Silage preparation from tuna fish wastes and its nutritional evaluation in broilers
1999
Vizcarra-Magana, L.A. | Avila, E. | Sotelo, A.
The present study was conducted to obtain tuna waste silage from the canning industry by using fresh fish viscera for the autolytic process. Chemical characterisation of the product and nutritional evaluation for broiler diets were then carried out. Three types of studies were performed. In study one the proximal composition was measured and three acid mixtures were tested for silage development. The formic-sulphuric acid mixture was chosen. The measurement of non-protein nitrogen (NPN) formation indicated that more than 50% NPN was obtained after 2 days of storage; pH changes were also measured and stabilisation occurred after 24h. Contents of aerobic mesophiles, total coliforms, yeast and mould were reduced during the first month of storage. Study two was then conducted to determine the proteolytic activity in fresh viscera, the changes in lipid oxidation and the trimethylamine formation during silage development. It was observed that cooked dark meat wastes were oxidised at the beginning, but trimethylamine did not change during 2 months of storage. Thirty-nine per cent of tryptophan content was lost, but available lysine decreased only 8% from original content after 20 days of storage. Fe, Ca, P, Zn, Na and K contents were also measured. A larger batch of silage was obtained and dried after sorghum addition. The silage-sorghum ratio was 70:30. Four starter diets for 9-day-old broiler chicks were prepared at different levels from the final dried silage (5, 10 and 15%). The control diet (0%) contained soybean meal as the predominant protein supplement. Food intake, weight gain and feed conversion were recorded during the short-time feeding study. There were no significant effects of dietary inclusion on the final dried product (p < 0.05). The results showed that 15% of this product can be included without adverse effects on broilers.
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