Lowering protein consumption of cattle

Submitted by on Thu, 11/10/2018 - 14:47

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Summary

Aim of Measure:

Lowering crude protein content of animal diets can decrease NH3 loss.

Nitrogen Species:

Ammonia emissions (NH3)

Climatic Zone:

Semi-arid
Temperate
Tropical
Arid

Geographic Region:

Global

Sector:

Agriculture (livestock)

Sector Category:

Livestock Feeding

Measure Description

Measure overview:

Gaseous N losses from livestock production originate from the faeces (dung) and urine excreted by the livestock. The animal feed composition and the feed management has a strong influence on animal performance but also on the composition of the dung and urine, hence the emissions of NH₃.

Low-protein animal feeding is one of the most cost-effective and strategic ways of reducing NH₃ emissions. For each per cent (absolute value) decrease in protein content of the animal feed, NH₃ emissions from animal housing, manure storage and the application of animal manure to land are decreased by 5%–15%, depending also on the pH of the urine and dung. Low-protein animal feeding also decreases N₂O emissions, and increases the efficiency of N use in animal production.

Low-protein animal feeding is most applicable to housed animals and less for grassland-based systems with grazing animals, because grass is in an early physiological growth stage and thus high in degradable protein, and grassland with leguminous species (e.g., clover and lucerne) have a relatively high protein content. While there are strategies to lower the protein content in herbage (balanced N fertilization, grazing/harvesting the grassland at later physiological growth stage, etc.), as well as in the ration of grassland-based systems (supplemental feeding with low-protein feeds), these strategies are not always fully applicable.

Although in many parts of the world, cattle production is predominantly grassland-based or partly grassland-based. In such systems, protein-rich grass and grass products form a significant proportion of the diet given the high crude protein content of grass from managed grasslands. Grass-based diets often contain a surplus of protein and the magnitude of the resulting high N excretion strongly depends on the proportions of grass, grass silage and hay in the ration and the protein content of these feeds.

However, urine excreted by grazing animals typically infiltrates into the soil before substantial NH3 emissions can occur and overall NH3 emissions per animal are therefore less for grazing animals than for those housed where the excreta is collected, stored and applied to land.

How to implement the measure:

Lowering crude protein of ruminant diets is an effective and category 1 strategy for decreasing NH₃ loss. The following guidelines hold:

Dairy Cattle

The average crude protein content of diets for dairy cattle should not exceed 15%-16% in the dry matter.

The average crude protein content of diets for dairy cattle should not exceed 15%–16% in the dry matter (Broderick, 2003; Swensson, 2003). For beef cattle older than 6 months this could be further reduced to 12%;
Phase feeding can be applied in such a way that the crude protein content of dairy diets is gradually decreased from 16% of DM just before parturition and in early lactation to below 14% in late lactation and the main part of the dry period;

Beef Cattle

Phase feeding can also be applied in beef cattle in such a way that the crude protein content of the diets is gradually decreased from 16% to 12% over time.

Phase feeding can be implemented to more closely match an animal's nutrient requirements at the stage it is in its life to optimise crude protein consumption. Phase feeding is a term used to describe the feeding of several diets for a relatively short period. Through phase feeding the animal’s nutrient requirements are closely matched to its growth needs, this can minimize the over- and under-feeding of nutrients. To get maximum benefit from phase feeding, diets and feed budgets must be established for each stage of production, and established based on actual animal performance and profitability/performance goals.

Indicative target levels for crude protein content (% of the dry mass of the ration), and resulting NUE of cattle product in mass fractions (kg/kg)

Cattle species	crude protein (%)^a	NUE of cattle product (kg/kg)
Milk + maintenance, early lactation	15–16	0.30
Milk + maintenance, late lactation	12–14	0.25
Non-lactating (dry) dairy cows	13–15	0.10
Veal	17–19	0.45
Cattle < 3 months	15–16	0.30
Cattle 3–18 months	13–15	0.15
Cattle > 18 months	12	0.05

^a The values presented here can be considered as “high ambition level”.

Crude protein content in grass-based diets

Grass-based diets often contain a surplus of protein, therefore N excretion strongly depends on the proportions of grass, grass silage and hay in the ration and the protein content of these feeds. The protein surplus and the resulting N excretion and NH3 losses will be highest for grass (or grass-legume)-only summer rations with grazing of young, intensively fertilzed grass or grass legume mixtures.

fresh grass in the grazing stage (2000-2500 kg DM/ha) is 18%-20% (or even higher, especially when legumes are present),
grass silage is 16% and 18%
hay is between 12% and 15%.
maize silage is 7%-8%.

Reduction in NH3 emissions can be achieved by increasing the proportion of the year the cattle spend grazing outdoors, but this will depend on the baseline (emission of ungrazed animals), the time the animals are grazed, and the N fertilizer level of the pasture. The potential to increase grazing is often limited by soil type, topography, farm size and structure (distances), climatic conditions, etc. The actual abatement potential will depend on the base situation of each animal sector in each country.

Co-benefits and trade offs:

Cost Effective: Low-protein animal feeding is one of the most cost-effective and strategic ways of reducing NH3 emissions.

Animal Welfare: As long as the requirements for all amino acids are met, there are no animal health and animal welfare implications of implementing this measure.

Challenges:

Complexity of phase feeding: The disadvantages of moving from one feed to a phase feeding system includes greater complexity in ordering feed and the potential need to install additional feed bins on the farm. However, with increased pressures on profitability, these disadvantages must be weighed against the benefits of improved animal performance and profitability.

Pollution swapping considerations: It should be noted that grazing of animals may increase other forms of N emissions (e.g., nitrate-N leaching and N2O emissions). However, given the clear and well quantified effect on NH3 emissions, increasing the period that animals are grazing all day can be considered as a category 1 strategy to reduce emissions.

Measure Efficiency

Indicator for the efficiency of the measure:


Nitrogen Species	Ammonia(NH3)	Ammonium Nitrate (NH4NO3)	Nitrogen Dioxide (NO2)	Nitrous Oxide (N2O)	NOx	Nr	Total N
% of Reduction	5-15%	-	-	-	-	-	-

Reference system:

The abatement strategies described are not defined and assessed against a uniform reference (or unabated or baseline) feeding strategy, because these reference feeding strategies are different for different countries and between animals.

Finanacial Implications

Financial Implications table definitions:


Cost savings and production benefits ($)	Capital costs of implementing this measure ($)	Operational costs of implementing this measure ($)
-2 euros to +2 euros per kilogram of NH3-N saved (in UNECE countries).	-2 euros to +2 euros per kilogram of NH3-N saved (in UNECE countries).	-2 euros to +2 euros per kilogram of NH3-N saved (in UNECE countries).

Refs and Further Info

References:

Bittman, S. Dedina, M. Howard, C.M. Oenema, O. Sutton, M.A. (eds) (2014) Options for Ammonia Mitigation Guidance from the UNECE Task Force on Reactive Nitrogen. Centre of Ecology and Hydrology, Edinburgh, UK.

Swensson, C. (2003). Relationship between content of crude protein in rations for dairy cows, N in urine and ammonia release. Livestock Production Science, vol. 84, No. 2 (December), pp. 125–133.

Broderick, G. A. (2003). Effects of Varying Dietary Protein and Energy Levels on the Production of Lactating Dairy Cows. Journal of Dairy Science, vol. 86, pp. 1370–1381.