Dr JP Pienaar | Published May 1997, in Livestock Production Science, Volume 48, Issue 2, May 1997, p.117-127
Four indirect methods for estimating feed intake were compared with actually measured feed intake when intake was uninterrupted, and also when intakes were changed abruptly. Intakes were estimated from: marker infused into the rumen and collected at the abomasum of faeces, marker infused into the ileum and collected at the faeces, faeces collection using faecal bags and a method which does not use markers, but uses the kinetics of rumen digestion and passage. During uninterrupted intake all methods gave relatively accurate estimates of intake provided digestibility was estimated accurately. With abruptly changing intakes, longest delays were observed with the marker based methods. The faecal collection method and the method based on rumen digestion kinetics had the shortest delay before giving the same value as actually measured intake. It was concluded that with rapidly changing intakes, the indirect methods will lag behind actually measured intake by about two days.