Summary Weaning weight is an important economic trait in the meat rabbit industry. Evidence has linked the gut microbiota to health and production performance in rabbits. However, the effect of gut microbiota on meat rabbit weaning weight remains unclear. In this study, we performed 16S rRNA gene sequencing analysis of 135 faecal samples from commercial Ira rabbits. We detected 50 OTUs significantly associated with weaning weight. OTUs that showed positive associations with weaning weight were mostly members of the family Ruminococcaceae which are important in degrading dietary fibres and producing butyrate. On the contrary, OTUs annotated to genera Blautia, Lachnoclostridium and Butyricicoccus correlated with fat deposition were negatively associated with weaning weight. Predicted functional capacity analysis revealed that 91 KOs and 26 KEGG pathways exhibited potential correlations with weaning weight. We found that gut microbiota involved in the metabolism of amino acids, butanoate, energy and monosaccharides affected weaning weight. Additionally, cross‐validation analysis indicated that 16.16% of the variation in weaning weight was explained by the gut microbiome. Our findings provide important information to improve weaning weight of meat rabbits by modulating their gut microbiome.

Three hundred and four female ducks of the Chinese indigenous Shan Ma breed, progeny of 11 sires and 104 dams, were used to study laying traits. Among them, 264 ducks were used to study the egg shell quality traits of eggs laid at 300 days of age. The mean age at first egg was 109 days with an average egg weight of 49.6 ± 3.7 g. Between 210 and 300 days of age, egg weight increased from 65.0 ± 3.9 g to 67.0 ± 4.2 g and the mean of the number of eggs laid up to 300 days was 161 ± 15.0. Egg length was 59.57 ± 3.01 mm and egg width was 45.02 ± 1.98 mm, leading to a shape index of 1.32 ± 0.08. Egg shell thickness was about 0.31 mm whatever the shell region, and the breaking strength was 28.80 ± 8.29 N. The heritability's estimated using restricted maximum likelihood (REML) methodology were high for egg weights (ranging from 0.43 to 0.61), intermediate for the number of eggs laid (ranging from 0.38 to 0.43), and low for the age at first egg (0.13). Heritability's for egg shell quality traits varied from 0.20 for the breaking strength to 0.44 for egg length, with in-between values of 0.28 for shell thickness and 0.34 for the shape index. The number of eggs laid was not genetically correlated with the age at first egg or egg weight, but was correlated with body weight (r g = +0.54 ± 0.23). High positive correlations were found between egg weight and body weight traits, and both of these traits (except egg weight at first egg) were highly and positively correlated with egg length and width. Breaking strength was genetically correlated with egg shell thickness (r g = +0.54 ± 0.19) and the shape index (r g = +0.71 ± 0.23). These results suggest that an efficient selection strategy could be implemented to improve the egg production of the pure Shan Ma duck line.

Alzheimer’s disease (AD), the most common cause of dementia, is a complex and multifactorial disease involving genetic and environmental factors, with hypercholesterolemia considered as one of the risk factors. Numerous epidemiological studies have reported a positive association between AD and serum cholesterol levels, and experimental studies also provide evidence that elevated cholesterol levels accelerate AD pathology. However, the underlying mechanism of hypercholesterolemia accelerating AD pathogenesis is not clear. Here, we review the metabolism of cholesterol in the brain and focus on the role of oxysterols, aiming to reveal the link between hypercholesterolemia and AD. 27-hydroxycholesterol (27-OHC) is the major peripheral oxysterol that flows into the brain, and it affects β-amyloid (Aβ) production and elimination as well as influencing other pathogenic mechanisms of AD. Although the potential link between hypercholesterolemia and AD is well established, cholesterol-lowering drugs show mixed results in improving cognitive function. Nevertheless, drugs that target cholesterol exocytosis and conversion show benefits in improving AD pathology. Herbs and natural compounds with cholesterol-lowering properties also have a potential role in ameliorating cognition. Collectively, hypercholesterolemia is a causative risk factor for AD, and 27-OHC is likely a potential mechanism for hypercholesterolemia to promote AD pathology. Drugs that regulate cholesterol metabolism are probably beneficial for AD, but more research is needed to unravel the mechanisms involved in 27-OHC, which may lead to new therapeutic strategies for AD.

In China and South East Asia, the duck (common duck) is important in egg production for human consumption. Plumage color is a breed characteristic and of economic importance, together with egg production. Our aim in this study was to investigate the inheritance of plumage color in three Chinese indigenous egg-type duck breeds, Shan Ma (S), Putian White (F) and Putian black (P), and some of their crossbreds. These three breeds have different plumage color and are used in crossbreeding. The crossbred laying ducks F×(P×S) and F×(S×P) showed highly improved laying ability but heterogeneous plumage color. Genotypes at four relevant loci were investigated by studying down color and pattern in ducklings after crossbreeding. F1 ducklings from the matings F×S and S×F, P×S, and S×P were classified into four classes of plumage color (the Shan Ma plumage color, black, white, or multicolored) over three generations. Parents were selected for the Shan Ma plumage color of their progeny. In the fourth generation, P male and P female ducks were selected according to the frequency of the desired class of plumage color (Shan Ma) of their F1 progeny to obtain the so-called “Brown Putian Ma duck”. The Shan Ma duck genotype was identified as having the restricted mallard color pattern (MRMR), full expression of any of the patterns or colors (CC), no extended black (ee) and no brown dilution D (D). The Putian White genotype was recessive white (cc), no extended black (ee) and no brown dilution D (D). The Putian Black genotype exhibited full expression of extended black (E gene) and no brown dilution (CCEE D [D]). It was shown that F×S and S×F tests should be implemented to eliminate the recessive white c allele in the S line and the dominant extended black E allele in the F line. It was also shown that the Brown Putian Ma obtained from Putian Black, with no extended black genotype (ee), could be used to get rid of the black plumage (E gene) in the crossbred ducks. This could provide a solution for producing 3-way crossbred ducks Putian White×(Putian-Ma ×Shan Ma) and Putian White×(Shan Ma×Putian-Ma), with the desired Shan Ma feather color.

Microphthalmia-associated transcription factor (MITF) is a key regulator for the development and function of melanocytes in skin, eye, and plumage pigmentations. Thus, the MITF was selected as a candidate gene associated with plumage coloration in ducks. This study analyzed the mRNA expression, promoter methylation, and polymorphisms in the MITF gene in ducks with different plumage colors (Putian Black, Putian White, Liancheng White, and Longsheng Jade-green). No expression of the MITF melanin-specific isoform (MITF-M) was detected in white feather bulbs. By contrast, the mRNA expression levels of MITF-M were high in black feather bulbs. Bioinformatics analysis showed that two CpG islands were present in the promoter region of the MITF gene. The methylation level of the second CpG island was significantly lower in black feather bulbs than in white feather bulbs. However, the methylation level of the first CpG island was not different among the feather bulbs with various colors except Liancheng White feather bulbs. The methylation status of the whole CpG island significantly and negatively correlated with the mRNA expression of MITF-M (P < 0.05). Furthermore, four novel SNPs (single nucleotide polymorphisms) were identified in the 5′UTR, exon 4, intron 7, and intron 8 of the MITF gene. Allele T in g.39807T>G and allele G in g.40862G>A were the predominant alleles only found in Putian White, whereas the variant A allele in g.32813G>A exhibited a high allele frequency in Liancheng White. Collectively, these results contributed to the understanding of the function of the MITF gene in duck plumage coloration.