Length of gestation in the guinea pig with data on the frequency and time of abortion and stillbirth

Goy, Robert W.; Hoar, Richard M.; Young, William C.

doi:10.1002/ar.1091280408

Cited by 41 publications

(14 citation statements)

References 5 publications

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“…For example, Goy, Hoar & Young (1957) showed that in a pure-bred strain of guinea-pigs the mean gestation length was 69-9 days for a litter size of one, whereas it was 65-3 days for a litter size of six. The litera¬ ture on this phenomenon in domestic animals is reviewed by Clegg (1959), who cites evidence for its occurrence in cattle, sheep, goats and rabbits.…”

Section: Discussionmentioning

confidence: 99%

Regulation of the Gestation Period in Mice

Biggers¹,

Curnow²,

Finn³

et al. 1963

Reproduction

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Unilateral ovariectomy in the mouse produces little if any reduction in the total number of eggs shed. Almost all the resulting embryos implant in the uterine horn of the intact side, which is therefore almost twice as crowded as normal. However, the operation does not alter the very significant inverse regression of gestation length on litter size. The duration of gestation in the mouse must therefore be influenced by the total number of conceptuses in the female, rather than by the number of conceptuses in the more crowded uterine horn.Occluding one Fallopian tube, which reduces the number of foetuses to about half but does not affect the number of corpora lutea, is also without effect on the inverse regression of gestation length on litter size. The duration of gestation in the mouse must therefore be related to the number of conceptuses directly, rather than through the number of corpora lutea.The results are consistent with the view that some humoral factor from the placentae and/or foetuses regulates the duration of pregnancy. An analysis of the literature on the endocrinology of pregnancy in the mouse strongly implicates oestrogens. This suggestion must remain speculative until the presence and nature of placental oestrogens in the mouse have been studied.The inverse relation between duration of gestation and litter size is well documented in many species. The sow, however, is a notable exception, since not one of several studies has demonstrated the phenomenon. The reasons for this are still obscure.

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Section: Discussionmentioning

confidence: 99%

Regulation of the Gestation Period in Mice

Biggers¹,

Curnow²,

Finn³

et al. 1963

Reproduction

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“…Guinea pigs produce large young which they bear after 65-72 days of pregnancy (Goy, Hoar & Young, 1957). Young are extremely precocial and begin to forage on normal food within the first days of life.…”

Section: Introductionmentioning

confidence: 99%

Energy allocation in reproducing and non‐reproducing guinea pig (Cavia porcellus) females and young under ad libitum conditions

1996

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With 9 figures in the text) Increase in body mass is an overall measure of growth which hides the dynamics of changes in body components. A study of the allocation of resources to growth versus reproduction is particularly interesting in guinea pigs (Cuviuporcellus) where females mature early in the growth phase and produce highly precocial young while still growing rapidly.In order to get information on energy allocation in guinea pigs, fat-free mass (FFM) of young (1-30 days) and adult females (reproducing vs. non-reproducing) was determined by measuring Total Body Electrical Conductivity (TOBEC; indexed by TOBEC#) which was calibrated by Soxhlet extraction.FFM was predictable from body length alone, but was best predicted as a function of (TOBEC#*length)' '. Prediction was further improved by separating the data into two sets, for animals of < 23 cm and of > 23 cm body length. Fat and total body water (TBW) can also be determined from TOBEC#, but the reliability of fat determinations is low unless samples of 5-10 equally treated animals can be averaged. The formula developed by for the estimation of TBW has frequently been used for all kinds of mammals, but is shown consistently to underestimate TBW even in guinea pigs. Using our calibrations, we studied the development of FFM and body fat in young guinea pigs from birth to 30 days, and the development of FFM and fat stores in reproducing, primiparous, and non-reproducing females of equal age.Young were born with about 11% fat. Young in large litters (3-5) had relatively and absolutely less fat reserves than young in small litters. In eight young measured on days 1, 3, and 5, fat declined until day 3 and returned to the mass at birth on day 5. Fat mass increased slowly during the lactation period, until day 20, and faster thereafter in weaned young. Relative to body mass, fat decreased from 11.2% at birth to 9.3% on day 30, with a minimum of 6.6% on day 20. Mass of fat on day 30 was independent of litter size. FFM began to grow linearly from day 5 onwards. Body water in FFM varied with age in an inverted U-shaped pattern.Reproducing females grew in FFM at equal rates to non-reproducing females, but deposited less than half as much fat until day 210, by which time they had had two litters. Under ad libitum food conditions and a mild thermal regime, reproducing females allocated as much of the available resources to growth in FFM as non-reproducing females, but reduced storage of fat, instead producing biomass of precocial young.

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“…In guinea-pigs, the incidence of still-births and neonatal deaths has been found to increase with litter size (Haines, 1931;Goy et al, 1957). However, there was no significant effect of mastectomy on litter size at delivery (3-6 + 0-20 in 16 intact; 40 + 017 in 12 mastectomized, median 4 in both) or on total weight of young (including still-born) (360 ± 23-5 g and 397 + 25-3 g, respectively).…”

Section: Pregnancy and Parturitionmentioning

confidence: 99%

“…However, there was no significant effect of mastectomy on litter size at delivery (3-6 + 0-20 in 16 intact; 40 + 017 in 12 mastectomized, median 4 in both) or on total weight of young (including still-born) (360 ± 23-5 g and 397 + 25-3 g, respectively). The incidence of still-births has also been found to be higher with gestation periods longer and shorter than 69 days (Goy et al, 1957), but there was no significant effect of mastectomy on the length of pregnancy: the gestation period in 8 intact animals in which the time of mating was known was 68-8 + 0-49 (s.e.) days compared with 67-6 ± 0-43 days in 12 mastectomized (median 68 days in both).…”

Section: Pregnancy and Parturitionmentioning

confidence: 99%

Some effects of mastectomy on reproductive success in the guinea-pig

Peaker

Taylor²

1990

Reproduction

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Summary. Virgin guinea-pigs were mastectomized in two stages between 11 and 18 weeks of age and then mated, starting 19 weeks after final surgery. In the subsequent first pregnancy, the incidence of still-births and neonatal deaths was significantly higher in the mastectomized animals (6 out of 12 mothers (50%) and 14 out of 49 young (29%) compared with intact guinea-pigs (1 out of 15 mothers (7%) and 1 out of 58 young (2%)). There was no significant effect of mastectomy on litter size and weight or on gestation period. The still-born were not significantly different in weight from those born alive. A significant relation was found between maternal weight changes in the period 20 to 5 days before parturition and the occurrence of still-births and neonatal deaths; still-births were associated with a period of reduced weight gain. No effect of mastectomy on the length of the oestrous cycle was apparent but a significant increase in the incidence of non-pregnancy was found. The results provide further evidence that mastectomy influences reproductive success in the guinea-pig and suggest that parturition is a key process affected.

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Length of gestation in the guinea pig with data on the frequency and time of abortion and stillbirth

Cited by 41 publications

References 5 publications

Regulation of the Gestation Period in Mice

Regulation of the Gestation Period in Mice

Energy allocation in reproducing and non‐reproducing guinea pig (Cavia porcellus) females and young under ad libitum conditions

Some effects of mastectomy on reproductive success in the guinea-pig

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