The aim of this study is to reveal the relationship between changes in the physical and chemical characterization of eggs during storage and to provide a new way to assess egg freshness at the molecular chemical level. In this study, the Fourier transform infrared (FTIR) spectra of egg albumin from 60 fresh eggs (ISA Brown layer) stored for 1, 10, 20, 30, and 40 days at 4°C and 10°C were measured ( ), and the amide I band of the egg albumin spectra was quantified by Fourier deconvolution and curve fitting to obtain the composition of the protein molecular structure. The results showed that different storage temperatures and storage times led to protein denaturation, resulting in changes in the conformation of the protein secondary structure. With increasing storage temperature and storage time, the content of the ordered structures β-sheet and α-helix in the egg protein secondary structure decreased significantly ( ), and the content of the disordered structure β-turn and random coil increased significantly ( ). Based on the pattern of protein secondary structure changes during storage, it was found that fresh eggs were better stored at 4°C for up to 15 days. Spearman’s correlation analysis of egg protein height, Haugh unit, egg weight, and protein secondary structure in eggs stored at 4°C showed a significant positive correlation between β-sheet and α-helix and egg weight, protein height, and Haugh unit. And a significant negative correlation between random coil and egg weight, protein height, and Haugh unit. Therefore, a curve fitting method based on Fourier transform infrared spectroscopy of deconvoluted spectra is an effective method for evaluating egg quality and freshness.

This study explored the effects of Lactobacillus plantarum on the growth performance, digestibility, serum biochemical indicators, and intestinal health in dual-purpose chickens. A total of 192 one-day-old Xiangdong chickens were selected and randomly divided into four groups: the basal diet group (C1), the semi-wet feed group (T1), the fermented feed group (T2), the postbiotics group (T3), with six replicates per group and 8 chickens per replicate. The experiment lasted 42 days. The results show that, compared with the control group, the growth performance of the experimental groups was significantly increased, among which the postbiotics (T3) group had the best growth performance: the final body weight (FW) and average daily gain (ADG) were significantly increased (P < 0.05), and the average daily feed intake (ADFI) and feed conversion ratio (FCR) were significantly decreased (P < 0.05). The apparent digestibility of the experimental groups was significantly increased. The levels of aspartate aminotransferase (AST), creatinine (CRE), and low-density lipoprotein (LDL) in the serum of group T2 increased. The levels of serum albumin (ALB), AST, glucose (GLU), high-density lipoprotein (HDL), LDL, triglycerides (TG), and total protein (TP) in postbiotics group (T3) decreased, and the level of HDL/LDL ratio increased (P < 0.05). Compared to the control group, the intestinal morphology of the experimental groups was all improved. And the relative abundance of Firmicutes in the caecal chyme of chickens in groups T1, T2, and T3 increased (P < 0.05), while the relative abundance of Bacteroidetes decreased (P < 0.05). These results indicate that adding L. plantarum postbiotics to the diet can enhance the growth performance of Xiangdong chickens, promote the absorption of nutrients, improve serum biochemical indicators, improve intestinal morphology, alter the structure of the caecal microbiota, increase the relative abundance of dominant bacteria. The postbiotics have a greater effect than feed fermented by L. plantarum.

GPX2 has been recognized as a potential candidate gene for feed efficiency in pigs. This article aimed to elucidate polymorphism of GPX2 associated with feed efficiency and its related molecular mechanism. In this study, seven single nucleotide polymorphisms (SNP) of GPX2 were found among 383 Duroc pigs. In addition, seven SNPs and ALGA0043483 (PorcineSNP60 BeadChip data in 600 Duroc pigs), which are near the GPX2 gene, were identified in one haplotypes block. Furthermore, associated studies showed that the genotype of GPX2 has significant association with weaning weight and 100 kg BF in Duroc pigs. In addition, the AG had no effect when the backfat became thinner, and the FCR and RFI traits had a tendency to decrease in the G3 + TT combination genotype, accompanied by an increase of GPX2 expression in backfat and muscle tissues. At the cellular level, the adipocyte proliferation and ability of adipogenic differentiation were reduced, and the lipid degradation increased in 3T3-L1 when there was overexpression of GPX2. In contrast, overexpression of the GPX2 gene can promote the muscle cell proliferation and myogenic differentiation in C2C12 cells. In other words, GPX2 has the effect of reducing fat deposition and promoting muscle development, and it is a candidate gene for backfat and feed efficiency.

Guanidinoacetic acid (GAA) is a direct precursor for creatine synthesis in animals. Because of its great biological value and chemical stability, it can be used as a feed ingredient. The aim of this study was to investigate the effects of GAA on the growth performance, serum biochemical indices and metabolites, intestinal morphology, and intestinal flora of Cherry Valley broiler ducks. The growth performance of broiler ducks in the treatment group was significantly higher than that in the control group. Alanine aminotransferase and total protein were significantly lower in the treatment group than in the control group, while high-density lipoprotein and immunoglobulin A were significantly higher in the treatment group than in the control group. The gut microbial community richness was higher in the treatment group. There were 149 metabolites found in all. The most important pathways through which GAA influences the serum of broiler ducks are fatty acid degradation, Cushing syndrome, fat digestion and absorption, cortisol synthesis and secretion, lipid accumulation and atherosclerosis, alpha-linolenic acid metabolism, and the folate biosynthesis metabolic pathway, according to an enrichment analysis of metabolic pathways. Spearman's correlation analysis showed that microorganisms were closely associated with metabolites. In summary, adding GAA to the diet of Cherry Valley broiler ducks can enhance their growth performance, improve intestinal villi formation, improve digestion and absorption, boost immunoglobulin secretion, and improve immune function. It also optimises lipid metabolism and reduces the burden on the liver, promoting efficient energy utilisation and anti-inflammatory and antioxidant properties. Additionally, GAA alters the blood metabolites and cecal flora of Cherry Valley broiler ducks.