Health conditions and
practical consequences

Figure 1. The detrimental effect of health deterioration on growth is mediated through a decrease in feed intake and the diversion of nutrients from muscles towards immune functions

Permanent exposure of animals to infectious or non infectious antigens prevents animals from expressing their growth potential. When animals are exposed to high antigen pressure, growth and feed intake are depressed even if there are not serious clinical signs of disease. Hence, nutrients are diverted away from growth towards the tissues and cells involved in immune functions (Figure 1).

In such a situation, amino acids can be used as an energy source for gluconeogenesis, immune cell proliferation and serve as building blocks for inflammatory protein and immunoglobulin synthesis. Finally, amino acids can enter specific metabolic pathways related to body defence. By understanding the interactions between nutrition and health, nutritionists and producers can design feeding strategies to maximise productivity while minimising the negative impact of unfavourable environments on growth performance.

Antimicrobial growth promoters (AGP) have been banned from the feed in 2006 in the EU. AGP act mainly on the activity of intestinal bacteria by limiting the development of unfavourable bacteria. As a consequence, they avoid digestive disorders and increase the availability of nutrients and energy for growth. Thus AGP removal from the feed may lead to a decrease in growth and an increase of health damage (Figure 2).

Figure 2. The effect of antimicrobial growth promoters (AGP) withdrawal from the diet on animal growth performance

As amino acids are closely related to growth performance, and for some of them to the integrity of gut health (e.g. threonine) and to the immune system (e.g. threonine and tryptophan), AGP withdrawals could lead to higher amino acids requirements. Amino acids could indeed be used in greater amount to satisfy potentially higher uptake by intestinal flora due to bad environment and/or to cover higher usage for proteins involved in immune function. Finally, amino acids requirements will depend not only on the level of growth performance but also on the way they are used by the body and the level of feed intake.

Despite lower growth performance when health status deteriorates, the requirement for amino acids could be modified. In growing-finishing pigs, it is shown that not only balanced lysine but also threonine requirement are higher in pigs fed a diet without salinomycin compared to pigs fed with 30 ppm of salinomycin. In piglets reared in poor sanitary conditions, balanced lysine and tryptophan requirements for optimal growth is not changed, however for both amino acids a deficiency will affect more severely the growth performance of the piglets with low health status compared to those with high health status.

Consequently, adequate supply of amino acids in conditions of poor health status helps to reduce the impact of a decrease in feed intake, change in nutrient utilisation and to maintain a correct level of growth.

The article below presents experiments at Schothorst Feed Research which investigated the effect of the AGP ban on the amino acids requirements.


For further information, please read our technical bulletins: numerous experimental results are reported.