Long- and short-term effects on intake of pelleting a roughage for sheep

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Abstract
1. Four groups of eight castrated male lambs, weighing initially about 37 kg, were fed ad libitum for 18 weeks on: C, chopped dried grass throughout; P, pelleted grass throughout; C/P (or P/C), the two forms alternated every 3 weeks; or C + P, both forms on offer.2. Daily dry-matter intake (g/kg W0·75) was 58·2 for treatment C and 814 for treatment P; thus the long-term difference in intake was 40%. However, in the alternated sheep, dry-matter intake was 53·6 g/kg W0·75 for chopped grass and 86·5 g for pelleted; this short-term difference (61%) was significantly greater than the long-term difference. Dry-matter intake for treatment C+P was 84·9 g/kg W0·75; after the first week, chopped grass comprised only 10% of this. Dry-matter digestibility coefficients (%) were: C, 740; P, 61·4 and C+P, 62·0.3. The sheep were killed in week 19 and the dimensions of digestive organs and their contents were adjusted to an animal of 50 kg empty body weight. The weight of the reticulo-rumen was greater for C (1·30 kg) than for P (0·94) or C+ P (1·05), C/P and P/C being inter-mediate (1·15). The water-filled volume of the rumen was proportional to weight, except that C/P (alternated sheep finishing on pelleted grass) had low volumes. Reticulo-rumen fill was greater for C (7·28 kg) than for P (3·97) or C+ P (4·53), P/C (5·90) and C/P (4·34) being intermediate. There were no other significant differences in organs or contents.4. Gains in empty-body weight (g/day) were: C, 112; P, 181; C/P and P/C, 126; C + P, 195.