CHARACTERISTICS OF THE OVULATORY RELEASE OF LUTEINIZING HORMONE IN FINN, FINN × SUFFOLK AND SUFFOLK EWES

Abstract
Department of Animal Science, University of Minnesota, St Paul, Minnesota 55108, U.S.A. (Received 12 July 1977) In sheep, the level of luteinizing hormone (LH) reaches a maximum 5–12 h before the onset of oestrus (Wheatley & Radford, 1969) and ovulation takes place 23–25 h after this peak (Cumming, Buckmaster, Blockey, Goding, Winfield & Baxter, 1973). However, it has been suggested that there is a relationship between the dynamics of the release of LH at oestrus and the rate of ovulation (Thimonier & Pelletier, 1971; Land, Pelletier, Thimonier & Mauleon, 1973). To increase the rate of ovulation, Finn sheep have been used in cross-breeding programmes (Boylan, 1975). This investigation was conducted to determine whether the release of LH at oestrus in Finn, Finn × Suffolk (F × S) and Suffolk ewes differs in the time of onset, magnitude or duration. Mature Finn, F × S and Suffolk ewes weighing 44 ±

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