Despite the fact that the sulphur hexafluoride (SF6) tracer technique was developed over 25 years... more Despite the fact that the sulphur hexafluoride (SF6) tracer technique was developed over 25 years ago to measure methane production from grazing and non-housed animals, no studies have specifically investigated whether ambient wind speed, temperature, relative humidity and rainfall influence the accuracy of the method. The aim of this research was to investigate how these weather factors influence the measurement of enteric methane production by the SF6 technique. Six different cohorts of dairy cows (40 per cohort) were kept outdoors and fed a common diet during spring in 3 consecutive years. Methane production from individual cows was measured daily over the last 5 days of each 32-day period. An automated weather station measured air temperature, wind speed, relative humidity and rainfall every 10 min. Regression analyses were used to relate the average daily wind speed, average daily temperature, average daily relative humidity and total daily rainfall measurements to dry matter i...
Globally, annual production of grape marc (GM), the residue of skins, seeds and stems remaining a... more Globally, annual production of grape marc (GM), the residue of skins, seeds and stems remaining after making wine, has been estimated to be approximately nine million tonnes. No previous studies have compared effects on milk production and methane emissions when GM from either red or white grapes was fed to dairy cows. This experiment examines the effects of partial replacement of a perennial ryegrass (Lolium perenne L.) based diet with GM from either red or white grapes on yield and composition of milk and methane emissions. Thirty-two Holstein dairy cows in early lactation were offered either a control diet containing 15.0 kg dry matter (DM) of freshly harvested perennial ryegrass and 5.2 kg of a concentrate mix, or a diet similar to the control diet but with 5 kg DM of ryegrass replaced with 5 kg DM of GM from red grapes (RGM), or a diet similar to the RGM diet except the GM was from white grapes (WGM). Individual cow feed intakes, milk yields, and methane emissions were measured...
Many farmers in southern Victoria grow fodder turnips as a summer feed for lactating dairy cows. ... more Many farmers in southern Victoria grow fodder turnips as a summer feed for lactating dairy cows. This paper reports on 2 experiments that measured the milk yields and liveweight changes of cows offered a basal forage diet and combinations of turnips, barley and protein supplements (cottonseed meal or lupins). A stall feeding experiment was conducted over 26 days with 40 Friesian cows in mid lactation offered 1 of 5 dietary treatments. All cows were offered 10 kg DM/day of a basal diet comprising pasture, pasture hay and pasture silage which is similar to that available on many southern Victorian dairy farms during summer. Cows in a control group did not receive additional feed supplements. Cows in the other 4 groups were offered a supplement of 5 kg DM/cow.day of either turnips, barley or a mixture containing 3 kg DM/cow.day of turnips and 2.0 kg DM/cow.day of either crushed lupins or cottonseed meal. The marginal milk responses from barley, turnips, turnips + lupins and turnips + c...
Nine pasture soils from high rainfall zones of southern Victoria were analysed for a range of che... more Nine pasture soils from high rainfall zones of southern Victoria were analysed for a range of chemical and physical properties before receiving a single application of P fertiliser in the form of triple superphosphate (TSP), single superphosphate (SSP), or TSP and lime (5 t/ha) at amounts ranging from 0 to 280 kg P/ha. Soils were analysed for bicarbonate-extractable P concentration, using both the Olsen P and Colwell P methods, 6 and 12 months after fertiliser application. A strong positive linear relationship existed at all sites between the amount of P applied and both the Olsen P and Colwell P concentrations. The slopes of these relationships measured the change in extractable P concentration (Δ EP) per unit of P applied, whilst the inverse of the ΔEP value indicated the amount of P fertiliser required above maintenance to increase the extractable P concentration by 1 mg/kg. These values ranged from 5 to 15 kg P/ha, depending on soil type. The ΔEP measured by the Olsen (Δ EP Olse...
The yield and quality of perennial ryegrass, short-rotation ryegrass–perennial ryegrass mix, oats... more The yield and quality of perennial ryegrass, short-rotation ryegrass–perennial ryegrass mix, oats, millet, maize, rape, kale, pasja and turnips were determined over a 13-week summer period in 1995–96 and 1996–97. The experiment was conducted on the Elliott Research Station in north-western Tasmania (145˚E, 41˚S) and consisted of 2 irrigated and 2 dryland main plots. Within each main plot was a randomised complete block design with 9 forage crop subplots. Where forage is required through the summer, there is little advantage in establishing millet or oats over a spring-sown ryegrass pasture, mainly as the former still require replacement with permanent pasture in the autumn. However, if additional forage is required from late January then turnips are clearly superior to the other forages evaluated in all respects, apart from a low bulb crude protein (CP) content. Turnips responded significantly to irrigation, producing between 15 and 22 kg DM/ha.mm irrigation applied, with yields ran...
Water pollution is a major environmental problem worldwide. Tracing the source of contaminants in... more Water pollution is a major environmental problem worldwide. Tracing the source of contaminants in our water supplies is often the first step in taking effective remedial action. Organic chemicals can be used to trace the sources of contaminants such as sediments, agrochemicals and nutrients because living organisms, like their wastes and decomposition products, are chemically unique. Using chemical characteristics to
Efficient nutrient management is a critical component of profitable and sustainable milk producti... more Efficient nutrient management is a critical component of profitable and sustainable milk production on modern dairy farms. While manufactured fertilisers can be a large part of dairy farm operating costs, the net flux of nutrients onto farms in feed and fertiliser can be large, with increasing scrutiny of off-farm nutrient impacts. In this study, we examine soil phosphorus (P), potassium (K), and sulphur (S) concentrations on 2065 grazed dairy paddocks and animal containment areas on 43 contrasting dairy farms across Australia. These farms represent the broad range of Australian dairy farm operations, including geographic locations, milk production, herd and farm size, reliance on irrigation, and soil types. More than three quarters of the grazed paddocks sampled had available phosphorus (P), potassium (K) and sulphur (S) concentrations above agronomic requirements. An exception to this was paddocks sampled on organic dairy farms, which generally had lower soil P and S fertility, wi...
Fertilisers contribute to phosphorus (P) exported from agricultural catchments in south-eastern A... more Fertilisers contribute to phosphorus (P) exported from agricultural catchments in south-eastern Australia. Phosphorus concentrations were initially measured in overland flow caused by rainfall after broadcasting either single superphosphate [SSP, Ca(H2PO4)2] or diammonium phosphate [DAP, (NH4)2HPO4] blends to pastures. In addition, P concentrations in overland flow were measured at intervals down border irrigation bay before and after fertiliser application. The period between fertiliser application and irrigation varied from 1 to 10 days. For the rainfall-induced overland flow, total dissolved P (TDP) concentrations were higher where DAP rather than SSP had been applied. For the irrigation study, sampling position behind the wetting front, irrigation pre and post fertiliser application, and irrigation number post fertiliser application explained 49.7, 20.5, and 15.2% of the total sum of squares, respectively. TDP concentrations were highest in the wetting front and diminished with ...
It has been proposed that methane emissions from dairy cows could be predicted from the concentra... more It has been proposed that methane emissions from dairy cows could be predicted from the concentrations of specific milk fatty acids (Chilliard et al. 2009). The proposed relationships were developed from a corn silage and concentrate diet with an addition of one of whole linseed, extruded linseed or linseed oil. The relationships have been tested by others but only for cows fed total mixed rations incorporating a limited range of feed additives (Mohammed et al., 2011; Dijkstra et al., 2011). The aim of this work was to determine if fatty acid concentrations in milk could assist in the prediction of methane emission from dairy cows fed a range of diets.
The SF6 tracer technique which is used to estimate enteric methane emissions from ruminants requi... more The SF6 tracer technique which is used to estimate enteric methane emissions from ruminants requires knowledge of, or at least accurate prediction of, the rate of release of SF6 from permeation tubes (Williams et al. 2011). The rate of release of SF6 from permeation tubes is generally determined by placing them in an incubator set at 39ºC and the weight loss from individual tubes is monitored over a number of weeks (Lassey et al. 1997). Simple linear regression (zero order kinetics) of tube weight versus time has often been used for determining rate of release of SF6. However, Lassey et al. (1997) showed that the rate of release of SF6 from permeation tubes declines with time. To circumvent this problem, Lassey et al. (1997) recommended fitting a quadratic equation to the tube weight vs time data. However, we have noticed that the shape of the curve describing weight of SF6 remaining in the tube vs. time, is not parabolic (as described by a quadratic equation), but can more accurate...
This experiment measured milk production responses of grazing cows offered supplements in differe... more This experiment measured milk production responses of grazing cows offered supplements in different ways. Holstein-Friesian cows averaging 89 days in milk, were allocated into six groups of 36 (each group including three rumen-fistulated cows). Two groups were randomly assigned to each of three dietary treatments: (1) cows were offered milled barley grain twice daily at milking and pasture silage in the paddock (Control); (2) the same amounts of milled barley grain and pasture silage were fed as a partial mixed ration (PMR) once a day following morning milking (PMR1); and (3) cows were supplemented with a PMR containing milled barley grain, lucerne hay, maize silage and crushed maize grain fed once a day following morning milking (PMR2). All dietary treatments were formulated to provide the same metabolisable energy and cows were offered a restricted allowance of ~14 kg DM/cow.day (to ground level) of perennial ryegrass pasture in addition to their supplement. Each group of 36 cows ...
Milk production responses of grazing cows offered supplements in different ways were measured. Ho... more Milk production responses of grazing cows offered supplements in different ways were measured. Holstein-Friesian cows, averaging 227 d in milk, were allocated into 6 groups of 36, with 2 groups randomly assigned to each of 3 feeding strategies: (1) cows grazed perennial ryegrass pasture supplemented with milled barley grain fed in the milking parlor and pasture silage offered in the paddock (control); (2) same pasture and allotment supplemented with the same amounts of milled barley grain and pasture silage, but presented as a mixed ration after each milking (PMR 1); and (3) same pasture and allotment, supplemented with a mixed ration of milled barley grain, alfalfa hay, corn silage, and crushed corn grain (PMR 2). For all strategies, supplements provided the same metabolizable energy and grain:forage ratio. [75:25, dry matter (DM) basis]. Each group of 36 cows was further allocated into 4 groups of 9, which were assigned to receive 6, 8, 10, or 12 kg of supplement DM/cow per day. T...
Analysis of atherogenic risk factors in 493 Maltese-born residents of Melbourne showed that after... more Analysis of atherogenic risk factors in 493 Maltese-born residents of Melbourne showed that after adjustment for the effects of age, fasting plasma insulin was the only factor with a highly significant (p = less than 0.001) association with electrocardiogram abnormalities suggestive of atherosclerotic coronary artery disease. Absence of peripheral arterial pulses was not correlated with abnormal electrocardiogram but was significantly associated with both age and smoking. Elevation of plasma insulin appears to be a significant risk factor for atherosclerotic heart disease.
Late-lactation Holstein cows (n=144) that were offered 15kg dry matter (DM)/cow per day of perenn... more Late-lactation Holstein cows (n=144) that were offered 15kg dry matter (DM)/cow per day of perennial ryegrass to graze were randomized into 24 groups of 6. Each group contained a fistulated cow and groups were allocated to 1 of 3 feeding strategies: (1) control (10 groups): cows were fed crushed wheat grain twice daily in the milking parlor and ryegrass silage at pasture; (2) partial mixed ration (PMR; 10 groups): PMR that was isoenergetic to the control diet and fed twice daily on a feed pad; (3) PMR+canola (4 groups): a proportion of wheat in the PMR was replaced with canola meal to produce more estimated metabolizable protein than other groups. Supplements were fed to the control and PMR cows at 8, 10, 12, 14, or 16kg of DM/d, and to the PMR+canola cows at 14 or 16kg of DM/d. The PMR-fed cows had a lower incidence of ruminal acidosis compared with controls, and ruminal acidosis increased linearly and quadratically with supplement fed. Yield of milk fat was highest in the PMR+cano...
Dairy products are the single largest commodity exported from south east Australia. However, dair... more Dairy products are the single largest commodity exported from south east Australia. However, dairy farming contributes 12% of Australia's national greenhouse gas emissions. During the last nine years, the Australian Federal Government and the Victorian State Government have funded considerable research towards mitigating greenhouse gas emissions from the agricultural sector. This review examines the findings of that research which pertains to the Australian dairy industry. Calorimeter measurements of 220 cows show a linear increase in enteric methane to increasing feed intake, over a range of forage based diets, with an average enteric methane yield of 21.4 g CH 4 /kg DMI (n = 220, R 2 = 0.70). Adoption of this empirical methane yield, rather than the equation currently used in the Australian greenhouse gas inventory would reduce the methane emissions attributed to the Australian dairy industry by approximately 10%. Analysis of additional data showed that enteric methane yield d...
Organic marker compounds (biomarkers) can be used to identify the sources of waterborne pollutant... more Organic marker compounds (biomarkers) can be used to identify the sources of waterborne pollutants. This paper examines sterols and other alcohols in overland flow from pasture-based grazing systems, possible agricultural source materials and water extracts of these source materials as a preliminary step to developing chemical profiles that can be used for tracing pollutants. Analyses of plant material shows that
An experiment was conducted to quantify the changes in energy partitioning resulting from grain s... more An experiment was conducted to quantify the changes in energy partitioning resulting from grain supplementation in herbage-fed dairy cows at 4 stages during a 670-d lactation. The experiment used 16 lactating Holstein-Friesian cows, with a control and a grain treatment being randomly allocated to 8 cows each. During 4 measurement periods (each of 4 d in a metabolism stall and 3 d in an indirect calorimeter) beginning at approximately 110, 270, 450, and 560 d in milk (DIM), the energy balance of each cow was measured. Cows in both groups were individually offered freshly cut ryegrass pasture (Lolium hybridum L.) in periods 1 and 3 and ryegrass pasture silage and alfalfa (Medicago sativa L.) hay in periods 2 and 4. In all periods, cows in the grain group were offered an additional 4.4 to 5.0 kg of dry matter of cereal grain/cow per day. Adding grain to the diet increased yields of fat and protein and tended to increase yields of milk and lactose, but did not affect milk composition. Gross energy intake (GEI) declined as lactation progressed. Adding grain to the diet decreased the percentage of GEI in feces and urine, but the extent of these reductions did not change as lactation progressed. Adding grain to the diet similarly reduced the percentage of GEI lost to heat, but again the extent of the reduction remained similar as lactation progressed. The magnitude of the increase in milk energy resulting from grain supplementation did not change with advancing lactation, but tissue energy retention was greater in the first 300 DIM compared with after 300 DIM. For herbage-based diets, CH 4 emissions ranged from 6.2 to 7.6% of GEI, which corresponds to 24.0 to 25.8 g of CH 4 /kg of dry matter intake. For diets supplemented with cereal grains, CH 4 emissions ranged from 6.3 to 7.3% of GEI, which corresponds to 21.6 to 25.2 g of CH 4 /kg of dry matter intake. It was concluded that, for cows producing <24 kg of milk/d and consuming herbage-based diets supplemented with grain, the efficiency of utilizing the additional energy in the grain, as measured by the loss of energy in heat, and its partitioning to milk, did not change as lactation progressed from 110 to 560 DIM.
Despite the fact that the sulphur hexafluoride (SF6) tracer technique was developed over 25 years... more Despite the fact that the sulphur hexafluoride (SF6) tracer technique was developed over 25 years ago to measure methane production from grazing and non-housed animals, no studies have specifically investigated whether ambient wind speed, temperature, relative humidity and rainfall influence the accuracy of the method. The aim of this research was to investigate how these weather factors influence the measurement of enteric methane production by the SF6 technique. Six different cohorts of dairy cows (40 per cohort) were kept outdoors and fed a common diet during spring in 3 consecutive years. Methane production from individual cows was measured daily over the last 5 days of each 32-day period. An automated weather station measured air temperature, wind speed, relative humidity and rainfall every 10 min. Regression analyses were used to relate the average daily wind speed, average daily temperature, average daily relative humidity and total daily rainfall measurements to dry matter i...
Globally, annual production of grape marc (GM), the residue of skins, seeds and stems remaining a... more Globally, annual production of grape marc (GM), the residue of skins, seeds and stems remaining after making wine, has been estimated to be approximately nine million tonnes. No previous studies have compared effects on milk production and methane emissions when GM from either red or white grapes was fed to dairy cows. This experiment examines the effects of partial replacement of a perennial ryegrass (Lolium perenne L.) based diet with GM from either red or white grapes on yield and composition of milk and methane emissions. Thirty-two Holstein dairy cows in early lactation were offered either a control diet containing 15.0 kg dry matter (DM) of freshly harvested perennial ryegrass and 5.2 kg of a concentrate mix, or a diet similar to the control diet but with 5 kg DM of ryegrass replaced with 5 kg DM of GM from red grapes (RGM), or a diet similar to the RGM diet except the GM was from white grapes (WGM). Individual cow feed intakes, milk yields, and methane emissions were measured...
Many farmers in southern Victoria grow fodder turnips as a summer feed for lactating dairy cows. ... more Many farmers in southern Victoria grow fodder turnips as a summer feed for lactating dairy cows. This paper reports on 2 experiments that measured the milk yields and liveweight changes of cows offered a basal forage diet and combinations of turnips, barley and protein supplements (cottonseed meal or lupins). A stall feeding experiment was conducted over 26 days with 40 Friesian cows in mid lactation offered 1 of 5 dietary treatments. All cows were offered 10 kg DM/day of a basal diet comprising pasture, pasture hay and pasture silage which is similar to that available on many southern Victorian dairy farms during summer. Cows in a control group did not receive additional feed supplements. Cows in the other 4 groups were offered a supplement of 5 kg DM/cow.day of either turnips, barley or a mixture containing 3 kg DM/cow.day of turnips and 2.0 kg DM/cow.day of either crushed lupins or cottonseed meal. The marginal milk responses from barley, turnips, turnips + lupins and turnips + c...
Nine pasture soils from high rainfall zones of southern Victoria were analysed for a range of che... more Nine pasture soils from high rainfall zones of southern Victoria were analysed for a range of chemical and physical properties before receiving a single application of P fertiliser in the form of triple superphosphate (TSP), single superphosphate (SSP), or TSP and lime (5 t/ha) at amounts ranging from 0 to 280 kg P/ha. Soils were analysed for bicarbonate-extractable P concentration, using both the Olsen P and Colwell P methods, 6 and 12 months after fertiliser application. A strong positive linear relationship existed at all sites between the amount of P applied and both the Olsen P and Colwell P concentrations. The slopes of these relationships measured the change in extractable P concentration (Δ EP) per unit of P applied, whilst the inverse of the ΔEP value indicated the amount of P fertiliser required above maintenance to increase the extractable P concentration by 1 mg/kg. These values ranged from 5 to 15 kg P/ha, depending on soil type. The ΔEP measured by the Olsen (Δ EP Olse...
The yield and quality of perennial ryegrass, short-rotation ryegrass–perennial ryegrass mix, oats... more The yield and quality of perennial ryegrass, short-rotation ryegrass–perennial ryegrass mix, oats, millet, maize, rape, kale, pasja and turnips were determined over a 13-week summer period in 1995–96 and 1996–97. The experiment was conducted on the Elliott Research Station in north-western Tasmania (145˚E, 41˚S) and consisted of 2 irrigated and 2 dryland main plots. Within each main plot was a randomised complete block design with 9 forage crop subplots. Where forage is required through the summer, there is little advantage in establishing millet or oats over a spring-sown ryegrass pasture, mainly as the former still require replacement with permanent pasture in the autumn. However, if additional forage is required from late January then turnips are clearly superior to the other forages evaluated in all respects, apart from a low bulb crude protein (CP) content. Turnips responded significantly to irrigation, producing between 15 and 22 kg DM/ha.mm irrigation applied, with yields ran...
Water pollution is a major environmental problem worldwide. Tracing the source of contaminants in... more Water pollution is a major environmental problem worldwide. Tracing the source of contaminants in our water supplies is often the first step in taking effective remedial action. Organic chemicals can be used to trace the sources of contaminants such as sediments, agrochemicals and nutrients because living organisms, like their wastes and decomposition products, are chemically unique. Using chemical characteristics to
Efficient nutrient management is a critical component of profitable and sustainable milk producti... more Efficient nutrient management is a critical component of profitable and sustainable milk production on modern dairy farms. While manufactured fertilisers can be a large part of dairy farm operating costs, the net flux of nutrients onto farms in feed and fertiliser can be large, with increasing scrutiny of off-farm nutrient impacts. In this study, we examine soil phosphorus (P), potassium (K), and sulphur (S) concentrations on 2065 grazed dairy paddocks and animal containment areas on 43 contrasting dairy farms across Australia. These farms represent the broad range of Australian dairy farm operations, including geographic locations, milk production, herd and farm size, reliance on irrigation, and soil types. More than three quarters of the grazed paddocks sampled had available phosphorus (P), potassium (K) and sulphur (S) concentrations above agronomic requirements. An exception to this was paddocks sampled on organic dairy farms, which generally had lower soil P and S fertility, wi...
Fertilisers contribute to phosphorus (P) exported from agricultural catchments in south-eastern A... more Fertilisers contribute to phosphorus (P) exported from agricultural catchments in south-eastern Australia. Phosphorus concentrations were initially measured in overland flow caused by rainfall after broadcasting either single superphosphate [SSP, Ca(H2PO4)2] or diammonium phosphate [DAP, (NH4)2HPO4] blends to pastures. In addition, P concentrations in overland flow were measured at intervals down border irrigation bay before and after fertiliser application. The period between fertiliser application and irrigation varied from 1 to 10 days. For the rainfall-induced overland flow, total dissolved P (TDP) concentrations were higher where DAP rather than SSP had been applied. For the irrigation study, sampling position behind the wetting front, irrigation pre and post fertiliser application, and irrigation number post fertiliser application explained 49.7, 20.5, and 15.2% of the total sum of squares, respectively. TDP concentrations were highest in the wetting front and diminished with ...
It has been proposed that methane emissions from dairy cows could be predicted from the concentra... more It has been proposed that methane emissions from dairy cows could be predicted from the concentrations of specific milk fatty acids (Chilliard et al. 2009). The proposed relationships were developed from a corn silage and concentrate diet with an addition of one of whole linseed, extruded linseed or linseed oil. The relationships have been tested by others but only for cows fed total mixed rations incorporating a limited range of feed additives (Mohammed et al., 2011; Dijkstra et al., 2011). The aim of this work was to determine if fatty acid concentrations in milk could assist in the prediction of methane emission from dairy cows fed a range of diets.
The SF6 tracer technique which is used to estimate enteric methane emissions from ruminants requi... more The SF6 tracer technique which is used to estimate enteric methane emissions from ruminants requires knowledge of, or at least accurate prediction of, the rate of release of SF6 from permeation tubes (Williams et al. 2011). The rate of release of SF6 from permeation tubes is generally determined by placing them in an incubator set at 39ºC and the weight loss from individual tubes is monitored over a number of weeks (Lassey et al. 1997). Simple linear regression (zero order kinetics) of tube weight versus time has often been used for determining rate of release of SF6. However, Lassey et al. (1997) showed that the rate of release of SF6 from permeation tubes declines with time. To circumvent this problem, Lassey et al. (1997) recommended fitting a quadratic equation to the tube weight vs time data. However, we have noticed that the shape of the curve describing weight of SF6 remaining in the tube vs. time, is not parabolic (as described by a quadratic equation), but can more accurate...
This experiment measured milk production responses of grazing cows offered supplements in differe... more This experiment measured milk production responses of grazing cows offered supplements in different ways. Holstein-Friesian cows averaging 89 days in milk, were allocated into six groups of 36 (each group including three rumen-fistulated cows). Two groups were randomly assigned to each of three dietary treatments: (1) cows were offered milled barley grain twice daily at milking and pasture silage in the paddock (Control); (2) the same amounts of milled barley grain and pasture silage were fed as a partial mixed ration (PMR) once a day following morning milking (PMR1); and (3) cows were supplemented with a PMR containing milled barley grain, lucerne hay, maize silage and crushed maize grain fed once a day following morning milking (PMR2). All dietary treatments were formulated to provide the same metabolisable energy and cows were offered a restricted allowance of ~14 kg DM/cow.day (to ground level) of perennial ryegrass pasture in addition to their supplement. Each group of 36 cows ...
Milk production responses of grazing cows offered supplements in different ways were measured. Ho... more Milk production responses of grazing cows offered supplements in different ways were measured. Holstein-Friesian cows, averaging 227 d in milk, were allocated into 6 groups of 36, with 2 groups randomly assigned to each of 3 feeding strategies: (1) cows grazed perennial ryegrass pasture supplemented with milled barley grain fed in the milking parlor and pasture silage offered in the paddock (control); (2) same pasture and allotment supplemented with the same amounts of milled barley grain and pasture silage, but presented as a mixed ration after each milking (PMR 1); and (3) same pasture and allotment, supplemented with a mixed ration of milled barley grain, alfalfa hay, corn silage, and crushed corn grain (PMR 2). For all strategies, supplements provided the same metabolizable energy and grain:forage ratio. [75:25, dry matter (DM) basis]. Each group of 36 cows was further allocated into 4 groups of 9, which were assigned to receive 6, 8, 10, or 12 kg of supplement DM/cow per day. T...
Analysis of atherogenic risk factors in 493 Maltese-born residents of Melbourne showed that after... more Analysis of atherogenic risk factors in 493 Maltese-born residents of Melbourne showed that after adjustment for the effects of age, fasting plasma insulin was the only factor with a highly significant (p = less than 0.001) association with electrocardiogram abnormalities suggestive of atherosclerotic coronary artery disease. Absence of peripheral arterial pulses was not correlated with abnormal electrocardiogram but was significantly associated with both age and smoking. Elevation of plasma insulin appears to be a significant risk factor for atherosclerotic heart disease.
Late-lactation Holstein cows (n=144) that were offered 15kg dry matter (DM)/cow per day of perenn... more Late-lactation Holstein cows (n=144) that were offered 15kg dry matter (DM)/cow per day of perennial ryegrass to graze were randomized into 24 groups of 6. Each group contained a fistulated cow and groups were allocated to 1 of 3 feeding strategies: (1) control (10 groups): cows were fed crushed wheat grain twice daily in the milking parlor and ryegrass silage at pasture; (2) partial mixed ration (PMR; 10 groups): PMR that was isoenergetic to the control diet and fed twice daily on a feed pad; (3) PMR+canola (4 groups): a proportion of wheat in the PMR was replaced with canola meal to produce more estimated metabolizable protein than other groups. Supplements were fed to the control and PMR cows at 8, 10, 12, 14, or 16kg of DM/d, and to the PMR+canola cows at 14 or 16kg of DM/d. The PMR-fed cows had a lower incidence of ruminal acidosis compared with controls, and ruminal acidosis increased linearly and quadratically with supplement fed. Yield of milk fat was highest in the PMR+cano...
Dairy products are the single largest commodity exported from south east Australia. However, dair... more Dairy products are the single largest commodity exported from south east Australia. However, dairy farming contributes 12% of Australia's national greenhouse gas emissions. During the last nine years, the Australian Federal Government and the Victorian State Government have funded considerable research towards mitigating greenhouse gas emissions from the agricultural sector. This review examines the findings of that research which pertains to the Australian dairy industry. Calorimeter measurements of 220 cows show a linear increase in enteric methane to increasing feed intake, over a range of forage based diets, with an average enteric methane yield of 21.4 g CH 4 /kg DMI (n = 220, R 2 = 0.70). Adoption of this empirical methane yield, rather than the equation currently used in the Australian greenhouse gas inventory would reduce the methane emissions attributed to the Australian dairy industry by approximately 10%. Analysis of additional data showed that enteric methane yield d...
Organic marker compounds (biomarkers) can be used to identify the sources of waterborne pollutant... more Organic marker compounds (biomarkers) can be used to identify the sources of waterborne pollutants. This paper examines sterols and other alcohols in overland flow from pasture-based grazing systems, possible agricultural source materials and water extracts of these source materials as a preliminary step to developing chemical profiles that can be used for tracing pollutants. Analyses of plant material shows that
An experiment was conducted to quantify the changes in energy partitioning resulting from grain s... more An experiment was conducted to quantify the changes in energy partitioning resulting from grain supplementation in herbage-fed dairy cows at 4 stages during a 670-d lactation. The experiment used 16 lactating Holstein-Friesian cows, with a control and a grain treatment being randomly allocated to 8 cows each. During 4 measurement periods (each of 4 d in a metabolism stall and 3 d in an indirect calorimeter) beginning at approximately 110, 270, 450, and 560 d in milk (DIM), the energy balance of each cow was measured. Cows in both groups were individually offered freshly cut ryegrass pasture (Lolium hybridum L.) in periods 1 and 3 and ryegrass pasture silage and alfalfa (Medicago sativa L.) hay in periods 2 and 4. In all periods, cows in the grain group were offered an additional 4.4 to 5.0 kg of dry matter of cereal grain/cow per day. Adding grain to the diet increased yields of fat and protein and tended to increase yields of milk and lactose, but did not affect milk composition. Gross energy intake (GEI) declined as lactation progressed. Adding grain to the diet decreased the percentage of GEI in feces and urine, but the extent of these reductions did not change as lactation progressed. Adding grain to the diet similarly reduced the percentage of GEI lost to heat, but again the extent of the reduction remained similar as lactation progressed. The magnitude of the increase in milk energy resulting from grain supplementation did not change with advancing lactation, but tissue energy retention was greater in the first 300 DIM compared with after 300 DIM. For herbage-based diets, CH 4 emissions ranged from 6.2 to 7.6% of GEI, which corresponds to 24.0 to 25.8 g of CH 4 /kg of dry matter intake. For diets supplemented with cereal grains, CH 4 emissions ranged from 6.3 to 7.3% of GEI, which corresponds to 21.6 to 25.2 g of CH 4 /kg of dry matter intake. It was concluded that, for cows producing <24 kg of milk/d and consuming herbage-based diets supplemented with grain, the efficiency of utilizing the additional energy in the grain, as measured by the loss of energy in heat, and its partitioning to milk, did not change as lactation progressed from 110 to 560 DIM.
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