A: No, But I have some for you as his parent.
Actually your son's sensitivity about animals being used in the Mosaic sacrificial system presents you with a wonderful teaching opportunity.
I would start by reminding him that God created animals, and He delights in all that He created. Then I would begin to share about how sin came into the world. Read him the passages in Genesis that tell how Adam and Eve disobeyed God and believed Satan instead. Take time to explain the gravity of sin, and show him that sin completely separates us from God and His love for us. Show your son Bible verses that speak of God's plan for saving us from our sin, and remind him that it involved God sending His only Son to die on a wooden cross.
Once you've shared those things, explain to him that God established a system of reminding his people just how bad their sin was by incorporating the sacrifice of animals. He did this so that every time an animal was killed, they would be reminded that the wages of sin is death. (Romans 6:23) And that without the shedding of blood there is no forgiveness of sins. (Hebrews 9:22)
But remind him that God also said that the blood of goats and bulls could never pay the price for our sin. (Hebrews 10:11) Animal sacrifices were used to foreshadow a very special sacrifice that was still to come—when God would sacrifice His one and only Son.
I would say something like, "Do you know how awful you feel when you think about animals being killed? Well, can you imagine how God felt by seeing His precious Son dying on that cross for you and me?"
The point of this is that you have a wonderful opportunity to pass along to your son that taking care of sin was not an easy thing for God to do. That's because our sin is really bad! It couldn't get cleaned up easily, and it required God to send His own Son to die for us. But until it was time for Jesus to come, God reminded His people every day that sin causes death, and it is only through death that we can have Life.
This may sound like a lot to take in at the age of 11, and it is. Your son has a sensitive heart, and that's okay. But in your sharing with him you can make the point that while the sacrificing of animals shows how terrible our sin really is, it also shows how deep and wonderful God's love is for us. Because it paints a picture of how far God was willing to go so that we might be saved.
God bless you!