Spanish and Mexican Alta California was a primarily cattle-based economy. The wealth of ranchers was measured in the size of their herd. Beef, manteca, and leather were used liberally, and hide and tallow were exported. How many cattle were killed, either annually or in total?
It would be tough to answer this very directly, but it's safe to say that tens of thousands, and possibly up to a few hundred thousand head of cattle, may have been killed per year over many years.
Here is an estimate of the growth in the longhorn cattle population of Alta California:
whereas in 1774 there were only approximately 350 head... by 1800 the missions reported holdings totalling 153,000 head. By 1834 that total had jumped to 396,000 head... populating the lands controlled by 21 missions. By 1850, it has been estimated that nearly 500,000 Longhorns could be found in four counties alone (Los Angeles, Santa Barbara, Ventura, and San Bernardino).
The annual trade in hides in the 1820s and 1830s The History of Alta California: A Memoir of Mexican California by Antonio Maria Osio (pp. 118-120) was estimated around 100,000.
For further details see the book Cattle Colonialism: An Environmental History of the Conquest of California by John Ryan Fischer.