Effect of feed restriction on serum somatotropin, insulin-like growth factor-I-(IGF-I) and IGF binding proteins in cyclic heifers actively immunized against growth hormone releasing factor
| Autor: | R. W. Harvey, Jeffrey D. Armstrong, W. S. Cohick, Robert M. Campbell, E. P. Heimer |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
medicine.medical_specialty
medicine.medical_treatment Fatty Acids Nonesterified Biology Growth Hormone-Releasing Hormone Random Allocation Insulin-like growth factor Endocrinology NEFA Estrus Food Animals Somatomedins Internal medicine medicine Animals Insulin Insulin-Like Growth Factor I Growth factor Vaccination IGF-Binding Proteins Human serum albumin Insulin-Like Growth Factor Binding Protein 2 Dietary treatment Growth Hormone Growth Hormone-Releasing Factor Cattle Electrophoresis Polyacrylamide Gel Female Animal Science and Zoology Carrier Proteins Food Deprivation medicine.drug |
| Zdroj: | Domestic Animal Endocrinology. 10:315-324 |
| ISSN: | 0739-7240 |
| DOI: | 10.1016/0739-7240(93)90035-a |
| Popis: | Feed restriction often increases serum somatotropin (ST) and decreases insulin-like growth factor-I (IGF-I) in ruminants; however, the mechanisms responsible for this change in ST and IGF-I are not well defined. We investigated the effects of feed restriction on serum ST, IGF-I, IGF binding proteins (IGFBP), insulin and nonesterified fatty acids (NEFA) in cyclic Angus and Charolais heifers (n = 15) previously immunized against growth hormone releasing factor (GRFi) or human serum albumin (HSAi). Cows were fed a concentrate diet ad libitum (AL) or were restricted to 2 kg cotton seed hulls (R) for 4 d. Each heifer received each dietary treatment in a single reversal design. As anticipated, GRFi decreased ST, IGF-I and insulin (P.05). In addition, GRFi decreased serum IGFBP-3 (P.01), but increased IGFBP-2 (P.01). Feed restriction resulted in an increase in serum ST in HSAi, but not in GRFi heifers. Regardless of immunization treatment, feed restriction decreased serum IGF-I and insulin, and increased NEFA (P.01). In conclusion, the increase in serum ST levels observed during feed restriction was blocked by active immunization against GRF. However, feed restriction resulted in decreased serum IGF-I in GRFi heifers in spite of initial low levels of IGF-I (due to GRFi). Although GRFi decreased levels of IGFBP-3 and increased levels of IGFBP-2, feed restriction for 4 d did not alter serum IGFBP. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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