The effects of grazing management strategies on the vegetation, diet quality, intake and performance of free grazing sheep
Introduction
Native grasslands in China cover 400 million hectares, about 40% of the land area (Wang and Ba, 2008). Forage produced on native grassland is the predominate source of livestock feed in semi-arid region of China. In the last decades, the native grassland was extensively degraded through overgrazing and over-exploitation of natural resources. Sustained utilization of these grasslands may improve the long-term animal performance as well as protect grassland from degradation and maintain ecological stability (Kemp and Michalk, 2007, Li et al., 1999). Many studies showed that recovery periods of the grassland after grazing are important for maintaining productivity of grasslands. This recovery period can be realized either by reducing the amount of animals during the grazing periods (Schönbach et al., 2009) or by preventing grazing in critical periods (Li et al., 2001, Li et al., 2005, Zhao et al., 2003). Spring grazing can reduce herbage mass by reducing plant cover and vegetation height (Li et al., 2005, Yun et al., 2010, Zhao et al., 2003). This will in turn decrease the herbage intake and performance of livestock (Li et al., 2005). Even though grazing sheep display a higher selective intake behavior at different stocking rates due to differences in herbage quality offered and ingested (Han et al., 2000, Kristensen, 1988, Wang et al., 2011). Stocking rate and grazing period may also influence feed quality and affect the herbage intake and animal performance (Glindemann et al., 2009, Lin et al., 2012). An assessment of dietary nutrient content of forage and dry matter intake by sheep on such grazing resources is necessary to formulate suitable grassland management strategies and to identify variations in herbage mass and nutrient content that constrain animal production.
In this study, the effects of grazing strategies on herbage mass (HM), diet quality; organic matter intake (OMI) and live weight gain (LWG) of sheep were evaluated. The hypothesis in this study is whether the spring grazing is a critical factor and grazing intensity should be varied according to the growing season on the steppe. The objectives of the study were tested the effects of grazing season and grazing intensities on the variables of herbage mass and animal performance which included the following aspects: 1. The effects of two different summer and autumn grazing strategies; 2. The effect of no spring grazing with a high stocking rate in the spring; 3. The effect of the moderate and high stocking rates in the autumn; 4. The effects of the moderate and high stocking rate throughout the season. This study will provide valuable information for developing grazing strategies during the growing season and providing guides for adjusting grazing management strategies based on herbage mass availability and sheep performance.
Section snippets
Study area description
The research was conducted on the national grassland ecosystem research station (long 115°46'E, lat 41°44'N, alt 1380 m, which is located in the semi-arid region (annual rainfall 300–400 mm of which 60% falls during the period of June to August) of Hebei province in China. Summer temperatures are warm with very cold winters, and the mean annual temperature is 1 °C. Mean temperature in January is −18.6 and 17.6 °C in July (Fig. 1). Annual evaporation is 1736 mm, which is more than four times of the
Effects of grazing management strategies and grazing periods on HM, herbage intake, diet chemical composition and digestibility
The herbage mass, intake, chemical composition and digestibility of the apparently eaten herbage in different grazing strategies are given in Table 2. HM varied a lot with different grazing strategies from 337 (SA3) to 1004 kg DM/ha (SA2) (P<0.05). The herbage mass was minimum with continuous high stocking rate in all grazing periods (SA3). The average HM was 3-times larger for grazing strategies where grazing was deferred in the late spring compared to continuous high stocking rates. There were
Effect of grazing period on HM, herbage intake, diet chemical composition and digestibility
The quantity and digestibility of available herbage varied significantly from late spring to autumn. Herbage mass was highest in the summer and lowest in late spring. Similarly Valdés et al. (1995) reported that grazing period (summer and autumn) could significantly increase OMI and CP, but decrease NDF of diets. The result does not agree with Glindemann et al. (2009) that reported available herbage decreased from July to September in Inner Mongolia steppe. According to Glindemann et al. (2009)
Conclusion
The results of this study showed that the grazing management strategies must adjust the grazing intensity according to the grassland growth rate in the grazing period. Grazing period and grazing intensity affected quality of diets, OMI, DOMI and LWG per sheep and per ha in sheep grazing on the steppe. The primary factor affecting livestock performance was the biomass of forage allocated to animals over the grazing period, which was influenced by grazing period in the growing season. Spring
Conflict of interest statement
The authors do not have possible confilicts of interest.
Acknowledgments
The authors wish to thank Dr. Marshall Haferkamp for reviewing the manuscript and show great gratitude to livestock holder Shounan Shen who provided the grazing sheep. The research was supported by the China Special Public Sector Research Project (Agriculture: 200903060 and 201003019) and the State Key Development Program for Basic Research of China (Project no. 2014CB138805). Animal management was done according to international and institutional guidelines for animal care, and approved by
References (36)
- et al.
Impact of grazing intensity on herbage intake, composition, and digestibility and on live weight gain of sheep on the Inner Mongolian steppe
Livest. Sci.
(2009) - et al.
Dynamics of soil physical and chemical properties and vegetation succession characteristics during grassland desertification under sheep grazing in an agro-pastoral transition zone in Northern China
J. Arid. Environ.
(2007) - et al.
Growth of sheep as affected by grazing system and grazing intensity in the steppe of Inner Mongolia, China
Livest. Sci.
(2012) - et al.
Comparison of diet and fecal collection methods for assessment of seasonal variation in dry matter intake by sheep maintained on Cenchrus ciliaris pasture
Anim. Feed. Sci. Tech.
(1999) - et al.
Estimating fecal output in reindeer during winter
Livest. Prod. Sci.
(2003) - et al.
Fecal crude protein content as an estimate for the digestibility of forage in grazing sheep
Anim. Feed. Sci. Tech.
(2009) - et al.
Diet selection variation of a large herbivore in a feeding experiment with increasing species numbers and different plant functional group combinations
Acta Oecologica
(2011) - et al.
The effect of sward height and its direction of change on the herbage intake, diet selection and performance of weaned lambs grazing ryegrass swards
Grass Forage Sci.
(1995) - Clifford, P., 1998. Essential concepts of sustainable grazing management. Otero Country. Colorado State University....
- et al.
The ability of sheep at different stocking rates to maintain the quality and quantity of their diet during the grazing season
J. Agric. Sci.
(2003)
Live weight change of sheep under 5 stocking rates in Stipa breviflora desert steppe
Grassl. China
Cattle, vegetation, and economic responses to grazing systems and grazing pressure
J. Range Manage.
The influence of stocking rate, range condition and rainfall on seasonal beef production patterns in the semi-arid savanna of KwaZulu-Natal
S. Afr. J. Anim. Sci.
Towards sustainable grassland and livestock management
J. Agric. Sci.
Influence of defoliation regime on herbage production and characteristics of intake by dairy cows as affected by grazing intensity
Grass Forage Sci.
The use of chromium oxide to estimate the fecal output of Merinos
Aust. J. Agr. Res.
Delay grazing a practical approach to grassland environment protection and sustainable animal production in grassland of northern China
Acta Agrestia Sinicia
Cited by (23)
Methane emissions in grazing systems in grassland regions of China: A synthesis
2019, Science of the Total EnvironmentCitation Excerpt :Furthermore, the HBM at the end of grazing season, daily OMI by sheep and LWG were linearly decreased with increasing SR (Fig. 5a–c), suggesting the importance of lowering the SR for improving the productivities for grasslands and sheep. It is well known that HBM at the end of grazing season is an important indicator for the healthy status of grassland, and daily OMI and LWG are key indicators for meat production in grazing systems (Glindemann et al., 2009; Ma et al., 2014), and the metric of greenhouse gas emission intensity can be utilized as a tool for acknowledging potential trade-offs between food (and meat, forage, and fuel) production and climate change mitigation (Ma et al., 2018b; Van Groenigen et al., 2010; Yao et al., 2017). In our study, the estimated CH4 emission intensities, i.e., CH4 emission per HBM, OMI, and LWG, were all linearly increased with increasing SR for both 2 cases (Fig. 5).
Annual methane budgets of sheep grazing systems were regulated by grazing intensities in the temperate continental steppe: A two-year case study
2018, Atmospheric EnvironmentCitation Excerpt :The experimental area was closed to grazing in 2009 and rested for one year to restore grassland productivity. Beginning in 2010, UG was un–grazed, DG was grazed at a stocking rate of 5.3 sheep ha−1 from July to late September with 30–40% biomass removal (equivalent to 1.0 sheep unit ha−1 year−1), MG was grazed at a stocking rate of 6.7 sheep ha−1 from June to late September with 50–55% biomass removal (equivalent to 1.43 sheep units ha−1 year−1), and HG was grazed at a stocking rate of 9.3 sheep ha−1 from June to late September with 75–85% biomass removal (equivalent to 2.33 sheep units ha−1 year−1) (Ma et al., 2014). The HG treatment is equivalent to the local grassland grazing management regime.
Soil respiration patterns for four major land-use types of the agro-pastoral region of northern China
2015, Agriculture, Ecosystems and EnvironmentCitation Excerpt :The climate is a semi-arid continental climate, which in summer is dominated by warm, moist air currents and other seasons are dominated by cold, dry air currents. Mean annual precipitation is 400 mm, nearly 75–80% of which is received from June to August (Ma et al., 2014). Mean annual temperature is 1 °C with a mean minimum temperature of –18.6 °C in January and mean maximum of 17.6 °C in July.
Methane uptake by four land-use types in the agro-pastoral region of northern China
2015, Atmospheric EnvironmentNutritional characteristics estimated by faecal protein in cattle fed with heterogeneous natural grassland
2024, Animal Production Science