Method 101b Feeding of ytterbium marked feed and faecal collection and preparation

Procedure. Depending on the diet allocation, weigh an appropriate quantity of the remainder of the marked feed and feed to the specified animal before its normal feed, ensuring all the marked feed has first been consumed. This could be at 21.30 h on the Monday of the collection week. Collect faeces samples 1.5 h before the first feed, then after 8 h, 12 h, and 18 h, and then at 2-h intervals until 01.30 h on Thursday, and at approximately 4-h intervals until 21.30 h Friday. A final sample is taken at 11.30 h on Saturday.

Collect the faeces from the stable floor at the above times, place in a tared bucket and calculate the total weight of faeces. Thoroughly mix and transfer an approximately 200 g subsample to a labelled grip-top polythene bag, and place in a deep freeze. The rest is transferred to the dustbin allocated to the particular animal. Remove the sample from the deep-freeze and allow to partially thaw. Take a 10 g aliquot for determination of DM by drying to constant weight at 60°C. This is subsequently milled to 1 mm and transferred to a sample tube before preparation for Yb analysis. Take a further 100 g portion and freeze dry, then mill to 1 mm and store in an airtight container. Weigh a 10 g sample for determination of DM in the freeze-dried material at the same time as weighing aliquots for determination of nutrient components, e.g. ADF, NDF and CP (crude protein) as required. The bulked faeces may also be similarly prepared for analysis.

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