Responses of wool growth rate and body reserves to nutrition in Merino ewes: a potential biological link between production and fitness
N. R. Adams A , J. R. Briegel A C and J. C. Greeff BA CSIRO Livestock Industries and Australian Sheep Industry CRC, PO Wembley, WA 6913, Australia.
B Western Australian Department of Agriculture and Food and Australian Sheep Industry CRC, GSARI, Katanning, WA 6317, Australia.
C Corresponding author. Email: Jan.Briegel@csiro.au
Australian Journal of Agricultural Research 58(9) 913-920 https://doi.org/10.1071/AR06386
Submitted: 6 December 2006 Accepted: 14 May 2007 Published: 28 September 2007
Abstract
This study examined whether the low body-fat reserves in sheep with high estimated breeding values (EBVs) for clean fleece weight (CFW) reported previously are affected by nutritional history, and second whether the effect may be related to differences in the variation in fibre diameter (CVfd). Groups of 11 20-month-old Merino ewes with high and low EBVs for CFW and for CVfd were compared in a 2 × 2 design at low bodyweight, then fed ad libitum for 100 days and re-measured. The response of wool growth rate to feed supply (WRF) was estimated as the slope of the regression against time of clean wool mass collected from mid-side patches at intervals of 30–40 days throughout the experiment. High CFW sheep had greater feed intake relative to liveweight and liveweight gain (P = 0.02), but did not differ significantly in other characteristics from low CFW sheep. High CVfd sheep had lower plasma concentrations of insulin (P = 0.02), IGF-1 (P = 0.03), and albumin (P = 0.02) throughout the study, and had less fat when in poor body condition (P = 0.02). The WRF was greater in both the high CFW (P = 0.003) and the high CVfd (P = 0.004) genotypes. When studied in poor body condition, sheep with a high WRF had lower liveweight (P < 0.001), lower body condition score (P < 0.001), lower plasma albumin (P < 0.001), and higher plasma growth hormone (P = 0.02), but these relationships weakened or disappeared after ad libitum feeding. Sheep with high WRF also had lower plasma concentrations of insulin (P = 0.002) and IGF-1 (P = 0.008) throughout the study, which may have brought about the increased responsiveness of protein and energy metabolism to nutrition. The results indicate that genetic selection for wool characteristics can affect the responsiveness of wool growth rate to nutrient supply. Sheep that are highly responsive grow more wool when offered abundant feed, but may have lower body nutrient reserves when on limited feed.
Additional keywords: lean, environment, reproduction.
Acknowledgments
Support for this work was received from Meat and Livestock Australia. We also thank G. Cox for preparing the sheep, S. Liu for assistance and advice with deuterium measurement, E. Bermingham, M. Carthew, and M. Ferguson for help during the study, F. Bush for assistance with wool measurements, and the CSIRO team at Floreat for helping with blood sampling.
Adams NR,
Briegel JR, Blache D
(2002) Feed intake, liveweight and wool growth rate in Merino sheep with different responsiveness to low- and high-quality feed. Australian Journal of Experimental Agriculture 42, 399–405.
| Crossref | GoogleScholarGoogle Scholar |
Adams NR,
Briegel JR,
Greeff JC, Bermingham EN
(2006) Feed intake, body composition, and plasma metabolic hormones in Merino sheep that differ genetically in fleece weight or fibre diameter. Australian Journal of Agricultural Research 57, 27–32.
| Crossref | GoogleScholarGoogle Scholar |
Adams NR,
Briegel JR,
Rigby RDG,
Sanders MR, Hoskinson RM
(1996) Responses of sheep to annual cycles in nutrition. 1. Role of endogenous growth hormone during undernutrition. Animal Science 62, 279–286.
Adams NR,
Briegel JR, Ritchie AJM
(1997) Wool and liveweight responses to nutrition by Merino sheep genetically selected for high or low staple strength. Australian Journal of Agricultural Research 48, 1129–1137.
| Crossref | GoogleScholarGoogle Scholar |
Adams NR,
Briegel JR,
Thompson MJ, Sammels LM
(2000) Metabolic hormones and tissue concentrations of mRNA for IGF-1 in lines of sheep that differ in their protein synthesis response to feed intake. Journal of Endocrinology 167, 315–320.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Adams NR,
Liu SM,
Briegel JR, Thompson MJ
(2004) Plasma insulin concentrations and amino acid turnover in Merino sheep with high or low fleece weight. Australian Journal of Agricultural Research 55, 833–838.
| Crossref | GoogleScholarGoogle Scholar |
Brier BH,
Gallaher BW, Gluckman PD
(1991) Radioimmunoassay for insulin-like growth factor-1: solutions to some potential problems and pitfalls. Journal of Endocrinology 128, 347–357.
| PubMed |
Greeff JC
(2001) Can along and between fibre diameter variation make a contribution in Merino breeding programs? Proceedings of the Association for the Advancement of Animal Breeding and Genetics 14, 293–296.
Greeff JC
(2005) Merino strains with high wool production have lower lifetime reproduction rates. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 16, 16–19.
Greeff JC, Cox G
(2006) Genetic changes generated within the Katanning Merino Resource Flocks. Australian Journal of Experimental Agriculture 46, 803–808.
| Crossref | GoogleScholarGoogle Scholar |
Greeff JC,
Cox G,
Butler L, Dowling M
(2005) Genetic relationships between carcass quality and wool production traits in Australian Merino rams. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 16, 12–15.
Greeff JC,
Davidson R, Skerritt JW
(2003) Genetic relationships between carcass quality and wool production traits in Australian Merino rams. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 15, 330–333.
Huisman AE, Brown DJ
(2005) Genetic parameters for ultrasound scan and wool traits at yearling and hogget age in Merino sheep. Proceedings of the Association for the Advancement of Animal Breeding and Genetics 16, 32–35.
Hynd PI,
Hughes A,
Earl CR, Penno NM
(1997) Seasonal changes in the morphology of wool follicles in Finewool and Strongwool Merino strains grazing at different stocking rates in southern Australia. Australian Journal of Agricultural Research 48, 1089–1097.
| Crossref | GoogleScholarGoogle Scholar |
Kadarmideen HN
(2004) Genetic correlations among body condition score, somatic cell score, milk production, fertility and conformation traits in dairy cows. Animal Science 79, 191–201.
Knap PW
(2005) Breeding robust pigs. Australian Journal of Experimental Agriculture 45, 763–773.
| Crossref | GoogleScholarGoogle Scholar |
Lambe NR,
Simm G,
Young MJ,
Conington J, Brotherstone SH
(2004) Seasonal changes in tissue weights in Scottish Blackface ewes over multiple production cycles. Animal Science 79, 373–385.
Lewer RP,
Woolaston RR, Howe RR
(1992) Studies on Western Australian Merino sheep. I. Stud, strain and environmental effects on hogget performance. Australian Journal of Agricultural Research 43, 1381–1397.
| Crossref | GoogleScholarGoogle Scholar |
McCann JP,
Loo SC,
Aalseth DL, Abribat T
(1997) Differential effects of GH stimulation on fasting and prandial metabolism and plasma IGFs and IGF-binding proteins in lean and obese sheep. Journal of Endocrinology 154, 329–346.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Rauw WM,
Kanis E,
Noordhuizen-Stassen EN, Grommers FJ
(1998) Undesirable side effects of selection for high production efficiency in farm animals: a review. Livestock Production Science 56, 15–33.
| Crossref | GoogleScholarGoogle Scholar |
Russel AJF,
Doney JM, Gunn RG
(1969) Subjective assessment of body fat in live sheep. Journal of Agricultural Science, Cambridge 72, 451–454.
Safari E,
Fogarty NM, Gilmour AR
(2005) A review of genetic parameter estimates for wool, growth, meat and reproduction traits in sheep. Livestock Production Science 92, 271–289.
| Crossref | GoogleScholarGoogle Scholar |
Schlink AC,
Mata G,
Lea J, Ritchie AJM
(1999) Seasonal variation in fibre diameter and length in wool of grazing Merino sheep with low or high staple strength. Australian Journal of Experimental Agriculture 39, 507–517.
| Crossref | GoogleScholarGoogle Scholar |
Searle TW
(1970) Body composition in lambs and young sheep and its prediction in vivo from tritiated water space and body weight. Journal of Agricultural Science, Cambridge 74, 357–362.
Thompson MJ,
Briegel JR,
Thompson AN, Adams NR
(2006) Differences in survival and neonatal metabolism in lambs from flocks selected for or against staple strength. Australian Journal of Agricultural Research 57, 1221–1228.
| Crossref | GoogleScholarGoogle Scholar |
Williams AJ
(1964) The effect of daily photoperiod on wool growth of Merino rams subjected to unrestricted and restricted feeding regimes. Australian Journal of Experimental Agriculture and Animal Husbandry 4, 124–128.
| Crossref | GoogleScholarGoogle Scholar |
Yang D,
Diraison F,
Beylot M,
Brunengraber DZ,
Samols MA,
Anderson VE, Brunengraber H
(1998) Assay of low deuterium enrichment of water by isotopic exchange with [U-13C3]acetone and gas chromatography-mass spectrometry. Analytical Biochemistry 258, 315–321.
| Crossref | GoogleScholarGoogle Scholar | PubMed |
Young VR,
Marchini JS, Cortiella J
(1990) Assessment of protein status. Journal of Nutrition 120, 1496–1502.
| PubMed |
