Ovarian Characteristics and Serum LH, Prolactin, Progesterone and Glucocorticoid from First Estrus to Breeding Size in Holstein Heifers

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Abstract
PITUITARY LH, FSH and prolactin have been determined during puberty and during the estrous cycle in cattle (Desjardins and Hafs, 1968; Sinha and Tucker, 1969; Hackett and Hafs, 1969). In these studies, decreased hormones in the pituitary generally were interpreted to reflect increased hormones in the blood. Although only limited data are available on blood concentrations of LH and prolactin (Schams and Karg, 1969, 1970; Henricks, Dickey and Niswender, 1970; Hansel and Snook, 1970) during the estrous cycle of cows, apparently levels of LH in blood and pituitary usually are negatively related while levels of prolactin may be negatively or positively related depending upon stage of estrous cycle. We found no data on blood LH or prolactin during puberty in heifers. Of ovarian and adrenal hormones, only progesterone has been reported during the estrous cycle in cattle (Stabenfeldt, Ewing and McDonald, 1969; Henricks et al., 1970). The present study was designed to determine blood LH and prolactin during puberty, to determine blood LH, prolactin, progesterone, cortisol, and corticosterone during estrous cycles from first estrus to breeding size and to relate these hormones to ovarian characteristics. Copyright © 1972. American Society of Animal Science . Copyright 1972 by American Society of Animal Science.

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