Effect of different grazing intensities during the different stages of alpine grassland growth on the body weight gain of Tibetan sheep

The present study investigated the effects of different pasture growth periods and grazing intensities during the various stages of pasture growth on body weight gain of Tibetan sheep. Grazing experiments using the Tibetan sheep were conducted as heavy (5.13 sheep units·ha⁻¹), moderate (3.92 sheep units·ha⁻¹), and light (3.03 sheep units·ha⁻¹) grazing. The results indicated that: 1) Differences in daily weight gain of Tibetan sheep over the years were influenced by the environment. The daily weight gain of Tibetan sheep during the rejuvenation and growth periods of the pasture were higher than that during the period when withering of grass occurred (P < 0.05). Linear regression analysis results confirmed a linear relationship with negative slope (y = 0.308 8 − 0.110 7x) indicating a significant correlation between daily weight gain of Tibetan sheep and stage of pasture growth. 2) Different grazing intensities showed nonsignificant impact on daily weight gain, average individual weight gain in warm season, and weight gain per unit of grassland area of the Tibetan sheep. However, the average individual weight gain of Tibetan sheep during the warm season in each year was higher upon moderate grazing than upon light and heavy grazing. The weight gain of Tibetan sheep calculated per unit of grassland area was found to be slightly lower in the light grazing group than in the moderate and heavy grazing groups. In summary, the body weight gain of Tibetan sheep during the warm season in the alpine grasslands gradually decreased from the pasture rejuvenation period to the growth period followed by the withering period, irrespective of the grazing intensities employed. Moderate grazing intensity is suggested as a relatively suitable approach for the primary objective of livestock production along with a concurrent consideration of the sustainable use of grasslands.