Energy and nitrogen metabolism of diseased chickens: aflatoxicosis.

1. New Hampshire chicks were fed on diets containing 0 (control), 0-7 (A), or 1-1 (B) ppm of aflatoxin B1. In two trials 1-d-old chicks were offered ad libitum the three diets for 14 d. The gaseous exchange of five chickens from each group was measured for 3 or 4 d, the same diets being fed, at 2, 3, 4 and 5 weeks of age in two series of experiments. The controls were fed at the lower intake of the two other groups. Following each series of experiments at the various ages, birds were starved for 24 h and their heat production was re-measured over the next 24 h. 2. Mortality was highest and growth and food conversion poorest where the diet with the highest aflatoxin concentration was fed. Mortality was confined to the first 2 weeks. 3. Performance of birds in the chambers was improved in the second series due to differences in food intake. It also improved with age suggesting some resistance to the toxin. 4. Mean respiratory quotient was 0-97 for fed chickens on diet B. This was significantly different from 0-92 for the two other groups. Similarly, during starvation the RQ was 0-76 compared with 0-73. 5. birds fed on diet B generally grew better, retained more nitrogen and had a better energy balance in the respiration chambers than the other two groups. Metabolisability of dietary energy was less (68.5%) for all groups at 2 to 3 weeks than when older (70%) but availability of ME was the same (71%) for all groups. 6. Heat production (kJ/kg0-75) of starved birds on diet B was significantly lower than the other two groups, while endogenous nitrogen excretion was higher. 7. Water consumption (ml/g food and g/100 g body weight) was greatest for birds on diet B. 8. Although aflatoxin in the diet substantially reduced intake there was no indication that at these reduced levels of intake, nitrogen or energy metabolism were measurably impaired.     

Effect of intestinal microflora on digestible energy and fiber digestion in chickens fed a high-fiber diet.

The effect of intestinal microflora on digestible energy (DE) value and fiber digestion was studied in single-comb White Leghorn chickens fed a low-fiber diet (experiment 1) or a high-fiber diet with low or adequate metabolizable energy (ME) value (experiment 2). Fecal energy excretion was calculated from the difference between total energy excretion in urinary and fecal droppings and urinary energy excretion, which was estimated from the energy values for individual urinary nitrogenous compounds extracted with Li2CO3. When the birds were fed the low-fiber diet, no differences in growth, DE, or ME were observed between germ-free and conventional environments. Of birds fed the high-fiber diet, growth of those in the conventional environment was similar to that of the birds in the germ-free environment at the adequate ME value, whereas birds in the conventional environment grew faster than the birds in the germ-free environment at the low ME value. Changes in observed dietary ME values of the high-fiber diets, being higher in birds in the conventional environment than in birds in the germ-free environment (experiment 2), were almost entirely accounted for by those in dietary DE values, most of which was contributed by crude fiber digestion. It was concluded, therefore, that by means of fiber digestion, the intestinal microflora may benefit the host bird by supplying extra energy, which would result in growth promotion, particularly when the bird is deficient in energy.     

Influence of substitution method and of food intake on bioassays to determine metabolisable energy with chickens

1. Several different methods of assaying the metabolisable energy (ME) of ground maize and a maize and glucose mixture were studied. Over a 24‐h period fasted cockerels lost more energy and nitrogen in their excreta than those fed 15 g maize and 15 g glucose monohydrate.

2. Discrepancies in ME values of maize were found between 1) Hill's method (substitution for glucose) and 2) Sibbald's method (the difference between energy ingested and excreted, corrected for endogenous losses by a comparison with fasted controls). These discrepancies were attributed to differences in endogenous energy losses between fed and fasted birds and interactions between the test substance and reference diet.

3. No significant differences could be detected when substitution for glucose was compared to substitution for the entire diet in three experiments.

4. Significant differences in the ME of maize because of the composition of the basal diet were found (semi‐purified: practical; 17·20:14·56 kJ/g; and 50 g/kg added fat: 100 g/kg added fat; 15·94:16·69 kJ/g).

5. Food intakes equal to 70, 60 or 30% of ad libitum did not affect the ME of maize when the substitution for glucose method was used.

6. It is concluded that basal diets for ME determinations should be carefully selected because of possible interactions between dietary components. When ME is determined by feeding small amounts of the test material, endogenous losses may be over‐estimated because the control birds are in a different physiological state (fasted).

     

European reference method for the in vivo determination of metabolisable energy with adult cockerels: reproducibility, effect of food intake and comparison with individual laboratory methods

1. A common reference procedure adopted by several European laboratories to determine apparent metabolisable energy corrected to zero-nitrogen balance (AMEn) is described. 2. Reproducibility has been estimated by comparing results from 4 diets measured in 7 laboratories. The standard deviations between laboratories of dry matter, gross energy, Kjeldahl nitrogen and AMEn were respectively, on average, 11.29 g/kg, 0.242 MJ/kg, 1.56 g/kg and 0.380 MJ/kg dry matter; the corresponding coefficients of variation between laboratories were 1.27, 1.29, 4.39 and 2.92%. 3. Effect of food intake was tested by comparing AMEn from birds fed either 0.90 or 0.45 of ad libitum: the amount of food intake had a negligible effect on AMEn values. Endogenous energy losses corrected (EELn) or not (EEL) to zero nitrogen balance were estimated either by regression between excreted energy and ingested energy or in fasted and glucose-fed cockerels. EELn estimated by regression was, on average, 8.7 kJ/bird/d.; it was independent of diet composition. EEL and EELn determined in fasted or glucose-fed birds were higher than those determined by regression. 4. AMEn values measured by individual laboratory procedures were very close to those obtained by the reference method, except from laboratories using a tube feeding procedure, where deviations were probably a consequence of overestimated EEL.     

Effect of genetic line, sex of birds and the type of bioassay on the metabolisable energy value of maize

1. Experiments were conducted to determine the differences in the energy utilisation of adult hens and cockerels of a layer (Rhode Island Red) and a broiler line (Cornish). The effect of 2 different precision-feeding methodologies (wet and dry-feeding) were also compared. Birds were fasted for 24 h, precision fed with 35 g dry or 33.5 g wet corn and fasted for a further 48 h period. Excreta were collected during this period. 2. Non of the parameters (method, sex, line) had a significant effect on the ME content of maize. However, a significant interaction was found between the sex of the birds and the methodology used. Females of both genetic lines utilised the energy content of maize more efficiently than males. The opposite was found when the wet precision-feeding method was used. 3. Weight loss and endogenous energy excretions (EEL) of birds were also effected by sex and genotype. Cockerels of both lines had significantly greater EEL than females. However, since hens lost less nitrogen, the nitrogen corrected EEL (EELn) was higher for the hens.     

鹅和鸡4种常用饲料原料的代谢能比较

本试验旨在比较鹅和鸡常用饲料原料的代谢能差异.选用体重为(3.76±0.23)kg的成年扬州鹅(公)和体重为(2.57±0.17)kg的成年新扬州鸡(公)各10只,采用Sibbald真代谢能法测定玉米、豆粕、稻谷、麦麸4种常用饲料原料的代谢能值,内源能测定采用饥饿法.结果表明:玉米、豆粕的表观代谢能(AME)鹅与鸡差异不显著(P＞0.05),真代谢能(TME)鹅显著低于鸡(P＜0.05);而稻谷、麦麸的AME鹅显著高于鸡(P＜0.05),TME鹅与鸡差异不显著(P＞0.05).每小时内源能排出量,除强饲豆粕条件下鹅略高于鸡但差异不显著外(P＞0.05),强饲其他3种饲料条件下,鹅均显著高于鸡(P＜0.05).由此表明,鹅的饲料代谢能与鸡的并不完全相同,部分饲料的代谢能鹅和鸡之间存在显著差异,并且鹅的内源能排出量高于鸡.     

Influence of level of feed input and procedure on metabolisable energy and endogenous energy loss (EEL) with adult cockerels

1. Two experiments were performed to study the relationship between apparent metabolisable energy (AME) and true metabolisable energy (TME) values at different feed intakes. Rhode Island Red (RIR) adult cockerels were used in two bioassays, under standard conditions. 2. In the first experiment (precision feeding) the birds were not fed for 24 h and then various quantities of maize were fed. There were 6 replicates per treatment. Droppings voided during the 48 h of the experimental period were collected and assayed for gross energy and nitrogen. 3. In the second experiment, each bird was given a 3-d adaptation period, fasted for 24 h and then given maize as an admixture (conventional addition method: CAM) to the same rations as those used in the first experiment. During the 3 d of the experimental period, droppings were collected and frozen for chemical analysis. 4. The results showed that mean metabolisable energy (ME) values obtained by the precisionfeeding procedure were higher than those obtained by CAM. The endogenous energy loss (EEL) (FE m + UE e ) determined by precision feeding was lower than that given by CAM. 5. It was concluded that the method of feeding does not influence ME of maize at different feed inputs. However, differences among intercepts of the regression between ME and feed input suggest that EEL varies at different maize inputs. 6. The optimum maize quantity was approximately 35 to 40 g for adult RIR cockerels by both procedures.     

Energy and nitrogen metabolism of diseased chickens: interaction of Ascaridia galli infestation and vitamin A status.

1. Effects of Ascaridia galli infection on the energy and nitrogen (N) metabolism were studied on groups of 5 cross-bred cockerels aged about 5 weeks and given a diet deficient or adequate in vitamin A at two levels of feeding in respiration chambers. 2. Metabolisability of dietary energy was 67% and N retention 33% in infected chickens compared with 71 and 41% respectively, in uninfected chickens. 3. Maintenance energy requirement of vitamin A-deficient birds was 882 kJ/kgW d compared with 998 kJ/kgW d for normal birds. N balance of the deficient chickens was also less when compared at the same energy balance. Infection did not affect maintenance energy requirement nor N balance. 4. Starvation heat production of infected chickens (619 kJ/kgW d) was higher than that of uninfected controls (586 kJ/kgW d). When infection treatments were combined, vitamin A-adequate chickens had a higher heat production (615 kJ/kg d) than the vitamin A-deficient (580 kJ/kgW d). Endogenous N excretion (mg/gW) was less in vitamin A-deficient than in adequate, starved birds. 5. Deficient chickens had undetectable liver reserves of vitamin A and only very low plasma concentrations. There was a difference in the length of larvae (17 d after infection) associated with vitamin A status, and with level of feeding.     

The effect of previous exposure to dietary microbial phytase on the endogenous excretions of energy, nitrogen and minerals from turkeys

1. A precision feeding experiment was conducted with turkeys, which had previously been fed diets with or without phytase, to study the effects on the excretions of endogenous energy (EEL), nitrogen (ENL), amino acids (EAAL) and minerals. 2. Female turkeys (BUT 6) which had been fed one of 4 experimental diets (low P maize-soya diets (control, C), C + 250 international units of phytase/kg diet (FTU), C + 500 FTU and C + 2500 FTU) were used in this study. All birds were fasted and then given 50 mL of glucose solution at 46 d of age. Birds were allocated to individual metabolism cages in a randomised block design with 8 replicates for each of the 4 previously-fed diets. 3. The response of EEL and ENL to phytase pre-exposure was linear. An increase of 100 FTU reduced the EEL and ENL by approximately 1·6 kJ and 20 mg respectively. The results suggest that a minimum activity of phytase of 500 FTU is needed to initiate the reduction of these losses. 4. Pre-exposure to phytase reduced the EAAL, which was best described as a linear response with increasing phytase dose in the pre-study period. An increase of 100 FTU reduced the losses of total endogenous amino acids by approximately 225 mg. 5. In contrast to the results for endogenous energy losses, turkeys pre-exposed to phytase linearly increased their excretions of Ca and Mg with increasing phytase activity in the pre-study period. 6. The effects of feeding turkeys with supplementary phytase continued for at least 4 d after the diets were withdrawn. This suggests that exposure to phytase alters the functionality and secretions of the gastrointestinal tract, which may influence the nutritive value of diets fed immediately after.     

Effects of dietary protein concentration and corticosterone injections on energy and nitrogen balances and fat deposition in broiler chicks

Reducing dietary protein concentration in isocaloric diets consistently decreased nitrogen and energy excretion, and increased dry matter (DM), non-protein DM (NPDM), energy retention and fatness. There were significant correlations, negative between dietary energy-to-protein (E:P) ratio and nitrogen excretion and positive between the E:P ratio and the retention of DM, NPDM and energy. Nitrogen excretion was correlated with energy excretion, and NPDM retention with energy retention. Corticosterone injections increased fatness despite significantly increasing nitrogen and energy excretion. A positive relationship was observed in corticosterone-treated birds between nitrogen excretion on the one hand and the retention of DM and NPDM on the other. Increased food intake because of a low dietary protein concentration was not evident when a sorghum-based diet was used. Moreover, corticosterone injections increased neither the food intake nor the fatness of chicks fed this diet. Decreasing the protein concentration in diets containing identical metabolisable energy (ME) levels slightly, but significantly increased apparent ME values in three out of four experiments. Corticosterone injection did not affect this variable.     

The estimation of endogenous excreta and the measurement of metabolisable energy in poultry feedstuffs using four feeding systems,four assay methods and four diets

1. Four different methods (dual semi‐quick (DSQ), conventional, a true metabolisable energy (ATM) method and Farrell's rapid method) were used to measure in adult roosters the apparent metabolisable energy (AME) and true metabolisable energy (TME) of four maize‐based diets with bran inclusions of 0, 200, 400 and 600 g/kg

2. Daily food intakes per bird were 75 g (or ad libitum) (H), 35 g (M) and 10 g (L). AME values determined by DSQ, conventional and Farrell methods were not different at the two highest intakes but were depressed at L intakes. ATM method often gave different values from other methods, particularly at the lowest intake.

3. The linear relationships between food intake and excreta energy yielded intercept values of 13 to 32 kJ/d for three methods; but ATM method yielded intercepts of 31 to 52 kJ/d. In a separate experiment it was demonstrated that a linear model may not be the most appropriate fit to such data. Removal of data for the 10 g/d intake yielded linear regression equations with intercepts not significantly different from zero for the two continuous feeding methods (i.e. a zero estimate for endogenous urinary and metabolic faecal energy (EEL), but for the two methods using a single input after fasting, intercepts were almost always positive. This confirms Härtel's (1986) observation of the absence of EEL under continuous feeding but its ever presence using a TME assay.

4. Correction of AME for EEL to obtain TME tended to increase values for all diets and also within a diet with decreasing intakes. The effect of correcting AME to nitrogen balance (n) was to give AME_n values that were more consistent between diets and reduced differences between methods. For the conventional method differences between the three intakes on all diets were greatly reduced.

5. There is reason to be concerned about the many different metabol‐isable energy values obtained using the ATM method compared to the three other methods and the basis for correcting for endogenous excreta. It is concluded that because of the uncertainty of EEL values, their variation and application, the AME system should be retained.     

Influence of conditioning temperature on the performance, nutrient utilisation and digestive tract development of broilers fed on maize- and wheat-based diets

1. The influence of conditioning temperature on the performance, nutrient utilisation and digestive tract development of broilers fed on maize- and wheat-based diets was examined up to 21 d of age. The experimental design was a 2 × 3 factorial arrangement of treatments evaluating two grain types (maize and wheat) and three conditioning temperatures (60°C, 75°C and 90°C). Broiler starter diets, each based on one grain (maize or wheat), were formulated and pelleted at the three temperatures. 2. Increasing conditioning temperature decreased the body-weight gain and feed intake in wheat-based diets, but birds fed on maize-based diets conditioned at 60°C and 90°C had higher body-weight gain and feed intake than those fed on the diet conditioned at 75°C. Increasing conditioning temperature increased feed per body-weight gain in both grain-type diets but improved pellet durability index (PDI) only in wheat-based diets; PDI was unaffected in maize-based diets. 3. In wheat-based diets, increasing conditioning temperature decreased the ileal digestibility of nitrogen and starch. Ileal nitrogen digestibility of maize-based diets conditioned at 60°C and 90°C was higher than at 75°C. Starch digestibility was unaffected by conditioning temperature in maize-based diets. No effect of conditioning temperature was found for apparent metabolisable energy (AME). Increasing conditioning temperature decreased digestible protein and AME intakes in wheat-based diets but, in maize-based diets, birds fed on the diet conditioned at 75°C had lower digestible protein and AME intakes compared to those fed on diets conditioned at 60°C and 90°C. 4. Small intestine was longer in birds fed on diets conditioned at 75°C and 90°C compared with those fed on diets conditioned at 60°C. 5. Overall, the data suggest that while the effects of conditioning temperature on body-weight gain and feed intake of broilers to 21 d of age differed depending on the grain type, feed per body-weight gain was adversely affected by higher conditioning temperatures.     

Effect of protein and lysine levels in the diet on body gain composition and energy utilization in growing pigs

Eight replicates of four Large White littermate female pigs were used to evaluate the effect of protein and lysine levels in the diet on the efficiency of protein and energy utilization. In each replicate, one pig was slaughtered at about 20 kg live weight and the others received three diets that contained (per Mcal digestible energy) 37.5 and 2.00 g (diet pl), 37.5 and 2.35 g (diet pL) or 45.0 and 2.35 g (diet PL) of digestible protein and lysine, respectively. Pigs were slaughtered after a 7-wk period. Tissue and chemical composition of the gain and energy and nitrogen gain were determined by using the comparative slaughter technique. Metabolizable energy (ME) intakes were similar in the treatments. Pigs fed the pl diet had a smaller body weight and muscle gain and retained less nitrogen and more lipids than pigs fed pL and PL diets. The decrease in the level of nonessential nitrogen in the diet (pL vs PL) did not affect body weight and muscle gain and the amount of nitrogen retained in muscle tissues. However, pigs given the PL diet had a higher total nitrogen retention and a lower fat deposition and exhibited a higher heat production. For each gram of additional protein catabolized for energy purposes (PL vs pL), heat production was increased by 1.8 kcal. The amount of lysine per unit of muscle gain (38 g/kg) or protein deposited (120 g/kg) was independent of protein and lysine levels in the diet. Estimates of energy (indirect calorimetry) and nitrogen (balance technique) retention were also obtained on the same animals; results were comparable with data obtained by direct measurements.     

Influence of food input and procedure of determination on metabolisable energy and digestibility of a diet measured with young and adult birds

Two series of balance trials were performed with adult cockerels and with broiler chickens during their 5th week of life, and one with adult colostomised hens. The latter served to determine the digestibility of protein of the diet under test. All birds were fed the same diet with one exception: in the case of colostomised hens limestone (100 g/kg) was added before feeding. The main purpose of the experiments was to compare the Sibbald procedure for determining the so-called true metabolisable energy (TME) with apparent metabolisable energy (AME) or TME values obtained by applying a conventional addition method (CAM). The results showed that the Sibbald procedure was less precise than CAM. The Sibbald procedure delivered incorrect TME and AME values, the reason for this being the use of starved birds. This led not only to wrong intercepts but also to misleading regression coefficients in the regression equations used to calculate energy excretion on food intake. In CAM there existed no differences between AME and TME. This was not true for the Sibbald procedure, in which AME values differed considerably from TME values. Because of the errors inherent in the Sibbald procedure it is suggested that it should be replaced by CAM, in which several feeding inputs should be used.     

Prediction of ingredient quality and the effect of a combination of xylanase, amylase, protease and phytase in the diets of broiler chicks. 1. Growth performance and digestible nutrient intake

1. A total of 2208 broiler chicks were used in two growth experiments (8 treatments and 12 replicate pens in each experiment) to assess the effects of xylanase, amylase, protease and phytase in maize-based diets. 2. A positive control diet was formulated containing adequate nutrient concentrations. A negative control diet was formulated to contain approximately 628 kJ/kg, 0.13%, 0.12% and 1 to 2% less metabolisable energy (ME), phosphorus (P), calcium (Ca) and amino acids, respectively, than the positive control. In addition, two further negative control diets that contained 167 or 334 kJ/kg more ME, respectively, than negative control 1 were formulated. 3. A further 4 dietary treatments were made by supplementing each of the 4 negative control diets with a combination of xylanase, amylase, protease and phytase, resulting in 8 dietary treatments in a 4 by 2 factorial arrangement. 4. The scale of the removal of energy, P, Ca and amino acids from the positive control diet was determined using least square models based on in vivo data for both the xylanase/amylase/protease cocktail and for phytase and it was predicted that performance of birds fed on negative control 1 would be returned by supplemental enzymes to that of those fed on the positive control. 5. In both experiments there was a significantly poorer performance in birds fed on the negative control 1 than in those fed on the positive control. The poorer weight gain and feed conversion ratio could be attributed in part to a reduced intake of digestible energy, P, nitrogen (N) and amino acids associated with birds fed on the negative control diet. 6. Supplementation of the negative control diets with the enzyme combination returned performance to that of the positive control in both experiments. 7. These data indicate that exogenous xylanase, amylase, protease and phytase can be used successfully in a strategically formulated low nutrient density diet to maintain performance to that of birds fed on a nutritionally adequate diet.     

Digestibilities of amino acids in maize, wheat and barley meals, determined with intact and caecectomised cockerels

1. Maize, wheat and barley meals, and a protein-free diet were each force-fed to 24 intact and 24 caecectomised adult cockerels. For each test, birds were starved of solid food for 48 h, fed, and then excreta collected for 48 h. 2. Quantities of nitrogen (N) and amino acids excreted after feeding the protein-free diet did not differ between intact and caecectomised birds. 3. True digestibility coefficients of N and amino acids did not differ between intact and caecectomised birds. 4. Differences between cereals in apparent digestibility of amino acids were inconsistent and more readily attributed to differences between amino acid intake than bioavailability. 5. Differences between cereals in true digestibility of amino acids were confined to higher values for N, aspartic acid, alanine and leucine in maize than in barley or wheat meals.     

Endogenous losses of energy and amino acids in birds and their effect on true metabolisable energy values and availability of amino acids in maize

1. Endogenous losses of amino acids (EAAL) and energy (EEL) were determined in unfed adult cockerels. The intercepts of linear regression analysis were determined using 44 birds precision-fed on maize. During the experimental period (48 h), excreta of birds were collected, and the samples of maize and the excreta were dried, ground and assayed for gross energy and amino acids. 2. The EAAL and EEL in unfed cockerels influenced true available amino acid (TAAA) values. Therefore, the intercept of regressions showed an increase in TAAA values of maize. 3. The results indicated that there was no significant difference between the data obtained for EEL from the unfed birds and from regression analysis so, the figure from regression analysis could be used for calculating the true metabolisable energy (TME) value of maize. 4. The calculated EAAL from regression analysis caused an increase in the TAAA value in maize. The amounts of metabolic and endogenous amino acid excretions varied in voided excreta from unfed birds. These differences would be related to genetics, age, sex and environmental temperatures.     

Relationship between food consumption and energy and nitrogen utilisation by chicks given varying amounts of standard and leucine-, isoleucine- and valine-deficient diets

The effect of different amounts of food, varying from below to above the rate of voluntary intake, was studied in chicks using a standard diet and diets containing only half the recommendation concentrations of leucine, isoleucine or valine. Irrespective of diet the body weight gain of the chicks increased with increasing food consumption. The body weight gain of chicks given the leucine-deficient diet was similar to that of chicks given the same amount of the standard diet. In contrast, the body weight gains of chicks given either the valine- or isoleucine-deficient diet were significantly less than that of chicks given the same amount of the standard diet. When the food intakes of the birds were similar the differences in body protein and water contents of the birds fed the different diets reflected differences in body weight gains, whereas body fat content was affected in the reverse manner. Retention and retention rate of dietary energy increased as food consumption increased. This was particularly evident in chicks given the isoleucine-deficient diet, followed by those given the valine-, leucine-deficient and standard diets. For all diets, the amounts of nitrogen retained and nitrogen retention rate (N retained/N consumed) increased in line with body weight gain. The metabolisable energy values of the diets were similar, except for the isoleucine-deficient diet which had a significantly higher metabolisable energy value than the standard valine-deficient diets.     

High versus low protein diets to mink--postprandial plasma urea and creatinine response, osmotic load and pattern of nitrogen and electrolyte excretion.

Nitrogen balance, pattern of excretion of nitrogenous end-products, endogenous urinary N excretion, postprandial plasma urea and creatinine, osmotic load, urinary electrolyte excretion and water intake/output relationships were studied in 12 adult female mink fed a high protein diet (HP; n = 6) providing about 155 g protein/kg or a low protein diet (LP; n = 6) providing about 95 g protein/kg. Two balance periods of each 3 d were used and diets were fed raw or cooked. After the last balance period followed a 48 h fasting period. Postprandial plasma urea and creatinine were studied for 48 h following a test meal given after an overnight fast. Osmotic load was determined based on collection of non-acidified urine carried out during 48 h. Level of protein supply did not affect N balance, being close to zero, whereas slightly negative balances were achieved for fasting animals. Protein supply was clearly reflected in excretion of urinary urea and allantoin but not in creatinine and uric acid. Endogenous urinary N excretion was estimated by a second order regression equation giving an intercept of 280 mg/kg0.75. Post-prandial plasma urea concentrations were strongly influenced by protein supply, HP animals having substantially higher peaks than LP animals, but values returned to fasting values within 24 h after the test meal. Plasma creatinine followed a biphasic pattern with a peak about 2 h after feeding and a nadir approximately 6 h after feeding. Physical form of diet influenced postprandial urea, animals fed raw diets having a higher peak, but not creatinine. The HP diet provided almost the double osmotic load of the LP diet and a corresponding increase in urine volume. The resulting water balances were identical irrespective of diet, showing that water intake/output relationships are very accurately regulated.     

True metabolisable energy values of some feedingstuffs

1. The apparent metabolisable energy (AME) and the true metabolisable energy (TME) contents of some feedingstuffs were determined with cockerels. The test materials consisted of feed‐grade lentil, lentil bran and wild vetch seed.

2. The average values of nitrogen lost, endogenous energy losses (EEL) and endogenous energy losses corrected to zero‐nitrogen balance (EEL_n) were found to be 1.18 g, 62.13 kJ and 21.51 kJ/bird/48h, respectively, from adult cockerels given an energy supply as 50 g glucose during starvation.

3. The nitrogen‐corrected apparent metabolisable energy (AMEn) values for feed‐grade lentil, lentil bran and wild vetch seed, respectively, were 6.84, 3.05 and 14.31 kJ/g dry matter. The nitrogen‐corrected true metabolisable energy (TME_n) values for the respective feedingstuffs were 7.44, 3.65 and 14.90 kJ/g dry matter.