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Individual fertility rate: a new individual fertility measure for small populations.

Fertility measurement in small preindustrial societies is hampered by small numbers and the lack of some essential data. Most measures of fertility are collective and require large enough populations to permit grouped data analysis. Existing individual measures of fertility are often unsatisfactory. This paper presents a new measure of individual fertility, the Individual Fertility Rate (IFR), which is constructed by dividing parity by reproductive span in years and multiplying the product by 100. The result is a number which may be used as a dependent individual or cumulative variable to study the effects of health and socioeconomic factors on fertility.

Adult↗
PubMed1978

Immunological control of fertility: measurement of affinity of antibodies to human chorionic gonadotrophin.

Four baboons were primed with diazotized beta human chorionic gonadotrophin and boosted with diazotized C-terminal beta human chorionic gonadotrophin peptide, and the changes in antibody amount and affinity determined using a double isotope modified Farr assay, using labelled human chorionic gonadotrophin as the antigen. The degree of cross-reaction with human luteinizing hormone was also determined. Although appreciable reactivity with luteinizing hormone was observed soon after immunization, this declined rapidly during the response. At the time intervals studied, there was a progressive increase in affinity of antibodies to human chorionic gonadotrophin until day 248 after priming. At day 313, in two of the animals, there was a decrease in affinity from 1.04 X 10(11) to 6.80 X 10(10) and 1.05 X 10(11) to 4.93 X 10(10) l/mol, whereas in the other two baboons there was a further increase in antibody affinity. At corresponding time intervals, there was a steady decrease in values of total antibody binding sites. To determine the overall effect of the maturation of affinity with a decrease in antibody amount on biological efficacy, the theoretical amount of chorionic gonadotrophin that would be neutralized was calculated. We computed that in all instances, over 99% of a peak concentration of chorionic gonadotrophin that could be in circulation in a pregnant baboon would be neutralized. This was in excellent agreement with results of mating experiments in these baboons. In over forty cycles studied, none of the matings resulted in a sustained pregnancy.

Animals↗
PubMed1988

Computer modeling of human fertility: the impact of reproductive heterogeneity on measures of fertility.

As a result of the paucity of biological markers for both reproductive events and exposure to reproductive toxicants, it is likely that individual members of populations will be misclassified with respect to reproductive performance and xenobiotic exposure. A four-parameter computerized model of fertility (frequency of intercourse, male fecundity, female fecundity, and spontaneous abortion) was developed to explore the effect of misclassification of populations on several measures of fertility. The measures of fertility explored include cumulative percent pregnant, time to pregnancy, cycle specific fertility, and fecundability ratio. The cumulative percent pregnant and time to pregnancy appeared to be insensitive to small changes in reproductive competence. The fecundability ratio decreased in proportion to the size of population exposed to a reproductive toxicant. The three reproductive parameters, time to pregnancy, cumulative percent pregnant, and fecundability, do not appear useful as measures of reproductive heterogeneity in populations. The reproductive heterogeneity of a population was best defined by the change in cycle-specific fertility rate over the period of observation. These simulations suggest that the change in the cycle-specific fertility rate should be evaluated and comparable in all population groups over the period of observation to assure reproductive homogeneity.

Abortion, Spontaneous↗
PubMed1976

Lifetime probability of additional births by age and parity for American women, 1935-1968: a new measurement of period fertility.

A new fertility measurement, probability that a woman of specified parity and age will bear a given number of births in her remaining lifetime, is proposed in this article. The measurement is a summary index of a set of age-parity-specific birth probabilities and in a particular case it is conceptually analogous to the total fertility by birth order but free from the influence of the parity distribution. Fertility of American women for the period 1935-1968 was studied by use of such lifetime probabilities. It appears that the trend of fertility of high birth orders has been parallel with that of low orders. Initiation of the recent decline in fertility depends on parity and age of woman.

Adolescent↗
PubMed1978

Age, biological factors, and socioeconomic determinants of fertility: a new measure of cumulative fertility for use in the empirical analysis of family size.

To influence the number of children ever born to a woman, socioeconomic variables must operate through behavioral and biological mechanisms such as the age at marriage, the level of fertility in the absence of deliberate fertility control, and the level of control exerted to reduce fertility within marriage. In this paper, we propose a new measure of cumulative fertility which is standardized for the age-fecundity relationship and for exposure to the risk of conception associated with duration of marriage. A simple model of fertility behavior which incorporates some of the mechanisms through which socioeconomic factors may affect fertility is developed and applied to data from the United States to demonstrate the properties of alternative measures of family size. The results indicate that use of the new measure allows more precise estimates of socioeconomic fertility relationships than would be obtained with children ever born or by sample stratification.

Adult↗
PubMed1992

A simple measure of fertility control.

We describe a simple measure of fertility control: the proportion of all births from the age-specific fertility schedule that occurs among women by age 35. This measure has broad applicability because it does not require information on marital fertility rates. When both the proportion of births by age 35 and the most commonly used measure of fertility control, m, are calculated for a population over time, they are correlated very highly. Because of increasing levels of nonmarital fertility in several developed countries, measures of fertility control that are based on marital fertility are less appropriate now than in the past.

Adult↗
PubMed1990

[Fertility controls as the measure of herd fertility of dairy stock].

Hormonal analyses have been conducted along with intensive clinical following-up of the animals of three dairy herds in the area of Thessaloniki/Greece for a two year period. The data and progesterone profiles collected by means of milk progesterone assay (EIA) contribute considerably towards confirming and/or correcting clinical diagnoses. The clinical findings and the fertility parameters illustrate the considerable burden of fertility problems present in the dairy herds. The authors assume that faults in nutrition constitute the cause of silent heat and the problems derived from it. Faulty management is mainly associated with difficulties in oestrus diagnoses owing to disorders of fertility, failure to keep precise fertility data and the effects of inconsistent servicing of the cows on the part of the state inseminators.

Animals↗
PubMed1976

Effect of adjustment for sex composition in the measurement of fertility on intrinsic rates.

The inconsistencies inherent in the one-sex models created a need for the construction of what are known as marriage functions, especially for the measurement of fertility. But attempts to develop marriage functions have been frustrated by the inability of the proposed functions to meet certain consistency conditions and also by difficulties in empiracally determining function parameters. Among several functions proposed so far, Das Gupta's (1972) "effective population" deserves special mention. He uses both sexes in its formulation, and has shown that the constancy of fertility rates based on such a function together with the constancy of survivorship probabilities of both sexes would result in a stable population. It is suggested in this article that the major source of the problem in a two-sex model seems to be the requirement that the model has to be specific both for sex and age. The ideal of incorporating the relative composition of one sex in the age-specific rates of the other, thereby creating a function dependent on both sexes, is advanced in this article. Such functions, defined explicitly for births, can be easily translated into age-specific birth rates. In addition to simplicity in the definition and form, the conditions leading toward stability can also be established. Interestingly enough, the intrinsic rate for this two-sex model lies in the interval determined by the rates obtained from the two one-sex models.

Birth Rate↗
PubMed1990

Some alternatives to calving date and interval as measures of fertility in beef cattle.

Records of 594 calving dates and 493 calving intervals collected from a herd of Retinta beef cows in southwest Spain were studied. Their efficacy as reproductive measures were compared when a long breeding season was utilized. Variables used were date of present calving (DOC), date of subsequent calving (DOSC), time from start of breeding season to calving (TBSC), interval to next calving (CI), two adjustments of calving interval by subtracting the time that bulls were not available to the cow from actual CI (ACI1 and ACI2), and three scores. Period score (SCOR) measured the 20-d increment of the 220-d calving season in which the cow calved. Pair score (PAIR) was computed by subtracting the deviation of calving interval from 365 d from the average SCOR of the two calvings involved. Adjusted pair score (APAIR) was calculated in the same way as PAIR, but using ACI1 instead of CI. Heritability estimates for DOC, SCOR, and DOSC and CI were .16, .14, .13 and 0, respectively. Heritabilities of all other measures ranged from .01 to .06. Repeatability estimates for DOC, SCOR, DOSC and CI were .29, .28, .34 and .14, respectively. Repeatability values were .28, .18, .18, .23 and .32 for TBSC, ACI1, ACI2, PAIR and APAIR, respectively. Genetic and phenotypic correlations among CI and its alternative measures were very high and favorable.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1989

An alternative stochastic framework for estimating pure measures of fertility.

A stochastic fertility model is developed that incorporates a state of "viable pregnancy" within parity i. This model is used as a framework to derive formulas expressing relationships between various central rates and probabilities within parity i. Specifically, formulas are derived to relate the total fertility rate with the parity progression probability, a pregnancy rate with a pregnancy progression probability, and a direct fertility rate with a direct parity progression probability.

Female↗
PubMed1989

Use of farrowing rate as a measure of fertility of boars.

The first 100 single-boar services of 140 boars were analyzed to determine whether the farrowing rate resulting from initial services predicted the farrowing rate of subsequent services. The data were analyzed for the influence of parity, number of matings per estrus, season of service, and interaction of these variables on farrowing rate. Sow parity influenced farrowing rate. Sows with parity greater than 8 and gilts had the lowest farrowing rates (P less than 0.01). Sows with parity 2 through 5 had the highest farrowing rates (P less than 0.01). One and 2 matings/estrus resulted in reduced farrowing rates (P less than 0.01), compared with farrowing rates of greater than 2 matings/estrus. Farrowing rate for services during the summer was lower than that for other seasons of the year (P less than 0.01). Evidence of interaction among these variables was not found. Therefore, the results of each service recorded was adjusted to the mean farrowing rate of sows with parity 2 through 5, sows mated greater than or equal to 3 times/service, and sows serviced in the spring. After these adjustments, the farrowing rates for the first 10, 20, 30, 40, and 50 services were analyzed to determine associations with farrowing rates for subsequent services through 100 farrowings. These data also were analyzed to determine whether the associations were strengthened by removal of the first 10 services from the data. The best farrowing rate association indicated that for each 1% increase in farrowing rate subsequent to the first 50 services, the farrowing rate for the second 50 services increased 0.33% (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Detection of early pregnancy factor in superovulated mice.

Rosette inhibition tests for the detection of early pregnancy factor (EPF) were performed on naturally ovulated and superovulated mice from day 2 of pregnancy up to 4 days after parturition. In both groups of mice, the rosette inhibition titre (RIT) increased on day 2 of pregnancy, and persisted at high levels until day 15. Thereafter, the RITs of both groups of mice decreased to the non-pregnancy range. No significant differences of the mean RITs between these two groups were observed during the high RIT period. These results showed that the superovulatory treatment did not cause any changes or interference in the detection of EPF. In order to investigate the initial time of appearance of EPF in the maternal circulation in relation to the stage of fertilization, measurement of RIT and examination of the fertilization stage were carried out on superovulated mice 1 day after mating. The mean RIT of mice with pronucleus stage ova was significantly (p less than 0.01) higher than that of mice with sperm-penetrated ova. EPF was considered to appear in the maternal peripheral blood at the pronucleus stage.

Animals↗
PubMed1990

Biosynthesis and secretion of the hatching enzyme during sea urchin embryogenesis.

The hatching enzyme secreted by the blastula stage sea urchin embryo proteolyzes the fertilization envelope, thereby allowing the embryo to hatch. Using an assay that measures fertilization envelope degradation, we have purified the hatching enzyme by ion-exchange and affinity chromatography from the hatching medium of Strongylocentrotus purpuratus embryos. The hatching enzyme was found to be a 33-kDa metalloprotease that exhibited a substrate preference for only a minor subset of proteins in the fertilization envelope. Secretion of the hatching enzyme by blastula stage embryos occurred during the 2-h period prior to hatching. The hatching enzyme was initially secreted as a 57-kDa protein, but during purification it was converted to the 33-kDa form. Biosynthesis of the hatching enzyme began at the late morula/early blastula stage up to 6 h before secretion. Experiments using the ionophore monensin suggest that the lag between synthesis and secretion of the hatching enzyme by the blastula stage embryos may be a result of a slow constitutive secretory process.

Animals↗