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Feed for piglets: towards an optimum amino acid content

INRA scientists, working in collaboration with the company Ajinomoto Eurolysine s.a.s., have demonstrated the importance of valine in low-protein feeds for piglets.  This work will enable the optimisation of nutritional strategies to develop cereal-based diets and to reduce nitrogen emissions by pig rearing units.

Piglets at the Bourges Galle experimental unit in Avord. © INRA, CATTIAU Gilles
Updated on 08/29/2013
Published on 08/29/2013

The environment, economics and animal health: triple demands to reduce the nitrogen content in piglet feeds

To enable the very rapid growth of piglets, the diet of these young animals must meet their considerable needs for amino acids to enable the synthesis and deposit of proteins in the body.  In view of the limited ingestive capacity of piglets, covering their amino acid needs has for many years been achieved by ensuring a massive intake of proteins; for example, in the form of soybean or fish meals.  However, this strategy has been called into question for several reasons.  The first is the onset of digestive disorders as a result of bacterial proliferation and the fermentation of undigested proteins in the gut.  Lowering the protein content can thus contribute to reducing the use of antibiotics in livestock units.  The second is the need to reduce nitrogen emissions by piglet excreta resulting from the degradation of amino acids that have not been utilised by the animal.  The third and final reason is the rise in the cost of raw materials.  Lowering the protein content of feeds has thus become imperative, but under the constraint of not penalising animal growth; it is therefore necessary to establish the levels of intake for each amino acid in a feed that are essential to maximise growth (nutritional requirements).

Knowledge based on nutritional requirements

For several years now, more detailed knowledge has been obtained regarding the amino acid requirements essential to ensure a maximum growth rate for piglets.  The addition of lysine, threonine, methionine and tryptophane in a crystallised form to low-protein diets can meet the amino acid needs of an animal and enhance its utilisation of nitrogen.  Further opportunities for progress are possible, but are hampered by a lack of knowledge on the physiological roles of amino acids and their required levels.
In the context of a CIFRE contract thesis project set up between the Joint Research Unit for the Physiology, Environment and Genetics of Animals and Livestock Systems (PEGASE) and AJINOMOTO EUROLYSINE S.A.S., the researchers focused on amino acids that limit piglet growth and those whose intake must be precisely controlled – once needs for tryptophane, methionine, threonine and lysine have been met – in order to ensure adequate coverage of the animal's requirements.  During this work, the scientists were particularly interested in branched-chain amino acids (valine, leucine, isoleucine).  It is indeed known that valine is the fifth amino acid that limits piglet growth, and because branched-chain amino acids utilise the same enzymatic pathway during their catabolism, an intake of these specific amino acids may degrade the others.

The role of branched-chain amino acids in the diet

The researchers confirmed the levels required of certain branched-chain amino acids (leucine/lysine and valine/lysine ratios, expressed in terms of standardised ileal digestibility, SID) that are presented in nutritional tables (NRC 1998 and BSAS 2003), but they reported lower isoleucine/lysine (SID) needs.  Valine deficiency caused a reduction in the weight gain of piglets, while excess leucine aggravated the effects of a valine deficiency.  A minimum 70% valine/leucine ratio is necessary to prevent the negative effects of excess leucine.
The researchers were thus able to determine that with an adequate intake of branched-chain amino acids in a cereal-soybean meal-based diet in piglets, the content in total nitrogen (proteins and amino acids) could be reduced from 19% to 16% without affecting the growth performance of animals, which is equivalent to a 40% reduction in nitrogen emissions.  

Scientific contact(s):

  • Nathalie Le Floc’h (+33(0)2 23 48 50 39) Joint Research Unit for the Physiology, environment and Genetics of Animals and Livestock Systems (PEGASE)
  • Jaap van Milgen (+33(0)2 23 48 56 44) Joint Research Unit for the Physiology, environment and Genetics of Animals and Livestock Systems (PEGASE)
Associated Division(s):
Animal Physiology and Livestock Systems
Associated Centre(s):

Find out more

  • Gloaguen M., Le Floc'h N., Brossard L., Barea R., Primot Y., Corrent E., van Milgen J. (2011). Response of piglets to the valine content in diet in combination with the supply of other branched-chain amino acids. Animal 5, 1734-1742.
  • Gloaguen M, Le Floc'h N, Corrent E, Primot Y, van Milgen J, 2012. Providing a diet deficient in valine but with excess leucine results in a rapid decrease in feed intake and modifies the postprandial plasma amino acid and α-keto acid concentrations in pigs. Journal of Animal Science 90: 3135-3142.
  • Gloaguen M, Le Floc'h N, Primot Y, Corrent E, van Milgen J, (in press). Response of piglets to the standardized ileal digestible isoleucine, histidine and leucine supply in cereal-soybean meal-based diets. Animal (doi:10.1017/S1751731112002339)