Abstract
BackgroundThis study aimed to elucidate the molecular mechanisms of solid diet introduction initiating the cellular growth and maturation of rumen tissues and characterize the shared and unique biological processes upon different solid diet regimes.MethodsTwenty-four Hu lambs were randomly allocated to three groups fed following diets: goat milk powder only (M, n = 8), goat milk powder + alfalfa hay (MH, n = 8), and goat milk powder + concentrate starter (MC, n = 8). At 42 days of age, the lambs were slaughtered. Ruminal fluid sample was collected for analysis of concentration of volatile fatty acid (VFA) and microbial crude protein (MCP). The sample of the rumen wall from the ventral sac was collected for analysis of rumen papilla morphology and transcriptomics.ResultsCompared with the M group, MH and MC group had a higher concentration of VFA, MCP, rumen weight, and rumen papilla area. The transcriptomic results of rumen wall showed that there were 312 shared differentially expressed genes (DEGs) between in “MH vs. M” and “MC vs. M”, and 232 or 796 unique DEGs observed in “MH vs. M” or “MC vs. M”, respectively. The shared DEGs were most enriched in VFA absorption and metabolism, such as peroxisome proliferator-activated receptor (PPAR) signaling pathway, butanoate metabolism, and synthesis and degradation of ketone bodies. Additionally, a weighted gene co-expression network analysis identified M16 (2,052 genes) and M18 (579 genes) modules were positively correlated with VFA and rumen wall morphology. The M16 module was mainly related to metabolism pathway, while the M18 module was mainly associated with signaling transport. Moreover, hay specifically depressed expression of genes involved in cytokine production, immune response, and immunocyte activation, and concentrate starter mainly altered nutrient transport and metabolism, especially ion transport, amino acid, and fatty acid metabolism.ConclusionsThe energy production during VFA metabolism may drive the rumen wall development directly. The hay introduction facilitated establishment of immune function, while the concentrate starter enhanced nutrient transport and metabolism, which are important biological processes required for rumen development.
Highlights
This study aimed to elucidate the molecular mechanisms of solid diet introduction initiating the cellular growth and maturation of rumen tissues and characterize the shared and unique biological processes upon different solid diet regimes
The hay introduction facilitated establishment of immune function, while the concentrate starter enhanced nutrient transport and metabolism, which are important biological processes required for rumen development
This study aimed to investigate the molecular mechanisms of rumen wall morphological and functional development induced by different solid diet introduction, and to characterize the specific molecular and biological processes upon introduction of hay or concentrate
Summary
This study aimed to elucidate the molecular mechanisms of solid diet introduction initiating the cellular growth and maturation of rumen tissues and characterize the shared and unique biological processes upon different solid diet regimes. As the specific digestive and metabolism organ in ruminants, is responsible for feed degradation, nutrient absorption and metabolism, and immune response, where microbial fermentation produces volatile fatty acids (VFAs), microbial proteins, vitamins, and other nutrients [1, 2]. Rumen development process consists of microbial colonization, functional achievement, as well as anatomic development [5]. Microbial colonization performs efficient digestion of feed components, thereby providing nutrients for the physiological requirements of the animal [5]. Rumen wall has an important role in immune and barrier functions, its integrity is essential to ensure the health of ruminants [1]. Improving rumen wall morphology and physiological function development by nutritional strategies during this early period has great significance for ruminant life-time health and production
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