Peripheral Plasma Progesterone and Oestradiol-17  Levels Before and After Puberty in Gilts

Abstract

A double isotope derivative assay and a simple competitive protein-binding assay were used to measure peripheral plasma progesterone levels during the pig oestrous cycle. In view of the similarity between the results, the more convenient protein-binding method was employed to determine progesterone levels during prepuberty, the oestrous cycle, early and late pregnancy, parturition and lactation. Peripheral plasma oestradiol-17\g=b\ levels were measured during the oestrous cycle, early pregnancy and around the time of parturition.

Blood Hormone Changes Associated With Puberty in the Female Pig

“…The occurrence of peak plasma progesterone levels during the estrous cycle is in agreement with those observed by Connor et al (1916) and Shearer et al (1972).…”

“…These are perhaps due to a strong negative feedback effect on the hypothalamus by the circulating levels of estrogens present at this time. Foster and Karsch (1916) (Shearer et al 1972). Lowest progesterone concentrations were recorded in this study a few days before and on day 0 of the first and second periods of estrus, which is consistent with those recorded in the mature gilt at these times of the ovarian cycle (Shearer et al 1972;Connor et al 1916).…”

Response of sows to oestradiol benzoate treatment after weaning at two stages of lactation

“…In this respect oestradiol benzoate treatment appears to have a potential application in commercial practice, in particular in those herds using artificial insemination although there is a consistent reduction in ovulation rate which could lead to unacceptably small litter sizes at term. However, the post-treatment concentrations of plasma oestradiol-17ß in the present studies were significantly higher at both dose levels of oestradiol benzoate employed than those previously reported for untreated cyclic and weaned sows in the preovulatory period (Shearer, Purvis, Jenkin & Haynes, 1972; de Wiel et al, 1981 ;Edwards & Foxcroft, 1983), and a further reduction in the dose of oestradiol benzoate might minimize any detrimental side effects without causing a diminished ovuiatory response.…”

Post-Partum Oestrus in the Sow in Relation to the Concentration of Plasma Oestrogens

“…Behavioural oestrus in cyclic gilts and weaned sows occurs approximately 12 to 24 hr after a peak of oestrogen concentration in the peripheral blood plasma (Shearer et al, 1972;Ash et al, 1973). This oestrogen is of ovarian origin, whereas shortly after parturition in sows there is morphological evidence to suggest a period of follicular quiescence (Burger, 1952;Palmer et al, 1965;Crighton & Lamming, 1969).…”

“…The peak of oestrogens in the blood that occurs at parturition, which is considerably higher than peaks in cyclic animals (Shearer et al, 1972), is apparently responsible for causing the early post-partum oestrus of the sow, even though this event has been recorded up to 4 days after farrowing in lactating sows (Burger, 1952). Thus, the outcome of efforts to breed at this oestrus will clearly not be successful (Burger, 1952 ;Baker et al, 1953 …”