THE GROWTH OF PIGS FROM 6 TO 10 KG WHEN FED FISH SILAGES THAT WERE PRESERVED EITHER BY FORMIC-ACID OR BY FERMENTATION

Formic acid preserves fish for use as an animal feed. Another process of fish preservation mixes fish with barley and a lactic acid fermenta tion is begun that lowers the pH. This study compared the nutritional value of this naturally fermented fish silage (355 g kg-1 of protein i n the dry matter (DM)) with formic acid silage (558 g kg-1 protein). T he formic acid silage was prepared by mixing ground fish from the same batch with 76 mol (100 kg)-1 of formic acid. Pigs weighing 6 kg were given one of ten diets in wet form (3 5% DM) until they reached 10 kg. Thirty pens each containing eight pigs were used in the experiment. D iets were produced that contained 0%, 6%, 8%, 10% or 12% DM of acid fi sh silage or the same levels of fish from naturally fermented silage. All diets contained 15.6 MJ of DE kg-1 DM and 220 g protein kg-1 DM. T he fish silage replaced a mixture of soyabean and fish meal in the die t. The feed intakes of the pigs given the naturally fermented silage w ere 12% greater (P < 0.01) than those given the acid silage. This may have been due to the naturally fermented silage having a lower than ex pected digestible energy content. Each 1% addition of fish from both s ilages decreased (P < 0.001) pig growth by 4%. Feed intakes were decre ased by 3% for each 1% increase in fish silage above 6% of the diet. P oor flavour characteristics of the fish silage, owing to lipid oxidati on and protein hydrolysis, probably reduced the voluntary feed intakes of the pigs and resulted in poorer productive performance.