The growth of pigs from 6 to 10 kg when fed fish silages that were preserved either by formic acid or by fermentation

Abstract

Formic acid preserves fish for use as an animal feed. Another process of fish preservation mixes fish with barley and a lactic acid fermentation is begun that lowers the pH. This study compared the nutritional value of this naturally fermented fish silage (355 g kg −1 of protein in the dry matter (DM)) with formic acid silage (558 g kg −1 protein). The 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 (35% DM) until they reached 10 kg. Thirty pens each containing eight pigs were used in the experiment. Diets were produced that contained 0%, 6%, 8%, 10% or 12% DM of acid fish 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. The fish silage replaced a mixture of soyabean and fish meal in the diet. The feed intakes of the pigs given the naturally fermented silage were 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 expected digestible energy content. Each 1% addition of fish from both silages decreased ( P < 0.001) pig growth by 4%. Feed intakes were decreased by 3% for each 1% increase in fish silage above 6% of the diet. Poor flavour characteristics of the fish silage, owing to lipid oxidation and protein hydrolysis, probably reduced the voluntary feed intakes of the pigs and resulted in poorer productive performance.