In this study, we evaluated the fermentation quality, digestibility and rumen fermentation of total mixed ration silage (TMRS) prepared with varying proportions of apple pomace, using four wethers in a 4 × 4 Latin square study design. A control diet was prepared using corn, wheat bran, timothy hay, alfalfa hay and a vitamin–mineral supplement. In the experimental treatments, apple pomace supplemented with soybean meal was used to replace corn and wheat bran at levels of 5%, 10% and 20% on a dry matter (DM) basis; treatment levels are indicated by these replacement levels. The moisture content of all diets was adjusted to 550 g/kg and the diets were then ensiled for 60 days. All diets were well fermented, with low pH and ammonia nitrogen (N) content. In treatments including apple pomace, lactic acid content decreased as acetic acid increased compared with the control (p < .05). Ethanol was generated in the 5%, 10% and 20% treatments. Following the addition of apple pomace, ammonia N content increased, and was highest in the 5% treatment (p < .05). N retention and digestibility of DM, organic matter, crude protein and ether extract decreased significantly (p < .05) in the 10% and 20% treatments. The rumen molar proportion of acetic acid increased, but those of propionic acid and ammonia N content decreased as the proportion of apple pomace in the diets increased (p < .05). The results of this study suggest that the proportion of apple pomace in TMRS should not exceed that of the 5% TMRS treatment, which was 44 g/kg of diet DM.

MicroRNAs (miRNAs) are small, single-stranded, noncoding RNAs ~21 to ~23 nucleotides in length and have become a popular research topic in recent years due to their regulation of gene expression and many physiological processes, including fat metabolism; however, the precise functional mechanisms underlying their regulation of fat metabolism are not fully understood. Here, we identified miR-381, which specifically targets the 3′ untranslated region (3′ UTR) of potassium channel tetramerization-domain-containing 15 (KCTD15) , and verified the mechanism regulating its expression and participation in adipogenesis. We used a dual luciferase-reporter assay and transfection-mediated miR-381 overexpression and inhibition in Yanbian yellow cattle preadipocytes to investigate the role of miR-381 in adipogenesis. The results showed that miR-381 directly targets the 3′ UTR of KCTD15 and downregulates its expression. Additionally, miR-381 overexpression using an miRNA mimic promoted triglyceride accumulation and upregulated adipogenic peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT enhancer-binding protein α (C/EBPα) at both the protein and mRNA levels, whereas miR-381 inhibition produced the opposite effect. These results indicated that miR-381 regulates the differentiation of Yanbian yellow cattle preadipocytes by inhibiting KCTD15 expression, thereby highlighting the importance of miRNA-mediated regulation of adipogenesis. Furthermore, our findings suggested that miR-381 and its target gene(s) might represent new targets for investigating intramuscular fat deposits in cattle and treating human obesity.

FABP4 is a candidate gene for carcass and meat quality traits in livestock and poultry. However, the effects of FABP4 have not been examined in the Yanbian yellow cattle, an economically important local cattle breed in China. In this study, we characterized single nucleotide polymorphisms (SNPs) in FABP4 in this cattle breed and their associations with meat quality traits. Six SNPs (referred to as SNP1-6) were identified in FABP4 by direct sequencing and polymerase chain reaction-restriction fragment length polymorphism. The six SNPs were significantly correlated with meat quality traits. In particular, the GG and GA genotypes of SNP1 were significantly associated with water and fat contents and GG and AA genotypes of SNP1 were significantly associated with protein contents (P < 0.05). The fat content and marbling in heterozygous individuals at SNP2-6 were significantly higher than those in wild-type or mutant individuals (P < 0.05), while protein content was significantly higher in wild-type and mutant individuals than in heterozygous individuals (P < 0.05). A gene expression analysis indicated that the lipid metabolism-related genes FABP4, PPARγ, ANGPTL4, and LPL show similar expression patterns with respect to FABP4 genotypes, with the highest levels in wild-type individuals and the lowest levels in mutants. In conclusion, FABP4 SNPs can be used for marker-assisted selection in Yanbian yellow cattle breeding.

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