Progesterone and Luteinizing Hormone Levels in Peripheral Blood of Cycling Beef Cows

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Abstract
LEVELS of certain hormones fluctuate during the estrous cycle of the cow. Gomes and Erb (1965) reviewed the literature on progesterone levels in corpora lutea of dairy cattle; luteal progesterone was lowest at estrus and gradually increased to peak levels at days 14 to 15. The concentration of progesterone in ovarian venous effluent (Gomes et al., 1963; Dobrowolski, Stupnicka and Domanski, 1968) and in peripheral blood (Plotka et al., 1967; Gupta and Pope, 1968; Stabenfeldt et al., 1968; Shemest, Ayalon and Luidner, 1968) of dairy cattle followed the same pattern. Progesterone has not been reported for peripheral blood of beef cows but has been determined in luteal tissue (Niswender et al., 1965). Luteinizing hormone (LH) in the pituitary glands of dairy cattle decreased rapidly at estrus as determined by the ovarian ascorbic acid depletion assay (OAAD) (Rakha and Robertson, 1965). Anderson and McShan (1966), using OAAD, found LH to increase in plasma between 6 and 17 hr. before ovulation. Copyright © 1971. American Society of Animal Science . Copyright 1971 by American Society of Animal Science.

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