Abstract
The present study aimed to evaluate if substitution of chicken egg yolk (CEY) with duck egg yolk (DEY) in diluents could improve and/or affects buck semen quality preserved at 5°C for 120 hr. and to study if changing level of DEY either by increasing or decreasing could affects buck semen preserved at 5°C for 120 hr. Semen samples collected twice weekly from 9 healthy mature bucks were diluted with 6 different diluents containing tris, citric acid, glucose, egg yolk and antibiotic. Diluent 1 contained 2.5% CEY (control), while diluents 2, 3, 4, 5 and 6 contained 1, 2.5, 5, 7.5 and 10% DEY, respectively. After cooling to 5-6°C, semen samples from each diluent were examined and evaluated each 12 hr. for motility, viability, total abnormalities, acrosomal damage and plasma membrane integrity.
The results showed that at 1st 24 hr. diluents 1 (CEY 2.5%), 3 (DEY 2.5%) and 4 (DEY 5%) were significantly higher (P < 0.05) than other diluents in terms of motility, viability and plasma membrane integrity, and significantly lower (P < 0.05) than other diluents in terms of total abnormalities and acrosomal damage. However, after 36 hr. and till 120 hr. diluent 3 (DEY 2.5%) was better than other diluents in the aforementioned parameters. Results also showed that decreasing DEY level in semen diluents as in diluent 2 (DEY 1%) was not satisfactory. Similarly, increasing DEY level in semen diluents as in diluent 4 (DEY 5%), 5 (DEY 7.5%) and 6 (DEY 10%) was not satisfactory and adversely affect spermatozoa which dead after 60 hr. and 84 hr. in diluents 5 (DEY 7.5%) and 6 (DEY 10%) respectively. The present study showed that inclusion of DEY at level of 2.5% rather than CEY 2.5% in diluents could improve bucks semen quality preserved at 5°C.

Key words: buck semen, perservation, duck egg yolk