Migration and proliferation of primordial germ cells in the early chicken embryo.

In avian species, primordial germ cells (PGC) use the vascular system as a vehicle to transport them to the future gonadal region. The aim of this study was to elucidate the details of migration system and size of the PGC population in the early chicken embryo. We analyzed whole chicken embryos during stages X and 2 to 17 by immunohistochemical staining using specific antibody raised against chicken vasa homolog. At stage X, PGC were dense in the central zone of the area pellucida. Following the formation of the primitive streak, PGC moved anteriorly to the edge of the extraembryonic region. The size of the PGC population increased gradually during stages X (130.4 +/- 31.9) to 10 (439.3 +/- 93.6). At stage 10, PGC began to accumulate in the region anterior to the head, and then we could observe that PGC invaded into the vascular system in this region. At stage 11, the number of PGC decreased in the region anterior to the head (129.8 +/- 42.5 to 46.7 +/- 4.2) and increased in the blood vessels (194.0 +/- 41.6 to 285.0 +/- 7.5). No PGC could be recognized in the intermediate mesoderm, the future gonadal region, until stage 14, but they first appeared there at stage 15. The number of PGC recognized in the intermediate mesoderm increased from stage 15 to 17. Interestingly, the number of PGC between the left and right sides of this region was consistently and significantly different (P < 0.05) in females and males. The present study mainly clarified that chicken PGC continue to proliferate throughout early development, many PGC invaded into the vascular system from the region anterior to the head in stage 11, and PGC actively left the blood vessels and migrated to the intermediate mesoderm from stage 15.

The effect of collection method and housing system on semen production and fertility of Alabio drakes.

Three methods of semen collection from Alabio drakes were compared: the use of an artificial vagina (AV), electro ejaculation (EE) and manual massage (MM). For the latter two methods, drakes were housed in individual cages or in groups in floor pens, while for the AV method all drakes were kept in individual cages. Training success rates of drakes for the three collection methods were similar. Drakes housed in cages produced significantly more semen with a higher sperm concentration, which maintained fertility longer than semen from floor-penned drakes. The average semen volume per ejaculate, sperm concentration and total number of sperm per ejaculate were highest for the AV method while the other two methods did not differ. The average duration of fertility was significantly longer for the AV method (8.8 d) than the EE (6.5 d) or MM methods (5.1 d). The proportion of fertile eggs for 7 d following the insemination of 2 X 10(8) spermatozoa was also highest for the AV method. Although greater skill was required from the operator, the AV method is recommended for general use because of its significantly higher semen yield and longer duration of fertility.