I see your point, though probably not in the way you mean. So let's pay attention shall we? FCS and FBS are collected from slaughtered dairy cows once they have exhausted their productive lifespans and rendered into meat. Details:

>After slaughter and bleeding of the cow at an abattoir, the mother's uterus containing the calf fetus is removed during the evisceration process (removal of the mother's internal organs) and transferred to the blood collection room. (3). A needle is then inserted between the fetus's ribs directly into its heart and the blood is vacuumed into a sterile collection bag. This process is aimed at minimizing the risk of contamination of the serum with micro-organisms from the fetus and its environment. Only fetuses over the age of three months are used otherwise the heart is considered too small to puncture. (4)

>Once collected, the blood is allowed to clot at room temperature and the serum separated through a process known as refrigerated centrifugation.

>It remains questionable as to whether or not fetuses have already died from anoxia (deprivation of oxygen) prior to serum collection. Nevertheless, no anesthesia is given, despite their possible ability to experience pain and discomfort.

Gestation period for a cow is around 7 months. Drawing an analogy to studies of human sentience (I am not an expert though), this is proprtionally well past the 1st trimester point where foetuses can feel pain. To speak in your language, FCS and FBS are essentially sourced from blood sucked out of the hearts of late-stage unanaesthetized 2nd-3rd trimester abortions. In this light it is not very difficult to see why vegans such as myself still have reservations about cultured meat.