Silvia Cerolini

Viability, susceptibility to peroxidation and fatty acid composition of boar semen during liquid storage

The changes in viability, susceptibility to peroxidation and fatty acid composition of total phospholipid were studied in boar spermatozoa during 5 day liquid storage in a standard or alpha-tocopherol (alphaT) enriched diluent. The sperm rich fraction of the ejaculates was collected from 6-month old boars. Sperm viability progressively decreased during storage and alphaT inclusion into the diluent significantly inhibited this trend. alphaT inclusion also decreased significantly peroxidation (TBARS production of spermatozoa). Spermatozoa stored in the treatment diluent became rapidly enriched in alphaT with a concomitant decrease of alphaT content in the medium. The proportion of polyunsaturates, mainly 22:6n-3, decreased with a complementary increase in the content of the saturates, mainly 18:0. The inclusion of alphaT into the diluent was effective in totally preventing the significant decrease of 22:6n-3 observed in sperm phospholipid in the control samples during the storage period. It is concluded that the alphaT inclusion in the boar semen diluent increased cell viability through its prevention of an oxidative reduction in the levels of the major polyunsaturated fatty acids, namely 22:6n-3.

Fatty acid composition, glutathione peroxidase and superoxide dismutase activity and total antioxidant activity of avian semen.

This work demonstrates that spermatozoa from five avian species (chicken, turkey, guinea fowl, duck and goose) are all characterised by high proportions of polyunsaturated fatty acids, from 46 (turkey) to 55% (duck) of total. For each of the species, the most abundant fatty acids were arachidonic (20:4n-6) and docosatetraenoic (22:4n-6) acids, representing between 22 (turkey) and 40% (chicken) of total. Significant activities of the major isozymes of superoxide dismutase and glutathione peroxidase, which protect against the peroxidation associated with high degree of fatty acid unsaturation, were found in spermatozoa from all species. The seminal plasma also had these activities and showed additional mechanisms for protecting spermatozoa from peroxidation. In general terms, these lipid and enzyme proteins were similar between the five avian species and different from those reported for mammalian sperm.

Dietary fish and evening primrose oil with vitamin E effects on semen variables in cockerels

1. Our aim was to determine the effect of n-3 (2%, wt/wt, fish oil rich diet) and n-6 (2%, wt/wt, evening primrose oil rich diet) fatty acid dietary supplementation and their combination with two concentrations of vitamin E (40 vs 200 mg/kg) on semen variables and on fatty acid and vitamin E profiles of spermatozoa in broiler breeders at 32, 42 and 52 weeks of age. 2. The inclusion of fish oil in the cockerel diets increased the docosahexaenoic acid proportion in the sperm phospholipid fraction, which was almost threefold higher compared to the other two groups irrespective of vitamin E supplementation. 3. In contrast, an increase in the proportion of total n-6 polyunsaturates, mainly 22:4n-6, was observed in the evening primrose oil group compared to the control only when the dietary content of vitamin E was increased to 200 mg/kg. 4. Sperm concentration was decreased in the fish and evening primrose oil groups if vitamin E was 40 mg/kg, but such an effect was prevented in the fish, not the evening primrose oil group, by increasing the vitamin E to 200 mg. 5. The proportion of motile spermatozoa was improved by the increased supplementation of vitamin E in all oil treatments.

The preferential mobilisation of C20 and C22 polyunsaturated fatty acids from the adipose tissue of the chick embryo: potential implications regarding the provision of essential fatty acids for neural development.

The aim of this study was to determine the relative mobilisation of the different fatty acyl components of the triacylglycerol (TAG) of the chick embryos adipose tissue in the light of the specific requirements of the developing neural tissues of the embryo for C20-22 polyunsaturated fatty acids. Pieces of adipose tissue, obtained from embryos at various developmental stages, were incubated in vitro in Dulbeccos Medium containing serum albumen. The fatty acid compositions of the initial tissue TAG and of the free fatty acid (FFA) mobilised from the tissue during 1 h of incubation were determined and compared. The composition of the FFA released into the medium under conditions of basal (i.e., unstimulated) lipolysis was markedly different in several respects from that of the TAG from which it originated. The polyunsaturated fatty acids, 20:4n-6, 20:5n-3, 22:5n-3 and 22:6n-3, were consistently found to be preferentially released into the medium, whereas the major fatty acyl constituents of the tissue, 16:0 and 18:1n-9, were selectively retained in the TAG. For example, at day 18 of development, the proportions (% w/w of fatty acids) of 20:5n-3 and 22:6n-3 released into the incubation medium were respectively 6.5 and 7.5 times higher than in the original tissue TAG. Glucagon stimulated the overall rate of mobilisation by approx. 2-fold and also partially suppressed the preferential mobilisation of C20-22 polyunsaturates. These results may be relevant to the elucidation of the means by which essential polyunsaturates are delivered from the yolk to the neural tissues of the embryo, with the implication of a mediatory role for the embryonic adipose tissue in this transfer.

Effect of n-3 and n-6 fatty acid supplemented diets and vitamin E level on semen quality in cockerels

mammalian spermatozoa, cholesterol has been shown to be involved in the process of capacitation (Langlais and Roberts, 1985). The aim of the present work was to develop a method of modifying the cholesterol content of spermatozoa without affecting the viability of the gametes, for further studies of semen biology. Five pools of spermatozoa from five males were separated from seminal plasma by centrifugation. They were then diluted 1:3 either in BPSE alone or in BPSE supplemented with blood lipoproteins of the same males. The lipoproteins were LDL containing 2·5 times more cholesterol than the spermatozoa (2·5 LDL) or HDL containing 25 times more cholesterol than the spermatozoa (25 HDL). Samples were then incubated for 1 h at 20°C. After the incubation, the lipoproteins were discarded. Mobility, viability, morphological integrity (eosin–nigrosin smears), and lipid profiles (thin layer chromatography) of spermatozoa were then measured. Clearly, the cholesterol/phospholipid ratio increased in spermatozoa previously incubated with either LDL or HDL. This is due to an increase in cholesterol content without any change in phospholipid content (data not shown). This increase was twice as high with LDL than with HDL. By contrast, the quality of spermatozoa was not affected by incubation with LDL while incubation with the high dose of HDL affected the mobility but not the proportion of viable and normal spermatozoa. This indicates that, as for other cell types, the interactions between spermatozoa and the physiological cholesterol donors depend on the nature of the lipoprotein used. It is therefore possible in vitro to increase the proportion of cholesterol of fowl spermatozoa without affecting semen quality by using LDL. The deleterious effect of HDL may not be due only to the very high dose used, and further work is needed on the use of HDL, which is the only lipoprotein present in fowl seminal plasma (Blesbois and Hermier, 1990).