Genetics of reproduction in the rabbit.

2021 ◽  
pp. 212-233
Author(s):  
Miriam Piles ◽  
Maria Antonia Santacreu ◽  
Agustin Blasco ◽  
Jun Pablo Sanchez
Keyword(s):  
Litter Size ◽  
Reproductive Cycle ◽  
Genetic Determinism ◽  
Ovulation Rate ◽  
Biological Processes ◽  
Embryo Survival ◽  
Male And Female ◽  
Fetal Survival

Abstract This chapter describes the genetic determinism of all traits involved in male and female reproductive performances in rabbits. All traits related to the underlying biological processes leading to the mating outcome, as well as some of its general features, such as the homogeneity of the reproductive performances, are considered (semen and ejaculate characteristics, ovulation rate, fertility, embryo survival, fetal survival and litter size). Different parameters of fertility and litter size are discussed, including the contribution of both sexes to each phase of the reproductive cycle.

scholarly journals Components of litter size in mice after 110 generations of selection

Reproduction ◽  
2004 ◽  
Vol 127 (5) ◽  
pp. 587-592 ◽  
Author(s):  
M Holt ◽  
O Vangen ◽  
W Farstad
Keyword(s):  
Litter Size ◽  
Late Pregnancy ◽  
Ovulation Rate ◽  
Control Line ◽  
Embryo Survival ◽  
High Line ◽  
Line Selection ◽  
Males And Females ◽  
The Mean ◽  
Standard Deviations

The aim of the present study was to evaluate how ovulation rate and survival rate through pregnancy had been affected by more than 110 generations of upwards selection on litter size in mice. The mean number of pups born alive was 22 in the high line (selected line) and 11 in the control line (an increase in 2.6 standard deviations). Selection on litter size increased ovulation rate by 4.6 standard deviations, and it is suggested that selection also increased embryonic mortality in late pregnancy. Embryo survival from ovulation until birth was 66% in the selected line and 69% in the control line, and the observed loss in litter size from day 16 of pregnancy until birth was possibly higher in the high line compared with the control line. Selection for higher litter size has significantly increased body weight in both males and females, as the mean weight at mating for the females was 46 g in the high line and 33 g in the control line respectively.

The effect of energy or protein supplementation on embryo survival rate in ewes

1995 ◽  
Vol 1995 ◽  
pp. 55-55
Author(s):  
M.G. Diskin ◽  
J.P. Hanrahan
Keyword(s):  
Survival Rate ◽  
Litter Size ◽  
Protein Supplementation ◽  
Ovulation Rate ◽  
Reproductive Efficiency ◽  
Protein Supplement ◽  
Embryo Survival ◽  
Rumen Undegradable Protein

Embryo survival rate is a major factor determining litter size and overall reproductive efficiency in sheep. In sheep, as ovulation rate increases the proportion of embryos surviving decreases. There is evidence, from cattle, that feeding a rumen-undegradable protein supplement enhances embryo survival rate. The objective of this experiment was to determine the effect on embryo survival rate in high prolific ewes of feeding an energy or protein supplement.

Effect of selection for increased litter size on ovulation rate and embryo survival in sheep

1990 ◽  
Vol 1990 ◽  
pp. 32-32 ◽  
Author(s):  
J.P. Hanrahan
Keyword(s):  
Litter Size ◽  
Ovulation Rate ◽  
Control Line ◽  
Selection Experiment ◽  
Embryo Survival ◽  
Relative Contribution ◽  
Variation Data ◽  
Component Traits ◽  
Selection For ◽  
The Impact

Variation in litter size in sheep is essentially attributable to variation in ovulation rate and embryo survival. Genetic variation in litter size, both among and within breeds, is largely attributable to variation in ovulation rate. While there is evidence for genetic differences among breeds in embryo survival the contribution of this component to within breed variation appears to be minor (Hanrahan, 1982). The impact of selection based on litter size on its component traits should reflect the relative contribution of these components to within breed variation. Data from two lines of Galway sheep, a Control line and one selected for increased prolificacy (Hanrahan and Timon, 1978), have been used to provide evidence on this point.Details relating to the selection experiment which provided the data for the present study are in Hanrahan (1984). Briefly a flock of Galway sheep was assembled from industry sources (both pedigree and non-pedigree) between 1963 and 1965.

Genetic studies of prolificacy in New Zealand sheep

1998 ◽  
Vol 67 (2) ◽  
pp. 289-297 ◽  
Author(s):  
G. H. Davis ◽  
C. A. Morris ◽  
K. G. Dodds
Keyword(s):  
Litter Size ◽  
Heritability Estimate ◽  
Ovulation Rate ◽  
The Other ◽  
Relationship Matrix ◽  
Research Station ◽  
Embryo Survival ◽  
Genetic Studies ◽  
Average Litter Size ◽  
Likelihood Model

AbstractData on ovulation rate, embryo survival and litter size have been analysed from the 1988-96 records collected at AgResearch's Woodlands Research Station on 2180 elite (highly prolific) ewes of three breeds: Romney, Coopworth and Perendale. The Romneys included a subgroup found to carry the sex-linked Inverdale high prolificacy gene. Foundation animals for all breeds were screened on high litter size (lambs born, alive or dead, per ewe lambing) from industry flocks. Prior to being transferred to Woodlands between 1979 and 1984, their average litter size was 2·66. Ovulation rates for descendants of the foundation ewes averaged 2·15 (Romney), 2·43 (Coopworth), 2·15 (Perendale) and 2·96 for the Romney subgroup carrying the Inverdale gene. Embryo survival averaged 0·84 except for a low value in Inverdales (0·76). Using a restricted maximum likelihood model, with full relationship matrix, the within-breed heritability of ovulation rate over all ages and breeds (excluding Inverdale) was 0·14 (s.e. 0·03), with repeatability 0·26 (s.e. 0·02). Litter size averaged 1-80 (Romney), 2·05 (Coopworth), 1·76 (Perendale) and 2·17 (Inverdale). The heritability estimate for litter size (excluding Inverdale) was 0·073 (s.e. 0·018), from data for all ages. The genetic correlation between ovulation rate and litter size was 0·91 (s.e. 0·08). The standard deviation for ovulation rate in the Inverdales was 1·75 times as great as the average of the other three breeds. Embryo survival to term for ewes conceiving to two, three or four ovulations averaged 0·89, 0·77 and 0·64, respectively, and was significantly different among breeds fP < 0·001). The greater ovulation rate in Inverdales than Romneys was sufficient to explain the Inverdale effect on reduced embryo survival. The highest embryo survival was observed in the Coopworth breed (P < 0·001).

scholarly journals 374 Early embryonic loss is an important mechanism for maximizing litter size in the pig

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 123-123
Author(s):  
Rodney D Geisert ◽  
Ashley E Meyer ◽  
Caroline A Pfeiffer ◽  
Destiny N Johns ◽  
Randall S Prather ◽  
...  
Keyword(s):  
Litter Size ◽  
Fetal Growth ◽  
Direct Method ◽  
Early Embryo ◽  
Ovulation Rate ◽  
Loss Of Function ◽  
Fetal Survival ◽  
Large Litter ◽  
Embryonic Loss ◽  
Embryo Loss

Abstract Litter size of commercial dam lines of pigs has seen a significant increase over the last 20 years. Although the current large litter size of gilts and sows can be attributed to improved genetic selection and nutrition, much of the increase in total number born has occurred through the continued increase in ovulation rate over the last four decades. Ovulation rate has increased from 14 in the 80’s to today’s average of 20–25 in commercial dam lines. However, high ovulation rate not only causes increased competition between embryos (uterine crowding), but the number of potential piglets born can out strip the number available teats. In addition, fetal crowding can reduce fetal growth and comprise health and survivability of lighter weight piglets at birth. Since there is usually minimal embryo loss observed up to blastocyst formation and hatching, the majority (20 to 30%) of embryonic loss occurs during Days 10 to 30 of gestation, which encompasses a critical period of conceptus development and differentiation, pregnancy recognition signaling, and onset of implantation. This period of early embryo loss is actually essential for establishing adequate uterine space to support fetal survival for a large litter. The period of rapid conceptus elongation on Day 12 of pregnancy provides a key “selection point” for regulating potential litter size in the pig. Establishing the fundamental roles of conceptus- and uterine-secreted factors is an essential step to develop strategies to increase placental and fetal growth to improve overall health and survivability of piglets before and after birth. During the peri-implantation period of pregnancy, porcine conceptuses produce interleukin-1B2, estrogens, prostaglandins and interferons. CRISPR/Cas9 genomic engineering technology has provided a direct method to evaluate the role of key pig conceptus genes. Loss-of-function studies have increased our understanding of the multiplicity of uterine/conceptus factors that are involved with maintenance of pregnancy.

scholarly journals Effects of flush feeding strategy before breeding on reproductive performance of modern replacement gilts: impacts on ovulation rate and litter traits

2020 ◽  
Vol 98 (6) ◽  
Author(s):  
André L Mallmann ◽  
Lidia S Arend ◽  
Gabriela S Oliveira ◽  
Ana P G Mellagi ◽  
Rafael R Ulguim ◽  
...  
Keyword(s):  
Litter Size ◽  
Reproductive Performance ◽  
Feeding Strategy ◽  
Early Embryo ◽  
Ovulation Rate ◽  
Breeding Cycle ◽  
Corpora Lutea ◽  
Embryo Survival ◽  
Estrous Cycles ◽  
Litter Traits

Abstract AbstractThe effects of two feed levels offered during two estrous cycles before insemination were evaluated on the reproductive performance of gilts. A total of 93 gilts (PIC Hendersonville, TN) were individually housed and manually fed twice a day with 2.1 or 3.6 kg/d of a corn and soybean meal-based diet (3.15 Mcal ME/kg and 0.64% standardized ileal digestible lysine), during two estrous cycles before breeding (cycle 1, between first and second estrus; cycle 2, between second and third estrus). Gilts were weighed at the beginning of the experiment, at second and third estrus, and at slaughter (30.2 ± 1.2 d of gestation). Follicles were counted at second estrus, and the embryo-placental units and the corpora lutea were individually counted, measured, and weighed at slaughter. Gilts fed 3.6 kg/d had greater BW gain during cycle 1 and cycle 2 (P &lt; 0.001; + 9.8 kg and + 10.0 kg, respectively) becoming heavier at second and third estrus (P &lt; 0.001). At second estrus, gilts fed 3.6 kg/d had 1.6 more medium-large follicles (P = 0.074) but no difference in follicle size (P = 0.530) was observed. Gilts fed 3.6 kg/d in cycle 1 or cycle 2 had a greater ovulation rate at third estrus (P &lt; 0.016) than those receiving 2.1 kg/d. Also, 3.6 kg/d in cycle 2 increased early embryo mortality (P = 0.006; 2.3 vs. 1.1 dead embryos) and consequently reduced total embryo survival (P = 0.002; 84.6 vs. 90.1%). Gilts fed 3.6 kg/d during cycle 1 had two more total embryos (P &lt; 0.001; 17.2 vs. 15.1) and two more vital embryos on day 30 (P &lt; 0.001; 16.7 vs. 14.5) in comparison with gilts fed 2.1 kg/d. The coefficient of variation for placental length was greater for gilts fed 3.6 kg/d during cycle 1 (P = 0.003). No further significant effects of feeding levels were observed on embryo and placental traits (P ≥ 0.063). These results suggest that the feeding level during the first cycle after pubertal estrus is crucial to set ovulation rate and potential litter size for breeding at next estrus. However, flush feeding gilts before insemination can negatively impact litter size by reducing embryo survival when breeding at third estrus.

Genetic implications of a simulation model of litter size in swine based on ovulation rate, potential embryonic viability and uterine capacity: II. Simulated selection.

1990 ◽  
Vol 68 (4) ◽  
pp. 980-986 ◽  
Author(s):  
G. L. Bennett ◽  
K. A. Leymaster
Keyword(s):  
Simulation Model ◽  
Litter Size ◽  
Selection Pressure ◽  
Selection Response ◽  
Ovulation Rate ◽  
Direct Selection ◽  
Weak Selection ◽  
Embryo Survival ◽  
Swine Population ◽  
Selection For

Abstract Direct selection for ovulation rate, uterine capacity, litter size and embryo survival and selection for indexes of ovulation rate with each of the remaining traits were simulated for a swine population. The relationships among these traits were determined from a simulation model that assumed that litter size was always less than or equal to both ovulation rate and uterine capacity. Heritabilities of ovulation rate and uterine capacity were assumed to be .25 and .20, respectively, and uncorrelated genetically and phenotypically. No additional genetic variation was assumed. Responses to weak selection pressure were simulated by recurrent updating of phenotypic variances and covariances combined with the heritabilities of ovulation rate and uterine capacity. Two indexes of ovulation rate and uterine capacity each resulted in 37% greater increase in litter size than direct selection for litter size. Indexes of ovulation rate and either litter size or embryo survival increased litter size by 21% more than direct selection for litter size. Selection for ovulation rate, uterine capacity or embryo survival was 6, 35 and 79%, respectively, less effective than direct selection for litter size. Responses to intense selection pressure were determined by direct simulation of genotypes and phenotypes of individuals. The two indexes of ovulation rate and uterine capacity exceeded direct selection for litter size by 39 and 27%. The indexes of ovulation rate and either litter size or embryo survival exceeded direct selection for litter size by 19 and 13%, respectively. Intense selection for ovulation rate or uterine capacity decreased selection response by 26 and 67%, respectively, relative to direct selection for litter size. Intense selection for embryo survival decreased litter size slightly.

The effect of feeding a diet high in fibre during the rearing period on reproduction in gilts

1999 ◽  
Vol 1999 ◽  
pp. 67-67 ◽  
Author(s):  
V.L. Glasgow ◽  
S.A. Edwards ◽  
T.G. McEvoy ◽  
M. Shanks
Keyword(s):  
Sugar Beet ◽  
Litter Size ◽  
Block Design ◽  
Early Embryo ◽  
Ovulation Rate ◽  
Embryo Viability ◽  
Embryo Survival ◽  
Flat Rate ◽  
Pregnancy And Lactation ◽  
Effect Of Feeding

Feeding diets high in fibre to breeding sows has been found to have a positive effect on reproductive performance. Danske Slagterier (1994) found a significant increase in litter size when sows were fed a diet containing high levels of unmolassed sugar beet pulp (USBP) during pregnancy and lactation. Litter size is influenced by two main factors; ovulation rate and embryo survival. Glasgow et al (1996) found no increase in ovulation rate in gilts fed high USBP diets. This experiment was designed to assess the effect of feeding a high USBP diet on endocrinology and early embryo viability.The experiment was of a randomised block design incorporating two diets; a cereal based diet (C) and a diet containing 50% unmolassed sugar beet (HF). 72 gilts of lean genotype (Newsham Hybrids) were allocated to treament at 138 days of age, housed in groups of 6 and had liveweight and backfat thickness recorded fortnightly. For the first 8 weeks, HF gilts were fed ad-libitum and C gilts were pair fed to the same daily energy intake. Subsequently, gilts were floor fed isoenergetically at a flat rate of 2.8 kg/d (HF) and 2.3 kg/d (C).

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