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Valine & Isoleucine as a limiting amino acids in poultry diet - Animal feed and poultry
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Valine & Isoleucine

Valine & Isoleucine as a limiting amino acids in poultry diet

Valine and Isoleucine: The next limiting amino acids in broiler diets

genetic changes have occurred in many commercial broiler lines with

regard to performance. This improvement needs a corresponding adjustment of our knowledge about amino acid nutrition in broilers.

The least cost formulation of the diet according to the ideal protein concept is the best way to supply an economic and a balanced amino acids feed for broiler, which can help to reduce the nitrogen excretion during the rearing period.

 

What are the next limiting amino acids in broiler diets?

To reduce dietary crude protein levels in broiler feed, it is necessary to know which

amino acids become limiting in diets and what the requirement of broilers is. Valine, Isoleucine, Tryptophan and Arginine are generally considered as the next limiting amino acids in broiler feed. Indeed, the amino acid composition of protein differs between feedstuffs.

In a study on 8-21day-old chicks The authors used the deletion method (amino acid supply was reduced one after another) and observed average daily gain (ADG) and gain:feed ratio (G:F) of the birds,and determineded that Methionine, Lysine and Threonine were the 1st limiting amino acids for broiler performance. It can be seen that Valine was the 4th limiting amino acid for broilers.

 

The Valine requirement of broilers as a ratio to Lysine

There is a clear response in ADG and G:F ratio to increased TD Val:Lys ratios, which validates   the selection procedure. The TD Val:Lys ratio of 80% appears as a minimum to optimise broiler growth and feed efficiency.(figure 1 )

 

Figure 1: Effect of TD Val:Lys ratio on ADG and G:F

Effect of TD Val:Lys ratio on ADG and G:FThe compilation of the data for carcass parameter shows a strong effect of TD Val:Lys ratio on weight of carcass and breast meat As carcass weight and breast meat weight increased together withnincreased Val:Lys ratios, the ratio between breast meat and carcass weight did not change. However,meeting the bird’s requirement for Valine is of key importance in ensuring the optimal usage of Lysine which is well known to increase breast meat yield

The Isoleucine requirement of broilers as a ratio to Lysine

In order to estimate the TD Ile:Lys ratio that optimises ADG and G:F ratio in broilers, growth performance of the six trials were compiled using the same method as for Valine. The graphical results of this compilation are presented in figure 2.

There is a clear response in ADG and G:F ratio to increased TD Ile:Lys ratios, which validates the selection procedure. A minimum TD Ile:Lys ratio of 67 appears to be necessary to optimises broiler performance.

 

Figure 2:Effect of TD Ile:Lys ratio on ADG and G:F

Effect of TD Ile:Lys ratio on ADG and G:F

 

Practical implication for broiler diets

it is possible to progressively determine the next limiting amino acid in broiler feed, and to establish the extent to which it is possible to reduce dietary crude protein through supplementation with amino acids As an example, three grower broiler diets (14 – 28 days) were formulated.

The first simulations are based on wheat-soybean meal diet and the second ones on corn-wheat-soybean meal diet (figure 3).

In both simulations, sulphur amino acids, Lysine and Threonine were the first limiting amino acids. L-Threonine supplementation allowed an additional reduction of approximately one percentage point of CP in both diet types.

Then, in these vegetable diets, Valine was the next limiting amino acid before Arginine

and Isoleucine. The supplementation of L-Valine allowed a further reduction of one percentage point of dietary CP.

In contrast, Isoleucine at 67% TD Ile:Lys ratio is the next limiting amino acid after Threonine in feed containing blood meal, followed by Arginine and Valine (figure 4).

 

Figure 3:

 

sulphur amino acids, Lysine and Threonine were the first limiting amino acidsFigure 4:

 

 

Conclusions

  1. Valine is the 4th limiting amino acid in vegetable broiler diets based on wheat or corn
  2. Isoleucine becomes the 4th limiting amino acid, when blood cells or blood meal are used in formulations.
  3. The TD Val:Lys and TD Ile:Lys requirements of broilers are 80% and 67%, respectively, to optimise

performance.

  1. Knowing the requirements of individual amino acids, feed formulators have more flexibility to reduce

dietary crude protein levels.

  1. L-Valine supplementation in combination with L-Threonine provides the opportunity to formulate

technically, economically and environmentally better broiler feed.

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