No, did several with a full complement of cows in the forward belly with no access either, never lost one. They were Instone charters so I'm sure they know what they're doing. Set the pack flow switches to full on the lower maintenance panel and open the vent panel in the forward belly left hand sidewall and off you go. Crew were also asked to keep the cabin altitude higher than normal auto schedule to reduce temperature and cycle the outflow valve every 30 minutes so it didn't freeze due to all that extra moisture.That was many years ago (pre BSE!) so the regulations may have changed since then?