Keith Betteridge

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Strong-cation-exchange, solid-phase extraction of pyrrolizidine alkaloids and their N-oxides from honey samples was followed by reduction of the N-oxides and subsequent analysis of total pyrrolizidine alkaloids using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry. A limited survey of 63 preprocessing(More)
A method for analyzing honey samples was developed that enabled the simultaneous detection and identification of pyrrolizidine alkaloids and their N-oxides. Honey samples were treated with methanol or dilute sulfuric acid and then centrifuged to remove insoluble material. Subsequent strong cation exchange, solid-phase extraction of the supernatant provided(More)
BACKGROUND The main source of nitrogen (N) leaching from grazed pastures is animal urine with a high N deposition rate (i.e. per urine patch), particularly between late summer and early winter. Salt is a potential mitigation option as a diuretic to induce greater drinking-water intake, increase urination frequency, decrease urine N concentration and urine N(More)
Forty-eight Friesian or Friesian-X factory supply dairy cows were divided into two groups. Group 1 received a supplement of sodiumtripolyphosphate (TPP, 25g P, 25g Na/cow/day), and group 2 a supplement of sodium chloride (25g Na/cow/day). Supplementation began at peak lactation, when the mean serum inorganic phosphorus (Pi) of all cows was 1.13 mmol/l.(More)
A newly developed enzyme-linked immunosorbent assay (ELISA) was applied for studying H-Y antigen in buffaloes, cattle, horses and humans. A monoclonal H-Y antibody was absorbed with cells from males or females and was then tested against fluid samples known to contain soluble H-Y antigen. In this system, positive absorption manifested itself by a fall in(More)
Serum inorganic phosphorus (Pi) concentration of 20 cows in each of ten factory supply dairy herds was assessed at monthly or two-monthly intervals during the 198243 lactation. Pasture on offer was ranked low, medium or high and the phosphorus (P) content assessed monthly on all farms from the two paddocks to be grazed next in the rotation. The mean serum(More)
New Zealand dairy farmers are facing increasing pressure to reduce nutrient losses from grazing ruminants to the environment. Research suggests that the major source of nutrient loss is animal excreta which, for nitrogen (N), relates to cattle urine in particular. Most models used to describe N cycling and predict loss assume homogeneous distribution of(More)
Serum inorganic phosphorus (Pi) and calcium (Ca) concentrations were assessed in 20 cows on each of four Manawatu factory supply dairy farms. Blood was taken from each cow before calving and at six-week intervals during lactation. Bleeding coincided with herd testing. Herds of Friesian or Friesian X cows and Jersey or Jersey X cows were compared on adjacent(More)