New Zealand Journal of Agricultural Research abstracts
Genetic parameters for growth, puberty, and beef cow reproductive traits in a
puberty selection experiment
C. A. MORRIS
J. A. WILSON
AgResearch
Ruakura Agricultural Research Centre
Private Bag 3123
Hamilton, New Zealand
G. L. BENNETT
USDA-ARS
US Meat Animal Research Center
P.O. Box 166
Clay Center
Nebraska 68933-0166, USA
N. G. CULLEN
S. M. HICKEY
J. C. HUNTER
AgResearch
Ruakura Agricultural Research Centre
Private Bag 3123
Hamilton, New Zealand
Abstract A selection experiment to change reproductive traits
in Angus cattle has been maintained for 14 years, with first calvings in 1985.
Alongside an unselected control line, three lines were established, selected
for increased age at puberty in heifers (AGE+ line), reduced age at puberty
in heifers (AGE- line), or increased scrotal circumference (SC line). The last
two lines were merged at the 1992 matings, with the revised objective of applying
further selection in both sexes to reduce age at puberty in heifers. Dates at
puberty in heifers from an average of 8 to 16 months of age and SC in bulls
were recorded in all lines, along with the pregnancy rates (PR) and subsequent
calving dates (CD) in heifers and all cow-age groups. Heritabilities of single-record
SC, standardised age at first behavioural oestrus (SFO), and single-record CD
were 0.41 ± 0.04 (repeatability 0.70 ± 0.01), 0.27 ± 0.04,
and 0.09 ± 0.04 (repeatability 0.19 ± 0.03), respectively.
Genetic correlations of SC with SFO and CD were -0.25 ± 0.09 and -0.23 ±
0.15, respectively; SFO with CD 0.57 ± 0.17; and PR with SFO and SC -0.36
± 0.13 and 0.12 ± 0.11, respectively. The selection-line difference in PR
over seven years (AGE- mean minus AGE+ mean), excluding yearling heifer matings,
was 4.7 ± 2.1% (P < 0.05). Mean CD in the AGE- line was 3 days earlier
than in the AGE+ line (P < 0.09). These correlation and selection-line
results suggest that selecting for higher SC and earlier heifer puberty leads
to earlier CD and higher PR.
Keywords Angus; puberty; genetics; correlation;
reproduction
New Zealand Journal of Agricultural Research, 2000, Vol. 43: 83-91
0028-8233/00/4301-00 83 $7.00/0 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (727K); (scanned from paper original: notes about this process)
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