Better Balanced Food Supply (Feeding Adjustment)

Objectives By better balancing the supply of feed with the feed requirements of the animals the digestibility of the feed will increase and the quantity of manure per unit of feed and per unit of product will decrease. | Objectives Techniques Costs Targeted Livestock System Impact Context of Application References

Techniques

Refining the feeding standards for the feed requirements for the different classes of livestock and balance the supply of energy, protein (N), minerals (P and K), heavy metals with the requirements of the animals. For example, most of the nitrogen in the urine originates from an imbalance between the amount and quality of digestible protein and animal requirements. Adjusting the protein content of the feed ration can reduce the amount of N in the urine.

In intensive monogastric production systems, reduction in N losses will be mainly achieved by adjusting the protein content of the feed to the variable requirements of the animals of various age and productivity (phase-feeding) and by balancing amino acid requirements and digestible amino acids offered. For the last-mentioned option, addition of synthetic amino acids is an important and increasingly popular strategy. Many commercial compound feeds for monogastrics contain added synthetic amino acids, mainly lysine and methionine as these are often the first limiting amino acids. High costs may prevent broader application of other limiting amino acids.

In intensive ruminant production systems, balancing the intake of rumen degradable protein and rumen degradable energy can produce major effects. In most European countries this would require a substantial reduction in the quantities of grass fed, as grass with a reasonable productivity per ha, almost inevitably has a high surplus of rumen degradable protein. However, this would imply a significant shift in feeding practices and even in the whole livestock system. The input of N from grass and forages can be reduced when forages are harvested in a somewhat more mature stage of growth. The amount of N input could also be reduced by replacing part of the grass based forage by whole plant maize or whole plant grain, or feeding limited amounts of straw to dairy cows. The latter would not only limit N input but also shift N output in manure from urine to faeces, this increases the C:N ratio in the manure and could reduce the N losses through ammonia emissions.

Usually fairly large safety margins for P requirements are used, as more accurate assessment of these requirements is complicated and no problems in case of overdose are anticipated. There is a high variability in the P digestibility of feedstuffs of plant origin from 20 % in maize and rice bran to 38 % for barley and soybean meal. The content of phytate P and the content of phytase can explain part of the variability; phytate P is hardly digested, but if phytase activity is high the digestibility of P will increase. It is estimated that the digestibility of P can be increased up to 60 % via the use of phytase. Phytase is present in germinating seeds, but also in grains in rest, particularly in rye and wheat. Major efforts have been made to examine the effects of microbial phytase to pig and poultry feed to increase P digestibility and the reduction of P excretion. Phytase preparations are now available as feed additives and will enhance the intestinal availability of P.

In monogastric animals, biotechnology has a potential to improve digestibility, particularly to eliminate anti-nutritional factors (ANF), which interfere with digestion or absorption. Examples of ANF’s are: tannins, trypsin inhibitors, lectins, non-starch polysaccharides, and specific oligosaccharides.

Altering feeding rations to include ingredients with higher P digestibility (e.g. feeds of animal origin or leguminous feeds) could also reduce P excretion.

Heavy metals:

The Cu content of the feed can be reduced to a large extent, though this might require an improved level of general management to avoid declining growth performance.

Utilization of phytase might also increase the availability of Zn, thus reducing the need for additions in the feed.

The Cd content is strongly related to the addition of inorganic feed-P , though improvements can also be achieved via the utilization of less phosphate and phosphate with less Cd.

In the Netherlands the maximum Cu content in feed for piglets (up to a liveweight of 16 kg) is 175 milligrams per kg. All other feed is a maximum of 35 milligrams per kg.

Costs

Cost differ according to the solution used:

- Savings could be made by reducing levels of protein, additives and mineral mixture.
- Cost could increase if higher quality ingredients (less by-products of a variable quality) and additives (e.g. synthetic amino acids, phytase preparations) have to be used which have a more reliable and constant quality.

Targeted Livestock Systems

Primarily the industrial livestock production system

Impact

- Positive Environmental Impact

- Reduction of the quantity of manure per unit of feed and per unit of product
- Reduction of the content of heavy metals in the manure

- Negative Environmental Impact

- In certain situations this could lead to reduced use of by-products and waste products in the feed manufacturing industry and an increase in the use of high quality primary products (competing with human food)

- Livestock Productivity Impact (groups : milk, reproduction, meat, health, feed...)

- Improved conversion of feed into animal products and increased efficiency of animal production

Context of Application

- Policy:

- Stimulation and providing incentives for research.
- Legislation for maximum levels of heavy metals in feed.

- Institutions:

- Feed quality control institutions.
- Research into feed composition, digestibility and excretion.

- Education:

- Training and extension of farmers.

References

P.J. Brandjes, de Wit, J. van de Meer, H.G. and van Keulen, H. 1996. Livestock and environment finding a balance: Environmental impact of animal manure management. International Agricultural Centre, Wageningen, the Netherlands.

de Wit, J., Westra, P.T. and Nell, A.J. 1996. Livestock and the environment Finding a balance: Environmental impact assessment of landless livestock ruminant production systems. International Agricultural Centre, Wageningen, the Netherlands.

Bos J.F.F.P. and de Wit, J. 1996. Livestock and the environment Finding a balance: Environmental impact assessment of landless monogastric livestock production systems. International Agricultural Centre, Wageningen, the Netherlands.

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