Reduced air changes per hour in IVCs and the impact on breeding performance

摘要

The fifty air changes per hour (ACH) setting of IVCs in combination with a "bedding-only" change procedure every two weeks and over a period of 26 weeks has been previously shown to affect negatively the Production Efficiency Index (P.E.I) in C57BI/6trios when the air is injected from the rear bottom of the cage. This reduction in the P.E.I is not detectable when the number of air changes per hour is set a 75 and the air is injected from the rear top of the cage. To determine whether the impact on breeding performances in C57BI/6 trios is due to the lower number of air changes per hour, the point of injection or a combination of the two conditions, we compared the performances of two IVC systems. The first is pre-set at 50 ACH and with the air injected in the cage from the rear bottom, the second normally operating at 75 ACH and with the air injected from the rear top of the cage, was set at 50ACH in order to work in a comparable quantitative condition in terms of air changes, the main differencebeing the point of air injection. In b oth systems the P.E.I was reduced and comparable with our previous findings, indicating that 50 ACH are not suitable when cage cleaning is accomplished only by changing the bedding. In addition, the number of litters cannibalised in the system with the air injected into the cage from the rear bottom was 35% higher and the body weight at weaning of both males and females was significantly lower (p<0.0001). These findings strongly suggest that there is a lack of flexibility when IVCs are set at 50ACH and injected into the cage from the rear bottom. While there appear to be no great differences between the two systems in terms of pups weaned per female per week, the impact on body weight at weaning and increased cannibalism of pups in the system where air is injected at animal level certainly require further investigation.