Any chiropractor engaged in the practice of animal chiropractic diagnosis and treatment applying for renewal of a registration related to animal chiropractic diagnosis and treatment must have completed a minimum of six hours annually of continuing education in animal chiropractic diagnosis and treatment, in addition to the required 20 hours annually of continuing education in human chiropractic under this chapter. The continuing education course attended for purposes of complying with this section must be approved by the board prior to attendance by the chiropractor.