Effects of Human Chorionic Gonadotropin on Serum Progesterone Concentration During the First Weeks After Mating, Components of Pre-implantation Complete Blood Counts, and Number of Offspring at Parturition in Ewes

Human chorionic gonadotropin (hCG) may boost progesterone production and attenuate maternal-immune response against concepti in ewes, increasing prenatal survival. The present study examined effects of repeated hCG administration after mating on serum progesterone concentration and complete blood counts (CBC) during early gestation, as well as offspring numbers at parturition. Fifty-six ewes were synchronized and mated, then administered saline (CON) or 100 IU hCG on d 4, d 7, d 10, and d 13 after estrus (d 0). Ewes not conceiving were mated again at subsequent estrus. Progesterone was measured on d 4 to d 15 and CBC on d 7 and d 11. In ewes pregnant at treatment, serum progesterone was greater (P < 0.050) in hCG-treated ewes than CON from d 7 through d 15 (final sampling day), while in ewes conceiving at subsequent estrus (after treatment), progesterone was greater (P < 0.050) in hCGtreated ewes on d 11 through 15 only. On d 7, total white blood cells (WBC) and lymphocytes (LYM) were greater (P < 0.050), mean corpuscular volume (P = 0.067) tended to be greater, and eosinophil fraction of WBC tended to be less (P = 0.068) in hCG-treated ewes. On d 11, red blood cells and hemoglobin were reduced (P < 0.050) and hematocrit tended to be reduced (P = 0.055) in hCG-treated ewes. Additionally, neutrophil fraction of WBC was greater (P < 0.050) in pregnant ewes on d 7, total LYM were less (P < 0.050) in pregnant ewes on d 11, and LYM fraction of WBC was less (P < 0.050) in pregnant ewes on d 7 and d 11 than in non-pregnant ewes, independent of treatment. No difference (P > 0.050) was found between treatments for number of ewes pregnant from mating at estrus just before treatment, the first estrus after treatment, the second estrus after treatment, or the number of ewes not pregnant. Frequency of single or multiple lambs at parturition did not differ (P > 0.05) due to treatment in ewes pregnant from mating at any estrus. Repeated administration of hCG during the first two weeks after estrus increased serum progesterone concentration in pregnant and non-pregnant ewes, influenced components of CBC, but did not appear to influence lambing rate or number of offspring at parturition when administered at these doses.