Reproduction in Farm Animals in an Era of Rapid Genetic Change: Will Genetic Change Outpace Our Knowledge of Physiology?

One Health challenges for pig reproduction

The current state of the world challenges pig reproduction as an important part of One Health, which involves interrelationships between animal, human and environmental health. The One Health concept underlines a comparative aspect in reproductive physiology and disease occurrence, bridging knowledge from one species to another. Seasonal changes in the environment affect pig reproduction and climate change may further strengthen those effects. Endocrine-disrupting chemicals (EDCs), and specifically phthalates and heavy metals, interfere with endocrine function, and thereby sexual behavior, fertilization capacity and steroidogenesis. Reproductive infections and extended semen storage are important indications for antimicrobial use. Innovative solutions are needed to explore alternatives to antimicrobials. Efforts to ensure reproductive efficiency have prolonged farrowing as litter size has doubled over the past three decades, compromising immune transfer and welfare. Physiological, metabolic and programming related events around parturition are key areas for future One Health research in pig reproduction. In conclusion, climate change challenges reproductive management and breeding. More resilient pigs that can tolerate harsh environment but maintain high reproductive performance are needed. EDCs continue to grow as an environmental challenge for reproductive management and alternatives to antibiotics will be required.

Suckling Induces Differential Gut Enzyme Activity and Body Composition Compared to Feeding Milk Replacer in Piglets

The aim of this study was to investigate differences in growth, hematology, metabolism, small intestine (SI) morphology, and enzyme activity of sow-reared piglets (SOW) compared to artificially reared piglets (MILK) given milk replacers in two different environments. Thirty-six piglets were selected at birth based on their birth weight; eighteen were kept on a commercial farm, another eighteen transferred to an animal research facility for artificial rearing. Differences were observed in enzymatic activity, with a larger amount of sucrase in the SOW compared with MILK group across the SI. SOW piglets also had a body composition with a larger amount of fat, muscle, and bone mass content. Differences in hematology were observed, suggesting environmental influences, biochemistry differences reflective of the diets given, and finally, an increased dry matter (DM) intake in SOW piglets was estimated. No differences were observed in immune function and only small differences in the gut integrity were found between the two groups. It can be concluded that body composition and enzyme activity can be manipulated through dietary intervention and that an increase in DM during lactation is beneficial for gut function. The study warrants further investigation into what this means for the subsequent weaning period.

Associations among individual gilt birth weight, litter birth weight phenotype, and the efficiency of replacement gilt production

Selection for larger litter size has increased the number of low individual birth weight (BWi) pigs and produced sows with a repeatable low average litter birth weight phenotype (BWP). Using an average of 3.6 litters records per sow, BWP was established in 644 nucleus-multiplication sows producing replacement gilts in a large commercial operation and classified as low (L-BWP, <1.18 kg, n = 85), medium (M-BWP, ≥1.18 to ≤1.35 kg, n = 250), or high (H-BWP, >1.35 kg, n = 309) on the basis of a BWi of 1.18 kg below which there was a high risk of early mortality and the average BWi (1.35 kg) for the population. In subsequent litters, potential replacement gilts born to these sows (n = 7,341) received a unique identification tag that allowed the impact of BWi, BWP, and their interactions on the efficiency of replacement gilt production to be evaluated. Negative effects of BWi on mortality until day 4 after birth were confirmed (P < 0.05) and cumulative losses to weaning, to day 70 of age, and to final pre-selection at 165 d of age were affected (P ≤ 0.05) by the interaction between BWP and BWi. Among the 2,035 gilts for which records for selection efficiency and production to fourth parity were available, a lower BWi decreased the probability of gilts reaching pubertal estrus (P < 0.05) after 21 and 28 d of boar stimulation starting at 180 d of age, with no effect of BWP. Overall, neither BWi, BWP, nor their interaction affected age at puberty. After breeding, only the main effect of BWP affected productivity and retention in the sow herd. In parities 1 and 2, percent stillborn was higher in litters born to gilts from H-BWP compared with L-BWP dams (P < 0.05), and in parity 2, total born and born alive were lower in sows derived from H-BWP compared with other BWPs. There were no differences in retention based on BWP classes until parity 2, after which retention tended (P ≤ 0.09) to be lower in sows derived from H-BWP compared with L-BWP dams. These results provide evidence that sow BWP is an important factor in the overall efficiency of replacement gilt management. This study also confirms that effective gilt selection and pre-breeding management protocols support excellent sow lifetime productivity and mitigate the risk of a high BWP in the litter of origin affecting retention in the breeding herd.

Effects of early commercial milk supplement on the mucosal morphology, bacterial community and bacterial metabolites in jejunum of the pre- and post-weaning piglets

Objective

Sow milk (SM) may not be able to meet the piglet’s nutritional needs in late lactation. Hence, this study was conducted to investigate the effects of early commercial milk (CM) supplement on the mucosal morphology, bacterial community and bacterial metabolites in jejunum of piglets.

Methods

Ten litters of newborn piglets ([Yorkshire×Landrace]×Duroc) were randomly divided into 2 groups of 5 litters. The piglets in the control group were suckled by the sow (SM), while the piglets in the treatment group (CM supplement) were supplemented with a CM supplement along with suckling from d 4 to d 28 of age.

Results

No significant differences were observed about jejunal mucosal morphology on d 28 and d 35 between two groups. On d 28, the activity of lactase in the jejunum was significantly decreased in the CM group, while the activity of sucrase and the ratio of maltase to lactase were significantly increased (p<0.05). On d 35, the activity of maltase in the jejunum was significantly increased in the CM group (p<0.05), and maltase to lactase ratio tended to increase in the CM group (p = 0.065). In addition, piglets in the CM group had a higher abundance of Clostridium XI, Tuicibater, and Moraxella in the jejunum on d 28, while the abundance of Lactobacillus was significantly increased on d 35 (p<0.05).

Conclusion

The early CM supplement improved the maturation of the jejunum to some extent by enhancing the maltase and sucrase activities. Moreover, the early CM supplement could help maintain the homeostasis of internal environment in jejunum by increasing the microbial-derived metabolites.

Effect of suckling intensity of primiparous sows on production performance during current and subsequent parities1

This study was conducted to evaluate the effects of suckling intensity (litter size and lactation length) to primiparious sows on production performance during current and subsequent parities. Upon farrowing, 115 primiparous sows (farrowing weight: 222.7 ± 20.0 kg) were initially allotted to 4 treatments in a 2 × 2 factorial arrangement with 2 litter sizes: 10 and 13 piglets (LS10 vs. LS13), and 2 lactation lengths: 21 and 27 d (LL21 vs. LL27). Upon weaning, sows were rebred and those farrowed successfully (n = 66) kept 10 piglets and weaned at 21 d in the second parity. Sows were fed ad libitum during lactation in both parities. Feed intake, BW loss, backfat loss, litter size, and litter weight gain during lactation in both parities were determined. Litter weight gain in LS13 was greater (P < 0.05) than that in LS10 (54.4 vs. 47.7 kg) during the first lactation. Sows in LS13 had a greater (P < 0.05) BW loss than sows in LS10 (24.1 vs. 17.4 kg). Body weight loss was not different between LL27 and LL21. Sows in LS13 tended to have a greater (P = 0.075) removal rate than those in LS10 (47.5 vs. 32.2%). Sows in LL27 had a smaller (P < 0.05) removal rate than those in LL21 (28.0 vs. 51.7%). In the second parity, gestation BW gain in LL27 tended to be greater (P = 0.098) than that in LL21 when the previous litter size was 10 piglets (56.1 vs. 33.2 kg). Litter performance and feed intake of sows were not affected by previous litter size, lactation length, and their interaction. The farrowing weight, farrowing body protein and lipid, body weight loss was not different between LS13 and LS10, whereas backfat loss in LS13 was smaller (P < 0.05) than that in LS10 during the second lactation (0.9 vs. 2.4 mm). The predicted body lipid loss in LS13 was also smaller than that in LS10 (2.3 vs. 5.3 kg) during the second lactation. Sows in LL27 had a smaller (P < 0.05) BW loss and body lipid loss during the second lactation than sows in LL21 (4.0 vs. 9.0 kg; 2.3 vs. 4.8 kg). The concentration of milk fat in LL27 was smaller (P < 0.05) than that in LL21 (7.9 vs. 9.1%). In conclusion, increasing suckling intensity to primiparous sows increased litter weight gain but increasing litter size reduced piglet ADG. Sow performance in the second lactation was not negatively affected by increasing suckling intensity of the first lactation. Interestingly, sows with an increased suckling intensity in the first lactation had reduced loss of body reserves in the second lactation.

Review: Maternal programming of development in the pig and the lactocrine hypothesis

Maternal effects on development are profound. Together, genetic and epigenetic maternal effects define the developmental trajectory of progeny and, ultimately, offspring phenotype. Maternally provisioned environmental conditions and signals affect conceptus, fetoplacental and postnatal development from the time of conception until weaning. In the pig, reproductive tract development is completed postnatally. Porcine uterine growth and uterine endometrial development occur in an ovary-independent manner between birth (postnatal day = PND 0) and PND 60. Milk-borne bioactive factors (MbFs), exemplified by relaxin, communicated from lactating dam to nursing offspring via a lactocrine mechanism, represent an important source of extraovarian uterotrophic support in the neonatal pig. Lactocrine deficiency from birth affects both the neonatal porcine uterine developmental program and trajectory of uterine development, with lasting consequences for endometrial function and uterine capacity in adult female pigs. The potential lactocrine signaling window extends from birth until the time of weaning. However, it is likely that the maternal lactocrine programming window - that period when MbFs communicated to nursing offspring have the greatest potential to affect critical organizational events in the neonate - encompasses a comparatively short period of time within 48 h of birth. Lactocrine deficiency from birth was associated with altered patterns of endometrial gene expression in neonatally lactocrine-deficient adult gilts during a critical period for conceptus-endometrial interaction on pregnancy day 13, and with reduced litter size, estimated at 1.4 pigs per litter, with no effect of parity. Data were interpreted to indicate that reproductive performance of female pigs that do not receive sufficient colostrum from birth is permanently impaired. Observations to date suggest that lactocrine-dependent maternal effects program postnatal development of the porcine uterus, endometrial functionality and uterine capacity. In this context, reproductive management strategies and husbandry guidelines should be refined to ensure that such practices promote environmental conditions that will optimize uterine capacity and fecundity. This will entail careful consideration of factors affecting lactation, the quality and abundance of colostrum/milk, and practices that will afford neonatal pigs with the opportunity to nurse and consume adequate amounts of colostrum.

Birth weight threshold for identifying piglets at risk for preweaning mortality

Several studies have suggested there is a critical relationship between piglet birth weight and preweaning mortality. Thus, the objective of the current work was to identify a birth weight threshold value for preweaning mortality. Birth weight and survival data from two studies involving a combined total of 4,068 piglets from 394 litters on four commercial farms (three European, one U.S.) were compiled for a pooled, multistudy analysis. Overall preweaning mortality across the two studies was 12.2%. Key variables used in the analysis were piglet birth weight (measured within 24 h of birth) and corresponding survival outcome (dead or live) by weaning at 3-4 wk of age. A mixed effects logistic regression model was fit to estimate the relationship between preweaning mortality and birth weight. A random effect of study was included to account for overall differences in mortality between the two studies. A piecewise linear predictor was selected to best represent the drastic decrease in preweaning mortality found as birth weight increased in the range of 0.5-1.0 kg and the less extreme change in weight above 1.0 kg. The change point of the birth weight and preweaning mortality model was determined by comparing model fit based on maximizing the likelihood over the interval ranging from 0.5 to 2.3 kg birth weight. Results from the analysis showed a curvilinear relationship between birth weight and preweaning mortality where the birth weight change point value or threshold value was 1.11 kg. In the combined data set, 15.2% of pigs had birth weights ≤1.11 kg. This subpopulation of pigs had a 34.4% preweaning mortality rate and represented 43% of total preweaning mortalities. These findings imply interventions targeted at reducing the incidence of piglets with birth weights ≤1.11 kg have potential to improve piglet survivability. Additional research is needed to validate 1.11 kg as the birth weight threshold for increased risk of preweaning mortality.

Impact of feed intake during late gestation on piglet birth weight and reproductive performance: a dose-response study performed in gilts

The effects of increasing feed intake (1.8, 2.3, 2.8, and 3.3 kg/d) during late gestation of gilts on piglet birth weight and female reproductive performance were evaluated. A total of 977 gilts were fed a diet based on corn-soybean meal (3.29 Mcal ME per kg and 0.64% standardized ileal digestible lysine) from day 90 of gestation until farrowing. Gilts were weighed on days 90 and 112 of gestation, at farrowing and weaning. Born alive and stillborn piglets were weighed within 12 h of birth. Colostrum yield (CY), lactation feed intake, and litter growth rate were measured in a randomly selected subsample of 245 gilts. The data were analyzed using generalized linear mixed models. As expected, gains in body weight (BW) were different at day 112 (P < 0.001) with the greatest values observed in the 3.3 kg/d treatment. As feed intake increased during late gestation, BW, body condition score (BCS), backfat (BF), and Caliper unit also increased between day 112 and weaning (P < 0.001). No differences were found among treatments in total number of piglets born, mummified fetuses, sum of born alive and stillborn piglets, and within-litter birth weight CV (P > 0.05). Tendencies for quadratic effect of feed intake were observed for born alive piglets (P = 0.079), average birth weight of piglets (P = 0.083), and litter weight (P = 0.059). Gilts with lower feed intake during late gestation had reduced percentages of stillborn piglets than gilts with greater feed intakes. The CY decreased linearly (P < 0.05) as the feed intake was increased. No differences among treatments were found at weaning in individual piglet weight and litter weight, as well as in percentage of weaned piglets (P > 0.05). Lactation feed intake decreased as gestation feeding level increased (P < 0.05). No differences in the subsequent cycle were observed among treatments for farrowing rate, retention rate up to the next farrowing, number of total piglets born, born alive, stillborn piglets, and mummified fetuses (P > 0.05). In conclusion, increased feed intake from day 90 of gestation until farrowing resulted in increased maternal BW gain and stillborn rate, but reduced CY and lactation feed intake. A slight increase in birth weight was observed for the 2.3 kg/d treatment. Furthermore, litter growth and subsequent female reproductive performance were not affected by feed intake during late gestation.

Two different feeding levels during late gestation in gilts and sows under commercial conditions: impact on piglet birth weight and female reproductive performance

The increase in the litter size in past decades has caused reduction in the individual piglet birth weight. Therefore, nutritional strategies employed in the last third of gestation in order to improve the piglet birth weight have been studied. This study aimed to evaluate the effects of 2 different feeding levels (1.8 and 2.2 kg/d) in the last third of gestation on the piglet birth weight and the female reproductive performance. A total of 407 females were fed on a diet based on corn-soybean meal (3.25 Mcal ME per kg and 0.65% standardized ileal digestible lysine) from day 90 of gestation until farrowing. The females were weighed on day 90 and day 112 of gestation, and at weaning. Born alive and stillborn piglets were weighed within 12 h of birth. The lactation feed intake and the litter growth rate were measured in a randomly selected subsample of 53 sows from each treatment. The data were analyzed using the generalized linear mixed models, considering the females as the experimental unit. Parity, treatment, and their interaction were analyzed for all responses. The females fed on 2.2 kg/d of diet from day 90 to day 112 exhibited greater body weight gain compared to the females fed on 1.8 kg/d (P < 0.001). No evidence of the effects of feeding levels on the individual piglet birth weight and on the within-litter CV were observed, for both gilts and sows (P ≥ 0.90). Similarly, when the classes of the total born piglets were considered in the analysis (<15 and ≥15 for gilts; <16 and ≥16 for sows), no positive effects of increasing the feeding level were observed on the individual piglet birth weight and the within-litter CV (P ≥ 0.47). Also, no differences in the stillborn rate, mummified-fetus rate, and percentage of piglets weighing less than 1,000 g at birth were observed between the treatments (P ≥ 0.28). The females fed on 1.8 kg/d of diet exhibited greater feed intake during lactation, compared to the females fed on 2.2 kg/d (P < 0.05). Weaning weight, weaning-to-estrus interval, subsequent litter size, and culling rate were not affected by the dietary levels (P ≥ 0.23). In conclusion, increasing the feed intake from day 90 of gestation until farrowing increased the body weight gain in sow, demonstrated no effect on the piglet birth weight, and reduced the lactation feed intake. Furthermore, there was no evidence of the effects of the treatments on the litter growth rate or on the subsequent female reproductive performance.

Estimation of the effects of selection on French Large White reproductive performance using frozen semen

Genetic trends for male and female sexual development and components of litter size and weight at birth (LB) as well as traits related to sow lifetime productivity were estimated in a French Large White (LW) pig population using frozen semen. Two experimental groups (EXP = L77 and L98) were produced by inseminating LW sows with either stored frozen semen from 17 LW boars born in 1977 (EXP = L77) or with semen from 23 LW boars born in 1998 (EXP = L98). In each group, about 100 males were measured for testicular development and bulbo-urethral gland development, and 90 gilts were checked for puberty, among which about 50 gilts were measured for their first ovulation rate at puberty (ORP). The females were then mated to 15 randomly chosen males for each group for 6 successive parities and measured for total number born (TNB), number born alive (NBA), litter weight at birth (LWB), and interval from weaning to first estrus as well as ovulation rate at fertilization (ORF = ovulation rate of gestating sows) on a subset of litters. The data were analyzed using mixed linear models including the fixed effects of EXP, of finishing (sexual development traits) or farrowing group, and parity (LB traits); the random effects of birth litter (sexual development traits) or sow (LB traits); and, when relevant, age or BW as covariates. The homogeneity of residual variances across EXP was also tested. For each trait, the genetic trend was estimated as twice the difference between L98 and L77. Limited differences were observed for sexual development traits, except for ORF, which increased by 0.17 ± 0.06/yr. The residual SD of NBA (2.7 vs. 2.0; = 0.004) and LWB (3.1 vs. 2.5; = 0.03) were larger in L98 sows than in L77 sows. Positive trends were observed for all litter traits (0.22 ± 0.07 ova, 0.12 ± 0.04 piglet, 0.09 ± 0.04 piglet, and 0.23 ± 0.06 kg/yr for ORF, TNB, NBA, and LWB, respectively) but at the expense of a degradation of prenatal and farrowing survival. A negative trend was also observed for length of productive life (-8.9 ± 3.9 d/yr). These results suggest that gains in productivity were associated with a loss of robustness.

Bovine milk-based formula leads to early maturation-like morphological, immunological, and functional changes in the jejunum of neonatal piglets

Artificial rearing and formula feeding is coming more into the focus due to increasing litter sizes and limited nursing capacity of sows. The formula composition is important to effectively support the development of the gut and prevent intestinal dysfunction in neonatal piglets. In this study, newborn piglets ( = 8 per group) were fed a bovine milk-based formula (FO), containing skimmed milk and whey as the sole protein and carbohydrate sources, or were suckled by the sow (sow milk [SM]). After 2 wk, tissue from the jejunum was analyzed for structural (i.e., morphometry) and functional (i.e., disaccharidase activity, glucose transport, permeability toward macromolecules, and immune cell presence) changes and concomitant expression of related genes. Formula-fed piglets had more liquid feces ( < 0.05) over the entire experimental period. Although FO contained twice as much lactose (46% on a DM basis) as SM (21%) and no maltose or starch, the lactase activity was lower ( < 0.05) and glucose transport capacity was higher ( < 0.05) in FO-fed pigs. The relative proportion of intraepithelial natural killer cells and proinflammatory cytokine gene expression (, , and ) was higher in FO-fed pigs ( < 0.05). Piglets fed FO had deeper crypts, larger villus area, and higher expression of caspase 3 and proliferating cell nuclear antigen ( < 0.05). Epithelial permeability toward fluorescein isothiocyanate-dextran was higher and expression of claudin-4 was lower in FO-fed piglets ( < 0.05). The data suggest an early response to bovine milk-based compounds in the FO accompanied with early onset of functional maturation and impaired barrier function. Whether lactose, absence of species-specific protective factors, or antigenicity of foreign proteins lead to to the observed intestinal reactions requires further clarification.

Evidence that oxidative stress is higher in replacement gilts than in multiparous sows

The recent success obtained in term of increasing the litter size of sows has not correlated with a reduction of replacement rate. There is thus an increased economic demand for gilts with optimal reproductive potential and longevity. Unfortunately, replacement gilts are known to be more susceptible to diseases and less productive than multiparous sows. Interestingly, reproductive performance, resistance to diseases and longevity could all be largely affected by oxidative stress. To investigate whether oxidative stress conditions could account for the poor longevity of gilts, three distinct groups of conventional Yorkshire × Landrace sows were formed based on their similar age and parity (gilts, second parity sows as well as fourth to fifth parity sows). All animals were slaughtered during the post-ovulatory period, and blood as well as tissue samples were collected. Biomarkers of oxidative damage to proteins (carbonyls) and DNA (8-OHdG) were analysed in samples. Specific mRNA expression of major antioxidants such as glutathione peroxidases 1, 3 and 4 (GPx1, GPx3, GPx4) as well as superoxide dismutases 1 and 2 (Sod1, Sod2) were monitored in liver and kidney samples by quantitative RT-PCR. Specific enzymatic activities of both GPx and SOD were measured by spectrophotometric assays. The plasma concentration of protein carbonyls was significantly different between the three groups with the highest concentration being observed in gilts (p ≤ 0.001). The mRNA expression levels of GPx1 and GPx4 were also significantly increased in the liver of gilts when compared to multiparous sows (p ≤ 0.05). SOD2 enzymatic activity was found to be higher in the liver of gilts than multiparous sows (p ≤ 0.05). Taken together, these results indicate that replacement gilts sustain significantly higher oxidative conditions than multiparous sows. Current findings may contribute to the design of nutritional regimens that will increase the productivity of gilts by counteracting oxidative stress.

Current strategies for reproductive management of gilts and sows in North America

Many advances in genetic selection, nutrition, housing and disease control have been incorporated into modern pork production since the 1950s resulting in highly prolific females and practices and technologies, which significantly increased efficiency of reproduction in the breeding herd. The objective of this manuscript is to review the literature and current industry practices employed for reproductive management. In particular the authors focus on assisted reproduction technologies and their application for enhanced productivity. Modern maternal line genotypes have lower appetites and exceptional lean growth potential compared to females of 20 yr ago. Thus, nutrient requirements and management techniques and technologies, which affect gilt development and sow longevity, require continuous updating. Failure to detect estrus accurately has the greatest impact on farrowing rate and litter size. Yet, even accurate estrus detection will not compensate for the variability in the interval between onset of estrus and actual time of ovulation. However, administration of GnRH analogs in weaned sows and in gilts after withdrawal of altrenogest do overcome this variability and thereby synchronize ovulation, which makes fixed-time AI practical. Seasonal infertility, mediated by temperature and photoperiod, is a persistent problem. Training workers in the art of stockmanship is of increasing importance as consumers become more interested in humane animal care. Altrenogest, is used to synchronize the estrous cycle of gilts, to prolong gestation for 2–3 d to synchronize farrowing and to postpone post-weaning estrus. P.G. 600® is used for induction of estrus in pre-pubertal gilts and as a treatment to overcome seasonal anestrous. Sperm cell numbers/dose of semen is significantly less for post cervical AI than for cervical AI. Real-time ultrasonography is used to determine pregnancy during wk 3–5. PGF_2α effectively induces farrowing when administered within two d of normal gestation length. Ovulation synchronization, single fixed-time AI and induced parturition may lead to farrowing synchronization, which facilitates supervision and reduces stillbirths and piglet mortality. Attendance and assistance at farrowing is important especially to ensure adequate colostrum consumption by piglets immediately after birth. New performance terminologies are presented.

Incorporation of genetic technologies associated with applied reproductive technologies to enhance world food production

Animal breeding and reproductive physiology have been closely related throughout the history of animal production science. Artificial insemination provides the best method of increasing the influence of sires with superior genetics to improve production traits. Multiple ovulation embryo transfer (MOET) provides some ability to increase the genetic influence of the maternal line as well. The addition of genetic technologies to this paradigm allows for improved methods of selecting sires and dams carrying the best genes for production and yield of edible products and resistance to diseases and parasites. However, decreasing the number of influential parents within a population also increases the risk of propagating a recessive gene that could negatively impact the species (Reprod Domest Anim 44:792-796, 2009; BMC Genomics 11:337, 2010). Furthermore, antagonistic genotypic relationships between production traits and fertility (Anim Prod Sci 49:399-412, 2009; Anim Genet 43:442-446, 2012) suggest that care must be taken to ensure that increasing the frequency of genes with a positive influence on production does not negatively impact the fertility of the replacement females entering the herd.