1. A series of nitrogen-balance trials was done using groups of four animals of various species of wild and domesticated ruminants using pelleted diets (Arman & Hopcraft, 1975)

2. Various herbivores were given grass or grass hays, legumes, herbs and shrubs. Food and faecal samples were analysed for N

3. With the pelleted diets, the N content of the faecal dry matter (DM) was low for eland (Taurotragus oryx Pallas), high for sheep and cattle (Bos taurus and Bos indicus) and intermediate for the three small antelope species (hartebeest (Alcelaphus buselaphus cokei Günther), Thomson's gazelle (Gazella thomsonii Günther) and duiker (Sylvicapra grimmia L.)). With the natural fodders, similar relationships were found, together with variations associated with the type of diet

4. Three forms of equation were used to express the relationship between faecal N and food N. One of the forms, the linear regression of g faecal N/kg DM intake v. g food N/kg DM intake, fitted the results less well than did the other two and was not used to estimate metabolic faecal N (MFN) losses

5. MFN was calculated by extrapolation of linear regressions of g faecal N/kg faecal DM v. g N intake/kg faecal DM for the pelleted diets. The range of values was (g N/kg faecal DM): Friesians 7·6, eland 8·1, zebu cattle 11·0 and small antelope and sheep 11·5–12·6. There were significant differences (P < 0·001) between species in slopes and intercepts

6. MFN was calculated from linear regressions of g faecal N/kg faecal DM v. g food N/kg food DM for all diets. This method gave the best fit for the pelleted diets. Values for these diets were (g N/kg faecal DM): eland 8·3, cattle and sheep 9·3–11·0 and small antelope 11·6–12·3. Species differences were significant (P < 0·001). With grasses, values ranged from 5·9 for non-ruminants (rabbit (domesticated), warthog (Phacochoerus aethiopicus Pallas) and hippopotamus (Hippopotamus amphibius L.)) plus eland and wildebeest (Connochaetes taurinus Burchell), to 8·4 for the other ruminants (sheep, goat, hartebeest, gazelle, duiker, buffalo (Syncerus caffer Sparrman)), kob (Adenota kob thomasi Sclater), reedbuck (Redunca redunca Pallas) and topi (Damaliscus korrigum Ogilby). For ruminants (sheep, hartebeest, duiker and kob), excluding eland, given legumes the value was 8·6, and for sheep and duiker given herbs the value was 14·7. With shrubs, faecal-N losses were variable and sometimes high

7. With the pelleted diets, true digestibilities of crude protein (N×6·25) varied from 0·84 to 0·91

8. The results are discussed in relation to the digestive physiology and feeding habits of the various species, and there is an examination of the feasibility of using linear regressions of crude protein in the diet v. N in the faecal DM for evaluating the quality of the diets selected by free-ranging East African herbivores.

1. Four rumen-cannulated sheep were given a forage mixture (F) of chopped hay–ground, pelleted, dried grass (92:8, w/w) and two concentrate mixtures (C and S) of ground barley–ground hay–flaked maize (46:24:30 and 56:24:20, by wt respectively) in twenty-four hourly meals each day. Each of the diets was offered in successive periods of 16 d to give a feeding sequence F–S–C–S for one pair of sheep and C–S–F–S for the other pair.

2. The average composition (mol/100 mol) of the mixture of short-chain fatty acids, acetic, propionic and butyric, in the rumen was respectively 70·1, 18·5 and 7·5 with diet F, and 55·8, 24·8 and 13·6 with diet C. With diet S, the pattern of fermentation varied both between animals and in the same animal for different periods having either ‘high’(28–39 mol/100 mol) or ‘low’(16–21 mol/100 mol) proportions of propionic acid. On average when diet S followed diet F there was less propionic acid in the fermentation mixture than when diet S followed diet C (59·3 acetic, 22·2 propionic and 14·I butyric as compared with 52·7, 29·4 and 13·I respectively) but this trend was not significant and there was evidence of interactions between the feeding sequences and the individual sheep.

3. The mean concentrations of ammonia, sodium, potassium and chloride were similar for all diets but the pH and concentrations of calcium, magnesium and phosphorus tended to be higher and the buffering capacity lower for diet F than for diets C or S. In animals receiving diet S there was no relationship between the concentrations of minerals, the pH or buffering capacity and the pattern of fermentation except for ammonia, the concentration of which was high when the molar proportion of propionic acid was low.

4. Rumen volume, outflow rate and clearance rate, determined using polyethylene glycol, were higher for diet F than for diets C and S but within each diet, particularly for diet S, values varied considerably between sheep and between periods.

5. There was evidence of an interrelationship between the molar proportion of propionic acid in the fermentation products and the clearance rate, which indicated that the clearance rate may be an important factor influencing the pattern of fermentation in the rumen.

1. The deposition of fat and protein and the utilization of energy by growing rats offered diets ad lib. or in controlled amounts by gastric intubation has been investigated. Diets contained 50, 75, 100 or 200 g protein/kg, mainly as casein

Gain of body-weight and protein increased with increasing dietary protein concentration when animals received the same energy intake, although the reverse was true for fat deposition. However, the differences in live-weight gain were almost entirely due to changes in body water. The dry-matter content of the gain in animals given low-protein diets was 770 g/kg compared to 360 g/kg in those given the control diet

2. Energy retention was unaffected by dietary protein level in groups given the same energy intake by gastric intubation. In Expt 1 daily heat production increased significantly (P < 0·05) with increasing protein level (50, 75 and 200 g protein/kg diet) when energy intake was constant, but in Expt 2 there was no significant effect of protein level (50, 100 and 200 g protein/kg diet). Problems arose in the selection of a suitable basis for comparison of heat production between groups because of the differences in body-weight and body composition

3. The energy requirement for zero energy balance was approximately 10% lower for the low-protein groups than for those given the diet containing 200 g protein/kg when food intake was just above the maintenance level. When the requirement was expressed per unit metabolic body size (W0·75 kg) dietary protein level had no significant effect. The mean values for Expts 1 and 2 were 452 and 436 kJ respectively

4. The energy cost of weight gain increased as dietary protein level decreased in pairs of groups gaining at the same rate. The extra energy ingested by the animals given the lower protein level was converted to body tissue with an efficiency of at least 0·70

5. Striking differences were observed in body composition and energy retention of the two pairs of groups used for the comparison of tube-feeding and ad lib. feeding. With the diet containing 50 g protein/kg, tube-fed rats gained significantly more weight (P < 0·01) and more fat, dry matter and energy (P < 0·001) than their ad lib. counterparts given an iso-energetic intake

6. The results demonstrate that dietary protein level has little or no effect on the utilization of energy by growing rats when the pattern of intake is controlled by gastric intubation.

1. Rats were fed for 8 weeks on one of five diets differing in the amount of fatty acids 18:1, 18:2 and 18:3. Lipolysis, in vitro, of epididymal fat from fed and fasted rats was measured both basally and in the presence of noradrenaline with and without prostaglandin E1

2. Lipolysis was markedly influenced by the type of dietary fat. In particular, lipolysis in adipose tissue from rats given diets rich in the fatty acid 18:3 was higher than in the rats given diets containing 18:2

3. Results showing the effects of fasting on adipose tissue lipolysis are also presented

4. The results are discussed in relation to the known effects of unsaturated fats on hyper-plasia and protein synthesis in adipose tissue and on the possible role of prostaglandins.