The ontogeny of serum insulin-like growth factor-I concentration in foals: Effects of dam parity,diet, and age at weaning |
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| Institution: | 1. Department of Veterinary Medicine, University “Aldo Moro” of Bari, 70010 Valenzano, Italy;2. IFCE, Plateau Technique de la Station Expérimentale, 1 Impasse des Haras, 19370, Hamberet, France;1. Department of Veterinary Science, University of Pisa, Pisa, Italy;2. Interdepartmental Centre for Agricultural and Environmental Research “E. Avanzi”, University of Pisa, Pisa, Italy;3. Interdepartmental Research Center Nutrafood “Nutraceuticals and Food for Health”, University of Pisa, Pisa, Italy;1. Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA;2. Department of Animal Science, University of California, Davis, CA, 95616, USA;1. William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis CA;2. Department of Medicine and Epidemiology School of Veterinary Medicine, University of California, Davis, CA;3. Department of Pathology, Microbiology, and Immunology School of Veterinary Medicine, University of California, Davis, CA;4. Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA;1. Research Platform Bioactive Microbial Metabolites (BiMM), Bioresources and Technologies Campus Tulln, Konrad Lorenz Straße 24, 3430 Tulln, Austria;2. Institute of Milk Hygiene, Milk Technology and Food Science, Department of Farm Animal and Veterinary Public Health, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria;3. University Clinic for Ruminants, Clinical Unit for Herd Health Management in Ruminants, Department for Farm Animals and Veterinary Public Health, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria;4. Institute of Physiology, Pathophysiology and Biophysics, Department of Biomedical Sciences, Vetmeduni Vienna, Veterinärplatz 1, 1210 Vienna, Austria;5. Fungal Genetics and Genomics Unit, Department of Applied Genetics and Cell Biology, BOKU University of Natural Resources and Life Sciences Vienna, Konrad Lorenz Straße 24, 3430 Tulln, Austria |
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| Abstract: | The effects of dam parity, age at weaning, and preweaning diet were examined in the ontogeny of serum insulin-like growth factor-I (IGF-I) concentrations in foals. Foals born to 13 primiparous and 19 multiparous draft-cross mares were weighed and bled near birth. About one-half of the foals in each group were weaned early (about 13 wk old); the remaining foals were weaned late (about 16 wk of age). Pooled values for serum IGF-I concentrations between birth and 17 wk of age were higher (P < 0.065) for foals born to multiparous (386 ng/ml) than to primiparous mares (237.5 ng/ml). Colts (378 ng/ml) had higher (P < 0.05) serum IGF-I concentrations than fillies (254.5 ng/ml), regardless of dam parity. Colts (173.5 kg) also tended (P = 0.12) to be heavier than fillies (159.2 kg). Weaning, whether at 13 or 16 wk of age, reduced (P < 0.05) growth rates and serum IGF-I concentrations. Serum IGF-I values recovered to preweaning values within 1–3 wk postweaning concurrent to an improved weight gain. Fifteen 1-d-old foals in a second study were fed milk replacer for 7 wk and were compared with five foals that nursed their mares for 8 wk. During the first 2 wk, replacer-fed foals (0.46 kg/d) did not gain as rapidly (P < 0.03) as mare-nursed foals (1.73 kg/d). The associated serum IGF-I values for replacer foals (139.4 ng/ml) were lower (P < 0.0001) than values for mare-nursed foals (317.4 ng/ml). Despite similarity in gains for both groups thereafter, serum IGF-I concentrations of replacer-fed foals were only 36 and 60% of values obtained for mare-nursed foals at 8 (weaning) and 18 wk of age, respectively. The intrinsic differences between mare-nursed and milk-replacer foals in serum IGF-I concentrations persisted to 1 yr of age despite similarities in dietary management and body weight of the foals. At 1 yr of age, the serum IGF-I concentration of mare-nursed foals (1,203 ng/ml) was 48% higher than that of replacer-fed foals (815 ng/ml). These data indicate that dam parity, sex of foal, and preweaning nutrition affect the ontogeny of serum IGF-I concentration in the foal. The chronic, persistent difference in serum IGF-I values created by the early nutritional management of growing animals has implications in the interpretation of longitudinal serum IGF-I studies in all species. |
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