The endocrine factors associated with
parturient paresis have not been defined totally.
Estrogens stimulate uptake of
calcium by bone. Since secretion of
estrogen increases dramatically as parturition approaches,
estrogen may be involved in homeostatic mechanisms regulating
calcium metabolism. Plasma was collected for 30 days (-30) prepartum to 5 days (+5) postpartum from six Holstein and nine Jersey cows approaching three or more lactations. Of all cows, six Jerseys contracted
parturient paresis.
Estradiol and
estrone were analyzed by radioimmunoassay, total
calcium and total
magnesium by atomic absorption spectrophotometry, and total
phosphorus by colorimetry. Data were grouped into periods respresenting days -30 to -21, -20 to -11, -10 to -6, -5 to -4, -3 to -2, -1, 0 (parturition), +1, +2 to +3, and +4 to +5.
Calcium in plasma was lower in
parturient paresis cows on days +1 and +2 to +3, and
magnesium was higher during the same periods but lower on days -4 to -5. Total
phosphorus,
estrone, and
estradiol of normal cows and those with
parturient paresis were not different. During the entire sampling period,
phosphorus and
estradiol were similar in both groups while
magnesium was higher and
calcium lower in cows with
parturient paresis.
Estrone was lower in cows with
parturient paresis. Lower
estrone in cows with
parturient paresis may be predisposing for
parturient paresis.