A comparative study between mature ostriches (Struthio camelus) and adult cockerels with regard to the true and apparent digestibilities of amino acids

1. A study was conducted to compare apparent and true digestibility of amino acids in a high protein experimental diet between young ostriches (7 months of age) and cockerels.

2. A mean value for true digestibility of amino acids (TAAD) of 0.837 ± 0.0073 (range 0.780 to 0.862) was derived for ostriches, compared with a mean value of 0.795 ± 0.0258 (range 0.723 to 0.825) for cockerels.

3. True retention of dietary protein was 0.646 ±0.0114 and 0.609 ±0.0643 for ostriches and cockerels respectively.

4. Results in the present study produced evidence that the method for determining metabolisable energy values of ingredients for ostriches is also suitable for measuring the digestibility of amino acids.

5. It was concluded that accurate diet formulation for ostriches requires the assessment of amino acid digestibilities for individual ingredients, because values derived from poultry would underestimate digestibilities for ostriches.     

Sudies on low metabolisable energy wheats for poultry using conventional and rapid assay procedures and the effects of processing

1. A significant proportion of wheat cultivars grown in New South Wales had low apparent metabolisable energy (AME) values (< 13.0 MJ/kg dry matter) for growing broilers when determined by the conventional total collection technique.

2. The low AME was due to a reduced starch digestibility and was not improved by grinding the wheat finely or by steam pelleting the diet.

3. Higher AME values were obtained when determinations were made with adult cockerels than with growing broilers when the conventional technique was used.

4. AME values determined using a rapid bioassay technique (Farrell, 1978) with growing broilers or adult cockerels were considerably higher than values determined using the conventional procedure with growing broilers.

5. Inter‐laboratory studies showed that the true metabolisable energy (TME) assay gave reproducible values for individual and blended wheat samples, but that these values were higher than AME values determined by the conventional procedure. Similar TME values were found with growing broilers and adult cockerels.     

Influence of caecectomy and dietary protein concentration on apparent excreta amino acid digestibility in adult cockerels

1. The influence of caecectomy and dietary crude protein content (50, 100, 150, 200 and 250 g/kg diet) on the apparent excreta amino acid digestibilities in adult cockerels fed on semi‐purified diets containing soyabean meal (SBM) or cottonseed meal (CSM) as the sole source of protein was investigated.

2. Caecectomy had no influence on the apparent digestibilities of most amino acids in SBM, the exceptions being histidine, arginine and lysine, but lowered the apparent digestibility of amino acids in CSM.

3. The protein content in assay diets has a strong influence on the apparent amino acid digestibility values for poultry. Apparent values are lower when the dietary protein content is low.

4. The use of a single endogenous amino acid output value, generated by regression analysis or protein‐free diets, for true digestibility adjustments across a wide range of protein intakes is questioned. In particular, such an application will penalise estimates of apparent digestibility when the dietary protein content is high.     

Interactions between dietary fat type and xylanase supplementation when rye‐based diets are fed to broiler chickens 2. Performance,nutrient digestibility and the fat‐soluble vitamin status of livers

1. The interactions between dietary fat type and xylanase supplementation of rye‐based diets were investigated using a 2×2 factorial design in which a rye‐based diet (610 g rye/kg) was combined with 100 g/kg of soya oil or beef tallow, with or without xylanase supplementation at 3000 IU/kg, and fed to 1‐d‐old male broilers for 35 d. Growth, nutrient digestibility and AMEn values were determined and the vitamin status of livers assessed at various ages.

2. There were significant interactions between crude fat and xylanase supplementation on the faecal digestibility of crude fat and crude protein. Fat digestibility was improved by xylanase in both fat type groups but to a greater extent for the tallow diets. However, the effects were found to be significant only for oleic, linoleic and linolenic acids. Similarly, protein digestibility and AMEn values were significantly improved by xylanase, but only for the tallow diet.

3. Heal digestibility of nitrogen and amino acids also were affected by enzyme for both fat type diets, the effect generally being more pronounced for the tallow diet.

4. The deposition of the fat soluble vitamins A and E in livers was significantly increased by xylanase supplementation and was also better for soya oil than for tallow.

5. Xylanase supplementation increased the digestibility of insoluble pentosans whereas for the soluble pentosans the opposite effect was noted.

6. Without xylanase supplementation the tallow‐based diet caused high mortality. Liveweight gain and the efficiency of food utilisation were greatest in the soya oil‐based, xylanase‐supplemented diet, followed by the unsupplemented soya oil‐, supplemented tallow‐ and unsupplemented tallow‐based diets.     

Effect of tannins on starch digestibility and tmen of triticale and semipurified starches from triticale and field beans

1. The effects of field bean tannin‐containing hulls (T‐hulls), non‐tannin hulls (NT‐hulls) and tannin extract on starch digestibilities and TMEn of triticale and semipurified starches from triticale and field beans were evaluated with adult cockerels and 3‐week‐old‐chicks.

2. For both cockerels and chicks, the digestibility and TMEn of semipurified starches from triticale were higher than those from beans. Starch digestibilities of triticales (range 99.1 to 97.7%), of semipurified starches from triticales (range 96.5 to 89.9%) and from field beans (range 75.4 to 71.6%) were similar for both cockerels and chicks.

3. The addition of NT‐hulls improved, in general, the digestibility of semipurified starches for both chicks and cockerels, which suggests that fibre improves the digestion of semipurified starches.

4. The effects of tannins of T‐hulls on semipurified starch from beans and from triticale were different. Tannins always decreased the digestibility and TMEn of semipurified starch from field beans but only decreased the digestibility and TMEn of semipurified starch from triticale when fed to chicks, but not when fed to cockerels.

5. The addition of tannin extract always decreased the digestibility of semipurified starches by a greater amount than T‐hulls, which supports the idea that the effect of tannins depends on the quantity of tannin ingested.     

Digestibility studies in broiler chickens: Influence of genotype,age, sex and method of determination

1. The influences of genotype, age and sex on droppings digestibility coefficients of a compound food were studied using male and female broiler chickens of three different genotypes at 2, 4 and 6 weeks of age.

2. Because the traditional method of determination of droppings digestibility coefficients of nitrogen may lead to systematic errors in estimating the feeding value of foodstuffs, a method is proposed to determine the ileal digestibility coefficients. The ileal method is compared with the droppings method for a mixed food and for two foodstuffs: wheat and solvent‐extracted soyabean meal.

3. Birds selected for efficient food conversion showed distinctly higher digestibility coefficients for all nutrients than birds selected for high growth potential or birds from a commercial strain.

4. The influence of age on digestibility coefficients was not consistent.

5. Female birds showed digestibility coefficients which were, in general, 3% higher than those of male chickens.

6. Interactions between genotype and sex and between genotype and age for energy metabolisability were the only interactions observed for digestibility measurements.

7. The method of determination influenced the amino acid digestibility coefficients of the mixed food and the relative feeding values of wheat and soyabean meal.

8. It is important to use well defined animals (genotype, sex, age) in evaluating foodstuffs.

9. The preferred method for determination of digestibility coefficients of nitrogen and amino acids is based on ileal sampling, although the differences in amino acid digestibility coefficients were small between methods.     

Rapid determination of metabolisable energy of foods using cockerels

1. Adult cockerels were trained to consume their daily food allowance of about 100 g in 1 h. Excreta were collected for the next 24 h and the metabolisable energy (ME) content of the diet was determined.

2. Two different diets were used to study effects of ME on adaptation to diet. Repeatable estimates of ME were obtained without a period of adaptation.

3. No difference in ME was found when a test diet was fed to adult cockerels for 1 h, or fed continuously and excreta collected over 5 d. The conventional total collection method of determining ME using groups of growing chickens yielded similar results.

4. Excreta collected between 24 and 48, or 48 and 72 h post‐feeding yielded constant energy values following feeding of two different diets, indicating that all excreta from the 1‐h feeding were voided during the next 24 h.

5. The method is precise and results can be reported 36 h after receipt of food sample.     

Interactions between xylanase and glucanase in maize-soy-based diets for broilers

1. The effect of various doses of xylanase and glucanase on the performance and ileal nutrient digestibility of broiler chickens fed on maize/soy-based diets was evaluated.

2. A total of 960 male broilers were used in separate growth and digestibility trials with each involving 10 treatments and 6 replicates. The 10 treatments included a positive control reference diet, a negative control diet with a lower energy density and 8 further diets where xylanase and glucanase were added to the negative control, individually and in combination.

3. Birds which received the negative control diet returned poorer (6 points; P < 0·05) feed conversion ratios compared with those fed on the positive control, confirming the lower energy density of the negative control diet. Ileal digestibility of energy determined at 21 and 42 d was also significantly lower for the negative control compared with the positive control. At d 21 birds that received the negative control diet returned lower ileal amino acid digestibility (for most amino acids) compared with their counterparts fed on the positive control whereas at d 42 this effect was not apparent.

4. Supplementation of the negative control with both glucanase and xylanase improved feed conversion ratio (FCR) and ileal nutrient digestibility. When both enzymes were added simultaneously a sub-additive effect (i.e. simultaneous use resulted in benefits greater than either enzyme independently but less than the sum of the individual effects) was observed, with the best performance achieved with the combination of xylanase (16 000 BXU/kg) and glucanase (30 000 BU/kg).

5. It can be concluded that the removal of oil to accommodate the anticipated energy digestibility improvement with enzymes can have deleterious effects on FCR and ileal amino acid digestibility in young broilers which enzymes may not adequately mitigate. Thus, in order to maximise the response to non-starch polysaccharide degrading enzymes in maize/soy-based broiler diets, it may be beneficial to consider a combination of xylanase and glucanase and to apply moderation when removing added fat in the starter diets.     

Influence of a microbial phytase on the performance and the utilisation of energy,crude protein and fatty acids of young broilers fed on phosphorus-adequate maize- and wheat-based diets

1. The effects of microbial phytase on the performance and nutrient utilisation in broilers fed on phosphorus-adequate starter diets were examined in this study. The effect of phytase on the apparent ileal digestibility of fatty acids was of particular interest. Two grain types (maize and wheat) and two inclusion concentrations of a phytase enzyme from Escherichia coli expressed in Schizosaccaromyces pombe (0 or 500 phytase units (FTU)/kg of feed) were evaluated in a 2 × 2 factorial arrangement of treatments.

2. Supplemental phytase improved the weight gain and feed per gain, but had no effect on the feed intake of young broilers receiving phosphorus-adequate diets.

3. Phytase supplementation improved the apparent ileal digestibility of nitrogen and phosphorus in both diet types. Phytase supplementation tended to improve the apparent ileal digestible energy in wheat-based diets, but had no effect on the apparent metabolisable energy in both diet types.

4. Supplementation of phytase increased the apparent ileal digestibility of fat, with similar effects for the different fatty acids measured. Increments on ileal fat digestibility due to phytase were not dependent on the type of diet.

5. Dietary supplementation of microbial phytase enhanced not only the digestibility of phosphorus, but also that of nitrogen and fat, exhibiting increased ileal digestibility for all fatty acids in P-adequate maize- and wheat-based diets.     

Nutritional value of narrow-leafed lupin (Lupinus angustifolius) for broilers

1. Two experiments were conducted to evaluate the nutritional value of three cultivars (Wallan, Tanjil and Borre) of narrow-leafed lupin (Lupinus angustifolius) for broilers.

2. In Experiment 1, the apparent metabolisable energy (AME) and the apparent ileal amino acid digestibility of the three cultivars were determined. The cultivar effects were not significant for AME and apparent ileal amino acid digestibility coefficients. In general, amino acids in narrow-leafed lupin were well digested, with the notable exception of methionine. Among the indispensable amino acids, arginine had the highest digestibility coefficient (0·92–0·95), while the lowest was for methionine (0·74–0·83).

3. In Experiment 2, using the energy and digestible amino acid values determined in Experiment 1, diets containing 200?g/kg of the three lupin cultivars were formulated and the effects of feeding these diets on the performance and the digestive tract development of broiler starters were investigated.

4. Weight gain, feed intake and feed per gain of broilers fed narrow-leafed lupins diets were similar to those fed on the maize-soy basal diet. The performance of birds fed on diets containing different cultivars of lupins was also similar. Birds fed on lupin diets had similar excreta scores to those fed on the basal diet.

5. Inclusion of 200?g/kg lupins in broiler diets had no effects on the relative weight and length of the intestinal tract. Broilers fed on lupin diets, however, had higher relative weights of liver.

6. These results suggest that narrow-leafed lupins are good sources of protein, but poor sources of AME and sulphur-containing amino acids. It is concluded that, when diets are properly balanced in terms of AME and digestible amino acids, lupins can be included at 200?g/kg inclusion level in broiler starter diets with no adverse effects on performance.     

Dietary selection of protein and energy by pullets and broilers

1. White Leghorn pullets and sexed broilers were allowed a free choice of two “ split‐diets “ which were concentrated sources of either crude protein (463 g/kg diet) or energy (13.32 to 14.00 MJ/kg diet).

2. Pullets receiving these two diets displayed a slower, but more uniform growth rate than did birds offered a single conventional diet. Up to 11 weeks of age, control birds consumed significantly more protein while the converse was true from 11 to 20 weeks. These differences are discussed in relation to the stage of sexual maturity.

3. Broilers offered the split‐diets grew more slowly and had an inferior food conversion ratio compared with control birds fed on a two‐stage rearing programme.

4. Among the broilers offered split‐diets, the usual sex differences were not observed for weight gain or carcass fat content.     

Use of ambroxol and bromhexine as mucolytics for enhanced diffusion of furaltadone into tracheobronchial secretions in broilers

1. Ambroxol and bromhexine were evaluated as mucolytics and to enhance the passage of furaltadone into tracheobronchial secretions (TBS) in chronic complicated respiratory disease‐affected broilers.

2. Viscosity of TBS was noticeably increased in the ambroxol‐treated birds and only slightly increased in the bromhexine groups; however, the physical (nature) of TBS was superior in the ambroxol‐treated broilers.

3. There was a clear increase in the passage of furaltadone into tracheobronchial secretions only in the ambroxol‐treated birds.

4. Everyday use of ambroxol in broilers is discussed.     

Hydrolysed feather protein as a source of amino acids for broilers

1. The inclusion of 25 g hydrolysed feather meal (HFM) in each kilogram of diet (floor experiment) and 60 g/kg (cage experiment) did not depress performance.

2. Chemical tests indicated 72.5% of the total lysine in HFM was available.

3. Total lysine concentration of 11.3 g/kg diet maximised performance during the period 0 to 34 d.

4. Reduction in dietary methionine content during the period 0 to 34 d from 4.2 g/kg to 3.2 g/kg did not depress performance on diets containing 60 g HFM/kg.

5. The results indicate that at least 57% by weight of the total sulphur amino acid requirement of broilers can be provided by cystine.     

The effect of heat treatment and enzyme supplementation on the nutritive value of barley for broiler chicks

1. The effect of heat treatment and enzyme supplementation on the nutritive value of barley was studied.

2. In only one experiment was weight gain significantly improved when the barley was heated.

3. Autoclaving barley at 120 °C for 30 min reduced dietary dry matter digestibility and treating the barley with dilute acid before heating had no effect on its nutritive value.

4. Supplementing diets containing commercial barley with a‐amylase produced slightly conflicting results in that there was an improved weight gain, food conversion efficiency and digestibility value in two of three experiments.

5. The digestibility and metabolisable energy values of a North American six‐row spring barley (Glacier) were significantly improved by enzyme supplementation.

6. The effect of the enzyme on diets containing a high amylose barley (Glacier Pentlandfield) was positive but not significant.     

Influence of site and variety on starch,hemicellulose and cellulose composition of wheats and their digestibilities by adult cockerels

1. It has been shown that both the variety of wheat and the environment under which growth took place influenced the quantities of starch and cell wall carbohydrate contents of wheat.

2. The different varieties of wheat investigated contained different proportions of water‐soluble to water‐insoluble hemicelluloses.

3. By comparison of the arabinose to xylose ratios it was concluded that water‐soluble and insoluble arabinoxylans of wheat were branched to the same degree.

4. Starch from six wheat varieties grown in the U.K. was very well digested by adult cockerels and true metabolisable energy values of the wheats were high.

5. Small amounts of cell wall carbohydrates were digested by adult cockerels.     

The development of a specific appetite for calcium in growing broiler chicks 1

1. Growing broilers were fed on a calcium‐deficient diet and allowed access to a separate calcium source.

2. When housed in a group, they consumed enough from the calcium source to supplement their diet adequately.

3. Caging individually inhibited the development of the calcium appetite in most birds even with visual contact between birds and colour cues to the calcium supplement.

4. Birds which had learned to consume a calcium supplement in a group continued to consume the supplement after being caged individually. Intake of the calcium source decreased immediately after the calcium‐deficient diet was replaced with one adequate in calcium, suggesting the existence of a physiological control mechanism for calcium intake.     

Some factors affecting urinary and Faecal nitrogen loss by chickens fed on a protein‐free diet

1. In adult colostomised cockerels, the rates of urinary and faecal nitrogen loss were measured when feeding low‐ and high‐energy, protein‐free diets after a preliminary period during which diets of differing energy and protein contents had been fed.

2. Urinary nitrogen excretion increased with increasing protein and decreasing energy in the preliminary diet.

3. Urinary nitrogen excretion was high during the first 3 d of feeding a high‐energy, protein‐free diet, decreased rapidly during the next 3 d and thereafter become relatively constant. However, in the case of a low‐energy, protein‐free diet, urinary nitrogen excretion gradually declined throughout the trial period of 15 d, resulting in increased urinary nitrogen excretion.

4. After a 3‐d period of adjustment faecal nitrogen loss from birds fed on a protein‐free diet was relatively constant under the conditions examined.     

Effects of a beta‐adrenergic agonist clenbuterol) on performance,carcase composition,hepatic microsomal mixed function oxidase and antibody production in female broilers treated with or without corticosterone

1. Beta‐adrenergic agonist (Clenbuterol, 0.33 mg/kg) and corticosterone (10 mg/kg) were incorporated into a diet based on maize and soyabean meal. Their effects on performance, carcase composition, hepatic microsomal mixed function oxidase and antibody production were investigated in female broilers.

2. Dietary corticosterone reduced the titre to sheep red blood cells, while it was unchanged by clenbuterol.

3. Clenbuterol exerted a promoting effect on gain‐to‐food ratio, carcase protein and hepatic microsomal cytochrome P‐450 content.

4. Addition of clenbuterol to the corticosterone‐containing diet prevented the increase in abdominal fat weight and uric acid excretion induced by corticosterone, but did not affect total fat mass.

5. The results showed that clenbuterol reduced abdominal rather than carcase fat and prevented protein degradation in the body when chicks were treated with corticosterone. Clenbuterol also influenced the content of cytochrome P‐450, but not the humoral immunity.     

Growth hormone and prolactin secretion in growing domestic fowl: Influence of sex and breed

1. Plasma growth hormone (GH) and prolactin concentrations were measured between 1 and 24 weeks of age in both sexes of a laying strain of chickens and from 1 to 9 weeks of age in broiler cockerels.

2. GH and prolactin concentrations were highest in young birds and higher in males than in females.

3. In both sexes GH and prolactin concentrations were correlated inversely with age and body weight and positively with relative weight gain.

4. Differences in growth rate between broilers and layers were related to differences in blood GH concentrations.

5. Water deprivation for periods of 6, 12, 18 or 24 h increased plasma prolactin markedly but did not affect GH secretion significantly.     

The choline and sulphur amino acid requirements of broiler chickens fed on semi‐purified diets

1. Growth and food conversion efficiency of broilers were reduced at low dietary choline concentrations. These effects were accentuated by low dietary total sulphur amino acids (TSAA).

2. Increased mortality, perosis and other pathological changes involving a number of tissues were observed in birds fed on a low‐choline diet.

3. Methionine replaced part of the dietary requirement for choline at low dietary choline concentrations.

4. High dietary concentrations of choline (> 1 750 mg/kg) increased the requirement for dietary TSAA.

5. Increasing the dietary choline while maintaining the TSAA at an inadequate level may decrease performance.