title: The Breakdown of Skeletal Muscle in Dairy Cows During Peak Lactation

authors: Gray, Tarra Stacee

subjects: dairy cows

abstract: The decline in fertility in dairy cows is of international concern. Since 1950, milk production demands have increased while first service rates of conception have decreased. It is unclear why fertility has decreased, however current dairy management practice requires cows to be kept on a tight yearly calving schedule to ensure maximum milk production over the lifetime of the cow. The current postulate suggests that this regime places a high metabolic burden on the cows, which in turn requires the breakdown of tissues such as fat and muscle to provide substrates to meet the increased energy demands of lactation.

Immediately after calving, dairy cows enter a state of negative energy balance (EB), as they cannot consume enough energy to sustain lactation. During this period of negative EB, fat is mobilised in the form of non-esterified fatty acids to help supply the body with the extra energy it needs, but fat mobilisation decreases after four weeks while cows remain in a state of negative EB for several more weeks. It is unclear whether or not muscle breakdown occurs and plays a role in the restoration of EB in lactating cows during peak lactation. I hypothesized that the breakdown of muscle does occur in cows during peak lactation, and that it occurs to a greater extent in cows producing higher amounts of milk.

Dairy cows from three strains, NZL, NZH and OSH, representing cows with differing milk production abilities (low, intermediate and high, respectively), were studied for 12 weeks postpartum. Blood was drawn at weekly intervals and muscle biopsies taken at -1, 1, 4, 8, and 12 weeks postpartum.

Analysis of plasma revealed an increase in the abundance of troponin I-fs (a marker of muscle breakdown) over the period of study, suggesting that breakdown of skeletal muscle was occurring. Real-time polymerase chain reaction analysis showed that expression of the ubiquitin-proteasome (UbP) ligases atrogin-1 (atro1) and muscle ring finger protein 1 (murf1) increased initially, but returned to normal levels by four weeks postpartum. Concentration of mRNA of the lysosomal proteases, cathepsin B, D, H and L, did not change over the period of study. Therefore, the UbP pathway may contribute to the breakdown of muscle detected by troponin I-fs in plasma.

Proteins involved in translation initiation were examined by Western blotting. The ratio of phosphorylated over total eIF2alpha and 4E-BP1 remained unchanged throughout the study, indicating that the breakdown of muscle was not a result of decreased protein synthesis. However, there was a greater ratio of phosphorylated to total eIF2alpha in NZL cows compared with NZH and OSH, suggesting that protein synthesis was less overall in NZL cows than other strains. Measurement of myosin heavy chain composition indicated there was no change in the abundance of type I and type IIx muscle fibres and plasma myostatin levels did not change over the period of study. However, the OSH cows had less myostatin in their plasma than the NZL and NZH cows, suggesting that there may be inhibition of muscle growth occurring in this strain.

The results of this study suggest that breakdown of muscle could be important in restoring the EB in high-producing dairy cows during peak lactation. Upregulation of the UbP pathway during the first four weeks of lactation may contribute to this muscle breakdown. However, it remains unclear what processes then continue to regulate breakdown of skeletal muscle to maintain the elevated abundance of troponin I-fs in plasma from four to 12 weeks postpartum in lactating dairy cows.

text: The Breakdown of Skeletal Muscle in Dairy Cows During Peak Lactation The decline in fertility in dairy cows is of international concern. Since 1950, milk production demands have increased while first service rates of conception have decreased. It is unclear why fertility has decreased, however current dairy management practice requires cows to be kept on a tight yearly calving schedule to ensure maximum milk production over the lifetime of the cow. The current postulate suggests that this regime places a high metabolic burden on the cows, which in turn requires the breakdown of tissues such as fat and muscle to provide substrates to meet the increased energy demands of lactation.

Immediately after calving, dairy cows enter a state of negative energy balance (EB), as they cannot consume enough energy to sustain lactation. During this period of negative EB, fat is mobilised in the form of non-esterified fatty acids to help supply the body with the extra energy it needs, but fat mobilisation decreases after four weeks while cows remain in a state of negative EB for several more weeks. It is unclear whether or not muscle breakdown occurs and plays a role in the restoration of EB in lactating cows during peak lactation. I hypothesized that the breakdown of muscle does occur in cows during peak lactation, and that it occurs to a greater extent in cows producing higher amounts of milk.

Dairy cows from three strains, NZL, NZH and OSH, representing cows with differing milk production abilities (low, intermediate and high, respectively), were studied for 12 weeks postpartum. Blood was drawn at weekly intervals and muscle biopsies taken at -1, 1, 4, 8, and 12 weeks postpartum.

Analysis of plasma revealed an increase in the abundance of troponin I-fs (a marker of muscle breakdown) over the period of study, suggesting that breakdown of skeletal muscle was occurring. Real-time polymerase chain reaction analysis showed that expression of the ubiquitin-proteasome (UbP) ligases atrogin-1 (atro1) and muscle ring finger protein 1 (murf1) increased initially, but returned to normal levels by four weeks postpartum. Concentration of mRNA of the lysosomal proteases, cathepsin B, D, H and L, did not change over the period of study. Therefore, the UbP pathway may contribute to the breakdown of muscle detected by troponin I-fs in plasma.

Proteins involved in translation initiation were examined by Western blotting. The ratio of phosphorylated over total eIF2alpha and 4E-BP1 remained unchanged throughout the study, indicating that the breakdown of muscle was not a result of decreased protein synthesis. However, there was a greater ratio of phosphorylated to total eIF2alpha in NZL cows compared with NZH and OSH, suggesting that protein synthesis was less overall in NZL cows than other strains. Measurement of myosin heavy chain composition indicated there was no change in the abundance of type I and type IIx muscle fibres and plasma myostatin levels did not change over the period of study. However, the OSH cows had less myostatin in their plasma than the NZL and NZH cows, suggesting that there may be inhibition of muscle growth occurring in this strain.

The results of this study suggest that breakdown of muscle could be important in restoring the EB in high-producing dairy cows during peak lactation. Upregulation of the UbP pathway during the first four weeks of lactation may contribute to this muscle breakdown. However, it remains unclear what processes then continue to regulate breakdown of skeletal muscle to maintain the elevated abundance of troponin I-fs in plasma from four to 12 weeks postpartum in lactating dairy cows.

year: 2008

title: Integrated Model Development for the Assessment of Food Security in China Related to Climate Change and Adaptation

authors: Wang, Meng

subjects: Climate Change

abstract: This thesis developed a practical methodological framework, which integrated the bio-physical and socio-economic processes within the food system across different scales. The framework provides a useful tool for the assessment of food security and possible adaptation related to climate change. It was applied in China, a country with rapid economic growth and a large population, in order to evaluate multiple dimensions of food security related to climate change and socio-economic development in the future. 

In the framework, an improved bio-physical crop model was coupled with an improved food economic model by scaling up from the farm level to the national level. The bio-physical crop model was developed from the site-based Decision Support System for Agrotechnology Transfer (DSSAT) model in order to investigate the impacts of climate change on physical production of a crop only related to environmental factors. The food economic model was developed from a partial equilibrium economic model, China's Agricultural Policy Simulation Model (CAPSiM). This was done in order to simulate the response of a socio-economic system to the negative consequences on a food economic system from the bio-physical change in crop production due to climate change.

Case studies of China and the Jilin province were investigated by applying the framework. The impacts of climate change on yield and phenology of maize under multiple greenhouse gas emission scenarios were studied at provincial and national levels in three time periods, 2020s, 2050s, 2070s, using the improved bio-physical crop model. In general, maize yield reduction due to climate change ranges from -3% in 2020 to -14% in 2070. The worst yield is -20.5% in 2070 produced under the A1FI scenario. Food security for China until 2050 was projected under multiple climate change and socio-economic scenarios by using the food economic model, and analyzed with respect to food availability, food price and the system resilience to sudden disasters. Modelled climate change impacts on food availability in this study are minimal, producing only a 23 Mt (~8%) gap between supply and demand for maize by 2050. The socio-economic system will compensate for the impacts of climate change on the self-sufficiency of grains by about 8% of total production for the whole country. The impacts on single grain would cause the prices of other grains to rise in future. The effectiveness of potential adaptation measures was assessed quantitatively at both farm and national levels. Uncertainties among different scenarios are discussed for China and the Jilin province.

text: Integrated Model Development for the Assessment of Food Security in China Related to Climate Change and Adaptation This thesis developed a practical methodological framework, which integrated the bio-physical and socio-economic processes within the food system across different scales. The framework provides a useful tool for the assessment of food security and possible adaptation related to climate change. It was applied in China, a country with rapid economic growth and a large population, in order to evaluate multiple dimensions of food security related to climate change and socio-economic development in the future. 

In the framework, an improved bio-physical crop model was coupled with an improved food economic model by scaling up from the farm level to the national level. The bio-physical crop model was developed from the site-based Decision Support System for Agrotechnology Transfer (DSSAT) model in order to investigate the impacts of climate change on physical production of a crop only related to environmental factors. The food economic model was developed from a partial equilibrium economic model, China's Agricultural Policy Simulation Model (CAPSiM). This was done in order to simulate the response of a socio-economic system to the negative consequences on a food economic system from the bio-physical change in crop production due to climate change.

Case studies of China and the Jilin province were investigated by applying the framework. The impacts of climate change on yield and phenology of maize under multiple greenhouse gas emission scenarios were studied at provincial and national levels in three time periods, 2020s, 2050s, 2070s, using the improved bio-physical crop model. In general, maize yield reduction due to climate change ranges from -3% in 2020 to -14% in 2070. The worst yield is -20.5% in 2070 produced under the A1FI scenario. Food security for China until 2050 was projected under multiple climate change and socio-economic scenarios by using the food economic model, and analyzed with respect to food availability, food price and the system resilience to sudden disasters. Modelled climate change impacts on food availability in this study are minimal, producing only a 23 Mt (~8%) gap between supply and demand for maize by 2050. The socio-economic system will compensate for the impacts of climate change on the self-sufficiency of grains by about 8% of total production for the whole country. The impacts on single grain would cause the prices of other grains to rise in future. The effectiveness of potential adaptation measures was assessed quantitatively at both farm and national levels. Uncertainties among different scenarios are discussed for China and the Jilin province.

year: 2014

title: The Te Kotahitanga Observation Tool: Development, use, reliability and validity.

authors: Berryman, Mere

subjects: chool reform

abstract: Te Kotahitanga is a New Zealand school reform project aimed at improving the pedagogical contexts in mainstream classrooms in which the indigenous Māori students have traditionally been marginalised. It does this by assisting teachers to implement an Effective Teaching Profile. Part of this process uses an observation tool to monitor the degree to which participating teachers are incorporating the interactions and relationships described in the Effective Teaching Profile into their day-to-day teaching. Given the central importance of these tasks, the Te Kotahitanga team undertook to test the observation tool for measurement reliability and validity. In order to undertake this study, the team conducted synchronous observations amongst trainers (the Professional Development Coordinator and Regional Coordinators) to ascertain their level of consistency when using the tool. The team then conducted synchronous observations between trainers and 38 in-school facilitators in the 12 schools involved in Phase 3 of the project. In total 41 teachers were observed and over 200 Māori students were involved in these observations. This study suggests that the tool can produce consistent and reliable results when observers have been effectively trained.

text: The Te Kotahitanga Observation Tool: Development, use, reliability and validity. Te Kotahitanga is a New Zealand school reform project aimed at improving the pedagogical contexts in mainstream classrooms in which the indigenous Māori students have traditionally been marginalised. It does this by assisting teachers to implement an Effective Teaching Profile. Part of this process uses an observation tool to monitor the degree to which participating teachers are incorporating the interactions and relationships described in the Effective Teaching Profile into their day-to-day teaching. Given the central importance of these tasks, the Te Kotahitanga team undertook to test the observation tool for measurement reliability and validity. In order to undertake this study, the team conducted synchronous observations amongst trainers (the Professional Development Coordinator and Regional Coordinators) to ascertain their level of consistency when using the tool. The team then conducted synchronous observations between trainers and 38 in-school facilitators in the 12 schools involved in Phase 3 of the project. In total 41 teachers were observed and over 200 Māori students were involved in these observations. This study suggests that the tool can produce consistent and reliable results when observers have been effectively trained.

year: 2011