Is it obligatory to combine sheep and goats to complete the Zakat nisab? And are their younglings combined with their adults in calculating the nisab if they are produced after half a year? And is the samn (ghee) produced from them added to the obligatory Zakat?

Zakat is not obligatory on sheep unless they are pasturing and graze for most of the year. Sheep (ḍān) and goats (maʿz) are considered one genus; thus, one is added to the other to reach the nisab. The nisab is forty sheep. Young sheep are added to older ones for the purpose of the hawl (one year of ownership) and nisab. If young and old, or healthy and defective, or male and female sheep are combined, then a sheep of average value between the two types of animals should be given.