1. Pangola grass (Digitaria decumbens) was grown with or without sulphur fertilizer, cut at seven stages of growth, dried and given to sheep with or without a supplement of 0.6 g S as sodium sulphate/d. Voluntary intake and digestibility of dry matter (dm) and retention time in the reticulo-rumen, of various components of the grasses were determined.

2. Grass grown on the S-fertilized plots had a mean S content of 1.57 g/kg dm compared with 1.03 g/kg dm for the control but there was no difference in the level of other elements. S fertilizer increased the level of acid-detergent fibre and lignin.

3. In the absence of a S supplement, fertilizer S increased voluntary intake by 10.5%, dm digestibility by 0.008 and reduced the period food dm was retained in the reticulo-rumen by 18.5%. Fertilizer S had no effect on rumen pH or volatile fatty acid concentration in rumen fluid, but decreased the molar proportions of propionic and butyric acids and increased those of acetic, isobutyric, isovaleric and caproic acids.

4. Supplementary S had little effect on the voluntary intake and dm digestibility of the S-fertilized grass but increased the voluntary intake and dm digestibility of the control grass by 22% and 0.036 respectively (P < 0.01). Thus the voluntary intake and dm digestibility of S-fertilized grass was lower than that of the control grass when the determinations were made with sheep supplemented with S.

5. It was concluded that S fertilizer increased nutritive value by overcoming a simple S deficiency in the diet when diets contained less than 1.7 to 1.8 g S/kg dm but this benefit was offset by a decrease in the content of digestible neutral-detergent solubles and an increase in the lignin content of the food.

1. Total body water (TBW) was measured using tritiated water in sixty-five children. The measurements were distributed throughout rehabilitation in order to define the effect of changing energy intakes.

2. Oedematous children had a high TBW which decreased to the normal range during loss of oedema providing they were not receiving more than maintenance amounts of energy during this period.

3. Marasmic children who had not received greater than maintenance amounts of energy had a normal TBW.

4. Treatment with a high-energy diet was associated with an initial increase in TBW.

5. The possible mechanisms for this phenomenon are discussed.

1. A computer programme is described which simulates energy metabolism in the whole animal. Simulation was based on representation of the animal as a quasi-steady-state system.

2. Input for the programme consisted of the chemical composition of the diet and an estimate of either the maintenance energy requirement or an estimate of energy retention.

3. Simulation was performed by estimating the yield of adenosine triphosphate in the major metabolic pathways operative in simple-stomached animals, and on the utilization of adenosine triphosphate in major anabolic processes.

x4. Results obtained from simulation were in close agreement with experimental observations reported by McCracken (1975).

1. Statistical analyses were carried out on results obtained under strictly-controlled conditions in metabolism stalls with forty-one different rations fed to 127 adult non-pregnant dry cows, and with fourteen other different rations fed to thirty-five adult non-pregnant lactating cows that had calved 2–6 months earlier and whose daily milk production ranged from 11 to 20 kg.

2. Correlations between calcium digestibility and values for the sum of the alkaline ions sodium and potassium minus the sum of the stable acid ions chloride, sulphate and phosphate were calculated for all fifty-five experimental diets.

3. The results showed that the excess of the anions over the cations, in rations maintaining a positive Ca balance but not in rations allowing a negative Ca balance, increases the absorption of Ca from the intestine. Phosphorus, not alone but with chloride and sulphate, is the most important component of this effect.

1. A study was made of protein utilization in rats given a variety of low-protein diets containing (g/kg) egg albumin 18, casein 49, gluten 50, or mixtures of either maize protein and gelatine 58, or casein and gelatin 37, each with supplemental methionine. The diets were limiting in leucine, tryptophan or lysine, or in both tryptophan and the sulphur-containing amino acids.

2. Values obtained for net protein utilization (npu) at these low levels of nitrogen intake were markedly higher than the amino acid score calculated for the different test proteins, except with casein for which the two values were similar. The npu values agreed more closely with chemical score values based on the content of S-amino acids or isoleucine in the dietary protein.

1. Responses of the protozoa population to the composition and the components of the diet were studied in permeable continuous cultures of rumen contents.

2. In Expt I a study was made of responses to diets containing different combinations of rice straw, lucerne meal and mixed concentrates given to the cow supplying inocula for cultures. It was found that (1) when a diet devoid of concentrates was fed, entodiniomorphs decreased in numbers; (2) their numbers increased with the increase in the amount of concentrates; (3) holotrich numbers were hardly affected by the type of diet; (4) rice straw and lucerne meal were not essential for protozoa to survive in culture medium.

3. In Expt 2 responses were determined to diets containing different combinations of maize, maize starch, sugars (glucose-sucrose (1:1, w/w)), soya-bean meal and isolated soya-bean protein. The results suggested the following relationship between dietary component and protozoa population. (1) The diet rich in both starch and sugars sustains the increased numbers of protozoa on the whole. (2) The diet rich in starch and deficient in sugars decreases selectively Dasytricha and small species of Entodinium such as Entodinium minimum and E. nanellum. The other species of protozoa, especially large entodiniomorphs such as Ophryo-scolex and Polyplastron, are maintained at relatively high levels. (3) The diet deficient in starch and abundant in sugars decreases general entodiniomorphs except small species, while the numbers of Holotrichs are kept at relatively high levels.

1. Rats were given diets containing different fats (200 g/kg) from weaning to 8 months of age. The fats were sunflower-seed oil (SFO), lard (L) and an equal mixture of sunflower-seed oil and lard (mixed-fat diet; MF). A control group was given the basal diet unsupplemented with fat. Energy intake and body-weight of individual animals were recorded weekly.

2. Three animals from each dietary group were killed after 5, 13, 17 and 29 weeks on the experimental diets. At slaughter epididymal fat pads were excised, weighed and the number and size of fat cells in the pad was determined.

3. There were no significant differences between the energy intake in the whole experimental feeding period for rats given the different fat diets. However, when energy intakes were examined on a monthly basis animals given MF had a significantly higher energy intake in the first 2 months of feeding than those animals given SFO. In the third month of feeding (when animals were over 12 weeks old) the group given L had a significantly higher intake than the group given SFO.

4. Body-weight, epididymal-fat-pad weight, cell size and cell number did not differ significantly between the ‘fat-fed’ animals at any individual slaughter period. Analysis of pooled values from the four slaughter periods revealed that animals given MF had significantly more fat cells than those given SFO.

5. We conclude that the nature of the dietary fat has no effect on the cellularity of developing adipose tissue but that the number of fat cells formed is sensitive to energy intake before 12 weeks of age in the rat.

1. Pigs, each surgically prepared with a Thiry-Vella jejunal loop were used to study the absorption of calcium and inorganic phosphate from the intestine.

2. The loops were perfused daily for 6–8 h with a nutrient solution and absorption from the perfusate was measured.

3. The technique employed minimized atrophy of the jejunal mucosa and enabled the measurement of hourly or daily changes in absorption rate of components of the luminal fluid.

4. No differences were observed when polyethylene glycol (PEG; molecular weight 4000), [14C]PEG or 51Cr-EDTA were used as markers of net water movement.

5. Increasing the concentration of Ca in the perfusate resulted in the demonstration of a two-component relationship between net absorption rate of Ca and intraluminal Ca concentration. An initial rapid absorption rate from 0 to 4 mm was found, then a slower rate from approximately 5 mm upwards which did not saturate at the highest concentration tested (25 mm).

6. Increasing the concentration of phosphate in the perfusion solution increased the net absorption of phosphate from that solution. Although a two-component system, similar to that for Ca, was not evident, net absorption of phosphate was not saturated at the highest concentration tested (50 mm).

7. The absorption of Ca was unaffected by the presence of phosphate in the solution but Ca (2.5 mm) enhanced the absorption of phosphate.

1. An investigation was made to determine the value of tissue enzymes as indices of protein nutrition.

2. Sheep were given a reduced protein intake for 6 weeks, whereupon some were given a protein supplement for 1 week and then the sheep were refed their initial diet. In the first experiment sheep were taken from pasture and given a reduced protein intake for 6 weeks whereupon some were given a protein supplement for 1 week and then all the sheep were grazed on pasture. In the second experiment sheep were fed on lucerne (Medicago sativa) chaff ad lib. in place of grazing before and after the period of reduced protein intake during which one group was also fed on molasses. Again, another group was given a protein supplement for 1 week after 6 weeks on the reduced protein intake.

3. As a result of reduced protein intake there were significant (P < 0.01) changes in the liver in the content of DNA, protein: DNA, arginine synthetase (combined activity of argininosuccinate synthetase (EC 6.3.4.5) and argininosuccinate lyase (EC 4.3.2.1)), aspartic aminotransferase (EC 2.6.1.1), glutamic dehydrogenase (EC 1.4.1.2), arginase (EC 6.5.3.1) and tyrosine aminotransferase (EC 2.6.1.5).

4. There were few consistent changes in muscle in the levels of DNA, protein:DNA, creatine kinase (EC 2.7.3.2) and aspartic aminotransferase.

5. The feeding of molasses to one group tended to reduce the change in DNA level but still resulted in significant changes in the enzymes.

6. It is suggested that the levels of arginine synthetase, aspartic aminotransferase and DNA in liver could be useful indices of protein status.

1. Heavy-breed (HB) chicks differed from light-breed (LB) ones in their propensity to be overfed. Whereas in the LB chicks the amount by which they could be overfed reached 70 % more than the food consumed daily by the ad lib.-fed chicks, in the HB chicks the maximal excess was only 13 %.

2. Overfeeding caused a slight but statistically significant increase in the linear growth rate (shank length) of the LB chicks, with an opposite effect in the HB chicks.

3. Overfeeding increased the weight of the crop, proventriculus, small intestine, pancreas, liver and adipose tissue but had no such effect on the heart, cerebrum or cerebellum.

4. Overfeeding had no effect on the specific activities of the pancreatic digestive enzymes, liver xanthine dehydrogenase, or tryptophan oxygenase (EC 1.13.1.12). The increase in the total activities was due entirely to organ hypertrophy.

5. Obesity induced in young chicks had no residual effects on the adult LB chicks, but reduced the linear growth of the adult HB chicks.

6. An explanation for the difference between breeds in response to overfeeding at an early age is discussed.

1. Six experiments, involving a total of 320 pigs, were conducted to examine the reponse of growing pigs to diets supplemented with free lysine when fed either once daily or in six equal portions at intervals of 3 h. The effect of dry or wet feeding on the response to free lysine was examined in Expt nos. 4 and 5. The assumption of linear lysine response over the range of lysine supplementation was examined in Expt no. 6.

2. A significant (P < 0.01) interaction between lysine supplementation and frequency of feeding occurred for growth rate and food conversion ratio. Growth responses to the supplements of free lysine with once daily feeding were only 67 % of that achieved with frequent feeding.

3. Wet feeding had no effect on the growth responses to free lysine supplements.

4. The lysine response was linear over the range of lysine supplementation examined.

5. The implications of these results to the interpretation of experiments examining the lysine requirements of pigs are discussed.

A method of estimating volatile fatty acid (VFA) production in the rumen in non-steady-state conditions was proposed. Laboratory models indicated that good estimates of total production over a complete feeding cycle could be obtained even when a wide range of production rates and volume changes occurred during the experiment. But estimates of instantaneous production rates might have contained large errors unless some attempt was made to match the infusion rate of labelled VFA to the rate at which VFA was produced in the rumen.

1. The influence of replacing 10 % of the urea nitrogen in a purified diet with casein, maize gluten or white fish meal on the efficiency of conversion of dietary-N into microbial N was examined using sheep equipped with rumen fistulas and duodenal re-entrant cannulas.

2. Total nitrogen (TN), non-ammonia nitrogen (NAN) and amino acid nitrogen (AAN) flowing to the proximal duodenum were significantly higher (P < 0.05) when maize gluten was added to the diet, and this appeared to be due to an increased efficiency of microbial protein production.

3. Pepsin secretion was not significantly different between treatments and the daily amount of pepsin N flowing to the proximal duodenum was very small (40–53 mg). The peak of pepsin activity in duodenal digesta was reached 6–8 h after feeding.

4. The possible practical implications of the results are discussed.

1. The net protein utilization (npu, the percentage of dietary nitrogen retained in the body, allowance being made for endogenous urinary and faecal N) of diets composed of Nigerian foodstuffs, based on rice, sorghum (Sorghum sativa) or cassava (Manihot utilissima), was compared to that of a minimal protein diet used to determine endogenous N excretion, supplemented with whole egg. The addition of dl-methionine and l-tryptophan to the rice diet produced a small but non-significant increase in npu, whereas the addition of dl-methionine to the cassava diet produced a very significant increase in npu. The npu of a diet based on home-pounded, winnowed, sorghum flour was higher than that of a diet based on milled whole-meal sorghum due to the low digestibility of the latter diet.

2. The digestibility of the rice and cassava diets were the same, although the total crude fibre content of the rice diets was lower than that of the cassava diets.

3. Nigerian men used the proteins of the egg diet and of mixed diets based on rice, sorghum and cassava more efficiently than predicted by applying methods recommended by the FAO/WHO ad hoc Expert Committee on Energy and Protein Requirements (FAO/WHO, 1973).

4. The recommendations of that Committee (FAO/WHO, 1973) to reduce the amounts of sulphur amino acids and tryptophan, contained in the ‘provisional pattern of amino acids’ proposed by the FAO Committee on Protein Requirements (FAO, 1957), are supported, but the increases in lysine and threonine are not supported, by the present results.

1. Four pregnant sows were used to study lysine requirements by means of the interpretation of values for plasma amino acid and blood urea. Diets containing graded levels of dietary lysine were fed at the rate of 1.82 kg/d.

2. Plasma lysine remained at a low level up to 6.4 g dietary lysine/kg (dry matter basis) and then increased sharply with further increases in lysine intake.

3. Blood urea levels decreased when the dietary lysine content was increased to 6.4 g/kg and then increased at higher dietary lysine concentrations.

4. Both criteria of response indicated that the lysine requirement of the pregnant sow given 1.82 kg diet/d during the later stages of pregnancy does not exceed 10.00 g/d.

1. Adult male Japanese quail (Coturnix Coturnix Japonica) were overfed at different intensities during varying periods: (1) by gradually increasing the daily amount of food up to twice the control level in a period of 11 d and keeping this level constant during the subsequent 12 d period (prolonged overfeeding); (2) by gradually increasing the daily amount of food up to approximately twice the control level in a period of 6 d (short, low-intensity overfeeding; SL); (3) by gradually increasing the daily amount of food up to approximately 2.5-fold the control level in a period of 7 d (short, high-intensity overfeeding; SH).

2. The activities of acetyl-CoA carboxylase (EC 6.4.1.2; CBX), fatty acid synthetase (FAS), ATP citrate lyase (EC 4.1.3.8; CCE) and malate dehydrogenase (decarboxylating) (NADP) (EC 1.1.1.40; ME) were determined in adipose tissue (AT) and liver of the overfed and ad lib.- fed chicks. Size and fat content of carcass, AT and liver were also determined in order to evaluate the extent of obesity.

3. The weight of carcass, lean body mass, liver and AT and the extent of fat deposition increased with the total amount of food consumed. Obesity was particularly pronounced in quail after prolonged overfeeding.

4. Lipogenic enzymes in liver were much more active than those of AT. The specific activities of CBX, FAS and CCE in liver and AT in overfed Japanese quail increased consistently in the SL and SH groups only and the increase was related to the level of food intake in these groups. ME was the only enzyme whose specific activity increased in all overfed groups. Total AT enzyme activities were increased most strongly after prolonged overfeeding because of the pronounced tissue enlargement in that treatment. But in liver, where tissue enlargement was less and differences in size due to the three overfeeding treatments were less marked, total activities depended mainly on the enhancement of specific activities.

5. The results lead to the conclusion that the increase in hepatic lipogenic enzymes roughly reflects the current food intake and may thus be considered to represent the primary adaptation in the overfed Japanese quail. Secondary adaptation, involving tissue enlargement, occurs principally in AT of Japanese quail after prolonged overfeeding, in which situation AT contributes significantly to total lipogenic activity.