Abstract: Grazing integrates multiple processes including bruising, defoliation, and the deposition of saliva, which may affect the regrowth of forage grasses. In this study, alfalfa plants defoliated at different intensities were treated with exogenous inorganic salts and with thiamine (treatment groups), and deionized water and sheep saliva (control groups). The aim of this study was to determine whether a herbivorous animal’s (sheep) saliva, especially its components (inorganic salts and thiamine) positively affect alfalfa regrowth. We also analyzed how the defoliation and sheep saliva interaction induced compensatory regrowth, and evaluated the morphological and physiological differentiation of defoliated alfalfa after treatment with inorganic salts and thiamine. Our results showed that, compared with alfalfa in the defoliation-only treatment, that in the saliva+defoliation treatment showed significantly better regrowth due to an effective ingredient in saliva (thiamine). Compared with defoliated alfalfa treated with exogenous inorganic salts, that treated with thiamine grew better, as indicated by the significantly greater aboveground biomass, 4.3-7.9-times greater stem/leaf ratio, and 1.56-times higher total tiller number at the 80% defoliation level. The physiological characteristics of defoliated alfalfa did not vary widely among treatments. In all treatments, the chlorophyll content of defoliated alfalfa was close to 49.3 mg/g. At the 20% defoliation level, alfalfa plants treated with sheep saliva and with water showed significantly increased soluble sugars contents in the roots, compared with those in the inorganic salts and thiamine treatments. Treatment with inorganic salts led to a progressive increase in peroxidase activity as the defoliation intensity increased, while treatment with thiamine did not affect peroxidase activity. These results increase our understanding of the functional mechanism of the alfalfa response to herbivore grazing. These results provide a reference for improving the status of artificial grassland and for improving the agricultural efficiency of cultivated forage grasses. The results of this study provide theoretical support for the development of ecologically sound grazing regimes.