Plasma Of Heifers Research Articles

Changes in the plasma concentrations of free and conjugated oestrogens in heifers after treatment to induce superovulation and the relationship with number of ovulations.

Oestradiol-17 beta and conjugated oestrone, oestradiol-17 beta and oestradiol-17 alpha were measured in peripheral plasma of heifers treated with PMSG/PGF-2 alpha to induce superovulation. Changes in the concentrations of each hormone were synchronous, the highest level being near oestrus. For a given number of ovulations the hormone with the highest concentration was total oestradiol-17 alpha, then came total oestrone, total oestradiol-17 beta and oestradiol-17 beta. For each oestrogen, the maximum preovulatory concentration measured was significantly correlated with the number of ovulations; the regression line for total oestradiol-17 alpha was twice as steep as that for oestradiol-17 beta. It is concluded that in animals treated to induce superovulation assay of total oestradiol-17 alpha gives a better induction of the number of follicles induced to ovulate than does the more conventional assay of oestradiol-17 beta.

Plasma progesterone concentration in Bos taurus and Bos indicus heifers

Progesterone concentrations were determined by radioimmunoassay in the plasma of heifers of German Brown Swiss, Holstein-Friesian and White Fulani cattle during two consecutive estrous cycles in the dry and wet seasons in a tropical climate. Seasonal differences in the levels were not significant but peak levels were significantly higher in the Bos taurus than in the Bos indicus heifers. The low levels at estrus and the gradual rise five days after estrus were similar among the heifers. The levels on the 1st and 2nd days preceding estrus were significantly higher in the Bos taurus than in the Bos indicus heifers, and suggest a possible tendency for the former to be more susceptible to infertility arising from high progesterone levels 1 and 2 days preceding estrus and insemination. The genital tract and ovaries at the mature luteal phase were generally smaller in the Bos indicus than in the Bos taurus heifers.

Concentrations of luteinizing hormone, oestradiol-17beta and progesterone in the plasma of heifers treated to induce superovulation.

Concentrations of luteinizing hormone (LH), oestradiol-17beta and progesterone were studied in 14 heifers treated with pregnant mare serum gonadotrophin (PMSG) and an analogue of prostaglandin F2alpha (PGF2alpha) 48 h later to induce superovulation. Plasma levels of oestradiol-17beta before ovulation and of progesterone after ovulation were related to the number of ovulations but the concentrations of LH were not so related; however, hormone concentrations at the time of injection of PMSG could not be used to predict the rate of ovulation. The injected gonadotrophin also appeared to affect folliculogenesis after ovulation and this may explain the presence of large follicles in the ovary when the corpora lutea were counted. It was possible to demonstrate by analysis of plasma levels of hormones that few non-superovulated animals were really insensitive to PMSG.