English abstract
This study was conducted to use local fish resources to produce fish silage that have a potential to be used as a low cost rich protein supplements for livestock feeding in Oman. A simplified modified method was used for silage making to be feasibly adopted by local fishermen or livestock producers. Fish silage was prepared from ground Indian oil sardines (Sardinella longiceps) using inorganic acid (hydrochloric acid) without addition of antioxidant and no neutralization for pH before use. Fish silage was sun-dried on wheat bran (75:25) before being mixed with other feed ingredients in sheep diets. Chemical characteristics of the fish silage and fish containing diets were evaluated. Forty Omani sheep were used in a feeding trial to one of five diets, formulated from fish silage, soybean meal, barley, wheat bran, ground date palm leaves, limestone, vitamin and mineral mix, salt and vegetable oil. The proportions of fish silage in the diet were 0, 5, 10, 15 and 20% whereas the parallel soybean meal ranged from 17 to 0%. The experimental diets were isonitrogenous (17% crude protein) and isoenergetic (15 kJ/gm gross energy). Animals were housed in individual pens and daily feed intake and weekly body weights were recorded. The experiment spanned 18 weeks with the first 2 weeks of adaptation. Animals were fed 500 g/d of the concentrates and allowed ad libitum access to hay, water and trace elements. A three week (one week adaptation and 10 days collection) digestibility experiment was carried out on twelve sheep fed 0, 10 and 20% fish silage (four sheep per diet). The fresh fish silage dry matter was 39.3% and it contained 51% crude protein, 22% ether extract, 15.3 ash, 3.4 calcium and 3.1 phosphorus. The 75:25 silage:wheat bran contained 88.3 DM, 39 crude protein, 13.9 ether extract, 12 ash, 1.7 Ca and 1.7 Phosphorus. No ill health signs were observed on experimental animals. Haematological and biochemistry investigations showed no treatment effects on blood parameters. There were no differences (P>0.05) in digestibility coefficients of crude protein, acid detergent fibre, and neutral detergent fibre between 0, 10 and 20% fish silage diets. However, the 20% silage diet had lower (P<0.001) DM, ash, Ca, P and energy digestibilities. There were no treatment effects on hay, concentrate or total feed intake; total body weight gain or gain per kg/body weight of experimental animals. Sheep fed the 0, 5, 10, 15 and 20% fish silage diets had average daily body weight gains of 105, 115, 107, 101 and 96 g/d, respectively. There were no diets effects on body composition, carcass characteristics, meat quality or sensory evaluation. This study indicated that fish silage can be prepared easily using a simple technique that can be adopted by any small scale farmers under Omani conditions. Fish silage may be incorporated in sheep diets at levels up to 20% without negatively affecting their performance. Fish silage offers a cheap high protein supplement for feeding livestock in Oman and would reduce feed cost and increase farmer's profit.
