Pedigree and performance data of a well-documented ostrich breeding
resource flock was used to (1) investigate the flock structure, (2) estimate variance
and (co)variance components for egg and day-old chick weight (individual traits), (3)
estimate genetic and environmental parameters for egg and chick production, mean
egg and day-old chick weights and hatchability within breeding seasons (hen traits)
and (4) investigate early identification of superior animals using random regression
models for repeated measures (longitudinal) data over years.
The average level of pedigree completeness of 40 074 birds of a pair-breeding
ostrich flock maintained from 1978 to 2005 at the Oudtshoorn Research Farm, South
Africa was high (99.3%) in the first generation and the average level of inbreeding (F)
was low at 0.51%. The estimated measures of variability were: effective genome
equivalents = 47.3, effective number of founders = 59 and the effective number of
ancestors = 58. The numbers of ancestors responsible for 100%, 50% and 20% of the
variation in the reference population (birds with both parents known), were equal to
254, 21 and 6 respectively. The generation interval in years calculated as the average
age of parents when their offspring which were kept for reproduction were born,
amounted to 7.72 ± 4.79 years. The linear regressions of rate of inbreeding on year of
hatch for the two distinct periods, 1995-2002 and 2003-2005, were 0.08% and -0.07
% per year respectively. The estimate of effective population size (Ne) computed via
the increase in the individual rate of inbreeding was 112.7 animals. The results of this
study indicated that the population under study was at an acceptable level of genetic
variability.
Pedigree and performance data for 71 147 individual egg records collected
between 1991 to 2005 were used to estimate genetic parameters for egg weight
(EWT), live day-old chick weight (CWT) and hatchability (H). Heritability estimates
(±SE) were 0.12 ± 0.02, 0.14 ± 0.04 and 0.09 ± 0.04 for EWT, CWT and H.
Corresponding estimates for maternal genetic effects were 0.27 ± 0.08, 0.38 ± 0.08
and 0.13 ± 0.02. The effects of common environment, permanent environment and
breeding paddock were significant but relatively low for all traits. Egg weight and
CWT were highly correlated at all levels, while H was mostly independent of the weight traits. These results indicated that genetic improvement in these traits would
be feasible.
Data involving monthly records of egg production (EP), chick production
(CP), hatchability (H), mean egg weight (MEW) and mean day-old chick weight
(MCW) were analysed as hen traits. Heritability estimates amounted to 0.04 ± 0.02
for EP, 0.05 ± 0.03 for CP, 0.44 ± 0.04 for MEW, 0.02 ± 0.02 for H and 0.67 ± 0.02
for MCW. Permanent environmental effects as a ratio of phenotypic variance (c2
pe)
ranged from 0.08 ± 0.03 to 0.11 ± 0.02 for the first four traits (MCW did not exhibit a
significant c2
pe effect). Monthly EP and CP were highly correlated at all levels,
ranging from 0.74 for the temporary environmental correlation to unity for the genetic
correlation. Hatchability was highly correlated with EP and CP at the genetic level
(>0.94). Genetic correlations of EP and CP with MEW and MCW were variable and
in some cases antagonistic. Genetic correlations of H with MEW and MCW were
positive (0.52 and 0.47, respectively). Results indicate that selection for improved
reproduction (reproductive output and product quality traits) is feasible. Selection for
production is unlikely to be complicated by unfavourable correlations with H, MEW
and MCW.
Hen traits defined above were further analysed in single-trait mixed models
with a random regression fitted as an intercept for the direct animal (a) and a
quadratic polynomial with intercept for the permanent environmental (p) effect
peculiar to each hen. Heritability (h2) estimates were moderate and remained
relatively constant for EP and CP ranging from 0.13-0.14 and 0.07-0.08 respectively
for 3- to 10-year old hens. Quality traits MEW and MCW had moderately high h2
estimates ranging from 0.49-0.61 and 0.37-0.45 respectively. Hatchability had h2
estimates ranging from 0.11-0.13 for the 10 hen-ages. Permanent environment
variance ratio for EP, CP, MEW, MCW and H ranges were 0.28-0.42, 0.29-0.41,
0.17-0.33, 0.21-0.35 and 0.14-0.24 respectively. Selection of superior hens from
three years onwards seems possible. Hens older than eleven years should be replaced
with younger, genetically superior hens which would reduce the generation interval
and improve EP and CP genetically, without adversely affecting MEW, MCW and H.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-05172013-113410 |
| Date | 17 May 2013 |
| Creators | Fair, Michael Denis |
| Contributors | Prof SWP Cloete, Prof JB van Wyk |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-05172013-113410/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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