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Islam M.R.,University of Sydney | Garcia S.C.,University of Sydney | Henry D.,Dairy Australia
Crop and Pasture Science | Year: 2011

This study was conducted to investigate the potentials of normalised difference vegetation index (NDVI), nitrogen (N) concentration (%), and N content (g/plant) of whole maize plant to estimate yield and nutritive value of hybrid forage maize. Hybrid forage maize was grown with two rates of pre-sowing fertiliser N (0, 135kg/ha) and three rates of post-sowing fertiliser N (0, 79, 158kgN/ha) applied at the six-leaf stage. Data on the NDVI and N (% and g/plant) of maize were collected at 2-, 3-, 6-, 8-, 12-, 16-, 18-leaf stages and at harvest. Metabolisable energy (ME) content of the whole maize plant at harvest was estimated from in vitro digestibility. Simple, polynomial, and multiple regression analyses were conducted and only the best-fit models were selected. The 8-leaf stage was found to be the most effective stage for use of the NDVI in predicting biomass yield (R2=0.81), grain yield (R 2=0.72), and N (%) (R2=0.92) of forage maize. Nitrogen (%) at the 8-leaf stage was also best related to biomass yield (R 2=0.88). Multiple regressions at the 3-leaf stage increased the coefficient of determination for both biomass yield and grain yield (R 2=0.77) over the relationships obtained from N (%) of the whole plant at 2- or 3-leaf stage. The NDVI and N (%) of the whole plant at 8-leaf stage were the best predictors of yield, but failed to predict ME content of the hybrid forage maize. Multiple regression models at the 3-leaf stage were almost as effective as the NDVI and N (%) of whole maize plant at the 8-leaf stage in predicting biomass and grain yield of forage maize. © CSIRO 2011.

Golder H.M.,University of Sydney | Lean I.J.,University of Sydney | Rabiee A.R.,University of Sydney | King R.,Dairy Australia | And 2 more authors.
Journal of Dairy Science | Year: 2013

Ruminal endotoxin and plasma oxidative stress biomarker concentrations were studied in dairy heifers challenged with grain, fructose, and histidine in a partial factorial study. Holstein-Friesian heifers [n=30; average body weight (BW) of 359.3±47.3kg] were randomly allocated to 5 treatment groups: (1) control (no grain); (2) grain [crushed triticale at 1.2% of BW dry matter intake (DMI)]; (3) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI); (4) grain (1.2% of BW DMI) + histidine (6g/head); and (5) grain (0.8% of BW DMI) + fructose (0.4% of BW DMI) + histidine (6g/head). Rumen samples were collected by stomach tube 5, 65, 115, 165, and 215min after diet consumption and blood samples at 5 and 215min after consumption. Rumen fluid was analyzed for endotoxin concentrations. Plasma was analyzed for concentrations of the following oxidative stress biomarkers: reactive oxygen metabolites (dROM), biological antioxidant potential (BAP), advanced oxidation protein products, and ceruloplasmin, and activity of glutathione peroxidase. Dietary treatment had no effect on concentrations of endotoxin or oxidative stress biomarkers. We observed no interactions of treatment by time. Ruminal concentrations of endotoxin decreased during the sampling period from 1.12×105 ± 0.06 to 0.92×105 endotoxin units/mL ± 0.05 (5 and 215min after diet consumption, respectively). Concentrations of dROM and the oxidative stress index (dROM/BAP × 100) increased over the sampling period, from 108.7 to 123.5 Carratelli units (Carr U), and from 4.1 to 4.8, respectively. Ceruloplasmin concentrations markedly declined 5min after the consumption of diets, from 190 to 90mg/L over the 215-min sampling period. Overall, a single feeding challenge for dairy cattle with grain, fructose, and histidine, and combinations thereof, may not be sufficient to induce marked changes in endotoxin or oxidative stress biomarker concentrations. © 2013 American Dairy Science Association.

Lean I.J.,University of Sydney | Golder H.M.,University of Sydney | Black J.L.,John L Black Consulting | King R.,Dairy Australia | Rabiee A.R.,University of Sydney
Journal of Animal Science | Year: 2013

Our objective was to evaluate a near-infrared reflectance spectroscopy (NIRS) used in the feed industry to estimate the potential for grains to increase the risk of ruminal acidosis. The existing NIRS calibration was developed from in sacco and in vitro measures in cattle and grain chemical composition measurements. To evaluate the existing model, 20 cultivars of 5 grain types were fed to 40 Holstein heifers using a grain challenge protocol and changes in rumen VFA, ammonia, lactic acids, and pH that are associated with acidosis were measured. A method development study was performed to determine a grain feeding rate sufficient to induce non-life threatening but substantial ruminal changes during grain challenge. Feeding grain at a rate of 1.2% of BW met these criteria, lowering rumen pH (P = 0.01) and increasing valerate (P < 0.01) and propionate concentrations (P = 0.01). Valerate was the most discriminatory measure indicating ruminal change during challenge. Heifers were assigned using a row by column design in an in vivo study to 1 of 20 grain cultivars and were reassigned after a 9 d period (n = 4 cattle/treatment). The test grains were dry rolled oats (n = 3), wheat (n = 6), barley (n = 4), triticale (n = 4), and sorghum (n = 3) cultivars. Cattle were adapted to the test grain and had ad libitum access to grass silage 11 d before the challenge. Feed was withheld for 14 h before challenge feeding with 0.3 kg DM of silage followed by the respective test grain fed at 1.2% of BW. A rumen sample was taken by stomach tube 5, 65, 110, 155, and 200 min after grain consumption. The rumen is not homogenous and samples of rumen fluid obtained by stomach tube will differ from those gained by other methods. Rumen pH was measured immediately; individual VFA, ammonia, and D-and L-lactate concentrations were analyzed later. Rumen pH (P = 0.002) and all concentrations of fermentation products differed among grains (P = 0.001). A previously defined discriminant score calculated at 200 min after challenge was used to rank grains for acidosis risk. A significant correlation between the discriminant score and the NIRS ranking (r = 0.731, P = 0.003) demonstrated the potential for using NIRS calibrations for predicting acidosis risk of grains in cattle. The overall rankings of grains for acidosis risk were wheat > triticale > barley > oats > sorghum. © 2013 American Society of Animal Science. All rights reserved.

Yin J.,Menzies Research Institute | Dwyer T.,Murdoch Childrens Research Institute | Riley M.,Dairy Australia | Cochrane J.,Menzies Research Institute | Jones G.,Menzies Research Institute
European Journal of Clinical Nutrition | Year: 2010

Background/Objectives: Fetal life may be a critical period for the development and/or programming of metabolic systems, including the skeleton. However, it is unclear on the association between maternal nutrition during pregnancy and bone mass in their offspring at adolescence.Subjects/Methods: This was a birth cohort study of 216 adolescents (16.2±0.4 years). Dietary intake was measured by food frequency questionnaire. Bone densitometry was measured at the femoral neck, lumbar spine and total body by DXA. Results: After adjustment for confounders, bone mineral density (BMD) of the femoral neck was positively associated with magnesium density and negatively associated with fat density (all P-values <0.05). BMD of the lumbar spine was positively associated with calcium, magnesium and phosphorus density and negatively associated with fat density (all P-values <0.05). Maternal milk intake was significantly positively associated with lumbar spine BMD. After considering all significant nutrients in the same model, fat density remained significant negatively for the femoral neck and lumbar spine, whereas magnesium density remained significant positively for the femoral neck. No nutrient was significant for the total body. Conclusions: Maternal intake of milk, fat and magnesium during the third trimester of pregnancy is predictive of BMD at age 16, suggesting that in utero diet influences peak bone mass possibly through programming bone responses. © 2010 Macmillan Publishers Limited All rights reserved.

Condron R.,Dairy Australia | Farrokh C.,CNIEL French Dairy Organisation | Jordan K.,Teagasc | McClure P.,Unilever | And 2 more authors.
International Journal of Food Microbiology | Year: 2015

Studies on the heat resistance of dairy pathogens are a vital part of assessing the safety of dairy products. However, harmonized methodology for the study of heat resistance of food pathogens is lacking, even though there is a need for such harmonized experimental design protocols and for harmonized validation procedures for heat treatment studies. Such an approach is of particular importance to allow international agreement on appropriate risk management of emerging potential hazards for human and animal health. This paper is working toward establishment of a harmonized protocol for the study of the heat resistance of pathogens, identifying critical issues for establishment of internationally agreed protocols, including a harmonized framework for reporting and interpretation of heat inactivation studies of potentially pathogenic microorganisms. © 2014 Elsevier B.V.

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