title: A study of the digestion and metabolism of dairy cows differing in susceptibility to bloat

authors: Carruthers, Vicki Robin

abstract: The digestive characteristics of cows of high (HS) or low (LS) susceptibility to bloat were investigated. 

Sixteen HS and 16 LS cows were offered pasture or hay when pregnant but not lactating, and pasture or 75% pasture plus 25% hay when lactating. The susceptibility groups did not differ in voluntary intake or apparent digestibility of dry matter, organic matter, nitrogen or energy on either occasion. LS cows produced more milk of a lower protein content than HS cows but yields of fat, protein and lactose were similar for both susceptibility groups.

Subsequent experiments used 4 or 5 cows of each susceptibility group, each fitted with a fistula in the dorsal rumen and offered diets of hay or pasture.

On 3 of 8 diets offered, non-lactating LS cows had less digesta, measured by removal through the fistula, in the reticulo-rumen before feeding than did HS cows. Increasing or decreasing the quantity of digesta in the reticulo-rumen after feeding correspondingly increased or decreased both the quantity of digesta subsequently lost and the quantity remaining 21 hours after feeding, or before the next feeding, for both HS and LS cows. On all diets LS cows lost less fluid from the reticulo-rumen during feeding and more after feeding, than did HS cows. Altering the concentration of Na in rumen fluid by addition of water or electrolyte solutions did not affect the loss of fluid and DM from the reticulo-rumen of LS cows relative to that of HS cows. When offered 3 pastures differing in maturity, an increase in maturity of the pasture resulted in an increase in the quantity of digesta in the reticulo-rumen before feeding, but HS and LS cows did not differ in quantity of digesta on each of the 3 pastures. The quantity of digesta in the reticulo-rumen was greater in cows when offered a diet of low K:Na ratio than when offered a high ratio diet. On both diets, however, LS cows had less digesta in the reticulo-rumen, a lower concentration of K in plasma and excreted less K in their faeces than HS cows.

Lactating HS and LS cows offered pasture ad libitum did not differ in intakes of dry matter and water, in the quantities of fluid and dry matter in the reticulo-rumen or in the rate of digestion when estimated from the loss of dry matter from nylon bags incubated in the ventral sac of the rumen.

HS and LS cows did not differ in capacity of the reticule-rumen. The rumen fluid dilution rate, estimated using Cr EDTA, was similar for both susceptibility groups in 3 experiments and higher for LS than HS cows in one experiment.

Overall, these studies revealed few differences between HS and LS cows in the parameters measured, except that under some experimental conditions LS cows had less digesta in the reticulo-rumen than did HS cows.

text: A study of the digestion and metabolism of dairy cows differing in susceptibility to bloat The digestive characteristics of cows of high (HS) or low (LS) susceptibility to bloat were investigated. 

Sixteen HS and 16 LS cows were offered pasture or hay when pregnant but not lactating, and pasture or 75% pasture plus 25% hay when lactating. The susceptibility groups did not differ in voluntary intake or apparent digestibility of dry matter, organic matter, nitrogen or energy on either occasion. LS cows produced more milk of a lower protein content than HS cows but yields of fat, protein and lactose were similar for both susceptibility groups.

Subsequent experiments used 4 or 5 cows of each susceptibility group, each fitted with a fistula in the dorsal rumen and offered diets of hay or pasture.

On 3 of 8 diets offered, non-lactating LS cows had less digesta, measured by removal through the fistula, in the reticulo-rumen before feeding than did HS cows. Increasing or decreasing the quantity of digesta in the reticulo-rumen after feeding correspondingly increased or decreased both the quantity of digesta subsequently lost and the quantity remaining 21 hours after feeding, or before the next feeding, for both HS and LS cows. On all diets LS cows lost less fluid from the reticulo-rumen during feeding and more after feeding, than did HS cows. Altering the concentration of Na in rumen fluid by addition of water or electrolyte solutions did not affect the loss of fluid and DM from the reticulo-rumen of LS cows relative to that of HS cows. When offered 3 pastures differing in maturity, an increase in maturity of the pasture resulted in an increase in the quantity of digesta in the reticulo-rumen before feeding, but HS and LS cows did not differ in quantity of digesta on each of the 3 pastures. The quantity of digesta in the reticulo-rumen was greater in cows when offered a diet of low K:Na ratio than when offered a high ratio diet. On both diets, however, LS cows had less digesta in the reticulo-rumen, a lower concentration of K in plasma and excreted less K in their faeces than HS cows.

Lactating HS and LS cows offered pasture ad libitum did not differ in intakes of dry matter and water, in the quantities of fluid and dry matter in the reticulo-rumen or in the rate of digestion when estimated from the loss of dry matter from nylon bags incubated in the ventral sac of the rumen.

HS and LS cows did not differ in capacity of the reticule-rumen. The rumen fluid dilution rate, estimated using Cr EDTA, was similar for both susceptibility groups in 3 experiments and higher for LS than HS cows in one experiment.

Overall, these studies revealed few differences between HS and LS cows in the parameters measured, except that under some experimental conditions LS cows had less digesta in the reticulo-rumen than did HS cows.

year: 1986

title: Australia: A land of missed opportunities?

authors: Greasley, David

abstract: Comprehensive Investment (CI) may provide an indicator of future changes in a country's per capita consumption. The authors explore the utility of the CI indicator for Australia by constructing CI data since 1861 and by estimating their relationship with changes in future consumption over periods of 50 years ahead. The CI measures include changes in natural, produced and human capital, and make allowance for exogenous technological progress. The results are used to consider how Australia's natural capital exploitation influenced the consumption of future generations. Further, the authors gauge if low CI relative to other leading OECD countries resulted in lower consumption levels in Australia over time than feasible, had it saved more.

text: Australia: A land of missed opportunities? Comprehensive Investment (CI) may provide an indicator of future changes in a country's per capita consumption. The authors explore the utility of the CI indicator for Australia by constructing CI data since 1861 and by estimating their relationship with changes in future consumption over periods of 50 years ahead. The CI measures include changes in natural, produced and human capital, and make allowance for exogenous technological progress. The results are used to consider how Australia's natural capital exploitation influenced the consumption of future generations. Further, the authors gauge if low CI relative to other leading OECD countries resulted in lower consumption levels in Australia over time than feasible, had it saved more.

year: 2017

title: How differing methods of ascribing ethnicity and socio-economic status affect risk estimates for hospitalisation with infectious disease

authors: Hobbs, Mark R.

subjects: Ethnicity/race

abstract: Significant ethnic and socio-economic disparities exist in infectious diseases (IDs) rates in New Zealand, so accurate measures of these characteristics are required. This study compared methods of ascribing ethnicity and socio-economic status. Children in the Growing Up in New Zealand longitudinal cohort were ascribed to self-prioritised, total response and single-combined ethnic groups. Socio-economic status was measured using household income, and both census-derived and survey-derived deprivation indices. Rates of ID hospitalisation were compared using linked administrative data. Self-prioritised ethnicity was simplest to use. Total response accounted for mixed ethnicity and allowed overlap between groups. Single combined ethnicity required aggregation of small groups to maintain power but offered greater detail. Regardless of the method used, Māori and Pacific children, and children in the most socio-economically deprived households had a greater risk of ID hospitalisation. Risk differences between self-prioritised and total response methods were not significant for Māori and Pacific children but single-combined ethnicity revealed a diversity of risk within these groups. Household income was affected by non-random missing data. The census derived deprivation index offered a high level of completeness with some risk of multicollinearity and concerns regarding the ecological fallacy. The survey-derived index required extra questions but was acceptable to participants and provided individualised data. Based on these results, the use of single-combined ethnicity and an individualised survey-derived index of deprivation are recommended where sample size and data structure allow it.

text: How differing methods of ascribing ethnicity and socio-economic status affect risk estimates for hospitalisation with infectious disease Significant ethnic and socio-economic disparities exist in infectious diseases (IDs) rates in New Zealand, so accurate measures of these characteristics are required. This study compared methods of ascribing ethnicity and socio-economic status. Children in the Growing Up in New Zealand longitudinal cohort were ascribed to self-prioritised, total response and single-combined ethnic groups. Socio-economic status was measured using household income, and both census-derived and survey-derived deprivation indices. Rates of ID hospitalisation were compared using linked administrative data. Self-prioritised ethnicity was simplest to use. Total response accounted for mixed ethnicity and allowed overlap between groups. Single combined ethnicity required aggregation of small groups to maintain power but offered greater detail. Regardless of the method used, Māori and Pacific children, and children in the most socio-economically deprived households had a greater risk of ID hospitalisation. Risk differences between self-prioritised and total response methods were not significant for Māori and Pacific children but single-combined ethnicity revealed a diversity of risk within these groups. Household income was affected by non-random missing data. The census derived deprivation index offered a high level of completeness with some risk of multicollinearity and concerns regarding the ecological fallacy. The survey-derived index required extra questions but was acceptable to participants and provided individualised data. Based on these results, the use of single-combined ethnicity and an individualised survey-derived index of deprivation are recommended where sample size and data structure allow it.

year: 2019