Effects of Relaxin on Neonatal Porcine Uterine Growth and Development

Evaluation of on-farm indicators of gilt reproductive performance potential at 21 days of age

Selection of replacements for the sow herd is one of the most important facets in swine production. Although our current methods of selection are effective, there is still a large amount of variation in sow reproductive performance traits such as pigs per sow per year (PSY). Therefore, the objective of this study was to determine if on-farm phenotypic traits at 21 d postnatal (PN) or perinatal environmental factors could predict sow reproductive performance. Data were prospectively collected from 2,146 gilts born on a commercial sow production facility and included birth and weaning weights, vulva length and width at 21 d PN, birth and nursing litter size, days nursed, average daily gain from birth to weaning, and age at first estrus. Of the initial animals, 400 (17%) were selected for the sow herd, 353 remained after removal of animals culled for non-reproductive reasons. Animals were assigned to 1 of 5 reproductive performance categories based on observation of estrus or pigs per sow per year (PSY) across two farrowings: High Fertility (HF; 23%; n = 82; ≥26 PSY), Middle Fertility (MF2; 12%; n = 43; 20–25 PSY), Low Fertility (MF3; 15%; n = 54; <20 PSY), Infertile-Estrus (IFe; 10%; n = 36; estrus, no pregnancy), and Infertile-No Estrus (IFno; 39%; n = 138; no estrus, no pregnancy). Generalized linear model analysis indicated vulva width (P = 0.03) was related to PSY, however, it only explained 1.5% of the total variation in PSY. To determine if preweaning variables were predictive of gilt fertility outcome, animals were grouped as those that became pregnant (n = 179) or not (n = 174). Vulva width tended to be greater in fertile animals versus infertile (P = 0.07). Binomial regression analysis revealed a positive relationship between vulva width and gilt fertility, however, this relationship is not strong enough to make sow herd selection decisions.

Lipidome profiles of postnatal day 2 vaginal swabs reflect fat composition of gilt's postnatal diet

We hypothesized that postnatal development of the vagina is impacted by early nutritional environment. Our objective was to determine if lipid profiles of vaginal swabs were different between postnatal gilts suckled by sow or fed milk replacer the first 48 h after birth, with or without a lard-based fat supplement. Gilts (>1.3 kg) were selected at birth across 8 litters and assigned to one of four treatments: 1) suckled by sow (S, n = 8); 2) suckled by sow plus administration of a fat supplement (SF, n = 5); 3) bottle-fed solely milk replacer (B, n = 8); or 4) bottle-fed solely milk replacer plus administration of a fat supplement (BF, n = 7). At 48 h postnatal, vaginal swabs of gilts were taken with a cytology brush, and lipids were extracted for analysis using multiple reaction monitoring (MRM)-profiling. Lipids extracted from serum collected at 48 h from gilts, milk collected at 24 h from sows, and milk replacer were also analyzed with MRM-profiling. Receiver operating characteristic curve analysis found 18 lipids recovered from vaginal swabs that highly distinguished between S and B gilts [area-under-the-curve (AUC) > 0.9], including phosphatidylethanolamine with 34 carbons and four unsaturations in the fatty acyl residues [PE (34:4)]. Twelve lipids from vaginal swabs highly correlated (r > 0.6; p < 0.01) with nutrition source. Lipids with greater abundance in milk replacer drove association. For example, mean intensity of PE (34:4) was 149-fold higher in milk replacer than colostrum. Consequently, PE (34:4) was found to have 1.6- and 2.12-fold higher levels in serum and vaginal swab samples (p < 0.001), respectively, of B gilts as compared to S gilts. Findings support that vaginal swabs can be used to noninvasively study effects of perinatal nutrition on tissue composition.

Relationships between day one piglet serum immunoglobulin immunocrit and subsequent growth, puberty attainment, litter size, and lactation performance

Colostrum affects gut and uterine gland development in the neonatal piglet, suggesting that subsequent growth and reproductive performance may be affected. Measuring immunoglobulin in piglet serum using the immunoglobulin immunocrit on Day 1 of age provides a simple, inexpensive indication of the amount of colostrum acquired by the piglet in the first day of life. Relationships between serum immunoglobulin immunocrit measures and subsequent growth rates, age at puberty, incidence of puberty failure, litter size, and lactation performance were examined in pigs born and subsequently farrowing between 2009 and 2013. Immunoglobulin immunocrit measures were collected on 16,762 piglets on Day 1 of age. Of these piglets, BW measurements were available from 15,324 (7,684 males and 7,640 females) piglets at a range of ages from weaning to 200 d of age, allowing an assessment of growth rates. Age at puberty was recorded from a subset of 2,857 of the females after observing them for estrous behavior from approximately 170 to 250 d of age. To examine relationships between d 1 immunocrit and puberty failure, gilts with immunocrit measures that failed to reach puberty (n = 119) were matched with littermate gilts with immunocrit measures that achieved puberty (n = 167). Similarly, number born alive was collected on a subset (n = 799) of females from first to fourth parities for which d 1 immunocrits were measured on them as neonates. Finally, d 1 immunocrit effect on adult lactational competence was assessed by measuring litter average (offspring of 440 females) and litter average piglet preweaning growth rate (offspring of 774 females) in females where d 1 immunocrits were available from them as neonates. Results indicated that low d 1 immunocrits were subsequently associated with reduced growth (P < 0.01), increased age at puberty (P < 0.01), reduced number born alive (P < 0.05), reduced litter average immunocrit (P < 0.05), and reduced litter average preweaning growth rate during lactation (P < 0.05). This suggests that management efforts to improve the amount of colostrum ingested by neonatal piglets would result in beneficial changes in production efficiency, particularly for gilts destined for the breeding herd. It also suggests that the immunoglobulin immunocrit can be useful in monitoring colostrum ingestion to maximize the beneficial effects of colostrum on subsequent performance.

Accelerated pre-weaning growth rates in dairy calves: do antioxidants have a place?

Accelerated growth of dairy calves in the pre-weaning phase has been shown to increase productivity of dairy cows during their lifetime. The increased weight gain during the pre-weaning phase is not the driving factor behind the changes in life-time productivity as the weight gained is inconsequential in terms of pre-lactation and weight gain. Furthermore, there are no differences in weight of heifers at the start of first lactation. The increased weight gain during the pre-weaning period must, therefore, initiate cellular changes within the animal. Research has focussed on increasing total nutritional supply or an increase in protein supply for promotion of such changes. The benefits of antioxidants in animal nutrition have been known for a long period of time. However, they have gained prominence with enforced reduction in use of antibiotics in many animal production systems. The role of antioxidants in nutrition of both the calf and the dam before parturition is critical for preventing disease and optimising growth weight of the pre-weaned calf. However, studies are yet to demonstrate a role, outside of preventive health, for the use of antioxidants in the pre-weaning period for increasing total life-time production of the dairy cow.

The effect of increasing the nutrient and amino acid concentration of milk diets on dairy heifer individual feed intake, growth, development, and lactation performance

Increasing early (<3 mo) nutrient feeding levels and growth rate of dairy calves has been found to increase their milk production potential. The objective of this study was to compare the effect of offering milk diets with or without added carbohydrates and amino acids on calf growth, weaning age, and subsequent growth and milk yield of dairy heifers in their first lactation. Friesian calves born at Massey University (n=57) were selected at random, weighed, and allocated to receive 1 of 3 diets. All calves were fed colostrum from 1 to 3d of age, followed by 4 L of whole milk (WM) per head per day and probiotics between 3 and 18d of age. At 18d of age, calves were weighed to ensure mean body weight (BW); then, at 19 d of age, calves changed diets to 1 of 3 treatments, which reached full treatment rate at 21 d of age. The diets were 4 L/head per day of WM (M); 4 L/head per day of WM plus 200 g of plant carbohydrates (MP); and 4 L/head per day of WM plus 200 g of plant carbohydrates with amino acids (MPA). Calves were weaned upon reaching a BW of 90 kg. During this period, BW, body condition, and hip height and width were measured. The heifers were commingled and grazed on ryegrass and white clover pastures until calving at 23 mo of age, when BW, body condition, and hip height and width were measured again. Milk yield and composition were measured throughout first lactation. At weaning, calves fed MPA had greater mean BW gain, a lower number of days to target BW, and a greater mean hip width gain compared with calves in the M group, although mean gain in hip height did not differ among treatments. Total calf starter intake during the milk period was lower for MPA-fed calves compared with those offered M, mainly due to a shorter milk feeding period required to attain the 90-kg weaning weight, whereas mean daily starter intake and straw intake did not differ. No difference was observed in the calving rate or calving age of heifers in any of the dietary feeding groups. First lactation fat-corrected milk yield, milk fat percentage, and total milk fat and protein yields were greater for animals reared on MP and MPA compared with M. Body weight, hip height and width at parturition, milk protein percentage, somatic cell count, or days in milk did not differ among treatments. Increasing nutrient intake, during the milk feeding period, improved the BW gain of calves and milk production of dairy heifers during first lactation.

Lactation Biology Symposium: The effect of nutrient intake from milk or milk replacer of preweaned dairy calves on lactation milk yield as adults: a meta-analysis of current data

Data from calf studies conducted over the past 20 yr has shown that preweaning nutrient intake, from milk or milk replacer, can have profound effects on development of the calf that enhance first lactation and lifetime productivity. Many of the studies show positive but not significant effects of preweaning nutrition on long-term productivity, primarily due to a lack of power, usually due to inadequate animal numbers per treatment. Meta-analyses were conducted using Comprehensive Meta-Analysis (CMA) software (version 2.2.064; Biostat, Englewood, NJ; Borenstein et al., 2005) to evaluate the effects of preweaning nutrient intake and preweaning ADG on first lactation milk production from studies where milk yield and preweaning treatment data were adequately described. Currently, 12 studies have been reported, describing milk yield of calves that had been fed various levels of preweaning nutrients, from both milk and milk replacer, and 11 evaluated the effect of preweaning ADG on long-term productivity. The estimated effect size for treatment (level of milk or milk replacer intake) and ADG were calculated. Using a random effects model, the overall milk yield response based on treatment was 435 ± 117 kg/lactation (P < 0.001), demonstrating that among the data sets milk yield in the first lactation was increased by increasing nutrient intake from milk or milk replacer in preweaned calves. Meta-regression of the effect of ADG resulted in the following equation: milk yield = -106 kg + 1,551.4 kg × ADG (kg/d; P = 0.01) indicating that for every kilogram of preweaning ADG, first lactation milk yield increased by 1,550 kg. Furthermore, the meta-analysis yielded an odds ratio of 2.09 (P = 0.001) indicating that calves fed for greater preweaning ADG were 2 times more likely to have greater milk yield in the first lactation. Finally, the 2001 Dairy NRC calf model was used to estimate the difference, within study, of intake over maintenance from milk replacer, using either the actual data or the published ADG; the difference in intake over maintenance was used as a predictor in a meta-regression and resulted in the following equation: milk yield = -60 kg + 1,100 kg × estimated difference in intake over maintenance (P = 0.02). The data demonstrate that nutrient intake from milk or milk replacer during the preweaning period positively impacted long-term productivity of dairy calves and provides new management opportunities to improve milk yield of dairy cattle. These data appear to indicate that there are significant developmental functions being programmed in the neonatal calf that require further investigation.

Preweaning milk replacer intake and effects on long-term productivity of dairy calves

The preweaning management of dairy calves over the last 30 yr has focused on mortality, early weaning, and rumen development. Recent studies suggest that nutrient intake from milk or milk replacer during the preweaning period alters the phenotypic expression for milk yield. The objective of this study was to investigate the relationship between nutrient intake from milk replacer and pre- and postweaning growth rate with lactation performance in the Cornell dairy herd and a commercial dairy farm. The analysis was conducted using traditional 305-d first-lactation milk yield and residual lactation yield estimates from a test-day model (TDM) to analyze the lactation records over multiple lactations. The overall objective of the calf nutrition program in both herds was to double the birth weight of calves by weaning through increased milk replacer and starter intake. First-lactation 305-d milk yield and residuals from the TDM were generated from 1,244 and 624 heifers from the Cornell herd and from the commercial farm, respectively. The TDM was used to generate lactation residuals after accounting for the effects of test day, calving season, days in milk, days pregnant, lactation number, and year. In addition, lactation residuals were generated for cattle with multiple lactations to determine if the effect of preweaning nutrition could be associated with lifetime milk yield. Factors such as preweaning average daily gain (ADG), energy intake from milk replacer as a multiple of maintenance, and other growth outcomes and management variables were regressed on TDM milk yield data. In the Cornell herd, preweaning ADG, ranged from 0.10 to 1.58 kg, and was significantly correlated with first-lactation yield; for every 1 kg of preweaning ADG, heifers, on average, produced 850 kg more milk during their first lactation and 235 kg more milk for every Mcal of metabolizable energy intake above maintenance. In the commercial herd, for every 1 kg of preweaning ADG, milk yield increased by 1,113 kg in the first lactation and further, every 1 kg of prepubertal ADG was associated with a 3,281 kg increase in first-lactation milk yield. Among the 2 herds, preweaning ADG accounted for 22% of the variation in first-lactation milk yield as analyzed with the TDM. These results indicate that increased growth rate before weaning results in some form of epigenetic programming that is yet to be understood, but has positive effects on lactation milk yield. This analysis identifies nutrition and management of the preweaned calf as major environmental factors influencing the expression of the genetic capacity of the animal for milk yield.

Relaxin physiology in the female reproductive tract during pregnancy

The characteristic functions of relaxin are associated with female reproductive tract physiology. These include the regulation of biochemical processes involved in remodeling the extracellular matrix of the cervix and vagina during pregnancy and rupture of the fetal membranes at term. Such modifications enable the young to move unimpeded through the birth canal and prevent dystocia. However, relaxin's physiological actions are not limited to late gestation. New functions for this peptide hormone in implantation and placentation are also emerging. Relaxin promotes uterine and placental growth and influences vascular development and proliferation in the endometrium. This chapter provides an overview of the current literature on relaxin physiology in the uterus, cervix and vagina of pregnant females and the impact on fetal health. It also outlines the potential mechanisms of relaxin action, particularly in the cervical extracellular matrix and uterine endometrium.

Epigenetic programming of porcine endometrial function and the lactocrine hypothesis

Epigenetic programs controlling development of the female reproductive tract (FRT) are influenced by the effects of naturally occurring bioactive agents on patterns of gene expression in FRT tissues during organizationally critical periods of foetal and perinatal life. Aberrations in such important cellular and molecular events, as may occur with exposure to natural or manmade steroid or peptide receptor-modulating agents, disrupt the developmental program and can change the developmental trajectory of FRT tissues, including the endometrium, with lasting consequences. In the pig, as in other mammals, maternal programming of FRT development begins pre-natally and is completed post-natally, when maternal effects on development can be communicated via signals transmitted in milk. Studies involving relaxin (RLX), a prototypic milk-borne morphoregulatory factor (MbF), serve as the basis for ongoing efforts to identify maternal programming events that affect uterine and cervical tissues in the neonatal pig. Data support the lactocrine hypothesis for delivery of MbFs to neonates as a specific consequence of nursing. Components of a maternally driven lactocrine mechanism for RLX-mediated signalling in neonatal FRT tissues, including evidence that milk-borne RLX is delivered into the neonatal circulation where it can act on RLX receptor (RXFP1)-positive neonatal tissues to affect their development, are in place in the pig. The fact that all newborn mammals drink milk extends the timeframe of maternal influence on neonatal development across many species. Thus, lactocrine transmission of milk-borne developmental signals is an element of the maternal epigenetic programming equation that deserves further study.

Neonatal porcine endometrial development and epithelial proliferation affected by age and exposure to estrogen and relaxin

In the pig, temporospatially regulated proliferation of uterine luminal (LE) and glandular (GE) epithelium between birth (postnatal day=PND 0) and PND 15 is essential for success of endometrial development. Exposure of gilts to estrogen (E) or relaxin (RLX) during this period disrupts uterine development, and neonatal E exposure can compromise adult uterine function. Neonatal uterotrophic effects of E and RLX, administered for 2 days beginning on PND 12, can be inhibited with the antiestrogen ICI 182,780 (ICI) indicating crosstalk between RLX and E signaling systems. Here, objectives were to determine effects of: (study 1) neonatal age and (study 2) exposure to E, RLX, and ICI on porcine neonatal uterine histoarchitecture and patterns of epithelial cell proliferation as reflected by proliferating cell nuclear antigen labeling index. In study 1, uteri were obtained on PND 0, 3, 6, 9, 12 and 15. Glandular epithelium, absent at birth, was observed by PND 3. Overall, epithelial labeling index increased from birth to PND 3, declined from PND 6-9 in LE and GE, and increased to PND 15 in GE. In study 2, uteri were collected on PND 14 after administration of vehicle, E, or RLX for 2 days, or following pretreatment with ICI. Alone, E was uterotrophic and adenogenic and increased labeling index in both LE and GE. Both RLX and ICI increased proliferation in GE. Effects of E and RLX were attenuated by ICI, providing further support for crosstalk between these signaling systems in the developing neonatal porcine endometrium.

Expression of LGR7 and LGR8 by neonatal porcine uterine tissues and transmission of milk-borne relaxin into the neonatal circulation by suckling

Estrogen receptor-dependent organizational events between birth [postnatal day (PND) 0] and PND 14 affect development and function of porcine uterine tissues. Observations that uterotrophic effects of relaxin (RLX) in neonatal gilts were inhibited by the antiestrogen ICI 182,780 suggested that a RLX signaling system, capable of cross-talk with the estrogen receptor, evolves during a critical period for uterine programming (PND 0-14). Objectives were to determine 1) effects of age and estrogen exposure from birth on porcine uterine RLX/insulin-like 3 receptor (LGR7/LGR8) expression and 2) whether milk serves as a natural source of RLX in neonatal pigs. Uterine LGR7/LGR8 expression, detected by RT-PCR and in situ hybridization on PND 0, 7, and 14, was predominantly stromal for LGR7, myometrial for LGR8, and increased with age and after treatment with estradiol valerate (50 microg/kg body weight x d) from birth. Stromal expression of LGR7 was also detected immunohistochemically. Milk RLX concentrations declined (P < 0.001) from 17.3 +/- 1.4 ng/ml (lactation d 0) to 1.7 +/- 0.3 ng/ml (lactation d 14). RLX, present in the serum of nursing pigs on PND 0 and 1, was undetectable before nursing and in neonates fed RLX-free milk replacer for 12 h. Thus, a developmentally regulated, estrogen-sensitive LGR7 and LGR8 receptor system is present in the porcine uterus at birth and may be activated by milk-borne RLX delivered into the circulation during the first 48 h of postnatal life. Maternal lactocrine contributions to the neonatal hormonal milieu could affect the developmental programming of uterine and other somatic tissues.

Uterotrophic effects of relaxin related to age and estrogen receptor activation in neonatal pigs

While uterotrophic effects of relaxin are well documented, the mechanism through which relaxin promotes uterine growth is incompletely understood. Studies in rats suggest that relaxin-stimulated uterine edema depends on estrogen receptor (ER) activation. Here, neonatal pigs were used to investigate the interaction between relaxin and ER signaling pathways. Gilts were treated either at birth (postnatal day (PND) 0) (study 1) before the onset of endometrial ERα expression, or on PND 12 (study 2) after the onset of ERα expression. In study 1, gilts were treated with estradiol-17β or porcine relaxin for two days and uteri were collected on PND 2. In study 2, PND 12 gilts were treated with a single injection of the ER antagonist ICI 182,780 (ICI) or vehicle. Two hours later, gilts were given either estradiol-17β or porcine relaxin for two days. When administered for two days from birth (study 1), neither estradiol-17β nor relaxin affected uterine weight or protein content. However, uterine luminal epithelial height was greater in relaxin- than in vehicle-treated gilts. In contrast, in study 2, both estradiol and relaxin increased uterine weight, protein content and uterine luminal epithelial height on PND 14. These effects were inhibited by pre-treatment with ICI in both estradiol- and relaxin-treated gilts. The results indicate that uterotrophic effects of relaxin in the neonatal pig are related to age and to both the relative presence and state of activation of the ER system in developing uterine tissues between birth and PND 14.