وَالْأَفْضَلُ فِي الْبُدْنِ النَّحْرُ، وَفِي الْبَقَرِ وَالْغَنَمِ الذَّبْحُ.
Translation: The preferred method for a camel is nahr, while for cattle and sheep/goats it is dhabḥ.
Nahr is the sacrificial method preferred for camels.
Dhabḥ is the usual slaughter method preferred for cattle and sheep/goats.
Al-afḍal expresses preference; it does not by itself say every other lawful method is automatically void.