Scientifically Speaking …
By Matthew Wedzerai
Matthew Wedzerai holds an MSc in Animal Science (Specialisation: Animal nutrition) from Wageningen University, The Netherlands. He also holds a Diploma in Pig husbandry & Animal Feed, PTC+ College, The Netherlands. He has 7 years’ experience in the pig husbandry and animal feed industry and has been a writer of articles based on scientific research since 2014.
HOW VALUABLE IS FISH SILAGE AS A PROTEIN SOURCE IN DIFFERENT ANIMAL SPECIES?
Protein is one of the most important nutrients in feed production, yet the most expensive. Sustainable sources can be a solution to the ever-increasing demand in alternative protein sources. By-catch fish and fish waste like heads and offals are usually discarded, resulting in pollution to the environment. There is, however, potential to use fish waste as a feedstuff in the form of silage. It is cheap and simple – but what is its nutritional value in different animal species?
The ever-increasing consumption of animal products demands enormous resources; there is a risk of animal feed resources becoming scarce due to the ongoing climatic changes, and food-feed- fuel competition. The future availability of conventional protein sources such as soybean meal and fishmeal, might be limited. This pushes the feed industry to shift its attention towards possible alternatives. A potential source of protein, fish silage – is easy to make, economical, and reduces environmental problems of dumping. It has a considerably high nutritional value in pig diets.
Silage material preparation It is advisable to start with fresh raw materials for the silage to reduce high bacterial contents which might result in poor quality silage. It is also a good idea to chill the fish and fish waste products before transportation from the processing plants or vessels to the fish silage production plant, or even better, process the silage at sea. However, the bacteria are most unlikely to be a problem especially with the acid ensilage method. Which are the main methods used for the production of fish silage?
Acid ensilage method Acid fish silage is made from by-catch or fish wastes, which are preferably chopped or ground, placed in non-metallic vats (tanks or tubs which hold liquids), mixed with an acid solution and stirred several times
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daily for three to five days. The acid lowers pH and prevents bacterial putrefaction, which allows the silage to be stored for a longer period. Propionic and formic acids, and mineral acids, such as sulphuric or hydrochloric acids can be used. This method mainly inhibits bacterial growth, prevent spoilage, and speeds up the breakdown of tissue proteins.
Fermentation method The method is similar to acid ensilage; in this method, preservation is the result of acidity arising from the growth of lactic acid-producing bacteria. Following chopping of the by-catch or fish wastes, the products are mixed with a carbohydrate source in non-metallic vats, and mixed with a carbohydrate source before storing in airtight conditions. Lactic acid bacteria ensures proper fermentation and reduced spoilage. For both methods the following applies: to prevent oxidation
and rancidity, an antioxidant may be added at the time of ensiling; ethoxyquin or butylated hydroxytoluene (BHT) at 150-200 ppm are commonly used as antioxidants.
Some advantages of fish silage
Versatile feedstuff It can be used as a protein source for pigs, cattle, sheep, fur- bearing animals and fish. However, it is most useful in the diets of monogastrics.
Reduce environmental problems of dumping It makes use of materials which could otherwise cause environmental pollution; helps curb the effects of traditional offshore dumping methods.
Economical ingredient A fish silage production unit can be sized according to the supply of raw materials. Where the supply of fish for fishmeal production is low or too expensive, fish silage could be an economical substitute.
Easy to make Only three basic steps involved: grinding, acidifying and storing – no matter how big or small an operation may be.
Long term storage It can be stored for extended periods of time without becoming spoiled or rancid. The presence of mineral or organic acids or the lactic fermentation process decreases the pH, creating an environment which inhibits the growth of bacteria, and hence enables long-term storage of the raw material. Addition of antioxidants also increases storage time by preventing oxidation and rancidity.
Nutritional value of fish silage
1. Broilers The inclusion of fish silage: soybean mixture (FSSM) on diets does not adversely affect the productive parameters, carcass yield and sensory quality of the meat (Ramirez et al., 2016). The feed conversion was better with the inclusion of fish silage (Table 1).
Comment section is sponsored by Compound Feed Engineering Ltd
www.cfegroup.com
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