Large Litters Research Articles

Effects of genotype, gestation length and litter size on the birth weight, litter weight, pre- and post-weaning weight of crossbred kits

BackgroundPerformance of rabbit is hinged on many factors of which the birth weights, gestation length and the litter size are most important. Linear body traits provide vital information on the performance, productivity and carcass characteristics which could be useful tool for the improvement in genetic potentials of rabbits. Therefore, this study investigated the effects of genotype, gestation length and litter size on the birth weight, pre- and post-weaning weight of crossbred kits.ResultsFive breeds: Rex (RX), Dutch-belted (DBT), New Zealand white (NZW), Californian white (CFW) and local breed (LAB) of rabbit were used for the study. A foundation stock of 40 growing rabbits consisting of six does and two bucks were used for the crossing experiment. Genotype exerted significant influence (P < 0.01) on the litter weight at birth as well as on the body weight of the kits at 21st and 35th days. The kit kindled from mating CFWxDBT breeds had the highest mean body weight from birth (91.90 ± 9.84 g) to 35th days (368.25 ± 17.36 g), while the crosses of DBTxCFW recorded the least mean body weight from birth (74.25 ± 1.78 g) to 35th days (332.60 ± 12.54 g). Gestation length significantly (P < 0.05) influenced individual and litter birth weights, pre- and post-weaning weights of kits. Does with short gestation length (29 days) had kits with light body weight compared to those with longer period of gestation (34 days). More so, kits belonging to large litter size (7) had the lowest body weight at birth as well as 21st and 35th day (69.93 ± 1.63 g, 209.57 ± 3.70 g, 319.11 ± 9.22 g) compared to kits that belonged to small litter group size. Highly significant (P < 0.01) and the strongest phenotypic relationships were recorded between body weight at day 21 and day 35 for all crosses, while weak and negative genetic correlation (r = − 0.19) was observed between litter birth weight and individual birth weight of crossbred kits.ConclusionCrossbreeding produces offspring with better performances. Birth weight of kits is a prediction tool for the overall performance of rabbits provided the environment is uninterrupted.

Multiple aspects of the maternal reproductive investment in a polytocous species: What do mothers really control?

One of the factors facilitating the expansion and proliferation of wild boar Sus scrofa is the plasticity of its reproductive biology. Nevertheless, the real influence of maternal and environmental factors on number and sex of the offspring is still controversial. While the litter size was shown to be related with the maternal condition, the strength of this relation remains to be understood, together with the possible role played by environmental conditions. Analogously, it is unclear whether wild boar females can adjust their offspring sex. We investigated multiple aspects of wild boar maternal investment by means of a 10-year dataset of female reproductive traits and a set of biologically meaningful environmental variables. The maternal condition slightly affected the litter size but not the offspring sex, and environment did not affect the litter size or the offspring sex. Moreover, mothers did not cope with the higher costs entailed by producing sons by placing them in the most advantageous intrauterine position, nor by allocating less resources on daughters. Our set of results showed that the female reproductive investment is quite rigid in comparison with other aspects of wild boar reproductive biology. Wild boar females seem to adopt a typical r-strategy, producing constantly large litters and allocating resources on both sexes regardless of internal and external conditions. Such strategy may be adaptive to cope with environmental unpredictability and an intense human harvest, contributing to explain the extreme success of wild boar within human-dominated landscapes.

Improving young pig welfare on-farm: The Five Domains Model.

Considering welfare through the "neonatal and nursery pig perspective" is an exciting approach and one that resonates with consumers. Overlaying this with the Five Domains Model, as we suggest in this review, points to practical on-farm improvements that provide each pig the opportunity to experience positive mental states. The Five Domains Model is broken into physical and functional states, which include Domain 1: Nutrition, Domain 2: Physical Environment, Domain 3: Health, and Domain 4: Behavioral Interaction, and Domain 5: Mental State. The Five Domains Model can build on the breadth and depth of swine welfare science to highlight opportunities to improve welfare on-farm. In Domain 1, management of increasingly large litters is considered, with examples of sow vs. artificial rearing, colostrum quality and quantity, and creep feed management strategies. Efforts can result in positive mental states such as feeling full and content and the ability to experience the pleasure of drinking and food tastes and smells. Domain 2 considers space complexity and access to key resources, along with thermal and physical amenities, to promote feelings of physical comfort. Domain 3 considers pig health in three broads, yet inter-linking categories 1) congenital and hereditary health, 2) environmental pathogen load, and 3) colostrum quality and quantity, and its effect on the microbiome. Improvements can result in a pig that displays vitality and feels healthy. Domain 4 provides the pig opportunities to express its rich behavioral repertoire, specifically positive social interactions, play, and exploration. These efforts can result in pigs feeling calm, safe, comfortable, having companionship, engaged, interested, and rewarded. In conclusion, using the Five Domains Model can highlight numerous opportunities to improve current and future housing and management through the "neonatal and nursery pig perspective" with a focus on inducing positive mental states that can result in improved quality of life and welfare state.

Body weight of newborn and suckling piglets affects their intestinal gene expression.

Modern hyperprolific sows must deal with large litters (16–20 piglets) which reduce piglet birthweight with a concomitant increase in the proportion of small and intrauterine growth retarded piglets. However, larger litters do not only have a greater variation of piglet weights, but also a greater variation in colostrum and milk consumption within the litter. To further understand the impact that body weight has on piglets, the present study aimed to evaluate the degree of physiological weakness of the smallest piglets at birth and during the suckling period (20 d) compared to their middle-weight littermates through their jejunal gene expression. At birth, light piglets showed a downregulation of genes related to immune response (FAXDC2, HSPB1, PPARGC1α), antioxidant enzymes (SOD2m), digestive enzymes (ANPEP, IDO1, SI), and nutrient transporter (SLC39A4) (P < 0.05) but also a tendency for a higher mRNA expression of GBP1 (inflammatory regulator) and HSD11β1 (stress hormone) genes compared to their heavier littermates (P < 0.10). Excluding HSD11β1 gene, all these intestinal gene expression differences initially observed at birth between light and middle-weight piglets were stabilized at the end of the suckling period, when others appeared. Genes involved in barrier function (CLDN1), pro-inflammatory response (CXCL2, IL6, IDO1), and stress hormone signaling (HSD11β1) over-expressed compared to their middle-weight littermates (P < 0.05). In conclusion, at birth and at the end of suckling period, light body weight piglets seem to have a compromised gene expression and therefore impaired nutrient absorption, immune and stress responses compared to their heavier littermates.

PQCT Analysis of Cortical Bone in Rats Exposed to High Levels of Cortisol in‐utero

Unperturbed fetal development is essential for future health of an individual. Previous studies have linked diseases of aging to harmful alterations that happen during fetal development. Given the significant long‐term impact that intrauterine environment has on an individual's life, it was hypothesized that maternal stress during pregnancy will have negative effects on the offspring's bone density and cross‐sectional area. To test this, twenty‐eight female and seven male Wistar rats (Rattus norvegicus) were purchased and bred to produce 176 offspring. During pregnancy, dams were randomly divided into four groups (n=7, per group) and immobilization stress induced as follows; Group 1 (GW1): immobilization stress on days 1–7 of pregnancy, Group 2 (GW2): on days 8–14, Group 3 (GW3): on days 15–21, Group 4 (Controls): left undisturbed. Maternal cortisol hormone, food intake, and weight gain were monitored during pregnancy. Pups were raised under normal laboratory conditions and sacrificed at ages: 4, 8, 12, and 16 weeks to determine the effect of prenatal stress. At necropsy, the femur was removed and preserved for image analysis.Differences among groups were determined by T‐test or analysis of variance (ANOVA). P values ≤ 0.05 were considered significant. Cortisol hormone levels in controls were lower than those of stressed animals. Stressed dams consumed 12.5% less food per day compared to controls. Animals in GW1 and GW2 gained less weight during pregnancy but had larger litters than did GW3 or the control group. Offspring born to GW3 were heavier compared to all other groups. The femurs were scanned using the XCT Research SA+ peripheral Quantitative Computed Tomography (pQCT). Preliminary analysis of cortical bone shows the GW1 males as having a significantly lower cortical thickness compared to the controls at the age of 8, 12 and 16 weeks. The GW1 males also had a significantly lower periosteal perimeter and endosteal perimeter compared to controls at the age of 8 weeks. There was no significant difference in cortical thickness, periosteal perimeter and endosteal perimeter of females. This preliminary analysis shows that bone development in males was significantly impacted when fetuses in this study were exposed to high levels of cortisol in‐utero during the first week of gestation. Analysis of the remaining data is ongoing.

Offspring of hyper prolific sows: Immunity, birthweight, and heterogeneous litters.

In Europe, in the last 3 decades, there has been a constant increase in litter size due to the use of superior maternal line genetics. Those sows giving birth to more piglets than their average number of functional teats are identified as hyperprolificsows(HPS). The large number of piglets born within a litter implies not only a challenge for their access to vital resources like colostrum and milk but has a direct effect on their average birth weight and heterogeneity. These conditions are detrimental to piglets' vitality in the first hours of life and also to their immunity development. An exceptionally large number of growing fetuses in HPS leads to intrauterine crowding and consequently to an increased number of piglets suffering from intrauterine growth retardation (IUGR), which put piglets at a high risk of mortality after birth and up to later stages of life. Increased heterogeneity of birth weight within large litters increases the competition for colostrum intake, with the smaller piglets being less competitive and vital, and therefore affecting negatively their immunity. Low birth weight, long interval to reach the udder, and long duration of farrowing, all have negative effects on piglets' immunoglobulin absorption. In HPS litters, colostrum management should be focused on low birth weight piglets, anticipating their impaired capabilities associated with ingesting adequate colostrum, by shortening the time to reach the udder and reducing competition among piglets. The vitality of neonate piglets, especially low in birth weight or affected by IUGR should be enhanced to improve their body temperature and their early life stage energy metabolism.

Disentangling Litter Size and Farrowing Duration Effects on Piglet Stillbirth, Acid-Base Blood Parameters and Pre-Weaning Mortality.

The current study evaluated interactions between farrowing duration and litter size on the level of asphyxia, vitality, percentage of stillbirth, and pre-weaning mortality of piglets. Farrowing duration was measured in 159 crossbred gilts and sows (Yorkshire × Dutch Landrace). Litter size ranged between 12 and 21 piglets. Blood acid–base parameters in umbilical cord blood and vitality scores of piglets were determined immediately after birth. Number of piglets born alive and stillborn as well as individual piglet weights at birth were recorded. Pre-weaning mortality (excluding stillbirth) was determined throughout lactation. Litter size as well as farrowing duration were categorized to evaluate the interaction between the two. There tended to be an interaction between litter size and farrowing duration for pre-weaning mortality (p = 0.10). In small litters (12–15 piglets), a prolonged farrowing duration (>250 min) tended to increase pre-weaning mortality compared with a short (<150 min) and medium farrowing duration (150–250 min), while for large litters (19–21 piglets), a medium to long farrowing duration tended to decrease pre-weaning mortality. No other interactions between litter size and farrowing duration were found. Piglets within large litters showed a higher umbilical cord lactate level (p < 0.01), lower average vitality score (p = 0.01), and a higher stillborn percentage (p < 0.01) compared with piglets within medium size (16–18 piglets) and small litters. Each additional piglet born to a litter linearly decreased average piglet birth weight (17.6 g, p < 0.01), increased farrowing duration (11 min, p < 0.01), and increased stillbirth (0.5%, p = 0.04). A medium farrowing duration resulted in a lower stillborn percentage compared with a short or prolonged farrowing duration, suggesting that farrowing duration might have an optimum. When analyzed linearly, stillborn percentage increased with 1.85% per every 100 min (p < 0.01) of farrowing duration. It can be concluded that both litter size and farrowing duration affect stillborn percentage, but independent from each other. However, these two factors tended to interact regarding pre-weaning mortality, suggesting that setting a certain threshold for maximal farrowing duration should be taken with care, because this appears to depend on litter size.

New traits to improve the maternal ability of sows under production conditions

The aim was to evaluate new traits for better expression of maternal ability in sows and the feasibility of their inclusion as a selection criterion in breeding programs. We used maternity performance records of 4627 Landrace and Large White litters to estimate genetic parameters through the Bayesian approach. Cross-fostering was performed only after piglet individual identification and the high cross-fostering rates were in accordance with the reality of production systems in the country. The group of new traits was made up of measures of average daily weight gain from birth to weaning of fostered and biological litter; average weaning weight of fostered and biological litter; total weight from birth to weaning of fostered and biological litter; and weaning potential of piglets, as the percentage of piglets weaned from the total piglets received at the beginning of the lactation period. The estimated heritabilities for new traits were low (0.02 to 0.06) and consistent with the complexity of the traits indicating maternal ability. The high variation between the correlations verified in this data set warns about the impact of management, mainly from cross-fostering, in the estimates of genetic parameters of complex maternal ability traits. Because of these interactions, there does not seem to be a single, common definition of a maternal ability trait. New litter performance traits attributed to sows, such as average weight gain of litter and average weaning weight, are liable to insertion in breeding programs despite the slow genetic gain and may be the key to improving the sow's maternal ability and potential, reflecting on the quality of the weaned piglet and weight of weaned piglets per sow per year. However, these traits do not replace current litter size traits that must be maintained to mitigate possible negative associations between traits.

DETERMINATION OF NATURAL FREQUENCIES AND FORMS OF FREE VIBRATIONS OF THE GRATE OF THE RAW COTTON CLEANER

The article discusses the operation of the grate proposed by the authors with grates made of composite material, with a polyamide matrix and a filler of basalt fibre. Experimental grates are mounted on elastic rubber supports with non-linear rigidity. On the basis of finite element modelling, the analysis of the forms and natural frequencies of free oscillations of the grate of cotton cleaner from large litter was carried out. It is shown that the first 12 natural frequencies are located in a narrow range from 2.579 to 2.692 Hz. This is due to the design features of the grate. It is shown that during operation the grate performs forced oscillations with frequencies 45…75 Hz.

PSIV-15 Impact of Wean Age and SID Lysine Level on Performance in Lactation

Abstract With genetic improvement, sows are having larger litters and nursing more pigs. The wean age of these piglets can impact sow feed intake and piglet wean weight. Additionally, Lys level can impact sow and piglet growth. This study was performed to assess whether the addition of greater standardized ileal digestible (SID) Lys improves sow and litter performance for 2 wean ages. Four hundred thirty-two DNA F1 females (average parity 2.4) were randomly allotted within group and entry weight at farrowing to 1 of 4 dietary treatments. Treatments were arranged in a 2 x 4 factorial with wean age (15.5 and 24.5 d) and lactation diet SID Lys (0.87, 0.94, 1.02 and 1.10%). Sows were weighed entering and exiting the farrowing room. Feed disappearance was calculated as the total amount of feed provided to the sow during lactation. A post-farrow weight model was utilized to assess true weight loss in lactation. Litters were standardized within 24 h of birth. Data were analyzed as a randomized complete block design with fixed effects of SID Lys and wean age, and random effect of replicate. Average daily feed intake was increased (P &amp;lt; 0.05) in the sows weaning older age compared with younger age piglets (6.52 vs. 5.87 kg respectively). There was a tendency (P &amp;lt; 0.10) for an interaction between wean age and maternal Lys level on piglet wean weight as higher Lys increased wean weight (0.29 kg) in the older wean age but had no improvement in the younger wean age. Sow weight loss was decreased (P &amp;lt; 0.05) in sows weaning younger piglets compared with sows weaning older piglets (4.26 vs. 11.02 kg weight loss, respectively). These data show that greater levels of SID Lys to target 65 g/d in lactation can improve wean weight for later weaning sows.

174 Effects of Nursing a Large Litter and Ovarian Response to Gonadotropins at Weaning on Subsequent Fertility in First Parity Sows

Abstract Post-weaning fertility failures occur more often in parity 1 (P1) sows due to increased metabolic demands for lactation and inability to meet energy requirements for maintenance, growth, and reproduction. We hypothesized that body condition loss occurs more frequently in P1 sows nursing a large litter, resulting in impairment of ovarian follicle development during lactation and post-weaning. At 24 h post-farrowing, P1 sows (n = 123) were assigned to treatment (TRT) based on body weight and the number of functional teats to receive High Number (HN, 15 to 16) or Low Number (LN, 12) of nursing pigs. At weaning, sows in each TRT were assigned to receive PG600 or None (Control). During lactation, sow body measures were obtained and ovarian follicles were assessed in mid-lactation and post-weaning. Lactation data were analyzed for the effects of TRT, and fertility data after weaning were assessed for TRT x PG600. There were no interactions of TRT x PG600. During lactation, 22.2% of HN sows lost ≥4 pigs and were removed from analysis. The HN sows lost more (P &amp;lt; 0.05) body weight (-6.2 kg), backfat (-1.0 mm), body condition score (-0.4), and nursing piglets (-0.4) than LN sows. However, HN sows weaned more pigs (14.0) than LN sows (11.0). There was no effect of TRT on wean to estrus interval (4.2 d), but was 0.5 d shorter for PG600 (P = 0.004). There were no effects of TRT or PG600 on estrus within 6 d after weaning (85.6%), but PG600 induced smaller (P = 0.002) follicles at estrus (6.7 mm) than Control (7.3 mm). In the subsequent parity, there were no effects of TRT or PG600 on farrowing rate (93.9%) and total born (13.2). Overall, HN sows lost more piglets and body condition, although they weaned more pigs, but had no effects on reproductive performance.

Effects of Age at First Joining and Ewe Genotype on the Performance of Two-Tooth Ewes and That of Their Progeny to Slaughter.

Simple SummaryEwe replacements are a major cost in prime-lamb production. Many producers do not join replacements at 7 months as they believe that it has a negative effect on two-tooth performance. The effect of age at first joining on the reproductive performance of two-tooth ewes, representing three genotypes, was evaluated as well as the performance of their progeny. Whilst joining at 7 months reduced ewe body weight when joined at 19 months and immediately post joining, body weight at the subsequent lambing was increased, and ewe productivity and progeny performance were unaffected. Ewe genotype significantly influenced litter size and the number of lambs reared per ewe joined but had no effect on progeny performance. The probability of rearing at least one lamb (PR1L) is an indicator of overall efficiency. In the current study, whilst there was no relationship between ewe body weight when joined at 19 months and PR1L, there was a positive relationship between body weight at 7 months and PR1L at 2 years. It is concluded that joining replacements at 7 months does not have a negative impact on the performance of two-tooth ewes. The effects of first-joining age (7 or 19 months) and genotype on ewe performance when joined to lamb at 2 years, and the performance of their progeny, were evaluated using 424 ewes, representing 3 genotypes: Belclare (Bel), Suffolk × Belclare (Suf × Bel) and Suffolk-type (≥75% Suffolk ancestry (Suf75)). Ewes were managed in a grass-based system. Ewes first joined at 7 months were lighter (p < 0.01) at 19 months and immediately post lambing; otherwise, age at first joining had no effects (p > 0.05) on ewes or their progeny and there were no important interactions with genotype. Bel and Suf × Bel had larger litters (p < 0.001) and reared more lambs per ewe joined (p < 0.01) than Suf75. Ewe genotype had no effect (p > 0.05) on proportion failing to lamb, incidence of lambing assistance, lamb mortality, ewe survival to 31 months, or progeny performance. Increasing the body weight of ewes at 7 months of age increased the probability (p < 0.02) of rearing 1 or more lambs at 2 years and there was no interaction with genotype. It is concluded that age at first joining had no negative impact on the performance of ewes or their progeny.

Hygienic behavior of bees as an element of sterility in the production of environmentally friendly products

Beekeeping in Russia has been widespread for a long time and almost everywhere, a traditional and significant branch of the country’s agriculture. In the Russian Federation, as in most countries, beekeeping is mainly practiced by amateurs. In 2019, according to government statistics, there were about 4.0 million bee colonies in the country, with more than 90% of them in the private sector. One of the factors of high productivity of bee colonies is the hygienic activity of individuals. The behavior of the bees in maintaining cleanliness and hygiene in the hive is astonishing. Not only the honeycomb, but even the walls and floor of the hive are always kept neat, polished with propolis. Garbage falling to the bottom of the hive is immediately thrown out through the entrance. Moreover, large litter, for example, the corpse of a bee, is pulled out by the orderlies onto the boarding board, and, grabbing it with their legs, take off to carry it away from the hive. Worker bees sweep small debris out of the hive with their fan wings, like brooms, and even brush dust particles to the tap hole. Sterility in a honey bee nest can be compared to an operating room in a modern clinical hospital.

A case of mastitis in an allomother mongrel bitch nursing a jaguar cub

Allonursing is typical in mammals, especially in the polytocous taxa with large litters. One of the immediate benefits of allonursing is milk evacuation of distended mammary glands, especially in females who lost their offspring, predisposing them to mastitis. Mastitis represents the inflammation of the mammary gland and in carnivores it can affect a section of the gland or the entire mammary tissue (13). Therefore, it is considered an emergency (2, 15) since if left untreated mastitis can suffer local and systemic complications like mammary gangrene, septicemia, or neonatal mortality. This case report presents a mastitis episode in an allomothering mongrel bitch after starting to allonurse a one-day-old jaguar cub and her single puppy. Laboratory assays showed the presence of mild leukocytosis, folded milk C-reactive protein (CRP; 5.1 μg/mL) levels, an alkaline milk pH reaction (pH &gt; 7), increased cell counts, phagocytosis, and presence of Staphylococcus aureus and Enterococcus faecalis in the cultured milk samples.

Genetically engineered pig models of neurological diseases

Genetically modified animal models are commonly used for in vivo studies of human diseases. Mice are the most common animal models used in biomedical research, which have provided important insights into disease pathogenesis and are widely used to find treatments for diseases. However, due to the differences in the anatomical structure and physiological function between human and mouse brains, most genetically modified mouse models cannot fully recapitulate the overt and selective neuronal loss seen in age-dependent neurodegeneration diseases. While non-human primates (NHP) are closer to humans and have been used to model human disease, these models are difficult to be utilized at a large scale due to various limitations including their high costs, prolonged breeding time, community concerns for use of NHP, and high ethical standards. As an important animal resource in agriculture, pigs are also used as animal models in biomedical research. The central nervous system of pigs is highly similar to that of humans, making pig models suitable for investigating neurological diseases. The relatively short breeding period, large litter size, and established somatic cell transfer technology are advantages over NHP for using pigs to model human diseases. The recent development of gene editing tools allows one to more efficiently generate pig models that can precisely mimic genetic mutations in neurological diseases. In this review, we summarize recent advances in the use of pigs for modeling human neurological diseases, including new approaches for generating genetically modified pig models.

Pre- and Postnatal Predator Cues Shape Offspring Anti-predatory Behavior Similarly in the Bank Vole

Prey animals can assess the risks predators present in different ways. For example, direct cues produced by predators can be used, but also signals produced by prey conspecifics that have engaged in non-lethal predator-prey interactions. These non-lethal interactions can thereby affect the physiology, behavior, and survival of prey individuals, and may affect offspring performance through maternal effects. We investigated how timing of exposure to predation-related cues during early development affects offspring behavior after weaning. Females in the laboratory were exposed during pregnancy or lactation to one of three odor treatments: (1) predator odor (PO) originating from their most common predator, the least weasel, (2) odor produced by predator-exposed conspecifics, which we call conspecific alarm cue (CAC), or (3) control odor (C). We monitored postnatal pup growth, and we quantified foraging and exploratory behaviors of 4-week-old pups following exposure of their mothers to each of the three odour treatments. Exposure to odors associated with predation risk during development affected the offspring behavior, but the timing of exposure, i.e., pre- vs. postnatally, had only a weak effect. The two non-control odors led to different behavioral changes: an attraction to CAC and an avoidance of PO. Additionally, pup growth was affected by an interaction between litter size and maternal treatment, again regardless of timing. Pups from the CAC maternal treatment grew faster in larger litters; pups from the PO maternal treatment tended to grow faster in smaller litters. Thus, in rodents, offspring growth and behavior are seemingly influenced differently by the type of predation risk perceived by their mothers.

Physical and mathematical modeling of cleaning fibrous material from coarse-grained litter

The article provides a recommended scheme and principle of operation of the cleaner of fibrous material from large litter. The results of theoretical studies to determine the laws of motion and the recommended parameters of the working bodies of the cleaning machine are presented. The results of comparative production tests of a fibrous material cleaner from large litter are given. Substantiated the receipt of parameters and modes of operation of the working bodies of the cleaner of fibrous material, in particular cotton.

The effect of the SCD genotype on litter size and weight at weaning

Genetic markers associated with meat quality may have adverse effects on reproduction performance, as shown for a variant in the leptin receptor (LEPR) gene. There is a single nucleotide polymorphism (SNP) in the stearoyl-CoA desaturase (SCD) gene that influences the monounsaturated fatty acid content of pork. Here, we investigate single and combined effects of the SCD (rs80912566 T>C) and LEPR (rs709596309 C>T) SNP on litter size and weaning weight. A total of 1,246 sows of known genotype for SCD (732 of which were also genotyped for LEPR) were monitored for age at farrowing, number of piglets born, born alive and weaned, and litter weight at weaning during two years. The effects of these SNP and of a variant in the diacylglycerol O-acyltransferase 2 (DGAT2) gene on milk fat content and fatty acid composition were also analysed in 99 primiparous sows. No adverse effects of the SCD SNP on overall reproductive performance were observed. However, in primiparous sows, we found that the SCD-T allele, the one that increases the monounsaturated fatty acid content, influenced negatively the weight of piglets at weaning (the piglets from SCD-TT sows weighted 126 g less at weaning than those from SCD-CT sows), especially in combination with the LEPR-TT genotype (the piglets from SCD-TT/LEPR-TT sows weighted 277 g less at weaning than piglets from SCD-C−/LEPR-C− sows). In contrast to SCD, the negative effect of the LEPR-TT sows on the piglets weaning weight was maintained in all parities (piglets from LEPR-TT sows were on average 126 g lighter than LEPR-C− sows). The unfavourable effect of the SCD-T allele on the litter weight of primiparous sows could be due to lower body reserves at first farrowing (SCD-TT pigs had 0.62 mm less backfat thickness at 205 d than SCD-CT pigs) together with larger litters at birth (the SCD-TT sows had 0.32 more piglets born alive per litter than the SCD-CT sows). The milk of primiparous sows with the SCD-T allele showed higher desaturation indices (i.e. higher monounsaturated to saturated fatty acid ratios), but lower fat content. No relevant effects of the DGAT2 SNP on milk traits were found. In conclusion, the SCD SNP does not impact overall reproductive performance in pigs, but cautious management of SCD-TT gilts is recommended.

483 Current Knowledge Gaps in Swine Reproduction

Abstract Identifying swine reproduction research opportunities, especially those that add value by addressing industry challenges and leveraging assisted reproductive technologies (ART) will be the focus of this talk. ART and genetic selection to increase pork production efficiency have been intertwined since the use of artificial insemination (AI) became widely adopted 30 years ago. Tremendous efficiency gains have been made in part by increasing litter size which is nearly 6 to 7 pigs larger today than it was in 1990. The increased farrowing duration and stillbirths, and decreased piglet birth weight, colostrum intake, and survival to weaning that has been associated with these larger litters are prime targets to be ameliorated with sow and pig management solutions. There is also clear evidence that pigs from smaller litters have the advantage of superior reproductive performance compared to those from larger litters. Thus, litter size and pre-weaning growth may need to be managed, or at least taken into account, to select the best boars and gilts for breeding stock and replacements. Any other accurate, early indicators of boar and gilt puberty, fertility, and lifetime productivity could add significant value. The seasonal fluctuation in fertility that has plagued pig production is costly and may be smoothed out by strategies that mitigate heat stress and improve health. Another opportunity to improve both pig and sow welfare may be intermittent suckling and induction of a fertile estrus and ovulation for breeding during lactation. Even more genetic and pig growth value could be added via AI with sex-sorted semen, if methods to better estimate boar fertility, deliver increased sperm quality, and more precisely synchronize or predict ovulation can be found to reduce the number of sperm required per female. Existing and evolving ART will synergize with genomics and gene editing technologies to unlock new levels of production efficiency.

Sexual dimorphism in size and shape of the head in the sea snake Emydocephalus annulatus (Hydrophiinae, Elapidae)

In snakes, divergence in head size between the sexes has been interpreted as an adaptation to intersexual niche divergence. By overcoming gape-limitation, a larger head enables snakes of one sex to ingest larger prey items. Under this hypothesis, we do not expect a species that consumes only tiny prey items to exhibit sex differences in relative head size, or to show empirical links between relative head size and fitness-relevant traits such as growth and fecundity. Our field studies on the sea snake Emydocephalus annulatus falsify these predictions. Although these snakes feed exclusively on fish eggs, the heads of female snakes are longer and wider than those of males at the same body length. Individuals with wider heads grew more rapidly, reproduced more often, and produced larger litters. Thus, head shape can affect fitness and can diverge between the sexes even without gape-limitation. Head size and shape may facilitate other aspects of feeding (such as the ability to scrape eggs off coral) and locomotion (hydrodynamics); and a smaller head may advantage the sex that is more mobile, and that obtains its prey in narrow crevices rather than in more exposed situations (i.e., males).