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101.
The reproductive performance of 48 Damara, 42 Dorper and 46 Merino ewes was evaluated under an optimum nutritional regime
for Merino ewes that included one annual joining in a mixed (cropping and sheep) farming system in the eastern wheatbelt of
Western Australia (W.A.) over a 3-year period. In 2005, when the Damara, Dorper and Merino ewes were aged between 8 and 9 months
at joining and weighed 41.2, 42.4 and 33.3 kg with average body condition scores of 2.3, 2.4 and 1.8, respectively, their
weaning rates were 71% (Damara), 81% (Dorper) and 13% (Merino). The Merino ewes had significantly lighter body weights and
were lower conditioned (p < 0.001) resulting in significantly lower weaning rates (p < 0.001). In 2006, the Damara, Dorper and Merino ewes weighed 61.9, 69.5 and 61.6 kg at joining, with body condition scores
of 2.8, 3.3 and 2.8, respectively, resulting in weaning rates of 52% (Damara), 122% (Dorper) and 117% (Merino). While the
Damara and Merino weights and body condition scores were not different (p > 0.05), the Damara weaning rates were significantly lower compared with the Dorper and Merino groups (p < 0.001). The Dorpers were heavier and greater conditioned (p < 0.001); however, the weaning rates between the Dorper and Merino were not different (p > 0.05). In 2007, the Damara, Dorper and Merino ewes weighed 71.6, 77.1 and 70.2 kg at joining with body condition scores
of 2.8, 2.8 and 2.5, respectively. Again, the Dorper ewes were heavier (p < 0.001) than the Damaras and Merinos, which were not different (p > 0.05). The Damara and Dorper had the same body condition while the Merino ewes were less and different (p < 0.05). However, there were differences in weaning rates between the three breeds (p < 0.001), of 64% (Damara), 105% (Dorper) and 134% (Merino). Over the 3-year period, under a nutritional management system
optimal for Merino sheep and with one annual joining, with increasing age the Merino ewes weaned more lambs. However, while
the Damara and Dorper ewes conceived and weaned relatively high lamb numbers when they were joined as lambs, their reproductive
performance decreased over time. This nutritional regime resulted in increased levels of fatness of the Damara and Dorper
ewes with no increase in reproduction rates under an annual joining system. A significant factor for the lower conception
and weaning rates in the Damara ewes was the enlarged fat tail due to the increased fat levels, which made it difficult for
the rams to impregnate the ewes. 相似文献
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Genetic and phenotypic parameter estimates for body weights and egg production in Horro chicken of Ethiopia 总被引:1,自引:0,他引:1
Nigussie Dana E. H. vander Waaij Johan A. M. van Arendonk 《Tropical animal health and production》2011,43(1):21-28
A breeding program has been established in 2008 to improve productivity of Horro chicken, an indigenous population in the
western highlands of Ethiopia. The pedigree descended from 26 sires and 260 dams. Body weights were measured every 2 weeks
from hatch to 8 weeks then every 4 weeks for the next 8 weeks. Egg production was recorded to 44 weeks of age for one generation.
Genetic parameters were estimated using animal model fitted with common environmental effects for growth traits and ignoring
common environment for egg production traits. Direct heritabilities ranged from low (0.15 ± 0.08), for body weight at 6 weeks,
to moderate (0.40 ± 0.23), for hatch weight. Heritabilities of common environmental effects on growth were high at hatch (0.39 ± 0.10)
and remained low afterwards. Age at first egg showed a very low heritability (0.06 ± 0.15). Heritabilities of egg numbers
in the first, second, third, and fourth months of laying were 0.32 (±0.13), 0.20 (±0.16), 0.56 (±0.15), and 0.25 (±0.14),
respectively. Heritabilities of cumulative of monthly records of egg numbers were from 0.24 ± 0.16 (for the first 2 months,
EP12) to 0.35 ± 0.16 (over the 6 months, EP16). Body weight at 16 weeks of age (BW16) has a strong genetic correlation with
the cumulative of monthly records: 0.92 (with EP12), 0.69 (with EP36), and 0.73 (with EP16). Besides their strong association,
BW16 and EP16 showed higher heritability, relative to their respective trait categories. These two traits seemed to have common
genes and utilizing them as selection traits would be expected to improve both egg production and growth performance of local
chicken. However, the standard errors of estimates in this study were mostly high indicating that the estimates have low precision.
Parameter estimations based on more data are needed before applying the current results in breeding programs. 相似文献