Comparison of diet and faecal collection methods for assessment of seasonal variation in dry matter intake by sheep maintained on a Cenchrus ciliaris pasture

Four diet collection methods: clipping(C), mouth grab (MG), plucking (P) and oesophageal extrusa (OE) and two faecal output estimation methods: faecal bag (FB) and Cr2O3 marker (I) were compared to assess seasonal changes in nutrient composition of diet and dry matter intake of sheep on Cenchrus ciliaris pasture. Crude protein (CP) and lignin contents of OE were higher than C, MG and P during all the seasons. Fiber fractions were lowest in MG, highest in C and intermediate in OE and P methods. Pooled CP contents of diet samples declined (P < 0.01) from 12.7% in monsoon to 9.3 and 7.9% in winter and summer while ADF, cellulose and lignin increased from monsoon to summer. Clipped samples had lower hTDE ADF, cellulose, hemicellulose and gross energy digestibility compared to P, MG and OE methods in all the seasons. Nutrient digestibility declined from monsoon to winter and summer in all the diet samples collected by the four techniques. CP digestibility showed marked depression from 63.1% in monsoon to 44.1 and 14.4% in winter and summer. Faecal collection bag and Cr2O3 marker methods estimated similar faecal outputs in all the seasons. The OE method estimated a lower DM intake of the animals (mean 960 g/day) compared to C, P and MG methods (mean 1381 g/day). Animals consumed more dry matter during winter (mean 1706 g/day) than during monsoon and summer (mean 1030 g/day) seasons. It is concluded that diet sampling method and season had an influence on the estimated diet composition and DMI of sheep on semi-arid pastures. Both methods of faecal collection, however, estimated similar daily faecal output in sheep. (C) 1999 Elsevier Science B.V. All rights reserved.