SEX DIFFERENCES OF PLASMA LUTEINIZING HORMONE LEVEL FORM BIRTH TO PUBERTY IN THE BOVINE

Bloods samples were collected three times a week from 4 bovine males and 4 females from birth to the age of 50—70 weeks. LH was measured by means of a radioimmunological method. There was no obvious change in basic values after birth up to puberty. The range of basic values for LH in males was 1.0 — 2.5 ng/ml plasma and for females 0.5—2.0 ng/ml plasma. LH peaks up to 19 ng/ml plasma could be demonstrated in the female, frequently at the age of 6—13 weeks, 26—40 weeks, before the first regular cycle. The first oestrus with ovulation and the following normal cycle were found to occur at the age of 41 to 47 weeks.