Twenty-four individually housed male pigs (6.6 kg) were used in a pilot study to validate two trivalent metal markers, one in the feed and the other dosed orally to piglets, for the estimation of voluntary feed intake. Pigs were randomly assigned to one of three oral dosing treatments using 15 mg lanthanum oxide/day as the internal marker: once daily, twice daily, or 3 times daily. Piglets were offered a diet containing 1 g/kg of yttrium as the external marker. After a 7-day adaptation period, total faecal collection was made for the next 3 days. The first faecal sample voided after 1000 h was considered as the ‘grab sample’, to allow comparison of the technique with total collection. Intake of diets was recorded daily, and compared to feed intake using the ratio of the markers in the faeces. Daily samples were analysed for marker concentrations and a mean of the three-day data was used for regression analysis. Total collection data demonstrated that the accuracy of the estimation using the trivalent metals depended on the frequency of oral marker administration, as the estimation principle relies on the continual flow of a known amount of marker in the gastrointestinal tract (GIT). Nevertheless and using total collection, dosing the oral marker 3 times a day estimated individual feed intake with reasonable accuracy. In contrast, the ‘grab sampling’ technique reduced the accuracy of estimation, indicating that continual flow of the oral marker in the GIT is required for such a method. In conclusion, there is some potential in using trivalent metal markers to quantitatively estimate the feed intake of an individual pig, however the level of accuracy requires improvement.

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