Cornale, P., Macchi, E., Renna, M., Prola, L., Perona, G., & Mimosi, A. (2016). Effect of Cage Type on Fecal Corticosterone Concentration in Buck Rabbits During the Reproductive Cycle. Journal of Applied Animal Welfare Science, 19(1), 90-96.
Research Question: What are the effects of cage type and stage of reproductive activity on fecal cortisone concentration (FCC) levels in buck rabbits?
Study Sample: Sexually mature Grigio del Monferrato buck rabbits (N = 14) located on a commercial rabbit breeding farm in Buttigliera d’Asti, Italy. All bucks were approximately 6 months of age with a mean body weight of 3,938.4 ± 284.9g at the start of the experiment.
Methodology: To test the effect of cage type on FCC in buck rabbits, the authors examined two different caging scenarios: 1) bucks housed individually in standard-dimension cages (SC); and 2) bucks housed individually in bigger cages (BC) defined as cages with a volume more than double the SCs. Both caging systems were equipped with a plastic foot mat to prevent direct contact with the wire. Buck rabbits were housed in either of the two experimental conditions for a period of four consecutive reproductive cycles. Semen from each buck was collected every 12 days for a total of two ejaculations per buck during the experimental period. Feces were collected at five different phases of the reproductive cycle: 1) before estrous synchronization of doe rabbits housed in the breeding facility; 2) before artificial insemination of the does using the collected semen; 3) before partum; 4) before weaning; and 5) after weaning. For each phase, feces were collected over a 24-hr period and then pooled for each experimental group prior to analysis. FCC was determined using commercially available enzyme immunoassay kits. Note that prior to the start of the experiment, feces were collected from each buck every day for a period of 14 consecutive days to assess intra-individual variability of FCC.
Findings: Results of FCC analyses indicate no statistically significant relationship between cage type and the phase of reproductive activity on the FCC of buck rabbits. While not significant, the FCC of buck rabbits housed in SC tended to be higher compared with the FCC of bucks housed in BC. Similarly, the effect of the reproductive phase on FCC was not significant but FCC tended to be higher during phase 2 (artificial insemination) and phase 5 (post-weaning) compared to all other reproductive phases in both SC and BC housed bucks. The authors suggest that despite a lack of statistically significant findings, the tendency of FCC to be highest around artificial insemination and post-weaning could imply that these two moments are the most critical phases for buck rabbits’ welfare.
Limitations: A primary limitation of this study is the small sample size of buck rabbits (N = 14). The small sample size may have contributed to the lack of statistically significant findings for both the effect of cage type and the effect of reproductive cycle phase on FCC. The authors noted that intra-individual variability in FCC was assessed prior to the experimental period; however, results of these analyses were not reported. It is assumed that the authors chose to pool fecal samples from each treatment condition based on their intra-variability findings or previously validated methods from the literature, but neither of these two justifications were given. Thus, it is possible that the authors’ decision to pool feces from all individuals housed in either of the two treatments affected the statistical significance of their findings.
Summary by Katherine Murtough