The takeover, for an undisclosed sum, became effective on 1 July and means Highland Game's turnover will be boosted to £10m.
The acquisition would pave the way for Highland Game to expand further as it had previously been held back by a shortage of supply, said managing director Christian Nissen.
"As a result of our success, we got to the situation where we had too much demand for the raw material we'll now be able to fulfil orders that we couldn't complete before."
Highland Game's increased market share would increase the production and supply of venison that is farmed in the UK, resulting in less being brought in from New Zealand, said Nissen.
"I think this is going to be an enormous opportunity to grow production in this country, using not just wild when available, but also farmed, rather than having to import it."
Following a changeover period, Rick Bestwick's game brand will cease to exist and all meat produced under it at the Rick Bestwick premises will be sold under the Highland Game brand instead, added Nissen. "The Highland game brand is what we are renowned for. It is a brand recognised in retailers and wholesalers so everything will be branded under one name."
Highland Game will take on Rick Bestwick's two existing sites in Chesterfield and Perth, and will continue to run them for the time being. Highland Game has its own processing site in Dundee, said Nissen.
"We are currently looking at consolidating the business to make best use of our investment and therefore we'll be assessing in due course how best to do so."
Highland Game supplies game to Waitrose, Asda, Tesco, Sainsbury's and Morrisons, and has product launches in the pipeline.