Animal Science Abstract
Metabolic adaptation and hormonal regulation in young rabbit does during long-term caloric restriction and subsequent compensatory growth
J. M. Rommers1,A, C. Boiti2, G. Brecchia2, R. Meijerhof3, J. P. T. M. Noordhuizen4, E. Decuypere5 and B. Kemp6
APresent address: J.M.Rommers, Animal Sciences Group of Wageningen UR, Marijkeweg 40, 6700 AH Wageningen; e-mail: Jorine.rommers@wur.nl
1Animal Sciences Group of Wageningen University and Research Centre (WUR), Applied Research, 8203 AD Lelystad, The Netherlands2Dipartimento di Scienze Biopatologiche veterinarie, Sezione di Fisiologia, Università di Perugia, 06126 Perugia, Italia
3Hybro, 5830 AA Boxmeer, The Netherlands
4Department of Farm Animal Health, Faculty of Veterinary Medicine, University of Utrecht, The Netherlands
5Laboratory for Physiology and Immunology of Domestic Animals, Department of Animal Science, Catholic University of Leuven, Leuven, Belgium
6Animal Sciences Group of Wageningen University and Research Centre, Department of Animal Sciences, 6700 AH Wageningen, The Netherlands
Abstract
An experiment was performed to assess the metabolic adaptation and hormonal regulation in young female rabbits during long-term food restriction and subsequent compensatory growth during rearing. Feeding level was either ad libitum (AL, no. = 52) or restricted (R, no. = 52). From 6 to 12 weeks of age, food intake of R was kept at a constant level. This resulted in an increase in relative restriction as compared with AL to 0.54of AL intake at 12 weeks of age (restriction period). Thereafter food intake gradually increased to 0.95 of AL at 17 weeks of age (recovery period). During the last 5 days before insemination at 17.5 weeks of age, all animals were fed to appetite. Blood samples were taken weekly from 6 to 17 weeks of age from 11 animals in each group. Growth rate of R was reduced during the restricted period (29 (s.d. 2) v. 44 (s.d. 5) g/day for R and AL, respectively; P < 0.05), but was higher in the recovery period (30 (s.d. 3) v. 27 (s.d. 4) g/day, respectively; P < 0.05). At first insemination, AL rabbits were heavier than R (4202 (s.d. 388) v. 3798 (s.d. 220) g, respectively; P < 0.001). During the restricted period, plasma glucose was constantly lower (P < 0.05) in R. Insulin levels paralleled those of glucose, being lower (P < 0.05) in R than in AL. Restriction reduced (P < 0.05) circulating corticosterone and tri-iodothyronine (T3) levels in R. Leptin, non-esterified fatty acids, and plasma urea nitrogen levels were similar for AL and R during food restriction, whereas triglycerides were similar until 10 weeks of age, after which the levels were lower in R. During the recovery period, the food intake of the R but not AL rabbits increased. Insulin was the only hormone in R rabbits that had returned to levels found in AL rabbits by the 2nd week of the recovery period. Glucose, T3, and corticosterone levels returned to levels found in AL rabbits between 3 to 4 weeks after refeeding. Non-esterified fatty acids, triglycerides, and leptin were higher (P < 0.05) in AL rabbits from 13 weeks of age onwards. The pattern of changes in the endocrine status during food restriction and compensatory growth in rabbits do conform with those from other species, although some specific changes may vary depending on the severity of food restriction and its duration.
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