Great question. You purchased 38 cows (breeding stock) and entered them as deprecating assets, good. Was this entered as a single asset group purchase (38 cows X $1000/hd =$38000) or each cow individually? What you will do is Edit the asset to report how it was disposed of from your farm business. This is done easily if the cows are entered individually. If 5 died you report that you sold them for Zero dollars. Then TT will remove them from your Asset Summary for next year. If they died after owning them less than a year this will result in a short term business loss reported on form 4797, part ll.
Here is a link to another Q&A you may find helpful;
https://ttlc.intuit.com/questions/3587134-our-cows-which-we-listed-as-assets-last-year-had-calves
