The nutritional value of feed proteins and their utilization by livestock are related not only to the chemical composition but also to the structure of feed proteins, but few studies thus far have investigated the relationship between the structure of feed proteins and their solubility as well as digestibility in monogastric animals. To address this question we analyzed soybean meal, fish meal, corn distiller's dried grains with solubles, corn gluten meal, and feather meal by Fourier transform infrared (FTIR) spectroscopy to determine the protein molecular spectral band characteristics for amides I and II as well as α-helices and β-sheets and their ratios. Protein solubility and in vitro digestibility were measured with the Kjeldahl method using 0.2% KOH solution and the pepsin-pancreatin two-step enzymatic method, respectively. We found that all measured spectral band intensities (height and area) of feed proteins were correlated with their the in vitro digestibility and solubility (p≤0.003); moreover, the relatively quantitative amounts of α-helices, random coils, and α-helix to β-sheet ratio in protein secondary structures were positively correlated with protein in vitro digestibility and solubility (p≤0.004). On the other hand, the percentage of β-sheet structures was negatively correlated with protein in vitro digestibility (p<0.001) and solubility (p = 0.002). These results demonstrate that the molecular structure characteristics of feed proteins are closely related to their in vitro digestibility at 28 h and solubility. Furthermore, the α-helix-to-β-sheet ratio can be used to predict the nutritional value of feed proteins.

This study was developed to provide further information on the intestinal barrier permeability and the tight junction protein expression in weaned piglets fed with different levels of soybean agglutinin (SBA). Twenty-five weaned crossbred barrows (Duroc × Landrace × Yorkshire) were selected and randomly allotted to five groups, each group with five replicates. The piglets in the control group were not fed with leguminous products. 0.05, 0.1, 0.15 and 0.2% SBA was added to the control diet to form four experimental diets, respectively. After the experimental period of 7 days (for each group), all the piglets were anesthetized with excess procaine and slaughtered. The D-lactic acid in plasma and the Ileal mucosa diamine oxidase (DAO) was analyzed to observe the change in the intestinal permeability. The tight junction proteins occludin and ZO-1 in the jejunum tissue distribution and relative expression were detected by immunohistochemistry and Western Blot. The results illustrated that a high dose of SBA (0.1–0.2%) could increase the intestinal permeability and reduce piglet intestinal epithelial tight junction protein occludin or ZO-1 expression, while low dose of SBA (0.05% of total diet) had no significant affects. The contents of DAO, D-lactic acid, occludin or ZO-1, had a linear relationship with the SBA levels (0–0.2%) in diets. The high dose SBA (0.1–0.2%) could increase the intestinal permeability and reduce piglet intestinal epithelial tight junction protein occludin or ZO-1 expression, while low dose of SBA (0.05% of total diet) had no affects.

Integrins are an important family of adhesion molecules that were first discovered two decades ago. Integrins are transmembrane heterodimeric glycoprotein receptors consisting of α and β subunits, and are comprised of an extracellular domain, a transmembrane domain, and a cytoplasmic tail. Therein, integrin cytoplasmic domains may associate directly with numerous cytoskeletal proteins and intracellular signaling molecules, which are crucial for modulating fundamental cell processes and functions including cell adhesion, proliferation, migration, and survival. The purpose of this review is to describe the unique structure of each integrin subunit, primary cytoplasmic association proteins, and transduction signaling pathway of integrins, with an emphasis on their biological functions.

Studies on dietary fiber and nutrient bioavailability have gained an increasing interest in both human and animal nutrition. Questions are increasingly being asked regarding the faith of nutrient components such as proteins, minerals, vitamins, and lipids after feed formulation. The aim of this review is to evaluate the evidence with the perspective of fiber usage in feed formulation. The consumption of dietary fiber may affect the absorption of nutrients in different ways. The physicochemical factors of dietary fiber, such as fermentation, bulking ability, binding ability, viscosity and gel formation, water-holding capacity and solubility affect nutrient absorption. The dietary fiber intake influences the different methods in which nutrients are absorbed. The increase in the total fiber content of the diet may delay the glycemic response. Soluble fiber decreased blood glucose content whereas purified insoluble fiber has a little or no effect on the blood glucose levels after a meal. Dietary fiber and prebiotics influence the host animal well-being by regulating blood glucose or insulin levels, stool bulking effects, increasing the acidity of the gut, constructive synthesis of short chain fatty acids (SCFAs), decreasing intestinal transit time, stimulating the growth of intestinal microbes, and increasing blood parameters. Previous studies suggest that fiber affects the bioavailability of nutrients, and maintains the host wellness.

Soybean agglutinin (SBA) is a non-fiber carbohydrate-related protein and the main anti-nutritional factor that exists in soybean or soybean products. SBA possesses a specific binding affinity for N-glyphthalide-d-galactosamine or galactose and has a covalently linked oligosaccharide chain. SBA mediates negative effects on animal intestinal health by influencing the intestinal structure, barrier function, mucosal immune system, and the balance of the intestinal flora. Functional oligosaccharides are non-digestible dietary oligosaccharides that are commonly applied as prebiotics since the biological effects of the functional oligosaccharides are to increase the host health by improving mucosal structure and function, protecting the integrity of the intestinal structure, modulating immunity, and balancing the gastrointestinal microbiota. The purpose of this review is to describe the structure and anti-nutritional functions of SBA, summarize the influence of SBA and functional oligosaccharides on the intestinal tract of monogastric animals, and emphasize the relationship between SBA and oligosaccharides. This review provides perspectives on applying functional oligosaccharides for alleviating the anti-nutritional effects of SBA on the intestinal tract.

The present study was undertaken to evaluate the effects of soybean varieties on content of anti-nutritional factors, growth, and nutrient digestibility in rat. For this purpose, the content of trypsin inhibitor and lectin was firstly measured in five soybean varieties. Then sixty male Wistar rats were randomly divided into six groups and fed on different diets as follows: groups 1 to 5 were fed on treatment diets containing five different varieties of soybean flour; group 6 was fed on a control diet containing casein. All animals were fed for four weeks. During this period, faeces and urine were collected to determine the nutritional efficiency of diets and body weight were measured weekly on ten rats from each group. The results showed that trypsin inhibitor and lectin content of Jilin45 was the highest, and those of Jinong7 were the lowest of the soybean varieties. In comparison, all measured parameters, that is including gain in body weight, feed utilization efficiency, nutrient digestibility, nitrogen balance and nitrogen retention, were markedly different among the five groups of animals, but were significantly lower than the control group. These findings show that soybean varieties could significantly affect trypsin inhibitor and lectin content in soybean.