Association of blood APMAP content and meat quality trait in Rex rabbits

APMAP is single transmembrane arylesterase which plays a cardinal role in adipogenesis. In this experiment, three tissue and blood samples of Rex rabbits at 3 growing periods were selected. The expression levels of APMAP gene in different tissues were detected by real-time fluorescence quantitative PCR and the content of APMAP in the blood was detected by Elisa. The results showed that fat deposition, the expression of APMAP in muscle and the content of APMAP in the blood increased rapidly during the growth of Rex rabbits. The correlation analysis showed that the correlation coefficient between APMAP content in the blood and the expression level of APMAP gene in longissimus lumborum muscle was 0.75(p < 0.05); the correlation coefficients between APMAP content in the blood and intramuscular fat and 24-hour pH were 0.90 (p < 0.01) and 0.75 (p < 0.05), respectively. According to the analysis results, we inferred APMAP content in the blood in Rex rabbits may influence meat quality and the meat quality of high APMAP content in the blood in Rex rabbits is better. These results revealed APMAP content in the blood may be one of the important signs for meat quality traits of molecular markers.

A genome-wide association study of coat color in Chinese Rex rabbits

Coat color is an important phenotypic characteristic of the domestic rabbit (Oryctolagus cuniculus) and has specific economic importance in the Rex rabbit industry. Coat color varies considerably among different populations of rabbits, and several causal genes for this variation have been thoroughly studied. Nevertheless, the candidate genes affecting coat color variation in Chinese Rex rabbits remained to be investigated. In this study, we collected blood samples from 250 Chinese Rex rabbits with six different coat colors. We performed genome sequencing using a restriction site-associated DNA sequencing approach. A total of 91,546 single nucleotide polymorphisms (SNPs), evenly distributed among 21 autosomes, were identified. Genome-wide association studies (GWAS) were performed using a mixed linear model, in which the individual polygenic effect was fitted as a random effect. We detected a total of 24 significant SNPs that were located within a genomic region on chromosome 4 (OCU4). After re-fitting the most significant SNP (OCU4:13,434,448, p = 1.31e-12) as a covariate, another near-significant SNP (OCU4:11,344,946, p = 7.03e-07) was still present. Hence, we conclude that the 2.1-Mb genomic region located between these two significant SNPs is significantly associated with coat color in Chinese Rex rabbits. The well-studied coat-color-associated agouti signaling protein (ASIP) gene is located within this region. Furthermore, low genetic differentiation was also observed among the six coat color varieties. In conclusion, our results confirmed that ASIP is a putative causal gene affecting coat color variation in Chinese Rex rabbits.

subtypes in Rex rabbits in China

Blastocystis sp. is a common protist that colonizes the intestinal tract in both humans and animals worldwide. A total of 666 fecal samples of Rex rabbits were collected from 12 farms in three administrative regions in Henan, China. Blastocystis sp. was screened and subtyped by PCR amplification of the small subunit ribosomal DNA. The results indicated that 31 (4.7%, 31/666) rabbits were positive for Blastocystis sp. across three farms (25.0%, 3/12). The infection rate of Blastocystis sp. in Rex rabbits was highest in Jiyuan at 9.1% (30/331), followed by Luoyang (0.5%, 1/191), with no positive infections found in Zhengzhou. The Blastocystis sp. infection rate in adults (10.2%, 14/287) was higher than that in young rabbits (4.5%, 17/379) (χ² = 0.0027, P > 0.50). Four Blastocystis sp. subtypes (ST1, ST3, ST4, and ST17) were identified in rabbits in the present study. Among them, the subtypes ST1 (n = 15) and ST3 (n = 14) were dominant, followed by ST4 (n = 1) and ST17 (n = 1). Blastocystis sp. ST1 was the dominant subtype in adult rabbits, and ST3 was the dominant subtype in young rabbits. This study enriches the data on the prevalence and subtype distributions of Blastocystis sp. in rabbits. More studies are needed among humans, domestic animals, and wild animals to obtain a better understanding of their role in the spread of Blastocystis sp.

FTO Regulated Intramuscular Fat by Targeting APMAP Gene via an m(6)A-YTHDF2-dependent Manner in Rex Rabbits

N6-methyladenosine (m⁶A) regulates fat development in many ways. Low intramuscular fat (IMF) in rabbit meat seriously affects consumption. In order to improve meat quality, we explored the law of IMF deposition. FTO could increase the expression of APMAP and adipocyte differentiation through methylation. However, interference YTHDF2 can partially recover the influence of interference FTO on the APMAP gene and adipocyte differentiation. APMAP promoted the differentiation of adipocytes. Analysis of IMF and APMAP expression showed IMF content is positive with the expression level of the APMAP gene (p < 0.01). Conclusion: Together, FTO can regulate intramuscular fat by targeting the APMAP gene via an m⁶A-YTHDF2-dependent manner in Rex rabbits. The result provides a theoretical basis for the molecular breeding of rabbits.

N6-Methyladenosine Methylome Profiling of Muscle and Adipose Tissues Reveals Methylase-mRNA Metabolic Regulatory Networks in Fat Deposition of Rex Rabbits

N6-methyladenosine (m6A) is the most prevalent internal form of modification in messenger RNA in higher eukaryotes and plays an important role in cancer, immunity, reproduction, development, and fat deposition. Intramuscular fat is the main factor used to measure the meat quality of an animal. The deposition of intramuscular fat and perirenal fat increases with age. However, there is no data on m6A modification of Rex rabbits and its potential biological roles in adipose deposition and muscle growth. Here, we performed two high-throughput sequencing methods, m6A-modified RNA immunoprecipitation sequence (MeRIP-seq) and RNA sequence (RNA-seq), to identify key genes with m6A modification on fat deposition in the muscle and adipose tissues of Rex rabbits. Then, qRT-PCR was used to identify the differently methylated genes related to fat deposition. Our findings showed that there were 12,876 and 10,973 m6A peaks in the rabbit muscle and adipose tissue transcriptomes, respectively. Stop codons, 3′-untranslated regions, and coding regions were found to be mainly enriched for m6A peaks. In addition, we found 5 differential methylases and 12 key genes of methylation modification related to fat deposition between muscle and adipose tissues samples. The expression levels of six random key genes were significantly higher in the fat than that in the muscle of Rex rabbits at different stages (p < 0.01). Finally, five differential methylases were found to regulate adipogenesis by affecting the expression of screened genes in different ways. These findings provided a theoretical basis for our future research on the function of m6A modification during the growth of fat deposits.

Environmental enrichment changes rabbits' behavior, serum hormone level and further affects cecal microbiota

Many studies have shown that stress is associated with gut microbiota. Environmental enrichment (EE) could reduce stress in farm animals; however, limited information is available on the microbial community composition in rabbits raised with or without EE. This study aimed to identify EE influences on the behavior, serum hormonal levels, and cecal microbiota of rabbits. Two hundred Rex rabbits were segregated randomly within four cohorts (n = 50); reared for 76 d within standardized enclosures (non-enriched) or within cages containing a willow-stick (WS), rubber-duck (RD), or a can of beans (CB). The rabbits' ingestive, rest, locomotion, exploratory, grooming, and abnormal behavior were observed. The serum hormone levels for rabbits were measured, and cecal specimens were sequencedfrom the V3-V4 region using 16S rRNA amplicons. Environmental enrichment increased feeding and drinking time, promoted exploratory behavior, and reduced abnormal behavior in rabbits. Insulin-like growth factor 1(IGF-1) levels of the enriched cohorts were elevated in comparison to the control cohort. Serum cortisol level for CB cohort was markedly reduced in comparison to the control cohort (p < 0.05), while dopamine levels for CB cohort peaked. Further, we found that EE mainly affected the dominant microbiota. Several families, such as Erysipelotrichaceae, Tannerellaceae, Enterobacteriaceae, Burkholderiaceae, and Prevotellaceae were markedly reduced within the CB cohort. Bacteria such as Alloprevotella, Bifidobacterium, Enterobacteriaceae, Parabacteroides, and Erysipelatoclostridium were identified as having negative associations with the presence of serum cortisol. EE influenced rabbit behavior and serum hormonal levels, and CB enrichment was the most suitable for rabbits. Further, cecal microbiota composition and diversity were affected by CB enrichment. These findings suggested that CB could be considered for use in rabbit husbandry.

Dietary Iodine Affected the GSH-Px to Regulate the Thyroid Hormones in Thyroid Gland of Rex Rabbits

Iodine (I) is an essential trace element that can influence animal health and productivity. In this study, we investigated the effects of dietary iodine on the antioxidant indices of organ (liver and thyroid gland) and messenger RNA (mRNA) expression of glutathione peroxidase (GSH-Px) in Rex rabbits. A total of 120 4-month-old Rex rabbits (2235.4 ± 13.04 g BW) were divided into four equal groups, and their diets were supplemented with iodine (0, 0.2, 2, or 4 mg/kg dry matter (DM)). The iodine concentration in basal diet (control group) was 0.36 mg/kg DM. In most of measured parameters, supplemental iodine exerted no significant effect. Growth and slaughter performance and organ weight were not influenced significantly by iodine supplementation. Serum T₃ was significantly lower in 2-mg I group than in 0.2 and 4-mg I groups (P < 0.05). Superoxide dismutase (SOD), GSH-Px, methane dicarboxylic aldehyde (MDA), and thyroperoxidase (TPO) in the serum and liver were not influenced (P > 0.05). Conversely, serum catalase (CAT) was significantly reduced (P < 0.05). In the thyroid, GSH-Px was higher in the 2-mg I group than in the 0.2- and 4-mg I groups (P < 0.05). RT-PCR results showed that the mRNA expression level of GSH-Px in the liver was not significantly influenced (P > 0.05). In the thyroid gland, the mRNA expression level of GSH-Px was higher in the 2-mg I group than in the 4-mg I group (P < 0.05), which agreed with the activity of GSH-Px. In conclusion, iodine supplementation exerted no effect on the performance and antioxidant capacity of the body, but dietary iodine influenced serum T₃ or GSH-Px in the thyroid gland. Thus, on the basis of serum T₃ and GSH-Px levels in the thyroid gland, we hypothesized that GSH-Px secretion was increased by adding dietary iodine in the thyroid, which may inhibit the H₂O₂ generation and further influence the thyroid hormone synthesis.