The effect of method of conserving grass herbage and the frequency of feeding on digestion in and passage from the rumen was studied in growing cattle. A single sward of perennial ryegrass (Lolium perenne cv. Endura) was cut on 1 d and conserved as silage or hay. These forages were offered as the only feed to twelve rumen-cannulated Friesian steers (average initial live weight (LW) 128 kg) either at a restricted level of intake (20 g dry matter (DM)/kg LW; Expt 1) or ad lib. (Expt 2). In Expt 1 the forages were offered either once or eight times daily. When fed once or eight times daily, in vivo digestibility of DM was very similar for hay and silage (0.771 and 0.783 respectively), while the fractional rate of digestion measured by incubation in Dacron bags was significantly (P < 0.05) higher for silage (0.069) than hay (0.057). The rate of passage of mordanted feed out of the rumen was significantly (P < 0.01) faster for silage when determined from concentrations of marker in the rumen (0.034 v. 0.028 /h). The volume of liquid in the rumen was lower (P < 0.01) for animals consuming silage (27.51) compared with hay (37.11), while the fractional rate of passage of liquid from the rumen was higher (0.141 v. 0.098 /h, P < 0.05). The volume of liquid in the rumen was also lower (P < 0.05) in steers offered feed eight times daily (29.51), compared with once daily (35.11), but frequency of feeding had no significant effect either on total digestibility or on rate of digestion in the rumen. The ad lib. intake of silage was significantly (P < 0.01) lower than that of hay (4.53 v. 5.16 kg DM/d) in Expt 2.

The influence of the method of conserving grass herbage and the frequency of feeding on eating behaviour, rumen motility and rumen fill was studied in growing steers. Silage and hay were offered to twelve rumen-cannulated Friesian steers (average initial live weight (LW) 128 kg) at a restricted level of intake (20 g dry matter (DM)/kg LW) either once or eight times daily. With once daily feeding, the daily intake of hay was consumed in a single large meal which lasted about 2 h, while silage was eaten in many small meals throughout the day. The proportion of the day spent ruminating was higher (0·39) for steers offered hay once daily than for those offered silage (0·28) or hay eight times per day (0·29). There was little effect of conservation method on frequency of rumen contraction, but contractile intensity (integration of frequency and amplitude) increased during the second half of the 24 h feeding cycle in steers offered hay either once daily or eight times daily, while the same effect was only observed when silage was offered once daily. Total daily contractile activity (the integration of the frequency and duration of myoelectric spike bursts) was significantly (P < 0·05) higher in steers offered hay, compared with silage, once daily. The mean weight of organic matter in the reticulo-rumen of steers offered hay was significantly higher than for silage both with once (1593 v. 1326 g organic matter (OM)/100 kg LW, P < 0·01) and eight (1367 v. 1160 g OM/100 kg LW, P < 0·05) times daily feeding. The proportion of the particulate pool which was present as small (< 1·2 mm) particles was always greater than 0·60.

The effect of the α2-adrenergic agonist, guanfacin, on the energy metabolism, feed intake and live weight (LW) change of steers was studied in three experiments. In the first, the metabolic rate of twelve steers was measured after a 72 h fast. The next day, after a 96 h fast, six steers were injected intramuscularly with 15 mg guanfacin in sterile saline (9 g sodium chloride/l) and six with sterile saline alone, and metabolic rate was measured again. Treatment significantly (P < 0.01) lowered metabolic rate by approximately 20% (53.9 v. 66.8 kJ/kg per d). In the second experiment twelve steers were fed on long-chopped, low-quality roughage (Pangola grass (Digitaria decumbens) hay) ad lib. for 6 weeks. Six steers were continuously infused through a jugular catheter with 15 mg guanfacin/d (about 40 μg/kg LW) in sterile saline. The other six served as controls. There was no significant effect of treatment on feed intake (g dry matter (DM)/kg LW) or the rate of LW loss. Treatment significantly (P < 0.05) increased the retention time of fluid (17.9 v. 22.1 h) in the alimentary tract. In the final experiment twenty-three steers were divided into four treatment groups and fed on long-chopped, low-quality roughage (Pangola hay). Treated animals were continuously infused with guanfacin at the rate of 20, 40 or 80 μg/kg LW per d. Control steers were not infused. At the end of the 6-week feeding period metabolic rate was measured after a 72 h fast. Regardless of dose, guanfacin significantly (P < 0.01) lowered metabolic rate. Feed intake was not significantly affected by treatment but the rate of LW loss was significantly (P < 0.05) less in treated steers.

The present experiment was designed to study the effects of factors likely to alter microbial purine yield from the rumen on urinary excretion of allantoin-nitrogen (UAN). Sixteen mature Clun Forest–Welsh crossbred wethers were used in a 2 × 2 × 2 × 2 factorial design to investigate the effects of (1) level of intake, (2) wheat: nutritionally improved straw (NIS) ratio, (3) sodium bicarbonate inclusion and (4) monensin inclusion on diet digestibilities, fractional outflow rates of solids and liquids from the rumen and urinary allantoin excretion. Each treatment occurred in each of two experimental periods. The treatments were designed to influence microbial purine yield via changes in rumen outflow rate and microbial maintenance coefficient. Increasing the proportion of NIS and increasing feeding level decreased digestibility and increased the fractional outflow rate of solids. Increasing the level of intake increased the fractional outflow rate of liquids. Urinary allantoin excretion (/kg live weight0.75 per d) was significantly increased by an increased proportion of wheat in the diet and increased level of intake, and significantly reduced by NaHCO3. There was a significant interaction effect such that increasing level of intake did not increase UAN with the high-NIS diet, despite an increased fractional outflow of solids from the rumen, in contrast to the increase observed with the high-wheat diet. Taken together with other observations it is suggested that high sodium concentrations in the diet reduce the efficiency of microbial synthesis, probably by increasing the energy cost of maintaining osmolarity. Monensin had no overall effect on UAN but there were significant interactions between monensin and dietary Na; the inhibitory effect of monensin on UAN was eliminated or reversed in the presence of added NaHCO3. This is consistent with theories that monensin increases the net influx of hydrogen ions into microbial cells and that this influx can be reduced by increased extracellular sodium ions.

Growing Friesian steers chronically catheterized in the anterior mesenteric and portal veins were used to study the influence of feeding with either a forage or forage–concentrate diet on nutrient utilization by mucosal tissue. When animals were consuming the forage–concentrate diet the molar proportion of propionate in rumen fluid was significantly increased, although production rate as measured by isotope dilution was not altered. Net rates of absorption of VFA into portal blood when compared with rumen production rates underlined the extent to which metabolism within mucosal tissue modifies the propionate supply to the liver. Net glucose utilization by splanchnic tissue was shown to be significantly lower on the forage–concentrate diet. There were no effects of diet on whole-body glucose turnover or on the proportion of glucose derived from propionate. Animals fed on the forage–concentrate diet had significantly lower concentrations of circulating essential amino acids, due mainly to a reduction in branched-chain amino acid levels. There was net absorption of all amino acids by animals on both diets except for glutamate, glutamine and taurine in forage-fed animals.

To test whether the glycaemic index is altered by the amount of carbohydrate, meals containing 25 and 50 g carbohydrate as white rice and white bread were taken by seven non-insulin-dependent diabetic subjects. The glycaemic indices to parboiled white rice corresponding to 25 and 50 g carbohydrate were similar, being 55 (SE 10) and 60 (SE 8) respectively. The incremental areas of blood glucose (above basal) to parboiled white rice were significantly lower than to white bread after both an amount corresponding to 25 g carbohydrate (85 (SE 24) mM × 180 min v. 181 (SE 55) mM × 180 min; P < 0.01) and to 50 g carbohydrate 226 (SE 29) mM × 180 min v. 423 (SE 76) mM × 180 min; P < 0.01). Similar insulin response areas to 25 g carbohydrate given as parboiled white rice and white bread were found, whereas 50 g carbohydrate as white bread caused a significantly higher insulin response area than parboiled white rice (P < 0.05).

In conclusion, the glycaemic index of parboiled white rice is not affected by the amount of carbohydrate ingested, at least under the present study conditions.

The objective of the present study was to characterize nutritionally esterase-1 (ES-1). For this purpose, the effects of replacement of dietary carbohydrates by isoenergetic amounts of either fat or protein on ES-1 activities of plasma and small intestine were studied in male rats. Purified diets differing in the amounts of maize starch plus dextrose, casein and various types of fat were used. Plasma and jejunal ES-1 activities were found to be increased with increasing fat intakes. As to the type of fat, increasing plasma ES-1 activities were induced by coconut fat, olive oil, maize oil and medium-chain triacylglycerols, in this order. Maize oil induced higher jejunal ES-1 activities than coconut fat and olive oil, but had similar effects to medium-chain triacylglycerols. Maize oil was more powerful in increasing plasma ES-1 activity than isoenergetic amounts of casein, but with respect to jejunal ES-1 activity these dietary components were equally effective. It is concluded that the amounts of fat and protein in the diet are important determinants of ES-1 activities in plasma and jejunum.

Protein degradation rates were assessed by the excretion of Nt-methylhistidine (NtMH) in four strains of mature chickens, two White Leghorns and two broilers (dwarf and normal), fed on diets containing two levels of dietary protein. Over 0.9 of labelled NtMH was recovered within 7 d of injection from three White Leghorn, three dwarf and three normal broiler males. Protein degradation, measured by NtMH output, was related to adult body-weight by the power 0.71 and strain intercepts were significantly different. Strain differences disappeared when the rate of output of NtMH per unit lean was evaluated. The rate of output of NtMH per unit muscle was higher in birds fed on a low-protein diet of 100 g crude protein (nitrogen x 6.25; CP)/kg compared with males fed on 150 g CP/kg. It was concluded that the lower rate of protein degradation in broiler compared with layer strains at young ages is related to increased adult body-weight in agreement with well-established biological principles.

Four experiments were conducted to compare different methods for estimating the availability of lysine in protein feeds. The same feeds were used in all experiments. In the first experiment the apparent digestibility of lysine to the ileum of growing pigs was found to be 0.92, 0.69, 0.73, 0.85, 0.84 and 0.97 for soya-bean meal, cottonseed meal 1, cottonseed meal 2, meat meal, sunflower meal and skim milk respectively. In the second experiment the utilization of lysine (relative to free lysine) for weight gain, as measured in weaner pigs, was found to be 0.68, 0.73, 0.81, 0.86 and 1.00 for cottonseed meal 1, cottonseed meal 2, meat meal, sunflower meal and skim milk respectively. In Expt 3 diets were formulated to contain soya-bean meal, sunflower meal or cottonseed meal 2 with the same available lysine content from the measurements made in Expts 1 and 2. The feed conversion ratios of weaner pigs given these diets were similar for the three sources of protein when the values were adjusted for the differences in digestible dry matter intake. In the fourth experiment isoenergetic and isonitrogenous diets were formulated with increasing amounts of lysine from synthetic lysine or cottonseed meal 2. The diets were given to weaner pigs and resulted in a curvilinear response to lysine particularly for the cottonseed meal, so that the availability of lysine in cottonseed meal was similar to that of synthetic lysine at low lysine intakes and much lower than synthetic lysine at higher lysine intakes. Possible reasons for the curvilinear responses are discussed.

Eleven fasted adult men consumed a chicken meat sandwich made with white or wholemeal bread, extrinsically labelled with 2 mg 67Zn, on two different occasions. Immediately after eating the sandwich they were given an intravenous injection of 1·5 mg 70Zn. True Zn absorption (which was approximately 7% higher than apparent absorption) was determined by the faecal balance technique by making an allowance for endogenous excretion from measurements of faecal excretion of 70Zn. There was no significant difference in mean true Zn absorption from the white or wholemeal bread sandwich, 33·6 and 25·4% respectively. It was concluded that the substitution of wholemeal for white bread does not reduce Zn absorption from meat-based sandwiches.

The first experiment was a central composite rotatable design with calculated calcium levels of 6.2, 7.0, 9.0, 11.0, and 11.8 g/kg diet and total phosphorus levels of 5.2, 6.0, 8.0, 10.0, and 10.8 g/kg diet (2.8 g phytin-P/kg by analysis). This design involved three replicates for each rotatable point and fifteen replicates of the central point. The second experiment was a 4 × 4 factorial design with calculated Ca levels of 8.0, 10.0, 12.0, and 14.0 g/kg diet and calculated total P levels of 7.0, 9.0, 11.0, and 13.0 g/kg diet (2.5 g phytin-P/kg by analysis). There were four replicates for each treatment. In both 16 d experiments maize–soya-bean diets were used and each replicate consisted of one pen containing 10-d-old broad-breasted, white tom turkeys. The Ca and total P requirements for optimum growth were estimated to be 12.5 and 10.0 g/kg diet respectively. Bone ash was adequate at these levels of Ca and total P, but maximum bone ash was not achieved until much higher levels of Ca and total P were employed. At the required levels of Ca and total P for growth the incidences of Ca- and P-deficiency rickets were very low. There were no treatment effects on feed efficiency. Increasing dietary Ca decreased the incidence of the Ca-deficiency lesion. There was a quadratic response due to dietary total P on both P-deficiency rickets and plasma dialysable P; intermediate levels of dietary P resulted in low incidence of the P-deficiency lesion and high levels of plasma dialysable P. There was a strong negative correlation between the incidence of P-deficiency rickets and plasma dialysable P. Percentage retention was very low at high levels of dietary P and low levels of Ca which corresponded with slightly higher P-deficiency rickets and low plasma dialysable P. No such obvious relationships existed between Ca retention, incidence of Ca-deficiency rickets, and plasma Ca. The incidence of tibial dyschondroplasia was very low in the present study. There were pronounced dietary treatment effects on phytin-P retention; at 14 d percentage phytin-P retention treatment means ranged from 18 to 46 in Expt 1 and from 0 to 40 in Expt 2 with the highest retention of phytin-P at low levels at both Ca and total P.

Calcium: Phosphorus: Phytin-phosphorus retention: Rickets: Tibial dyschondroplasia: Turkey

Iron speciation in rodent diet and rat gastrointestinal tract lumen during dietary digestion and absorption was investigated with a novel selective extraction technique. Five Fe fractions were identified, namely exchangeable (soluble in 1 M-magnesium chloride), carbonate-bound (soluble in mild acid), oxide-bound (soluble in hydroxylamine–acetic acid), organic-bound (soluble after treatment with peroxide in nitric acid) and residual. Fe from the pelleted diet was mobilized by rat stomach to the exchangeable fraction, then redistributed to the carbonate- and oxide-bound fractions on passage through the proximal small intestine. In vitro incubation of diet with hydrochloric acid failed to mimic the in vivo effect of the stomach. In vitro neutralization of stomach contents with bicarbonate was found to produce a similar effect on Fe speciation to that seen when diet passed the proximal small intestine in vivo. Comparison of 59Fe speciation in extrinsically labelled diet with endogenous Fe speciation showed that extrinsic labelling does not uniformly label all endogenous species. The experiments suggest that selective extraction may provide a useful approach to the study of Fe species present in diets, in vitro digestions and gastrointestinal contents.

Marginally vitamin C-deficient guinea-pigs treated with the diabetogenic agent streptozotocin were compared with those liberally supplied with vitamin C, for functional indices of vitamin C status, particularly in the eye lens. Weanling male Dunkin–Hartley guinea-pigs were fed on diets with 0.1 g vitamin C/kg (marginally deficient), or 5 g/kg (liberally supplied), and some received intraperitoneal streptozotocin (two doses of 150 mg/kg body-weight). About half the streptozotocin-treated animals had high urinary glucose following an oral glucose dose; these animals also grew more slowly than the others. At 4 months after streptozotocin the animals were killed for measurement of tissue vitamin C, glucose and sorbitol. Streptozotocin moderately increased the concentration of glucose in plasma, lens and aqueous humour. Lens sorbitol levels increased only in the group exposed to streptozotocin plus marginal vitamin C. There was a significant (P < 0.02) positive correlation between urinary glucose and lens sorbitol levels overall. Liberal vitamin C intake may thus counteract the effect of streptozotocin diabetes on lens sorbitol, suggesting a new function of vitamin C, possibly related to cataractogenesis and to the biochemical lesions associated with diabetes.

The α-tocopherol content of a number of different fetal, neonatal and maternal guinea-pig tissues was determined and compared with plasma and erythrocyte α-tocopherol values. During late gestation, the fetal liver appears to act as a storage site for α-tocopherol, the majority of which is released immediately following birth. In contrast, lung and brain vitamin E levels are relatively constant over the final period of gestation and during early neonatal life. The ontogeny of α-tocopherol in brain and lung was similar to that for erythrocytes while plasma α-tocopherol content varied considerably and did not accurately reflect tissue α-tocopherol status. Surprisingly, fetal and maternal lung α-tocopherol concentrations were similar at all time-points considered, whereas fetal liver α-tocopherol status was always considerably greater than maternal liver α-tocopherol content. These results, if representative of the human fetus, suggest that preterm infants may not have tissue α-tocopherol concentrations as low as previously assumed and that during the perinatal period erythrocyte α-tocopherol content is a more accurate indicator of tissue α-tocopherol concentration than plasma α-tocopherol content.

The present study was undertaken to explore the effect of apple pulp on weight and composition of faeces. This material is rich in dietary fibre (DF;620 g dry matter/kg) and contains appreciable amounts of polyphenols. Recent reports indicate that both condensed tannins (CT) and soluble polyphenols form cross-links with protein and inhibit digestive enzymes, affecting the protein digestibility, and may produce a stimulation of endogenous nitrogen excretion. Two groups of male Wistar rats were fed on either a control diet free of DF or a diet containing 100 g apple pulp DF/kg during 7 d after a 4 d adaptation period. Body-weight and food intake were monitored daily and faeces and urine were collected once daily. DF, water content and polyphenolic compounds were measured in faeces, and N content in both faeces and urine. Faecal weight increased in the fibre group by 280 and 240% when compared with wet and dry faecal weights of animals fed on the fibre-free diet. Soluble dietary fibre (SDF) excreted in faeces was 10.9% of the SDF ingested, which suggested a low resistance to fermentation of this fraction. Of the insoluble DF, 43% of the ingested fibre was fermented. Polyphenols were degraded in the intestinal tract. Of the ingested CT, 68.6% was recovered in faeces, while the soluble polyphenols were extensively degraded (85.7% of that ingested). On the other hand, a higher faecal N excretion was observed for the fibre-fed group, suggesting a decrease in the digestibility of the dietary protein and lower apparent digestibility and N balance indices.

Rats were fed on four semi-purified diets in which raw or cooked peas (Pisum sativum var. Sentinel) provided 250 or 500 g/kg diet. Pressure-cooking of peas followed by rapid freezing and freeze-drying increased the proportion of starch resistant to α-amylase (EC 3.2.1.1) without previous treatment with dimethyl sulphoxide. There were only minor effects of cooking on the digestibilities of non-starch polysaccharides and their constituent sugars. With the higher dietary pea concentration there were marked increases in the flow of organic matter to, and fermentation in, the large bowel. These increases were associated with significant increases in colonic tissue and contents weights, and in colonic transit time. Both cooking and dietary pea inclusion rate altered the pattern of volatile fatty acids in caecal contents and in portal blood.

To study in vivo the contribution of the bacterial flora to amylomaize starch degradation in the rat, germ-free and conventional rats were fed on a diet containing either a normal maize starch or an amylomaize starch. In germ-free rats maize starch was almost totally digested in the small intestine, whereas 40% of the ingested amylomaize starch reached the caecum and 30% was excreted, despite the very high endogenous amylase activity. Study by transmission electron microscopy of germ-free caecal contents showed an endocorrosion of the starch granule. In conventional rats, as in germ-free rats, digestibility of maize starch reached 98% in the small intestine, whereas that of amylomaize starch was only 60%. In the caecum of these rats amylomaize starch was fermented, and this led to a decrease in caecal pH and to formation of short-chain fatty acids (SCFA), especially propionate. Comparison between conventional rats fed on maize starch or amylomaize starch showed that caecal SCFA concentrations during a circadian cycle varied in the same way whereas total SCFA and lactic acid concentrations were much higher in rats fed on amylomaize starch. Amylase (EC 3.2.1.1) activity was similar in the caecal contents of conventional rats whatever the ingested starch. It was lower in conventional than in germ-free rats, but no starch granule remained in the caecum of conventional rats. These results showed that bacterial amylase was more efficient at degrading resistant amylomaize starch than endogenous amylase.

Female weanling rats in three equal groups (n 12) were given orally by intubation 1 ml micellar solution of taurocholic aicd (10 mM) and either arachidonic acid (20:4 n−6), linoleic acid (18:2 n−6) or eicosapentaenoic acid (20:5 n−3) at a concentration of 120 mM. After 1 h the rats were given intragastrically 2 ml absolute ethanol and were killed 1 h later. Rats given oral 20:4 n−6 showed a significant reduction (P < 0.05) in the extent (%) of gastric mucosal haemorrhage compared with either the rats given 20:5 n−3 or 18:2 n−6 (8.3 (SD 7.3), 23.2 (SD 10.4) and 21.4 (SD 10.4)) respectively. In a second experiment, four equal groups (n 12) of female Wistar rats were fed for 5 weeks on either a control diet of standard laboratory rat food, or the same diet enriched with either maize oil or fish oil or butterfat at a level of 100 g/kg. Following a 24 h fast the rats received an intragastric dose of 2 ml ethanol and were killed 1 h later. Examination of the extent (%) of gastric lesion showed a significant reduction (P < 0.05) with the feeding of either maize oil or fish oil compared with the controls (12.2 (SD 8.2), 15.3 (SD 13.2) and 29.3 (SD 14.0) respectively). The butterfat diet was not significantly different from the control diet (23.8 (SD 8.1)).