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Post-weaning growth performance of heifers grazing Tasmanian native pastures and the estimation of inbreeding levels using random amplied polymorphic DNA markers

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Malau-Aduli, AEO and Dunbabin, M (2007) Post-weaning growth performance of heifers grazing Tasmanian native pastures and the estimation of inbreeding levels using random amplied polymorphic DNA markers. Journal of Animal Science, 85 (Suppl ). p. 370. ISSN 1525-3163

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Abstract

The aims of this study were to evaluate the growth performance of
Hereford, Angus, Hereford × Angus and Hereford × Saler heifers within
the same herd grazing native pastures and to estimate homozygosity
and inbreeding coefcients using random amplied polymorphic DNA
(RAPD) markers. Post-weaning liveweight (BW), average daily gain
(ADG) and body condition score (BCS) on a scale from 0 to 5 were
monitored monthly from 2005 to 2006. Genomic DNA was extracted
from blood samples, amplified using RAPD primers, fragments
resolved by gel electrophoresis and banding patterns elucidated under
UV light. Estimation of homozygosity through band sharing patterns
was utilised in determining within-breed inbreeding levels. Regardless
of breed, LWT, BCS and ADG of heifers followed a typical sigmoid
curve pattern characterised by a decline in average BW from 200 kg
in May to 188 kg in June, a continuous monthly increase through to
March 2006 when it reached a peak (380 kg) before a nal decline to
375 kg in May. The BCS ranged from 1.6 to 3.6 while ADG ranged
from -0.4 to 1.5 kg/d. Significant genetic variation was observed
between the different breeds in that BCS and BW of purebred Angus
heifers were lower than those of purebred Hereford and their crosses
with Angus and Saler. Average BW of the Angus breed ranged from
164-349 kg, with BCS ranging from 1.4 to 3.3 compared to the
Hereford (186-383 kg, 1.6-3.6), Hereford × Angus (192-383 kg,
1.7-3.6) and Hereford × Saler (192-385 kg, 1.6-3.7), respectively. The
ADG of the Angus was not different from those of Hereford and their
crosses indicating that the Angus was perhaps better in terms of feed
efciency since they probably ate less and gained the same weight as
the heavier breeds that must have eaten more commensurate with their
maintenance requirements. The strongest residual correlation (r=0.98)
was between BW and BCS. Average band sharing frequencies ranged
from 0.60 in the crossbreds to 0.96 in the purebreds with estimated
inbreeding coefcients ranging from 0.5% to 3%, respectively, which
is very low.

Item Type: Article
Keywords: RAPD Markers, Post-weaning Growth, Beef Cattle
Journal or Publication Title: Journal of Animal Science
Page Range: p. 370
ISSN: 1525-3163
Identification Number - DOI: 400
Date Deposited: 04 Jan 2008 00:57
Last Modified: 18 Nov 2014 03:26
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