Herborg Haaland

Autolysed fish silage as a feed ingredient for atlantic salmon (Salmo Salar)

Abstract 1. 1. Fish silage made from saithe stored for 2 and 5 months was compared to raw minced saithe as a replacement for parts of the dietary feed protein for Atlantic salmon (Salmo salar). 2. 2. Weight gain and feed utilization were better in the fish fed the silage stored for 2 months and the raw mince than fish fed the silage stored for 5 months. These fish also showed somewhat better protein utilization. 3. 3. Those fish fed the most hydrolysed feed nitrogen, stored less fat in carcass and fillets, resulting in higher amounts of protein.

Growth of young rats on diets based on fish silage with different degrees of hydrolysis

Abstract The effect of storage for up to 1 year on the nutritional value of ensiled cooked and non-cooked minced capelin was determined in growth experiments with young rats. Minced fresh capelin of the same batch was also included. Cooked silage came out best after the storage of 1 year showing both better growth and protein efficiency ratio (PER). There were no significant differences in apparent digestibilities. Rats given the uncooked silage accumulated more glycogen in the liver than the rats given the cooked silage diet ( p The rats given raw minced capelin performed worse than the rats given the silages of up to 180 days of storage, but they performed better than those with 1 year of storage. This was probably due to the procedure used for mixing the diet.

Total volatile nitrogen — A quality criterion for fish silage?

Abstract Total volatile nitrogen (TVN) consisting mainly of trimethylamine (TMA) and ammonia (NH 3 ), is used as a quality criterion for fish meal and fish meal raw material. Therefore, the significance of TVN and of the NH 3 portion of it as quality criteria for fish silage were studied. Such criteria are required to ensure a wider use of silage in fish feed. Formic acid silages were prepared from fresh raw material of mackerel and of capelin, the latter with varying amounts of acid. In properly preserved silage (stable pH) TVN and NH 3 -N increased moderately during storage and amide-N (from glutamine and asparagine) decreased at the same rate. Amide-N was taken to be the difference between NH 3 -N before and after weak hydrolysis. The amino acid composition was not significantly affected. As asparagine and glutamine are considered to be dispensable amino acids, this is not expected to affect the nutritional value of the silage. When acid addition was too low, the pH increased during storage and there were large increases in TVN and NH 3 -N but a slight decrease in amide-N similar to that found in the other silages. Furthermore, the amino acid composition was affected; arginine and tyrosine seemed most vulnerable. We conclude that amide-N from glutamine and/or asparagine is a major source of the NH 3 formed in properly preserved silage during storage. TVN is thus of limited value as a quality criterion for fish silage.

Effects of sodium nitrite and formaldehyde on the lysine content of fish muscle. Model experiments

Abstract Fish muscle pieces were treated under anaerobic conditions and at different pH values with sodium nitrite and formaldehyde alone and in combination. Lysine and tyrosine were the only amino acids affected under the conditions chosen. Lysine was reduced by some 20% by nitrite alone and by nitrite and formaldehyde in combination at 24h reaction time at pH 5·0, which was the lowest pH value tested. At higher pH values the effect was negligible. Formaldehyde had no effect on lysine. Tyrosine was not affected by nitrite, but formaldehyde alone and in combination with nitrite had a dose-related effect resulting in almost complete loss at the highest levels tested. This effect of formaldehyde was probably an artefact due to a reaction between tyrosine and formaldehyde during hydrolysis of the fish muscle pieces.

Methionine oxidation in commercially and experimentally produced fish meals

Abstract The amounts of methionine oxidized to methionine sulphoxide were determined in 36 fish meals produced in 1988 and in 86 fish meals produced in 1975. The 1988 meals were of three quality grades based on the freshness of the raw material. Total methionine (methionine plus methionine sulphoxide) and unoxidized methionine were slightly higher in the meals of the best quality than in the two other quality grades. The 1975 meals were dried either directly by flame or indirectly by steam. The raw material was unpreserved or preserved with a mixture of sodium nitrite and formalin, and the meals were either protected by addition of an antioxidant or unprotected. There were no significant effects of type of drier or of antioxidant protection on the degree of methionine oxidation whereas there was significantly less oxidized methione in meals from preserved raw material. The various treatments showed little effect on the content of total methionine. In model experiments with fish fillet meals, no obvious effects of oxidizing atmospheres and additions of unsaturated fat (cod liver oil) and trimethylamine oxide (TMAO) on methionine oxidation were found. During storage for 1–2 years a slow oxidation of methionine took place.