Lousada owned more than 400 African slaves on his sugarcane plantations in the British West Indies at the time of the Slavery Abolition Act 1833.
Emanuel Lousada's ancestors had been involved in the Atlantic slave trade for several generations, owning sugar cane plantations in Jamaica and Barbados worked by enslaved Africans.
His grandmother Abigail Lamego (1723—1790) was the great-niece of Manuel Rodrigues Lamego who held the official contract (known as the asiento) for the monopoly on providing the Spanish Empire (in particular the Spanish Americas) with African slaves from Portuguese West Africa from 1 April 1623 to 25 September 1631.
Lousada owned 424 slaves in Jamaica and Barbados and received a £6,852 payment at the time (worth £821,378 in 2025).
[9] Some of Lousada's relatives in Jamaica had been awarded titles of nobility; in 1759, Charles III of Spain created a member of the family Duke de Losada y Lousada and another was created Marquis di San Miniato by the Grand Duke of Tuscany.