Corpora Lutea Counts Research Articles

Relationship between uterine progesterone and fetal development in pigs.

The potential relationship between uterine arterial and venous concentrations of progesterone. and porcine fetal size and viability was examined. Sixteen Yorkshire gilts were laparotomizedat 27 to 37 days of gestation to count corpora lutea and embryos. Samples of blood were drawn from uterine arteries and veins at each embryonal location of 10 of the gilts but not from the six control guts. At 60 to 76 days of gestation, a second laparotomy was performed to determine rates of fetal survival and to draw blood samples from uterine vessels at all fetal locations in each of the 12 gilts remaining from the first surgery. The percentages of embryos surviving between first and second surgeries were 51.0% for the experimental gilts and 65.6% for the control gilts (P>0.05). Progesterone concentrations were higher in arteries than in veins at each fetal location at both surgeries (P<0.01).The disappearance or utilization of progesterone in the uterine tissues surrounding either normal or mummified fetuses was greater late in pregnancy compared with the early embryonic stage (P<0.05). Uterine arterial and venous progesterone concentrations were unrelated to fetal weight; however, fetal weight was correlated with arterial-venous differences. These data suggest that some of the progesterone entering the uterine arterial system is metabolized or utilized and does not reenter the uterine venous system and that this utilization may be related to fetal weight and stage of development.

Litter Size in Columbian Ground Squirrels (Spermophilus columbianus)

Measures of litter size, based on counts of corpora lutea, placental scars, embryos, and juveniles emerging from natal burrows, were determined from 181 Columbian ground squirrels ( Spermophilus columbianus ) collected in three areas in southwestern Alberta, Canada, and from observations of 88 litters that emerged in these areas. Most measures of litter size differed between areas and were lower at a high elevation site (2,170 m) than at the other two sites (elevation 1,500 m). We suggest that differences between areas may be related to timing of snow melt and onset of vegetative growth. Columbian ground squirrels have smaller litters than most other North American species of ground squirrel, perhaps reflecting different life history tactics.

The effect of time of mating on ovulation rate and potential lambing rate of Greyface ewes

ABSTRACTOver 2 years, 104 Greyface ewes were mated at a synchronized oestrus either in early October or early November. From late September until slaughter at return to service or between 4 and 7 weeks after mating, ewes were fed to maintain their body condition score as previously adjusted by differential group feeding on grass. Ovulation rate and potential lambing rate were derived from counts of corpora lutea and viable embryos at slaughter. Both rates were higher in the early-mated ewes in comparable body condition. Stress factors were implicated as contributing to the decline in ovulation rate with time, while ewes which failed to hold to first mating were largely responsible for the decline in potential lambing rate.

Fertility in Cheviot ewes. 2. The effect of level of pre-mating nutrition on ovulation rate and early embryo mortality in North and South Country Cheviot ewes in moderately-good condition at mating

ABSTRACTIn two experiments over 2 years, 57 North Country Cheviot and 82 South Country Cheviot hill ewes were differentially group-fed indoors over a 2-month period to achieve either good or moderate body con- dition. Over 5 weeks prior to mating, ewes in good condition were brought down in condition by restricted feeding and ewes in mod- erate condition were raised in condition by a high level of feeding. The ewes were thus in moderately-good condition at mating. After mating, ewes were maintained in this condition until killed either on return to service or at 29 ± 8 days for counts of corpora lutea and viable embryos.Ovulation rate in each breed was positively related to the level of pre-mating food intake at the condition level studied. Embryo mortality, as ova loss, was not influenced overall by the level of pre-mating food intake but loss of multiple-shed ova was greater than that of single-shed ova in ewes which had been on restricted feeding before mating. Although a greater proportion of ewes in the North Country Cheviot breed were not pregnant at slaughter, this could not be identified as a breed difference since the breeds were studied in different years.

Reproductive Performance of White-Tailed Deer in Iowa

Reproductive biology of the white-tailed deer ( Odocoileus virginianus ) in Iowa and the Nebraska-owned portion of DeSoto National Wildlife Refuge on the Iowa side of the Missouri River was determined from female reproductive organs of deer killed on highways and by hunters from 1959 to 1963, 1965, and 1966. Rut for fawn does extended from mid-November into early January but peaked between 3 to 18 December. Presence of corpora lutea indicated 82 percent of the fawns had ovulated. Corpora albicantia in ovaries of 1½-year-old does indicated that 65 percent of the fawns had breed successfully. The peak of breeding by 1½-year-old does was about 24 November, and for 2½-year-old does about 22 November. Fertilization frequency for does (all ages) that had been in estrus was 92 percent. A primary sex ratio for 178 embryos from 109 does of all ages was 1.23 males:1 female. Corpora lutea counts and fertilization rates indicated fawns from Iowa may produce up to 30 percent of the annual increment.

Short-term undernutrition and prenatal mortality in young and mature Merino ewes

SUMMARYPrenatal mortality was examined in 74 primiparous Merino ewes which, after hand mating to fertile rams on the second oestrus following synchronization, were allocated to two groups. One group of 38 ewes was confined to yards and restricted to approximately 30% of their maintenance requirement for 14 days while the other group of 36 remained at pasture. The degree and timing of prenatal loss was assessed by corpora lutea counts, pregnancy diagnosis about day 40, returns to service and lambing records.The mean ovulation rate was 1·06 and the 19-day non-return rate was 87·8%. Pregnancy failed in a higher proportion of the underfed ewes (45·0%) than in the control ewes (30·8%) but this difference did not reach significance. Of the ewes returning to service, significantly more did so with cycles longer than 19 days in the underfed group (9/12) than in the control group (2/8), indicating that in the latter stages, the treatment may have been detrimental to embryo survival.In a second experiment, ovulation rate and prenatal mortality, assessed as in the first experiment, were studied in 85 mature Merino ewes subjected to the following nutritional treatments: HH, control; HL, 30% submaintenance feeding for 14 days following mating; LH, 15% submaintenance feeding for 7 days prior to mating; LL, both submaintenance treatments.Acute undernutrition prior to mating (LH) had no effect on ovulation rate or prenatal mortality. Ovulation rates were low over all groups (mean 1·09) and thus precluded any valid examination of ovulation rate and body weight relationships. The right ovary was significantly more active in producing ova than the left in all groups (P &lt; 0·05). Although ova wastage was apparently higher in. the post-mating undernutrition groups (HL, 44%; LL, 48%; LH, 50%) than in the control group (HH, 35%), the differences were not significant. An increased incidence of extended (&gt; 19 days) first-return cycle lengths in group LL provided some evidence of induced prenatal mortality.In so far as the experiments can be considered together, they indicate that if body weights are comparable, primiparous 1½-year-old ewes are not necessarily more susceptible than mature ewes to prenatal mortality induced by severe short-term undernutrition.

The ecology of the deer mouse Peromyscus maniculatus in a coastal coniferous forest. II. Reproduction

The duration and intensity of reproduction in deer mice was followed for four seasons by live and dead trapping. Three populations living in different types of forest habitat had synchronous breeding seasons, although there were major differences between years in the time of onset and cessation of breeding and in the proportion of females in breeding condition. No consistent relationships were found between either density changes or the incidence of parasitism and reproductive phenology. In the absence of overt food fluctuations there was a relationship between unseasonable temperature changes and breeding. Sudden increases in temperature may have stimulated the onset of breeding but its cessation before the autumn equinox was always associated with a considerable decrease in temperature if this occurred after April. In 57 pregnancies the corpora lutea count was 4.75 ± 1.12 and embryo count was 4.52 ± 1.16. [Formula: see text].

The effect of condition at service and plane of nutrition in early pregnancy in the sow 1. Uterine and extra-uterine changes

SUMMARYTwelve sows (F) were fed 7·3 kg/day and twelve (T) 3·7 kg/day of a 16% crude protein (CP) diet for the last 5 weeks of an 8-week lactation, so that at the subsequent service F sows were heavier (16%) and in better condition.From service to slaughter 70 days later, sows received either 3·7 kg/day (H) or 1·8 kg/day (L) of a 15% CP diet, giving four treatment combinations; FH, FL, TH and TL.In pregnancy H sows gained more weight than L sows and, on the low plane, F sows gained more weight than T sows. Ovulation rate as measured by corpora lutea count at slaughter was higher for TH than TL sows and for FL sows than FH sows. A combination of low ovulation rate and high mortality rate gave fewer foetuses (10·0) in the TL sows than in sows on the other treatments (13·5). Similarly mean foetal weight and thus foetal litter weight was least in TL sows. Foetal membranes, uterine fluids and uterine wall were lighter at slaughter in T sows than F sows and lighter in L sows than H sows, those of TL sows being appreciably the lightest.The results indicate that when the sow is in poor condition at service, body reserves being depleted, the uterus and its contents become more vulnerable to adverse pregnancy nutrition.

Observations on the Reproductive Biology of Pseudomys (Rodentia: Muridae)

Certain anatomical and histological features of the reproductive system are described for the first time for three species of Pseudomys from mainland Australia— P. shortridgei, P. australis , and P. gracilicaudatus . All three species possess Cowper's glands, seminal vesicles, and prostates. Preputial glands occur in P. australis and P. gracilicaudatus . In P. gracilicaudatus , litter size, determined from corpora lutea counts, ranges from two to four, and ovulation appears to be suppressed during pregnancy. It is not known if any of the species experience a postpartum estrus, nor is the length of gestation known. Brief habitat descriptions are provided for each of the three species under consideration.

X-ray-induced dominant lethal mutations in male guinea-pigs, hamsters and rabbits

The yields of dominant lethal mutations in successive post-meiotic stages after X-ray doses to male guinea-pigs, rabbits and hamsters were compared with those after a similar dose to mice, by dissecting females pregnant by irradiated males and counting corpora lutea and live and dead embryos. After 500 rad X-rays guinea-pigs and rabbits both gave a lower yield of dominant lethals than the mouse, but they showed a similar pattern of relative sensitivity of germ cell stages, with spermatids more sensitive than mature spermatozoa. Hamsters, after a dose of 200 rad, gave a yield of dominant lethals from mature spermatozoa nearly as high as after 500 rad to mice, but the pattern of sensitivity was different, with nearly mature sperm and spermatids giving a lower yield, close to that expected after 200 rad to mice. Thus, in extrapolating from species to species account must be taken of different patterns of relative sensitivity of germ cell stages as well as of overall differences in sensitivity.

Microtus Population Biology; III. Reproductive Changes in Fluctuating Populations of M. ochrogaster and M. pennsylvanicus in Southern Indiana, 1965‐67

About 1,200 Microtus pennsylvanicus and 1,000 M. ochrogaster were collected over a 3—year period by sequential trapping of snap—trap lines in 15 grassland areas in southern Indiana. Peak densities were reached in 1966 for all but two of the populations studied. Reproductive data were obtained to determine whether weight at sexual maturity, pregnancy rate, living embryo production, prenatal mortality, and body weight varied in relation to fluctuations in numbers. The rate of winter breeding was high in both species of vole between the cyclic increase and cyclic peak years. Breeding was continued at a reduced level during the fall of the cyclic peak and was greatly reduced during the winter between the cyclic peak and decline. In both species sexual maturity occurred at higher weights in periods of peak population density and lower weights in periods of low density. Only heavy individuals remained fecund during the winter months of November—February. Sexual maturity was reached at the same weight in males and in females. Litter size was correlated with body size. In M. pennsylvanicus litter size was not significantly different in multiparous and primiparous females, and litter size remained constant in the summer breeding seasons of the increase, peak, and decline years. Difference between seasons was significant, the fall—winter—spring periods having a 14% lower litter size than the summer period. In M. ochrogaster living embryo counts were 25% lower during the period of cyclic peak in multiparous females than they were during the years of cyclic increase or decline. This observation was confirmed independently in a population that was out of synchrony. A decline in litter size was not associated with the year of cyclic decline in either species. Corpora lutea counts were correlated with body size. The pattern established for living embryo counts was nearly identical to the ovulation pattern. Prenatal mortality did not change significantly, either seasonally or yearly, and thus was not higher in the decline phase for either species. Testes weight and body weight were correlated. The testes weight of non—fertile Microtus pennsylvanicus differed little among the summers of population increase, peak, or decline. Testes development was inhibited during fall and winter. Fertile males taken during the summer of population peak and the summer of decline had heavier testes than males taken during the summer of increase. A midsummer drop in testes weight was observed during three breeding seasons. Non—fertile M. ochrogaster had only slightly reduced testes weight during the winter between the population increase and peak, but testes weight declined significantly during the winter following the population peak. Testes weights of fertile males changed little during the summer of population increase, but they increased steadily during the summer of population peak. A significant decline in testicular weight occurred during the winter following the population peak. High body weights were associated with peak populations in both species of Microtus. The pattern of change in weight distributions was similar to that described for other cyclic voles and lemmings.

The effect of mestranol on canine reproduction.

A single oral dose of mestranol (l7α-ethynylestradiol 3-methyl ether) was administered to two groups of eight adult female beagle dogs each on Day 6 or 21 after first acceptance of the male. Based on corpora lutea counts, embryonic loss was 95.5 and 67.3%, respectively, for the two treatment groups, and only 34.5% for the control. In a second study a group of 12 beagles were used to determine the effect of mestranol on ova transport. Nine bitches were dosed on Day 6 and the reproductive tracts were removed between 1 and 5 days later and three controls were examined on Day 11. Thirty-nine of a possible 56 ova were flushed from the tracts of the treated females and all but one were from the oviducts. Eighteen (46%) of the ova were degenerating. The controls produced 17 normal zygotes out of a possible 24, and all were flushed from the uteri. Mestranol apparently did not accelerate ova transport, and the possibility of both a direct effect on the ova and an indirect effect via a delay in ova transport is discussed.

Resorption in guinea pigs as estimated by counting corpora lutea: the problem of twinning.

AbstractNormal pregnant guinea pigs were killed on gestation days 12–20 and examined for implantation sites and resorbing embryos. Their ovaries were removed and serially sectioned, and the functioning corpora lutea counted for comparison with the number of conceptuses.It was found that a single corpus luteum was associated with two implantation sites with a frequency of 9.55%. Embryonic loss prior to implantation was 12.6% and the value for resorption following implantation varied from 5.8 to 7.2% depending on the time of killing and the method employed for determining resportion. A count of functioning corpora lutea facilitated the determination of embryonic loss prior to implantation, but offered little advantage over simpler techniques for determining resorption after implantation.

Chromosome abnormalities in early embryos of the pig.

This report presents the results of chromosome analysis of blastocysts collected and processed as previously described (McFeely, 1966) from seven gilts selected at random from the swine herd at the University of Pennsylvania. No records of parentage of the gilts were available, but as they consisted of various breeds and cross breeds from a variety of sources, it was assumed that they were not closely related. Two unrelated, pure bred, Yorkshire boars were used as sires. Chromosome analysis of peripheral blood leucocytes from all of the pigs did not reveal any abnormalities, nor were any physical defects observed in the animals. No immunization or drugs were administered at any time during the experiment, and no disease of consequence was noted. The recovery rate of blastocysts was 98% based on corpora lutea counts as indicative of

Corpora Lutea Variations of White-Tailed Deer

The reproductive tracts of 404 female white-tailed deer (Odocoileus virginianus) were studied for information on size, shape, and coloration of corpora lutea. Corpora lutea in fawns are regarded as regressing if they are less than 4.0 mm in diameter at the time when the rut for that age-class is nearing its end. In all age-groups of does where fetal membranes or embryos are present, corpora lutea smaller than 6.0 mm are regarded as regressing. These small ones are regarded as corpora lutea of an earlier heat and not as corpora lutea of the current pregnancy. Regressing corpora lutea of a previous ovulation also appear to have an irregular surface shape. Color is not a dependable criterion for differentiation of the two types of corpora lutea. During an investigation of reproduction in white-tailed deer in Iowa, information was obtained on the physical characteristics of their corpora lutea. In attempting to correlate fertilization rate with ovulation rate, difficulty has been encountered in differentiating corpora lutea of ovulation of a previous heat from corpora lutea of pregnancy. In sheep, corpora lutea of ovulation are formed in ruptured follicles within 4 days following ovulation (Asdell 1946:366-367) and are fully developed by the eighth day following ovulation (Harrison 1962:169). In deer, corpora lutea of ovulation begin regressing after about 14-15 days (Cheatum 1949:285) if fertilization does not occur. When fertilization and implantation take place, corpora lutea of ovulation persist as corpora lutea of pregnancy (Amoroso and Finn 1962:454). The corpus luteum has a glandular function, secreting progesterone hormone which is essential for implantation and early development of the fertilized ovum. This hormone also suppresses further follicular development and ovulation. After parturition, corpora lutea of pregnancy regress and become corpora albicantia. Ability to identify corpora lutea of ovution of a previous heat from those of pregnancy of a later heat would eliminate a possible source of error when using corpora lutea counts as an index to reproductive rates of deer. Golley (1957) found the use of the corpora lutea dependable for determining the ovulation incidence of the black-tailed deer (Odocoileus hemionus columbianus) but detected an error when using the corpora albicantia to indicate ovulation. Golley used histological techniques to determine the differences between the two types of tissue. This paper will discuss gross size, shape, and color variations of corpora lutea in white-tailed deer ovaries as a possible means for distinguishing the two types. The assistance of Eldie Mustard, former Iowa State Conservation Commission Biologist, is appreciated. Several of Iowa's Conservation Commission officers and biologists also assisted materially by collecting reproductive tracts from wild deer. The cooperation of deer hunters who saved tracts for the study was indispensable. Calvin Rayburn, Ronald Schara, Harold Prince, and David Bolton, students 1Journal paper J-4604 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. A contribution from the Iowa Cooperative Wildlife Research Unit, which is jointly sponsored by Iowa State University of Science and Technology, U. S. Bureau of Sport Fisheries and Wildlife, the Iowa State Conservation Commission, and the Wildlife Management Institute. Financial support for Trauger was provided by the National Science Foundation Undergraduate Research Participation Program.

OVULATION RATES IN THE LACOMBE BREED OF PIGS

Ovulation rates were estimated by corpora lutea counts made after slaughter at 50 ± 4 or 100 ± 4 days of gestation. Mean corpora lutea counts of 14.5 ± 3.2 for gilts and 21.4 ± 4.4 for sows of the Lacombe breed are reported. The evidence suggested that ovulation rate was subject to a high degree of genetic control, but was not highly correlated with litter size at the stages of pregnancy examined.

Studies on prenatal mortality in the rabbit, Oryctolagus cuniculus: the amount and distribution of loss before and after implantation.

SUMMARY The amount and distribution of prenatal mortality were studied in 126 first and second pregnancies in seventy-three rabbits, weighing 3·5–4 kg. The does were mated naturally, artificially inseminated to ensure against the failure of natural mating, and injected with 25 i.u. luteinizing hormone. The numbers of corpora lutea and implantation sites were counted at laparotomy 7–13 days post coitum (p.c.) and the number of live foetuses was recorded at autopsy 28 days p.c., or after parturition. The diameter of the uterine swellings was measured at laparotomy. In a further eight pregnancies only the litter size was recorded. Ovulation occurred in every case, but in six (4·8%) of the 126 pregnancies all the ova (109, or 8·1%) were lost before implantation. In the remaining 120 pregnancies there was a total loss of 132 ova (or 154 if corrected for polyovuly), representing 9·7% of ovulations. In 64 out of the 120 pregnancies (53·3%) there was some loss of ova before implantation. The proportion of litters showing loss and the proportion of ova lost before implantation were significantly related to the number of ovulations. After implantation, total resorption occurred in four pregnancies (3·3%) and in a further eighty-five pregnancies (70·8%) there was some loss of embryos, which altogether amounted to 18·3% of the ovulations. The proportion of litters suffering loss after implantation was significantly related to the number of implantations. It was concluded that 7% of the embryos died shortly after implantation, 66% died between days 8 and 17, and 27% were lost between days 17 and 23. Data relating to the diameter of 1728 uterine swellings measured between days 7 and 20 p.c., counts of corpora lutea, the occurrence of corpora lutea atretica and polyovuly, the position of foetuses in utero, weights of placentae associated with resorbed embryos, foetal weights, birth weights, and the incidence of stillbirths are also presented.