Increased Litter Size Research Articles

In vivo experiments reveal the good, the bad and the ugly faces of sFlt-1 in pregnancy.

ObjectiveSoluble fms-like tyrosine kinase (sFlt)-1-e15a, a primate-specific sFlt-1-isoform most abundant in the human placenta in preeclampsia, can induce preeclampsia in mice. This study compared the effects of full-length human (h)sFlt-1-e15a with those of truncated mouse (m)sFlt-1(1-3) used in previous preeclampsia studies on pregnancy outcome and clinical symptoms in preeclampsia.MethodsMice were injected with adenoviruses or fiber-mutant adenoviruses overexpressing hsFlt-1-e15a, msFlt-1(1-3) or control GFP under the CMV or CYP19A1 promoters on gestational day 8 (GD8) and GD11. Placentas and pups were delivered by cesarean section, and dams were monitored postpartum. Blood pressure was telemetrically recorded. Urine samples were collected with cystocentesis and examined for albumin/creatinine ratios. Tissue specimens were evaluated for transgene as well as endogenous mFlt-1 and msFlt-1-i13 expression. H&E-, Jones- and PAS-stained kidney sections were histopathologically examined. Placental GFP expression and aortic ring assays were investigated with confocal microscopy.ResultsMean arterial blood pressure (MAP) was elevated before delivery in hsFlt-1-e15a-treated mice compared to controls (GD18: ΔMAP = 7.8 mmHg, p = 0.009), while ΔMAP was 12.8 mmHg (GD18, p = 0.005) in msFlt-1(1-3)-treated mice. Urine albumin/creatinine ratio was higher in hsFlt-1-e15a-treated mice than in controls (GD18, p = 0.04; PPD8, p = 0.03), and msFlt-1(1-3)-treated mice had marked proteinuria postpartum (PPD8, p = 4×10−5). Focal glomerular changes were detected in hsFlt-1-e15a and msFlt-1(1-3)-treated mice. Aortic ring microvessel outgrowth was decreased in hsFlt-1-e15a (p = 0.007) and msFlt-1(1-3)-treated (p = 0.02) mice. Full-length msFlt-1-i13 expression was unique for the placenta. In hsFlt-1-e15a-treated mice, the number of pups (p = 0.046), total weight of living pups (p = 0.04) and maternal weights (p = 0.04) were higher than in controls. These differences were not observed in truncated msFlt-1(1-3)-treated mice.ConclusionsTruncated msFlt-1(1-3) simulated the preeclampsia-promoting effects of full-length hsFlt-1. MsFlt-1(1-3) had strong effect on maternal endothelium but not on placentas and embryos. In contrast, hsFlt-1-e15a induced preeclampsia-like symptoms; however, it also increased litter size. In accord with the predominant placental expression of hsFlt-1-e15a and msFlt-1-i13, full-length sFlt-1 may have a role in the regulation of embryonic development. These observations point to the difference in the biological effects of full-length and truncated sFlt-1 and the changes in the effect of full-length sFlt-1 during pregnancy, and may have important implications in the management of preeclampsia.

Relationships among sow productivity traits within purebred and crossbred litters

The purpose of this study was to evaluate the relationships of litter weaning weight (LWW), number weaned (NW), mean pig weaning weight (PWT), litter birth weight (LBW), and survival percentage (%S) with number after transfer (NAT) and number born alive (NBA) on purebred and crossbred litters. Data consisted of purebred Duroc (29,297), Landrace (34,177), and Yorkshire litters (40,301) as well as Yorkshire×Landrace (8061) and Landrace×Yorkshire (4028) crossbred litters. The data were distributed into 4 time periods of 1980 through 1997, 1998 through 2002, 2003 through 2008, and 2009 through 2011. All variables were initially modeled with the fixed effects of litter breed, period, NAT, farm, parity-age class (P-AC) groupings and interactions, and random effects of sow and contemporary group. Non-significant variables and interactions (P>0.05) were removed from final models. Periods 1 and 2 as well as 3 and 4 were combined based on non-significant main effects and interactions. The effect of NAT on LWW differed by time period (P<0.01) such that heavier litters were achieved at larger litter sizes (NAT>11) in Landrace and Yorkshire litters (P<0.05) in period 2. Mean PWT decreased as NAT increased with less effect on PWT during the second time period. Also %S decreased in a linear fashion from 6 to 12 NAT then decreased at an increasing rate for NAT>12, with a slight increase in %S over time for all breeds. Number weaned increased in a linear fashion up to NAT equal to 11 then increased at a decreasing rate to a maximum value depending on breed; above that value of NAT, NW decreased. There were no significant (P>0.05) NBA by parity interactions for traits that were measured after processing and transfer. In every statistical analysis, farm was a significant and major source of variation. Also %S, and NW were greatly affected by NAT, and LBW was greatly affected by total number of pigs born (TNB). As litter size increases, greater emphasis should be placed on preweaning survival. The data indicate the effects of NAT on LWW, and PWT should be revaluated periodically.

Desempeño reproductivo de cerdas primerizas suplementadas con riboflavina durante la gestación

Para evaluar los efectos en el tamaño de lechigada y la expresión del factor de crecimiento endotelial vascular (VEGF; por sus siglas en inglés) y de la uteroferrlna, cerdas primerizas cruzadas (n = 24) se suplementaron con 0 o 60 mg de riboflavina diariamente durante toda la gestación. El tamaño de la lechigada y el peso individual de las crías se determinó al nacer y al destete. Se colectaron muestras de placenta al momento del parto para determinar la expresión relativa del VEGF y de la uteroferrina. Las cerdas suplementadas y no suplementadas parieron 11.2 ± 0.6 y 8.2 ± 0.6 cerditos totales, respectivamente (P &lt; 0.004). Hubo diferencias análogas en el número de cerditos nacidos vivos de 10.5 ± 0.6 contra 8.1 ± 0.6 (P &lt; 0.01) y en el número total de cerditos destetados (9.41 ± 0.6 y 7.5 ± 0.6, P &lt; 0.05). Se encontró diferencia entre los tratamientos para el peso total de la lechigada al nacer pero no al destete. La expresión relativa del VEGF fue mayor (P &lt; 0.07) en la placenta de cerdas suplementadas con riboflavina que en las controles, pero los tratamientos no difirieron en la expresión relativa de la uteroferrina. Los resultados presentes indican que la suplementación con 60 mg diarios de riboflavina a cerdas primerizas durante la gestación puede incrementar el tamaño de la lechigada, quizás mediado por una mejor vascularización de la placenta y por consiguiente mejorando la supervivencia del embrión/feto.

Evaluation of quantitative trait loci affecting intramuscular fat and reproductive traits in pigs using marker-assisted introgression.

We investigated the effects of previously identified quantitative trait loci (QTL) in an experimental backcross (BC) between Chinese Meishan pigs and commercial Duroc pigs. We performed marker-assisted introgression of two QTL for intramuscular fat (IMF) content (IMF population) and three QTL for reproductive traits (reproduction population) from a donor Meishan pig into a recipient Duroc pig. At the fourth BC generation of the IMF population and third BC generation of the reproduction population, carrier animals were selected for the production of animals homozygous for the QTL. Our previous studies have shown that the presence of a Meishan allele on the IMF QTL is associated with low IMF values, and the Meishan allele on the reproductive QTL is associated with large litters. In this study, the presence of a Duroc allele at the IMF QTL on SSC9 resulted in a 0.27% increase in IMF (additive effect = 0.27 ± 0.08), whereas the presence of a Meishan allele at the IMF QTL on SSC7 resulted in a 0.34% increase in IMF (additive effect = -0.34 ± 0.09). The presence of the Meishan allele at the IMF QTL on SSC7 thus had the opposite effect to our previous studies, that is, increased IMF. In the reproduction population, we observed no differences between the genotypes of the three QTL in regard to number of corpora lutea or litter size. Marker-assisted introgression at these QTL is thus unlikely to result in an associated increase in litter size. These results show that it is possible to introgress alleles from other breeds into a selection population using molecular markers; any unexpected results might be associated with the genetic background.

Increased litter size and suckling intensity inhibit KiSS-1 mRNA expression in rat arcuate nucleus.

The effect of litter size and suckling intensity on the expression of KiSS-1 mRNA in the arcuate nucleus (ARC) of rats were evaluated. Thirty two pregnant and four non-lactating ovariectomized (as control group) rats were used in this experiment. Lactating rats were allotted to eight equal groups. In three groups, litter size was adjusted to 5, 10, or 15 pups upon parturition and allowed to suckle their pups continuously by 8 days postpartum. In the other three groups, litter size was adjusted to five upon birth; the pups were separated from the dams for 6 hr on day 8 postpartum, after which the pups were allowed to suckle their dams for 2.5, 5, or 7.5 min prior to killing the dams. Two groups of lactating rats with either 10 or 15 pups were separated from their pups for 6 hr on day 8 postpartum, after which the pups were allowed to suckle their dams for 5 min before the dams were killed on day 8 postpartum. The ARC was removed and the expression of KiSS-1 mRNA was evaluated, using real-time PCR. The expression of KiSS-1 mRNA in the ARC was decreased as the litter size and intensity of suckling stimulus were increased. The effect of suckling intensity on the expression of KiSS-1 mRNA was more pronounced than that of litter size. Increased litter size and suckling intensity decreased KiSS-1 mRNA expression in the ARC which may contribute to lactation anestrus in rat.

Genomic analysis reveals selection for Asian genes in European pigs following human-mediated introgression.

The independent domestication of local wild boar populations in Asia and Europe about 10,000 years ago led to distinct European and Asian pig breeds, each with very different phenotypic characteristics. During the Industrial Revolution, Chinese breeds were imported to Europe to improve commercial traits in European breeds. Here we demonstrate the presence of introgressed Asian haplotypes in European domestic pigs and selection signatures on some loci in these regions, using whole genome sequence data. The introgression signatures are widespread and the Asian haplotypes are rarely fixed. The Asian introgressed haplotypes are associated with regions harbouring genes involved in meat quality, development and fertility. We identify Asian-derived non-synonymous mutations in the AHR gene that associate with increased litter size in multiple European commercial lines. These findings demonstrate that increased fertility was an important breeding goal for early nineteenth century pig farmers, and that Asian variants of genes related to this trait were preferentially selected during the development of modern European pig breeds.

English

This study was conducted at the grasscutter section of the University of Education, Winneba, Ghana, to estimate non-genetic effects on reproductive and survival traits. Data consisted of records on 136 does from 2006 to 2010. Litter size at weaning, litter weight and lactation weight loss all increased (P &lt; 0.01) with increasing litter size at birth. Litter weight and lactation weight loss increased (P &lt; 0.05) at weaning, whilst days of joining decreased (P &lt; 0.01), with increasing years. Minor rainy season was found to be the most suitable mating season. Dams that kidded in dry season took fewer (P &lt; 0.05) days to conceive than in other seasons. Nursing dams lost more (P &lt; 0.05) weight in dry and minor rainy seasons than in major rainy season. Increasing parity led to decreasing (P &lt; 0.05) pre-weaning survival of offspring. Post-weaning survival of offspring decreased (P &lt; 0.01) with increasing years. Kids conceived in the minor rainy and dry seasons had significantly higher (P &lt; 0.05) post-weaning survival rates than those conceived in the major rainy season. Post-weaning survival rates of kids born in the minor rainy season were lower (P &lt; 0.05) than those born in other seasons. It was concluded that non-genetic factors influenced fitness traits and must therefore be considered when designing grasscutter breeding programmes. &nbsp; Key words: Domestication, environmental factors, reproduction, rodent.

Genetic parameters for litter size in Black Slavonian pigs

The objective of this study was to estimate genetic parameters for litter size of Black Slavonian pigs using the repeatability, multiple trait, and random regression models, and to consider the possibility to increase litter size in Black Slavonian pigs by selection. A total of 4733 litter records from the first to the sixth parity from sows that farrowed between January 1998 and December 2010 were included in the analysis. Individual record consisted of the following variables: breeding organisation (eight regions), parity (1-6), service boar, and farrowing season (month-year interaction). Estimation of all the covariance components with three different models was based on the residual maximum likelihood method. Estimate of additive genetic variance and heritability for number of piglets born alive with repeatability model was 0.23 and 0.10, respectively. Estimates of additive genetic variance with multiple trait and random regression model were in a wider range from 0.05 to 0.65 across parities, and heritabilities were estimated in the range between 0.03 and 0.26. Estimates of phenotypic and additive genetic correlations were much smoother with random regression model in comparison with multiple trait model. Due to unexpected changes of variances along trajectory obtained with multiple trait and random regression model, the best option for genetic evaluation of litter size for now could be the use of repeatability model. With increasing number of data with proper data structure alternative modelling of litter size of Black Slavonian pig using multiple trait and random regression model could be taken into consideration.

Heterosis in the second and third generation affects litter size in a crossbreed mink (Neovison vison) population

Litter sizes in a cross between Brown and Black mink color types were observed through six generations. Litter size was significantly affected by yearly environmental variations. After adjusting for year effects, we found significant increases in litter size in the second and third generations (F2 and F3) after crossing. Thereafter, in the following generations, litter size dropped to a level comparable to the mean litter size of the midparent. Increased litter size in F2 compared to F1 indicated that maternal effects influenced litter size more than non-maternal effects. The heterosis was mainly caused by an increase in litter size compared to the Black parental line. This indicates that the Black line was affected by inbreeding depression prior to crossing. We also found that two-year old F1 females had significantly more offspring compared to one-year old F1 females.

High-resolution association mapping of number of teats in pigs reveals regions controlling vertebral development.

BackgroundSelection pressure on the number of teats has been applied to be able to provide enough teats for the increase in litter size in pigs. Although many QTL were reported, they cover large chromosomal regions and the functional mutations and their underlying biological mechanisms have not yet been identified. To gain a better insight in the genetic architecture of the trait number of teats, we performed a genome-wide association study by genotyping 936 Large White pigs using the Illumina PorcineSNP60 Beadchip. The analysis is based on deregressed breeding values to account for the dense family structure and a Bayesian approach for estimation of the SNP effects.ResultsThe genome-wide association study resulted in 212 significant SNPs. In total, 39 QTL regions were defined including 170 SNPs on 13 Sus scrofa chromosomes (SSC) of which 5 regions on SSC7, 9, 10, 12 and 14 were highly significant. All significantly associated regions together explain 9.5% of the genetic variance where a QTL on SSC7 explains the most genetic variance (2.5%). For the five highly significant QTL regions, a search for candidate genes was performed. The most convincing candidate genes were VRTN and Prox2 on SSC7, MPP7, ARMC4, and MKX on SSC10, and vertebrae δ-EF1 on SSC12. All three QTL contain candidate genes which are known to be associated with vertebral development. In the new QTL regions on SSC9 and SSC14, no obvious candidate genes were identified.ConclusionsFive major QTL were found at high resolution on SSC7, 9, 10, 12, and 14 of which the QTL on SSC9 and SSC14 are the first ones to be reported on these chromosomes. The significant SNPs found in this study could be used in selection to increase number of teats in pigs, so that the increasing number of live-born piglets can be nursed by the sow. This study points to common genetic mechanisms regulating number of vertebrae and number of teats.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-542) contains supplementary material, which is available to authorized users.

The Buserelin Enigma; How Does Treatment with this GnRH Analogue Decrease Embryo Mortality?

The use of the GnRH analogue buserelin administered in mid dioestrus has been shown to increase early pregnancy rate, reduce embryo loss and increase litter size in several species. The mechanism by which this works is unclear and may differ between species. In cattle it is believed that buserelin, by reducing oestrogen concentrations, causes the development of endometrial oxytocin receptors to be delayed. Luteal oxytocin binds with these receptors to promote the formation and secretion of prostaglandin. Any delay in the release of PGF2α would allow an underdeveloped embryo extra time to produce and release the maternal recognition of pregnancy signal, which might otherwise be lost following luteolysis. This may also be the mechanism in sheep and pigs although an increase in progesterone concentrations could also be important. However in the mare, following buserelin administration at 9 or 10 days after the detection of ovulation, pregnancy rates are already increased by 12-13 days compared with untreated controls, i.e. before the time of luteolysis, without any change in progesterone concentrations. In addition to an increased pregnancy rate, the twin embryo rate is also increased and subsequent embryo loss rate reduced. The possible mechanisms by which this may result in the mare are discussed.

Neonatal piglet survival: impact of sow nutrition around parturition on fetal glycogen deposition and production and composition of colostrum and transient milk

Piglet survival is a major problem, especially during the first 3 days after birth. Piglets are born deficient of energy, but at the same time they have a very high energy requirement because of high physical activity, high need for thermoregulation (because of their lean body with low insulation) and high heat production in muscle tissues. To be able to survive, newborn piglets may rely upon three different sources of energy, namely, glycogen, colostrum and transient milk, which orchestrate to cover their energy requirements. Piglets are born with limited amounts of energy in glycogen depots in the liver and muscle tissues and these depots are sufficient for normal activity for ∼16 h. Intake and oxidation of fat and lactose from colostrum must supply sufficient amount of energy to cover at least another 18 h until transient milk becomes available in the sow udder ∼34 h after the first piglet is born. Selection for large litters during the last two decades has challenged piglets even further during the critical neonatal phase because the selection programs indirectly decreased birth weight of piglets and because increased litter size has increased the competition between littermates. Different attempts have been made to increase the short-term survival of piglets, that is, survival until day 3 of lactation, by focusing on improving transfer of vital maternal energy to the offspring, either in utero or via mammary secretions. Thus, the present review addresses how sow nutrition in late gestation may favor survival of newborn piglets by increasing glycogen depots, improving colostrum yield or colostrum composition, or by increasing production of transient milk.

Feeding behaviour of artificially reared Romane lambs

A consequence of increasing litter size in sheep is that a portion of the lambs have to be reared artificially. Detailed information about the pattern of milk consumption of artificially reared lambs would help improve their management. The purpose of this study is to describe the individual and group feeding behaviour of 94 Romane artificially reared lambs from 5 to 28 days of age using an electronic automatic lamb feeder. Animals were located in four pens of 8 to 15 lambs of similar age with one teat per pen. They were fed ad libitum. In our experimental situation (group rearing, continuous lightning) on average a lamb made 1.4±0.7 visits to the teat per meal and 9.5±3 meals per day. Mean meal duration was 247±158 s and the mean daily time spent feeding was 38±25 min. The mean quantity of milk intake was 176±132 ml per meal and 1.68±0.8 l per day. With age, the number of daily meals and their duration decreased while the quantity of milk consumed per meal and per day increased. Females tended to make more visits to the teat per meal and perform more meals per day but their milk consumption per meal was lower. The feed conversion ratio was 1.36±0.2. Synchrony in feeding (group meal) was estimated as the percentage of lambs that wanted to access the teat within the same short period (relative group meal size). On average 65% of lambs in the pen wanted to access the teat within the same period, but for 35% of group meals the relative group meal size was >90%. There was no consistency in the order in which lambs accessed the teat during a group meal. Our evaluation suggested that electronic automatic lamb feeders are tools that can provide, on a large scale, data describing the feeding behaviour of artificially reared lambs. It is then possible to study factors influencing these traits in order to improve the outcome of artificially reared lambs.

Different resource allocation strategies result from selection for litter size at weaning in rabbit does

This study examined the effect of long-term selection of a maternal rabbit line, solely for a reproductive criterion, on the ability of female rabbits to deal with constrained environmental conditions. Female rabbits from generations 16 and 36 (n=72 and 79, respectively) of a line founded and selected to increase litter size at weaning were compared simultaneously. Female rabbits were subjected to normal (NC), nutritional (NF) or heat (HC) challenging conditions from 1st to 3rd parturition. Animals in NC and NF were housed at normal room temperatures (18°C to 25°C) and respectively fed with control (11.6 MJ digestible energy (DE)/kg dry matter (DM), 126 g digestible protein (DP)/kg DM, and 168 g of ADF/kg DM) or low-energy fibrous diets (9.1 MJ DE/kg DM, 104 g DP/kg DM and 266 g ADF/kg DM), whereas those housed in HC were subjected to high room temperatures (25°C to 35°C) and the control diet. The litter size was lower for female rabbits housed in both NF and HC environments, but the extent and timing where this reduction took place differed between generations. In challenging conditions (NF and HC), the average reduction in the reproductive performance of female rabbits from generation 16, compared with NC, was −2.26 (P<0.05) and −0.51 kits born alive at 2nd and 3rd parturition, respectively. However, under these challenging conditions, the reproductive performance of female rabbits from generation 36 was less affected at 2nd parturition (−1.25 kits born alive), but showed a greater reduction at the 3rd parturition (−3.53 kits born alive; P<0.05) compared with NC. The results also showed differences between generations in digestible energy intake, milk yield and accretion, and use of body reserves throughout lactation in NC, HC and NF, which together indicate that there were different resource allocation strategies in the animals from the different generations. Selection to increase litter size at weaning led to increased reproductive robustness at the onset of an environmental constraint, but failure to sustain the reproductive liability when the challenge was maintained in the long term. This response could be directly related to the short-term environmental fluctuations (less severe) that frequently occur in the environment where this line has been selected.

Characterization of an animal model of pregnancy-induced vitamin D deficiency due to metabolic gene dysregulation

Vitamin D deficiency has been associated with pregnancy complications such as preeclampsia, gestational diabetes, and recurrent miscarriage. Therefore, we hypothesized differences in vitamin D status between healthy [Sprague-Dawley (SD) and Lewis (LW)] and complicated [Brown Norway (BN)] rat pregnancies. In SD, LW, and BN rats, we analyzed the maternal plasma levels of the vitamin D metabolites 25-OH-D and 1,25-(OH)2-D at prepregnancy, pregnancy, and postpartum. Analysis of the active metabolite 1,25-(OH)2-D showed a twofold increase in pregnant SD and LW rats but a nearly 10-fold decrease in pregnant BN rats compared with nonpregnant controls. BN rats had a pregnancy-dependent upregulation of CYP24a1 expression, a key enzyme that inactivates vitamin D metabolites. In contrast, the maternal renal expression of CYP24a1 in SD and LW rats remained constant throughout pregnancy. Analysis of the vitamin D receptor (VDR) indicated that LW and SD but not BN rats experience a pregnancy-induced 10-fold decrease in maternal renal VDR protein levels. Further analysis of bisulfite-converted and genomic DNA indicated that the observed differences in maternal renal regulation of CYP24a1 during pregnancy and lactation are not due to differences in CYP24a1 promoter methylation or single-nucleotide polymorphisms. Finally, supplementation with 1,25-(OH)2-D significantly improved the reproductive phenotype of BN rats by increasing litter size and maternal-fetal weight outcomes. We conclude that BN rats represent a novel animal model of pregnancy-specific vitamin D deficiency that is linked to pregnancy complications. Vitamin D deficiency in BN rats correlates with maternal renal CYP24a1 upregulation followed by CYP27b1 upregulation.

Nutritional interventions to prevent and rear low‐birthweight piglets

Selection for hyperprolific sows, as a means of increasing litter size and profit, has resulted in an increased number of low-birthweight (LBW) piglets. These LBW piglets might suffer from increased morbidity and mortality during the early neonatal period. In addition, they show reduced growth performance, meat and carcass quality, which leads to an important economic loss for the farmer in the post-natal period. Therefore, nutritional interventions can be undertaken to prevent and rear LBW piglets. In the first part of this review, the preventive strategies at the sow level will be discussed. Approaches in preventing LBW piglets are to optimize the intrauterine environment via supplementing the sow during gestation. In the second part of this review, the interventions at the piglet level will be described. To increase the survival and growth rates of LBW piglets, one must focus on ensuring adequate colostrum and milk intake. Interventions include supplementing piglets, split nursing, split weaning and cross-fostering. Additional interventions increasing the probability of optimal post-natal food intake will be discussed.

Energetics of hibernation and reproductive trade-offs in brown bears

Brown bears give birth and nurture their young for the first 3–5 months while fasting in hibernation. During this period, bears use body reserves to support the energy and protein costs of reproduction. Limited reserves may restrict reproductive investment. We developed a model to assess the energetic costs of reproduction during hibernation and to determine how maternal condition, length of lactation, litter size, and length of hibernation affect brown bear reproductive success. Increasing litter size by one cub was more costly than increasing the lactation period by 14 days. For hibernating females, ∼73% of their mass loss during lactation was lean mass. Minimum levels of fat reserves necessary to support reproduction varied from 19% to 33% depending on number of cubs and length of lactation while denned. Reproduction was not possible if body fat content was below 19% and length of hibernation was over 120 days. While the importance of fat or energy reserves at the beginning of hibernation has been long recognized, the importance of consuming high-protein foods after hibernation may be equally important. Therefore, more attention should be given to understanding pre- and post-hibernation nutritional factors affecting reproduction and the trade-offs between available food resources, maternal condition, and reproductive investment and success in wild bear populations.

Oral vaccination with inhibin DNA delivered using attenuated Salmonella choleraesuis for improving reproductive traits in mice

The objective of this study was to examine the efficacy and safety of a novel inhibin vaccine containing inhibin α (1-32) fragments in mice. A recombinant plasmid pVAX-asd-IS was constructed by inserting recombinant inhibin α (1-32) and the hepatitis B surface antigen S into the plasmid in which the asd gene, rather than the kanamycin gene, was a selection marker. Ninety Kuming mice were divided into six groups consisting of 15 mice each. First group was (C1) injected with 200 µl of PBS, second (C2) received 1 × 10(10) CFU of crp(-) /asd(-) C500/pVAX-asd and served as vector control, third did not receive any treatment (C3), while fourth, fifth, and sixth group received 1 × 10(10) , 1 × 10(9) , 1 × 10(8) CFU of the recombinant inhibin vaccine crp(-) /asd(-) C500/pVAX-asd-IS (group T1, T2, T3), respectively. Western blotting demonstrated that recombinant expressed inhibin protein possessed immune function and that this plasmid could replicate for up to 40 generations stably. Vaccination with this strain at a dose of 1 × 10(10) CFU/200 µl per mouse induced high anti-inhibin antibody levels, significantly increased large-follicle production in T1 group (p < 0.05) and average litter size (p > 0.05) compared with control groups. Integration studies showed no evidence of inhibin fusion gene integrated into mice's genome 2-month after immunization. These results suggest that the vaccine described in the present study may provide a safe method to improve reproductive traits in animals. A trend towards increased litter size and significant increase in large follicle population depict that this vaccine may have direct application in large animal industry.

Why do female mice mate with multiple males?

Females often show multi-male mating (MMM), but the adaptive functions are unclear. We tested whether female house mice (Mus musculus musculus) show MMM when they can choose their mates without male coercion. We released 32 females into separate enclosures where they could choose to mate with two neighboring males that were restricted to their own territories. We also tested whether females increase MMM when the available males appeared unable to exclude intruders from their territories. To manipulate territorial intrusion, we introduced scent-marked tiles from the neighboring males into males' territories, or we rearranged tiles within males' own territories as a control. Each female was tested in treatment and control conditions and we conducted paternity analyses on the 57 litters produced. We found that 46 % of litters were multiply sired, indicating that multiple paternity is common when females can choose their mates. Intrusion did not increase multiple paternity, though multiple paternity was significantly greater in the first trial when the males were virgins compared to the second trial. Since virgin male mice are highly infanticidal, this finding is consistent with the infanticide avoidance hypothesis. We also found that multiple paternity was higher when competing males showed small differences in their amount of scent marking, suggesting that females reduce MMM when they can detect differences in males' quality. Finally, multiple paternity was associated with increased litter size but only in the intrusion treatment, which suggests that the effect of multiple paternity on offspring number is dependent on male–male interactions.

Genetic correlations between lactation performance and growing-finishing traits in pigs

Genetic selection for increased litter size of sows increases the risk of a large negative energy balance during lactation. Furthermore, the feed intake capacity of the lactating sows might be reduced due to the simultaneous selection for greater feed efficiency during the growth phase when sows were actually reared as finishers but later on selected for breeding. There is a need to improve lactation performance of sows and continue selection for feed efficiency of grower-finishers in commercial breeding. Therefore, this study was conducted to estimate genetic correlations between growing-finishing traits and lactation performance traits. An additional objective was to study the impact of including additive social effects in the animal model on genetic correlation estimates. Analyses were performed on a population of 1,149 commercial crossbred sows with repeated observations on lactation performance traits and their 7,723 grower-finisher offspring. The genetic correlation between daily BW gain of grower-finishers and starting BW of lactating sows was positive (rg = 0.24; P < 0.05). The correlation between off-test backfat of grower-finishers and fat mass of lactating sows was also positive (rg = 0.53; P < 0.05). The genetic regulation of feed intake from the beginning of lactation seems to differ from the genetic regulation of feed intake during the growing-finishing period, as the correlation between these 2 traits was low (rg = +0.23; P < 0.05). Feed efficiency during growing-finishing and lactation phases showed similar tendencies as the genetic correlation between residual feed intake of the grower-finisher and lactation efficiency of sows was -0.51 (P < 0.05). Taking heritable social effects into account for daily BW gain and feed intake did not affect the genetic correlation estimates, either within growing-finishing traits or between growing-finishing traits and lactation performance traits. It was concluded that in the absence of antagonistic genetic correlations, selection for growing-finishing traits in dam lines could be combined with selection for lactation performance traits.