You can enter them on 4684 but you will only benefit if you itemize on schedule A. That is done under Personal Deductions, Other Deductions and Credits, Casualties and Thefts.
If you reported them as a group purchase you will still need to Edit this asset. Using the example above in the answer of 38 cows for $38000, you will reduce the head count from 38 to 33, then reduce your cost basis in the group from $38000 to $33000. This has removed 5 cows from that group. That 33 cow asset will remain. Now you re-enter those 5 dead cows as a new asset, 5 hd X $1000 =$5000. Edit this asset to report they were sold or disposed of from your farm, (sold for zero dollars). TT will automatically enter the loss onto form 4797, part ll.
