The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council. |
Monday, January 28, 2008
29
Effect of Pre and Post Grazing Herbage Mass on Seasonal Pasture Growth and Nutritive Value
Cristian Ortiz Sr., Oscar Balocchi Sr., and Ignacio Lopez Sr. Instituto de Produccion Animal, Universidad Austral de Chile, Campus isla teja s/n, Valdivia, 5090000, Chile
It was assessed the effect of grazing frequency and intensity, both defined by herbage mass, on the dry herbage mass accumulation and its nutritive value of a Lolium perenne / Trifolium repens pasture, in Southern Chile (39° 47’ S, 73° 13’ W).
Seasonal levels of pre-grazing herbage mass (kg DM/ha) were defined as low frequency grazing (LF): 2600 for Spring (SpLF); 2400 for both Summer (SuLF) and Autumn (AuLF); and 1800 Winter (WiLF). Also pre-grazing herbage mass (kg DM/ha) defined high frequency grazing (HF): 2200 for Spring (SpHF), 2000 for Summer (SuHF) and Autumn (AuHF), and 1500 for Winter (WiHF). The grazing intensity was seasonally fixed as follows:1600 kg DM/ha as Low Intensity grazing for Spring (SpLI), Summer (SuLI) and Autumn (AuLI); 1300 kg DM/ha as Winter Low Intensity grazing (WiLI); 1200 kg DM/ha as High Intensity grazing for Spring (SpHI), Summer (SuHI) and Autumn (AuHI); and 1000 kg DM/ha as Winter High Intensity grazing (WiHI). Dairy cows were used to graze. Accumulated and available herbage mass (HM), metabolizable energy (ME), crude protein (CP) and neutral detergent fibre (NDF) were assessed. A factorial design with three blocks was applied. HM was not significantly different (P>0,05) in spring and summer. During autumn and winter HM was greater in AuLF-AuHI (P≤0,01) WiLF-WiHI and WiHF-WiHI (P≤0,001): 1427; 1393 and 1432 kg DM/ha, respectively, contrary to AuHF-AuLI, WiLF-WiLI and WiHF-WiLI with 863; 938 and 894 kg DM/ha, respectively.
During spring, the pasture nutritive value was similar (P>0,05) between the grazing treatments. Treatments had a significant effect on CP, being the highest values: 18,9% in SuHF-SuHI (P≤0,05) 28,63% in AuLF-AuHI (P≤0,01) and 27.3% in WiHF-WiLI (P≤0,05). ME differed amongst grazing treatments only during autumn (P≤0,05).
It is concluded that grazing frequency and intensity can generate relevant changes on pasture productive and quality features.
Seasonal levels of pre-grazing herbage mass (kg DM/ha) were defined as low frequency grazing (LF): 2600 for Spring (SpLF); 2400 for both Summer (SuLF) and Autumn (AuLF); and 1800 Winter (WiLF). Also pre-grazing herbage mass (kg DM/ha) defined high frequency grazing (HF): 2200 for Spring (SpHF), 2000 for Summer (SuHF) and Autumn (AuHF), and 1500 for Winter (WiHF). The grazing intensity was seasonally fixed as follows:
During spring, the pasture nutritive value was similar (P>0,05) between the grazing treatments. Treatments had a significant effect on CP, being the highest values: 18,9% in SuHF-SuHI (P≤0,05) 28,63% in AuLF-AuHI (P≤0,01) and 27.3% in WiHF-WiLI (P≤0,05). ME differed amongst grazing treatments only during autumn (P≤0,05).
It is concluded that grazing frequency and intensity can generate relevant changes on pasture productive and quality features.