How old can you castrate with elastics? I have used them in the past on calves and young kids, but my kids are 4 months old now. I just bought 27 boer goats including the buck that I used last year. The problem is 2 of the 10 month olds came into heat. I seperated the billy but my bucklings are chaseing them all over, and they are half brother/sister. Not shure if they were bred. I want to wean the bucklings next week, so I figured I would castrate at the same time.