Effect of feed restriction and subsequent re-alimentation on hormones and genes of the somatotropic axis in cattle.
The objective of this study was to characterize the effect of feed restriction and compensatory growth during re-alimentation on the functionality of the somatotropic axis. We blocked 60 bulls into one of two groups: 1) restricted feed allowance for 125 days (period 1) (RES, n = 30) followed by ad libitum feeding for 55 days (period 2) or 2) ad libitum access to feed throughout (ADLIB, n = 30). A growth hormone releasing hormone (GHRH) challenge was performed during each period. At the end of each period, 15 animals from each treatment were slaughtered and hepatic tissue collected. Hepatic expression of 13 genes of the somatotropic axis was measured by qRT-PCR. RES displayed a lower growth rate during period 1 (0.6 vs. 1.9 kg/day; P < 0.001), subsequently gaining more than ADLIB animals during period 2 (2.5 vs. 1.4 kg/day; P < 0.001). Growth hormone response to GHRH was not different between treatments at either time-point (P > 0.05); however, resultant plasma IGF-1 was lower in period 1 and greater in period 2 in RES animals (P < 0.05). Expression of IGFBP2 was higher (P < 0.01) and IGF1 (P < 0.001) and GHRIA (P < 0.05) lower in RES compared with ADLIB during period 1, with no difference evident in period 2 (P > 0.05). Collectively, the results of this study are consistent with uncoupling of the somatotropic axis following feed restriction. However, there is no evidence from this study that the somatotropic axis per se is a significant contributor to compensatory growth.
Animal and Bioscience Research Department, Animal and Grassland Research and Innovation Centre, Teagasc, Dunsany, County Meath, Ireland; University College Dublin School of Agriculture and Food Science, Belfield, Dublin, Ireland; and.
Kate
K
Keogh
Animal and Bioscience Research Department, Animal and Grassland Research and Innovation Centre, Teagasc, Dunsany, County Meath, Ireland;
Sinéad M
SM
Waters
University College Dublin School of Agriculture and Food Science, Belfield, Dublin, Ireland; and.
Alan K
AK
Kelly
Agri-Food and Biosciences Institute, Belfast, Northern Ireland.
Alastair R G
AR
Wylie
Animal and Bioscience Research Department, Animal and Grassland Research and Innovation Centre, Teagasc, Dunsany, County Meath, Ireland; david.kenny@teagasc.ie.
David A
DA
Kenny
D000824:Animal Nutritional Physiological Phenomena / Q000502:physiology*; D000818:Animals; D019540:Area Under Curve; D031204:Caloric Restriction / Q000009:adverse effects / Q000662:veterinary*; D002417:Cattle / Q000254:growth & development*; D019295:Computational Biology; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000096:biosynthesis; D013006:Growth Hormone / Q000097:blood*; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism*; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D012313:RNA / Q000302:isolation & purification; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D013053:Spectrophotometry / Q000662:veterinary
D017931:DNA Primers; D018076:DNA, Complementary; D018971:Insulin-Like Growth Factor Binding Protein 2; D012313:RNA; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone
cattle; compensatory growth; gene expression; somatotropic axis