Estrogens and piglet viability. II. Effect of estrogen on piglet viability

The effect of estrogens (Es) on piglet viability was determined as measured by birth to suckling intervals. Starting on d 109 postbreeding daily blood samples were obtained from 15 Yorkshire sows, Immediately after birth, blood samples were taken from the umbilical cord (UC) and the vena cava (VC) of piglets, followed by injections via the VC of either estradiol benzoate (EB) or a saline solution. The interval from birth to suckling (BTS), and body weight gain until 96 h was recorded. Total estrone concentration in the sows' serum rose until the day before parturition and declined sharply by d 2 postpartum. Piglets given EB injections had a shorter interval from BTS (P less than .05) and females suckled sooner than males in both the control and treated groups. No significant differences in weight gain were detected between control and treated groups at 2, 24 or 96 h. Higher (P less than .001) levels of estrone and estrone sulphate were found in the UC than in VC samples, but no correlation existed between levels of Es in the UC and VC (P greater than .05). We concluded that Es or other hydroxylated compounds could be acting upon a high control center of the newborn piglet to cause hyperactivity with a consequent reduction in BTS interval.