title: Reduced Cortisol and Metabolic Responses of Thin Ewes to an Acute Cold Challenge in Mid-Pregnancy: Implications for Animal Physiology and Welfare

authors: Verbeek, Else

subjects: biology

abstract: Background: Low food availability leading to reductions in Body Condition Score (BCS; 0 indicates emaciation and 5 obesity) in sheep often coincides with low temperatures associated with the onset of winter in New Zealand. The ability to adapt to reductions in environmental temperature may be impaired in animals with low BCS, in particular during pregnancy when metabolic demand is higher. Here we assess whether BCS affects a pregnant animal’s ability to cope with cold challenges.

Methods: Eighteen pregnant ewes with a BCS of 2.760.1 were fed to attain low (LBC: BCS2.360.1), medium (MBC: BCS3.260.2) or high BCS (HBC: BCS3.660.2). Shorn ewes were exposed to a 6-h acute cold challenge in a climate-controlled room (wet and windy conditions, 4.460.1uC) in mid-pregnancy. Blood samples were collected during the BCS change phase, acute cold challenge and recovery phase.
Results: During the BCS change phase, plasma glucose and leptin concentrations declined while free fatty acids (FFA) increased in LBC compared to MBC (P,0.01, P,0.01 and P,0.05, respectively) and HBC ewes (P,0.05, P,0.01 and P,0.01, respectively). During the cold challenge, plasma cortisol concentrations were lower in LBC than MBC (P,0.05) and HBC ewes (P,0.05), and FFA and insulin concentrations were lower in LBC than HBC ewes (P,0.05 and P,0.001, respectively). Leptin concentrations declined in MBC and HBC ewes while remaining unchanged in LBC ewes (P,0.01). Glucose concentrations and internal body temperature (Tcore) increased in all treatments, although peak Tcore tended to be higher in HBC ewes (P,0.1). During the recovery phase, T4 concentrations were lower in LBC ewes (P,0.05).
Conclusion: Even though all ewes were able to increase Tcore and mobilize glucose, low BCS animals had considerably reduced cortisol and metabolic responses to a cold challenge in mid-pregnancy, suggesting that their ability to adapt to cold challenges through some of the expected pathways was reduced.

text: Reduced Cortisol and Metabolic Responses of Thin Ewes to an Acute Cold Challenge in Mid-Pregnancy: Implications for Animal Physiology and Welfare Background: Low food availability leading to reductions in Body Condition Score (BCS; 0 indicates emaciation and 5 obesity) in sheep often coincides with low temperatures associated with the onset of winter in New Zealand. The ability to adapt to reductions in environmental temperature may be impaired in animals with low BCS, in particular during pregnancy when metabolic demand is higher. Here we assess whether BCS affects a pregnant animal’s ability to cope with cold challenges.

Methods: Eighteen pregnant ewes with a BCS of 2.760.1 were fed to attain low (LBC: BCS2.360.1), medium (MBC: BCS3.260.2) or high BCS (HBC: BCS3.660.2). Shorn ewes were exposed to a 6-h acute cold challenge in a climate-controlled room (wet and windy conditions, 4.460.1uC) in mid-pregnancy. Blood samples were collected during the BCS change phase, acute cold challenge and recovery phase.
Results: During the BCS change phase, plasma glucose and leptin concentrations declined while free fatty acids (FFA) increased in LBC compared to MBC (P,0.01, P,0.01 and P,0.05, respectively) and HBC ewes (P,0.05, P,0.01 and P,0.01, respectively). During the cold challenge, plasma cortisol concentrations were lower in LBC than MBC (P,0.05) and HBC ewes (P,0.05), and FFA and insulin concentrations were lower in LBC than HBC ewes (P,0.05 and P,0.001, respectively). Leptin concentrations declined in MBC and HBC ewes while remaining unchanged in LBC ewes (P,0.01). Glucose concentrations and internal body temperature (Tcore) increased in all treatments, although peak Tcore tended to be higher in HBC ewes (P,0.1). During the recovery phase, T4 concentrations were lower in LBC ewes (P,0.05).
Conclusion: Even though all ewes were able to increase Tcore and mobilize glucose, low BCS animals had considerably reduced cortisol and metabolic responses to a cold challenge in mid-pregnancy, suggesting that their ability to adapt to cold challenges through some of the expected pathways was reduced.

year: 2012

title: Carbon dynamics of a dairy pasture: annual balance and impact of cultivation

authors: Wallace, Dirk Fraser

subjects: Soil carbon

abstract: Maintenance of soil carbon (C) content is important because a relatively small percentage change in the global soil C store has the potential to cause a large change in atmospheric CO₂ concentration. Losses of soil C can also lead to a decline in soil quality and its capacity to be productive and carry out other services such as the filtering of pollutants. Globally, research on soil C dynamics has largely focused on forests, croplands and natural grasslands, while intensively grazed pasture has received much less attention. In New Zealand, the dynamics of soil C content and C cycling in intensively grazed dairy systems are poorly understood but large losses of soil C (1 t C ha⁻¹ yr⁻¹) have recently been reported for grazed dairy pastures.

The objective of this research was to build on current knowledge of the C balance of intensively grazed dairy farm systems. To achieve this objective, net ecosystem CO₂ exchange (NEE) and water use efficiency (WUE) were measured over intensively grazed dairy pasture using eddy covariance from 15 December 2007 to 15 December 2009. Net ecosystem carbon balances (NECB) were then calculated for 2008 & 2009 from NEE measurements combined with measurements and estimates of C imports (feed) and C exports (milk, silage, methane). A further objective was to determine the impact of periodic cultivation of contrasting soils on the C balance of a dairy farm. To achieve this objective, measurements of soil CO₂ emissions were made using the closed chamber technique following the cultivation of three paddocks of Horotiu soil (Typic Orthic Allophanic) and three paddocks of Te Kowhai soil (Typic Orthic Gley).

Annual NEE of the farm was -1,212 ± 500 kg C ha⁻¹ for 2008 and -2,280 ± 500 kg C ha⁻¹ for 2009. Including imports and exports of C to the farm resulted in an annual NECB of -199 ± 500 kg C ha⁻¹ and -1,014 ± 500 kg C ha⁻¹ for 2008 and 2009, respectively. Applied uncertainty is at 90% confidence bound and derived from previous studies reported in the literature. The site was a net sink of C during both 2008 and 2009 in agreement with EC studies performed over grasslands in Europe. The large difference in NEE and NECB between years was due to a drought in 2008, when the site was a C source for the first four months of this year. Average daily water use efficiency (WUE) for 2008 (4 g C kg⁻¹H₂O) and 2009 (4.2 g C kg⁻¹ H₂O) were not substantially different between years and agreed with international field and laboratory studies for pasture.

Soil CO₂  loss following cultivation was measured using the closed chamber technique. During the period of cultivation photosynthesis ceased, and potential C input (NEE) to pasture during this time was estimated at -750 kg C ha⁻¹from the adjacent EC study site. To calculate the maximum net soil CO₂₋C loss the potential C input from photosynthesis (NEE) must be added to measured CO₂ emissions. Total soil C loss from the Te Kowhai was between 2,880 kg C ha⁻¹ (CO₂ flux only) and 3,742 kg C ha⁻¹ (CO₂ flux + NEE) while the Horotiu soil lost between 2,082 kg C ha⁻¹(CO₂ flux only) and 2,944 kg C ha⁻¹ (CO₂ flux + NEE). The significant difference in C loss between the two soils was likely a result of their contrasting clay mineralogy and drainage. The Horotiu soil contains allophanic clays with a very high specific surface area, which protects soil C from decomposition. Additionally, poorly drained soils such as the Te Kowhai tend to lose more C following cultivation due to aeration caused by cultivation which increases oxygen penetration into the soil and accelerates decomposition of soil C.

Based on these results this grazed pasture was a net sink of C for 2008 and 2009 which is in contrast to the measured decline of 1 t C ha⁻¹ yr⁻¹ from New Zealand’s flat to rolling dairy pastures. Cultivation of dairy pasture soil resulted in net C losses, however, these losses were not large enough to account for the measured decline in soil C from New Zealand’s flat to rolling dairy pastures. Further research is required to investigate long term soil C recovery following initial cultivation of pasture in order to be confident of this conclusion.

text: Carbon dynamics of a dairy pasture: annual balance and impact of cultivation Maintenance of soil carbon (C) content is important because a relatively small percentage change in the global soil C store has the potential to cause a large change in atmospheric CO₂ concentration. Losses of soil C can also lead to a decline in soil quality and its capacity to be productive and carry out other services such as the filtering of pollutants. Globally, research on soil C dynamics has largely focused on forests, croplands and natural grasslands, while intensively grazed pasture has received much less attention. In New Zealand, the dynamics of soil C content and C cycling in intensively grazed dairy systems are poorly understood but large losses of soil C (1 t C ha⁻¹ yr⁻¹) have recently been reported for grazed dairy pastures.

The objective of this research was to build on current knowledge of the C balance of intensively grazed dairy farm systems. To achieve this objective, net ecosystem CO₂ exchange (NEE) and water use efficiency (WUE) were measured over intensively grazed dairy pasture using eddy covariance from 15 December 2007 to 15 December 2009. Net ecosystem carbon balances (NECB) were then calculated for 2008 & 2009 from NEE measurements combined with measurements and estimates of C imports (feed) and C exports (milk, silage, methane). A further objective was to determine the impact of periodic cultivation of contrasting soils on the C balance of a dairy farm. To achieve this objective, measurements of soil CO₂ emissions were made using the closed chamber technique following the cultivation of three paddocks of Horotiu soil (Typic Orthic Allophanic) and three paddocks of Te Kowhai soil (Typic Orthic Gley).

Annual NEE of the farm was -1,212 ± 500 kg C ha⁻¹ for 2008 and -2,280 ± 500 kg C ha⁻¹ for 2009. Including imports and exports of C to the farm resulted in an annual NECB of -199 ± 500 kg C ha⁻¹ and -1,014 ± 500 kg C ha⁻¹ for 2008 and 2009, respectively. Applied uncertainty is at 90% confidence bound and derived from previous studies reported in the literature. The site was a net sink of C during both 2008 and 2009 in agreement with EC studies performed over grasslands in Europe. The large difference in NEE and NECB between years was due to a drought in 2008, when the site was a C source for the first four months of this year. Average daily water use efficiency (WUE) for 2008 (4 g C kg⁻¹H₂O) and 2009 (4.2 g C kg⁻¹ H₂O) were not substantially different between years and agreed with international field and laboratory studies for pasture.

Soil CO₂  loss following cultivation was measured using the closed chamber technique. During the period of cultivation photosynthesis ceased, and potential C input (NEE) to pasture during this time was estimated at -750 kg C ha⁻¹from the adjacent EC study site. To calculate the maximum net soil CO₂₋C loss the potential C input from photosynthesis (NEE) must be added to measured CO₂ emissions. Total soil C loss from the Te Kowhai was between 2,880 kg C ha⁻¹ (CO₂ flux only) and 3,742 kg C ha⁻¹ (CO₂ flux + NEE) while the Horotiu soil lost between 2,082 kg C ha⁻¹(CO₂ flux only) and 2,944 kg C ha⁻¹ (CO₂ flux + NEE). The significant difference in C loss between the two soils was likely a result of their contrasting clay mineralogy and drainage. The Horotiu soil contains allophanic clays with a very high specific surface area, which protects soil C from decomposition. Additionally, poorly drained soils such as the Te Kowhai tend to lose more C following cultivation due to aeration caused by cultivation which increases oxygen penetration into the soil and accelerates decomposition of soil C.

Based on these results this grazed pasture was a net sink of C for 2008 and 2009 which is in contrast to the measured decline of 1 t C ha⁻¹ yr⁻¹ from New Zealand’s flat to rolling dairy pastures. Cultivation of dairy pasture soil resulted in net C losses, however, these losses were not large enough to account for the measured decline in soil C from New Zealand’s flat to rolling dairy pastures. Further research is required to investigate long term soil C recovery following initial cultivation of pasture in order to be confident of this conclusion.

year: 2010

title: He purapura whetū tō te whakataukī

authors: Tuahine, Hōhepa

subjects: Whakataukī

abstract: Ko te whakataukī he kōrero e whakaatu ana i ngā tini āhuatanga o te Māori me te āhua o tōna taiao (Milroy, 2004, wh. 38).  Hei tuinga ake, he kōrero e pupuri ana i ngā tohutohu e tau ai te noho o te tangata ki te whenua.  Ka rerekē te whakatakotoranga o te kupu o te whakataukī o nehe, ki te reo Māori o nāianei.  Ko ngā whakataukī o tāukiuki i titoa i te wā e ora tonu ana ngā whare wānanga o nehe me ōna tohunga.  Ka mutu, ko te reo me ōna kupu kei tērā taumata e rere ana.  Nō reira, he kōrero e whakaata ana i te ao Māori, ko ōna atua, ko ōna tikanga, ko ōna pakanga, ko ōna tātai whakapapa, ko ōna mātauranga, ko ōna tohutohu (Milroy, 2004, wh. 38).  Ka tākaitia ake aua mātauranga ki te kōrero poto noa iho, ka tuku iho ai ki ngā uri whakaheke.

text: He purapura whetū tō te whakataukī Ko te whakataukī he kōrero e whakaatu ana i ngā tini āhuatanga o te Māori me te āhua o tōna taiao (Milroy, 2004, wh. 38).  Hei tuinga ake, he kōrero e pupuri ana i ngā tohutohu e tau ai te noho o te tangata ki te whenua.  Ka rerekē te whakatakotoranga o te kupu o te whakataukī o nehe, ki te reo Māori o nāianei.  Ko ngā whakataukī o tāukiuki i titoa i te wā e ora tonu ana ngā whare wānanga o nehe me ōna tohunga.  Ka mutu, ko te reo me ōna kupu kei tērā taumata e rere ana.  Nō reira, he kōrero e whakaata ana i te ao Māori, ko ōna atua, ko ōna tikanga, ko ōna pakanga, ko ōna tātai whakapapa, ko ōna mātauranga, ko ōna tohutohu (Milroy, 2004, wh. 38).  Ka tākaitia ake aua mātauranga ki te kōrero poto noa iho, ka tuku iho ai ki ngā uri whakaheke.

year: 2016