Sourced cells can be (and are) immortalized. https://en.m.wikipedia.org/wiki/Immortalised_cell_line https://en.m.wikipedia.org/wiki/Immortalised_cell_line Thi

Sourced cells can be (and are) immortalized. https://en.m.wikipedia.org/wiki/Immortalised_cell_line https://en.m.wikipedia.org/wiki/Immortalised_cell_line This alone removes almost all of the downside suffering. Additionally, for those of a more more absolutist moral bent, when the animals are small in number, there isn't the same financial pressure to ruthlessly optimize cost at the expense of welfare; you can afford to raise the animal in non-torture conditions without it materially impacting competitive position.