OK, a little misinformation here. PH-BFT is indeed a combi, the horses were not under floor but on the main deck, hence the need for a high-loader for which St. John's possibly lacks. Or, possibly, the horses could not disembark due to quarantine regulations. KLM sends trained animal attendants on every flight with horses, so they would be the ones to take necessary action in case of disruptive behaviour. And although the aircraft has seven pallet positions, it can hold a lot more horses than that because you can fit more than one horse in each stall - nine is by no means unusual.