Microbiological feed hygiene essential for 
modern farming

By Sarah Pesie, technical communication manager, Selko Feed Additives

Livestock producers have a 
challenging business dealing with an increasing pressure on the feed market and a growing concern for 
sustainable production. The supplies are scarce and the global population is expected to increase from seven billion today to nine billion in 2050, of which three billion people will newly reach the middle class. Consequently more people can afford purchasing, and demand high quality nutrition such as animal proteins. In contrast there are still over one billion people suffering from malnutrition.

The livestock industry has a shared responsibility to use sustainable and affordable nutritional solutions, aiming to produce enough animal proteins to satisfy increasing demands. An interesting opportunity is to increase the efficiency of the feed to food cycle. Yearly one third of all food production is left unused because of losses in 
processing and waste (FAO 2011). Globally this is more than one billion tonnes of food spoiled each year. Inedible or unmarketable products can be converted into animal feeds, reducing nutrient spoilage. The effectiveness of using organic acids for the preservation of animal feeds and co-products from the food industry becomes better researched and confirmed. Recently a research was done by an MSc student of Wageningen University, which results are elaborated in this article. Protection against spoilage due to microbiological contamination has shown to be essential for sustainable use of moisture feeds such as co-products, some silages and Total Mixed Ration (TMR).

Hygiene matters in liquid pig feeds

The usage of co-products from the food industry is generally accepted for livestock feeding. Due to the increasing scarcity of natural resources compared to the large amounts of co-products available the economic benefits of using co-products increases. For example potato peelings, brewer’s yeast, bread blend, whey can be used as an ingredient for liquid pig feed. To preserve 
co-products, natural acidic fermentation is encouraged. This causes the pH to lower and limits the growth of micro-organisms such as yeasts. The fermentation process depends on environmental factors such as hygiene, atmosphere, temperature and content of the feed.

In itself, yeasts can be a good addition to the feed for animals. However yeast development in a co-product makes it difficult to predict the quality and nutrient content. Growing yeasts are not desirable as they consume sugars and essential amino acids such as lysine, quickly bringing down the nutrient values to alarming levels. The dry matter content decreases and the water, pH level and CO₂ content of the feed increases. The degradation of the feed due to yeasts lowers the palatability, decreasing feed uptake and animal performance. Additionally the toxins from moulds, and gasses produced by yeasts inside the intestines when being eaten can cause serious health issues for swine. In combination with high levels of Enterobacteria (i.e. Salmonella and E-coli) this may cause food safety risks and increased mortality.

In contrast to mould and Enterobacteria, yeasts are not included in the GMP+ quality controls or regulation. However it is strongly recommended to perform yeast controls and to implement a hygiene strategy to limit the detrimental effects of yeast. In a low risk feeding strategy hygiene control is number one priority. This includes regular cleaning and disinfection of the troughs and feeding system. Negative effects from yeasts are limited when keeping a maximum yeast count rule of 100,000 CFU/gram (colony forming units) in co-products.Figure 1 presents an overview of microanalysis of 892 samples of co-products received last year in the Selko laboratory. The yeast count is too high in more than half of the samples (39.4 % ≤100,000 CFU/gram). This clearly indicates that prevention of yeast contamination is highly desirable and will pay back due to less feed spoilage when yeast is controlled. Research proves that not only the feed content is better preserved but also that feeding liquid feeds with a low pH limits harmful Enterobacteria along the gastrointestinal tract in sows and piglets.

Ruminants prefer organic acids in feed

Yeast problems do not only occur in liquid feeding with co-products in pigs. Also co-products and silages used for ruminant feeding in TMR can be affected by microbiological contamination. Silage is a fermented feedstuff, mainly used as winter forage for ruminants in north USA and Europe. Ensilaging is done to preserve crops with high moisture content. The limited air contact prevent yeast development in the silage. Yeast development consumes the nutrients and results in dry matter losses. The yeasts produce CO₂ and warmth while lowers the palatability. In ruminants this results in a low feeding efficiency, lower milk yield and more indirectly related health problems such as lameness and mastitis.

Fortunately, the problems caused due to yeast contamination can be prevented with correct microbiological hygiene and preservation of the feed. When the silage is mixed in TMR an organic acid blend can control the activity of yeast in feed.Figure 2 illustrates three graphs that indicate the positive effects by the preservation of TMR with organic acids. Direct effects can be seen in a higher dry matter intake per dairy cow per day. An experiment done by a MSc student A. de Brouwer from Wageningen University showed that at five dairy farms organic acids effectively stop yeast development when TMR was added during mixing. The yeast counts reduced with 17.6% compared to similar, untreated, control feed. However the yeasts already present in the feed did not disappear. Another benefit of using organic acids is that Enterobacteria cannot resist the acidic environment and die, resulting in 52% decrease of Enterobacteria count. Additionally the organic acids improve the palatability of the feed, which results in a higher dry matter intake by the cows. Farmers participating in the experiment were convinced to keep using organic acids, especially when the weather enhanced yeast development i.e. warm or humid. The higher feed intake can result in positive effects on milk production and vitality of the cows on the long term. The duration of the experiment was however too short to show the benefit of organic acids significantly.

Everybody benefits

To optimise feed utilisation, good hygiene practices are essential. Organic acids are an ecologically sound solution for feed preservation. The usage is safe for humans and 
animals and results in a more efficient use of resources. Specialised synergistic blends of acids make sustainable feeding more available and easy to implement. The unique characteristics of the various acids in a synergetic blend make the product more efficient. A broad protection against yeasts, moulds and Enterobacteria can improve the following aspects:

– Feeding efficiency increases; 
a better palatability, results in 
optimal health and growth.

– Feed safety is enhanced; Enterobacteria both in the feed and inside the animal are limited.

– Shelf life of co-products and TMR is prolonged; ensuring a stable nutrient composition.

Microbiological hygiene shows to be 
an essential step towards a more 
sustainable and efficient feed to food production cycle. It combines the 
interests of the farmer, food industry and society in a positive manner.

References are available on request.

For more information about feed hygiene, please contact Maarten van der Heijden Business Manager Health & Preservation, Selko Feed Additives (Maarten.van.der.Heijden@nutreco.com)