Assessing the Effects of Dietary Cadmium Exposure on the Gastrointestinal Tract of Beef Cattle via Microbiota and Transcriptome Profile

Simple Summary Cadmium is a ubiquitous environmental pollutant present in soil, which can be absorbed by plants, animals, and humans, causing tissue damage or dysfunction. Ruminants possess rumen microorganisms to establish tolerance against plant toxins. However, there are few studies describing the response of ruminants to cadmium accumulated in plants. The objective of this study was to evaluate the impact of feeding cadmium-accumulated maize on growth, gastrointestinal response, and microbial alterations in cattle. The results show that cadmium-accumulated maize promoted weight gain and feed efficiency and increased the abundance of short-chain fatty acid-related bacteria, but also had suppressive effects on gastrointestinal immune regulation at the genetic level.Abstract Cadmium (Cd) is an environmental pollutant, widely existing in soil, and can be absorbed and accumulated by plants. Hunan Province exhibits the worst cadmium contamination of farmland in China. Ruminants possess an abundant microbial population in the rumen, which enables them to tolerate various poisonous plants. To investigate whether the rumen microbiota could respond to Cd and mitigate the toxicity of Cd-accumulated maize to ruminants, 6-month-old cattle were fed with 85.82% (fresh basis) normal whole-plant maize silage diet (CON, n = 10) or Cd-accumulated whole-plant maize silage diet (CAM, n = 10) for 107 days. When compared to the CON cattle, CAM cattle showed significantly higher gain-to-feed ratio and an increased total bacterial population in the rumen, but a decreased total bacterial population in the colon. CAM cattle had higher relative abundance of Prevotella and Lachnospiraceae ND3007 group in the rumen, and Lachnospiraceae NK4A136 group and Clostridia vadinBB60 group in the colon. Notably, microbial correlations were enhanced in all segments of CAM cattle, especially Peptostreptococcaceae in the jejunum. Transcriptome analysis revealed down-regulation of several immune-related genes in the rumen of CAM cattle, and differentially expressed genes in the rumen were mostly involved in immune regulation. These findings indicated that feeding Cd-accumulated maize diet with a Cd concentration of 6.74 mg/kg dry matter (DM) could stimulate SCFA-related bacteria in the rumen, induce hormesis to promote weight gain, and improve energy utilization of cattle.

Automated summary

This study evaluated the impact of feeding cadmium-accumulated maize on growth, gastrointestinal response, and microbial alterations in cattle. The results showed that cadmium-accumulated maize promoted weight gain and feed efficiency, increased the abundance of short-chain fatty acid-related bacteria, but also had suppressive effects on gastrointestinal immune regulation.