Effects of dietary physical or nutritional factors on morphology of rumen papillae and transcriptome changes in lactating dairy cows based on three different forage-based diets

Abstract

BackgroundRumen epithelial tissue plays an important role in nutrient absorption and rumen health. However, whether forage quality and particle size impact the rumen epithelial morphology is unclear. The current study was conducted to elucidate the effects of forage quality and forage particle size on rumen epithelial morphology and to identify potential underlying molecular mechanisms by analyzing the transcriptome of the rumen epithelium (RE). To achieve these objectives, 18 mid-lactation dairy cows were allocated to three groups (6 cows per group), and were fed with one of three different forage-based diets, alfalfa hay (AH), corn stover (CS), and rice straw (RS) for 14 weeks, respectively. Ruminal volatile fatty acids (VFAs) and epithelial thickness were determined, and RNA-sequencing was conducted to identify the transcriptomic changes of rumen epithelial under different forage-based diets.ResultsThe RS diet exhibited greater particle size but low quality, the AH diet was high nutritional value but small particle size, and CS diet was low quality and small particle size. The ruminal total VFA concentration was greater in AH compared with those in CS or RS. The width of the rumen papillae was greater in RS-fed cows than in cows fed AH or CS. In total, 31, 40, and 28 differentially expressed (DE, fold change > 2, FDR < 0.05) genes were identified via pair-wise comparisons including AH vs. CS, AH vs. RS, and RS vs. CS, respectively. Functional classification analysis of DE genes revealed dynamic changes in ion binding (such as DSG1) between AH and CS, proliferation and apoptotic processes (such as BAG3, HLA-DQA1, and UGT2B17) and complement activation (such as C7) between AH or RS and CS. The expression of HLA-DQA1 was down-regulated in RS compared with AH and CS, and the expression of UGT2B17 was down-regulated in RS compared with CS, with positive (R = 0.94) and negative (R = -0.96) correlation with the width of rumen epithelial papillae (P < 0.05), respectively.ConclusionOur results suggest that both nutrients (VFAs) and particle sizes can alter expression of genes involved in cell proliferation/apoptosis process and complement complex. Our results suggest that particle size may be more important in regulating rumen epithelial morphology when animals are fed with low-quality forage diets and the identified DE genes may affect the RE nutrient absorption or morphology of RE. Our findings provide insights into the effects of the dietary particle size in the future management of dairy cow feeding, that when cows were fed with low-quality forage (such as rice straw), smaller particle size may be beneficial for nutrients absorption and milk production.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-3726-2) contains supplementary material, which is available to authorized users.

Metabolomics Integrated with Transcriptomics Reveals a Subtle Liver Metabolic Risk in Dairy Cows Fed Different Crop By‐products

“…In our previous work, the cows in the RS group displayed a thicker ruminal papilla layer and epithelial layer than the cows in the CS group, which may prevent nutrient absorption and therefore affect the metabolite profile in the liver. Liver tissue metabolomics data had a clear discrimination between cows in the CS and RS groups.…”

“…In our study, the nutrient composition was similar but the physical size showed great difference between the CS and RS diets. Both the proportion of particles with a size > 19 mm (40.4% vs 16.9%) and the peNDF >19 mm (14.9 vs 6.1) were significantly higher in the RS than CS, which increased the rumen epithelial thickness and inhibited the nutrient degradation and absorption, and thus limited the nutrient supplying and metabolism in the liver. Therefore, it is likely that different crop by‐products alter liver metabolism.…”

“…Even though the utilization practice of CS and RS in the ruminant diet has been explored for hundreds of years, the understanding of metabolic functions and host responses under different crop by‐products is still limited. Our previous studies have identified the different thicknesses of rumen papilla and differentially expressed genes in the rumen and mammary gland when dairy cows were fed diet with CS or RS as main forage sources . It is known that the diet nutrients digested in the rumen are absorbed by the rumen epithelial wall and are then transported to the liver for glycogenesis, followed by transportation to the mammary gland for milk synthesis through the blood stream.…”

“…Our previous study found that after 12 weeks of feeding with the RS‐based diet, the rumen papillae width in dairy cows was thicker than in cows on the CS diet, and 28 differentially expressed genes were identified using transcriptomics . The emerging high‐throughput‐based multi‐omics technologies have proven to be a powerful tool to capture key changes and to uncover underlying biological mechanisms in ruminants .…”

Jersey steer ruminal papillae histology and nutrigenomics with diet changes

“…The outer dense plaque contains the intracellular ends of desmocollin and desmoglein; this last one being the structure, we were interested in analysing. Desmoglein ( DSG1 ) is a cell structure involved in cell‐to‐cell adhesion, and it is associated with cellular transport and structure through dynamic changes through ion bindings (Wang et al, ). DSG1 is highly expressed in stratified squamous epithelium, especially the stratum granulosum (Green & Simpson, ).…”