The Indian Contract Act, 1872
163. Bailer entitled to increase or profit from goods bailed –
In the absence of any contract to the contrary, the bailee is bound to deliver to the bailer, or according to his directions, any increase or profit which may have accrued from the goods bailed.
A leaves a cow in the custody of B to be taken care of. The cow has a calf. B is bound to deliver the calf as well as the cow to A.