RELATIONSHIPS OF PERIPARTUM, PLASMA-CONCENTRATIONS OF PROGESTERONE, ESTROGENS AND 13,14-DIHYDRO-L5-KETOPROSTAGLANDIN F2-ALPHA IN HEIFERS AND OF ANATOMICAL MEASUREMENTS OF DAM AND CALF WITH DIFFICULTY OF CALVING IN EARLY-BRED HEREFORD X FRIESIAN HEIFERS

Plasma concentrations of progesterone, oestradiol-17 beta, oestrone, o estrone sulphate and PGFM have been measured daily during the first pe ri-partum period of 45 Hereford X Friesian heifers bred at 11 months o f age. Anatomical measurements of dam and calf were also recorded. Twe lve of the calvings were scored easy, 33 difficult. Each of five model s (fitted by linear logistic regression) relating difficulty of calvin g to the hormonal and anatomical measurements, predicts with at least 94% accuracy the calving score (easy or difficult) among the calvings, The models predict that increases of progesterone concentration on th e day before calving, of oestrone sulphate concentration on the day af ter calving and of heifer heart girth decrease the odds of difficult c alving, whereas increases of heifer body length and of calf head circu mference increase the odds of difficult calving. (C) 1998 Elsevier Sci ence R.V. All rights reserved.