The n-3:n-6 ratio ranged between 0.1-0.9 in diets, whilst it was 0.5-1.4 in the eggs from fish fed their respective diets at full and half ration. The n-3:n-6 ratio increased in the eggs as the ratio was increased in the diets (Figure 4.21).
0
TSFA% in eggs from full ration
TSFA% in eggs from half ration
Figure 4.14 Total saturated fatty acid (TSFA) levels in three diets and in eggs originating from O. niloticus fed these diets at either full or half ration. Data presented as percentage total lipid.
0 ARA% in eggs from full ration ARA% in eggs from half ration
Figure 4.15 Arachidonic acid (ARA) levels in three diets and in eggs originating from O. niloticus fed these diets at either full or half ration. Data presented as percentage total lipid. EPA % in diets total lipid
EPA % in eggs total lipid
EPA% in diets total lipid EPA% in eggs from full ration EPA% in eggs from half ration
Figure 4.16 EPA levels in three diets and in eggs originating from O. niloticus fed these diets at either full or half ration. Data presented as percentage total lipid.
0 DHA% in diets total lipid
DHA% in eggs total lipid
DHA% in diets total lipid
DHA% in eggs from full ration
DHA% in eggs from half ration
Figure 4.17 DHA levels in three diets and in eggs originating from O. niloticus fed these diets at either full or half ration. Data presented as percentage total lipid.
0 Tn-6% in eggs from full ration Tn-6% in eggs from half ration
Figure 4.18 Total (T) n-6 levels in three diets and in eggs originating from O.
niloticus fed these diets at either full or half ration. Data presented as percentage total lipid.
0 Tn-3% in eggs from full ration Tn-3% in eggs from half ration
Figure 4.19 Total (T) n-3 levels in three diets and in eggs originating from O.
niloticus fed these diets at either full or half ration. Data presented as percentage total lipid.
TPUFA% in eggs from full ration
TPUF% in eggs from half ration
Figure 4.20 Total (T) PUFA levels in three diets and in eggs originating from O.
niloticus fed these diets at either full or half ration. Data presented as percentage total lipid.
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
0.1 (Diet 2)
0.2 ( Diet 3)
0.9 (Diet 4) n-3:n-6 ratio in diets total lipid
n-3:n-6 ratio in eggs total lipid
n-3:n-6 ratio in diets total lipid n-3:n-6 in eggs from full ration n-3:n-6 in eggs from half ration
Figure 4.21 n-3:n-6 ratios in three diets and in eggs originating from O. niloticus fed these diets at either full or half ration. Data presented as percentage total lipid.
4.6 Discussion
To determine eggs quality, in the present study, eggs originating from fish fed their respective diets and rations during their entre life cycle; from the onset of exogenous feeding until spawning (for a period of 18 months).
Broodstock nutrition and genetics appear to be major factors in egg quality (Kjesbu and Holm, 1994). Broodstock nutrition is also vital in the production of high-quality eggs and larvae, and dietary lipid and fatty acid compositions are known to be important factors in determining the success of the developing embryos and larvae (Hu et al., 2009; Izquierdo et al., 2001b; Salze et al., 2005; Tandler et al., 1995).
The biochemical composition of fish eggs is related to spawning performance and egg quality, as egg composition must satisfy embryonic nutritional needs for development and growth (Craik, 1985; Harel et al., 1994; Lu and Takeuchi, 2004;
Sandnes et al., 1984). In fish, lipids are important nutrients for successful embryonic development (Boulekbache, 1981; Castell et al., 2004; Sargent, 1995;
Terner, 1979). Particular interest has focused on the role that the essential fatty acids (EFA), particularly docosahexaenoic acid (DHA: 22:6(n−3) and eicosapentaenoic acid (EPA: 20:5n−3), play in egg and larval development (Bell et al., 1997; Bruce et al., 1993, 1999; Castell et al., 2004; Czesny et al., 2000; Estevez et al., 1999; Gunasekera et al., 1995; Hu et al., 2009; Ramos et al., 1993; Sargent, 1995; Thrush et al., 1994). Recently, attention has partly shifted to include arachidonic acid (ARA: 20:4n−6), mainly because of its role in eicosanoid production (Abayasekara and Wathes, 1999; Bell et al., 1996; Farndale et al., 1999).
This is also due to the involvement of eicosanoids in a range of physiological
functions, including reproduction and egg development (Abayasekara and Wathes, 1999).
One of the principal objectives of the present study was to evaluate the effect of different dietary lipid sources on egg quality in terms of lipids and fatty acid composition, with the goal of replacing fish oil with palm oil in tilapia feed.
Fishmeal which is commonly used as a protein source for aquafeed, contains up to 9% fish oil (De Boer and Bickel, 1988). Therefore, to avoid the effects of fish oil, soy-protein concentrate was used as the protein source for experimental diets.
Previous studies in other species have shown that palm oil can be used to replace fish oil with no negative effect on growth performance (Al-Owafeir and Belal, 1996; Bell et al., 2002; Bell and Sargent, 2003; Kanazawa et al., 1980; Legendre et al., 1995; Ng et al., 2000; Ochang et al., 2007a; Ochang et al., 2007b; Tortensen et al., 2000; Varghese and Oommen, 2000). Limited information, however, is available on the effect of palm oil on tilapia reproductive performance, particularly the effect of lipid and fatty acid composition of tilapia eggs. The present study is the first attempt to investigate the effect of dietary lipid sources on reproductive performance of tilapia which were fed the same diet and ration levels throughout their entire life cycle.