Levels of selenium in whole blood, plasma, erythrocytes and platelets, glutathione peroxidase (EC 1.11.1.9; GSH-Px) activity in erythrocytes and platelets and vitamin E, low-density-lipoprotein (LDL)-cholesterol and vitamin E: LDL cholesterol in plasma were measured in seventy-five healthy subjects aged < 65 years and twenty-eight healthy and twenty-three institutionalized elderly people aged > 65 years. Healthy elderly subjects had significantly lower levels of Se in whole blood and plasma when compared with younger subjects. Other measurements of Se status were not significantly different. In the healthy subjects plasma levels of vitamin E and LDL-cholesterol increased with age to 60 years and decreased above 80 years. Vitamin E: LDL cholesterol values were not affected by age. Measurements of Se and vitamin E status in the institutionalized elderly compared with the healthy elderly were all reduced with the exception of platelet Se levels and erythrocyte GSH-Px activity. Ageing per se had minimal effect on Se and vitamin E status but intercurrent illness and decreased food intake can lead to reduced levels in the elderly.

The composition and dental properties of eight different soft drinks, representing some of the most popular types used in the UK, were examined. Demineralization experiments were conducted on hydroxylapatite, the basic component of dental enamel, determining calcium dissolving by atomic absorption spectroscopy and phosphorus by u.v. visual spectrophotometry. The titratable acid content of the drinks was found to give a better guide than their pH to their potential dental erosiveness. The sugar content, in their ready-to-drink form, varied from zero in a low-calorie product up to almost 14 % in a blackcurrant drink, but using a technique with a relatively long contact time, and in the absence of intact dental plaque, the demineralizing action on hydroxylapatite of the acids already in the drinks eclipsed the effects of the acid generated by oral micro-organisms from the sugars in the drinks. The pure citrus juices showed potentially the worst dental properties, followed by the orange and blackcurrant concentrates after dilution to their ready-to-drink form, with least demineralization from the carbonated drinks, and a cola drink giving especially low values.

The effect of giving Maillard reaction products (MRP) on zinc metabolism was investigated in the rat. In Expt 1, MRP were prepared by incubating casein with either glucose or lactose under controlled reaction conditions, and were quantified as either ‘early’ or ‘advanced’ after estimation of lysine loss and lysine destruction respectively. In Expt 2, the effect of the purified early MRP fructose–lysine (FL) on Zn metabolism was studied. The experimental diets containing 20 mg Zn/kg were given to weanling rats for 21 d. Zn balance was assessed over 9–14 d (Expt 1), or 1–14 d (Expt 2). Femur, liver, kidney and serum Zn concentrations were determined at 21 d. The major effect of the MRP in the casein-sugar mixtures was on urinary Zn excretion. The casein-glucose MRP induced up to a 6-fold increase in the quantity of Zn excreted in the urine. The magnitude of the hyperzincuria increased with the extent of the Maillard reaction. Similar dietary levels of casein-lactose MRP increased urinary Zn loss 2-fold. Free FL had no effect on urinary Zn. Faecal Zn, Zn retention, liver, femur and serum Zn were generally not influenced by giving MRP from casein-sugar mixtures or by giving free FL, although kidney Zn was decreased in rats fed on FL. It was concluded that although urinary Zn excretion can be increased by the presence of MRP in the diet, this is only a minor excretory pathway and would have little influence on overall Zn nutrition in individuals fed on a diet adequate in Zn.

Sixteen pigs were given a purified diet of maize flour and casein from 5 to 25 d of age with or without a biotin supplement (100 μg/kg). From 26 to 94 d of age, eight of the pigs were changed to a wheat and casein diet with or without the biotin supplement and eight continued on the maize flour and casein diet. The weight gain and feed conversion ratio of the pigs were not affected by the dietary biotin supplement or the carbohydrate source. The pigs given the unsupplemented maize flour diet developed foot lesions, scaly skins and showed a reduction in carcass length. The excretion of biotin in the faeces was similar for the pigs given the biotin-supplemented and unsupplemented diets. The excretion of biotin in the faeces of pigs given the wheat diet was ten times as great as that of the pigs given the maize flour diet. The excretion of biotin in urine was 6 μg/d in the pigs given the unsupplemented maize flour diet and 67 μg/d in the pigs given the biotin-supplemented diet between 91 and 94 d of age. The biotin contents of the liver, heart, kidney, adrenals and plasma were increased by biotin supplementation of the maize flour diet. The 16:1/16:0 and 18:1/18:0 fatty acids ratios in the liver were decreased by biotin supplementation of the maize flour diet.

Labelled particles were prepared by mordanting low concentrations (0.1 or 5 g/kg dry matter) of chromium to neutral-detergent-extracted stems (1–2 mm or 10 mm in length) of bromegrass (Bromus inermis). These were used in the study of reticulo-rumen particle kinetics of four steers given bromegrass hay and from the results a quantitative model of particle digestion and passage was developed. At the 0.1 g Cr/kg concentration there was minimal interference with digestibility of the feedstuff. The ratio, dry weight of the reticulo-rumen large-particle pool (> 3.35 mm):small-particle pool (< 3.35 mm) was 2:1. It was derived from the model that volatile fatty acids (VFA) and carbon dioxide in the rumen were produced mainly from large particles, and that between 500 and 700 g/kg hay dry matter was digested in the reticulo-rumen. It was also derived from the model that a major portion, 200 (SE 110) g/kg, of the hay dry matter was rapidly solubilized and that the material leaving the reticulo-rumen was composed of small particles (500–840 g/kg), large particles (100–160 g/kg) and an unknown portion of soluble dry matter of hay (0-400 g/kg). Disappearance from the large-particle pool in the model involving the lowest Cr level was directed to formation of VFA and CO2 (0.68 (SE 0.04) of total flow) to the small-particle pool (0.25 (SE 0.06) of total flow) and direct passage from the reticulo-rumen (0.07 (SE 0.002) of total flow). The disappearance from the small-particle pool was to VFA and CO2 production and to the omasum accounting for 0.14 (SE 0.18) and 0.86 (SE 0.24) respectively, of the total flow. It was concluded that the low-level-mordanting technique in combination with appropriate sampling yielded a realistic quantitative description of forage breakdown and movement processes in the digestive tract of cattle.

Twenty pigs weaned at 5 d were given pelleted diets based on maize flour and casein and supplemented with 0,50,100,150 or 200 μg biotin/kg diet. The performance of the pigs was not influenced by the biotin content of the diets. Typical biotin deficiency symptoms (foot lesions and skin pustules) were observed in pigs given the unsupplemented diet and the diet supplemented with 50 μg biotin/kg diet. Tissue biotin concentration plateaued when 100 μg biotin/kg was added to the diet. Faecal biotin excretion was independent of dietary biotin intake, but increased with age. Urine biotin excretion at 102 d was significantly lower for the unsupplemented pigs than for the pigs given various levels of dietary biotin supplements. A dietary requirement of biotin for young pigs between 50 and 100 μg/kg diet is suggested from the results of the present experiment.

Plastic particles of defined length (2, 5 mm) and specific gravity (sp.gr. 1.10, 1.34, 1.77) were administered just before feeding into the reticulo-rumen of four cattle and four swamp buffaloes given a diet predominantly of rice straw ad lib. Simultaneously, doses of ground rice straw marked with Cr and Yb were likewise given. Plastic particles were recovered from faeces for 12 d after dosing, and divided into non-ruminated (NR) and ruminated (R) particles. Excretion data of plastic particles were interpreted using a four-pool model incorporating passage of NR (kp) and R from the reticulo-rumen, post-ruminal passage, rate of chewing (kr) and two lag times. An inverse relationship was found between kr and sp.gr. The kr was higher for 5 mm than that for 2 mm particles. In contrast, kp was greatest for particles of sp.gr. 1.34, with higher kp for 2 mm than for 5 mm particles. Rates of passage and rumination (kp, kr) were higher for buffaloes than for cattle. Rumination time was related to kr, most highly (r2 0.96) with kr of 2 mm, 1.10 sp.gr. particles. Fragmentation of 5 mm particles by rumination tended to increase the rate of passage from the rumen. Ruminal passage rates of Yb and Cr markers were poorly correlated with each other and with kp of any of the plastic markers. Reanalysis of published data from plastic particle studies supported the relationships between sp.gr., size, kp and kr. In view of the additional information (kr) obtained using plastic particles, we suggest their use may be appropriate in studies which investigate specific differences in digestive function, while being less suitable for investigating differences between diets.

Eight pigs were given a semi-purified diet based on maize flour and casein containing 10 μg biotin/kg. The diet was given ad lib. with or without a supplement of 70 μg biotin/kg diet from 5 to 94 d of age. The flow of biotin in the stomach was similar to the biotin intake (13.5 and 112 μg/d) for the unsupplemented and biotin-supplemented pigs respectively. The flow of biotin through the small intestine decreased for the biotin-supplemented pigs from 39 μg/d in the first quarter of the small intestine to 7.9 μg/d in the last quarter. The flows of biotin in the caecum, large intestine and colon were similar for both the unsupplemented and biotin-supplemented pigs, with values of 17–54 μg/d, indicating the synthesis of biotin in the hind-gut.

Four types of hay were used: an early-cut and a late-cut lucerne (Medicago sativa) and an early-cut and a late-cut ryegrass (Lolium italicum). Digestibility and voluntary intake were measured on six adult sheep maintained in metabolism crates and fed 10% above the previous day's consumption, in equal portions at 08.00 and 16.30 hours. Lucerne intake was higher than that of ryegrass at similar digestibilities. The rate of digestion of the four hays was measured using nylon bags and the rates of digestion of dry matter for late-cut lucerne were faster than those for the late-cut ryegrass. Eleven adult sheep fitted with oesophageal (four), rumen (four) or duodenal (three) fistulas were used for collecting digesta samples at the different sites. They were fed successively with the four hay types. Each was offered to appetite, once daily, in a meal taken over 4 h. The rumen of rumen-fistulated sheep was completely emptied by hand once before feeding (08.00 hours) and once after removal of refusals (12.00 hours). The number of times the ingested hay was chewed during the meal and the time spent masticating was greater for the late-cut hays and greater for the ryegrass compared with the lucerne hays. The particle size of the boluses was greater than that of the rumen contents, which in turn was greater than that of the duodenal contents and faeces. The percentage of particles > 8 mm in the boluses from the ryegrass was higher than that of lucerne, and that of the early-cut ryegrass was greater than that of the late-cut ryegrass. This was also the case for the percentage of particles > 1.6 mm in the rumen contents after the meal. The rate at which dry matter disappeared from the rumen was greatest during the meal except with late-cut ryegrass; it was particularly high with late-cut lucerne, a little less with early-cut ryegrass and much lower with the other two hays. When nylon bags containing food boluses were placed in the rumen, it was apparent that without rumination, with the exception of the very digestible early-cut ryegrass, microbial degradation alone did not reduce the particle size.

Bedouin goats were fed on wheat straw as a single-component diet under two watering regimens, drinking once daily or once every 4 d, in order to clarify whether lignin-degradation products were absorbed, metabolized and excreted in urine. Acid-soluble lignin accounted for 220 g/kg total lignin, its digestibility was the highest (0.87) and was unaffected by water deprivation. Acid-insoluble lignin accounted for 780 g/kg total lignin and its digestibility increased during water deprivation from 0.21 to 0.41. Alkali-soluble lignin accounted for 320 g/kg total lignin and its digestibility increased during water deprivation from 0.44 to 0.53. Digestibility of structural carbohydrate was considerably higher than that observed in other domesticated ruminants fed on wheat straw. It responded positively to water deprivation, increasing from 0.63 to 0.73 with cellulose and from 0.61 to 0.68 with hemicellulose. The amount of urinary aromatic acids, mainly in the form of hippuric acid, considerably exceeded the potential contribution of any non-lignin component which might affect the excretion of aromatic acids. A considerable percentage (71−76) of the apparently digested lignin was not accounted for as soluble phenolic compounds in faeces or as aromatic acids in urine, and hence was apparently completely metabolized. Lignin is a key substrate which is extensively digested in goats fed on low-quality forage, with subsequent absorption of end-products. This enhanced the availability of structural carbohydrates for fermentation and was associated with excretion of high-energy metabolites in the form of benzoic and hippuric acids.

Six pigs (initial weight 30 kg) were fitted with T-shaped cannulas in the ileum, 0.3 m from the ileocaecal junction. Each pig was given each of seven diets for a 10 d period. The diets contained wheat (var. Banks and Egret), barley, sorghum, meat meal, soya-bean meal or casein as test feedstuffs. The apparent digestibilities of biotin to the ileum of the pigs were 0.06, -0.03, -1.23, 0.18, 0.82, 0.12 and 0.95 for the diets containing wheat (var. Banks), wheat (var. Egret), sorghum, barley, meat meal, soya-bean meal and casein respectively. The same diets were given to 168 chickens. Digesta were collected from the terminal ileum after 7 d. The apparent digestibilities of biotin to the ileum of the chickens were 0.11, −0.10, −0.73, 0.05, 0.69, 0.28 and 0.75 for the diets containing wheat (var. Banks), wheat (var. Egret), sorghum, barley, meat meal, soya-bean meal and casein respectively.

Six pigs were given a biotin-deficient diet (10 μg biotin/kg) for 14 weeks. The pigs were given the same diet for a further 42 d with one of three biotin treatments: no supplement, 400 μg biotin/d given orally, 400 μg biotin/d infused into the caecum. The concentrations of biotin in the liver, kidney and heart, at the conclusion of 42 d were greater in the pigs given the oral biotin supplement than in the unsupplemented pigs. The values for the pigs given the caecal infusion of biotin were intermediate. The excretion of biotin in faeces was increased from 35 to 101 μg/d by the caecal biotin infusion, and the urinary excretion was increased from 35 to 83 μg/d. The oral dose of biotin increased urinary biotin excretion from 35 to 345 μg/d, but there was no change in faecal biotin excretion. Two pigs were fitted with ileal cannulas and catheters in the vena cava. The pigs were given a dose of [14C] biotin either into the caecum, when the ileum was occluded by a bladder catheter, or orally. [14C] biotin was measured in the urine and plasma and showed that post-ileal biotin absorption was 8 % as efficient as the absorption of biotin after oral dosing.