Plasma metabolomics indicates metabolic perturbations in low birth weight piglets supplemented with arginine

Effects of oral glutamine supplementation on jejunal morphology, development, and amino acid profiles in male low birth weight suckling piglets

Background

It has been shown that small intestine development in low birth weight (LBW) piglets is impaired. Glutamine (Gln) has been reported to improve piglet health and intestinal function in weaned piglets, but data is scarce in suckling piglets. This study was conducted to investigate the effects of oral Gln supplementation compared to Alanine (Ala) on jejunal development and function in 5 and 12 d old male LBW and normal birth weight (NBW) suckling piglets.

Results

Gln had no effect on the jejunal morphology, development, tissue and digesta amino acid profiles and mRNA abundance of genes involved in amino acid transport, metabolism, glutathione synthesis in LBW piglets when compared to Ala supplementation and birth weight controls at 5 and 12 d. Only the concentration of Gln in jejunal tissue was higher in NBW piglets supplemented with Gln compared to Ala at 5 d (P < 0.05). A comparison of the birth weight groups showed no differences between LBW and NBW piglets at 5 and 12 d in any parameter. Jejunal crypt depth, villus height / width, tunica muscularis thickness, number of goblet and IgA positive cells, the ratio of jejunal RNA to DNA and the concentration of DNA, protein and RNA changed (P < 0.05) from 5 compared to 12 d. The concentrations of several free, and protein bound amino acids as well as amino metabolites differed between age groups in jejunal tissue but the digesta concentrations were affected to a lesser extent.

Conclusions

Oral Gln supplementation to suckling male piglets over the first 12 d of life was not associated with changes in jejunal parameters measured in this study. The absence of effects may indicate that Gln is absorbed as well as metabolized in the upper intestinal tract and thus could benefit intestinal development at a more proximal location.

Amino Acids in Swine Nutrition and Production

Amino acids are the building blocks of proteins in animals, including swine. With the development of new analytical methods and biochemical research, there is a growing interest in fundamental and applied studies to reexamine the roles and usage of amino acids (AAs) in swine production. In animal nutrition, AAs have been traditionally classified as nutritionally essential (EAAs) or nutritionally nonessential (NEAAs). AAs that are not synthesized de novo must be provided in diets. However, NEAAs synthesized by cells of animals are more abundant than EAAs in the body, but are not synthesized de novo in sufficient amounts for the maximal productivity or optimal health (including resistance to infectious diseases) of swine. This underscores the conceptual limitations of NEAAs in swine protein nutrition. Notably, the National Research Council (NRC 2012) has recognized both arginine and glutamine as conditionally essential AAs for pigs to improve their growth, development, reproduction, and lactation. Results of recent work have also provided compelling evidence for the nutritional essentiality of glutamate, glycine, and proline for young pigs. The inclusion of so-called NEAAs in diets can help balance AAs in diets, reduce the dietary levels of EAAs, and protect the small intestine from oxidative stress, while enhancing the growth performance, feed efficiency, and health of pigs. Thus, both EAAs and NEAAs are needed in diets to meet the requirements of pigs. This notion represents a new paradigm shift in our understanding of swine protein nutrition and is transforming pork production worldwide.

Developing a Reference Database for Typical Body and Organ Growth of the Artificially Reared Pig as a Biomedical Research Model

Objectives: The pig is a common model utilized to support substantiation of novel bioactive components in infant formula. However, reference ranges for outcomes to determine safety are unclear. Our objective was to use historical data to objectively define typical body and organ growth metrics of the domesticated pig in research. Methods: Twenty-two studies were compiled to assess typical growth of body and organ weights in young pigs. Metadata were organized to include milk replacer sources, bioactive components, sex, breed, source of herd, feeding regimen, and rearing environment. A combination of statistical models including simple linear regression and linear mixed effect models were used to assess typical growth patterns. Results: Over 18,000 data points from 786 animals were available. In general, minimal differences in the growth of pigs who were male and female, artificially- or sow-reared, or fed ad libitum- or by scheduled-feeding, were observed in the first 30 days of life (P > 0.05). A weight-for-age chart from reference pigs was developed to compare body weights of pigs demonstrating growth characterized as accelerated, typical, reduced, and failure to thrive to illustrate effects of dietary interventions. Distributions of relative brain, liver, and intestine weights (as % of total body weight) were similar between rearing environments and sexes. An alternative bivariate level approach was utilized for the analysis of organ weights. This approach revealed significant biologically-relevant insights into how deficient diets can affect organ weight that a univariate level assessment of weight distribution was unable to detect. Conclusions: Ultimately, these data can be used to better interpret whether bioactive ingredients tested in the pig model affect growth and development within typical reference values for pigs in the first 30 days of life.

Effects of Dietary L-arginine Supplementation from Conception to Post- Weaning in Piglets

Weaned piglets experience sudden changes in their dietary patterns such as withdrawal from the easily digestible watery milk to a coarse cereal diet with both systemic and intestinal disruptions coupling with the expression of pro-inflammatory proteins which affects the immune system and the concentrations of haptoglobin including both positive and negative acute-phase proteins in the plasma. L-arginine is an important protein amino acid for piglets, but its inadequate synthesis is a nutritional problem for both sows and piglets. Recent studies indicated that dietary supplementation of L-arginine increased feed intake, uterine growth, placental growth and nutrient transport, maternal growth and health, embryonic survival, piglets birth weight, piglet's growth, and productivity, and decreased stillbirths. L-arginine is essential in several important pathways involved in the growth and development of piglets such as nitric oxide synthesis, energy metabolism, polyamine synthesis, cellular protein production and muscle accretion, and the synthesis of other functional amino acids. However, the underlying molecular mechanism in these key pathways remains largely unresolved. This review was conducted on the general hypothesis that L-arginine increased the growth and survival of post-weaning piglets. We discussed the effects of dietary L-arginine supplementation during gestation, parturition, lactation, weaning, and post-weaning in pigs as each of these stages influences the health and survival of sows and their progenies. Therefore, the aim of this review was to discuss through a logical approach the effects of L-arginine supplementation on piglet's growth and survival from conception to postweaning.

A Single Dose of Fat-Based Energy Supplement to Light Birth Weight Pigs Shortly After Birth Does Not Increase Their Survival and Growth

Simple Summary

In modern piggeries, due to the increase in litter size (number of piglets born alive), the number of piglets born at a low birth weight (typically under 1.0 kg) is increasing. Those piglets have a lower chance of survival because of their lower body energy reserves, and therefore are of concern for the farmers. Piglets weighing less than 1.1 kg at birth were given an oral dose of fat-based energy (2 mL of coconut oil or 2 mL of a commercial product), 2 mL of water or were only handled but given nothing. This was done to investigate the effects of providing an energy boost at birth on the chances of survival of small piglets. Parameters measured to assess the piglets’ vitality were survival, blood glucose content, rectal temperature, behaviour test of vigour and weight gain. Unfortunately, there was no effect of the energy dose on the parameters measured. Therefore, we conclude that a single dose of energy at birth does not enhance the chances of survival of small piglets. Therefore, using energy product to improve piglet survival at birth may not be the most efficient strategy.

Abstract

Low birth weight piglets are at high risk of mortality, because of the rapid depletion of their energy reserves after birth. At 3 h postpartum, 405 piglets weighing <1.1 kg were either dosed orally with 2 mL of (1) coconut oil (CO, 74 kJ/2 mL, n = 107 piglets), (2) commercial product (CP, 71 kJ/2 mL, n = 101 piglets), (3) water (W, 0 kJ/2 mL, n = 100 piglets) or (4) were sham-dosed (S, n = 97 piglets). Treatments were applied within litter (97 sows). Before treatment piglets were weighed, scored for vitality and blood glucose concentration (subset: CO = 45 piglets, CP = 38 piglets, W = 49 piglets and S = 44 piglets) and rectal temperature were measured. Rectal temperature was remeasured 1 h post-treatment (4 h postpartum). At 24 h post-treatment (27 h postpartum), vitality, weight and blood glucose were remeasured. Piglets were weighed on D5, D7, D10, D14, D21 and at weaning (27 ± 0.1 day old). Mortality rate and cause were recorded until 24h period post-treatment and until weaning. Data were analysed using Generalised Linear Mixed Models in SAS. There was no overall effect of treatment on any of the parameters measured. In conclusion, a single oral of fat-based energy supplement dose at birth did not improve growth, survival, rectal temperature or vitality of low birth weight piglets.

Efficacy of energy supplementation on growth performance and immune response of suckling pigs

Three studies were performed to determine the effects of oral energy sources on the performance, immune status, and intestinal morphology of piglets. In Exp. 1, 50 litters were selected based on genotype and parity order to determine the optimum amount of supplemental energy for neonatal pigs. They were distributed according to a 5 × 5 Latin square design, in which columns were represented by 5 sows and rows were represented by 5 newborn weight categories. Treatments consisted of 2 oral doses of 0, 2, 4, 8, or 16 mL of rice bran oil (RBO). There was a positive response of RBO on BW with a numerical difference (P = 0.12) and a significant linear effect (P = 0.04) at weaning. In Exp. 2, litters (n = 340) were randomly allotted to a 2 × 2 factorial arrangement of treatments: RBO supplemented either through oral doses (without supplementation or with 2 mL of RBO) or through prestarter feed (without supplementation or with 2% of RBO replacing 2% of soybean oil). Piglets orally receiving RBO showed a numerical increase in BW at weaning (P = 0.101) compared with the control group. Moreover, piglets supplemented by prestarter feed tended to increase feed intake (P = 0.084). In Exp. 3, litters (n = 245) were selected based on genotype and parity order and they were distributed according to a 7 × 7 Latin square design planed in the same way as in Exp. 1. Each neonatal pig within a litter was randomly assigned to 1 of 7 treatments: 1) control (no supplementation), 2) 2 mL of RBO enriched with omega-3 fatty acids, 3) 2.33 mL of pure glycerin, 4) 1.3 mL of soybean oil, 5) 1.4 mL of linseed oil, 6) 1.68 mL of coconut oil, and 7) 2 mL of RBO. Animal performance was analyzed using 2 data sets: all data (average initial BW of 1.479 kg) and low birth weight (LBW) piglet data (≤1.220 kg initial BW with average of 0.985 kg). Body weight or BW gain (BWG) were not different among treatments (P > 0.10) when all data were analyzed. However, LBW piglets fed coconut oil tended to increase BW (P = 0.099) during the first week. In conclusion, the oral use of RBO may increase BW at weaning and the supplementation by prestarter feed may enhance the feed intake of piglets. In addition, coconut oil may increase BW of LBW piglets in the first week of life without affecting mortality, immune response, or gut morphology. The routine practice of oral supplementation of energy for newborn pigs could be an important tool in swine production.

BOARD-INVITED REVIEW: Arginine nutrition and metabolism in growing, gestating, and lactating swine

Arginine (Arg) has traditionally not been considered as a deficient nutrient in diets for gestating or lactating swine due to the assumption that these animals can synthesize sufficient amounts of Arg to meet their physiological needs. The lack of full knowledge about Arg nutrition has contributed to suboptimal efficiency of pork production. Over the past 25 yr, there has been growing interest in Arg metabolism in the pig, which is an agriculturally important species and a useful model for studying human biology. Arginine is a highly abundant amino acid in tissues of pigs, a major amino acid in allantoic fluid, and a key regulator of gene expression, cell signaling, and antioxidative reactions. Emerging evidence suggests that dietary supplementation with 0.5% to 1% Arg maintains gut health and prevents intestinal dysfunction in weanling piglets, while enhancing their growth performance and survival. Also, the inclusion of 1% Arg in diets is required to maximize skeletal muscle accretion and feed efficiency in growing pigs, whereas dietary supplementation with 1% Arg reduces muscle loss in endotoxin-challenged pigs. Furthermore, supplementing 0.83% Arg to corn- and soybean meal-based diets promotes embryonic/fetal survival in swine and milk production by lactating sows. Thus, an adequate amount of dietary Arg as a quantitatively major nutrient is necessary to support maximum growth, lactation, and reproduction performance of swine. These results also have important implications for improving the nutrition and health of humans and other animals.

Supplementation of sows with L-Arginine during gestating and lactation affects muscle traits of offspring related with postnatal growth and meat quality: From conception to consumption

This study investigated the effect of dietary inclusion of 25 g/day of _L-Arginine (n = 7) or iso‑nitrogenous amounts of alanine (n = 6) from d 30 of gestation to d 28 of lactation of sows on performance, muscle traits and meat quality in offspring. From each litter, heaviest and smallest littermate of both sexes were reared from d 28 and slaughtered at d 140 in accordance with a 2³factorial design. A response to _L-Arginine were obtained on small females where _L-Arginine increased birth weight, however this effect disappeared at weaning. _L-Arginine increased daily gain by 7% and increased the cross-sectional area of the M. semitendinosus in small females by 14%, suggesting an increased lean ratio. Mechanistic studies showed firstly, that small female littermates had increased number of muscle fibres (myogenesis) after _L-Arginine treatment (11%) and secondly increased total DNA (12%) as a consequence of satellite cell proliferation. Traits describing tenderness seem to be affected by _L-Arginine but further studies are needed.

Influence of l-carnitine and l-arginine on protein synthesis and maturation of the semitendinosus muscle of lightweight piglets

Lightweight (LW) piglets from large litters display impaired growth performance compared with heavier littermates. This study investigated the growth performance and muscle development of early-weaned LW piglets (birthweight <1.2 kg) from large litters (17.3 ± 3.0 total born per litter), fed ad libitum a milk replacer supplemented with either l-carnitine (CAR) or l-arginine (ARG) from day 7 to day 28 of age. In total, 36 female and entire male Swiss Large White piglets, weaned on day 7 of age, were artificially reared in pairs in rescue decks. They were allocated to one of three dietary treatments: unsupplemented control (CON), 0.48 g l-carnitine·piglet^-1 ·day^-1 (CAR) or 1.20 g l-arginine·kg body weight^-1 ·day^-1 (ARG). Milk replacer was prepared daily in a 1:4 powder-to-water ratio and fed ad libitum. Piglets were weighed at birth and on days 7, 14, 21 and 28. Feed intake was assessed daily. Piglets were euthanized on day 28. The entire semitendinosus muscle (STM) was collected, and organs were weighed. Subsequently, the STM was divided into the light (STM_l ) and dark (STM_d ) portion, and contractile and metabolic traits were analysed by ATP histochemistry, enzyme activities and gene expression. No differences in growth performance, organ and STM weight and on contractile traits were found between groups. A tendency (p < .10) for an elevated lipid oxidation enzyme activity in the STM_l and STM_d and greater (p < .05) phosphorylation of the mammalian target of rapamycin pathway in the STM_l of CAR compared with CON piglets was found. Despite these metabolic responses, the lack of effect of CAR and ARG supplementation on growth performance suggests that providing the milk replacer ad libitum in combination with added CAR and ARG is insufficient for eliciting faster growth of LW piglets.

Milk replacers supplemented with either L-arginine or L-carnitine potentially improve muscle maturation of early reared low birth weight piglets from hyperprolific sows

As a result of the selection for genotypes with greater sow prolificacy, litter size increased and, concomitantly, average litter birth weight and early postnatal survival rates of low birth weight (L-BtW) offspring decreased. This study compared the impact of l-carnitine (CAR) and l-arginine (ARG) supplemented with a milk replacer and fed to L-BtW piglets born from large litters from days 7 to 28 of age on growth performance, carcass composition, organ and Semitendinosus muscle (STM) development. A total of 30 female and castrated Swiss Large White piglets weaned at 7 days of age were assigned to three milk replacer diets containing either no supplement (CON), CAR (0.40 g/piglet per day) or ARG (1.08 g/kg BW per day). Piglets were kept in pairs in rescue decks (0.54 m2). They were weighed daily and daily allowance of both, feed and ARG, was adjusted accordingly. Thus, feed allowance depended on growth. Each day, the milk replacer was prepared with water (1:4). Feed (allowance: 60 g dry matter/kg BW per day) was offered daily in six equal rations. Feed intake and feed efficiency was assessed for the pairs and apparent total tract-energy and -protein digestibility was determined from days 21 to 28 of age. On day 28, piglets were euthanized, blood samples were collected and the whole STM and organs were weighed. In STM, the size and metabolic properties of myofibers were determined. No difference in growth performance was found between dietary treatments, but piglets from the CAR group tended (P<0.10) to grow faster during the 1st experimental week and consume more feed from days 14 to 21 as compared with piglets of the CON group. A setback in growth in the last week in the CAR group coincided with the lower (P<0.05) energy and protein digestibility. Dietary treatments had no effect on STM and organ weight and myofiber size. Compared with the other groups, there were trends (P<0.10) for blood serum urea and glucose level to be greater in CAR and for non-esterified fatty acid level to be greater in ARG piglets. The greater (P<0.05) ratio of lactate dehydrogenase to either citrate synthase or β-hydroxyacyl-CoA dehydrogenase indicated that the relative importance of the glycolytic compared with the oxidative pathway was greater in STM of CAR and ARG compared with CON piglets. These results suggest that ARG and CAR supplements were beneficial for muscle maturation whereas findings on phenotypic traits were rather unsystematic.

Nutritional support for low birth weight infants: insights from animal studies

Infants born with low birth weights (<2500 g, LBW), accounting for about 15 % of newborns, have a high risk for postnatal growth failure and developing the metabolic syndromes such as type 2 diabetes, CVD and obesity later in life. Improper nutrition provision during critical stages, such as undernutrition during the fetal period or overnutrition during the neonatal period, has been an important mediator of these metabolic diseases. Considering the specific physiological status of LBW infants, nutritional intervention and optimisation during early life merit further attention. In this review, the physiological and metabolic defects of LBW infants were summarised from a nutritional perspective. Available strategies for nutritional interventions and optimisation of LBW infants, including patterns of nutrition supply, macronutrient proportion, supplementation of amino acids and their derivatives, fatty acids, nucleotides, vitamins, minerals as well as hormone and microbiota manipulators, were reviewed with an aim to provide new insights into the advancements of formulas and human-milk fortifiers.

Intrauterine growth-restricted piglets have similar gastric emptying rates but lower rectal temperatures and altered blood values when compared with normal-weight piglets at birth

Intrauterine growth-restricted (IUGR) piglets have lower survival rates and are more likely to have empty stomachs 24 h after birth than normal piglets. Although hypoglycemia may result from low colostrum intake per se, it is not known if slow gastric emptying may be an additional risk factor for poor immunization and glucose absorption in IUGR piglets. It is estimated that IUGR piglets consume less colostrum per kilogram BW than normal-weight piglets within the first 24 h, which could be due to a slower gastric emptying rate and a compromised energy metabolism. Therefore, we hypothesized that the gastric emptying rate and blood glucose would be lower in IUGR piglets. We investigated gastric emptying rates in normal and IUGR piglets and blood glucose and rectal temperatures at birth and after 15, 30, 60, and 120 min. In addition, blood parameters relevant for metabolism were studied. Forty-eight piglets (24 normal and 24 IUGR) were classified at birth as either normal or IUGR on the basis of head morphology. Piglets were removed from the sow at birth before suckling, and birth weight was recorded. Pooled porcine colostrum was tube-fed to all piglets at 12 mL/kg BW as soon as possible after birth (t = 0 min). The piglets were randomly allocated to be euthanized at 15, 30, 60, and 120 min (all groups, = 6) after bolus feeding, and the weights of the stomach and its residuals were recorded. There was no difference in gastric emptying rates between normal and IUGR piglets ( = 0.129); however, gastric DM residuals tended to by greater in IUGR piglets than normal piglets ( = 0.085). Overall, IUGR piglets had lower rectal temperatures (36.2°C ± 0.2°C vs. 37.5°C ± 0.2°C; < 0.001) and plasma glucose levels (2.8 ± 0.2 vs. 4.1 ± 0.2 mmol; < 0.001) than normal piglets. Interactions between piglet classification and time were observed in plasma values for NEFA, -3-hydroxybutyrate, albumin, aspartate, and alanine amino transferase, with greater levels in normal piglets at 15 min ( < 0.05) and 30 min for bile acid ( < 0.05) compared to IUGR piglets. In conclusion, the gastric emptying rates between normal and IUGR piglets were similar, but gastric DM residuals tended to be greater in IUGR piglets. Differences were observed in blood values and rectal temperatures, with lower values in IUGR piglets. Therefore, it is likely that factors like hypothermia and possibly reduced metabolic function are more important during the first hours after birth than gastric retention per se.

Catabolism and safety of supplemental L-arginine in animals

L-arginine (Arg) is utilized via multiple pathways to synthesize protein and low-molecular-weight bioactive substances (e.g., nitric oxide, creatine, and polyamines) with enormous physiological importance. Furthermore, Arg regulates cell signaling pathways and gene expression to improve cardiovascular function, augment insulin sensitivity, enhance lean tissue mass, and reduce obesity in humans. Despite its versatile roles, the use of Arg as a dietary supplement is limited due to the lack of data to address concerns over its safety in humans. Data from animal studies are reviewed to assess arginine catabolism and the safety of long-term Arg supplementation. The arginase pathway was responsible for catabolism of 76-85 and 81-96 % Arg in extraintestinal tissues of pigs and rats, respectively. Dietary supplementation with Arg-HCl or the Arg base [315- and 630-mg Arg/(kg BW d) for 91 d] had no adverse effects on male or female pigs. Similarly, no safety issues were observed for male or female rats receiving supplementation with 1.8- and 3.6-g Arg/(kg BW d) for at least 91 d. Intravenous administration of Arg-HCl to gestating sheep at 81 and 180 mg Arg/(kg BW d) is safe for at least 82 and 40 d, respectively. Animals fed conventional diets can well tolerate large amounts of supplemental Arg [up to 630-mg Arg/(kg BW d) in pigs or 3.6-g Arg/(kg BW d) in rats] for 91 d, which are equivalent to 573-mg Arg/(kg BW d) for humans. Collectively, these results can help guide studies to determine the safety of long-term oral administration of Arg in humans.