Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Net Reproduction Rate”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed2005

Resistance cost of a cytochrome P450 herbicide metabolism mechanism but not an ACCase target site mutation in a multiple resistant Lolium rigidum population.

Costs of resistance are predicted to reduce plant productivity in herbicide-resistant weeds. Lolium rigidum herbicide-susceptible individuals (S), individuals possessing cytochrome P450-based herbicide metabolism (P450) and multiple resistant individuals possessing a resistant ACCase and enhanced cytochrome P450 metabolism (ACCase/P450) were grown in the absence of mutual plant interaction to estimate plant growth traits. Both P450 and ACCase/P450 resistant phenotypes produced less above-ground biomass than the S phenotype during the vegetative stage. Reduced biomass production in the resistant phenotypes corresponded to a reduced relative growth rate and a lower net assimilation rate and rate of carbon fixation. There were no significant differences between the two resistant phenotypes, suggesting that costs of resistance are associated with P450 metabolism-based resistance. There were no differences in reproductive output among the three phenotypes, indicating that the cost of P450 resistance during vegetative growth is compensated during the production of reproductive structures. The P450-based herbicide metabolism is shown to be associated with physiological resistance costs, which may be manipulated by agronomic management to reduce the evolution of herbicide resistance.

Acetyl-CoA Carboxylase↗
PubMed1995

Acceleration of 13C-labelled photosynthate partitioning from leaves to panicles in rice plants exposed to chronic ozone at the reproductive stage.

To investigate the effects of low (0.05 micromol/mol) and relatively low (0.10 micromol/mol) concentrations of ozone on photoassimilate partitioning, rice plants grown in a water culture were fed with (13)C-labelled carbon dioxide at the reproductive stage in an assimilation chamber with constant concentration of (12)CO(2) and (13)CO(2). Rice plants were exposed to ozone 4 weeks before and 3 weeks after (13)CO(2) feeding. The dry weight of whole plants decreased with increasing ozone concentration, whereas net photosynthetic rate (apparent CO(2) uptake per unit leaf area) was unaffected, compared with the control, at the time of (13)CO(2) feeding. Dry matter distribution into leaf sheaths and culms was reduced more than that into leaf blades by ozone exposure. Although panicle dry weight per plant was reduced by ozone, the percentage of panicle dry weight to the whole plant tended to increase considerably. Exposure to ozone accelerated translocation of (13)C from source leaves to other plant parts. Partitioning of (13)C to panicles and roots was higher under ozone treatment than in the control. Respiratory losses of fixed (13)C from plants tended to decrease under treatment with ozone. The increase in photoassimilate partitioning in panicles can be considered to be an acclimation response of rice plants to complete reproductive stage under the restricted biomass production caused by ozone.

Journal Article↗
PubMed2005

Bayesian population dynamics of interacting species: great gerbils and fleas in Kazakhstan.

We propose a discrete-time Bayesian hierarchical model for the population dynamics of the great gerbil-flea ecological system. The model accounts for the sampling variability arising from data originally collected for other purposes. The prior for the unknown population densities incorporates specific biological hypotheses regarding the interacting dynamics of the two species, as well as their life cycles, where density-dependent effects are included. Posterior estimates are obtained via Markov chain Monte Carlo. The variance of the observed density estimates is a quadratic function of the unknown density. Our study indicates the presence of a density-dependent growth rate for the gerbil population. For the flea population there is clear evidence of density-dependent over-summer net growth, which is dependent on the flea-to-gerbil ratio at the beginning of the reproductive summer. Over-winter net growth is favored by high density. We estimate that on average 35% of the gerbil population survives the winter. Our study shows that hierarchical Bayesian models can be useful in extracting ecobiological information from observational data.

Animals↗
PubMed1995

Use of prostaglandin F2 alpha as a postpartum reproductive management tool for lactating dairy cows.

This study compared three programs for reproductive management of the postpartum period for reproductive performance and net economic benefit within three dairy herds (n = 1624 cows). Cows on one program received PGF alpha injection at 25 to 32 d postpartum for reproductive therapy, and cows on a second program received additional PGF2 alpha at 39 to 46 d postpartum for synchronization of estrus. These programs were compared with a postpartum program of rectal palpation based on veterinary intervention. Survival analysis indicated that cows receiving PGF2 alpha for reproductive therapy and synchronization of estrus had an 11% higher rate of first AI and 10% higher rate of pregnancy than did cows receiving the rectal palpation. No differences existed between the cows receiving rectal palpation and those receiving the PGF2 alpha. Because overall conception rates and conception rates at first AI did not differ among programs, the improved reproductive performance of cows receiving PGF2 alpha for both therapy and synchronization may be attributed to greater synchronization of estrus, which resulted in improved estrus detection. A partial budget indicated that the PGF2 alpha programs were less expensive than the rectal palpation program. When PGF2 alpha was used for postpartum reproductive therapy and synchronization of estrus, reproductive performance and net economic benefit were increased compared with those of the other programs.

Animals↗
PubMed1981

Vaginal bleeding disturbances associated with the discontinuation of long-acting injectable contraceptives. From the World Health Organization Special Programme for Research, Development, and Research Training in Human Reproduction; Task Force on Long-acting Systemic Agents for the Regulation of Fertility.

A randomized comparative trial of 832 women receiving norethisterone oenanthate (NET-OEN) and 846 women receiving depot medroxyprogesterone acetate (DMPA) injections at 12 week intervals was conducted in 10 centers. The pregnancy rate with NET-OEN was significantly higher than with DMPA. The termination rate for amenorrhoea was substantially lowe with NET-OEN than DMPA, whereas the discontinuation rates for bleeding problems were similar with the two drugs. Analysis of bleeding patterns among continuing and discontinuing users suggests that women tolerated frequent bleeding episodes, but found prolonged bleeding or prolonged bleeding-free intervals unacceptable. Bleeding for more than 30 days during an injection interval and complete amenorrhoea for a whole injection interval were jointly associated with 43.7% of all terminations among NET-OEN users and 64.5% of all terminations among DMPA users. In future efforts to improve the acceptability of long-acting injectable contraceptives, more attention should be given to the control of prolonged amenorrhoea and prolonged bleeding.

Amenorrhea↗
PubMed1987

Biotechnology. The key to improved animal production?

Biotechnology will influence the reproductive performance of cattle in a number of different ways. In animals breeding, embryo transfer has already had a significant impact on the way in which genetic selection of animals is performed. If other technologies such as embryo splitting, in vitro fertilization, cloning, and sex selection are superimposed on conventional embryo transfer, genetic gains will be achieved at an extremely rapid rate. The net result be a rapidly changing animal population in which genetic gains are maximized. Transgenic animals with altered genetic make-up will also have a dramatic effect on animal production. The general introduction of such animals will be slow and the cost to produce them will be enormous, as conventional selection and progeny testing will be needed to ensure that the "new" introduced genes are functional and do not have detrimental side effects. Simple, sensitive assays of hormones and proteins developed using biotechnology will aid in the monitoring of reproductive performance of animals.

Animals↗
PubMed1993

Genetic and economic analyses of sow replacement rates in the commercial tier of a hierarchical swine breeding structure.

Commercial-level sow replacement rates were investigated for a 10-yr planning horizon using a stochastic life-cycle swine production model. A three-tiered breeding structure was modeled for the production of market hogs in a three-breed static crossing scheme. Growth and reproductive traits of individual pigs were simulated using genetic, environmental, and economic parameters. Culling was after a maximum of 1, 5, or 10 parities in commercial levels within 1- and 5-parity nucleus and 1-, 5-, and 10-parity multiplier combinations. Yearly changes and average phenotypic levels were computed for pig and sow performance and economic measures. For growth traits, greater commercial level response was for systems with higher sow replacement rates, 110 to 115% of lowest response. Phenotypic changes in net returns ranged from $.85 to 1.01 x pig-1 x yr-1. Average growth performances were highest for systems with greatest genetic trend. Highest kilograms.sow-1 x year-1 finished was for 10-parity commercial alternatives. System differences in total costs and returns per pig resulted primarily from differences in replacement costs. Removal of the gilt system from analyses often reduced ranges among systems for economic measures by more than 70%. Systems with the lowest commercial replacement rates were most profitable. Within these systems, those with higher genetic change had highest net returns. For high replacement rates, no more than 175% of market value could be paid for gilts, but with lower sow replacement rates commercial units could justify as much as 450%.

Adipose Tissue↗
PubMed1991

Heterogeneities in transmission rates and the epidemiology of schistosome infection.

Previous theoretical studies have suggested that heterogeneities in transmission rates can have significant effects on the epidemiology of parasite infections. However, the magnitude of these effects in practice remains uncertain because of the difficulty of quantifying such heterogeneities under natural conditions. In this paper we consider the effects of heterogeneous rates of contact with infective water bodies on the basic reproductive rate, R0, of human schistosomes. In particular, we examine the theoretical effects of differences in the distribution of contacts among individuals and among sites. We find that an individual's contribution to R0 depends not only on the net contact rate but also on how these contacts are distributed among sites--the contact pattern. Our analysis of field data suggests a substantial impact of heterogeneous contact rates on R0 in practice. Significant reductions in R0 may be possible if schistosomiasis control efforts are targeted at certain sites and, especially, certain individuals.

Animals↗
PubMed2026

Accounting for voluntary waiting period changes in US dairy herds: Adjusting daughter pregnancy rate and introducing first-service to conception.

The genetic evaluation of female fertility traits in dairy cattle in the United States has progressed over the past 2 decades, with 4 additional traits integrated into the national evaluation system since the introduction of daughter pregnancy rate (DPR) in 2004. However, concerns have arisen in the dairy sector, with reports of producers extending the voluntary waiting period (VWP), which is the time of initial breeding after calving, due to more persistent lactation yields. Since its inception, DPR calculations in the US evaluation have assumed a fixed 50-d VWP, which may not reflect modern reproductive strategies. Furthermore, producers may determine that some of their cows should have their VWP extended while others may follow the standard time. A re-evaluation of the current female fertility evaluation is necessary to ensure traits align with current management practices. Therefore, this study explores the addition of a potential new trait, First Service to Conception (FSC), along with a revised DPR formula that permits more flexibility with VWP. About 32 million records from the National Cooperator Database, covering 5 major dairy breeds (2003-2023), were used for this study. Data for cows calving before 2003 were unavailable because insemination records were not recorded prior. The findings suggest FSC enhances female fertility evaluations, providing a more comprehensive reproductive assessment independent of VWP. Another approach was an adjustment to the DPR calculation (DPRadj) to account for herd VWP on a herd-year and lactation group basis. The mean DPR value was 45.06%, while DPRadj increased the mean value to 52.58%. The mean FSC was 62.64 d. In an analysis using first lactation cows for cow traits and heifers for heifer traits, genetic correlations of FSC with other fertility traits were 0.97 with Cow Conception Rate (CCR) and DPR, 0.98 with DPRadj, 0.40 with Heifer Conception Rate (HCR), and 0.32 with Early First Calving (EFC). Predicted transmitting abilities (PTA) were calculated to assess the implications of adding FSC to, or replacing DPR with DPRadj within the CDCB multi-trait evaluation index, Net Merit $ (NM$). The highest correlation among the top 10% of bulls occurred when replacing DPR with DPRadj (0.99). Adding FSC to the original model reduced the latter correlation to 0.88, which indicates slight re-ranking of top bulls. Among animals with PTA reliability above 50%, the lowest correlation was between the original index and the index replacing DPR with FSC (0.95). This work advances genetic evaluation in dairy cattle, improving reproductive efficiency and productivity.

daughter pregnancy rate↗
PubMed2004

Vermistabilization of textile mill sludge spiked with poultry droppings by an epigeic earthworm Eisenia foetida.

Investigations were made to explore the potential of an epigeic earthworm Eisenia foetida to transform textile mill sludge spiked with poultry droppings in to value added product, i.e., vermicompost. The growth and reproduction of E. foetida was monitored in a range of different feed mixtures for 77 days in the laboratory under controlled experimental conditions. The maximum growth was recorded in 100% cow dung (CD). Replacement of poultry droppings by cow dung in feed mixtures and vice versa had little or no effect on worm growth rate and reproduction potential. Worms grew and reproduced favourably in 70% poultry droppings (PD)+30% solid textile mill sludge (STMS) and 60% PD+40% STMS feed mixtures. Greater percentage of STMS in the feed mixture significantly affected the biomass gain and cocoon production. Net weight gain by earthworms in 100% CD was 2.9-18.2 fold higher than different STMS containing feed mixtures. The mean number of cocoon production was between 23.4+/-4.65 (in 100% CD) and 3.6+/-1.04 (in 50% PD+50% STMS) cocoons earthworm(-1) for different feed mixtures tested. Vermicomposting resulted in significant reduction in C:N ratio and increase in nitrogen and phosphorus contents. Total potassium, total calcium and heavy metals (Fe, Zn, Pb and Cd) contents were lower in the final product than initial feed mixtures. Our trials demonstrated vermicomposting as an alternate technology for the recycling and environmentally safe disposal/management of textile mill sludge using an epigeic earthworm E. foetida if mixed with poultry droppings.

Animals↗
PubMed1992

Cost-benefit evaluation of on-farm milk progesterone testing to monitor return to cyclicity and to classify ovarian cysts.

The effect of using on-farm milk progesterone testing to monitor return to cyclicity after parturition and to classify correctly and to treat cystic cows was evaluated using modeling and simulation. The test was evaluated assuming low and high accuracies of progesterone measurement, first breeding policy of 40 d, average estrus detection rate of 55%, and an average fertility rate of 55%. Three testing schemes (starting milk progesterone testing on d 30, 40, or 50 after parturition) were compared against a control to evaluate the effect of monitoring return to cyclicity on cows' reproductive and economic performance. For this purpose, the use of the test was an economically justifiable management intervention. Starting to test on d 30 after parturition was the most effective scheme, reducing days open by 18 d, replacement rate by 2.4%, and increasing net return per cow per year by $11. Starting to test on d 50 postpartum was not economically justifiable. Accuracy of the test, within the range used in this study, was unimportant. Testing was most profitable in herds with low fertility and low efficiency of estrus detection. The use of the test to classify follicular and luteal cysts and to select the appropriate therapy was not economically justifiable because of the low proportion of cystic cows and the high variation in response to therapy.

Animals↗
PubMed2006

Evaluation of systems for reducing the transmission of porcine reproductive and respiratory syndrome virus by aerosol.

The purpose of this study was to compare 3 methods for the reduction of aerosol transmission of Porcine reproductive and respiratory syndrome virus (PRRSV): high-efficiency particulate air (HEPA) filtration, low-cost filtration, and ultraviolet light (UV) irradiation. The HEPA-filtration system involved a pre-filter screen, a bag filter (EU8 rating), and a HEPA filter (EU13 rating). The low-cost-filtration system contained mosquito netting (pre-filter), a fiberglass furnace filter, and an electrostatic furnace filter. For UV irradiation, a lamp emitted UVC radiation at 253.7 nm. No form of intervention was used in the control group. The experimental facilities consisted of 2 chambers connected by a 1.3-m-long duct. Recipient pigs, housed in chamber 2, were exposed to artificial aerosols created by a mechanically operated mister containing modified live PRRSV vaccine located in chamber 1. Aerosol transmission of PRRSV occurred in 9 of the 10 control replicates, 8 of the 10 UVC-irradiation replicates, 4 of the 10 low-cost-filtration replicates, and 0 of the 10 HEPA-filtration replicates. When compared with no intervention, HEPA filtration and low-cost filtration significantly reduced PRRSV transmission (P < 0.0005 and = 0.0286, respectively), whereas UV irradiation had no effect (P = 0.5). However, low-cost filtration and UV irradiation were significantly less effective (P = 0.043 and P < 0.0005, respectively) than HEPA filtration. In conclusion, under the conditions of this study, HEPA filtration was significantly more effective at reducing aerosol transmission of PRRSV than the other methods evaluated.

Aerosols↗
PubMed1997

Seasonal courses of CO(2) exchange and carbon balance in fruits of Cinnamomum camphora.

Carbon dioxide exchange in fruits of Cinnamomum camphora Sieb. was followed over a growing season from July to December 1992. Dark respiration was exponentially related to temperature, with a Q(10) value near 2. Light dependence of photosynthetic CO(2) refixation, i.e., the ratio of gross photosynthesis to dark respiration, was approximated by a hyperbolic function. Seasonal variation in maximum CO(2) refixation capacity ranged between 52 and 174%, reaching a maximum in early August. Daily photosynthetic CO(2) refixation ranged between 17 and 51% over the growth period. We evaluated seasonal variation in translocation rate to the fruit on the basis of the seasonal rates of gross photosynthesis, dark respiration and increase in fruit dry weight, and used the results to develop a simple carbon flow model of fruit development. Seasonal changes in translocation rate paralleled those in fruit growth rate, with two peaks during the periods before and after September. Seed formation took place in the period between the two peaks. The relationship between fruit growth rate and translocation rate was approximated by a linear function. The carbon flow model estimated that, over the reproductive period, the amount of assimilate translocated to each fruit was 377.2 mg dry weight, of which 58.5% was accounted for by weight growth and 41.5% was consumed by net respiration. Carbon dioxide refixation accounted for 22.9% of the carbon balance of the fruit.

Journal Article↗
PubMed2000

The evolution of polyandry: multiple mating and female fitness in insects.

Theory suggests that male fitness generally increases steadily with mating rate, while one or a few matings are sufficient for females to maximize their reproductive success. Contrary to these predictions, however, females of the majority of insects mate multiply. We performed a meta-analysis of 122 experimental studies addressing the direct effects of multiple mating on female fitness in insects. Our results clearly show that females gain directly from multiple matings in terms of increased lifetime offspring production. Despite a negative effect of remating on female longevity in species without nuptial feeding, the positive effects (increased egg production rate and fertility) more than outweigh this negative effect for moderate mating rates. The average direct net fitness gain of multiple mating was as high as 30-70%. Therefore, the evolutionary maintenance of polyandry in insects can be understood solely in terms of direct effects. However, our results also strongly support the existence of an intermediate optimal female mating rate, beyond which a further elevated mating rate is deleterious. The existence of such optima implies that sexual conflict over the mating rate should be very common in insects, and that sexually antagonistic coevolution plays a key role in the evolution of mating systems and of many reproductive traits. We discuss the origin and maintenance of nuptial feeing in the light of our findings, and suggest that elaborate and nutritional ejaculates may be the result of sexually antagonistic coevolution. Future research should aim at gaining a quantitative understanding of the evolution of female mating rates. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1992

Age structure of horn fly (Diptera: Muscidae) populations estimated by pterin concentrations.

Pterins accumulate in the head capsules of horn flies, Haematobia irritans irritans (L.), as a linear function of time and temperature. Pterin concentrations were used to estimate chronological ages and to establish correlations between chronological age and ovarian development and reproductive success in 12 horn fly populations in 1988 and 1989. Male ages were estimated spectrofluorometrically. There were statistically significant differences between years in population age structure measured by pterins. Survival rates estimated from pterin concentration distributions were consistent with a one-parameter exponential model with constant survival rate. Mean daily survival rates were 0.81 for females and 0.84 for males in 1988 and 0.66 and 0.75 in 1989. Mean lifetime egg production was approximately 26 eggs per female in 1988 and 8 in 1989. Female reproductive success was close to the maximum possible, i.e., there were no net delays in oviposition. Analysis of gonotrophic age distributions provided survival estimates that suggested an increasing risk of mortality with age or age-related biases in sampling.

Aging↗
PubMed1983

Short and long term effects of root and shoot chilling of ransom soybean.

The immediate short term effects on some physiological processes and the long term effects on morphology and reproductive development of root- and shoot-chilled soybeans (Glycine max L. cv Ransom) were studied. Roots or shoots of 16- or 17-day-old plants were chilled at 10 degrees C for one week, and then rewarmed to 25 degrees C. Leaf elongation rate, net CO(2) uptake rate, and stomatal conductance decreased during root or shoot chilling. Root chilling had only temporary effects on water relations, while shoot chilling caused large changes in potentials during chilling. Most processes measured returned to control levels after two days of rewarming. Root-chilled plants harvested 90 days after emergence were similar in morphology and seed weight to controls. Shoot-chilled plants showed a large increase over controls in axillary branch growth, but an early abortion of flowers and a delayed resumption of flowering caused a 78% reduction in seed weight. Root chilling in this study was found to have little or no long term effect on the plants, while shoot chilling caused significant changes in vegetative morphology, and a delay in flowering and subsequent pod filling.

Journal Article↗
PubMed1984

Effect of low and high fill diets on dry matter intake, milk production, and reproductive performance during early lactation.

Feedstuffs analyzed for rate and extent of ruminal neutral detergent fiber disappearance were used to formulate two diets that differed for predicted time required for ruminal clearance of neutral detergent fiber. Diets with slow and fast estimated disappearance rate of neutral detergent fiber were termed and high and low fill, respectively. For both diets, crude protein, acid detergent fiber, neutral detergent fiber, net energy of lactation, and soluble protein were similar. Twenty-eight lactating cows were limit fed the rations 2 wk prior to calving, then fed for ad libitum consumption until 8 wk after calving. Cows fed low fill produced more milk (30.3 vs. 26.3 kg) and milk protein (.97 vs. .78 kg) and had higher incidence of short estrous cycles and fewer acyclic cows by 8 wk postpartum than cows offered high fill. Dry matter intake, fat-corrected milk yield, daily fat production, and solids-not-fat did not differ between diets. Rumen fermentation measurements for pH and ammonia-nitrogen concentrations were also not different between diets. Cows fed low fill tended to have higher rates of solids and liquid turnover and lower total dry matter in the rumen compared with cows fed high fill. Low ruminal pH on both diets as well as other physiological mechanisms may have been responsible for failure of rates of neutral detergent fiber disappearance to affect intake of dry matter.

Animals↗
PubMed2003

Overwintering in Drosophila melanogaster: outdoor field cage experiments on clinal and laboratory selected populations help to elucidate traits under selection.

Insects can adapt to temperate environments by increasing levels of resistance to cold conditions over winter and/or altering reproductive patterns to focus reproduction in favourable conditions. In temperate areas, Drosophila melanogaster persists over winter at the adult stage. A previous experiment, conducted with flies kept in outdoor population cages in the temperate winter, indicated that temperate populations produced more eggs than did tropical populations following an abrupt increase in reproduction in late winter. In contrast, the tropical populations produced more eggs prior to the increase. Both patterns resulted in a higher net number of surviving offspring for temperate populations. Here we again examine the clinal pattern in reproduction using outdoor cages, this time held under tropical winter conditions. In this environment, surprisingly, egg production was higher and on average earlier in populations originating from temperate areas. However, mortality rates also increased with latitude of origin, and the relationship of lifetime egg production to latitude should therefore be measured. To test the role of altered pattern of egg production per se in the reproductive advantage of temperate populations in the temperate winter, we tested the performance of laboratory lines selected for altered reproductive patterns, under temperate winter conditions. Lines selected for high early fecundity exhibited this characteristic in the field cages and lines selected for late reproduction exhibited a relatively high fecundity in spring. The timing of the abrupt increase in egg production was identical in these sets of lines and occurred at the same time in recently collected populations, suggesting evolutionary conservation of the switch. These findings suggest that changes in early and late reproduction per se determine adaptation to temperate winter conditions, and illustrate how laboratory selection lines can be used to understand traits underlying adaptive shifts in field performance.

Adaptation, Physiological↗