When Mackenzie Kirker-Head joined the Horseracing Integrity and Safety Authority last summer as its communications manager, she arrived with a strong desire to support and strengthen the industry that she has loved since she was a child. The 31-year-old native of Massachusetts, now living in Lexington since 2015, previously worked as a marketing manager at MyRacehorse, the microshare platform that caters to more than 50,000 owners.