In absolute numbers that's not even remotely true. According to FAOSTAT the undisputed top 1 is mainland China (175M) followed by Australia (75M), India (64M), Sudan (52M) and Iran (50M). New Zealand is down to 31M heads and it's been falling pretty much continually since the 1999 uptick to 46M heads.

NZ may have the highest number of sheep per capita and highest sheep density (especially since FAOSTAT doesn't list Wales independently)