Basic and applied aspects of female reproduction in farmed ostriches

Abstract

This thesis investigated basic and applied aspects of female reproduction in farmed ostriches throughout the 48h egg laying cycle, during the egg production season, and, the non-breeding season. The main objectives were: (1) to evaluate the use of transcutaneous ultrasound scanning to visualize functional changes within the female reproductive organs; (2) to evaluate the plasma hormone profiles of progesterone, luteinizing hormone (LH) and estradiol-17beta (estradiol); and, (3) to study the relationship between the functional, morphological changes in the female reproductive organs and the concurrent changes of the above mentioned plasma hormone levels. First, a technique for on-farm transcutaneous ultrasound scanning of the female reproductive organs is described. By comparing ultrasonographic images with post mortem ovarian morphology, the following morphological structures could be identified: ovarian follicles of different sizes (diameter 1 to 9 cm), atretic follicles, post-ovulatory follicles, and eggs in different stages of development within the genital tract. In total 58% of the number of follicles (> 3 cm) counted during post mortem investigation were detected during the previous in vivo examination. Second, ten egg-producing ostriches were repeatedly investigated during the 48h egg laying cycle. Ultrasound scanning was performed at 3h intervals and blood sampling at hourly intervals. In eight hens, ovulation of the next egg in the laying sequence occurred within 2h after oviposition, while the developing egg remained for 9h in the proximal part of the oviduct, and for 39h in the distal part (shell gland). Follicular mass, estimated by the volume of visualized follicles > 3 cm, increased before ovulation and decreased right after it. In ovulating hens, plasma progesterone, LH and estradiol concentrations showed a characteristic profile, peaking before oviposition. Additionally, it was shown that: (1) the volume of the largest measured follicle (VF1), progesterone and estradiol were all higher before oviposition, increased towards oviposition, and increased when LH increased; (2) progesterone increased when LH, estradiol and VF1 increased. Third, ultrasound scanning and blood sampling for plasma hormone analyses were performed in nine hens on a monthly basis throughout one year. The number of large follicles (> 6 cm) and LH concentrations were elevated already one month before the first eggs of the season were produced. Estradiol concentrations increased as soon as egg laying started. The number of large follicles, LH and estradiol concentrations were elevated during the entire egg production season, and decreased after the last eggs of the season were produced. In conclusion, transcutaneous ultrasound scanning in ostriches is a practical diagnostic technique for visualizing morphological structures within the female reproductive organs, and, following changes on the ovary and within the oviduct over time. Finally, ultrasound scanning can be used as a selection tool on farm to: (1) identify hens showing early ovarian activity in the pre-season, (2) quantify the egg production potential of individual birds at the start of the season, and (3) distinguish laying from non-laying, or, ovulating from non-ovulating hens during the egg production season.