@conference {41275,
	title = {Magnesium endogenous loss as a function of plasma magnesium concentration rather than a constant allows better development of magnesium models in ruminants},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {160-163},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {In the course of adapting an existing sheep model of magnesium metabolism for use with lactating dairy cattle it was found that the model failed to predict plasma magnesium concentrations in agreement with experimental data after scaling the model for animal size dependent parameters. An inspection of the model indicated that faecal endogenous Mg loss and Mg absorption from the hindgut were the model components requiring further development. Pooled data from Mg balance experiments were used to investigate the relationship between plasma Mg concentration, net faecal endogenous Mg loss and the apparent availability of magnesium. A mathematical relationship between Mg intake and faecal Mg output is presented. It was derived from the generalised non-linear case to allow for variability in both apparent absorption of Mg and faecal endogenous Mg loss. A balance trial simulation was carried out in which net faecal endogenous Mg was implemented as a linear function of plasma Mg concentration. The results of this simulation were in close agreement with the analysis of pooled balance trial data and suggest that net faecal endogenous Mg loss should be applied to the model as a function of plasma Mg concentration. In fact net faecal endogenous Mg loss is not useful in modelling since it is the net result of a true Mg secretion function being subject to reabsorption in distal regions of the tract. Post rumen magnesium exchanges are examined in the model by implementing net Mg exchanges in the small intestine and hindgut as separate secretion and absorption processes. The difficulties in isolating the true secretion and absorption functions in the hindgut are discussed in conjunction with an initial estimate of these functions. In the modified model the incorporation of a variable endogenous Mg secretion dependent on plasma magnesium concentration provides an additional mechanism for magnesium homeostasis which is sufficient to allow the model to scale between sheep and cattle. },
	issn = {1176-5283},
	author = {Bell ST and Laporte JA and Robson AB and Sykes AR}
}
@conference {40799,
	title = {Effects of potassium on potential difference across the rumen wall and magnesium metabolism in sheep},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {138-142},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Several in vitro studies have indicated that the potential difference  (p.d.) across the rumen wall is important for magnesium (Mg) absorption  and that increases in p.d. as a result of high rumen potassium (K)  concentration may reduce Mg transport. The aim of this work was to  provide quantitative data on the relationship between p.d. and Mg  absorption in the live animal and on diurnal variation in p.d. Twelve rumen cannulated ewes, weighing 45},
	issn = {1176-5283},
	author = {Wachirapakorn C and Sykes AR and Robson AB}
}
@conference {40798,
	title = {Magnesium metabolism in sheep subjected to sodium or water loading},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {133-137},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = { Six rumen-cannulated ewes, averaging 48},
	issn = {1176-5283},
	author = {Wachirapakorn C and Sykes AR and Robson AB}
}
@conference {40388,
	title = {Magnesium Solubility in the caecum in response to pH changes},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {52},
	year = {1992},
	month = {Jan},
	pages = {103-106},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {We examined the practicality of using a combination of protein  polymorphism and DNA fingerprinting to match up hinds and calves in nine  separate mating groups of red deer with between 8 and 21 progeny each.  Variation in 10 polymorphic proteins excluded 0.61 to 0.89 of the  possible dam-calf combinations in each sire group, leaving between 2 and  200 pedigree combinations per group to be solved by DNA fingerprinting.  Of the 44 sire-dam-calf combinations tested by DNA fingerprinting, 22  were excluded, while four calves matched the parents at all bands.  However, 16 pedigrees were equivocal, due to the fact that one or both  parents were not in a lane directly adjacent to the calf on the  fingerprinting gel. The low probability of exclusion of protein testing  in some sire groups, combined with the practical limitation of having to  run each possible pedigree combination side by side on DNA  fingerprinting gels, mean that the present techniques do not provide a  routine method for identifying the dam-calf pairings in red deer mating  groups on farms.  },
	issn = {1176-5283},
	author = {Dalley DE and Isherwood P and Sykes AR and Robson AB}
}
