Calf milk pasteurization
In the ongoing quest for improved biosecurity and maximum dairy herd health, it stands to reason that pasteurizing calf milk would be a worthwhile and beneficial management practice. Yet in reality, conservative industry estimates indicate that far fewer than half of all dairies currently perform any type of heat treatment on waste milk fed to calves. Is calf milk pasteurization effective? Does it address current disease and biosecurity concerns on the average dairy? And if so, what role can dairy practitioners play in promoting its adoption?
Pasteurization of discard mycoplasma mastitic milk used to feed calves: thermal effects on various mycoplasma.
Discard milk from sick or antibiotic-treated cows is often used as an economical alternative to milk replacer at dairy farms. This practice poses a health risk to calves if the discard milk is from cows with mycoplasma mastitis. Mycoplasma bovis, Mycoplasma californicum, and Mycoplasma canadense are among the agents known to cause contagious mastitis in cattle and occasionally pneumonia, otitis media, or arthritis in calves. This report describes a recent outbreak of calf polyarthritis and respiratory disease on a midwest dairy farm. The farm fed discard mycoplasma mastitic milk to its calves. On-the-farm pasteurization of the discard milk to 65 degrees C for 1 h before feeding prevented additional illness in the calves. Discard milk samples were collected before and after heating and tested for mycoplasma by culture. Only samples collected before pasteurization yielded live cultures. Common mastitic mycoplasma agents were also tested for sensitivity to heat. It was determined that 65 degrees C killed M. bovis and M. californicum after 2 min of exposure, while M. canadense remained viable for up to 10 min. Exposure to 70 degrees C inactivated M. bovis and M. californicum after 1 min, but M. canadense samples were positive for up to 3 min. Thus, M. canadense appears to be more heat resistant than M. bovis and M. californicum. Heat treatment that results in the destruction of M. canadense should be used for the pasteurization of discard mycoplasma mastitic milk.
MAS-NMR spectroscopy studies in the setting reaction of glass ionomer cements.
OBJECTIVES
The main objective is the characterisation of the setting reaction in glass ionomer cements based on experimental ionomer glasses with different fluorine content and a commercial glass ionomer cement liquid by using 13C CP/MAS-NMR, 29Si, 27Al and 31P MAS-NMR spectroscopy in order to receive information specifically about the cross-linking process.


METHODS
Different fluorine containing glass compositions based on 4.5SiO2-3Al2O3-1.5P2O5-(5-z)CaO-zCaF(2) where z=0-3, were mixed with a commercially available polymer liquid to form glass ionomer cements. The cements were subjected to 27Al, 13C CP/MAS, 29Si, and 31P MAS-NMR analysis.


RESULTS
The 27Al spectra showed clearly the formation of six-fold coordinate Al(VI), that may crosslink the carboxyl groups in the poly-acid molecules. A shift towards to more positive values of the carboxyl peak in the 13C CP/MAS-NMR spectra showed clearly the proton dissociation of the carboxyl groups. A shift towards more negative values was observed in the 29Si MAS-NMR spectra, suggesting formation of hydrated silica gel and consequently formation of additional Si-O-Si bonds. 31P MAS-NMR spectra also reflected changes in the coordination state around a PO4(3-) tetrahedron. Increasing the fluorine content of the glasses resulted generally in increased reactivity during setting, due to promoting cross-linking and repolymerisation of the silicate phase, followed by clear changes in the MAS-NMR spectra.


CONCLUSIONS
The cross-linking process during the setting reaction of glass ionomer cements can be followed by MAS-NMR spectroscopy observing the conversion of Al(IV) to Al(VI). The acid base setting reaction is completed in 1 day and no further significant changes in the MAS-NMR spectra can be observed. Further study is required in order to understand the role of phosphorus.