The maintenance requirement for digestible organic matter of adult sheep has been derived by Wood and Capstick (1926) and more recently by Lang-lands, Corbett, McDonald and Pullar (1963) by means of regression analysis of data for feed intake, live-weight and live-weight gain.

As data from digestibility trials carried out both in Trinidad and Venezuela were available, similar equations were derived for adult male sheep under tropical conditions. Groups of six adult male sheep were housed individually and total collections of faeces and urine were made for periods of 10 days after preliminary periods of 7 or 10 days. The quantity of forage offered was generally that which the individual sheep would eat without leaving a large residue. The results obtained in these trials and a more detailed description of the methods used have been described elsewhere (Butterworth, 1963; 1965). In all, 178 sets of data were used. Each set for an individual animal consisted of daily intake of digestible organic matter (D), the mean (W) of initial and final body weights, and daily change in weight (G) all in lb. Values of D and G were means obtained from the results for the 10-dayperiod. The value of G was subject to high error in determination as periods were short and measurement of weight change in ruminant animals over short periods is most unreliable (see for example, Lush, Christensen, Wilson and Black, 1928; Whiteman, Chambers, Loggins, Pope and Stephens, 1954). Mean values and ranges of the values were as follows: D=0·96 lb. (0·46–1·87 lb.), W=84·2 lb. (56·0–149·0 lb.) and G=0·02 lb. (-0·5-+0·5 lb.). The digestibility coefficients for the dry matter of the various forages used ranged from 47·3 to 68·0%.