Seasonal changes in parotid and rumen papillary development in Mongolian gazelle (Procapra gutturosa Pallas)

The Mongolian gazelle (Procapra gutturosa Pallas) lives in the Mongolian Plateau, where conditions are dry and cold from late autumn to early spring. The climate results in apparent seasonal changes in the nutrition of forage plants on the plateau. The morphology of the gazelle's rumen papillae and the weight of their salivary glands also reflect these changes. The relative weight of the parotids to body mass (0.8–1.3 g kg−1 and 1.8–2.7 g kg−0.75) and the surface enlargement factor (SEF) of the internal rumen wall (8.5–12.0) fell within the range of mixed (intermediate) feeders. Although previous studies in a great number of ruminants have shown that parotid mass and SEF are positively related to feed quality, we found that relative parotid mass to body mass increased in winter, the dry and cold season, during the poorest dietary conditions. The surface enlargement factor increased from autumn to winter and spring, during the poorest and best seasons in feed quality, respectively. It is possible that an increase in parotid mass is related to water shortage from both feed and habitat in winter. An increase in parotid mass, suggesting an increase in saliva production, could meet the liquid needs of the gazelles during feeding and rumination in poor and dry forage seasons. The development of rumen papilla and the consequent increase in SEF in poor food seasons should result in the effective absorption of nutrients by Mongolian gazelles.