Introduction to the special issue Zimmer‐gembeck, Melanie J.; Dunbar, Michele D.; Ferguson, Samantha ...
Australian journal of psychology,
06/2014, Letnik:
66, Številka:
2
Journal Article
The aim of this study was to investigate the role of FSH in the control of ovulation rate by the Booroola gene. Three Booroola genotypes (FecBFecB, FecBFec+ and Fec+Fec+) of the F2 population, from a ...cross between Booroola Merino and Scottish Blackface, and two Booroola genotypes (FecBFec+ and Fec+Fec+; 25% Booroola Merino and 75% Scottish Blackface), from the backcross of FecBFec+ sires to Scottish Blackface ewes, were compared. During seasonal anoestrus significant differences (P < 0.05) in hCG-stimulated ovulation rates were obtained between FecBFecB and Fec+Fec+ ewes from the F2 population, and FecBFec+ ewes were intermediate. No significant difference in hCG-stimulated ovulation rate was observed in the backcross population between FecBFec+ ewes and Fec+Fec+ ewes. There were no significant differences between genotypes in mean serum FSH concentrations during seasonal anoestrus in either backcross of F2 population. During the breeding season, two separate experiments confirmed the expected ovulation rate differences between genotypes (FecBFecB > FecBFec+ > Fec+Fec+). In both experiments, mean peripheral FSH concentrations in the F2 population were similar in FecBFec+ and Fec+Fec+ ewes, but were significantly higher (P < 0.05) in FecBFecB ewes. In the backcross population, mean peripheral FSH concentrations during the oestrous cycle were not significantly different between FecBFec+ and Fec+Fec+ ewes, despite significant differences in ovulation rate. Ovariectomy during the breeding season resulted in significantly higher (P < 0.001) mean peripheral FSH concentrations in all three genotypes. After ovariectomy, mean FSH concentrations between FecBFec+ and Fec+Fec+ ewes, form both backcross and F2 populations, were not significantly different.
A high and a low response line in sheep were selected on the basis of the mean concentration of LH in 10-week-old Finn-Dorset ram lambs after an i.v. injection of 5 micrograms GnRH. After 8 male ...generations the mean LH response of the high line was more than 5-fold that of the low line and the heritability of the selected trait was estimated at 0.44 +/- 0.015. Highly significant line differences in mean LH response to GnRH were also found in males at 20 weeks of age and females at 10 and 20 weeks of age and the genetic correlations between the four LH response traits appear to be close to unity. Large line differences in the mean FSH response to GnRH were also found in both males and females at 10 and 20 weeks of age. Selection had little effect on the physical characteristics of lambs. High-response line ewes entering their first breeding season at about 7 months of age showed oestrus earlier in the season and had higher ovulation rates and numbers of lambs born per ewe lambing than did low-response line ewes. In the second breeding season, at about 19 months of age, the only line difference was a higher ovulation rate early in the breeding season in high-line ewes. It is suggested that these changes may be mediated by a more rapid response in high-line ewes to increased GnRH stimulation at puberty or at the beginning of the breeding season.
Revolutionary opportunities for the modification of animal performance are being created by the development of new methods for embryo manipulation and the application of molecular biology. This paper ...reviews the potential application of these procedures for the improvement of reproductive performance in livestock. There are three sections: a consideration of the methods of molecular manipulation that are available at present and those that seem likely to become available, a discussion of the modifications to hormonal systems and, finally, an analysis of candidate genes for manipulation of seasonality, number of ovulations, sex ratio and prenatal survival. The analysis points to a number of ways forward. Many of the most promising opportunities will depend upon the isolation of embryonic stem cells or the establishment of alternative methods of site-directed mutation. In most cases, the genes of interest have not yet been cloned and much remains to be learned about the molecular regulation of reproduction. A greater understanding seems likely to reveal the inadequacies of some of the present suggestions, but it is also certain to reveal further opportunities. However, in the longer term, there seems to be a real prospect of modification of at least some of these aspects of reproductive performance by molecular means.
This analysis shows that there could be net gains to the U.S. wheat industry if all U.S. export wheat were to be cleaned to a dockage level between 0.35 to 0.40 percent. These results are based on ...survey results of major importers of U.S. wheat, and a model of world wheat trade. Larger benefits to the U.S. wheat industry would be possible from cleaning only wheat destined to countries that demand higher quality U.S. wheat. However, these gains in export revenue from selling cleaner wheat could be offset if other exporters, especially Canada, responded in ways that would maintain their market share.
This analysis shows that there could be net gains to the U.S. wheat industry if all U.S. export wheat were to be cleaned to a dockage level between 0.35 to 0.40 percent. These results are based on ...survey results of major importers of U.S. wheat, and a model of world wheat trade. Larger benefits to the U.S. wheat industry would be possible from cleaning only wheat destined to countries that demand higher quality U.S. wheat. However, these gains in export revenue from selling cleaner wheat could be offset if other exporters, especially Canada, responded in ways that would maintain their market share.
This analysis shows that there could be net gains to the U.S. wheat industry if all U.S. export wheat were to be cleaned to a dockage level between 0.35 to 0.40 percent. These results are based on ...survey results of major importers of U.S. wheat, and a model of world wheat trade. Larger benefits to the U.S. wheat industry would be possible from cleaning only wheat destined to countries that demand higher quality U.S. wheat. However, these gains in export revenue from selling cleaner wheat could be offset if other exporters, especially Canada, responded in ways that would maintain their market share.
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