A comparison of five methods that estimate meal criteria for cattle

III data collected for feeding behaviour analysis, feeding events are gener ally separated by many very short to very long intervals during which no fe eding occurs. When feeding is clustered in bouts, a meal criterion (that is the longest ton-feeding interval accepted as part of a meal) must be estim ated before events can be grouped into meals. Until recently, three methods that estimate quantitative meal criteria were available. These methods con sist of fitting a 'broken-stick' (two straight intersecting lines, both wit h a negative slope) to the frequency distribution (method 1), the log(e)-tr ansformed cumulative frequency distribution (the log-survivorship curve; me thod 2) or the log(e)-transformed frequency distribution (method 3) of inte rvals between events. Recently, new methods have been proposed that fit eit her two (method 4) or three (method 5) Gaussians to the frequency distribut ion of log,transformed interval length (log-normal models). We compare the estimates obtained with these five methods when applied to a data set of 79 575 intervals between visits to food dispensers. These were recorded with 1 6 lactating cows during an average period of 156.6 (s.d. 51.5) days per cow . Meal criteria were estimated as 1.9, 6.0, 7.5, 32.4 and 49.1 min by metho ds I to 5, respectively. Estimated daily number of meals ranged from 5.7 to 12.1 per cow and estimated average meal size from 4.0 to 8.4 kg. The obser ved probabilities of cows initiating feeding in relation to time since feed ing last showed best agreement with the predictions of the log-normal model s. We conclude that the first three methods do not, while log-normal models do, have an adequate biological basis for a clear interpretation of the es timated meal criteria. Log-normal models are, therefore, the most promising for estimating meal criteria in cattle and probably iii other species as w ell.