Grazing effects on the nutritive value of dominant species in steppe grasslands of northern China

Interplay between Livestock Grazing and Aridity on the Ecological and Nutritional Value of Forage in Semi-arid Mediterranean Rangelands (NE Spain)

Rangeland-based livestock production constitutes a primary source of livelihood for many inhabitants of dryland regions. Their subsistence relies heavily on maintaining the productivity, biodiversity and services of these ecosystems. Harsh environmental conditions (e.g., drought) combined with land use intensification (e.g., overgrazing) make dryland ecosystems vulnerable and prone to degradation. However, the interplay between livestock grazing intensity and aridity conditions in driving the conservation and nutritional value of forage in arid and semi-arid rangelands is still not fully understood. In this study, we performed structural equation models (SEM) to assess the simultaneous direct and indirect effects of livestock grazing intensity and aridity level on community structure, diversity, biomass, forage production, forage C:N ratio and forage fiber composition in two semi-arid Mediterranean rangelands, NE Spain. Not surprisingly, we found that higher livestock grazing intensity led to lower community plant cover, especially when combined with higher aridity. However, both increasing grazing intensity and aridity were associated with higher forage production after one year of grazing exclusion. We did not find any adverse effect of livestock grazing on plant diversity, although plant species composition differed among grazing intensity levels. On the other hand, we found an aridity-driven trade-off in regard of the nutritional value of forage. Specifically, higher aridity was associated with a decrease in the least digestible fiber fraction (i.e., lignin) and an increase in forage C:N ratio. More interestingly, we found that livestock grazing modulated this trade-off by improving the overall forage nutritional value. Altogether, our results provide further insights into the management of semi-arid Mediterranean rangelands, pointing out that maintaining traditional rangeland-based livestock production may be a sustainable option as long as rangeland conservation (e.g., community plant cover) is not severely compromised.

Predicted changes in distribution and grazing value of Stipa-based plant communities across the Eurasian steppe

The Eurasian steppe is one of the world's largest continuous areas of grassland and has an important role in supporting livestock grazing, the most ubiquitous land use on Earth. However, the Eurasian steppe is under threat, from irrational grazing utilization, climate change, and resource exploitation. We used an ensemble modeling approach to predict the current and future distribution of Stipa-dominated plant communities in three important steppe subregions; the Tibetan Alpine, Central Asian, and Black Sea-Kazakhstan subregions. We combined this with an assessment of the grazing value of 22 Stipa species, the dominant grassland species in the area, to predict how grazing value might change under future climate change predictions. We found that the effects of changing climates on grazing values differed across the three subregions. Grazing values increased in the Tibetan alpine steppe and to a lesser extent in Central Asia, but there were few changes in the Black Sea-Kazakhstan subregion. The response of different species to changing climates varied with environmental variables. Finally, our trait-based assessment of Stipa species revealed variations in grazing value, and this had major effects on the overall grazing value of the region. Our results reinforce the importance of trait-based characteristics of steppe plant species, how these traits affect grazing value, and how grazing values will change across different areas of the Eurasian steppe. Our work provides valuable insights into how different species will respond to changing climates and grazing, with important implications for sustainable management of different areas of the vast Eurasian steppe ecosystem.

Karst grassland forage quality and its determinants in Guizhou Province of Southwest China

Forage quality is a key property of grassland ecosystems. In this study, grassland forage qualities were measured at 373 sampling sites throughout Guizhou Province in the karst mountain region of Southwest China, and the factors affecting it were explored. The forage quality level of most plant species was categorized into four levels: (1) preferred forage species; (2) desirable forage species; (3) consumed but undesirable forage species; and (4) non-consumable or toxic forage species. High temperature and precipitation appeared to facilitate the growth of preferred forage species, but limited the growth of other plants. Increasing soil pH had a positive impact on the number and biomass of preferred forage plants, but a negative influence on other plants, especially non-consumable or toxic plants. Both GDP and population density had a positive correlation with the number and biomass of preferred forage species, while such correlations for other levels of forage species tended to be negative. Grazing could lead to a decrease in the preferred forage species. Therefore, it is suggested that by focusing on soil improvement in grassland and maintaining an appropriate grazing intensity, global warming and rapid economic growth in Guizhou Province will likely contribute to increase the forage quality of karst grasslands in Southwest China.

Effects of grazing intensity on forage nutritive value of dominant grass species in Borana rangelands of Southern Ethiopia

Background

Forage nutritive value analysis is an essential indicator of rangeland status regarding degradation and livestock nutrient demand. Thus, it is used to maintain healthy and sustainable rangelands that can provide the livestock with sufficient quantity and quality of forage. This study is conducted with the aim of investigating the effects of grazing intensity combined with seasonal variation on the nutritive values of dominant grass species in the Teltele rangeland.

Methods

The studied area is classified into no-grazed, moderately grazed, and overgrazed plots based on the estimated potential carrying capacity. Sampling data is collected during both rainy and dry seasons. The collected forage samples are analyzed for concentrations of crude protein (CP), acid detergent organic fiber (ADF), neutral detergent fiber (NDF), acid detergent lignin (ADL), ash, dry matter digestibility (DMD), potential dry matter intake (DMI), and relative feed/forage value (RFV).

Results

The results show significant (P < 0.05) effects of both grazing intensity and season to grazing intensity interactions on all forage nutrient content concentrations across all grass species both within and between treatments. The recorded CP concentrations of all grass species are high in the overgrazed site and low at the no-grazed site, while the fiber concentration is high in NG and low in OG. RFV data also varies greatly, with high value recorded in OG in the rainy season and low value found in NG mainly during the dry season. As a result, it is recommended that moderate grazing should be practiced on the study site to maintain the quality and quantity of forage and to manage it in a sustainable manner.

Temporal variations of herbage production and nutritive value of three grasslands at different elevation zones regarding grazing needs and welfare of ruminants

Interannual and monthly variations of herbage production and nutritive value regarding grazing ruminants' needs and welfare were evaluated in three grasslands (semi-mountainous, mountainous and sub-alpine) located at different altitudes (480–900, 901–1500 and 1501–2334 m, respectively) in northern Greece during 2015–2016. Herbage biomass was collected from 30 experimental cages (10 per grassland), weighed, dried at 65 ∘C, milled and analyzed for crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, calcium (Ca) and phosphorus (P) content and in vitro dry matter digestibility (IVDMD). The sub-alpine grassland was the most productive (1031 and 1231 kg DM ha-1) with the highest mean annual herbage CP content (93 and 87 g kg-1 dry matter; DM) for 2015 and 2016, respectively. CP content was sufficient to meet small ruminants' and beef cattle maintenance requirements until April and May in the semi-mountainous and mountainous grasslands, respectively, while it could cover the above requirements in the sub-alpine grassland until June and August, respectively. The herbage Ca concentration was higher than the grazing ruminants' needs, while the phosphorus concentration was insufficient. Protein and phosphorus supplementation should be provided to animals to cover their maintenance requirements during the whole period and to reach high levels of welfare. Even though grazing is considered as a welfare-friendly procedure, it is uncertain whether all the welfare principals are satisfied in extensive production systems due to variations of forage availability and nutritive value as well as the lack of infrastructure in grasslands.