Abstract
Pregnant pony mares (weight, 115 to 300 kg) were necropsied on the following days after the end of estrus (number of mares in parentheses): 10 (three), 14 (four), 18 (four), 24 (three), 30 (two), 40 (two), 50 (three), 60 (three), 80 (three), 100 (three), 160 (two) and 220 (one). The primary corpus luteum was marked with India ink on day 2 or 3 in the mares which were necropsied on days 24 to 220. In a second experiment pregnant mares were necropsied and the stage of pregnancy was estimated as follows: 150± 15 days (six mares), 180 ±15 days (four mares), 210±15 days (four mares). The weight of the primary corpus luteum in pregnant mares was significantly less at day 14 than at day 10 and tended (P10 mm) after, day 60 and the decrease could be accounted for, at least in part, by the increasing number of secondary corpora lutea. Copyright © 1974. American Society of Animal Science. Copyright 1974 by American Society of Animal Science.