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Growth hormone pulsatility in ram lambs of genotypes selected for fatness or leanness

  • J. M. Suttie (a1), B. A. Veenvliet (a1), R. P. Littlejohn (a1), P. D. Gluckman (a2), I. D. Corson (a1) and P. F. Fennessy (a1)...

Abstract

Although it is known that growth hormone (GH) influences body composition in ruminants, the precise role of the pattern of GH secretion is not known. We have studied the pulsatile release of GH and insulin-like growth factor 1 (IGF 1) secretion in the male progeny of rams from lines selected either for {fat genotype) or against (lean genotype) fatness. Seventy-two lambs (36 each of the fat and lean genotype) were kept on high-quality pasture and randomly allocated within genotype to treatment at 2, 3, 3·5, 4,5 or 6 months of age. The procedure, which was identical for each sampling period, was to sample each lamb through a jugular cannula every 10 min for 6 h, and then, following an overnight fast, to slaughter and analyse the carcass for fat. All blood samples were analysed for GH and samples taken each hour for total plasma IGF 1. The GH data were further analysed with the pulse detection routine PULSAR. Carcass fatness, adjusted for cold carcass weight, was greater for fat genotype animals than for the lean genotype. GH was pulsatile in all profiles but the pattern differed with time and genotype. Mean GH and pulse amplitude decreased with time but did not differ between genotype, although the lean genotype had higher mean GH at five of the six sampling periods. In contrast, GH pulse frequency and IGF 1 were significantly higher for the fat compared with the lean genotype lambs. GH mean and amplitude correlated negatively with carcass fatness in both genotypes and GH pulse frequency and total IGF 1 correlated positively with fatness for the lean genotype only. When carcass weight and genotype were fitted to these relationships, GH mean and total IGF 1 were found to have independent negative and positive effects, respectively, on carcass fatness. Because GH mean had a separate effect on fatness independent of genotype or cold carcass weight, it is likely that GH secretion influences composition by the same basic mechanism in both genotypes. However, although the slopes of these relationships did not differ significantly between the genotypes, the intercepts were significantly different indicating that over and above the basic mechanism, at any level of GH, the lean genotype lambs were leaner than the fat genotype lambs. This may indicate a measure ofGH resistance in the fat genotype lambs.

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Breier, B. H., Gluckman, P. D. and Bass, J. J. 1988. Plasma concentrations of insulin-like growth factor 1 and insulin in the infant calf: ontogeny and influence of altered nutrition. Journal of Endocrinology 119:4350.
Davis, S. L. and Borger, M. L. 1974. Dynamic changes in plasma prolactin luteinizing hormone and growth hormone in ovariectomised ewes, journal of Animal Science 38: 795802.
Davis, S. L., Hossner, K. L. and Ohlson, D. L. 1984. Endocrine regulation of growth in ruminants. In Manipulation of growth in farm animals (ed. Roche, J. F. and D., O'Callaghan), pp. 151178. Martinus Nijhoff, The Hague.
Fennessy, P. F., Greer, G. J. and Bain, W. E. 1987. Selection to change carcass fatness in sheep. Proceedings of the fourth Australasian Association for the Study of Animal Production Conference, p. 382.
Forbes, J. M., Driver, P. M., Brown, W. B., Scanes, C. G. and Hart, I. C. 1979. The effect of daylength on the growth of lambs. 2. Blood concentrations of growth hormone, prolactin, insulin and thyroxine, and the effect of feeding. Animal Production 29:4351.
Frohman, L. A., Downs, T. R., Clarke, I. J. and Thomas, G. B. 1990. Measurement of growth hormone-releasing hormone and somatostatin in hypothalamic-portal plasma of unanesthetized sheep — spontaneous secretion and response to insulin-induced hypoglycaemia. Journal of Clinical Investigation 86: 1724.
Gluckman, P. D., Breier, B. H. and Davis, S. R. 1987. Physiology of the somatotrophic axis with particular reference to the ruminant. Journal of Dairy Science 70: 442466.
Gluckman, P. D. and Butler, J. H. 1983. Parturition related changes in insulin-like growth factors I and II in the perinatal lamb. Journal of Endocrinology 99: 223232.
Gluckman, P. D., Mueller, P. L., Kaplan, S. L., Rudolph, A. M. and Grumbach, M. M. 1979. Hormone ontogeny in the ovine fetus. 1. Circulating growth hormone in mid and late gestation. Endocrinology 104:162168.
Klindt, J., Jenkins, T. G. and Leymaster, K. A. 1985a. Relationships between some estimates of growth hormone and prolactin secretion and rates of accretion of constituents of body gain in rams. Animal Production 41:103111.
Klindt, J., Ohlson, D. L., Davis, S. L. and Schanbacher, B. D. 1985b. Ontogeny of growth hormone, prolactin, luteinizing hormone, and testosterone secretory patterns in the ram. Biology of Reproduction 33: 436444.
Lord, E. A., Fennessy, P. F. and Littlejohn, R. P. 1988. Comparison of genotype and nutritional effects on body and carcass characteristics of lambs. New Zealand Journal of Agricultural Research 31:1319.
Merriam, G. R. and Wachter, K. W. 1982. Algorithms for the study of episodic hormone secretion. American Journal of Physiology 243: E310–E318.
Suttie, J. M, Lord, E. A., Gluckman, P. D., Fennessy, P. F. and Littlejohn, R. P. 1991. Genetically lean and fat sheep differ in their growth hormone response to growth hormone releasing hormone. Domestic Animal Endocrinology 8: 323329.
Suttie, J. M., Veenvliet, B. A., Littlejohn, R. P., Corson, I. D., Fennessy, P. F. and a 1988. Growth hormone pulsatility in relation to carcass composition in ram lambs of two genotypes. Proceedings of the eighth international congress of endocrinology, Kyoto, Japan, abstr. 02–21–137.
Tannenbaum, G. S. and Ling, N. 1984. The interrelationship of growth hormone (GH) releasing factor and somatostatin in generation of the ultradian rhythm of GH secretion. Endocrinology 115:19521957.
Thomas, G. B., Cummins, J. T., Francis, H., Sudbury, A. W., McCloud, P. I. and Clarke, I. J. 1991. Effect of restricted feeding on the relationship between hypophyseal portal concentrations of growth hormone (GH)-releasing factor and somatostatin and jugular concentrations of GH in ovariectomised ewes. Endocrinology 128:11511158.
Trenkle, A. 1977. Changes in growth hormone status related to body weight of growing cattle. Growth 41: 241247.
Trenkle, A. and Topel, D. G. 1978. Relationships of some endocrine measurements to growth and carcass composition of cattle. Journal of Animal Science 46:16041609.
Verde, L. S. and Trenkle, A. 1987. Concentrations of hormones in plasma from cattle with different growth no. potentials. Journal of Animal Science 64:426432.

Keywords

Growth hormone pulsatility in ram lambs of genotypes selected for fatness or leanness

  • J. M. Suttie (a1), B. A. Veenvliet (a1), R. P. Littlejohn (a1), P. D. Gluckman (a2), I. D. Corson (a1) and P. F. Fennessy (a1)...

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