Abstract
SUMMARY The grassland steppe of Inner Mongolia is traditionally used for sheep grazing. However, overgrazing reduced vegetation cover in winter, thereby increasing soil erosion and consequently, degradation of the steppe vegetation. Grazing intensity (GI) is still the most important factor in pasture management. Hence, the aim of the current study was to evaluate the effect of GI on grassland and sheep performance. A grazing experiment was conducted from July until September in 2005, 2006 and 2007 in which six different GI ranging from very light (GI 1), light (GI 2), light-moderate (GI 3), moderate (GI 4) and heavy (GI 5) to very heavy (GI 6) were tested. Each GI treatment comprised two adjacent plots that were alternately used for grazing or hay-making each year. Variables measured included herbage mass (HM) and chemical composition, digestibility of ingested organic matter (dOM), organic matter intake (OMI) and live weight gain (LWG) of sheep. The HM decreased significantly with increasing GI from 1·01 t (GI 1) to 0·45 t dry matter (DM)/ha (GI 6). There were only minor effects of GI on chemical composition and digestibility of standing herbage. Moreover, dOM, OMI and hence, digestible OMI did not differ between GI. Across all study years, LWG of sheep was not influenced by GI so that LWG per hectare increased with increasing GI, reaching a maximum of 730 g/d at GI 6 compared with 181 g/d at GI 1. However, a strong decrease in LWG per sheep with increasing stocking rate was found in 2005 when annual rainfall was less than half of the long-term average, resulting in a similar LWG per hectare across the range of tested stocking rates. The results therefore show that intensive grazing does not reduce growth of individual animals in most years, but increases LWG per unit of land area and thus, income of farmers. The alternating use of pastures for grazing or hay-making might have mitigated the negative effects of heavy grazing on herbage and animal performance. Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals.
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Claims 11
Claim · model-written summary
Herbage mass decreased significantly with increasing grazing intensity from GI 1 to GI 6
Verbatim
e0“The HM decreased significantly with increasing GI from 1·01 t (GI 1) to 0·45 t dry matter (DM)/ha (GI 6)”
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
Grazing intensity had only minor effects on chemical composition and digestibility of standing herbage
Verbatim
e1“There were only minor effects of GI on chemical composition and digestibility of standing herbage”
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
Digestibility of organic matter, organic matter intake and digestible organic matter intake did not differ between GI treatments
Verbatim
e2“Moreover, dOM, OMI and hence, digestible OMI did not differ between GI”
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
Live weight gain of sheep was not influenced by grazing intensity across study years
Verbatim
e3“Across all study years, LWG of sheep was not influenced by GI so that LWG per hectare increased with increasing GI, reaching a maximum of 730 g/d at GI 6 compared with 181 g/d at GI 1”
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
Live weight gain per hectare increased with increasing grazing intensity, reaching 730 g/d at GI 6 compared with 181 g/d at GI 1
Verbatim
e3“Across all study years, LWG of sheep was not influenced by GI so that LWG per hectare increased with increasing GI, reaching a maximum of 730 g/d at GI 6 compared with 181 g/d at GI 1”
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
Live weight gain per sheep decreased strongly with increasing stocking rate in 2005 when rainfall was low
Verbatim
e4“However, a strong decrease in LWG per sheep with increasing stocking rate was found in 2005 when annual rainfall was less than half of the long-term average, resulting in a similar LWG per hectare across the range of tested stocking rates”
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
Live weight gain per hectare was similar across the tested stocking rates in 2005
Verbatim
e4“However, a strong decrease in LWG per sheep with increasing stocking rate was found in 2005 when annual rainfall was less than half of the long-term average, resulting in a similar LWG per hectare across the range of tested stocking rates”
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
Intensive grazing does not reduce growth of individual animals in most years
Verbatim
e5“The results therefore show that intensive grazing does not reduce growth of individual animals in most years”
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
Alternating use of pastures might mitigate the negative effects of heavy grazing on herbage and animal performance
Verbatim
e6“The alternating use of pastures for grazing or hay-making might have mitigated the negative effects of heavy grazing on herbage and animal performance”
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
High grazing intensity may negatively affect grassland productivity in the long term
Verbatim
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”
Claim · model-written summary
Heavy grazed pastures in dry years will require supplement feeding or untimely sale of animals
Verbatim
e7“Nevertheless, high GI may negatively affect grassland productivity in the long term and the lack of HM on offer on heavy grazed pastures in dry years will require supplement feeding at the end of the vegetation period or the untimely sale of animals”