scholarly journals Intensive Breeding of Rats 1. Crossfostering

1968 ◽  
Vol 2 (1) ◽  
pp. 35-39 ◽  
Author(s):  
W. Lane-Petter ◽  
Marjorie E. Lane-Petter ◽  
C. Wendy Bowtell
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Average Litter Size ◽  
Intensive Breeding ◽  
Weight For Age

The sex ratio of CFE rats as born is approximately 1:1, but the demand is usually for many more males than females. Litter size as born is variable, with resulting variation in weight for age at weaning and subsequently. The average litter size born is lower than that which the dams are capable of rearing. By a system of crossfostering pups at about two days of age, and killing surplus female pups at this age, litter size may be standardized, the sex ratio of animals raised can be adjusted to the demand, and larger litters can be reared.

Maximization of long-term productivity in a rat colony

1972 ◽  
Vol 6 (2) ◽  
pp. 203-206 ◽  
Author(s):  
N. T. Gridgeman ◽  
J. M. Taylor
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Albino Rats ◽  
Mathematical Treatment ◽  
Production Time ◽  
Time Curve ◽  
Intensive Breeding

Maximization of intensive breeding in the animal colony can be approached using a simple mathematical treatment of the production-time curve. It has been found that in a colony of specified-pathogen-free albino rats whose breeding dams were averaging litters of 11 at 6-week intervals, the stock should be entirely replaced at intervals of 27-28 weeks to maximize the output of weanlings. Some data on litter size and sex ratio are also presented.

scholarly journals Effect of inbreeding on fertility traits in five dog breeds

2019 ◽  
Vol 64 (No. 3) ◽  
pp. 118-129 ◽  
Author(s):  
Joanna Kania-Gierdziewicz ◽  
Sylwia Pałka
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Fixed Effects ◽  
Female Offspring ◽  
German Shepherd ◽  
Male And Female ◽  
Litter Traits ◽  
Average Litter Size ◽  
Inbreeding Level ◽  
Fertility Traits

The aim of the study was to analyze retrospectively the influence of inbreeding on fertility traits in five dog breeds: German Shepherd dog (GSD), Golden (GR) and Labrador (LR) Retrievers, Beagle and the Tatra Shepherd dog (TSD). The data were 436 litters, with the total of 2560 puppies: 1307 males and 1206 females. The parents of the litters were 163 dogs and 228 bitches. For each litter the litter size, number of male and female puppies, sex ratio, and sex difference were calculated. The fixed effects of breed, of litter birth year and linear regression coefficients on litter and parents’ inbreeding were included in the linear model for litter traits. The correlations between litter traits and litter parents’ inbreeding were also estimated. The average litter size was 5.87 (± 2.53) for all breeds. GSD had the smallest average litter size differences in years and the lowest fluctuations of sex ratio with litter size. In other dog breeds those differences were much bigger. The difference between the number of male and female offspring in a litter depended on the breed. The lowest percentage of inbred parents was found for LR, and the highest for TSD. Mating non-inbred animals, in most cases also unrelated, was frequent in all breeds. The inbreeding level of parents had significant influence on the litter traits only for TSD. For the Beagles low, positive and significant correlation between the number of female offspring in a litter and the dam’s inbreeding level and the sex ratio below 0.5 suggests sex ratio disturbance. The correlation coefficients between litter inbreeding and litter size for majority of examined dog breeds were positive but not significant. The conclusion is that in Poland at first obligatory monitoring of the inbreeding level for all breeds should be applied.

Ecology of the western barred bandicoot (Perameles bougainville) (Marsupialia: Peramelidae) on Dorre and Bernier Islands, Western Australia

1998 ◽  
Vol 25 (6) ◽  
pp. 567 ◽  
Author(s):  
Jeff Short ◽  
J. D. Richards ◽  
Bruce Turner
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Substantial Reduction ◽  
Female Dominance ◽  
Home Ranges ◽  
Island Populations ◽  
Median Distance ◽  
Average Litter Size ◽  
Significant Difference ◽  
System Body

Population structure, reproduction, condition, movements and habitat preference were assessed for western barred bandicoots (Perameles bougainville) on Dorre and Bernier Islands over seven trapping sessions between 1988 and 1995. Data comes from 372 captures of bandicoots in 2535 trap-nights (an average of 14·7 captures per 100 trap-nights). Trap success was 5.7–25.8% on Dorre and 5.7–7.6% on Bernier. Recaptures within a trip made up 29% of bandicoot captures. The overall sex ratio (excluding recaptures) was skewed heavily towards males at 1.7: 1 for trapped animals, but varied between male and female dominance at any time according to reproductive status of females. Sex ratio of pouch young was 1.2: 1. Production of young was concentrated in the wetter winter months. The smallest western barred bandicoot with pouch young weighed 175 g. Bandicoots showed a pattern of increasing litter size with size of mother. Females with young had an average litter size of 1.8, with young reaching independence at about 100 g body weight. Large testes size relative to body size in males suggested a promiscuous mating system. Body condition could be predicted by sex (females were typically in better condition than males) and by rainfall over the previous 2 months. Some sexual dimorphism was evident, with females having longer heads and typically being heavier than males. There was no detected dimorphism between island populations. Movements of bandicoots appeared limited, with the median distance moved by animals captured more than once within a 9–11-day trapping session being 154 m. There was no significant difference in movements between the sexes, with males moving a median distance of 160 m and females 138 m within trapping sessions. The greatest movement by a male was 1020 m while the greatest distance moved by a female was 490 m. Only 13% of recorded movements were greater than 400 m. Home ranges overlapped, with 51% of traps catching more than one individual and as many as five males being caught at the same trap site. Bandicoots were widely dispersed through all habitats surveyed. Bandicoots appeared to suffer a substantial reduction in numbers on Dorre Island in a prolonged drought extending from October 1986 to April 1989, reducing overall trap success to less than 6% in the 1988 survey.

scholarly journals The feeding and breeding of laboratory animals. VI. The breeding of mice

1947 ◽  
Vol 45 (4) ◽  
pp. 420-430 ◽  
Author(s):  
H. M. Bruce
Keyword(s):  
Sex Ratio ◽  
Litter Size ◽  
Reproductive Performance ◽  
Post Partum ◽  
Statistical Analyses ◽  
Gestation Period ◽  
Laboratory Animals ◽  
One Year ◽  
Intensive Breeding

1. The total reproductive performance of two groups each of twenty-four mice over a period of one year under two different systems of mating has been recorded.2. In the first system (monogamous pairs) the male was kept continuously with the female; in 78% of cases the females became pregnant again at post-partum oestrus and were thus subjected for the most part to unbroken intensive breeding.3. In the second system (polygynous groups) several females were kept with one male and were removed to individual cages for the birth and rearing of the litters and were returned to the male again only after the litter had been weaned.4. Under the first system 1149 young were successfully reared to weaning in one year by the twenty-four females; under the second system 559 young were weaned during the same period.5. Mortality of breeding females, litter size, weight of young at weaning, the effect of parity, loss of litters and of young between birth and weaning and the sex-ratio of the young weaned were alike for both methods of mating.6. The interaction of concurrent gestation and lactation upon the length of the gestation period is discussed, and regression lines showing the relation between the number of young suckled, the number of young in the uterus and the length of the gestation period are given.My best thanks are due to Dr A. S. Parkes, F.R.S., for advice during the course of the work and for help in the preparation of the manuscript. I should also like to thank Dr C. W. Emmens for the statistical analyses and the calculation of the regression lines.

scholarly journals Studies on the Sex-Ratio and Related Phenomena

1926 ◽  
Vol 4 (1) ◽  
pp. 93-104
Author(s):  
A. S. PARKES
Keyword(s):  
Seasonal Variation ◽  
Sex Ratio ◽  
Recent Work ◽  
Litter Size ◽  
Annual Variation ◽  
Average Litter Size ◽  
Average Size

(1) 1872 normal mice bred during November 1922-October 1925 had an average litter-size of 6.18, and a male percentage of 51.7 ± .77, both of which figures are lower than the corresponding ones found for 1921-2. (2) The annual variation in the sex-ratio is, however, not very appreciable, the figures for the four years running 54.2 ± 1.04, 50.4 ± 3.22, 52.2 ± 1.18, 51.4 ± 1.09. The average size of litter during these four periods ranged from 6.65 to 5.93. (3) Considerable seasonal variation in both fertility and sex-ratio occurred, the highest figures being fertility 6.46 and male percentage 55.9 ± 1.83 in the October-December quarter, and the lowest being fertility 5.82 and male percentage 48.2 ± 1.46 in the April-June period. (4) Litter-size appeared to be uncorrelated with any sort of definite variation in the sex-ratio. (5) Recent work on the mouse is discussed.

Ambient Temperature and Rainfall: An Effect on Sex Ratio and Litter Size in Deer Mice

1985 ◽  
Vol 66 (2) ◽  
pp. 289-298 ◽  
Author(s):  
P. Myers ◽  
L. L. Master ◽  
R. A. Garrett
Keyword(s):  
Sex Ratio ◽  
Ambient Temperature ◽  
Litter Size ◽  
Deer Mice

REPRODUCTIVE POTENTIAL AND SEX RATIOS OF SNOWSHOE HARES IN NORTHERN ALBERTA

1956 ◽  
Vol 34 (4) ◽  
pp. 273-281 ◽  
Author(s):  
Wm. Rowan ◽  
L. B. Keith
Keyword(s):  
Litter Size ◽  
Sex Ratios ◽  
Reproductive Potential ◽  
Post Mortem ◽  
Comparable Data ◽  
Snowshoe Hares ◽  
Average Litter Size ◽  
Northern Regions ◽  
Two Factors ◽  
Northern Alberta

In conjunction with studies of the "10-year cycle" of snowshoe hares, almost 900 hares were collected in the Anzac district of Alberta during the period May, 1949, to April, 1956. Embryo numbers and sex ratios were among the data gathered from post-mortem examinations of these hares. It was found that the average litter size was 3.82; the modal litter size was four and the range was from one to seven. The average number of litters each season was calculated at 2.75. The annual reproductive potential is thus 10.51 (3.82 × 2.75) young per female hare. This is more than 50% greater than that indicated by comparable data from Minnesota. It is suggested that herein lies the cause of higher peak populations in northern regions. Sex ratios shifted from a marked excess of females in the year 1949–1950 to about even numbers of both sexes during the two subsequent years. Since the change in sex ratio occurred at the peak of the cycle, the two factors are believed to be in some manner correlated.

Development of a Strain of Rabbits with Congenital Simple Nonsyndromic Coronal Suture Synostosis Part I: Breeding Demographics, Inheritance Pattern, and Craniofacial Anomalies

1994 ◽  
Vol 31 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Mark P. Mooney ◽  
H. Losken Wolfgang ◽  
Michael I. Siegel ◽  
Janice F. Lalikos ◽  
Albert Losken ◽  
...  
Keyword(s):  
Litter Size ◽  
Rabbit Model ◽  
Pedigree Analysis ◽  
Human Populations ◽  
Incomplete Penetrance ◽  
Coronal Suture ◽  
Inheritance Pattern ◽  
Average Litter Size ◽  
Midfacial Hypoplasia ◽  
Congenital Condition

The lack of an animal model of congenital coronal suture (CS) synostosis has prompted the widespread use of an experimental rabbit model using adhesive Immobilization of the CS. Such postnatal models have helped make significant scientific contributions but may still not fully represent all aspects of the human congenital condition. In the March 1993 issue of The Cleft Palate-Craniofacial Journal we reported a female rabbit born in our laboratory with complete bilateral CS synostosis. This follow-up study presents our attempts to breed this animal and establish a strain of cranlosynostotic rabbits. To date, we have accomplished 10 back- and intercrosses with these animals and have produced a total of 71 live offspring; 10 animals exhibited complete nonsyndromic unilateral (plagiocephalic) or bilateral (brachycephalic) CS synostotic deformities at birth, and 19 animals exhibited partial CS synostosis that showed more than 75% growth retardation across the CS (well below the 95% confidence interval for normals). Results revealed that gestational time and litter size averages were consistent with those reported for the strain, although the average litter size decreased with increased inbreeding. By 1.5 weeks of age the completely synostosed animals already exhibited brachycephalic cranial vaults and midfacial hypoplasia compared to unaffected siblings. Initial pedigree analysis suggested an autosomal dominant inheritance pattern with incomplete penetrance and variable expressivity. The development of such a congenital rabbit model may prove useful In helping to understand the etiopathogenesis of this condition In human populations.

A note on ovulation rate and embryonic survival in D'man ewes

1981 ◽  
Vol 32 (2) ◽  
pp. 227-229 ◽  
Author(s):  
A. Lahlou-Kassi ◽  
M. Marie
Keyword(s):  
Litter Size ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Embryonic Survival ◽  
Average Litter Size ◽  
Simultaneous Activity

ABSTRACTThe elements of prolificacy have been analysed for the D'man sheep, a prolific Moroccan breed, by laparotomy on 38 animals. The average ovulation rate was 2·50 (s.e.0·45); a slight difference was observed between nulliparous and multiparous ewes due to high simultaneous activity by both ovaries in the latter group. Embryonic survival (42% overall) was 94% (87 to 100%) for multiparous and 44% (36 to 52%) for the nulliparous ewes at one ovulation, decreasing with increasing numbers of corpora lutea. The average litter size showed an optimum at four ovulations.

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