A comparison of the adrenal cortical response to ACTH stimulation in Angora and non-Angora goats.

摘要

The adrenal cortex is believed to be implicated in the high incidence of abortion in the Angora goat. Stimulation testing with adrenocorticotrophic hormone (ACTH) was used to assess the adrenal cortical function in 5 Angora females from herds with ahistory of abortion and 5 non-Angora females. An acute test involving a single i.m. injection of 0.25 mg of synthetic ACTH was given during anoestrus, at mid-oestrus, on day 90 and on day 120 of gestation. Blood samples were collected from the jugular vein at 30 min intervals for 1 h before and 5 h after injection. Cortisol concentrations rose within 30 min and returned to baseline values within 3.5 h. Cortisol production was lower (p < 0.01) in the pregnant state compared to the non-pregnant state inboth groups. Production of cortisol was consistently lower (p < 0.05) in the Angoras compared to the non-Angoras during anoestrus and pregnancy and marginally so at mid-oestrus. In a chronic stimulation test involving once daily injections of 0.5 mg of adepot form of ACTH i.m. for 7 days commencing on day 90 of pregnancy, cortisol concentrations rose to reach a peak on the third day of treatment in both groups. The values then declined in the Angoras despite continued ACTH treatment, while those for the non-Angoras showed a second peak. During and following this treatment, 2 non-Angoras delivered live kids (day 95, day 120). Out of 7 Angora pregnancies, one Angora aborted 2 dead fetuses at day 116. No significant difference in the cortisol response inthe acute test was detected between the animals that aborted and their respective cohorts, but the 2 non-Angoras that aborted had significantly lower cortisol concentrations during depot ACTH administration. Progesterone and oestradiol levels did not differ between Angora and non-Angora animals during pregnancy or on the test days. The results suggest that the steroidogenic response of the adrenal cortex to ACTH stimulation is significantly less in Angora females with a history of abortion than it is in non-Angoras and support the view that the Angora goat would make a more limited adrenal cortical response to stress during pregnancy.