Interactions between fats of differing chemical content: apparent availability of fatty acids

1. Tallow (A) and rape oil (E) were obtained for evaluation. They were blended in the ratios A95:E5, A90:E10 and A80:E20. The three blends together with the two pure fats were each included at 40, 80 and 120 g/kg into a basal diet. 2. The experimental diets were evaluated for apparent availability (g/kg) of the fatty acids palmitic (C16:0), stearic (C18:0), oleic (C18:1) and linoleic (C18:2) using 6 replicates of a cage of two male broiler chicks 14 d old and 8 replicates of a cage of one Rhode Island cross cockerel approximately 1 year old. Diets were fed for 72 h then removed for 24 h. This was followed by a 48 h period when food was available ad libitum and a further 24 h starvation. A total collection of excreta was undertaken for the latter 72 h period. 3. Evaluation of apparent available fatty acid (AAFA g/kg fatty acid) was achieved by linear regression. 4. All results indicated a progressive increase in AAFA with both chicks and adults for C16:0 and C18:0 with increasing proportions of the more unsaturated rape oil in the fat blends and for C18:1 and C18:2 with chicks. 5. Evaluation of AAFA by quadratic regression indicated an additional effect of rate of inclusion for C16:0 and C18:0 with chicks and adults and for C18:1 with chicks.     

Apparent metabolisable energy values of fats for broiler chicks

Seven fats were included at 30, 60 and 90 g/kg (experiment 1) and at 20, 40, 60 g/kg (experiment 2) in a semi-synthetic fat-free diet and in a practical diet respectively. Apparent metabolisable energy (AME) was evaluated with 6 replicate cages each with three Ross 1 cockerel chicks 8 d old. Diets were fed for 11 d and a total collection of excreta undertaken for the last four. There was no significant departure from linearity in the response of dietary AME to added fat, indicating no interactions between basal diet and added fat. In experiment 3 one fat was evaluated at 10 rates of inclusion (10 g/kg to 100 g/kg in 10 g increments) in both a semi-synthetic fat-free basal and a practical basal diet. A significant departure from linearity in the response of dietary AME to added fat was detected but there was no significant fat X basal diet interaction. In experiment 4 twelve commercially available fat blends were each evaluated at 10 rates of inclusion (15 g/kg to 150 g/kg in 15 g increments) in a practical basal diet. Significant departures from linearity in the responses of dietary AME to added fat were observed with some of the fats. It was concluded that the AME of fats mat be determined from multi-level assays by interpolating the quadratic relationships derived.     

Influence of age, chemical composition and rate of inclusion on the apparent metabolisable energy of fats fed to broiler chicks

1. Vegetable oil (VO) and tallow (T) were evaluated at rates of 25, 50, 75, 100 and 125g/kg in a basal diet with broiler chicks aged 1.5, 3.5, 5.5 and 7.5 weeks of age using a total collection period of 72 h. 2. Apparent metabolisable energy, corrected to zero nitrogen retention (AMEN, MJ/kg) and apparent fat availability (AFA, g/kg) of the experimental diets were employed to estimate the dietary energy values of fats, by linear and quadratic regression. 3. AME of fats, determined from AFA, had smaller standard errors than those determined from AMEN. 4. There was a marked increase in the AME of fats from 1.5 to 3.5 weeks of age; thereafter, the improvement was less pronounced. 5. Rate of improvement in fat AME with age was greater with T than VO.     

Comparison of two direct bioassays using 3-week-old broilers to measure the metabolisable energy of diets containing cereals high in fibre: differences between true and apparent metabolisable energy values

1. Nitrogen-corrected apparent and true metabolisable energy contents (AMEN and TMEN) of 12 diets, containing different amounts of maize, wheat, barley and rye, barley with beta-glucanase and maize with 0.05 g/kg guar gum were measured using 3-week-old male broilers. 2. The AMEN method involved: 4 d of dietary adaptation, 24 h of starvation, 54 h of ad libitum feeding, 24 h of starvation and daily total droppings collection. TMEN was measured after a 48 h starvation period followed by 2 d of tube-feeding two doses of 15 g of the diets and quantitatively collecting all the droppings after 48 h of starvation. The endogenous energy losses (EELN) were measured after tube-feeding 8 chickens with 30 g of glucose, also over 2 d. 3. The results show that a significant interaction exists between the nature of the diets and the method used to measure metabolisable energy. Differences between TMEN and AMEN values ranged from 1.03 to 1.98 MJ/kg dry matter. These differences were positively correlated with the total pentosan contents of the diet (r = 0.94), the natural logarithm of the viscosities of the water extracts (r = 0.87), the sum of the contents of total pentosans and total beta-glucan (r = 0.85), the calculated total non-starch polysaccharide contents (r = 0.79), the neutral detergent fibre contents (r = 0.76) and the total beta-glucan contents (r = 0.70). Furthermore, a significant interaction was found between diets and the method used to derive lipid digestibility. The differences between apparent and true lipid digestibility ranged from 0.05 percentage points for the wheat diet to 0.20 percentage points for the rye diet. 4. From the results of this trial, it appears that TMEN overestimates the energy value of high fibre diets.     

The effects of age,dietary fat and bile salts,and feeding rate on apparent and true metabolisable energy values in chickens

1. Apparent (AME) and true (TME) metabolisable energy values of four diets, containing 50 or 150 g animal fat or maize oil/kg, were estimated in young and adult chickens. The diets were given with and without a supplement of 5 g bile salts/kg. Three feeding rates, ad libitum, and l/6th or 1/3rd of ad libitum were compared.

2. In younger birds, endogenous energy losses were higher when measured in starved birds than when estimated by regression analysis.

3. In young birds, feeding rate had no effect on AME of diets containing 50 g lipids/kg but it significantly affected TME. These results were reversed in adults. AME and TME values of diets containing 150 g lipids/kg were affected by the feeding rate in both young and adult birds.

4. Bile salts increased metabolisable energy values of diets containing high concentrations of saturated fatty acids and their effect was more pronounced in young birds.     

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.     

Relationship between digesta transit time and apparent metabolisable energy value of wheat in chickens

1.?This study tested the hypotheses that: (a) apparent metabolisable energy (AME) values and whole tract transit time (WTTT) were related, and that (b) the relationship between AME and WTTT differed between male and female Ross broiler chickens.

2.?Enzyme products with xylanase activity were added to a basal diet to provide 4 dietary treatments comprising control (no enzyme), Avizyme 1300 (1 kg/tonne), Kemzyme W1 (1 kg/tonne), and Bio-Feed Wheat CT (200 g/tonne). The basal diet comprised (in g/kg), 800 wheat, 155 casein, 20 dicalcium phosphate, 11 limestone, 7 D,L-methionine, 2 vitamin and mineral premix, 3 sodium chloride and 2 choline chloride (60%).

3.?AME values for diets were determined in a 7-d energy balance study commencing when chickens were 21 d of age. WTTT was the time elapsed (in min), from time of administration by oral gavage of 200 mg ferric oxide in a gelatine capsule, to time of first observation of the distinctive red colouration in droppings.

4.?The mean AME value for the wheat was high (15·7 MJ/kg dry matter) and ranged from 14·4 to 16·3 MJ/kg dry matter for individual birds. Mean WTTT was 206 min and ranged from 105 to 429 min. AME and WTTT were unaffected by enzyme addition to the diet, and the interaction between diet and gender was not significant.

5.?There was a significant but weak positive relationship between AME and whole tract transit time, with AME increasing by 2·2 kJ/min. This relationship was unaffected by gender of the chicken.     

A note on the effect of temperature on true and apparent metabolisable energy values of a layer diet

The effect of ambient temperature on the true (TME) and apparent metabolisable energy (AME) values of a layer diet was examined using White Leghorn cockerels.

The TME value found at the cool temperature (5 to 15 °C) was significantly higher than those found at hot (25 to 35 °G) and control (22 °C) temperatures. AME values were not significantly affected.     

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.     

Modified assay for true and apparent metabolisable energy based on tube feeding

1. To improve the accuracy with which true metabolisable energy (TME) values of feedingstuffs are determined, a modification to the assay based on tube-feeding is proposed. 2. To ensure that the gastrointestinal tracts of the experimental birds are as empty as possible at the start of the assay it is recommended that the normal food is withdrawn 48 h before tube-feeding. 3. In order to partly alleviate the effects of starvation, all birds are given two doses of 25 g glucose (as an aqueous solution) about 40 and 16 h before tube-feeding. Birds, from which endogenous energy losses are to be derived, are fed 50 g glucose rather than given no food. 4. All birds are given 50 ml water by tube about 32 h after feeding to overcome any effects induced by low water intake. 5. A comparison of the two procedures with 8 feedingstuffs showed that the mean coefficient of variation was reduced from 5.5% to 1.5% for TME and from 4.7% to 1.8% for TME.     

Interactions between wheat and other dietary cereals with respect to metabolisable energy and digestible amino acids

Small, varying improvements in apparent ileal amino acid digestibilities were obtained when wheat was combined with certain other cereals in broiler diets. Synergistic interactions, sometimes resulting in large improvements in the apparent metabolisable energy (AME) contents of the diets, were also observed with certain cereal combinations. Combining wheat with maize or oats enhanced the utilisation of dietary energy and amino acids.     

Comparative apparent metabolisable energy values of high, medium and low tannin varieties of sorghum in cockerel, guinea fowl and quail

1. Nitrogen-corrected apparent metabolisable energy values (AMEN) of three varieties of sorghum (white-low tannin, brown-medium tannin and red-high tannin) were measured in three species of poultry (cockerel, guinea fowl and Japanese quail) by a practical diet replacement (total collection) method. 2. Each variety of sorghum was tested at two concentrations (200 and 400 g/kg of reference diet) in 6 replications with one cockerel or guinea fowl or two quails per replication. The duration of the trial included a 10 d preliminary feeding period (on conventional grower diet) followed by a 12 d adaptation period (on reference and test diets) and a 3 d balance period (with recording of feed intake and excreta output). 3. The calculated AMEN values of different sorghum varieties were: white--12.9, 12.8 and 12.7; brown--12.7, 12.3 and 12.6; and red--11.4, 11.1 and 11.6 MJ/kg for cockerels, guinea fowls and quails, respectively. The mean AMEN value of red sorghum (11.3 MJ/kg) was significantly lower than those of brown (12.5 MJ/kg) or white sorghum (12.8 MJ/kg). A negative correlation was observed between tannin concentration and AMEN. 4. There was no significant difference in the AMEN values of white, brown and red sorghum varieties to the different poultry species. AMEN values of sorghum for the cockerel could, therefore, be used in practical feed formulation for guinea fowl and quail.     

Comparison of metabolisable energy values of different foodstuffs determined in ostriches and poultry

Apparent (AMEn) and true (TMEn) metabolisable energy values, corrected for nitrogen retention, of wheat bran, saltbush (Atriplex nummularia), common reed (Phragmites australis), lupins, soyabean oil cake meal (SBOCM), sunflower oil cake meal (SFOCM) and fishmeal were compared in 7 successive trials using 12 mature South African Black ostriches and 10 adult Australorp cockerels per ingredient. TMEn values of 11.91, 7.09, 8.67, 14.61, 13.44, 10.79 and 15.13 MJ/kg for wheat bran, saltbush, common reed, lupins, SBOCM, SFOCM and fishmeal, respectively, were found for ostriches in comparison to lower (P<0.05) values of 8.55, 4.50, 2.79, 9.40, 9.04, 8.89 and 13.95 MJ/kg for cockerels. The higher (P<0.05) ME values for ostriches confirm that the ostrich is capable of digesting foodstuffs, especially those with high fibre concentrations such as drought-resistant fodders, more effectively than poultry. Plant protein sources could make a considerable energy contribution to diets for ostriches. It is concluded that it is essential to use energy values of foodstuffs determined using ostriches and not extrapolated values derived from poultry in diet formulation for ostriches.     

True metabolisable energy, heat increment and net energy values of two high fibre foodstuffs in cockerels

1. The yields of true metabolisable energy (TME) and net energy (NE) from chaya leaf meal and wheatfeed were mcasured in tube-fed cockerels. 2. TME, 5.76 MJ/kg, from chava leaf meal was lower than from wheatfeed, 8.39 MJ/kg. The total heat increment attributable to the feeding of chaya leaf meal was 1-7 times greater than that of wheatfeed. 3. The net efficiency of utilisation of ME (k) from chaya leaf meal was 0.64, while that from wheatfeed was 0.86. The role of different chemical composition, especially the high fibre content of the materials, is discussed. 4. The metabolisable energy and net energy values derived from chava leaf meal represented 0.34 and 0.23 respectively of its gross energy content. The combination of lower TME and lower net efficiency of utilisation led to chaya having a NE value, 3.86 MJ/kg, which was only 0.53 that of wheatfeed.     

A comparative study between mature ostriches (Struthio camelus) and adult cockerels with respect to true and apparent metabolisable energy values for maize,barley, oats and triticale

1. In three successive trials with cockerels and mature ostrich males the apparent and true metabolisable energy values, corrected for nitrogen retention (AME_n and TME_n) were determined by a balance method for malting barley, oats, triticale and yellow maize. All these ingredients were used as sole dietary components with the exception of triticale for ostriches which was diluted with 440 g/kg lucerne meal. The balance trial lasted for 5 d after an adaption period of 7 d for ostriches, and 3 d after an adaption period of one day for cockerels.

2. AME_n values for cockerels of malting barley, oats, triticale and maize were 11.6, 10.48, 11.44 and 14.42 MJ/kg respectively. Significantly higher values of 14.21, 12.65, 12.60 and 14.89 MJ/kg were determined for malting barley, oats, triticale and maize for ostriches.

3. TME_n values determined by regression yielded values in ostriches of 13.92, 12.27, 13.21 and 15.22 MJ/kg for malting barley, oats, triticale and maize respectively. The corresponding TME_n values in cockerels were 11.33, 10.63, 11.82 and 14.07 MJ/kg.

4. The ostrich is capable of utilising fibre more efficiently than poultry. The higher energy values observed for the various ingredients also indicated that the non‐starch polysaccharides such as ß‐glucans and arabinoxylans in the more fibrous energy sources had little if any effect on the available energy of these ingredients as found with poultry.

5. The potential of ostriches to utilise the more fibrous energy sources like barley, oats and triticale allows for their economical use in diet formulation. This possibility may result in markedly lower food costs for ostriches.     

Cell wall content as a predictor of metabolisable energy value of poultry feedingstuffs

1. Forty eight diets were tested to develop equations for predicting the apparent metabolisable energy values corrected to zero nitrogen retention (AMEn), of practical poultry feedingstuffs.

2. The effectiveness of different fibre indicators (crude fibre, acid detergent fibre, lignin, neutral detergent fibre and cell wall content) as predictors of AMEn values was assessed. The most efficient measure proved to be cell wall content obtained by an enzymatic procedure (pronase and α‐amylase).

3. The best combinations of variables were, in decreasing order: (1) gross energy (GE), crude protein (CP) and cell wall (CW); (2) ether extract (EE), ash and CW; (3) EE, CP, starch and sugars.

4. When GE, CP and CW variables were used, a significant constant appeared in the linear equation. Another equation without a constant was calculated, using an exponent (1·5) for the CW variable. The residual standard deviation (0·20 MJ/kg) of this equation was about the same as that of the equation with the constant.

     

Effects of sex,age and food intake upon metabolisable energy values in broiler chickens

1. Nitrogen‐corrected apparent metabolisable energy (AME_n) values of 2 diets with different energy: protein ratio were estimated in an experiment with 8 groups of female and 8 of male chickens in 15 sequential 3‐day balance periods from the 12th to the 56th d of age.

2. The effect of sex on AME_n values was not significant.

3. The effect of age was highly significant. AME_n values of the mixture with the narrower energy: protein ratio increased with age. The dependence of AME_n of the diet with the wider energy: protein ratio on age was parabolic, AME_n values increasing only until the 37th day of life.

4. Under conditions of ad libitum feeding, AME_n of the mixture with the wider energy: protein ratio given to female chickens decreased significantly with increasing food intake.