | ● – ● – Variable effect (depending on farm characteristics or way/level of implementation) | |
Effect per emission source
| Mean effect on absolute emission from | Animal | Manure storage | Feed and forage production | Barn | |||
| CH4 | CH4 | N2O | CO2 | N2O | LUC | CO2 | |
| Increase share of silage maize in diet | ● | ●● | ● | ? | ● | ? | |
*risk of an adverse effect (see ’cause of variable or unfavourable effect’)
Legend
| ● – Small effect (<5%) | o – No effect | ? – Effect unknown |
| ●● – Medium effect (5-20%) | ● – Unfavourable effect | |
| ●●● – Large effect (>20%) | ● – ● – Variable effect (depending on farm characteristics or way/level of implementation) | |
Cause of variable or unfavourable effect
Increase share of silage maize in diet
The effect depends on the maize silage quality (more reduction with lower NDF content), initial diet composition (e.g. grass silage), replacement rate, feed intake (a greater DM intake increases methane emissions), forage yields, and land use change (ploughing grassland for maize crops can offset the benefits of reduced methane emissions due to changes in soil carbon and nitrogen dynamics (effects not shown in this factsheet)). Methane emissions from manure can increase with a higher share of maize silage, potentially compensating the reduction of enteric methane. However, methane from manure may be captured for biogas production.
Other Effects
Effects on yield and cost-effectiveness
| Yield | Labor | Costs and revenues | ||||
|---|---|---|---|---|---|---|
| Animals | Crops | Time | Capital investment | Operational Costs | Revenues | |
| Increase share of silage maize in diet | ●–●● | o | ●-o | ●●–o | ●-o | o-●●● |
Legend (thresholds differ per indictor and can be found in the tooltip)
| ● – Small favorable effect | o – No effect | ? – Effect unknown |
| ●● – Medium favorable effect | ● – Unfavourable effect | |
| ●●● – Large favorable effect | ● – ● -Variable effect (depending on farm characteristics or way/level of implementation) | |
Effects on other sustainability aspects
| Risks of trade-offs | Potential synergies | |
|---|---|---|
| Increase share of silage maize in diet | Ammonia emission, Soil health, Biodiversity, Animal welfare, Societal and cultural acceptance | Ammonia emission, Soil health, Biodiversity, Animal welfare |
| Literature references | Increase share of silage maize in diet |
|---|---|
| Hart et al., 2015 | The influence of grass silage-to-maize silage ratio and concentrate composition on methane emissions, performance and milk composition of dairy cows |
| Hatew et al., 2015 | Effects of dietary starch content and rate of fermentation on methane production in lactating dairy cows. |
| Hellwing et al., 2014 | Enteric and manure-derived methane emissions and biogas yield of slurry from dairy cows fed grass silage or maize silage with and without supplementation of rapeseed |
| Brask-Pedersen et al., 2023 | Effect of substituting grass-clover silage with maize silage for dairy cows on nutrient digestibility, rumen metabolism, enteric methane emission and total carbon footprint |
| Borsting et al., 2022 | Effect on carbon footprint when substituting grass-clover silage with maize silage for dairy cows |
| Oenema and Oenema, 2022 | Unraveling feed and nutrient use efficiencies in grassland-based dairy farms |