The net energy value of artificially dried subterranean clover harvested before flowering

Abstract

Subterranean clover (Trifolium subterraneum L. cv. Clare) was harvested before flower emergence and dried rapidly without heating. Each of four adult sheep was given the dried clover at rates of 200, 600, 1000, and 1400 g/day in four successive fortnights and was finally fed ad libitum for 1 month. Energy, nitrogen, and carbon balances and body weight changes were measured. The fasting energy losses of the sheep were determined at the end of the experiment.

The hay contained approximately 27% crude protein, 14% crude fibre, and 3% lignin (dry matter basis) and was eaten avidly by the sheep. Voluntary consumption ranged from 1400 to 2100 g dry matter/day, and maximum balances were 2080 kcal and 17 g nitrogen/day.

Digestibility of energy was 78% at the lowest level of feeding and 74% at the highest. Cell wall and cell contents were respectively 74 and 82% digestible. Energy losses in methane were unusually low (7–11% of digestible energy) whereas losses in urine were unusually high (12–21%). The net result was that metabolizable energy was a lower fraction of digestible energy than for most forages, e.g, it was c. 77% at maintenance instead of the normal 82%. Net availability of metabolizable energy was 84% between fasting and half maintenance, 69% between fasting and maintenance, and 54% above maintenance.

The value of this clover per gram was in keeping with its chemical composition and digestibility; its exceptional value as a feed was due to the large amounts of digestible energy which the sheep took in when fed ad libitum.