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There is a pre-conceptualised idea that the higher is the protein content of a feed the faster the animal will grow, especially for piglets. Such rationale leads farmers to select higher protein to boost their animal growth. But actually, high protein content can create some damages as well. Morever, dietary protein is the next most expensive cost in the diet after energy and we should avoid wasting it.

An immature enzymatic system:

Before weaning, the piglet is easily able to digest the high protein level of the sow milk, but after weaning, moving to a solid and vegetable-based diet it will face a more difficult challenge. The weaned piglet before 6-7 weeks of age has an immature enzymatic system: Lipolytic and proteolytic enzymes synthesis has not reached full efficiency and plant protein will be allergenic and poorly digestible.

Consequently, the crude protein will be incompletely digestible and this indigestible fraction entering the hindgut will cause proteolytic fermentations and pathogenic bacteria development resulting in diarrhoea, growth retardation and even mortality.

Less diarrhoea with lower protein content diets

In many countries where the antibiotics are still used as growth promoter, the fermentation triggered by the non-digested protein will be controlled by the antibiotics. But when we are reducing the use of antibiotics or when resistance appears, diarrhoea will occur. This diarrhoea is not always associated with bacterial contamination, as we often believe but the results of the fermentation of the non-digested portion of protein.

This has been one of the first major challenges that producers had to solve in Europe when antibiotics have been forbidden at growth promoter concentrations. Without the use of antibiotics, farmers had to reduce the protein level in piglet diets in order to avoid releasing non-digested protein into the gut.

Minimum protein requirements for weaned piglets feed:

Surprisingly, it showed that such adaptation did not affect weight gain, feed intake and feed efficiency of the animals. Many studies, and a long practice of feeding in Europe, showed that reduction of protein content in feed has been beneficial to the industry by reducing the digestive disorders and prepare better the piglets for a high daily growth and a better feed efficiency.

This shows that the high levels of protein that we supply to piglets in Asia are actually not well converted by the animals. It would be better to provide lower protein content provided that we can guarantee high level of digestibility.

To define the optimal level of protein in the feed, we must look at Lysine first. As far as energy is not limiting in the diet, lysine is the first limiting amino acids for the piglet growth, the response to growth is proportional to the lysine intake. Increasing lysine which digestibility is very high (around 87% from protein sources and 100% from synthetic lysine) will directly improve the daily weight gain without any adverse effect on health.

The other amino acid should be supplied with the correct ratio to Lysine to avoid any excess that would then be fermented and cause diarrhoeas. This ideal amino acid profile is now well known and the

The importance of amino-acids according to tissues

So, in the minds of most nutritionists and veterinarians, cutting back on crude protein is a sure way to control diarrhea, even when antibiotics are used. But, that’s not true in several places around the globe. Let’s talk about Asia, China in particular. There, and despite the fact that nutritionists and veterinarians recognize the need to reduce crude protein, such measure is virtually impossible for marketing purposes and sometimes even regulatory purposes. A low-crude protein feed is considered inferior even though assurances are provided that amino acids are there — so as to protect animal growth. I believe this is a matter of customer education. The same but different is true for the U.S. market that has started the uphill battle against growth-promoting antibiotics. There, nutritionists cannot fathom a piglet diet with only 18 percent crude protein when their existing products contain as much as 24 percent crude protein. Clearly this is a matter of scientific development, and I know they are working hard to this end.

But, let’s consider the existing situation: two large pig markets — the U.S. and Asia — that cannot accept, yet, lower-crude protein diets for piglets (with or without antibiotics). Is there anything that can be done to ensure that piglets don’t scour and continue to grow when high-protein diets are fed without antibiotics (U.S.) or when antibiotics are facing resistance (Asia)?

In countries who are enforcing limitations in nitrogen emissions, the reduction of protein content in diet by increasing the protein digestibility is an obligation. The drop of 1 percentage point of crude protein in the diet get the emissions of NH3 by 10%.

This strategy of reducing protein content must start with the selection of the protein sources with a specific focus on digestibility. It is not only a question of cost. We must leave as little as possible undigested protein in the gut even at a superior cost.

  • From animal by products: Milk, Whey protein concentrate, Fish meal, plasma protein…

  • From plants: Protein concentrate, Extruded SBM, potato protein…

We must pay an attention as well not to antagonise the digestive process. Protein sources have a high Acid Binding Capacity (ABC), limiting the natural acidification of the stomach. The natural pH evolution of the stomach moves from 4.5 at weaning to 2.8 during the growing phase. This pH evolution is necessary to improve the initial process of plant protein digestibility. To counterbalance the negative effect that protein will have on the pH, it is advised to choose a high level of strong acidifiers (up to 8-10kg per ton), with a high negative ABC (Formique, fumaric, orthophosphoric acids) and to limit incorporation of other elements that could increase feed ABC value due to their buffering activity

  • Limit calcium carbonate (by using more digestible source of Calcium)

  • Reduce the dosage of Zinc Oxide from 3000ppm to 300ppm

  • Add dietary protease to reduce the undigested portion of protein and limit proteolytic fermentation

Other tools to limit the fermentation of non-digested protein will be to incorporate in the feed a portion of micronized fibers. The gut bacteria will preferentially ferment fiber source vs. the protein thereby limiting the negative effects of the higher protein. So, where feed producers do need to market high protein diets, use of the micronized concentrated source fibers is a key formulation strategy to balance their diet.


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