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Optimal weaning with vegetable proteins

Many sources of protein seem to have disadvantages for weaned piglets or pig producers - legislation, price or anti-nutritional factors.The demand for less antibiotics and alternatives for expensive fishmeal in piglet feed and improved animal welfare force producers to take a different approach towards piglet feeding prior and post weaning. A protein source offers a helping hand.

By Lars Sangill Andersen, feed application manager, Hamlet Protein, Denmark

Proteins from a vegetable source are generally not the proteins of first choice in feed formulations for preweaning or weaning piglets. Believing vegetable proteins to be high in crude fibre and anti-nutritional factors, feed processors typically prefer alternative, more expensive proteins to meet the piglet’s amino acid needs.

This is true for soybean meal, the most used vegetable protein source. Having one of the best amino acid profiles of the vegetable proteins, it could serve as the main or even sole protein ingredient in piglet feeds. The reason why it is not is its content of anti-nutritional factors (ANF), which are a frequent cause of digestive problems, resulting in increased antibiotic use.

It is for this reason that fishmeal, milk proteins, potato protein and plasma have found a place in piglet feed formulations. However, since the banning of antibiotic growth promoters in Denmark shortly before the BSE crisis, it is no longer permitted to use animal proteins like plasma in piglet diets.

Fishmeal and milk products are, today, the only alternatives to vegetable proteins.

Trend towards fishmeal reduction
There is no doubt that fishmeal is a good protein source for optimised, healthy piglet feed. The problem is the increasingly high cost, which has encouraged some feed manufacturers to reduce or eliminate fishmeal from feed formulations. Although it is possible to formulate feed without fishmeal, the disadvantage is the increase in crude protein (CP) content.

To avoid sub-optimal diets that compromise health or performance, it is crucial to ensure that fishmeal alternatives are easily digestible. If not, piglets will suffer digestive problems resulting from a build up of excessive protein in the large intestine.

Non-protein nitrogen
A competitively priced alternative came up when L-Valine was introduced. It is a single amino acid which enables the formulation of weaning diets with only a few vegetable proteins. It created an opportunity to experiment with piglet formulations that contain no fishmeal or other animal proteins, such as plasma, and no antibiotics. Experience shows that these diets give good piglet perform ance and, often, improve gut health.

The reason for the apparent differences in performance could be found in the use of various protein sources (Table 1) since not all CP in a protein source comes from amino acids. Some are derived from other non-protein nitrogen compounds, known colloquially as NPN. In fishmeal, the content of NPN is particularly high.

NPN content of selected feedstuffs (composition in 1,000 g product). 

Anti-nutritional factors in the form of NPN and undigested protein increase the growth of unwanted bacteria in the intestine and put a strain on the animal’s liver and kidneys during their subsequent excretion.

As Table 1 suggests, the reduction or elimination of fishmeal from piglet feed could lead to improved digestive health.

Choose the right alternatives
When replacing fishmeal, it is important to choose alternatives that are not only equally digestible but can also supplement the amino acid content. The digestibility measurements shown in Table 2 highlight a big difference between soya products. The difference in digestibility reflects the content of antinutritional factors that are harmful to piglet digestion (Table 3), resulting in low daily weight gain and feed utilisation and a compromised dietary tract. It is important to ensure the content of such harmful components is as low as possible in the feed.

Standardised ileal digestibility in weaning piglets.

Analysed content of anti-nutritional factors in soya products.

The recipe for optimal performance
Researchers at the University of Illinois* proved in a ileal digestibility test that by using vegetable proteins with similar digestibility to fishmeal in combination with single amino acids, it is possible to create a diet far lower in CP and NPN than fishmeal-based feed and, at the same time, an optimised content of amino acids. They consider this the recipe for optimal piglet performance. The fats and minerals usually obtained from fishmeal are easily replaced by readily available market sources, without the need of integration in the vegetable protein.

Highly digestible soya protein.Diets based on highly digestible vegetable protein with a low content of crude protein are proven to reduce the problem of weaning diarrhoea. According to new international research, optimised piglet diets promote animal welfare and, because piglets are healthier, medication costs are reduced.

*Read more about this research “Ileal digestibility of amino acids in conventional, fermented, and enzyme-treated soybean meal and in soy protein isolate, fish meal and casein fed to weanling pigs,” by S.K. Cervantes-Pahm and H.H. Stein both researchers at the University of Illinois, published in the Journal of Animal Science. Link to the research article:

More info: Lars Sangill Andersen - lsa@ / +45 75 63 10 20