RELATIONSHIP BETWEEN NUTRITION AND REPRODUCTIVE EFFICIENCY IN OSTRICH (Struthio camelus): YOLK FATTY ACID CONTENT AND FERTILITY

Scarce reproductive performance is one of the most important problems that affect ostrich farm productivity in Italy: 20% of laid eggs is not fertile and just 60% hatches (Salghetti, 2000). Good incubation practices are quite important to improve low hatchability (Gonzales et al., 1999), but nutrition is also a key element. In several farms at the beginning of reproductive period laying percentage and chicks’ conditions are pretty good, but later on the number of laid eggs, fertility and hatchability percentages get worse and worse and mortality increases. The laying period lasts 6-7 months and already at its beginning the ostrich hen has almost the totality of follicles. Moreover, since all the nutrients required for embryo development are prepackaged in the egg prior to laying, worsening of the performance could be due to a progressive consumption of some nutrients (Angel, 1994). Yolk lipids are the primary nutrient source for the avian embryo. The fatty acid components of lipids provide the energy needed for development and are also vital for the synthesis of the phospholipids which form the cell membranes of the growing tissue. Certain tissues of the embryo require large amounts of particular longchain highly-polyunsaturated fatty acids (Speake, 1999). The polyunsaturated profile of the yolk varies greatly between avian species (Surai et al., 1999): the composition of yolk lipids and their utilization by the avian species have been described in several review articles (Noble and Cocchi, 1990; Kuksis, 1992; Speake et al., 1998). Fatty acids profile of yolk is also largely a reflection of the fatty acid composition of the diets, as demonstrated in poultry (Hargis et al., 1991; Nash et al., 1995; Halle, 2001). An adequate knowledge of nutrient requirements is quite important to achieve a “correct” yolk lipid composition and the studies of the nutritive profile of ostrich eggs, as a sign of chick’s conditions, can be useful to better comprehend these topics. Yolk lipid amount of ostrich eggs do not much differ from the other avian species (Sales et al., 1996), but confronted with poultry, ostrich showed difference in fatty acid composition. In poultry the most represented polyunsaturated fatty acid is linoleic acid and its importance in embryo development, particularly embryo’s brain and retina, results in a major consideration in diet formulation, while in ostrich the predominant polyunsaturated fatty acid is linolenic and its content is much greater than in poultry (21.8% vs 1.4%) (Leskanich and Noble, 1997).