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ABSTRACT. The IGF-1 gene has been implicated as a candidate gene for the regulation of pig growth traits. We analyzed exons 3 and 4 of IGF-1 gene polymorphisms of the Banna mini-pig (28), the Tibetan mini-pig (30), the Junmu pig (55), and L. Yorkshire species (50) using PCR-SSCP. Three genotypes in exon 3 and 6 genotypes in exon 4 were observed, among which, one single nucleotide polymorphism, G201A, on exon 3 and two single nucleotide polymorphisms, A440G and T455C, on exon 4 were found. Statistical analysis of genotype frequencies revealed that the A allele was dominant in the large pig at the G201A locus (PIC = 0.20-0.34), and the AT alleles were dominant in the large pig at the A440G and T455C loci (PIC = 0.30-0.60). The genotype distribution between the various groups was significantly different (P < 0.01), with the highest heterozygosity seen in Junmu pigs at 0.223 and the lowest seen in L. Yorkshire at 0.098. The genetic distance of the Junmu pig from the L. Yorkshire is the smallest, the distance from the Tibetan miniature pigs is larger, and the distance from the Banna minipig is the largest. The IGF-1 gene polymorphism and heterozygosity results from various pig breeds indicate that IGF-1 is substantially polymorphic with significant difference of the polymorphic distribution and expression levels among various pig breeds. This information provides a theoretical basis for the genetic background of miniature pigs but also provides means to breed improved pig varieties.

Background: The declines in both laying performance and egg shell quality during late production period have adverse effects on long production cycle. Improving nutrition of laying hens is a crucial measure to reverse the declination. Selenium (Se) plays important roles in antioxidant defense, redox balance, immune response, and modulation of gut microbiota. However, the mechanism underlying selenium yeast regulating the interaction between transcriptome and gut microbiota to influence laying performance, is still unclear. Here, we use the transcriptome and 16S rRNA analysis to investigate how selenium yeast alters the gene expression and microbiota composition of ileum in aged laying hens.Results: In this study, selenium yeast ameliorated the depression in aged laying performance with a significant increase of laying rate in 0.30 mg/kg group. Furthermore, functional enrichment and STEM analysis were performed using RNA-Seq, which indicated selenium yeast activated metabolic progresses (e.g. Glycerolipid metabolism, Glycerophospholipid metabolism, and fatty acid metabolism), immune response and oxidative stress response. Four hub genes (TXNRD1, DLD, ILK and LZTS2) were involved in intestinal metabolism which was closely associated with Se deposition/status. Additionally, Se increased the abundance of beneficial bacteria including Veillonella, Turicibacter, and Lactobacillus whiledecreasing the abundance of pathogenic bacteria Stenotrophomonas by 16S rRNA-Seq. The Integrated analysis of omics revealed that several microbiotas (Maritalea, Alteromonas, Geobacter, etc.) were positively associated with both Se content and laying rate, and there was a markable correlation between several specific microbiotas (Aliivibrio, Anaerobacillus, Shewanella, etc.) and the immune response pathways (regulation of acute inflammatory response, positive regulation of lymphocyte activation and IFN gamma response). Meanwhile, the “switched on” gene PSCA had a positive relationship with Veillonella, and a negative relationship with the opportunistic pathogens Stenotrophomonas. CCA analysis indicated that both the Se content and the laying rate were highly positively correlated with Anaerobacillus, Alteromonas, Loktanella and the positive regulation of lymphocyte activation, but were negative correlated with Streptococcus, Devosia, Aerococcus, Intestinibacter and fatty acid metabolic progress. Conclusions: Overall, our study provides unprecedented insights showing that selenium yeast supplementation can affect immune response, metabolic processes, and specific microbiota composition to ameliorate the egg production deterioration in aged laying hens.

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Internal egg and eggshell quality are often deteriorated in aging laying hens, which causes huge economic losses in the poultry industry. Selenium yeast (SY), as an organic food additive, is utilized to enhance laying performance and egg quality. To extend the egg production cycle, effects of selenium yeast supplementation on egg quality, plasma antioxidants and selenium deposition in aged laying hens were evaluated. In this study, five hundred and twenty-five 76-week-old Jing Hong laying hens were fed a selenium-deficient (SD) diet for 6 weeks. After Se depletion, the hens were randomly divided into seven treatments, which included an SD diet, and dietary supplementation of SY and sodium selenite (SS) at 0.15, 0.30, and 0.45 mg/kg to investigate the effect on egg quality, plasma antioxidant capacity, and selenium content in reproductive organs. After 12 weeks of feeding, dietary SY supplementation resulted in higher eggshell strength (SY0.45) (p < 0.05) and lower shell translucence. Moreover, organs Se levels and plasma antioxidant capacity (T-AOC, T-SOD, and GSH-Px activity) were significantly higher with Se supplementation (p < 0.05). Transcriptomic analysis identified some key candidate genes including cell migration inducing hyaluronidase 1 (CEMIP), ovalbumin (OVAL), solute carrier family 6 member 17 (SLC6A17), proopiomelanocortin (POMC), and proenkephalin (PENK), and potential molecular processes (eggshell mineralization, ion transport, and eggshell formation) involved in selenium yeast’s effects on eggshell formation. In conclusion, SY has beneficial functions for eggshell and we recommend the supplementation of 0.45 mg/kg SY to alleviate the decrease in eggshell quality in aged laying hens.