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With few exceptions, the bovine female produces one ovum per estrous cycle, and consequently one offspring per year. Thus,the reproductive rate of cattle is low in comparison to other meat-producing animals, birds and fish. Studies at the University of Wisconsin in the early 1950's indicated that the frequency of twin ovulations was 1O-fold greater than the frequency of twin births. However, a recent evaluation of ovulation rate in the MARC twinner herd indicated that about 50% of the twin ovulations resulted in twin births. With a twinning frequency of 25% in this population, it is suggested that the bovine female does have the capacity to gestate more than one fetus. The objective of this study was to determine the effects of multiple ovulations and/or number of fetuses within the uterus on conception rate, embryonic survival and development, maternal progesterone and estrone sulfate concentrations and placental function, and to assess uterine capacity in cattle.