1. Bioavailability of Fe from beef, spinach (Spinacea oleracea L.) and their mixtures was studied using anaemic and non-anaemic rats by haemoglobin regeneration efficiency (HRE) and apparent Fe absorption in two trials.

2. The initial haemoglobin levels of severely anaemic, mildly anaemic and non-anaemic rats were 63, 88 and 113 g/l, respectively. The Fe level in diets was about 30 mg/kg. All other nutrients equalled or exceeded the requirement of the growing rat.

3. The spinach Fe was well utilized by the rats with average HRE of 0.41, 0.53 and 0.36, and apparent Fe absorptions averaging 0.48, 0.59 and 0.37 for the severely anaemic, mildly anaemic and non-anaemic animals respectively.

4. Beef Fe was efficiently used by rats as reported by others. Average HRE were 0.42, 0.51 and 0.44, and average apparent Fe absorptions were 0.44, 0.47 and 0.46 for the severely anaemic, mildly anaemic and non-anaemic rats respectively.

5. When the percentage of meat Fe was increased from 0 to 25, 50, 75 or 100 of the dietary Fe, HRE and apparent Fe absorption were not increased significantly. A meat enhancement effect on total Fe absorption, reported by others for non-haem-Fe, did not occur in the present experiment.

6. Negative correlation coefficients between initial haemoglobin and HRE (r -0.79), and initial haemoglobin and apparent Fe absorption (r -0.73) were seen with the rats fed on dietary Fe from FeSO47H2O. This was not seen with the rats fed on dietary Fe from beef or spinach.

7. The Fe absorption pattern for the different Fe sources is evidence for a third Fe pool, a pool made up of highly soluble inorganic Fe salt, in addition to haem-Fe and non-haem-Fe complex pools. FeSO4 7H2O is not in the same gastrointestinal pool as non-haem-Fe complex such as spinach Fe. A suggested mechanism of absorption is discussed.

1. A number of dietary sugars are known to mediate the effects of copper deficiency. The effects of lactose (compared with sucrose) and a dietary Cu deficiency on hepatic and cardiac antioxidant enzyme activities and tissue mineral element status were investigated in the rat.

2. Groups (n 6) of male weanling Wistar rats were provided ad lib. with deionized water and diets containing sucrose (580 g/kg) or sucrose and lactose (387 g/kg and 193 g/kg respectively) with either control (12.0 mg/kg) or deficient (1.5 mg/kg) quantities of Cu for 77 d.

3. Animals consuming the low-Cu diets exhibited significantly decreased tissue Cu levels (P < 0.01), hepatic and cardiac cytochrome c oxidase (EC 1.9.3.1, CCO) activities (P < 0.01 and P < 0.001 respectively) and hepatic Cu-zinc superoxide dismutase (EC 1.15.1.1, CuZnSOD) activity (P < 0.05). The low-Cu diets also significantly decreased cardiac manganese superoxide dismutase (EC 1.15.1.1, MnSOD), catalase (EC 1.11.1.6) and glutathione peroxidase (EC 1.11.1.9, GSH-Px) activities (P < 0.01, P < 0.05 and P < 0.001 respectively).

4. Hepatic Mn was significantly increased in both lactose-fed (P < 0.001) and Cu-deficient (P < 0.01) animals. These increases were unrelated to hepatic MnSOD activity. Cardiac Zn was significantly (P < 0.01) increased in Cu-deficient animals.

5. Lactose feeding resulted in significantly increased cardiac CCO activity (P < 0.001) but significantly decreased hepatic CuZnSOD (P < 0.05), catalase (P < 0.01) and GSH-Px (P < 0.001) activities.

6. The activities of lactose dehydrogenase (EC 1.1.1.27, LDH) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6PDH) were found to be significantly (P < 0.05 and P < 0.01 respectively) increased in Cu-deficient animals and G6PDH activity was significantly (P < 0.01) decreased as a result of lactose consumption.

7. The observed changes in antioxidant enzyme activities associated with both Cu deficieny and lactose consumption may have important implications for the development of free radical mediated cell damage. However, no significant differences in either hepatic or cardiac levels of thiobarbituric acid reactive substances, a measure of lipid peroxidation, were found.

1. The relative importance of excretory routes in the removal of recently stored 67Cu following tetrathiomolybdate (TTM) administration was studied. Lambs fed on either 5 mg Cu/kg dry matter (DM) or 35 mg Cu/kg DM, were primed intravenously (iv) with 67Cu and challenged 27 h later with 99Mo-labelled TTM given either iv or intraduodenally (id). The profiles of 67Cu and 99Mo and of Cu and Mo in blood, bile, urine and faeces were measured.

2. Level of dietary Cu and route of administration of 99Mo-TTM affected the amplitude of blood, bile and urine profiles of 67Cu and stable Cu, but not the pattern of the responses observed.

3. The present study describes for the first time increased excretion of endogenous 67Cu through gastrointestinal secretions other than bile due to TTM administration.

4. Administration of TTM resulted in the immediate release of 67Cu from storage compartments in the body into the blood circulation. Changes in stable Cu levels in blood, bile, urine and faeces, and gut and systemic effects were evident. Biliary and urinary Cu excretion due to TTM was rapid and maximal within 24 h of injection.

5. Administration of 67Cu iv resulted in the immediate excretion of 67Cu in bile in a pulsatile, constant pattern. A similar pattern of 67Cu excretion into bile in synchrony with that of 99Mo was observed after 99Mo-labelled TTM administration.

6. The similar pattern of biliary 67Cu excretion observed after injection of 67Cu and after injection of 99Mo-labelled TTM 27 h later is discussed in relation to the times required to process the Cu through different hepatic pathways for excretion in bile.

1. The effectiveness of tetrathiomolybdate (TTM) in the removal of 67Cu from the long-term storage compartment in liver was studied. Lambs receiving 5 mg Cu/kg dry matter (DM) or 35 mg Cu/kg DM were primed intravenously (iv) with 67Cu and challenged 10 d later with 99Mo-labelled TTM given either iv or intraduodenally (id). The profiles of 67Cu and 99Mo and of Cu and Mo with time were measured in blood, bile, urine and faeces.

2. The level of dietary Cu affected the amplitude of profiles of 67Cu and Cu in blood, bile and urine after administration of 99Mo-labelled TTM. TTM administration increased liver Cu removal and this was most marked in sheep given TTM iv. The liver Cu removal from the long-term storage Cu compartment was low and was not affected by the route of administration of TTM. Endogenous Cu excretion was higher in lambs given TTM id.

3. Excretion of 67Cu in bile through the transhepatocellular pathway after TTM administration appeared absent, while the transbiliary and hepatolysosomal pathways were operative. The potential reasons for this change are discussed.

4. TTM predominantly enhances the removal of Cu from the short-term storage compartment, but effects on the long-term storage compartment may still be of significance.

1. A group of six cattle, three of which had a non-bloating history (group A) and had been ruminally cannulated for the previous 2 years, and three with a history of being bloat-prone (group B) and which had been ruminally cannulated only 3 months before the study, were fed ad lib. on chopped lucerne (Medicago sotiva) hay, lucerne pellets, or a 100 g chopped hay and 900 g rolled barley grain/kg diet over three periods of 30 d each. Flow of rumen digesta, by reference to CoEDTA and chromium-mordanted fibres, and foam production from samples of rumen contents were measured.

2. Samples of rumen contents (50 ml) from group A produced foam heights of 150 and 60 mm, 2 and 4 h after feeding respectively, compared with 240 and 150 mm for group B (P < 0.05).

3. The fractional passage rate of the 1-2 mm particles mordanted with Cr did not differ (P > 0.05) between groups.

4. The fractional outflow rates (FOR) for CoEDTA 0-2 h and 2-7 h after feed was offered were 0.205 and 0.160/h for group A and 0.093 and 0.086/h for group B respectively (P < 0.05).

5. Rumen-fluid FOR 0-2 h and 2-7 h after provision of feed were significantly (P < 0.05) inversely correlated (r -0.74 and -0.85 respectively) with the amount of foam produced from rumen contents at these times.

1. In hay-fed, cannulated sheep the apparent degradation in and outflow from the rumen were determined for graded doses of mixtures of the amino acids lysine, threonine and methionine, administered intraruminally and using polyethylene glycol (PEG) as a liquid marker. The doses ranged between 2.5 and 15 g for each amino acid in the mixtures.

2. Relative rate of apparent degradation in the first 4 h was highest for lysine, and lowest for methionine. The apparent degradation in 24 h was highest for lysine and lowest for threonine. Conversely the fraction flowing out of the rumen in intact form in 24 h was highest for threonine and lowest for lysine. Rates of apparent degradation as well as outflow were dose-dependent.

3. The validity of the estimated outflow of amino acids from the rumen was corroborated by measurements of concentrations of the amino acids in duodenal contents and in blood plasma which were also dose-dependent.

4. It was concluded that part of the requirement for the essential amino acids threonine and methionine may be met, even when these amino acids are delivered in unprotected form, given as a feed supplement.

1. Five rumen-fistulated cows were given freshly cut ryegrass (Lolium perenne L.) and lucerne (Medicago sativa L.), on separate occasions, to compare rates of particle breakdown and aspects of rumen fermentation.

2. Cattle were required to consume their daily allowance (offered ad lib.) in two 2 h feeding periods daily.

3. During the first 2 h feeding period, dry matter (DM) intakes of ryegrass (4.75 kg) and lucerne (4.85 kg) were similar. Eating reduced 46% of ryegrass and 61 % of lucerne to a size able to pass a 2 mm sieve (P < 0.001). Rumen DM particles retained on the 2 and 4 mm sieves had a low probability of passage out of the rumen, and accounted for only 6 % of faecal DM with both feeds.

4. Ryegrass was cleared from the rumen more slowly than lucerne. During eating, rumen DM particles which could not pass the 2 mm sieve increased from 323 to 511 g/kg for ryegrass and from 201 to 389 g/kg for lucerne. The rate of particle size reduction for lucerne stem was similar to that for ryegrass.

5. When lucerne was eaten the increases in rumen volatile fatty acid (VFA) and ammonia concentrations were much greater than for ryegrass (P < 0.001). The proportions of plant chlorophyll released during eating were similar for both feeds (0.570 and 0.607), but 2 h after eating 22.3 g had been released from lucerne (79.1 %) compared with 15.0 g from ryegrass (63.8%). The flux of water from the rumen to the omasum was similar for ryegrass (10.2 litres/h) and lucerne (12.7 litres/h) during eating, but declined to 6.0 litres/h after eating with the lucerne diet.