Bava Kamma 47A

ליתה לפרה ⁠– משתלם רביע נזק מולד.

if the cow is not here, e.g., it went astray, only 1/4th of the cost of the damage is reimbursed from the offspring.

טעמא דלא ידעינן אי הוה ולד בהדה כי נגחה, אי לא הוה; אבל אי פשיטא לן דהוה ולד בהדה כי נגחה ⁠– משתלם כוליה חצי נזק מולד;

The Talmud infers: According to Rava, the reason for paying only 1/4th of the cost of the damage is that we do not know if the offspring was with it, as a fetus, when the cow gored or whether it was not. But if it is obvious to us that the offspring was with it as a fetus when it gored, the full amount of half the cost of the damage may be reimbursed from the offspring if the cow is not there.

רבא לטעמיה, דאמר רבא: פרה שהזיקה ⁠– גובה מולדה. מאי טעמא? גופה היא. תרנגולת שהזיקה ⁠– אינו גובה מביצתה. מאי טעמא? פירשא בעלמא הוא.

The Talmud comments: In this respect, Rava conforms to his line of reasoning, as Rava says: In the case of a cow that caused damage while pregnant, the injured party collects compensation from its offspring, i.e., the offspring that had been a fetus at the time of the goring. What is the reason? It is because it is considered an integral part of its body and therefore may be used to collect payment. By contrast, in the case of a hen that caused damage, the injured party does not collect compensation from its egg. Payment can be collected only from the body of the hen. What is the reason? The egg is simply a secretion and not an integral part of the hen’s body.

ואמר רבא: אין שמין לפרה בפני עצמה ולולד בפני עצמו, אלא שמין לולד על גב פרה. שאם אי אתה אומר כן ⁠– נמצא אתה מכחיש את המזיק.

§ And Rava also says: When assessing the damage inflicted by a goring ox on a cow whose newborn calf is found dead by its side, the court does not appraise the damage to the cow by itself and the damage to the offspring by itself. Rather, the court appraises the offspring together with the cow and evaluates the overall damage inflicted on the pregnant cow, which will be slightly less than it would be with two separate evaluations. The reason for this is that if you do not say this, you will be found to have ultimately weakened the one liable for damage by inflicting a loss on him, as the market value of a newborn calf is greater than the difference in market value between a pregnant cow and one that is not pregnant.