A simplification of the deuterium oxide dilution technique using FT-IR analysis of plasma, for estimating piglet milk intake

Abstract

Previous studies estimating milk intake using deuterium oxide (D₂O) as a tracer have required sublimation of the sample fluid (usually plasma) to remove solids and retrieve total water. This procedure has been simplified by directly measuring the D₂O content of plasma with a Fourier transform-infrared (FT-IR) spectrometer, removing the requirement for sample sublimation. Comparisons of samples that were split and then analysed as water of sublimation and as total plasma were performed. It was found that the direct analysis of the plasma could be achieved without a loss in fidelity of the results (sublimated v. plasma, r² = 0·976;n = 26). Linearity of assay standards was very high (r² > 0·997). The modified technique was used to determine the milk intake by piglets from litters of 7 sows during established lactation (Days 10-15). Water turnover (WTO) was shown to be the primary point by which differences in the piglet milk intakes were influenced. Differences in the milk composition had minimal effect on the milk intake determinations. Milk intake by each piglet was shown to be strongly correlated to piglet growth (r² = 0·59, P < 0·01). The relationship between milk intake and piglet growth was even stronger when examined based on the data from all piglet litters (r² = 0·84, P < 0·01).