Nafi' narrates from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that he used to say: When a sacrificial camel gives birth, its young should be carried (on a mount) until it is slaughtered along with it; and if no mount can be found on which to carry it, then it should be carried on its mother until it is slaughtered along with her.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10211