Date of Award:

1982

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Advisor/Chair:

Warren C. Foote

Abstract

Female Spanish x Dairy cross goats were divided into three reproductive phases--breeding season or cyclic (20), seasonal anestrus (20), and early postpartum (20). Each group of animals was further divided into three treatments--control (10), Gonadotropin Releasing Hormone (GnRH) treated (5), and pituitary Luteinizing Hormone (LH) (5). During each of the above mentioned reproductive phases, the following were measured: progesterone and LH profiles, serum LH levels following GnRH injection, pituitary LH concentration and ovarian responses following GnRH treatment.

Progesterone levels indicative of luteal development were present only in the breeding season. Progesterone levels during the seasonal anestrous and postpartum periods were 0.65 ± 0.03 and 0.3 ± 0.02 ng/ml, respectively, and significantly different (P<0.01)

The LH surge mechanism was operational only in breeding season does,showing LH peaks of 187.86 ± 3.95 ng/ml an average of 13.2 ± 1.47 hours after the onset of estrus. LH levels returned to 2 ng/ml by 48 hours post estrus. There was an inverse relationship between plasma progesterone and LH with mean LH levels of 1.1 ± 0.13 ng/ml during the luteal phase of the cycle. Serum LH levels during the seasonal anestrous and postpartum period were 0.71 ± 0.02 and 0.32 ± 0.02 ng/ml, respectively. These differences in tonic LH secretion were significant.

Tonic LH levels (0.5 ± 0.2 ng/ml) were recorded in all does, regardless of the reproductive phase, prior to the initial injection of GnRH. Serum LH increased to 182.96 ± 54.56, 209.38 ± 41.38, and 97.84 ± 55.84 ng/ml, these peak levels were recorded at 114 ± 4, 135 ± 7, and 135 ± 11 minutes post injection in cyclic, seasonal anestrous, and postpartum does, respectively. Response to the second injection was more rapid and heightened, peaks were achieved from 27 ± 3 to 66 ± 14 minutes post injection, LH peak levels were higher than those recorded following the first injection. Postpartum animals showed reduced responses in all cases.

Pituitary LH concentrations were 1711 ± 378, 2069 ± 265, and 3542 ± 398 μg LH/g tissue in the postpartum, seasonal anestrous, and cyclic animals respectively. Because of high nonspecific binding, these concentrations are considered as estimates, nevertheless, trends observed are considered to be real.

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