Polymorphism identification in the goat KITLG gene and association analysis with litter size

This study reported the analysis of KIT ligand (KITLG) gene polymorphisms in 681 goats of three breeds: Xinong Saanen (SN), Guanzhong (GZ), and Boer (BG). In addition, the study identified three allelic variants: g.769T>C and g.817G>T in SN and GZ breeds, and g.9760G>C in the three goat breeds. The g.769T>C and g.817G>T loci were closely linked (r² > 0.33). All the single nucleotide polymorphism loci were in Hardy–Weinberg disequilibrium (P < 0.05). Significant associations were found for litter size with all three loci. Therefore, these results suggest that the KITLG gene is a strong candidate gene affecting litter size in goats.     

Artificial insemination in the mouse with special reference to the effect of sperm numbers on the conception rate and litter size (author's transl)

Mature female mice (ICR-JCL), 8 to 12 weeks of age, were artificially inseminated at 8:30-9:30 a. m. on the day of estrus vaginal smear (about 3-7 hr after ovulation) with 3.18 X 10(6), 1.83 X 10(6) and 1.15 X 10(6) sperms from four, two and one cauda epididymidis, respectively, of adult males which were suspended in 50 microliter of a modified Krebs-Ringer-bicarbonate solution and incubated at 37 degrees C was under 5% CO2 in air for an hour. Immediately after insemination, pseudopregnancy induced by an artificial penis and a vaginal tampon. Out of 13 females inseminated with 3.18 X 10(6) sperms, 9 females showed placental signs and 8 of them gave birth to the mean 10.5+/-2.20 (M+/-S.D.) young at term. Four of 13 females having received 1.83 X 10(6) sperms became pregnant giving birth to the mean 4.3+/-2.1 (M+/-S.D.) young at term. On the other hand, 5 out of 6 females failed to become pregnant following insemination with 1.15 X 10(6) sperms, and only one showed a placental sign and gave birth to twelve young at term. It is concluded that the conception rate and litter size are both dependent on the number of sperms inseminated and that more than 3 X 10(6) sperms are necessary to get the conception rate and the litter size comparable to those in natural mating.     

Breed and experience effect on the sexual behaviors of Damascus and Egyptian-Nubian goat bucks

This study compares the sexual behaviors of bucks from two pure breeds of goats, Damascus and Egyptian-Nubian (Zaraibi), and assesses their relationships with the pregnancy and kidding rates of their inseminated does. Twenty-three bucks (12 Damascus and 11 Egyptian-Nubian bucks) were used in this study. These bucks were either in their first season of service (N =12, with an average age of 1.51 years) or had been previously used in service for several seasons (N = 11, with an average age of 3.34 years). Buck service behaviors toward estrous does were continuously recorded for 30 minutes from the moment of appearance of the doe. Egyptian-Nubian bucks were highly sexually active with estrous does in comparison with Damascus bucks. They required less time to mount and ejaculate for the first (P < 0.04) and second times (P < 0.0002) and tended to sniff, nudge and vocalize more frequently than Damascus bucks. In addition, Egyptian-Nubian bucks had more ejaculations and a higher mating efficiency (27.48% vs. 10.21%, P < 0.001), and their inseminated does had a higher pregnancy rate and larger litter sizes. Regarding the effect of experience, the data revealed a limited influence. No significant differences in sexual behavior were recorded between younger and older bucks. Conversely, pregnancy, kidding rates, and litter size were not influenced by the total number of ejaculations. From these results, it can be concluded that there were sexual behavior differences as a function of breed between Damascus and Egyptian-Nubian bucks and that experience had little impact in this study.     

The influence of ovulation rate on subsequent litter size in sows

Data were collected from 318 pregnant sows (Large White, Landrace or crossbred), which had been weaned from their first litter, to determine the relationship between ovulation rate (OR) and subsequent litter size (total born alive - TBA). Laparoscopy was performed on sows 7 to 14 days after mating to determine OR, and subsequent litter size (TBA) was recorded. Mean (+/-SE) ovulation rate, litter size (TBA) and foetal survival (FS) was 14.56+/-0.19, 9.00 +/- 0.16 and 63.5+/-1.1%, respectively. Regressions of TBA against OR and FS against OR were best fitted by a linear function which indicated that litter size of first-litter sows was limited by ovulation rate up to at least 23 ova. The respective linear regressions were:     

Correlated responses on litter size traits and survival traits after two-stage selection for ovulation rate and litter size in rabbits

Farmer profit depends on the number of slaughter rabbits. The improvement of litter size (LS) at birth by two-stage selection for ovulation rate (OR) and LS could modify survival rate from birth to slaughter. This study was aiming to estimate direct and correlated response on LS traits and peri- and postnatal survival traits in the OR_LS rabbit line selected first only for OR (first period) and then for OR and LS using independent culling levels (second period). The studied traits were OR, LS measured as number of total born, number of kits born alive (NBA) and dead (NBD), and number of kits at weaning (NW) and young rabbits at slaughter (NS). Prenatal survival (LS/OR) and survival at birth (NBA/LS), at weaning (NW/NBA) and at slaughter (NS/NW) were also studied. Data were analysed using Bayesian inference methods. Heritability for LS traits were low, 0.07 for NBA, NW and NS. Survival traits had low values of heritability 0.07, 0.03 and 0.03 for NBA/LS, NW/NBA and NS/NW, respectively. After six generations of selection by OR (first period), a small increase in NBD and a slight decrease in NBA/LS were found. However, no correlated responses on NW/NBA and NS/NW were observed. After 11 generations of two-stage selection for OR and LS (second period), correlated responses on NBA, NW and NS were 0.12, 0.12 and 0.11 kits per generation, respectively, whereas no substantial modifications on NBA/LS, NW/NBA and NS/NW were found. In conclusion, two-stage selection improves the number of young rabbits at slaughter without modifying survival from birth to slaughter.     

The imprinted gene DIO3 is a candidate gene for litter size in pigs

Genomic imprinting is an important epigenetic phenomenon, which on the phenotypic level can be detected by the difference between the two heterozygote classes of a gene. Imprinted genes are important in both the development of the placenta and the embryo, and we hypothesized that imprinted genes might be involved in female fertility traits. We therefore performed an association study for imprinted genes related to female fertility traits in two commercial pig populations. For this purpose, 309 SNPs in fifteen evolutionary conserved imprinted regions were genotyped on 689 and 1050 pigs from the two pig populations. A single SNP association study was used to detect additive, dominant and imprinting effects related to four reproduction traits; total number of piglets born, the number of piglets born alive, the total weight of the piglets born and the total weight of the piglets born alive. Several SNPs showed significant (q-value < 0.10) additive and dominant effects and one SNP showed a significant imprinting effect. The SNP with a significant imprinting effect is closely linked to DIO3, a gene involved in thyroid metabolism. The imprinting effect of this SNP explained approximately 1.6% of the phenotypic variance, which corresponded to approximately 15.5% of the additive genetic variance. In the other population, the imprinting effect of this QTL was not significant (q-value > 0.10), but had a similar effect as in the first population. The results of this study indicate a possible association between the imprinted gene DIO3 and female fertility traits in pigs.     

Efficiency of energy use for pregnancy by meat goat does with different litter size

Twenty-four Boer × Spanish does (3 years of age, having kidded once previously and with an initial BW of 42.7 ± 1.2 kg) were used to determine the efficiency of ME utilization for pregnancy (k_preg). Six does were nonpregnant and, based on ultrasound determination on day 45 of gestation, six had a litter size (LS) of 1, 2, and 3. However, only 10 of the pregnant does delivered the expected number of kids (3, 4, and 3 with LS of 1, 2, and 3, respectively). Does were fed a diet of approximately 50% concentrate in accordance with assumed maintenance plus pregnancy energy requirements based on estimated nonpregnancy tissue BW and LS. Recovered energy (RE) was determined by subtraction of energy expenditure (EE; respiration calorimetry) near days 80, 100, 120, and 140 of gestation from ME intake (MEI). RE was assumed attributable to pregnancy tissues (fetus, fetal fluids and membranes, uterus, and mammary gland), and ME used for pregnancy (ME_preg) was estimated by subtracting ME_m determined with nonpregnant goats from MEI by those pregnant. For does with actual LS equal to that expected, the no-intercept equation for the regression of RE against ME_preg was: RE = ME_preg × 0.252 (S.E. = 0.030; R² = 0.64), indicating a k_preg of 25%. A regression including LS (1 versus 2 or 3) suggested greater k_preg for LS of 1 (40.2 ± 5.6%) versus 2 or 3 (20.5 ± 3.2%). Regressions for goats with LS different from expected suggested positive effects of use of energy mobilized from nonpregnancy tissues on k_preg and of use of dietary ME for energy accretion in nonpregnancy tissues on the efficiency of whole body ME utilization. In conclusion, the average efficiency of ME use for pregnancy regardless of LS in goats was near 25%, which when considering the expected proportion of all pregnancy tissues attributable to fetal or conceptus tissues implies an energy requirement for pregnancy of goats similar to common recommendations for sheep and cattle.     

The effect of fast created inbreeding on litter size and body weights in mice

This study was designed to reveal any differences in effects of fast created versus total inbreeding on reproduction and body weights in mice. A line selected for large litter size for 124 generations (H) and a control line (K) maintained without selection for the same number of generations were crossed (HK) and used as a basis for the experiment. Within the HK cross, full sib, cousin or random mating were practised for two generations in order to create new inbreeding (IB_F) at a fast rate. In the first generation of systematic mating, old inbreeding was regenerated in addition to creation of new inbreeding from the mating design giving total inbreeding (IB_T). The number of pups born alive (NBA) and body weights of the animals were then analysed by a model including both IB_T and IB_F. The IB_T of the dam was in the present study found to reduce the mean NBA with -0.48 (± 0.22) (p < 0.05) pups per 10% increase in the inbreeding coefficient, while the additional effect of IB_F was -0.42 (± 0.27). For the trait NBA per female mated, the effect of IB_T was estimated to be -0.45 (± 0.29) per 10% increase in the inbreeding coefficient and the effect of IB_F was -0.90 (± 0.37) (p < 0.05) pups. In the present study, only small or non-significant effects of IB_F of the dam could be found on sex-ratio and body weights at three and six weeks of age in a population already adjusted for IB_T.     

Influence of SLA haplotype on ovulation rate and litter size in miniature pigs

Systemic blood was collected from and surgery performed on sows of 3 strains of miniature swine bred for specific SLA (swine MHC) haplotypes (a, c and d) from Day 2 to Day 6 after mating (first day of mating = Day 0). Ovulation rate was determined by counting corpora lutea and embryos were flushed from the uterus. Progesterone, oestradiol-17 beta and oestrone were quantitated in blood plasma and uterine flushings by RIA. SLAd/d females had a higher ovulation rate than SLAa/a or SLAc/c females (11.50 +/- 0.87 vs 9.11 +/- 0.68 and 8.17 +/- 0.83, respectively; P less than 0.01). Oestrone was higher than oestradiol-17 beta in systemic plasma (56.5 +/- 6.4 vs 33.0 +/- 4.7 pg/ml, P less than 0.01) while oestradiol-17 beta was higher than oestrone in uterine flushings (19.8 +/- 1.4 vs 14.9 +/- 1.5 pg/horn, P less than 0.10). Systemic progesterone concentration was correlated with day after mating (r = 0.93, P less than 0.01). There was no effect of haplotype on any of the hormone concentrations measured. Litter size was analysed from 99 matings amongst SLAa/a, SLAa/c, SLAa/d, SLAd/c and SLAd/d sires and dams. Litter size from -/d and d/d sows or from d/d boars were larger (P less than 0.05) than for all other matings. Although ovulation rate was higher in SLAd/d sows, the significant effect of sire SLA genotype on litter size suggests an additional effect of the d haplotype on embryonic survival.     

The effect of exogenous estradiol on litter size in a typical swine herd

Fifty-six female pigs (12 gilts, 26 primiparous and 18 multiparous sows) were bred and assigned to receive either corn oil (vehicle; n=28) or estradiol-17beta (2 mg/day; i.m.; n=28) on Days 12 and 13 (Day 0 = first day of estrus) to determine if exogenous estradiol could improve litter size in swine. Though litter size of the females farrowing was not increased with estradiol treatment (vehicle versus estradiol, 9.7 +/- 0.8 versus 10.1 +/- 1.8 live pigs born, respectively), more females in this group remained pregnant (vehicle versus estradiol, 6 versus 1 recycled, respectively; P<0.05). Litter size, expressed as the number of pigs born per-female-bred, was therefore increased with exogenous estradiol (vehicle versus estradiol, 7.6 +/- 0.8 versus 9.8 +/- 0.7 live pigs born, respectively; P<0.05). Some of these estradiol- treated females produced smaller (P<0.05) litters and this may be of concern in herds experiencing low fertilization/conception rates. Overall 60 more pigs were born alive to females in the estradiol-treated group than to the control group females. This experiment demonstrated that supplemental estradiol treatment on Days 12 and 13 assisted in maintenance of pregnancy and thereby increased litter size on a per-female-bred basis.     

Influence of early pregnancy on reproductive rate in lines of mice selected for litter size

Summary The influence of male-induced early puberty on female reproductive rate was determined in three lines of mice differing in litter size and body weight. The lines originated from a single base population and had undergone 20 generations of selection for the following criteria: large litter size at birth (L⁺), large litter size and small 6-week body weight (L⁺W^–), or small litter size and large 6-week body weight (L^–W⁺). Females were paired with a mature intact male of the same line at 3, 5 or 7 weeks of age. Mean mating age, averaged over lines, was 26.5 ± .3, 38.3 ± .3 and 52.7 ± .3 days. Exposure to a mature male accelerated female sexual maturation in each line. When contrasted with their sibs mated at a later age, early-pregnant females from each line exhibited a decline in one or more component of reproductive performance, suggesting that the physiological state of the very young female was not optimum for normal pregnancy. In comparisons of early and later mating ages, all three lines showed a decreased littering rate at first mating, number born alive, and individual birth weight of progeny adjusted for litter size; L⁺ and L⁺W^– mice showed an increased perinatal mortality rate; L⁺ and L^–W⁺ had a reduction in litter size at birth. When the L⁺, L⁺W^– and L^–W⁺ lines were compared with an unselected strain and a line selected for high postweaning gain in similar experiments, a genotype by environment interaction was apparent since all lines did not respond in a similar manner to early mating. The line ranking for litter size at birth for each age at male-exposure was L⁺>L⁺W^–>L^–W⁺, despite the significant line by age interaction. When litter size was adjusted by covariance for body weight at mating, the significant effects of age at male-exposure and line by age interaction were eliminated. All fertile females were remated after they had weaned their first litter to obtain information on litter size in parity two. Line differences in litter size at birth and number born alive were uniform across parities. An age by parity interaction was evident since the decreased fecundity at younger ages of male exposure in the L⁺ and L^–W⁺ litters of parity one was not evident in parity two. Litter feed efficiency during first parity gestation was defined as litter birth weight divided by either cumulative feed intake of the dam from mating to parturition (GEI) or cumulative feed intake from weaning to parturition (GEII). The ranking of lines for GEI and GEH was L⁺> L⁺W^–>L^–W⁺, but when feed efficiency was adjusted for littering rate, L⁺W^– and L^–W⁺ were not significantly different. With regard to age at mating, the ranking for GEI (7 wk > 5 wk > 3 wk) was reversed from GEII (3 wk >5 wk > 7 wk) and these significant differences were maintained after adjustment for littering rate.Paper No. 6302 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentionedOn leave at the Institute of Animal Genetics, West Mains Road, Edinburgh EH9 3JN, Scotland. Supported, in part, by an Underwood Fund Fellowship, Agricultural Research Council, and an Edinburgh University Biological Fellowship in the Department of Genetics     

Pellet-freezing of Damascus goat semen in a chemically defined extender

During the breeding season of goats (12 bucks and 64 does) in Egypt, five experiments were conducted using a chemically defined cryoextender (CDE) to investigate: (1) the influence of rates of semen dilution (1:2, 1:4 and 1:19) and methods of thawing of frozen semen pellets (dry thawing versus wet thawing) on sperm progressive motility (SPM), sperm acrosome abnormalities (SAA) and rate of lipid peroxidation in semen as measured by malonaldehyde (MAL) production, and (2) the effect of insemination of does in natural (n = 38) and cloprostenol-synchronized (n = 26) estrus with frozen semen on their kidding rates and prolificacy. Semen (two successive ejaculates/buck) was collected twice a week via an AV and only ejaculates of >2500 x 10(6) sperm/ml and 70% SPM were diluted in one step at 30 degrees C with the CDE, cooled to 5 degrees C over a 4h-period, frozen in the form of 0.30 ml pellets and stored in liquid nitrogen for 72 h. The results revealed that post-thaw SPM of semen diluted at a rate of 1:4 was significantly (P < 0.01) higher than that of semen diluted at the other rates. Dilution of semen at a rate of 1:19 (< or =151 x 10(6) sperm/ml) not only minimized (P < 0.01) pre-freeze and post-thaw SPM, but also augmented (P < 0.01) pre-freeze and post-thaw rates of lipid peroxidation as evidenced by the high level of MAL production and the ability of antioxidants (1mg/ml EDTA, 200 U/ml bovine liver catalase, 0.61 mg/ml reduced glutathione and 0.11 mg/ml sodium pyruvate) to restore (P < 0.01) pre-freeze and post-thaw SPM. Frozen semen pellets exposed to dry thawing had a greater percentage of SPM (P < 0.01) as well as lower values of SAA and MAL (P < 0.01) than those exposed to wet thawing. Although the kidding rates did not vary significantly among does in natural (55.26%) and synchronized (53.85%) estrus, a higher (P < 0.05) prolificacy was obtained after their insemination in natural (1.81+/-0.16) rather than in synchronized (1.22+/-0.11) estrus.     

Correlated responses on growth traits after two-stage selection for ovulation rate and litter size in rabbits

Rabbit commercial maternal lines are usually selected for litter size (LS) and paternal lines for growth rate (GR). Line OR_LS was selected by ovulation rate (OR) and LS to improve LS more efficiently. In this study, growth traits of line OR_LS were evaluated by estimating the correlated response on weaning weight (WW), slaughter weight (SW) and GR during fattening period as well as their variability (DWW, DSW and DGR, respectively). Data were analyzed using Bayesian inference methods. Heritability estimates were low for growth traits (0.09, 0.13 and 0.14 for WW, SW and GR, respectively) and negligible for growth traits variability (0.01, 0.004 and 0.01 for DWW, DSW and DGR, respectively). Moderate common litter effect ratio (c²; 0.35, 0.28 and 0.27) and low maternal effect ratio (m²; 0.11, 0.05 and 0.01) were obtained for WW, SW and GR, respectively. Both c² and m² were lower at slaughter than at weaning. In addition, low common litter effect and negligible maternal effect were observed for growth traits variability. Genetic correlations between LS and both growth traits and their variability were close to zero. Positive genetic correlations were observed between OR and growth traits (0.19, 0.38 and 0.36 for WW, SW and GR, respectively) as well as between OR and growth traits variability (0.35, 0.62 and 0.20 for DWW, DSW and DGR, respectively). Positive correlated responses in both periods were obtained for growth traits, WW, SW and GR (0.037, 0.156 and 0.110 kg, respectively). The correlated response found in growth traits might be due to the positive genetic correlations between OR and these traits. However, selection for OR and LS using independent culling levels did not modify the growth traits variability. Therefore, no negative consequences on growth traits can be expected in current commercial maternal lines.     

Genetic diversity and investigation of polledness in divergent goat populations using 52 088 SNPs

The recent availability of a genome‐wide SNP array for the goat genome dramatically increases the power to investigate aspects of genetic diversity and to conduct genome‐wide association studies in this important domestic species. We collected and analysed genotypes from 52 088 SNPs in Boer, Cashmere and Rangeland goats that had both polled and horned individuals. Principal components analysis revealed a clear genetic division between animals for each population, and model‐based clustering successfully detected evidence of admixture that matched aspects of their recorded history. For example, shared co‐ancestry was detected, suggesting Boer goats have been introgressed into the Rangeland population. Further, allele frequency data successfully tracked the altered genetic profile that has taken place after 40 years of breeding Australian Cashmere goats using the Rangeland animals as the founding population. Genome‐wide association mapping of the POLL locus revealed a strong signal on goat chromosome 1. The 769‐kb critical interval contained the polled intersex syndrome locus, confirming the genetic basis in non‐European animals is the same as identified previously in Saanen goats. Interestingly, analysis of the haplotypes carried by a small set of sex‐reversed animals, known to be associated with polledness, revealed some animals carried the wild‐type chromosome associated with the presence of horns. This suggests a more complex basis for the relationship between polledness and the intersex condition than initially thought while validating the application of the goat SNP50 BeadChip for fine‐mapping traits in goat.     

Multi-male mating, probability of conception, and litter size in the prairie vole (Microtus ochrogaster)

We conducted a mating experiment in the laboratory using prairie voles, Microtus ochrogaster, to document that multi-male mating (MMM) can occur in this supposedly monogamous species and to test two hypotheses for the advantages of MMM in female mammals. The two hypotheses are that MMM (1) increases the probability of pregnancy and (2) increases litter size. We also tested the hypothesis that multiple copulations, rather than multiple partners, increases litter size and/or probability of pregnancy. Females were given a choice of mating with any of three males, each of which was tethered in a separate compartment. The mate choice bouts were recorded on videotape. We recorded the number of copulations and number of males with which females mated over a 24 h period. Litter size and probability of pregnancy were not significantly different for females that mated with one, two or three males. Increasing numbers of copulations, independent from the number of males, also did not increase litter size but did significantly increase the probability of pregnancy. MMM, at least in prairie voles, must serve some function other than increasing litter size and probability of conception.     

The relationship of semen quality to pregnancy rate and litter size following artificial insemination in the bitch

Artificial insemination of 31 bitches with fresh, undiluted, semen resulted in 22 31 conceptions (71%) and the birth of 124 puppies. Inseminations using at least 220 x 10(6) spermatozoa of normal morphology resulted in a mean pregnancy rate of 81.5% (22 27 ). The pregnancy rates were significantly influenced by the total number of progressively motile or morphologically normal sperm cells per ejaculate (P < 0.05). The pregnancy rate was not influenced by the percentage of progressively motile or morphologically normal sperm cells per ejaculate (P > 0.1). Litter size was not influenced by sperm motility or morphology (P > 0.1).     

LH receptor induction and ovulation rate in mice selected for litter size and body weight

Female mice from lines which had undergone long-term single trait and antagonistic index selection for litter size and body weight were analysed for ovulation rate and LH receptor induction. Compared to randomly selected controls, selection for large litter size increased ovulation rate (60%; P less than 0.001) and decreased LH receptor induction per microgram ovarian DNA (87%; P less than 0.01). Selection for large body weight increased ovulation rate (18%; P less than 0.001), but did not lead to a significant correlated response in LH receptor induction. Index selection for large litter size and small body weight increased ovulation rate (14%; P less than 0.01) and decreased LH receptor induction (72%; P less than 0.01), while index selection for small litter size and large body weight did not significantly alter either ovulation rate or LH receptor induction. LH receptor quantities in testes of males from the 5 lines did not exhibit the among-line profile which was observed in ovaries of females. These results confirm the role of ovulation rate in mediation of the positive genetic correlation between litter size and body weight in mice. Increased ovulation rate in mice selected for large litter size may be due to mechanisms associated with LH receptors as well as factors related to growth. In contrast, increased ovulation rate in mice selected for large body weight may be due exclusively to factors related to growth.     

Effect of the buck on number of services per conception,service period and litter size at birth in Bauscat rabbits

A non-significant buck effect on the number of services per conception, service period and litter size at birth in Bauscat rabbits was found using 66 bucks. The within-buck repeatability of number of services per conception and service period of 0.027 ± 0.028 and 0.035 ± 0.029, respectively, were non-significant. The same parameter for litter size at birth could not be obtained because of the negative buck component of variance observed. For this population of rabbits it appeared that no difference in these traits existed among bucks and, as a result, improvement in these traits could not be made by selection of bucks based on their own performance.     

Association analysis of the INHA gene with litter size in Boer goats

This study investigated the association between differences in litter size in Boer does, with genetic polymorphisms in the inhibin alpha gene. Our preliminary (n = 209) results found 12 SNPs, including the non-synonymous polymorphisms 911T/C and 946A/C, resulting in corresponding 299V/A and 311T/P amino acid polymorphisms. Of the SNPs, 651A/G was preliminarily suggested as a useful marker for litter size of the second parity in the population studied, showing an overdominance effect. Polymorphisms, sequence, and genotype distributions were also characterized.