Placenta Expulsion-time on Different Age and Breed Cows Erif Maha Nugraha Setyawan, Yosua Kristian Adi, Topas Wicaksono Priyo, Surya Agus Prihatno, Sri Gustari, Asmarani Kusumawati and Agung Budiyanto BIO Web Conf., 33 (2021) 04007 Published online: 23 August 2021 DOI: 10.1051/bioconf/20213304007