Correlations in fertility across generations: can low fertility persist?

Correlations in family size across generations could have a major influence on human population size in the future. Empirical studies have shown that the associations between the fertility of parents and the fertility of children are substantial and growing over time. Despite their potential long-term consequences, intergenerational fertility correlations have largely been ignored by researchers. We present a model of the fertility transition as a cultural process acting on new lifestyles associated with fertility. Differences in parental and social influences on the acquisition of these lifestyles result in intergenerational correlations in fertility. We show different scenarios for future population size based on models that disregard intergenerational correlations in fertility, models with fertility correlations and a single lifestyle, and models with fertility correlations and multiple lifestyles. We show that intergenerational fertility correlations will result in an increase in fertility over time. However, present low-fertility levels may persist if the rapid introduction of new cultural lifestyles continues into the future.     

Kin influences on fertility in Thailand: Effects and mechanisms

It has been suggested that human mothers are cooperative breeders, as they need help from others to successfully raise offspring. Studies working under this framework have found correlations between the presence of kin and both child survival and female fertility rates. This study seeks to understand the proximate mechanisms by which kin influence fertility using data from the 1987 Thailand Demographic and Health Survey (DHS), a nationally representative sample of 6775 women. Kin influence is measured by the length of time couples live with the husband's or wife's parents after marriage. Event history analysis, multilevel modeling and structural equation modeling are used to investigate both fertility outcomes and potential pathways through which postnuptial residence may influence fertility outcomes, including employment status, maternal and child outcomes, contraceptive use, breastfeeding duration, and age at marriage. We show that living virilocally (with husband's kin after marriage) increases total fertility by shortening time from marriage to first birth, and increasing the likelihood of progression to each subsequent birth. These effects are mediated through correlations between virilocal residence and earlier age at marriage as well as delayed initiation of contraceptive use. We find no influence of husband's kin on maternal or child outcomes. Living uxorilocally (with wife's kin after marriage) also reduces age at marriage, shortens time from marriage to first birth and (marginally) improves child survivorship, but has no effect on other child and maternal outcomes or progression to subsequent births and results in a similar number of living children as women living neolocally.     

In Vitro Evaluation of Frozen-Thawed Stallion Semen: A Review

The article reviews methods used for in vitro evaluation of sperm, with particular emphasis on frozen-thawed stallion sperm. The techniques, limitations of the methods and correlations with fertility results are discussed. Very few studies have tried to find correlation between fertility of frozen stallion semen and laboratory tests. It is difficult and expensive to inseminate an adequate number of mares to achieve statistically significant differences. Significant, but low correlations have been demonstrated between the foaling rate and subjective motility of sperm incubated for 2 h and 4 h at 37°C and hypoosmotic swelling test after 0 and 3 h of incubation. Significant correlations have been reported between the pregnancy rate and viability of propidium iodide-stained sperm assessed by flow cytometry as well as for glass wool and Sephadex filtration tests. No correlations have been detected between fertility and motility immediately after thawing. In spite of that, motility estimation by light microscope is the most commonly used method to evaluate frozen-thawed stallion sperm. Computer assisted automatic sperm analyzers have replaced light microscopy in research projects, but so far nobody has been able to demonstrate a correlation between fertility of frozen stallion semen and any of the motility parameters obtained by these instruments.     

Multiple-trait multiple-country genetic evaluation of Holstein bulls for female fertility and milk production traits

The aim of this study was to investigate the effect of including milk yield data in the international genetic evaluation of female fertility traits to reduce or eliminate a possible bias because of across-country selection for milk yield. Data included two female fertility traits from Great Britain, Italy and the Netherlands, together with milk yield data from the same countries and from the United States, because the genetic trends in other countries may be influenced by selection decisions on bulls in the United States. Potentially, female fertility data had been corrected nationally for within-country selection and management biases for milk yield. Using a multiple-trait multiple across-country evaluation (MT-MACE) for the analysis of female fertility traits with milk yield, across-country selection patterns both for female fertility and milk yield can be considered simultaneously. Four analyses were performed; one single-trait multiple across-country evaluation analysis including only milk yield data, one MT-MACE analysis including only female fertility traits, and one MT-MACE analysis including both female fertility and milk yield traits. An additional MT-MACE analysis was performed including both female fertility and milk yield traits, but excluding the United States. By including milk yield traits to the analysis, female fertility reliabilities increased, but not for all bulls in all the countries by trait combinations. The presence of milk yield traits in the analysis did not considerably change the genetic correlations, genetic trends or bull rankings of female fertility traits. Even though the predicted genetic merits of female fertility traits hardly changed by including milk yield traits to the analysis, the change was not equally distributed to the whole data. The number of bulls in common between the two sets of Top 100 bulls for each trait in the two analyses of female fertility traits, with and without the four milk yield traits and their rank correlations were low, not necessarily because of the absence of the US milk yield data. The joint international genetic evaluation of female fertility traits with milk yield is recommended to make use of information on several female fertility traits from different countries simultaneously, to consider selection decisions for milk yield in the genetic evaluation of female fertility traits for obtaining more accurate estimating breeding values (EBV) and to acquire female fertility EBV for bulls evaluated for milk yield, but not for female fertility.     

Genetic parameters for endocrine and traditional fertility traits,hyperketonemia and milk yield in dairy cattle

High-yielding cows may suffer from negative energy balance during early lactation, which can lead to ketosis and delayed ability of returning to cyclicity after calving. Fast recovery after calving is essential when breeding for improved fertility. Traditionally used fertility traits, such as the interval from calving to first insemination (CFI), have low heritabilities and are highly influenced by management decisions. Herd Navigator™ management program samples and analyses milk progesterone and β-hydroxybutyrate (BHB) automatically during milking. In this study, the genetic parameters of endocrine fertility traits (measured from milk progesterone) and hyperketonemia (measured from milk BHB) in early lactation were evaluated and compared with traditional fertility traits (CFI, interval from calving to the last insemination and interval from first to last insemination) and the milk yield in red dairy cattle herds in Finland. Data included observations from 14 farms from 2014 to 2017. Data were analyzed with linear animal models using DMU software and analyses were done for first parity cows. Heritability estimates for traditional fertility traits were low and varied between 0.03 and 0.07. Estimated heritabilities for endocrine fertility traits (interval from calving to the first heat (CFH) and commencement of luteal activity (C-LA)) were higher than for traditional fertility traits (0.19 to 0.33). Five slightly different hyperketonemia traits divided into two or three classes were studied. Linear model heritability estimates for hyperketonemia traits were low, however, when the threshold model was used for binary traits the estimates became slightly higher (0.07 to 0.15). Genetic correlation between CFH and C-LA for first parity cows was high (0.97) as expected since traits are quite similar. Moderate genetic correlations (0.47 to 0.52) were found between the endocrine fertility traits and early lactation milk yield. Results suggest that the data on endocrine fertility traits measured by automatic systems is a promising tool for improving fertility, specifically when more data is available. For hyperketonemia traits, dividing values into three classes instead of two seemed to work better. Based on the current study and previous studies, where higher heritabilities have been found for milk BHB traits than for clinical ketosis, milk BHB traits are a promising indicator trait for resistance to ketosis and should be studied more. It is important that this kind of data from automatic devices is made available to recording and breeding organizations in the future.     

Population ageing: what should we worry about?

Approximately half the world''s population now has replacement-level fertility or below. The UK experience in accommodating to a changing dependency ratio provides some generalizable insights. A mechanistic approach assuming a fixed retirement age and a need to raise fertility or increase immigration in order to maintain pensions at a fixed proportion of the gross domestic product (GDP) is overstated and wrong. It needs to be replaced by a welfare optimizing model, which takes into account the increasing years of healthy life, a slow rise in the pensionable age, capital inheritance and wider welfare considerations of population density that are not reflected in GDP measures. A combined replacement ratio (CRR) is suggested for developed countries combining the impact of the fertility rate and immigration rate. A CRR above 2 implies continued population growth. The current UK CRR of 2.48 is higher than needed for pension reasons, and it is suggested that it exceeds the welfare maximizing level.     

不同地区青檀根际土壤肥力和真菌多样性及其相关性分析

为了探明不同地区青檀(Pteroceltis tatarinowii Maxim.)根际土壤真菌多样性及其与土壤肥力的关系,对国内7省(广西、安徽、河南、陕西、四川、山东和辽宁)1市(北京)8个样地野生青檀根际土壤的肥力指标(包括pH值、速效磷含量和速效钾含量)进行比较,并采用Illumina MiSeq高通量测序技术对其根际土壤的真菌多样性进行了分析;在此基础上,对土壤真菌多样性指数与土壤肥力指标的相关性以及土壤真菌科水平相对丰度前20位的操作分类单元(OTUs)与土壤肥力指标的相关性进行分析.结果表明:供试8个样地青檀根际土壤的pH值为pH 6.06~pH 7.61,速效磷含量为0.49~3.27μg·g-1,速效钾含量为150.24~636.89μg·g-1.基于土壤真菌DNA测序结果,以有效序列相似度97%为阈值获得7143个OTUs,鉴定出6门32纲106目254科,其中,包括子囊菌门(Ascomycota)、担子菌门(Basidiomycota)和接合菌门(Zygomycota)3个优势门以及Incertae sedis(GenBank数据库中存在,但未准确分类的科)、被孢霉科(Mortierellaceae)、发菌科(Trichocomaceae)、丛赤壳科(Nectriaceae)和Archaeorhizomycetaceae 5个共有优势科;不同样地的土壤真菌多样性差异明显,Chao1指数、Shannon-Wiener指数和Simpson指数分别为1041.37~1793.19、5.39~6.14和0.007~0.020,盖度为98.90%~99.84%.相关性分析结果表明:土壤真菌Chao1指数与土壤速效钾含量呈显著(P<0.05)负相关,其余土壤真菌多样性指数与土壤肥力指标的相关性均不显著;在相对丰度前20位的OTUs中,55%OTUs与土壤pH值呈负相关,并且,多数OTUs与土壤的速效磷含量和速效钾含量呈正相关,其中,OTU0(被孢霉科)与土壤pH值呈显著负相关,OTU1(丛赤壳科)和OTU4(伞型束梗孔菌科)(Agaricostilbaceae)与土壤速效钾含量呈显著正相关.研究结果显示:野生青檀根际土壤呈弱酸性至弱碱性,并具有富钾少磷的特点;青檀根际土壤真菌多样性与土壤肥力有一定相关性,并且,被孢霉科、丛赤壳科和伞型束梗孔菌科与土壤肥力有显著相关性.     

Dilauroylphosphatidylcholine liposome effects on the acrosome reaction and in vitro penetration of zona-free hamster eggs by bull sperm: II. A fertility assay for frozen-thawed semen

Frozen-thawed sperm from five bulls with fertility rates ranging from 48% to 77% were treated with seven concentrations of dilauroylphosphatidylcholine (PC12) liposomes to induce an acrosome reaction (AR) that enabled sperm to penetrate eggs. Treated sperm were incubated with liposomes for 7 min prior to insemination of zona-free hamster eggs in vitro. Sperm and eggs were incubated 3 hr at 39°C prior to fixation, staining, and examination for sperm penetration and nuclear decondensation. The percentage of motile sperm immediately after thawing as well as after treatment with liposomes had a low correlation with sire fertility (r = .39 and ?.63, respectively). The percentage of sperm exhibiting an AR was more highly correlated with fertility (r ? ?.85). Similar correlations were found between fertility and the penetration rates of zona-free hamster eggs or the total number of penetrating sperm. When data for two high and for two lower fertility buils were each grouped to increase information per data point the correlation between the PC12 concentration giving the maximum proportion of eggs penetrated and fertility was r = .92 (P ≤ .05). The correlation between the PC12 concentration producing the most total sperm penetrating the eggs and fertility r = .97 (P ≤ .05). It was concluded that PC12 liposomes induced an AR in bull sperm frozen-thawed in egg yolk extender. Frozen-thawed sperm from low fertility bulls require less PC12 to induce the AR and to penetrate zona-free hamster eggs than do sperm from higher fertility bulls. These differences in lipid requirements may help to provide a quick, direct laboratory assay method to estimate the fertility of frozen bull semen.     

Assortative mating for anthropometric traits in parents of Punjabi twins

The marital correlations between 97 pairs of parents of Punjabi twins reveal positive phenotypic assortative mating for body traits while almost random mating with respect to cranio-facial traits. There is no evidence of any significant negative assortative mating for any of the 50 traits. The results have been compared with those from other world populations. The data contradict the earlier reported hypothesis that assortative mating is associated with lowered fertility.     

New evidence for dysgenic fertility for intelligence in the United States

Data were taken from the 1994 National Opinion Research Center survey of a representative sample of American adults to examine the relation between the intelligence of adults aged 40+ and their numbers of children and their numbers of siblings. The correlations were found to be significantly negative at -0.05 and -0.09, respectively, indicating the presence of dysgenic fertility. Further analysis showed that dysgenic fertility is present only in females. The correlation for females between intelligence and ideal numbers of children was effectively zero, indicating that if women had the numbers of children they consider ideal, dysgenic fertility would be reduced.     

Can pre-collected register data be used to identify dairy herds with good cattle welfare?

Background

Pre-recorded register data from dairy herds are available in almost all Nordic countries. These databases can be used for research purposes, and one of the research areas is animal welfare. The aim of this study was to investigate if pre-recorded register data could be used to identify herds with good welfare, and to investigate if a combination of register data sets could be used to be able to more correctly distinguish between herds with good welfare and herds with welfare deficiencies.

Methods

As a first step, nine animal-based measurements on calves, young stock and cows in 55 randomly selected herds were performed on-farm as the basis for a classification of welfare at the herd level. The definition for being a case herd with “good welfare” was no score lying among the 10% worst in any of the nine welfare measurements. Twenty-eight of the 55 herds were cases according to this definition. As a second step, 65 potential welfare indicators, based on register data in a national dairy database, were identified by expert opinion. In the final step, the extent to which the suggested welfare indicators predicted farms’ as having good welfare according to the stated definition was assessed. Moreover, the effect of combining in sequence a previously developed model that identified herds with poor welfare with the present model identifying herds with good welfare was investigated.

Results

The final set of welfare indicators used to identify herds with good animal welfare included two fertility measures, cow mortality, stillbirth rate, mastitis incidence and incidence of feed-related diseases (including gastrointestinal disturbances but excluding paralyses and cramps). This set had a test sensitivity of correctly classifying herds with no score lying among the 10% worst of the nine welfare measurements of 96 %. However, the specificity of the test was only 56% indicating difficulties for the test to correctly classifying herds with one or more scores lying among the 10% worst. Combining the previously developed model with the present model, improved the welfare classification.

Conclusions

This study shows that pre-collected register data may be used to give approval to dairy farms with “good welfare” and that combining different sets of register data can improve the classification of herd welfare.

     

A conceptual model for the identification, organization, and measure of influence of fertility policies and programs.

The fertility program of any government is the procedural action intended to effect the government fertility policy. There may also be unintended results of any fertility program. A conceptual model was designed to measure the effect of governmental action on fertility and to identify sociocultural factors that have the greatest influence on fertility. The model uses sociocultural variables as intervening variables between fertility programs and changes in actual fertility. The structural variables considered by the model are characteristics of the pattern of social order; the cultural variables consist of shared values and norms. Fertility trend analysis is effected by polynomial regression formulae. Puerto Rican data from 1946 to 1970 were used to test the proposed model. Analysis of the data indicated that emigration between 1940-1962 had little effect on national fertility. Governmental family planning programs, beginning in 1946, contributed to a sharp decline in fertility. It is recommended that the model be used with data from other countries to assess the effects of their family planning programs.     

Intergenerational health effects of Medicaid

This paper investigates the effects of the introduction of Medicaid during the 1960s on next generations’ birth outcomes. A federal mandate that all states must widen the coverage to all cash welfare recipients generated cross-state variations in Medicaid eligibility, specifically among nonwhites who largely overrepresented the target population. I implement a reduced-form difference-in-differences strategy that compares the birth outcomes of mothers born in states with higher cash welfare recipiency versus low welfare recipiency and different years relative to the Medicaid implementation year. Using Natality data (1970–2004), I find that Medicaid significantly improves birth outcomes. The effects are considerably larger among nonwhites, specifically blacks. The effects do not appear to be driven by preexisting trends in birth outcomes, preexisting trends in households’ socioeconomic characteristics, changes in other welfare expenditures, and selective fertility. A back-of-an-envelope calculation points to a minimum of 3.9% social externality of Medicaid through income rises due to next generations’ improvements in birth outcomes.     

Quality of semen stored at +15 degrees/16 degrees C as related to fertility of artificially inseminated swine

Linear correlations between swine semen quality and fertility (birth rate and number live born pigs) were studied. Doses of swine semen with 4 × 10⁹ motile spermatozoa were used after being stored at +15°/16°C. However, mean or high correlations could not be found. Low correlations occurred between head-acrosome anomalies, total anomalies and birth rate. It is likely that the doses of semen with 4 × 10⁹ motile spermatozoa were too concentrated for the fertility level in the swine breed employed.     

Edaphic Factors are a More Important Control on Surface Fine Roots than Stand Age in Secondary Tropical Dry Forests

Although there are generalized conceptual models that predict how above and belowground biomass increase during secondary succession after abandonment from agriculture, there are few data to test these models for fine roots (defined as ≤2 mm diameter) in tropical forests. We measured live and dead fine roots (0–10 cm depth) in 18 plots of regenerating tropical dry forest in Costa Rica that varied in age from 5 to 60 yrs, as well as in soil properties. We predicted that both stand age and soil fertility would affect fine roots, with greater values in older forests on low fertility soils. Across two sampling dates and locations, live fine roots varied from 0.35 to 3.53 Mg/ha and dead roots varied from 0.15 to 0.93 Mg/ha. Surprisingly, there was little evidence that surface fine roots varied between sampling dates or in relation to stand age. By contrast, total, live, and dead fine roots averaged across sampling dates within plots were negatively correlated with a multivariate index of soil fertility (Pearson correlations coefficients were ?0.64, ?0.58, and ?0.68, respectively; P < 0.01) and other individual edaphic variables including pH, silt, calcium, magnesium, nitrogen, and phosphorus. These results suggest that soil fertility is a more important determinant of fine roots than forest age in tropical dry forests in Costa Rica, and that one‐way these plant communities respond to low soil fertility is by increasing fine roots. Thus, simple conceptual models of forest responses to abandonment from agriculture may not be appropriate for surface fine roots.     

On-farm assessment of laying hen welfare: a comparison of one environment-based and two animal-based methods

Methods available to assess animal welfare at farm level are based on a range of welfare parameters, which can be divided into two categories, environment-based and animal-based parameters. The first category describes features of the environment and management, which can be considered prerequisites for welfare. The second category records animals’ responses to that particular environment and management more directly. Objective of this study was to validate a mainly environment-based method, the animal needs index (ANI), with animal-based methods: behavioural observations and feather condition scores (FCS). The study was conducted on 20 commercial laying hen farms, 10 farms with battery cages and 10 farms with deep litter systems. During a 1-day visit on each farm, ANI was assessed, FCS was scored, and behavioural observations were performed. Instantaneous scan sampling and continuous focal sampling were used to assess the time spent on different behaviours and the occurrence of event behaviours. Data from behavioural observations and FCS were reduced with principal factor analysis. This resulted in two factors for each method. Significant positive correlations were found between ANI, on the one hand, and ‘movement’ and ‘comfort’, two factors from behavioural observations, on the other hand. A significant negative correlation was found between ANI and ‘wing damage’ (from FCS). The results of this study show that ANI is valid and sensitive enough to show differences in animal welfare between housing systems, whereas differences in welfare within housing systems cannot be shown. In conclusion, ANI is an appropriate method for assessment of laying hen welfare on a large number of farms with different housing systems.     

The evolved psychological mechanisms of fertility motivation: hunting for causation in a sea of correlation

Cultural, ecological, familial and physiological factors consistently influence fertility behaviours, however, the proximate psychological mechanisms underlying fertility decisions in humans are poorly understood. Understanding the psychological mechanisms underlying human fertility may illuminate the final processes by which some of these known predictors have their influence. To date, research into the psychological mechanisms underlying fertility has been fragmented. Aspects of reproductive psychology have been examined by researchers in a range of fields, but the findings have not been systematically integrated in one review. We provide such a review, examining current theories and research on psychological mechanisms of fertility. We examine the methods and populations used in the research, as well as the disciplines and theoretical perspectives from which the work has come. Much of the work that has been done to date is methodologically limited to examining correlations between ecological, social and economic factors and fertility. We propose, and support with examples, the use of experimental methods to differentiate causal factors from correlates. We also discuss weaknesses in the experimental research, including limited work with non-WEIRD (western, educated, industrialized, rich and democratic) populations.     

Uncertainties in predicting the demographic impact of AIDS

A model giving the demographic impact of AIDS is analysed to examine the sensitivity of the projections when various complicating features are included. The model deals with age and sexual partner change rate as continuous variables and uses a device to specify arbitrary correlations between the ages of the people who form sexual partnerships. The device ensures consistency, in that the amount of partner formation is the same regardless of whether the partnerships are counted from the point of view of males or females. Arbitrary correlation between partner change rate and fertility is also permitted. The results show the uncertainty in model predictions that population growth will reduce over the next 20 years to approximately zero in parts of East Africa severely affected by the AIDS epidemic. The main sources of uncertainty in the model predictions are assumptions concerning the correlation between ages in a partnership, the correlation between partner change rate and fertility, the incubation period of AIDS, and the variability of the female partner change rate.     

Thermoresistance sperm tests are not predictive of potential fertility for cryopreserved bull semen

Different studies demonstrate positive correlations between seminal variables determined in the laboratory and subsequent fertility after artificial insemination. It is clear, however, that there is still a deficiency in predicting in vivo fertility results of semen samples. The present study intended to verify the efficiency of rapid and slow thermoresistance tests in predicting fertility of frozen semen of bulls. Sperm from 64 ejaculates of 39 Nelore bulls (Bos indicus), aged 2-10 years, were cryopreserved in 0.5 mL straws. Thawed straws containing 30 x 10(6) sperm were analyzed for seminal variables in the laboratory and used to inseminate 4920 cows to evaluate fertility in the field. The ejaculates were frozen in a Tris-based extender and samples were evaluated for total motility after rapid (46 degrees C/30 min) and slow (38 degrees C/5h) thermoresistance tests by conventional and computerized (CASA) methods. Sperm samples were grouped according to their ability to retain motility after thermoresistance testing: group 0 (0% motility), group 1 (1-20% total motility), group 2 (21-40% total motility) and group 3 (>40% total motility). Correlation and association between these groups and fertility diagnosed by rectal palpation at 90 days were verified. Chi-square test demonstrated no association between motility groups and fertility (P>0.25) and both rapid and slow thermoresistance tests had a lesser correlation to fertility (r=0.11 and 0.14, respectively). These results demonstrated that these tests are not reliable in predicting in vivo behavior of bull frozen semen and are not effective to estimate fertility.