Abstract
Comparison of Sex Steroid Concentration in Blood Plasma and Ovarian Follicles of White Leghorn and Greenleg Partridge Laying HensThe study was performed to compare plasma and ovarian levels of progesterone (P4) and estradiol (E2) with laying rate in two different breeds of egg-type chickens, i.e. White Leghorn (WL) and Greenleg Partridge (GP). Thirty-five-week-old WL (line H22; n = 8) and GP (line Z11; n = 8) hens were used in the experiment. Blood samples were collected from hens at the time of C1 oviposition (i.e. 0.5 h before C2 ovulation), then at 20, 16, 12, 8, 4, 2 h before C3 ovulation, and at the time of predicted C3 ovulation (i.e. just after C2 oviposition). On the following day, six birds of each breed were decapitated 2 h before ovulation on the next day after the last blood collection. A stroma, small (SWF; 1-4 mm), medium (MWF; 4-6 mm) and large (LWF; 6-8 mm) white prehierarchical follicles, and yellow hierarchical (F6-F1; 8-36 mm) ovarian follicles were isolated. P4 and E2 levels in blood plasma and ovarian follicles were determined radioimmunologically. The average rate of lay in WL hens was significantly higher than in GP hens (P<0.05). The highest concentrations of P4 and E2 were found 4 h before ovulation in both WL and GP hens. In WL hens the levels of P4 at the time of oviposition and at 4 and 2 h before ovulation were significantly higher in comparison with GP hens (P<0.05). On the other hand, higher E2 concentrations were found in GP hens at the time of oviposition and 12, 8 and 4 h before ovulation (P<0.05). In LWF and hierarchical follicles of WL hens the level of P4 was significantly lower than in GP hens (P<0.05). With respect to E2, a reverse relationship was observed in LWF and F6-F4 follicles. In conclusion, the results obtained indicate that in egg-type layers the profiles of plasma and ovarian sex steroids depend on their genotype. The significant differences in sex steroid levels in blood and ovarian follicles of the WL and GP breeds may contribute to explain the endocrinological factors that determined their laying performance and productivity.
Highlights
The ovary of White Leghorn (WL) hens weighed more than the ovary of Greenleg Partridge (GP) hens, there were no differences in their weight in relation to body mass
In the ovary of WL hens we found more SWF and LWF follicles which might potentially be selected into preovulatory hierarchy
Changes in sex steroid levels in blood plasma of WL laying chickens during the ovulatory cycle have been extensively studied in the past, but to our knowledge, this is the first report showing ovarian steroid profile in the ovulatory cycle of GP laying chickens
Summary
Animals The experiment was carried out on WL (line H22) and GP (line Z11) laying hens (35 weeks old) weighing an average of 1.94 ± 0.063 and 1.73 ± 0.059 kg, respectively. Birds were housed in individual cages at neutral temperature (18–20°C) under 14L:10D lighting schedule They were provided with water and commercial feed ad libitum. Three weeks before the onset of the experiment oviposition time had been checked at 15-min intervals between 0700 h and 1600 h. On the basis of recording of egg-laying, cloacal palpation and autopsy it was found that ovulation occurred within 30 min after oviposition of the previous egg in the series which took place between 0700 h and 1000 h. The egg laying rate of WL and GP hens was recorded 10 days before and during the experiment
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