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Domestic Animal Endocrinology
Gootwine, E., Institute of Animal Science, ARO, Volcani Center, Bet Dagan 50250, Israel, Institute of Animal Science, ARO, Volcani Center, POB 6, Bet Dagan 50250, Israel
Suttie, J.M., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
McEwan, J.C., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
Veenvliet, B.A., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
Littlejohn, R.P., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
Fennessy, P.F., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
Montgomery, G.W., AgResearch Molecular Biology Unit, Department of Biochemistry, Center for Gene Research, PO Box 56, Dunedin, New Zealand
The effects of natural variation in the number of copies of the growth hormone (GH) gene on growth parameters, plasma GH profiles, and the response to GHRH challenge were compared in Coopworth ram lambs from selection lines differing in body composition and GH levels. Different genotypes at the GH locus carried two, three, or four copies of the GH gene and GH secretion was studied under ad libitum feeding conditions and in the fasted state. There were no significant effects of GH genotype on any parameters of growth or body composition. Basal serum GH concentration, GH pulse frequency, and GH pulse amplitude differed significantly with selection line and fasting, but did not differ significantly between the GH genotypes. Significant differences of subtle nature were found between the GH genotypes in their responsiveness to GHRH. For the ad libitum-fed Lean selection line animals, the first GHRH challenge resulted in a higher mean maximum response for GH1/GH1 than GH2/GH2 (P < 0.05). Between the first and the second challenges there was a decrease in maximum response for the GH1/GH1 genotype and an increase for the GH2/GH2 genotype (P < 0.05 for GH genotype main effect). The differences between GH genotypes in response to GHRH challenge suggest that polymorphism in the number of GH gene copies in sheep may have physiological implications for the function of the GH axis, which may be manifested in growing lambs only under specific genotype-environment combinations.
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The physiological effects of natural variation in growth hormone gene copy number in ram lambs
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Gootwine, E., Institute of Animal Science, ARO, Volcani Center, Bet Dagan 50250, Israel, Institute of Animal Science, ARO, Volcani Center, POB 6, Bet Dagan 50250, Israel
Suttie, J.M., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
McEwan, J.C., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
Veenvliet, B.A., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
Littlejohn, R.P., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
Fennessy, P.F., AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand
Montgomery, G.W., AgResearch Molecular Biology Unit, Department of Biochemistry, Center for Gene Research, PO Box 56, Dunedin, New Zealand
The physiological effects of natural variation in growth hormone gene copy number in ram lambs
The effects of natural variation in the number of copies of the growth hormone (GH) gene on growth parameters, plasma GH profiles, and the response to GHRH challenge were compared in Coopworth ram lambs from selection lines differing in body composition and GH levels. Different genotypes at the GH locus carried two, three, or four copies of the GH gene and GH secretion was studied under ad libitum feeding conditions and in the fasted state. There were no significant effects of GH genotype on any parameters of growth or body composition. Basal serum GH concentration, GH pulse frequency, and GH pulse amplitude differed significantly with selection line and fasting, but did not differ significantly between the GH genotypes. Significant differences of subtle nature were found between the GH genotypes in their responsiveness to GHRH. For the ad libitum-fed Lean selection line animals, the first GHRH challenge resulted in a higher mean maximum response for GH1/GH1 than GH2/GH2 (P < 0.05). Between the first and the second challenges there was a decrease in maximum response for the GH1/GH1 genotype and an increase for the GH2/GH2 genotype (P < 0.05 for GH genotype main effect). The differences between GH genotypes in response to GHRH challenge suggest that polymorphism in the number of GH gene copies in sheep may have physiological implications for the function of the GH axis, which may be manifested in growing lambs only under specific genotype-environment combinations.
Scientific Publication
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