Abstract

The aim of this study was to evaluate preservation methods of catfish by-products (CBP), and the effects of replacing marine fish meal (FM) with these processing byproducts on diet digestibility, performance, feed efficiency and carcass quality in growing-finishing pigs. Paper I presents data on catfish production, processing and the nutritive value of catfish by-product meals (CBM) in the Mekong Delta (MD) of Vietnam. In Paper II, CBP silage made with 20-40% addition of sugar cane molasses (M) was of a better quality than when made with rice bran (RB) at the same levels. The optimum proportion for successful silages with M was 8:2, and with RB 7:3 (CBP and M or RB, fresh weight basis). The total tract apparent digestibility (CTTAD) of CP in CBP ensiled with RB or M was comparable to that of FM, but ether extract (EE) digestibility in ensiled CBP was higher. However, N utilization was not significantly different among FM and silage diets. In Paper III, the coefficient of ileal apparent digestibility (CIAD) of CP in CBP ensiled with M (ECM) tended to be higher than that in CBM, processing waste water (WWB) and FM. However, the CIAD and CTTAD of EE in FM were lower than in CBP. Amino acid digestibility and nitrogen retention were not affected by replacement of FM. Results from Paper IV showed that, the higher the inclusion level of WWB as replacement for FM in the diet, the lower the average daily feed intake (ADFI), amino acid intake and average daily gain (ADG).However, feed conversion ratio (FCR) was improved, and the feed cost was reduced to 68% of that of the FM diet. In Paper V, a higher inclusion level of ECM as replacement for FM in the diet resulted in slightly lower ADFI, but increased ADG. As a result, FCR was improved and feed cost of the diet with 100% CP coming from ECM reduced to 72% of the cost of the diet with 100 % of the CP from FM. Carcass yield and dressing percentage were not affected by ECM replacement, but leaf fat and back fat thickness were higher with higher ECM replacement of FM. There was no effect on DM and CP contents in Longissimus dorsi muscle, but EE and polyunsaturated fatty acid contents increased especially eicosenoic, linolenic, linoleic, DHA and DPA. Meat colour values also increased with increasing ECM replacement level.