R. L. Huang

Impaired translation initiation activation and reduced protein synthesis in weaned piglets fed a low-protein diet.

Weanling mammals (including infants) often experience intestinal dysfunction when fed a high-protein diet. Recent work with the piglet (an animal model for studying human infant nutrition) shows that reducing protein intake can improve gut function during weaning but compromises the provision of essential amino acids (EAA) for muscle growth. The present study was conducted with weaned pigs to test the hypothesis that supplementing deficient EAA (Lys, Met, Thr, Trp, Leu, Ile and Val) to a low-protein diet may maintain the activation of translation initiation factors and adequate protein synthesis in tissues. Pigs were weaned at 21 days of age and fed diets containing 20.7, 16.7 or 12.7% crude protein (CP), with the low-CP diets supplemented with EAA to achieve the levels in the high-CP diet. On Day 14 of the trial, tissue protein synthesis was determined using the phenylalanine flooding dose method. Reducing dietary CP levels decreased protein synthesis in pancreas, liver, kidney and longissimus muscle. A low-CP diet reduced the phosphorylation of eukaryotic initiation factor (eIF) 4E-binding protein-1 (4E-BP1) in skeletal muscle and liver while increasing the formation of an inactive eIF4E.4E-BP1 complex in muscle. Dietary protein deficiency also decreased the phosphorylation of mammalian target of rapamycin (mTOR) and the formation of an active eIF4E.eIF4G complex in liver. These results demonstrate for the first time that chronic feeding of a low-CP diet suppresses protein synthesis in animals partly by inhibiting mTOR signaling. Additionally, our findings indicate that supplementing deficient EAA to low-protein diets is not highly effective in restoring protein synthesis or whole-body growth in piglets. We suggest that conditionally essential amino acids (e.g., glutamine and arginine) may be required to maintain the activation of translation initiation factors and optimal protein synthesis in neonates.

Nutritive value of feedstuffs and diets for pigs: I. Chemical composition, apparent ileal and faecal digestibilities

The chemical composition, including amino acid content, and ileal and faecal digestibility was determined for 39 batches of 38 different feedstuffs and 18 mixed diets. Considerable variation was found in both chemical composition and digestibility among cereals and cereal by-products, legumes, animal protein feedstuffs, oil seed meals, protein and mineral concentrates and mixed diets. Within the different classes of feedstuffs and diets, variation was small for mixed diets and protein and mineral concentrates. A large variation was found for animal protein feedstuffs and oil seed meals, especially for apparent ileal digestibilities of amino acids. However, there was good agreement between the results and those reported in the literature. The digestibilities of nutrients were affected by many factors, including cell wall constituents, the balance of mineral and trace elements and anti-nutritional factors. Faecal digestibility was higher than ileal digestibility. In general, the differences between apparent faecal digestibilities were smaller than for apparent ileal digestibilities. This indicates that the modifying action of microflora in the large intestine is irregular, therefore the digestibility measured at the end of the ileum is more reliable. However, the high ileal digestibility of cell wall constituents indicates that the influence of the microflora begins before the end of the ileum, and other methods such as isotope dilution techniques should be used to more accurately determine digestion and absorption.

Effect of dietary arginine and N-carbamoylglutamate supplementation on reproduction and gene expression of eNOS, VEGFA and PlGF1 in placenta in late pregnancy of sows

The objectives of this study were to investigate the potential mechanisms of dietary arginine (Arg) and N-carbamoylglutamate (NCG) supplementation on reproductive performance of sows. Twenty-seven crossbred (Landrace×Large White) sows with similar body weight and parity at day (90±1) of gestation were assigned randomly into 3 groups (n=9) control group, Arg group, NCG group, and fed with the following diets: a control diet, and the control diet supplemented with 1.0% Arg or 0.1% NCG. Litter size was recorded. Blood samples were obtained for biochemical analyses. Placenta chorioallantoic membrane tissue collected immediately after birth to preserve in RNA stabilizer for mRNA analysis of endothelial nitric oxide synthase (eNOS), endothelial growth factor a (VEGFA) and placenta growth factor 1 (PlGF1) by real time-PCR. The results showed that compared with the control group, the average birth weight of all piglets born alive were 16.2% and 14.3% higher in the Arg and NCG groups (P<0.05), respectively; plasma VEGFA was higher in the Arg group (P<0.05). The expression of VEGFA in the allantochorion tissue of the NCG-supplemented group was higher (P<0.01), and tended to be higher in the Arg-supplemented group (0.05<P<0.1). NCG significantly increased protein concentration of PlGF1 in plasma (P<0.05), and enhanced PlGF1mRNA expression in allantochorion tissue of placenta (P<0.01). The results suggested that dietary Arg and NCG supplementation play important roles in meliorating placental vascular function and promoting the nutrients supply to fetus.

Dietary amylose and amylopectin ratio and resistant starch content affects plasma glucose, lactic acid, hormone levels and protein synthesis in splanchnic tissues.

Experiments were conducted to determine the effects of feeding different starch sources on piglets. Four diets were formulated with maize, brown rice, sticky rice and Hi-Maize 1043 as starch sources, with resistant starch (RS) contents of 2.3%, 0.9%, 0.0%, 20.6%, and amylose and amylopectin ratio of 0.23%, 0.21%, 0.18%, 0.06% respectively. Fifty-six pigs weaned at 28 days of age were randomly assigned to one of the four diets. In Exp. 1, six piglets in each group were fitted with an indwelling jugular catheter. After 25 days of feeding trial, venous blood samples were obtained at time zero and every 1 h for 4 h. In Exp. 2, the remaining piglets were used to determine the effects of different starch sources on the fractional synthesis rate (FSR). The results indicated that feeding the Hi-Maize 1043 diet decreased (p < 0.05) plasma contents of glucose, insulin, lactic acid and T(3), while sticky rice increased plasma contents of glucose and insulin. The insulin contents in piglets fed the sticky rice diet was 69.2 microIU/ml at 1 h post-feeding which was highest among the starch diets. The FSR in the pancreas, spleen, duodenum, jejunum, ileum and colon in the corn group were much higher (p < 0.05) than that in the sticky rice group. These results suggest that RS is potentially beneficial for improving insulin sensitivity in young pigs and that the ratio of amylose and amylopectin have significantly effects on the FSR in splanchnic tissues in weaned piglets. Another finding of this study indicated maize with a ratio of amylose and amylopectin of 0.23 has the best starch sources for pig production.

Dietary starch sources affect net portal appearance of amino acids and glucose in growing pigs

Four male pigs (Duroc × Landrace × Yorkshire; average initial (mean ± SEM) BW = 22.5 ± 1.1 kg), fitted with permanent catheters in the portal vein, ileal vein and carotid artery, were used in a 4 × 4 Latin square experimental design to measure the effect of dietary starch sources on the net portal appearance of glucose and amino acids. Dietary starch sources were resistant starch (RS), maize, sticky rice and brown rice. Diets were provided at 0730, 1530 and 2330 h during a 6-day adjustment period and 1-day collection period. On day 7 of each period, blood samples were collected from the portal vein and carotid artery at 0730 h (prior to feeding) and hourly up to 8 h after meal. Blood samples were used to determine glucose, amino acid, packed cell volume and partial pressure of oxygen (pO2). When calculated per 100 g feed intake, cumulative portal glucose appearance was lower (P < 0.05) for resistant starch than for maize, sticky rice or brown rice up to 8 h after the meal. Cumulative portal glucose appearance was higher (P < 0.05) for sticky rice and brown rice than for other diets until 4 h after the meal, but maize had higher cumulative glucose appearance after 4 h. Net cumulative portal concentrations of most amino acids for resistant starch were also reduced (P < 0.05) than for the other starch sources. Cumulative portal appearance of amino acid represented 48.39%, 63.76%, 61.80% and 59.18% of dietary intake for resistant starch, maize, sticky rice and brown rice, respectively. Collectively, our results indicate that dietary starch sources substantially affect the appearance of amino acids and glucose in the portal circulation.

Apparent digestibilities of energy, cell wall constituents, crude protein and amino acids of Chinese oil seed meals for growing pigs

The apparent ileal and faecal digestibilities of energy, crude protein (CP), amino acid and cell wall constituents in feedstuffs of peanut meal (PNM), soyabean meal (SBM), rapeseed meal (RSM-1), ammoniated rapeseed meal (RSM-2), partly dehulled cotton seed meal (CSM) and rice bran cake (RBC) were determined for non-cannulated pigs (n=6) or pigs (n=6) fitted with ileo-caecal reentrant cannulae. The pigs were fed with a cornstarch-based diet formulated to contain about 14% protein. The results showed that the ileal digestibility of energy was not significantly different between SBM (76.2%) and PNM (74.4%), but that it was significantly lower for RBC (P<0.05) than for SBM and PNM. However, the ileal digestibility of energy was significantly lower for RSM-2, RSM-1 and CSM than for RBC. The ileal digestibility of CP was significantly higher for PNM (87.3%) than for SBM, and was significantly higher for SBM than for RBC (73.4%) and CSM (73.0%). Although the ileal digestibility of CP was significantly higher for RSM-2 than for RSM-1, it was significantly lower for RSM-2 than for CSM and RBC. CSM had the lowest ileal digestibilities of lysine (43%), methionine (64%) and threonine (67%), which are the most important amino acids in amino nutrition. The ileal digestibility of lysine was highest for SBM (P<0.05), but that of methionine was highest (P<0.05) for RSM-2. PNM, SBM and RSM-2 had a similar ileal digestibility of threonine. PNM contained not only the highest amount of arginine (76.6 g kg−1 DM), but also had the highest ileal digestibility of arginine (92%). In general, the faecal analysis method overestimated the digestibility value of nutrients. The modifying action of the bacteria in the large intestine is irregular, therefore a precise determination of the apparent digestibilities of nutrients, especially the amino acids, cannot be obtained from the faecal analysis method. In contrast to previous findings, a high ileal digestibility of cell wall constituents was found for oil seed meal.

Fermentation Characterization of Chinese Yam Polysaccharide and Its Effects on the Gut Microbiota of Rats

Rat was used to characterize Chinese Yam polysaccharides (CYPs). In Exp. 1, maximum volume and rate of gas production in CYP 3-supplemented group were higher than other CYP-supplemented groups and control group, while pH values and NH3 contents in CYP 2-, CYP 3-, and CYP 4-supplemented groups were lower than control group. Contents of acetate, propionate and butyrate increased by supplementing CYP 3 or CYP 4 compared to other groups, except for glucose-supplemented group. Contents of isobutyrate for CYPs groups decreased compared to control group. CYP 3 enhanced beneficial gut microbiota, but suppressed bacterial pathogens. In Exp. 2, contents of acetate and butyrate in cecal digesta of rats fed 0.25 or 0.5 g/kg CYP 3 were higher than other groups on day 7. pH values in 0.25 and 0.5 g/kg groups were lower than 1.0 g/kg group. Contents of acetate in 0.25 and 0.5 g/kg groups were greater than other 2 groups on day 21. Gut microflora in CYP 3-supplemented rats had greater diversity than non-supplemented rats. CYP 3 enriched beneficial gut microbiota, but suppressed bacterial pathogens in rat cecum. These findings suggested that CYP 3 is a good source of carbon and energy, and may improve bacterial community diversity and modulate short-chain fatty acid production in hindgut of rats.

Comparison of ileorectal anastomosis and the conventional method for the measurement of ileal digestibility of protein sources and mixed diets in growing pigs

Apparent digestibility determined by collection of digesta at the terminal ileum has been shown to provide a reliable estimate of amino acid availability in pigs. As a routine technique for collecting ileal digesta, ileorectal anastomosis (IRA) has been proposed. In this trial, twelve Yorkshire × Chinese Black Pigs (45 kg) were used to compare IRA with the ileocaecal re-entrant cannula (IC) method, which was considered as a reference cannula technique. Three complex diets—a soyabean meal diet (SBMD), a rapeseed meal diet (RSMD), a Chinese common commercial diet (CCCD)—and three simple diets—a fish meal (Peru) diet (FM), a raw soyabean diet (RSB) and a single cell protein (SCP) diet—were used. The trial was conducted as a 6 × 6 Latin square design. The results show that, with the exception of the dry matter in SBMD and RSMD, organic matter in SBMD and CCCD, and valine, glutamic acid and analine in CCCD, similar values for dry matter, organic matter, energy, crude protein and amino acid digestibility were obtained in IRA and IC pigs on the six diets. Regression coefficients showed a close relationship between IRA and IC (P < 0.01) of the apparent digestibility of nutrients, except for dry matter, organic matter and serine (P < 0.05). There were no significant differences in growth and development between the IRA and intact pigs. In general, apparent digestibility of nutrients in FM was the highest and the complex diets had a higher digestibility of crude protein and amino acids than RSB and SCP. The digestibility of nutrients was almost equal between RSB and SCP.

Use of the Ussing chamber technique to study nutrient transport by epithelial tissues.

The Ussing chamber provides a physiologically relevant system for measuring the transport of ions, nutrients, and drugs across various epithelial tissues. This article outlines the design, structure, principle, and operation of the Ussing chamber, its application in the field of gastrointestinal barrier function and nutrient transport research, as well as its advantages and limitations. This review serves as a practical guide for investigators who are new to the Ussing chamber and should help researchers better understand this valuable method for measuring the transport of electrolytes, organic nutrients, water, and drugs across the small intestine, placenta, and other epithelial tissues.

Effect of dietary supplementation of galacto-mannan-oligosaccharides and chitosan on performance and serum immune parameters of 28-day weaned piglets challenged with pathogenic E. coli.

Abstract Sun, Z.H., Tang, Z.R., Yin, Y.L., Huang, R.L., Li, T.J., Tang, S.X. and Tan, Z.L. 2009. Effect of dietary supplementation of galacto-mannan-oligosaccharides and chitosan on performance and serum immune parameters of 28-day weaned piglets challenged with pathogenic E. coli. J. Appl. Anim. Res., 36: 207–211. To determine the effects of galacto-mannan-oligosaccharides (GMOS) and chitosan (COS) on growth performance and serum immune parameters 40- 28-d weaned castrated Duroc × Landrace × Yorkshire piglets (8.09 ± 1.87 kg) were challenged with three kinds of pathogenic E. coli (serotype 09, 0141 and 064) and randomly assigned to four treatment groups fed a maize-soybean meal diets containing either no addition (control), 250 mg/kg of lincomycin (LIN), 250 mg/kg of COS (COS) or 2000 mg/kg of GMOS (GMOS), respectively, in α four-week feeding experiment. The feed/gain of control group was poorer than that of other groups with no difference in average daily gain or feed intake. The serum concentrations oflgG, IgA, IgM, IL—6, IL −2 and IL—lβ in experimental groups were higher when compared to control group (P<0.05). The results indicate that GMOS and COS supplemented in weaned piglets diet can improve growth performance and enhance immune function.