• Korea journal of population studies
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• v.29 no.2
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• pp.89-113
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• 2006

Over the past four decades reproductive behavior has changed rapidly in much of the developing countries. The average total fertility rate has fallen by half from six or more to near three today. Between 1960 and 2000 the largest fertility decline occurred in Asia and Latin America. The mortality rate has also decreased in most developing countries. The purpose of this study is to review the pattern and characteristic of demographic transition in developing countries. At first, this study focuses on the regional fertility and mortality transition. Africa, the total fertility rate is still high, can be match to the second stage of demographic transition. Similar case is found in Southern West Asia areas. However, the fertility rate has therd stage of demographic transition. The same pattern is found in Latin America. The mortality rate has also decreased in most of developing countries. It is interesting to find that there is a clear difference among developing countries. In terms of crude death rate, Latin American countries show the lowest rate. while African countries remain still high rate. About mortality, African countries show a high level in terms of both crude death rate and infant mortality rate. African countries also show the lowest level of life expectancy in the world. One of the reasons for low level of life expectancy in Africa is the widespread of AIDS in this areas. This study suggests that we should include 'AIDS' in the study of mortality in African countries.

• Journal of The Korean Society of Grassland and Forage Science
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• v.31 no.4
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• pp.345-352
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• 2011

Soil fertility different depend on application rate of manure and compost for many years. While each crop has different adaptability depend on soil fertility, crop and species or varieties should be chosen depending on the adaptability and productivity. These experiments were carried out to compare the five winter cereal crops for whole crop silage on growth, yield and feed value as affected by soil organic content. The rate of increase on no. of spikes at high fertile soil compared with medium fertile soil was sequently high Samhan (Oat's variety) > Cheongwoo (Wheat) > Gogu (Rye) > Youngyang (Barley) > Shinyoung (Triticale). The rate of decrease at low fertile soil compared with medium fertile soil was sequently high Youngyang > Gogu > Cheongwoo > Shinyoung > Samhan. The triticale was lower variation of no. of spikes as affected by soil organic content than that of other winter cereals. The variations of dry matter yield as affected by soil fertility was higher oat and barley and lower triticale. Forage yield of triticale was higher about 69 percent than that of barley at low fertile soil. Forage yield was the highest in triticale and the lowest in rye in all soil fertility. In high fertile soil, rate of increasing digestible dry matter (DDM) yield compared with medium fertile was high in Samhan and Youngyang. Rate of reduced DDM yield in low fertile soil compared with medium fertile was low in Shinyoung and Cheongwoo.

• Clinical and Experimental Reproductive Medicine
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• v.47 no.4
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• pp.312-318
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• 2020

Objective: The objective of the study was to compare the effects of long-term and short-term embryo culture to assess whether there is a correlation between culture duration and clinical outcomes. Methods: Embryos were divided into two study groups depending on whether their post-warming culture period was long-term (20-24 hours) or short-term (2-4 hours). Embryo morphology was analyzed with a time-lapse monitoring device to estimate the appropriate timing and parameters for evaluating embryos with high implantation potency in both groups. Propensity score matching was performed to adjust the confounding factors across groups. The grades of embryos and blastocoels, morphokinetic parameters, implantation rate, and ongoing pregnancy rate were compared. Results: No significant differences were observed in the implantation rate or ongoing pregnancy rate between the two groups (long-term culture group vs. short-term culture group: 56.3% vs. 67.9%, p=0.182; 47.3% vs. 53.6%, p=0.513). After warming, there were more expanded and hatching/hatched blastocysts in the long-term culture group than in the short-term culture group, but there was no significant between-group difference in embryo grade. Regarding pregnancy outcomes, the time to complete blastocyst re-expansion after warming is shorter in women who became pregnant than in those who did not in both culture groups (long-term: 2.19±0.63 vs. 4.11±0.81 hours, p=0.003; short-term: 1.17±0.29 vs. 1.94±0.76 hours, p=0.018, respectively). Conclusion: The outcomes of short-term culture and long-term culture were not significantly different in vitrified-warmed blastocyst transfer. Regardless of the post-warming culture time, the degree of blastocyst re-expansion 3-4 hours after warming is an important marker for embryo selection.

• Journal of Families and Better Life
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• v.25 no.6
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• pp.1-13
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• 2007

The purpose of this study is to examine the college students' and married adults' perceptions of the current low fertility and their motivations of parenthood. It also verifies the gender differences in the numbers of planned children between male and female college students. The sample population included 100 unmarried undergraduate students and 100 married adults. The measurements included in the questionnaire were based on recommendations from the literature review. The major findings of this study are as follows: Women reported higher levels of traditional-normal and altruistic-emotional motivations of parenthood than men did. College students reported higher levels of motivations of parenthood to strengthen biological family ties than married adults did, while adults reported higher levels of martial bond-strengthening, traditional-normal, and gene-preservative motivations of parenthood than students did. College students attributed the current low fertility to the tight labor market and high costs of childbirth and rearing while married adults attributed to gender-discriminating traditional family norms, increasing infertility, and poor conditions of pregnancy and childbirth. Female and adult respondents took the social problems caused by the current low fertility more seriously than their counterparts did.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.5
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• pp.702-707
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• 1999

A percoll density gradient technique was developed for producing high quality turkey semen and improving the fertility by removing deleterious cellular components, including spermiophages, bacteria, abnormal or dead spermatozoa, and other cellular debris. The combination of three different percoll densities, 1.05, 1.07, and 1.08 showed the best resolution and was selected to prepare a discontinuous percoll density gradient to obtain healthy spermatozoa from semen smples. Bacteria, spermiophages, and abnormal or dead spermatozoa were detected from the density range from 1.05, 1.05 to 1.07, and 1.07 to 1.08, respectively. Healthy spermatozoa were collected from the density greater than 1.08. Spermatozoa obtained from percoll density gradient centrifugation showed better sperm motility than those from unprocessed pooled semen. Bacteria including Escherichia coli, Staphylococcus aureus, and Proteus spp., were predominant contaminants in turkey semen, and the numbers of cells were approximately $5{\times}10^5$ to $1{\times}10^9cfu/ml$. The overall fertility rates in hens inseminated with processed percoll density gradient were higher than those in hens with unprocessed semen especially for unhealthy sperm. In conclusion, semen quality can be improved by percoll density gradient centrifugation, which augmented the fertility of turkey breeders.

• Asian Journal of Turfgrass Science
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• v.13 no.2
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• pp.79-90
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• 1999

This study was conducted to provide basic understandings for proper management of zoysiagrass fairways. Mowing intervals of 2, 4 and 6-days, with and without aeration were compared at two fertility levels. Turfgrass quality, growth and pest infestation were evaluated. Turf density, number of tillers, leaf width and resiliency were significantly affected by mowing frequency. Turfgrass plots mowed every 2-day had greater density, tillering, and resiliency but had narrower leaf width compared to other mowing treatments. Clipping dry weight with every 2-day mowing increased in the early stage of mowing treatment regardless of fertilizer application rates but gradually decreased in the later stage of mowing treatment compared to every 4 or 6-day mowings. The dry weight of above-ground part was not affected by mowing frequency, but that of underground part was significantly higher for every 6-day mowing frequency(3.3kg/day/m2) compared to every 2 or 4-day mowings. The organic mater content in soil was not different among mowing treatments but it was significantly reduced by the core aerification treatment, indicating significant effect of core aerification on thatch decomposition. Occurrences of weeds such as annual bluegrass and crabgrass according to mowing frequency were greater in every 2-day mowing treatment, while plots mowed every 6 days had less weed occurrence. Occurrence of rusts significantly increased in high fertility plots and frequently mowed turfgrasses.

• International Journal of Advanced Culture Technology
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• v.9 no.1
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• pp.93-98
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• 2021

To develop policies regarding fertility and pregnancy that will be effective in preventing further declines in fertility rates in the context present-day Korea, current policies in Japan were analyzed and compared with those now being implemented in Korea. This study was structured to involve (a) comparison of maternal health projects in Korea and Japan, and (b) comparison of infertility support policies based in regional cities in Korea and Japan. Korea's Health Plan 2030 emphasizes strengthening healthcare for high-risk pregnant women, expanding investments to benefit vulnerable groups, and establishing a support system for infertile couples. In Japan, government programs involving treatment targeting infertility specifically were implemented nationwide in 2006. Wide dissemination of accurate knowledge related to pregnancy is emphasized. Also, counseling centers specializing in infertility were established by 67 local governments. We have confirmed that Korean policies include decentralization, while Japan is implementing the central government's infertility policy uniformly in all regions. Japan also adjusted its policy out of concern that problems related to infertility and childbirth will worsen due to the social disaster of COVID-19. The results indicate that providing additional support for psychological counseling may be preferable to increasing the number of in-vitro fertilization procedures. The physical burden on women may be minimized by benchmarking policies in Japan. Step-by-step application of these procedures should be systematically supported to achieve the best results.

• Reproductive and Developmental Biology
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• v.35 no.3
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• pp.391-394
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• 2011

This study was carried out to investigate the effects of semen on reproductive ability in crossbred Korean native chicken (KNC, 58-wk old). The body weight, volume of semen and concentration of spermatozoa, were 2.96 g, 0.40 ml, $36.58{\times}10^8/ml$, respectively, in KNC. The fertility and hatchability were 94.8% and 78.8% respectively in crossbred KNC. KNC(Y) was high compared to other strains in fertility. The other strains were not significantly different among 6 strains. The results of this experiment indicated that hatchability of (G) was high compared to other strains. The result of this study could be available to genetic improvement of reproductive traits as a basic reference in KNC strains. To achieve the more effective improvement of reproductive traits, addition research such as genetic parameter evaluation should be performed.

• Korean Journal of Animal Reproduction
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• v.7 no.2
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• pp.57-71
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• 1983

1. Diluted chicken semen can be preserved at 2 to 5$^{\circ}C$ for 24 to 48 hr with resultant fertility of greater than 90% of that of fresh semen. Turkey semen can be preserved at 10 to 15$^{\circ}C$ for 6 to 24 hr and provide economical fertility. 2. Frozen chicken semen has given variable results; a 21 to 93% fertility ranges as compared to 92 to 94% expected with fresh semen. Highest fertility levels obtained with frozen turkey semen intravaginally inseminated have been 61 and 63% using DMSO and glycerol, respectively, as cryoprotectants. 3. The use of glycerol as a cryoprotectant reauires that its concentration in semen be reduced to less than 2% either by dialysis or centrifugation after thawing and before intravaginal insemination if optimal fertility is to be obtained. 4. The temperature at which cryoprotectants are added to semen and the time allowed for equilibration are important for subsequent fertility pre- and post-freezing. 5. The type of container used for packaging the semen, freeze or cooling rates, thaw rates and level of cryoprotectant all interact in affecting cell survival. 6. Plastic freeze straws as a packaging device for semen offers the following advantages: easy to handle, require minimal storage space, offer a wide range of freeze and thaw rates, and insemination can be made directly from them upon thawing. 7. Controlled slow cooling rates of 1 to 8$^{\circ}C$/min have thus far provided the best results for cooling chicken semen throught the transition phase change (liquid to solid) or critical temperature range of ＋5 to -20 or -35$^{\circ}C$. 8. Highest fertilities have been achieved with frozen chicken semen where a slow thaw rate (2。 to 5$^{\circ}C$) has been used regardless of the freeze rate. 9. To maintain a constant high level of fertility throughout a breeding season with frozen semen, a higher absolute number of spermatozoa must be inseminated (2 to 3 times as many) as compared to fresh semen since a, pp.oximately 50% are destroyed during processing and freezing. 10. The quality of semen may vary with season and age of the male. Such changes in sperm quality could be accentuated by storage effects. Thus, the correct number of spermatozoa may very well vary during the course of a breeding period. 11. As to time of insemination, it is best to avoid inseminating chicken hens within 1-2 hr after or 3-5 hr before oviposition; and turkey hens during or 7-10 hr before oviposition. 12. The physiological receptiveness of the oviduct at the time of insemination is a very important biological factor influencing fertility levels throughout the breeding season.

• Korea journal of population studies
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• v.28 no.2
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• pp.183-203
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• 2005

Over the past four decades reproductive behavior has changed rapidly in much of the developing countries. The average total fertility rate has fallen by half from six or more to near three today. Between 1960 and 2000 the largest fertility decline occurred in Asia and Latin America. The mortality rate has decreased in most developing countries. The purpose of this study is to review the pattern of demographic transition in developing countries. At first, this study focuses on the regional fertility transition. In Africa, the total fertility rate has decreased from 6.59 to 4.85 between 1960 and 2000. However, the rate has rapidly fallen from 5.76 to 2.34 in East Asia. The same pattern is found in Latin America. The mortality rate has also decreased in most of developing countries. It is also interesting to find that there is a clear difference among developing countries. In terms of crude death rate, Latin American countries show the lowest rate, while African countries remain still high rate. The study also shows the relationship between socioeconomic indicators and fertility/mortality in developing countries. The result supports the hypothesized relationship between education and fertility. However, the effects of urbanization and income on fertility do not show consistent result. About mortality rate, however, the study shows the significant relationship between urbanization and infant mortality rate, between income and mortality. The study finally emphasizes that we should include 'AIDS' in the study of mortality in African countries.