Fish by-products have been used in livestock production systems internationally for centuries. Typically these products have high content of valuable protein, and oils rich in polyunsaturated and omega-3 fats. While these components are of considerable value as energy and protein sources, they have also been the subject of much research both here in New Zealand and internationally on their specific effects on ruminant health and production. These include the effect of fish proteins in improved immune responses to internal parasites, the increase in the proportion of polyunsaturated fats in milk and meat products and a characteristic reduction in methane production when fish oils are included in the diet. In addition, the ready availability of fish by-products enabled their use in boosting protein in the diets of young stock in those seasonal ‘windows’ where feed quality is lower, such as summer.
However, traditional methods of processing fish by-products for use in livestock involved extensive drying to produce fishmeal, and the large energy inputs required resulted in an expensive final product, which has typically limited their use. Based on the international studies, United Fisheries Ltd, Christchurch has developed a product called Fish Silage which is enzymatically hydrolyzed fish protein at low temperature from the offal after fish processing. This retains the proteins, fish oil, amino acids, naturally occurring vitamins and enzymes. It contains approximately 7.5% fish oil and fish bone.
Based on the trials conducted by Jim Gibbs at Lincoln University shows that:
- A reduction of peak rumen methanogenesis in the daily feeding cycle of more than 33%.
- A reduction of feacal egg counts of internal parasites of ruminants in more than 50%.
- An increase in omega fatty acid content in milk, almost ten fold in certain groups, in dairy cows.