Low-field ac susceptibility was measured on bulk La0.7Ca0.3MnO3 prepared by a partial melting technique. Discontinuous jumps with heights of (1 - 2)105 emu at temperature intervals of 3-5 K were observed in the ac susceptibility. 28 jumps were observed in the temperature range between 4.2 K and the Curie temperature of 250 K, with an ac field amplitude of 1 Oe, a frequency of 117 Hz, and a dc bias field of 5 and 20 Oe. Upon increasing the frequency up to 5000 Hz, the jumps shifted to lower temperature. For a dc bias field of 50 Oe and an ac field with an amplitude of 0.1 Oe and a frequency between 117 and 5000 Hz, only three jumps with heights of about 3105 emu at large temperature intervals of about 60 K were observed for TTc . With increasing frequencies, the three jumps shifted to lower temperatures without changing jump height. The discontinuous jumps in La0.7Ca0.3MnO3 were interpreted in terms of thermally and ac-field-activated domainwall jumps.