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Title: Sheep of divergent genetic merit for wool growth do not differ in digesta kinetics while on restricted intakes
Contributor(s): de Barbieri Etcheberry, Luis (author); Hegarty, Roger  (author); Oddy, Hutton  (author)orcid ; Barnett, Mark  (author)orcid ; Li, Li (author); Nolan, John V  (author)orcid 
Publication Date: 2014
DOI: 10.1071/an14319
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Abstract: Sheep selected for high wool growth were previously shown to exhibit higher microbial protein outflow from the rumen and higher uptake of amino nitrogen in portal blood than those selected for low wool growth. This suggests that genetic selection for wool growth may induce changes in foregut physiology. This study was undertaken to determine whether differences in digesta kinetics, especially mean retention mime (MRT), are associated with differences in fleece production between sheep with low or high estimated breeding values (EBVs) for fleece weight. Twenty mature Merino wethers with uniform EBVs for liveweight were allocated to two groups of 10 animals on the basis of high or low EBVs for yearling fleece weight. Five sheep with low-EBVs and five sheep with high-EBVs for fleece weight groups were allocated in a crossover design to low and high feeding-level treatments, which comprised a blended hay diet fed at maintenance or 1.5 times maintenance. All sheep were given single doses of chromium-mordanted fibre and cobalt-EDTA as inert, non-digestible markers. Digesta kinetics was determined by analysis of the faecal marker excretion patterns using a compartmental model. Higher feed intakes from animals fed 1.5 times maintenance were associated with higher rates of wool growth and higher masses of indigestible fibre in the gut, but reduced MRT of digesta. Although sheep with higher EBVs for fleece weight had higher wool growth rates, there was no indication that these wool growth differences were associated with differences in digesta kinetics. The lack of interaction between feeding level and genotype suggests that MRT did not contribute to genotype differences in wool growth in sheep fed restricted intakes. The differences in wool growth among commercial Merino sheep with divergent fleece weight EBVs achieved by multi-trait selection are not attributable to differences in digesta kinetics, at least when feed is not available 'ad libitum'.
Publication Type: Journal Article
Source of Publication: Animal Production Science, 54(9), p. 1243-1247
Publisher: CSIRO Publishing
Place of Publication: Australia
ISSN: 1836-5787
Fields of Research (FoR) 2008: 070204 Animal Nutrition
070201 Animal Breeding
070202 Animal Growth and Development
Fields of Research (FoR) 2020: 300303 Animal nutrition
300305 Animal reproduction and breeding
300301 Animal growth and development
Socio-Economic Objective (SEO) 2008: 830310 Sheep - Meat
970106 Expanding Knowledge in the Biological Sciences
830311 Sheep - Wool
Socio-Economic Objective (SEO) 2020: 100412 Sheep for meat
280102 Expanding knowledge in the biological sciences
100413 Sheep for wool
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
Appears in Collections:Journal Article

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