Analysis of factors affecting the nutritional composition of roughage using existing data: A case study on China and Africa

Context or problem

Most studies suggested that as the concentration of atmospheric carbon dioxide increases, straw seemed to be becoming more difficult to digest, but this was not absolute. Due to various factors, there has been no consensus on the changes in straw composition and digestibility.

Objective or research question

The purpose of this study is to investigate the differences in straw composition between China and Africa, as well as the influencing factors, and to establish a predictive model for the in vitro dry matter digestibility.

Methods

A total of 14574 articles were retrieved from China National Knowledge Infrastructure, PubMed, Web of Science, and Google Scholar, and the articles were screened and data was extracted. A total of 709 articles were relevant to our research. The Z-score (a standard score <3 was considered acceptable) function was used to constrain the obtained data. The obtained data was used to analyze the differences in straw composition between China and Africa, the main factors affecting straw composition, and changes in in vitro digestibility. Similarly, articles on the in vitro dry matter digestibility of straw had been collected. After evaluating the quality of the articles and filtering the data, an in vitro dry matter digestibility model had been constructed.

Results

The research results indicated that there was a significant difference in the composition of rice straw and corn straw between Africa and China, with African straw having a higher Neutral detergent fiber (NDF) than Chinese straw, and the difference between corn straw was extremely significant (P < 0.01). The crude protein (CP) content of Chinese straw was significantly higher than that of African straw (P < 0.05). In terms of time, the contents of crude protein (CP) and ligin (LIG) in straw,except for corn straw in China, also showed an increasing trend over time. On the latitude, the CP of rice and corn showed a decreasing trend with increasing latitude, while the LIG content showed an increasing trend except for wheat straw in China. A model for in vitro digestibility was constructed based on the relationship between straw composition and in vitro digestibility: IVDMD = 155.26 + 1.446–0.083CP² + 3.652EE - 1.147EE² - 2.77Ash + 0.137Ash² - 3.091NDF + 0.023NDF² + 1.016ADF - 0.019ADF².

Conclusions

The results indicated that there were significant differences in straw composition between China and Africa. And the composition of straw was influenced by various factors, especially atmospheric carbon dioxide concentration. It was expected that, under the continuous increase in atmospheric CO₂ concentrations, although the CP content of straw would rise, the in vitro dry matter digestibility of straw would continue to decline.

Implications or significance

This study revealed the changes in straw composition under current global environmental changes, provided a universal predictive model for in vitro dry matter digestibility, and recommended straw from low-latitude regions as the preferred feed source globally.