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| Responses of sheep to annual cycles in nutrition .1. Role of endogenous growth hormone during undernutrition |
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| Author(s): Adams NR, Briegel JR, Rigby RDG, Sanders MR, Hoskinson RM |
| Source: ANIMAL SCIENCE Volume: 62 Pages: 279-286 Part: Part 2 Published: APR 1996 |
| Times Cited: 13 References: 30 |
| Abstract: Plasma concentrations of growth hormone (GH) are elevated ill sheep during undernutrition. The present study attempted to determine whether this increased secretion mediated nutritional effects on reproduction or wool growth, using sheep immunized against growth hormone-releasing hormone and given a low-quality, sub-maintenance diet. Immunized reduced plasma concentrations of GH at all times measured (P < 0.01), through reduced pulse frequency, reduced pulse amplitude, and reduced baseline concentrations. Plasma insulin-like growth factor-1 (IGF-1) was also reduced in the immunized sheep (P < 0.01). Despite this, rates of live-weight loss and wool growth were similar in immunized and control ewes. Plasma concentrations of LH and FSH were also similar in immunized and control ewes, both during the late luteal phase and after ovariectomy and supplementation with oestradiol and progesterone. Numbers of ovarian follicles and corpora lutea were also unaffected by immunization. It is concluded that high endogenous concentrations of GH in sheep given food below maintenance are necessary to maintain plasma IGF-1, but do not affect the concentration of gonadotropins or ovarian follicular growth. Furthermore, rates of live-weight loss and the depression in wool growth in such animals were also independent of concentrations of GH or IGF-1. |
| Document Type: Article |
| Language: English |
| Reprint Address: Adams, NR (reprint author), CSIRO, DIV ANIM PROD, WEMBLY, WA 6014 AUSTRALIA |
Addresses:
1. CSIRO, DIV ANIM PROD, BLACKTOWN, NSW 2148 AUSTRALIA |
| Publisher: DURRANT PERIODICALS, WINTON LEA PENCAITLAND, EAST LOTHIAN, SCOTLAND EH34 5AY |
| Subject Category: Agriculture, Dairy & Animal Science |
| IDS Number: UE804 |
| ISSN: 1357-7298 |
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