Investigation of the Nutritional Potential of some Rangeland Plants Species by in vitro Gas Production and Fermentation Parameters in Torbat-e Jam, Iran: A Meta-Analysis and Meta-Regression

The current study aimed to evaluate the nutritional potential of some rangeland plants by in vitro gas production kinetics and ruminal fermentation parameters in the Torbat-e Jam region using a meta-analysis approach. A comprehensive literature searches in the scientific databases was carried out to identify studies that investigated the variables of interest. The data analyzed were extracted from 13 peer-reviewed publications. The effect size of all outcomes was reported as a standardized means difference (SMD) with 95% confidence intervals (CI). Q test and I2 were calculated to determine the heterogeneity, and a meta-regression was also used to investigate sources of heterogeneity. A significant increase for 24 h in vitro gas production (IVGP) was observed (P 0.01). Among the estimated gas parameters, potential GP (bgas) and fractional rate of GP (cgas) were increased significantly (P 0.05). Also, short chain fatty acids (SCFA) (P 0.05), microbial protein yield (MPY) (P 0.01), and ammonia nitrogen (NH3-N) (P 0.01) of culture medium were increased. The values of I2 ( 50) and Q (P 0.05) for 24 h IVGP, bgas, cgas, SCFA, MPY and NH3-N indicated high heterogeneity. No publication bias was found for 24 h IVGP, bgas, and SCFA. With the evaluation of funnel plots, only one study on the right of each plot indicates publication bias for cgas, MPY, and NH3-N. A strong regression relation (P 0.01) between some chemical compositions (dry matter, crude protein, neutral detergent fiber, and acid detergent fiber) and MPY and NH3-N was suggested from meta-regression analysis. In conclusion, the current meta-analysis confirmed that there were differences in fermentation parameters among all rangeland plants. However, all plants species had a relatively high potential nutritive value. According to the reported fermentation parameters, it seems that most of the Torbat-e Jam rangeland plants species have high nutritional value in small ruminant feeding. More in vivo and in vitro studies are needed to assess the other nutritive values and their effects on animal performance.