Investigation to determine digestibility coefficients of various raw materials in diets for gilthead sea bream, Sparus auratus L.

A number of raw materials were tested to obtain the in vivo apparent digestibility coefficients of protein, lipid and gross energy for gilthead bream. Sparus auratus L., under controlled conditions. In the case of protein digestibility assessment, a standard in vitro method was also included for comparison. Protein digestibility coefficients were generally high, with values between 60% and 96% being observed for most of the materials studied. However, some exceptions were apparent in materials of both animal and plant origin. Lipid digestibilities also ranged between 50% and 90%. Values for energy digestibilities indicated a much greater variation, from 6% to 80%. These observations are discussed in relation to the nature and source of ingredients and to the type of processing technology employed.     

The pathology of chronic erosive dermatopathy in Murray cod, Maccullochella peelii peelii (Mitchell)

Chronic erosive dermatopathy (CED) is a disease of intensively farmed Murray cod in Australia that has been reported in association with the use of groundwater (mechanically extracted from shallow boreholes) supplies. CED results in focal ulceration of the skin overlying sensory canals of the head and flanks. Trials were conducted at an affected fish farm to study the development of the condition, both in Murray cod and in goldfish, and also to assess the reported recovery of lesions when affected fish were transferred to river water. Grossly, lesions began after 2-3 weeks with degeneration of tissue at the periphery of pores communicating with the sensory canals. Widening of these pores along the axis of the canals resulted from a loss of tissue covering the canal. Histopathologically, hyperplasia of the canal epithelial lining was seen after 3 weeks in borehole water and subsequent necrosis and sloughing of this tissue resulted in the loss of the canal roof. Canal regeneration occurred when fish were transferred from borehole water into river water. The lack of lesions in other organs and the pattern of lesion development support exposure to waterborne factors as the most likely aetiology.