Exogenous insulin-like growth factor-I increases weight gain in intrauterine growth-retarded neonatal pigs

Branched-chain amino acid supplementation does not enhance lean tissue accretion in low birth weight neonatal pigs, despite lower Sestrin2 expression in skeletal muscle

Postnatal muscle growth is impaired in low birth weight (L) neonatal pigs. Leucine supplementation has been established as a dietary intervention to enhance muscle growth in growing animals. The aim of this study was to investigate the efficacy of supplementing L neonatal pig formulas with branched-chain amino acids (B) to enhance the rate of protein accretion. Twenty-four 3-day old pigs were divided into two groups low (L) and normal birth weight (N) based on weight at birth. Pigs were assigned to a control (C) or 1% branched-chain amino acids (B) formulas, and fed at 250 mL·kg body weight -1·d-1 for 28 d. Body weight of pigs in the L group was less than those in the N group (P < 0.01). However, fractional body weight was greater for L pigs compared with their N siblings from day 24 to 28 of feeding regardless of formula (P < 0.01). In addition, feed efficiency (P < 0.0001) and efficiently of protein accretion (P < 0.0001) were greater for L than N pigs regardless of supplementation. Pigs fed the B formula had greater plasma leucine, isoleucine, and valine concentrations compared with those fed the C formula (P < 0.05). Longissimus dorsi Sestrin2 protein expression was less for pigs in the L group compared with those in the N group (P < 0.01), but did not result in a corresponding increase in translation initiation signaling. Longissimus dorsi mRNA expression of BCAT2 was less for LB pigs compared with those in the LC group, and was intermediate for NC and NB pigs (P < 0.05). Hepatic mRNA expression of BCKDHA was greater for pigs in the L compared with those in the N groups (P < 0.05). However, plasma branched-chain keto-acid concentration was reduced for C compared with those in the B group (P < 0.05). These data suggest that branched-chain amino acid supplementation does not improve lean tissue accretion of low and normal birth weight pigs, despite a reduction in Sestrin2 expression in skeletal muscle of low birth weight pigs. The modest improvement in fractional growth rate of low birth weight pigs compared with their normal birth weight siblings was likely due to a more efficient dietary protein utilization.

Zinc Oxide Nanoparticle Improves the Intestinal Function of Intrauterine Growth Retardation Finishing Pigs via Regulating Intestinal Morphology, Inflammation, Antioxidant Status and Autophagy

This study was to investigate effects of zinc oxide nanoparticle (Nano-ZnO) on growth, immunity, intestinal morphology and function of intrauterine growth retardation (IUGR) finishing pigs. Six normal birth weight (NBW) and 12 IUGR male piglets were obtained and weaned at 21 d. NBW-weaned piglets fed basal diets (NBW group), IUGR-weaned piglets allocated to two groups fed basal diets (IUGR group) and basal diets further supplemented 600 mg Zn/kg from Nano-ZnO (IUGR+Zn group), respectively. All pigs were slaughtered at 163 d. Results showed: (1) IUGR pigs showed no difference in body weight at 77d and 163d (P &gt; 0.05), while had increased villus height (VH) and villus surface area in jejunum (P &lt; 0.05) and enhanced interleukin-6, TNF-α and NF-κB mRNA expression (P &lt; 0.05) as compared to NBW group; Compared with IUGR group, dietary Nano-ZnO did not affect the body weight (P &gt; 0.05), but increased VH to crypt depth ratio and IgA concentration (P &lt; 0.05) and decreased TNF-α and NF-κB mRNA expression in jejunum (P &lt; 0.05). (2) IUGR increased the number of swollen mitochondria and autolysosomes, and protein expressions of sequestosome-1 (P62) and microtubule-associated protein light chain 3 B/A (LC3B/A) in jejunum as compared to NBW group (P &lt; 0.05); Compared with IUGR group, Nano-ZnO decreased the number of swollen mitochondria and autolysosomes, and P62 and LC3B/A protein expression (P &lt; 0.05). (3) IUGR increased mucosal contents of malondialdehyde and protein carbonyl (PC) and Keap1 protein expression (P &lt; 0.05) as compared to NBW group; Compared with IUGR group, dietary Nano-ZnO increased activities of total antioxidant capacity, catalase, glutathione peroxidase, and glutathione content (P &lt; 0.05), and enhanced nuclear respiratory factor 2 (Nrf2), glutamate-cysteine ligase modifier subunit and glutathione peroxidase 1 mRNA expression, and increased total and nuclear Nrf2 protein expression (P &lt; 0.05), and decreased malondialdehyde and PC content, and Keap1 protein expression (P &lt; 0.05) in jejunum. Results suggested that IUGR pigs showed postnatal catch-up growth and improved intestinal morphology, and dietary Nano-ZnO may further improve intestinal morphology, reduce inflammation, decrease autophagy and alleviate oxidative stress via Nrf2/Keap1 pathway in jejunum of IUGR pigs.

Compensatory feeding during early gestation for sows with a high weight loss after a summer lactation increased piglet birth weight but reduced litter size

Sows mated in summer produce a greater proportion of born-light piglets (<1.1 kg) which contributes to increased carcass fatness in the progeny population. The reasons for the low birth weight of these piglets remain unclear, and there have been few successful mitigation strategies identified. We hypothesized that: 1) the low birth weight of progeny born to sows mated in summer may be associated with weight loss during the previous summer lactation; and 2) increasing early gestation feed allowance for the sows with high lactational weight loss in summer can help weight recovery and improve progeny birth weight. Sows were classified as having either low (av. 1%) or high (av. 7%) lactational weight loss in their summer lactation. All the sows with low lactational weight loss (LLStd) and half of the sows with high lactational weight loss received a standard gestation feeding regime (HLStd) (2.6 kg/d; day 0-30 gestation), whereas the rest of the sows with high lactational weight loss received a compensatory feed allowance (HLComp) (3.5 kg/d; day 0-30 gestation). A comparison of LLStd (n = 75) versus HLStd sows (n = 78) showed that this magnitude of weight loss over summer lactation did not affect the average piglet or litter birth weight, but such results may be influenced by the higher litter size (P = 0.030) observed in LLStd sows. A comparison of HLStd versus HLComp (n = 81) sows showed that the compensatory feeding increased (P = 0.021) weight gain of gestating sows by 6 kg, increased (P = 0.009) average piglet birth weight by 0.12 kg, tended to reduce (P = 0.054) the percentage of born-light piglets from 23.5% to 17.1% but reduced the litter size by 1.4 (P = 0.014). A subgroup of progeny stratified as born-light (0.8-1.1 kg) or -normal (1.3-1.7 kg) from each sow treatment were monitored for growth performance from weaning until 100 kg weight. The growth performance and carcass backfat of progeny were not affected by sow treatments. Born-light progeny had lower feed intake, lower growth rate, higher G:F, and higher carcass backfat than born-normal progeny (all P < 0.05). In summary, compensatory feeding from day 0 to 30 gestation in the sows with high weight loss during summer lactation reduced the percentage of born-light progeny at the cost of a lower litter size, which should improve growth rate and carcass leanness in the progeny population born to sows with high lactational weight loss.

The Potential for Sialic Acid and Sialylated Glycoconjugates as Feed Additives to Enhance Pig Health and Production

Simple Summary

This review discusses the current challenges in the pig industry and the potential nutritional significance of sialic acid (Sia) and glycoconjugates (Sia-GC’s) for pig health and nutrition. Sia is a nine-carbon acidic sugar which is present in various organs and body fluids of humans and animals. Sias contribute to many beneficial biological functions including pathogen resistance, immunomodulation, gut microbiota development, gut maturation, anti-inflammation and neurodevelopment. The role of Sias in regulating the metabolism of pigs has seldom been reported. However, we have documented significant beneficial effects of specific Sia-GC’s on health and production performance of sows and piglets. These findings are reviewed in relation to other studies while noting the beneficial effects of the inclusion of Sia, Sia containing oligosaccharide or the sialo-protein lactoferrin in the diets of gilts and sows. The importance of the passive transfer of of Sia and Sia-GC’s through milk to the young and the implications for their growth and development is also reviewed. This information will assist in optimizing the composition of sow/gilt milk replacers designed to increases the survival of IUGR piglets or piglets with dams suffering from agalactia, a common problem in pig production systems worldwide.

Abstract

Swine are one of the most important agricultural species for human food production. Given the significant disease challenges confronting commercial pig farming systems, introduction of a new feed additive that can enhance animal performance by improving growth and immune status represents a major opportunity. One such candidate is sialic acid (Sia), a diverse family of nine-carbon acidic sugar, present in various organs and body fluid, as well as an essential structural and functional constituent of brain ganglioside of humans and animals. Sias are key monosaccharide and biomarker of sialylated milk oligosaccharide (Sia-MOS’s), sialylated glycoproteins and glycolipids in milk and all vertebrate cells. Sias accomplish many critical endogenous functions by virtue of their physiochemical properties and via recognition by intrinsic receptors. Human milk sialylated glycoconjugates (Sia-GC’s) are bioactive compounds known to act as prebiotics that promote gut microbiota development, gut maturation, pathogen resistance, immunomodulation, anti-inflammation and neurodevelopment. However, the importance of Sia in pig health, especially in the growth, development, immunity of developing piglet and in pig production remains unknown. This review aims to critically discuss the current status of knowledge of the biology and nutritional role of Sia and Sia-GC’s on health of both female sow and newborn piglets.

Effects of duration of betaine supplementation on growth performance and blood IGF-1 in light- and normal-weight weaner pigs under commercial conditions

Context Betaine supplementation has been reported to increase insulin-like growth factor 1 (IGF-1) in pigs. Betaine is not generally added to weaner pig diets due to a lack of knowledge on the duration of supplementation and effect on targeted bodyweight class. Light-weight weaners, known for their inferior growth performance, may benefit from betaine supplementation during the early days post-weaning. Aims This experiment aimed to identify the timing of betaine supplementation over the weaner phase (early (0–7 days) or late (7–35 days) post-weaning periods) and targeted weaning weight class (light vs normal). Methods The experiment followed a 2 × 2 × 2 factorial arrangement for studying the effects of 0.1% betaine supplementation during early (0–7 days post-weaning) and late (7–35 days post-weaning) weaner phase in light-weight and normal-weight weaners. One hundred and forty-four pens (18 pigs/pen) of weaned pigs (26 days age) were allocated into a 2 × 2 × 2 factorial arrangement on the basis of weaning weight class ((light (3.6 ± 0.75 kg, mean ± s.d.) vs normal (6.6 ± 0.84 kg, mean ± s.d.)), early weaner phase diet (control vs 0.1% betaine) and late weaner phase diet (control vs 0.1% betaine). Basal diets contained sufficient methionine and choline as per industry practice. Growth performance during early, late and whole weaner phase were recorded. Blood IGF-1 was measured at 7 days and 35 days post-weaning. Key results Supplementing 0.1% betaine during the early weaner phase reduced (P &lt; 0.05) growth rate over the early post-weaning period (0–7 days) in both light- and normal-weight weaners, although blood IGF-1 concentration (7 days post-weaning) was not affected. Betaine supplementation during early or late weaner phase did not affect growth performance over the late weaner phase (7–35 days), whole weaner phase (0–35 days) or blood IGF-1 concentration (35 days) of light- or normal-weight weaners. Light-weight weaners had a lower feed intake, and a lower average daily gain than did the normal-weight weaners during the early, late and whole post-weaning periods (all P &lt; 0.01). Conclusions Light-weight weaners had inferior production performance during the weaner phase, which was not improved by betaine supplementation. Implications Betaine supplementation is not recommended in the weaner phase when other dietary methyl donors are sufficient.

The Greater Proportion of Born-Light Progeny from Sows Mated in Summer Contributes to Increased Carcass Fatness Observed in Spring

Simple Summary

Pig producers are required to supply consistent lean carcasses to the market. However, the pig production cycle contains seasonal variation in carcass fatness, such that pigs finished in spring have a greater carcass backfat thickness than those finished in summer. Our experiment showed that when sows were mated in summer they had an increased incidence of born-light progeny (≤1.1 kg), which when finished in spring, had increased fatness. This finding provides a novel explanation for the seasonal variation of carcass fatness and sets a research direction for future mitigation strategies.

Abstract

The backfat of pig carcasses is greater in spring than summer in Australia. The unexplained seasonal variation in carcass backfat creates complications for pig producers in supplying consistent lean carcasses. As a novel explanation, we hypothesised that the increased carcass fatness in spring was due to a greater percentage of born-light progeny from sows that were mated in summer and experienced hot conditions during early gestation. The first part of our experiment compared the birth weight of piglets born to the sows mated in summer (February, the Southern Hemisphere) with those born to sows mated in autumn (May; the Southern Hemisphere), and the second part of the experiment compared the growth performance and carcass fatness of the progeny that were stratified as born-light (0.7–1.1 kg) and born-normal (1.3–1.7 kg) from the sows mated in these two seasons. The results showed that the sows mated in summer experienced hotter conditions during early gestation as evidenced by an increased respiration rate and rectal temperature, compared with those mated in autumn. The sows mated in summer had a greater proportion of piglets that were born ≤1.1 kg (24.2% vs. 15.8%, p < 0.001), lower average piglet birth weight (1.39 kg vs. 1.52 kg, p < 0.001), lower total litter weights (18.9 kg vs. 19.5 kg, p = 0.044) and lower average placental weight (0.26 vs. 0.31 kg, p = 0.011) than those mated in autumn, although litter sizes were similar. Feed intake and growth rate of progeny from 14 weeks of age to slaughter (101 kg live weight) were greater for the born-normal than born-light pigs within the progeny from sows mated in autumn, but there was no difference between the born-light and normal progeny from sows mated in summer, as evidenced by the interaction between piglet birth weight and sow mating season (Both p < 0.05). Only the born-light piglets from the sows mated in summer had a greater backfat thickness and loin fat% than the progeny from the sows mated in autumn, as evidenced by a trend of interaction between piglet birth weight and sow mating season (Both p < 0.10). In conclusion, the increased proportion of born-light piglets (0.7–1.1 kg range) from the sows mated in summer contributed to the increased carcass fatness observed in spring.

Dietary lactoferrin supplementation to gilts during gestation and lactation improves pig production and immunity

Lactoferrin (LF), a sialylated iron-binding glycoprotein, performs multiple beneficial functions including modulating immunity and improves neurodevelopment, health and growth performance. Maternal LF intervention for gilts (first parity sows) on the performance of gilts and their offspring remains unknown. In the current study gilts were fed with a commercial pig feed supplemented with 1g LF /day (treatment group) or 1g milk casein/day (control group) from day 1 post mating throughout pregnancy and lactation for about 135 days. The milk production and body weight gain was monitored. The immunoglobulin concentrations in the serum of gilts and piglets were measured using ELISA. Our study showed that maternal LF supplementation to the gilt (1) significantly increased milk production at different time points (day 1, 3, 7 and 19) of lactation compared to the control (p<0.001); (2) significantly increased body weight gain of their piglets during the first 19 days of life compared to the control group (p<0.05); (3) tended to increase pregnancy rate, litter size and birth weight, number of piglets born alive, and decrease the number of dead and intrauterine growth restriction (IUGR) piglets; (4) significantly increased the concentration of serum IgA in gilt and serum sIgA in piglet (p<0.05). In summary, maternal Lf intervention in gilts can improve milk production, pig production and serum IgA and sIgA levels, and therefore plays a key role in shaping the performance of their progeny.

PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Roles for insulin-supported skeletal muscle growth

Basic principles governing skeletal muscle growth and development, from a cellular point of view, have been realized for several decades. Skeletal muscle is marked by the capacity for rapid hypertrophy and increases in protein content. Ultimately, skeletal muscle growth is controlled by 2 basic means: 1) myonuclear accumulation stemming from satellite cell (myoblast) proliferation and 2) the balance of protein synthesis and degradation. Each process underlies the rapid changes in lean tissue accretion evident during fetal and neonatal growth and is particularly sensitive to nutritional manipulation. Although multiple signals converge to alter skeletal muscle mass, postprandial changes in the anabolic hormone insulin link feed intake with enhanced rates of protein synthesis in the neonate. Indeed, a consequence of insulin-deficient states such as malnutrition is reduced myoblast activity and a net loss of body protein. A well-characterized mechanism mediating the anabolic effect of insulin involves the phosphatidylinositol 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) signaling pathway. Activation of mTOR leads to translation initiation control via the phosphorylation of downstream targets. Modulation of this pathway by insulin, as well as by other hormones and nutrients, accounts for enhanced protein synthesis leading to efficient lean tissue accretion and rapid skeletal muscle gain in the growing animal. Dysfunctional insulin activity during fetal and neonatal stages likely alters growth through cellular and protein synthetic capacities.

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.

Nutritional interventions to prevent and rear low-birthweight piglets

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

Characterizing growth and carcass composition differences in pigs with varying weaning weights and postweaning performance

The unprecedented increase in litter size over the last decade has led to a perceived increase in the number of fallback pigs (Sus scrofa). However, there is little peer-reviewed data available regarding the biological differences between fallback pigs and their normal cohorts. Therefore, the objective of this experiment was to identify differences in the biology and physiology, and thus the growth and metabolism, between pigs with varying weaning weights (WW) and postweaning performance. To accomplish this objective, a total of 120 barrows (PIC C22/C29 × 337) were used in growth and comparative slaughter experiments. Pigs were selected from a population of 960 weanling pigs to represent the 10% lightest, median, and heaviest pigs at weaning (n = 40 pigs per WW category). Eight pigs from each WW category were harvested on d 5 postweaning as the initial slaughter group (ISG). The remaining 96 barrows were housed in individual crates, fed ad libitum quantities of a common diet during a 27-d growth study, and were harvested on d 33 or 34 postweaning. After the completion of the live animal component of the experiment, pigs within each WW category were further stratified into the slowest, median, or fastest 33% ADG categories. This resulted in a total of 9 treatments in a nested design. Fallback pigs were designated as those belonging to the slowest ADG category from either the lightest or median WW categories. Data were analyzed using the GLIMMIX procedure of SAS with the fixed effects of WW category and WW(ADG). Although feed intake was maximized (P < 0.0001) by WW(ADG) category, feed efficiency was not different (P = 0.30). When equalized per unit of BW, WW(ADG) category greatly affected (P < 0.02) eviscerated carcass, organ, and metabolic BW, but not (P = 0.28) empty BW. There were no differences (P > 0.12) in tissue nutrient concentrations, ratios, or energy content among pigs in the growth experiment. All tissue deposition rates, which were calculated as the difference between tissue nutrient concentrations of the growth experiment and initial slaughter groups, were maximized (P < 0.0002) by WW(ADG), even when equalized per unit of BW. In conclusion, WW and ADG affect tissue accretion rates, but not feed efficiency or carcass composition in nursery pigs.

Maturation of digestive function is retarded and plasma antioxidant capacity lowered in fully weaned low birth weight piglets

The digestive function of low birth weight (LBW) pigs post-weaning has been poorly studied. Therefore, newborns from eleven hyperprolific sows were weighed, weaned at 27·2 d and fed a starter diet until sampling. Sampling was done between 18 and 28 d post-weaning. An LBW piglet (n 19) was defined as a piglet having a birth weight less than 1 kg and less than the lower quartile of litter birth weights. Normal birth weight (NBW) piglets (n 13) were having a birth weight close to the mean litter birth weight. For each piglet, eighty-eight variables were determined. Data were analysed with linear models with type of piglet and litter as predictors. A principal component analysis was performed to determine the most important discriminating variables. In the LBW pig, the development of the digestive tract post-weaning was delayed: lower small-intestinal weight:length ratio due to a thinner tela submucosa and tunica muscularis and a higher secretory capacity, both in the distal jejunum. These observations might be a consequence of lower circulating insulin-like growth factor-1 (IGF-1) concentrations (126 (se 10·0) v. 158 (se 12·0) ng/ml for LBW and NBW, respectively) and a lower density of IGF-1 receptors in the proximal small intestine. Additionally, the plasma antioxidant capacity was lower for the LBW pig. Taken together, in the LBW piglet, the normal gut maturation post-weaning was retarded and this did not seem to be related to the weaning transition as such.

Impact of intrauterine growth retardation and early protein intake on growth, adipose tissue, and the insulin-like growth factor system in piglets

Small birth weight and excess of early protein intake are suspected to enhance later adiposity. The present study was undertaken to determine the impact of diets differing in protein content on short-term growth, adipose tissue development, and the insulin-like growth factor (IGF) system in piglets. Normal (NW) and small (SW) birth weight piglets were fed milk-replacers formulated to provide an adequate (AP) or a high protein (HP) supply between 7 and 28 d of age. The fractional growth rate was higher (p < 0.01) in SW than in NW piglets. At 7 d of age, the lower (p < 0.05) weight of perirenal adipose tissue relative to body mass in SW than in NW piglets did not involve significant changes in plasma IGF-I, leptin, or insulin-like growth factor binding protein levels, but involved differences (p < 0.05) in the expression of IGF-I and leptin in adipose tissue. Growth rates did not differ between AP and HP piglets. At 28 d of age, HP piglets had lower (p < 0.001) relative perirenal adipose tissue weight but did not differ clearly from AP piglets with regard to the IGF system. It remains to be determined whether piglets fed such a high protein intake will stay subsequently with a low adiposity.

Intrauterine growth restriction affects the proteomes of the small intestine, liver, and skeletal muscle in newborn pigs

Efficiency of nutrient utilization is high in neonates with normal birth weights but is reduced in those with intrauterine growth restriction (IUGR). However, the underlying mechanisms are largely unknown. This study was conducted with the piglet model and proteomics technology to test the hypothesis that IUGR affects expression of key proteins that regulate growth and development of the small intestine, liver, and muscle, the major organs involved in the digestion, absorption, and metabolism of dietary nutrients. Jejunum, liver, and gastrocnemius muscle were obtained from IUGR and normal birth-weight piglets at birth for analysis of proteomes using the 2-dimensional-PAGE MS technology. The results indicate that IUGR decreased the levels of proteins that regulate immune function (immunoglobulins and annexin A1), oxidative defense (peroxiredoxin 1, transferrin, and zeta-crystallin), intermediary metabolism (creatine kinase, alcohol dehydrogenase, L-lactate dehydrogenase, prostaglandin F synthase, apolipoprotein AI, catecho O-methyltransferase, and phosphoglycerate kinase 1), protein synthesis (eukaryotic translation initiation factor-3), and tissue growth (beta-actin, desmin, and keratin 10) in a tissue-specific manner. In addition, IUGR increased the levels of proteins that are involved in proteolysis (proteasome alpha-5 and alpha-1 subunits), response to oxidative stress (scavenger-receptor protein and alpha-1 acid glycoprotein), and ATP hydrolysis (F1-ATPase). These novel findings suggest that cellular signaling defects, redox imbalance, reduced protein synthesis, and enhanced proteolysis may be the major mechanisms responsible for abnormal absorption and metabolism of nutrients, as well as reduced growth and impaired development of the small intestine, liver, and muscle in IUGR neonates.

Insulin-like growth factor-I and analogues increase growth in artificially-reared neonatal pigs

Exogenous insulin-like growth factor (IGF)-I has been shown to increase growth rate in neonatal pigs while an analogue of IGF-I, long arginine (LR3) IGF-I, has been shown to be more potent than IGF-I in the rat. Therefore, two studies were conducted to determine whether IGF-I and LR3IGF-I increase growth in the artificially-reared neonatal pig. Expt 1 involved forty-two (2 kg initial weight) pigs infused with either control, IGF-I (2, 4 or 8 μg/h) or LR3IGF-I (2, 4 or 8 μg/h) infusions for 8 d. Pigs were weighed and then offered 1·7 MJ (gross energy) milk replacer/kg0·75 per d. Expt 2 involved eighteen pigs (2 kg initial weight) treated with control saline, IGF-I (8 μg/h) or LR3IGF-I (8 μg/h) infusions. After 9 d an additional pump was inserted to increase the infusion rates of each of the growth factors (16 μg/h) for a further 9 d. Cows' milk was provided ad libitum. In Expt 1 there was no overall effect of growth factors on daily weight gain or slaughter weight. However, milk intake was greater in pigs infused with growth factors (909 v. 867 g/d, P=0·027), with an apparently greater milk intake by the pigs infused with IGF-I compared with LR3IGF-I (920 v. 898 g/d, P=0·12). Infusion of LR3IGF-I decreased plasma IGF-I concentrations, but had no effect on plasma IGF-II concentrations. In Expt 2, neither IGF-I nor LR3IGF-I infusion had any effect upon daily weight gain over the first 9 d of the study. However, over the second 9 d of the study, daily weight gain was increased in LR3IGF-I-infused pigs (457 v. 386 g/d, P<0·01), but not in pigs infused with IGF-I (413 v. 386 g/d, P=0·15). Milk intake was not different during the first 9 d of the study but was significantly greater in pigs infused with growth factors over the second half of the study (3407 v. 2905 g/d, P<0·01). Plasma IGF-binding protein-3 concentrations were highly correlated (R=0·85) with average daily gain over the 3 d preceding blood sampling. In conclusion, exogenous IGF-I and particularly LR3IGF-I can increase growth rate and milk intake in artificially-reared pigs fed ad libitum but not in limit-fed piglets.

Short- and long-term influence of perinatal dexamethasone treatment on swine growth

The objective was to evaluate the effects of perinatal dexamethasone (Dex) treatment on postnatal growth in pigs. Experiment 1: 42 piglets were assigned according to birth weight and sex to receive either Dex (1 mg/kg body weight) or sterile saline (Control; equivalent volume) i.m. within 1h of birth. Body weights were recorded weekly and at sacrifice (day 18). Birth weights (1.43 +/- 0.05 kg) did not differ between treatment groups (P > 0.19). At day 18, Dex pigs were heavier than Control pigs (5.46 +/- 0.24 and 4.45 +/- 0.26 kg, respectively). Serum IGF-1 was 17.3% higher in Dex pigs (P < 0.04) compared to Controls. For serum GH, there was a treatment x sex interaction (P < 0.04) with GH being 51% lower in Dex males compared to Control males, and no differences in females. Experiment 2: 71 pigs were assigned according to birth weight and sex to receive either Dex (2 mg/kg body weight) or sterile saline (Control; equivalent volume) i.m. within 1 h of birth. Body weights were recorded weekly until weaning (day 21) and then every 14th day until market weight. Birth weights (1.53 +/- 0.03 kg) did not differ (P > 0.35) between treatment groups or sexes. Dexamethasone increased growth from birth to market weight by 4.15%. Carcass weights were not different (P > 0.34) between Dex (89.9 +/- 1.17 kg) and Control pigs (88.6 +/- 1.36 kg). Overall, Dex enhanced growth in pigs from birth to market weight with minimal effects on carcass and meat quality.

Dexamethasone treatment at birth enhances neonatal growth in swine

The objective of the present study was to determine if dexamethasone (Dex; a potent synthetic glucocorticoid) treatment at birth would alter postnatal growth in neonatal pigs. Forty crossbred pigs were injected i.m. with either sterile saline (Cont; n = 10 males and 10 females) or Dex (1 mg/kg; n = 10 males and 10 females) within 1 hr of birth. All pigs remained with their respective dams until 18 d of age. Body weights were recorded weekly and on d 18. On d 17, all pigs were nonsurgically fitted with an indwelling jugular catheter and placed back with the sows. On d 18, all pigs were placed in individual pens for serial blood collection. Birth weights (1.53 +/-.04 kg) did not differ between birth treatments or sex classes (P > 0.70 and 0.89, respectively). A time by treatment effect was detected (P < 0.007) for body weight such that those pigs which received Dex at birth had the greatest body weights during the 18-d period. Average daily gain was increased (P < 0.017) by 12.2% in those pigs which received Dex at birth (.286 +/-.007) as compared to the Cont pigs (.255 +/-.01 kg/d). Serum concentration of IGF-1 was influenced by both treatment (P < 0.0001) and sex class (P < 0.013). In the male pigs, Dex increased (P = 0.0041) serum concentration of IGF-1 by 47% as compared to Cont male pigs, whereas in the females, Dex increased (P < 0.011) serum concentration of IGF-1 by 34% as compared to Cont female pigs. Dex treatment reduced (P < 0.002) serum IGF-2 by 12.8%. Serum concentration of IGFBP-3 was influenced by both birth treatment (P < 0.007) and sex class (P < 0.002) such that Dex treatment increased serum IGFBP-3, and higher concentrations of IGFBP-3 were observed in boars as compared to gilts. These data suggest that the early neonatal period may be an opportune time to alter physiological factors which influence growth in swine.

Fetal therapy with rhIGF-1 in a rabbit model of intrauterine growth retardation

BACKGROUND

Intrauterine growth retardation (IUGR) may, in part, be due to a deficiency of insulin-like growth factor-1 (IGF-1). The objectives of this study were to determine the relationship between fetal serum IGF-1 levels and fetal and placental size in a rabbit model of IUGR and to compare two techniques of selective, exogenous IGF-1 administration (transamniotic and branch uterine arterial catheter infusion) to growth-retarded fetuses in utero.

MATERIALS AND METHODS

Pregnant rabbits (n = 6) had their fetuses harvested near term (31 days) for fetal and placental weighing and serum collection. Growth-retarded fetuses were selectively infused for 7 days with recombinant human IGF-1 (rhIGF-1; 1,440 ng/day) either through a transamniotic catheter (n = 8) or via an adjacent uterine arterial branch catheter (n = 6). Opposite horn runts were sham catheterized, but not infused. At term, the fetal runt pairs and their placentas were harvested and weighed, and their serum was collected. The correlation between fetal and placental weight and endogenous serum IGF-1 was calculated (Pearson coefficient, r), while paired t-tests were used to compare the means between the IGF-1-infused and control groups.

RESULTS

There was a significant correlation between fetal (r = 0.4230; P = 0.022) and placental weight (r = 0.4166; P = 0.025) and endogenous serum levels of IGF-1. Transamniotic infusion of rhIGF-1 was associated with an increase in serum IGF-1 level (254 +/- 79 vs 351 +/- 101 ng/ml, P = 0.04) and placental weight (5.4 +/- 2.3 vs 7.1 +/- 3.2 g, P = 0.005), and with a trend toward increased fetal weight between matched fetal runt pairs. Fetal mortality in the uterine arterial catheterized group was 76%, and there was no significant difference in fetal or placental weight or IGF-1 levels between infused and noninfused survivors.

CONCLUSIONS

Endogenous fetal serum levels correlate with fetal and placental size in the rabbit IUGR model. Transamniotic administration of rhIGF-1 significantly increases serum IGF-1 levels and placental weight of fetal runts, while uterine vessel catheterization results in prohibitive fetal mortality and does not increase fetal or placental growth or IGF-1 levels.

Moderate doses of porcine somatotropin do not increase plasma insulin-like growth factor-I (IGF-I) or IGF binding protein-3

The growth rate of the young pig is generally much less than its potential and may be constrained by endocrine status as well as by nutrient intake. The aim of this study was to determine whether porcine somatotropin (pST) could increase growth in the nursing pig. Fourteen sows nursing litters of 6 (n = 7) or 12 (n = 7) piglets were utilized to establish a high and low plane of nutrition for sucking pigs. On Day 4 of lactation, the median two male pigs from each litter were randomly allocated to one of two doses of pST (0 or 60 micrograms/kg/d) until weaning on Day 31. Pigs were bled on Days 4, 13, 22, and 31 of lactation and the plasma was analyzed for insulin-like growth factor (IGF)-I, IGF-II, and IGF binding protein-3 (IGFBP-3). Pigs were weaned into conventional accommodation and further weighed on Days 63, 91, and 119. Pigs from litters of 6 grew more quickly and weighed 2.2 kg (P = 0.01) and 3.5 kg (P = 0.04) more than pigs from litters of 12 at 31 and 63 d of age, respectively. There was no effect of pST on preweaning growth of sucking pigs (261 vs. 258 g/d, P = 0.68), although growth rate increased in the final 3 d before weaning at 31 d (241 vs. 294 g/d, P = 0.01). IGFBP-3 was greater (1.09 vs. 0.78 micrograms/ml, P < 0.001), whereas IGF-I tended to be greater (206 vs. 176 ng/ml, P = 0.14), in pigs from the small litters. There was no effect of pST on plasma IGF-I (182 vs. 195 ng/ml, P = 0.454) or IGFBP-3 (0.93 vs. 0.94 microgram/ml, P = 0.85) concentrations. Plasma IGF-I and IGFBP-3 were highly correlated with the growth rate of nursing pigs (R = 0.638 and 0.756, respectively). There were no effects of pST (340 vs. 328 ng/ml, P = 0.48) or litter size (336 vs. 333 ng/ml, P = 0.88) on IGF-II. In conclusion, pST had no little or no effect on growth performance or plasma IGF-I, IGF-II, or IGFBP-3 in sucking pigs on either a high or low plane of nutrition.

Redefining body composition: nutrients hormones, and genes in meat production

Growth rate and body composition of livestock can be optimized to meet consumer needs for a leaner product and to improve the efficiency of meat-animal production. Optimization strategies have traditionally focused on genetic selection and cost-effective ration formulation to achieve the genetic potential. Advances in understanding the mechanisms of growth and its control have led to additional opportunities for its manipulation. These include nutritional manipulation,the use of growth promotants, and, more recently, the ability to change the genetic potential through genetic engineering. Selection of appropriate candidate genes for manipulation depends on understanding the mechanisms underlying differentiation and growth of embryonic muscle cells. Recent advances in genetic engineering techniques, including gene therapy and germline transgenesis, will likely hasten the genetic progress toward a leaner carcass in domestic livestock. Such strategies may prove to be more beneficial then the controlled enhancement of somatotropin expression.