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Results for “Fecundability”

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At least 955 records · Page 53Linked to original sources
PubMed1986

Effect of three pyrethroids on blood feeding and fecundity of Aedes aegypti.

Caged Aedes aegypti were exposed to a range of concentrations of d-phenothrin, d-allethrin and tetramethrin in a wind tunnel. Mortality, blood engorgement and egg production among these mosquitoes and their progeny were recorded. Tetramethrin was the most effective (LC50 of 0.0017%), followed by d-phenothrin (LC50 0.0031%) and d-allethrin (LC50 0.01%). Blood engorgement was decreased by treatment with each pyrethroid at the high concentration (0.002%, 0.003% and 0.01% respectively). Treatment with d-phenothrin or d-allethrin decreased egg production, but tetramethrin increased oviposition. These effects had ceased in the F2.

Aedes↗
PubMed1987

Effects of gamma radiation on development, sterility, fecundity, and sex ratio of Dermanyssus gallinae (DeGeer) (Acari: Dermanyssidae).

Protonymphal Dermanyssus gallinae were irradiated with 0.50, 0.75, 1.0, 3.0, and 6.0 krad of gamma radiation and subsequently monitored regarding their developmental, feeding, and mating success. Also, sex ratios of adults treated as protonymphs were recorded as were sex ratios of embryos and F1 adults produced by these adults. Doses up to 1.0 krad did not prevent development of treated protonymphs to the adult stage or stop mating. Three krad reduced the number of treated protonymphs attaining adulthood and 6.0-krad treatment prevented all mites from developing to the adult stage. Egg (embryo) production was normal for mites treated with 0.50 krad, but significantly curtailed by doses of 0.75 krad and greater. Radiation doses used in this study did not appear to affect the normal variable sex ratios observed in untreated mites.

Animals↗
PubMed1986

Winter survival of third stage Trichostrongylus colubriformis larvae: effects on infectivity and fecundity of adult worms.

Two groups of six lambs were fed with grass cut from two plots which had been contaminated by spreading Trichostrongylus colubriformis larvae. One plot received larvae in December, the other in April. The post mortem examination results showed that the infectivity of overwintering larvae was significantly higher than that of fresh larvae. An inverse relationship was demonstrated between infectivity of larvae and egg production of adult worms developed from these larvae. The results are compared with those obtained under laboratory conditions.

Animals↗
PubMed1985

Effects of caffeine and theophylline on the fecundity of four lepidopteran species.

Effects of secondary plant metabolites (caffeine and theophylline on reproduction of lepidopteran species were studied using Bombyx mori, Spodoptera litura, Danaus chrysippus and Catopsilia crocale as test organisms. Reproductive potential (ovary length and egg number) was significantly reduced in the lepidopterans receiving caffeine/theophylline treated leaves in comparison to the control. Protein and energy contents in the egg of the moths showed remarkable decrease with increasing concentrations of secondary plant metabolites in the feed. However, fat content remained almost constant in the egg of control and experimental animals.

Animals↗
PubMed1985

[Influence of the photoperiod on the production and fecundity of spermatozoa in the adult Ile-de-France ram].

Two groups, A and B, of 5 adult Ile-de-France rams each of the same age were exposed for 52 weeks (October 1975 to October 1976) to an artificial light regime reproducing natural variations of daylength (DL). In group A, DL increased from 8 to 16 h during the first 26 weeks and then decreased. In group B, DL varied in an opposite manner. Light intensity was constant (300 lux/m2) and ambient temperature was controlled (20 +/- 4 degrees C). The rams were collected using an artificial vagina twice weekly (2 X 2 ejaculates/male/week) during the whole experimental period (EP). The volume and concentration of each ejaculate were recorded. The pH of the raw semen was also measured on the first ejaculate once a week or every two weeks, according to material possibilities. The unselected ejaculates of all rams were used for artificial insemination (AI) on the same days in the same flocks between January and October 1976. AI (980 ewes) was always carried out after oestrus synchronization (FGA + PMSG). Amongst these ejaculates, some (3 ejaculates/male/group/period) could be used for both in vitro (pH) and in vivo (AI) measurements: - Weekly sperm production (SP) varied in an opposite manner in both groups during the whole EP. In group A, minimal (10.6 +/- 4.0.10(9) and maximal (25.5 +/- 5.1.10(9] levels were reached from weeks 12 to 28 and weeks 38 to 52, respectively. In group B, SP was maximal (21.8 +/- 2.3.10(9] from weeks 9 to 24 and minimal (12.7 +/- 5.2.10(9] from weeks 36 to 49. The differences between rams were significant within periods of high and low production. - The sperm pH was somewhat higher in both groups when DL increased and vice-versa. Fertility after AI was higher with rams exposed to short days than with rams exposed to long days (65.7 vs 56.7%; P less than 0.01). The season of AI had no effect on mean fertility (61.0 vs 62.3% for ewes inseminated from January to June and from July to October, respectively), whatever the DL. No correlation was found between the pH of the sperm and its fertilizing ability. From January to April, a highly significant correlation existed between fertility and prolificacy in the 10 rams (r = + 0.607). These results show that photoperiodism has an important effect on both ejaculated sperm production and fertility in rams.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1979

Seasonal migration and seasonal variation in fecundability: effects on birth rates and birth intervals.

Seasonal patterns in conception rates have been documented in several recent studies. In this paper, a mathematical model of the reproductive process is developed through which the impact of such variation in conception rates is assessed. It is found that the effect on fertility can be quite substantial, but that the birth rate when seasonal variation is occurring is approximated well by the birth rate calculated when conception rates are constant at their mean. These results indicate that further documentation of seasonality in conception rates and exploration of the causes of these patterns and their change is an important area for demographic research.

Birth Rate↗