Luteal features and serum concentrations of progesterone and hCG in dairy goats submitted to estrus induction followed by intrauterine or intramuscular hCG administration

Abstract

This study evaluated the effect of hCG administration by different routes on D7 (D0=estrus onset) on serum concentrations of hCG and progesterone (P4). Its role in the induction of accessory corpora lutea (aCL), total luteal area (TLA), and vascular area (VA) was assessed by ultrasonography (US). Forty-four goats had estrus induced with intravaginal sponges (60 mg of MAP, six days) plus 200 IU recombinant eCG and 131.5 μg cloprostenol via intramuscular (i.m.) 24 h before sponge removal. Goats received 300 IU hCG either via intrauterine (hCG-IU, n=8) or i.m. (hCG-IM, n=11) or 1 mL of saline i.m. (control, n=12). Estrus was detected and goats were mated with fertile bucks. On D21, goats from hCG-IU and hCG-IM presented more CLs than control ones (P<0.05). The aCL was not detected in the control and differed (P<0.05) between hCG-IU (25.0 %; 2/8) and hCG-IM (63.6 %; 7/11). TLA increased in hCG-IM between D13 and D17 (P<0.05) and VA was higher (P<0.05) in the hCG-IU on D13. On D7, the hCG concentration was similar among groups (P>0.05), however, it increased (P<0.05) on D7.5 in the hCG-IM and remained higher than hCG-IU and control until D8. The concentration of P4 did not differ (P>0.05) among groups. The pregnancy rate did not differ (P>0.05) between hCG-IM (91.0 %) and control (83.0 %) and both were higher (P<0.05) than hCG-IU (25.0 %). In conclusion, despite a slight improvement in luteal perfusion, intrauterine administration of hCG showed limited benefits on the parameters studied, not promoting significant changes in the reproductive tract environment.