Inert fibres as an alternative to zinc oxide in pig diets

One of the alternatives to using zinc oxide in post-weaning diets is the addition of inert fibres, which can improve gut health. This page describes what they are, how they work and what impacts they can have on pigs. 

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What are inert fibres? 

The inert fibres described here are all types of oligosaccharide (long chains of carbohydrates) that are not easily digested by pigs. They help build levels of ‘friendly’ bacteria and stimulate gut development. Inert fibres have no direct energy value for pigs and can be added to a diet as a bulking agent without affecting the balance of nutrients. They are often described as prebiotics, as they benefit the gut bacteria, rather than probiotics which are the bacteria themselves. 

Depending on their source, inert fibres are often abbreviated to GOS, MOS or XOS. 

Full name Abbreviation Source material
Galacto-oligosaccharides GOS Lactose- (milk) based long-chain fibres, a by-product of the dairy industry.
Mannan-oligosaccharides MOS Yeast-based long-chain fibres, a by-product of brewing and fermentation industry.
Xylo-oligosaccharides  XOS/FOS  Plant-based long-chain fibres, a by-product of food and plant oil production.

Each type of fibre works in the same way, with the convenience of source and availability being a deciding factor in their use.  

Find out about other inert fibres used within livestock diets

How do inert fibres work? 

Inert fibres are food for specific types of bacteria. Increasing that food supply means that the numbers of ‘friendly’ or ‘good’ bacteria in the gut increase. This limits the population of unfriendly or disease-causing bacteria because the good bacteria release chemicals that limit their growth or outcompete them.  

Fewer disease-causing bacteria results in less diarrhoea and other health pressures in post-weaned pigs. 

The presence of the good bacteria and the chemicals they release help stimulate the physical development of the small and large intestines. This development of a strong, well-formed gut means that piglets can better make the transition from milk to solid feed and experience a significantly reduced dip in post-weaning performance, i.e. pigs with a healthy gut cope better with the transition of weaning.  

There is evidence to suggest that the addition of specific inert fibres can positively impact the immune response of the gut. This better prepares pigs to deal with disease-causing microbes.  

Azad et al. (2020) produced an overview of prebiotics, source and impact. You can find this report in The journal of Animal Nutrition, and the article is entitled Opportunities of prebiotics for the intestinal health of monogastric animals 

What should I consider when including dietary fibres in pig diets? 

Inert fibres are at their maximum effectiveness in pig herds with low levels of endemic disease and good levels of biosecurity.  

Piglets with good access to colostrum are more likely to develop a healthy gut and immune system. The addition of inert fibres to diets should be made in conjunction with very well controlled biosecurity and a clear health management plan. 

Find out more about colostrum management for pigs

How to improve biosecurity on your farm

Depending on which fibres are used and at which stages in growth, e.g. from birth or pre- and into post-weaning, the use of inert fibres can have different outcomes. It is always advisable to discuss with your vet and nutritionist which solutions are likely to have the biggest impact on your system.