Sixty-four cows were blood sampled and physical signs of impending parturition were scored daily from Day 272. Sampling and scoring ceased on Day 282 of gestation or when parturition occurred, whichever came about first. Mean udder development scores increased from 2.0 ± 0.76 (± SD) on Day -10 (ten days prior to parturition) to 3.2 ± 0.72 (± SD) on Day 0 (day of parturition) with 84% of cows having an udder score of 3 or 4 on the day prior to parturition (Day -1). Teat distension, vulva swelling and oedema were not useful as indicators of imminent parturition. Udder score was the most useful predictor, but the low frequency of scores less than 2 and greater than 3 on any one day resulted in unstable models. Plasma samples were assayed for progesterone, PGF2a metabolites (PGFM), cortisol and oestradiol. Oestradiol concentration on Day 274 was a useful predictor of whether an individual cow would calve within eight days (P=0.02). Plasma oestradiol concentrations used to build models to predict whether a cow would calve within the next five days were accurate from Day 272 to 275 of gestation (P<0.05). Progesterone, PGFM and cortisol were unreliable indicators.
Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 34-37, 2002
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