Feeding behaviour in chickens given diets containing medium chain triglyceride

1. The effect of dietary medium chain triglyceride (MCT) on short‐term food intake was compared with the effect of long chain triglyceride (LCT) in chickens. Maize oil was used as the LCT while glyceryl tricaprylate (C 8) and glyceryl tricaprate (C 10) were used as MCT. Cumulative food intake was determined during the 6 h after the start of feeding.

2. Chicks were given diets containing 200 g C 8/kg diet, 200 g C 10/kg diet or 200 g LCT/kg diet in experiment 1. As early as 30 min after feeding, cumulative food intake in both MCT‐supplemented diets decreased significantly compared with the diet containing LCT.

3. To determine if endogenous cholecystokinin (CCK) was responsible for the decrease in food intake caused by MCT, birds were injected with the CCK‐A receptor antagonist devazepide (DVZ, 1 mg/kg BW) before diet presentation. DVZ had no effect on food intake with either LCT‐ or MCT‐supplemented diets.

4. In experiment 3, chicks were given a choice between either diets containing LCT and C 8, LCT and C 10, or C 8 and C 10 to confirm whether or not the palatability of the diets was influenced by the dietary fat sources. There was no difference in food intake between C 8 and C 10‐supplemented diets. However, chicks preferred the LCT‐supplemented diet compared with either of the diets containing MCT.     

Effect of dietary medium chain triglyceride on protein and energy utilisation in growing chicks.

1. Protein, fat and energy retentions of chicks fed on diets containing medium chain triglyceride (MCT) and long chain triglyceride (LCT), at 100 and 200 g fat/kg diet, were investigated. Maize oil was used as the LCT source. The MCT used was glyceryl tricaprylate. 2. Body weight gain and food intake were decreased with the diets containing MCT and these effects were greater at the higher fat concentration. Protein retention was also reduced by dietary MCT, although the efficiency of protein utilisation (protein retained/protein intake) was not altered. 3. The values for fat and energy retentions were significantly lower in the chicks fed on the MCT-supplemented diets than in those receiving the LCT-containing diets. Dietary ME values and efficiencies for energy utilisation (energy retained/ME intake) were also reduced by dietary MCT.     

A comparison of the energy and nitrogen metabolism of fed ducklings and chickens

1. Energy measurements were made over 4 d on groups of three ducklings (aged from 5 to 22 d), and three broiler chickens (aged from 11 to 32 d) offered high‐ or low‐energy diets.

2. Food, metabolisable energy (ME) and water intakes were significantly higher for ducklings than for chickens. The ratio of water : food was 4.2 : 1 and 2.3 : 1 for ducklings and chickens, respectively. The food conversion ratio differed between diets but not species. Performance was generally better for both species on the high‐energy diet.

3. Heat production, energy, fat and protein retentions were higher for ducklings than chickens, and ducklings retained 0.44 of their energy as fat compared with 0.37 for chickens. Overall the ratio of protein (g) to fat (g) retention was 2.2 : 1 and 2.8 : 1 for ducklings and chickens respectively.

4. For ducklings, metabolisability of the high‐energy diet declined from 0.774 to 0.747, and to a lesser extent of the low‐energy diet, as they aged. There was no such decline for chickens. Net efficiency of utilisation of ME for gain was 0.64 for ducklings compared with 0.50 for chickens.

5. Fractional retention of dietary nitrogen (N) was 0.62 for ducklings and 0.55 for chickens. Gaseous ammonia‐N was 4.5 and 2.2%, respectively, of N retained.

6. In a second experiment groups of ducklings only, were offered high‐and low‐protein diets from 12 to 22 d of age. Comparisons among four diets showed that food and energy intake was lower on the low‐protein diet than on the other three. Energy retention on the high‐energy diet was greater (P<0.05) than on the other three diets.

7. It was concluded that a high‐energy diet is important for ducklings and chickens for maximum biological performance during the first 4 weeks of life.     

Fat deposition and heat production as responses to surplus dietary energy in fowls given a wide range of metabolisable energy: Protein ratios

1. Female broiler fowl between 21 and 42 d of age were given diets with apparent metabolisable energy (AME) contents ranging from 8 to 15 MJ/kg at each of two crude protein (nitrogen x 6.25; CP) contents (130 and 210 g/kg).

2. Food intake was measured daily for 21 d. Body composition was determined at 42 d and gains in body mass, protein, fat and gross energy calculated by comparison with a group analysed at 21 d. Heat production was calculated by difference between AME intake and energy gain.

3. Decrease of food mass intake with increased dietary AME concentration limited the increase in AME intake to about 25%, despite the near 2‐fold range of AME concentrations.

4. There was no effect of CP concentration on food mass intake. CP intake was directly related to CP: AME ratio.

5. When body weight differences were taken into account, heat production was independent of dietary AME concentration, but increased by about 8% on the higher‐protein diets.

6. There were strong linear correlations between dietary CP:AME ratio and carcase protein: energy ratio, carcase fat content and carcase protein content.

7. It was concluded that the growing fowl responded to dietary nutrient: energy ratio, and the associated differences in nutrient and energy intakes, by varying the rate of energy deposition as fat, without regulatory variation of energy dissipation as heat.     

Effects of dietary cholestyramine on the utilisation of diets containing medium or long chain triacylglycerols by chicks

1. The effects of graded dietary concentrations of cholestyramine (CSTY, a bile acid binding polymer), which prevents micelle formation and bile acid reabsorption, on the lipid and energy metabolism of chicks given diets containing different dietary concentrations of medium chain triacylglycerol (MCT) and long chain triacylglycerol (LCT) were investigated.

2. MCT‐ or LCT‐supplemented diets containing 100 or 200 g oil/kg diet and 0, 10 or 20 g CSTY kg were fed to 7 d old chicks for 10 d. As dietary CSTY concentration increased, a reduction in the metabolisable energy value was observed for both dietary lipid sources. Consequently, fat and energy retentions were also reduced as the dietary CSTY content increased.     

Effect of dietary energy restriction on retention of protein,fat and energy in broiler chickens

1. Broiler chickens were fed 60–100% of recommended energy intakes to study the effects of energy restriction on protein and fat retention.

2. At an energy retention of 179 kJ/kg W ^0·75 d, only protein was retained. At higher energy intakes, each increment in retention had a rather constant composition: about 85% energy in fat and 15% in protein. At lower energy intakes body fat was mobilised whereas protein was deposited.

3. The efficiencies of energy retention in protein and fat were estimated to be 0·66 and 0·86 respectively.

4. The rather constant composition of additional retained energy after additional energy supply provides an explanation for a linear relationship between energy intake and energy retention.     

The response of male broiler chickens to diets with various protein and energy contents during the growing phase

1. In two trials each using 2 400 male broilers, the regression of body weight on the linear effects of dietary protein, energy and age, the quadratic effect of age, and their interactions, accounted for approximately 99% of the observed variation during the growing and finishing period (3 to 8 weeks of age). Increasing either dietary protein or energy content significantly increased body weight.

2. The regression of food consumption on the linear effects of age, protein, energy and protein × energy interaction, and the quadratic effect of age accounted for 94% of the observed variation. The regression of food utilisation on the linear effects of protein, energy, and age and the quadratic effects of dietary protein and age accounted for 97% of the observed variation. Food consumption and efficiency were dependent on both dietary protein and energy, increasing with increases in either dietary protein or energy content.

3. The regression of fat in the dressed carcass on the linear effects of protein, energy and age accounted for 19% of the observed variation. Carcass fat increased with increasing age and dietary energy, and decreased with increasing dietary protein.

4. Although body weight, food consumption and utilisation were significantly different between trials, the proportion of carcass fat was not.     

Calorimetric measurements of the energy and nitrogen metabolism of Japanese quail

1. Respiration calorimetry measurements were made over 4 d on normally‐fed groups of 10 male or 10 female quail during three periods commencing at 12, 19 and 26 d of age. Carcass compositions were determined on groups of birds of each sex at 2 and 5 weeks of age.

2. Expressed per unit body weight, food and metabolisable energy (ME) intake and weight gain decreased between 2 and 3 weeks of age, but remained constant thereafter.

3. No differences were observed between sexes for any variable measured. Efficiency of utilisation of ME for energy retention was only 0.33. This was mainly because the majority of energy was retained as protein tissue.

4. Nitrogen (N) retention (g/d) increased with increasing dietary N intake but when expressed as a proportion of N intake, declined from 0.46 at 2 weeks to 0.33 at 4 weeks. Fat retention increased substantially during week 4.

5. Carcass analyses showed that fat, protein and ash were higher for quail at 5 weeks than at 2 weeks of age. At 5 weeks carcass fat was only 60 g/kg.     

Effect of dietary protein,essential and non‐essential amino acids on the performance and carcase composition of male broiler chickens

1. The present study was conducted to determine the possibility of using low‐protein broiler diets supplemented with synthetic amino acids. The effects on performance, carcase composition and nitrogen retention were evaluated.)

2. A starter diet was given, ad libitum, from 7 to 21 and a finisher diet from 21 to 42 d of age. Body weight, weight gain, food intake and food conversion (FC) were determined at 3 and 6 weeks of age. Abdominal fat deposition (AFD), carcase yield, carcase fat and protein and nitrogen retention were determined at 6 weeks of age. During the starter period chicks were given a 231 g/kg crude protein (CP) diet and a low protein diet supplemented with synthetic amino acid, a: to National Research Council recommendations, b: to the concentration of the control diet, and c: in agreement with the pattern of body composition. Glutamic acid and glycine were added to some diets as sources of non‐essential amino acids (NEAA). All diets contained 12.62 MJ metabolisable energy (AME_n)/kg. The diets administered between 3 and 6 weeks were comparable to the starter diets, except that they contained more AME_n (12.85 MJ/kg) and less protein.

3. Performance equal to that of high protein controls was obtained with birds fed a low protein diet supplemented with synthetic essential and NEAA to the amounts in the control diet or based on the amino acid profile of body protein. This was not achieved with low protein diets supplemented with synthetic amino acids to the amounts recommended by NRC.

4. Without altering performances, the efficiency of protein utilisation of birds fed on low protein diets was superior to that of birds fed on the commercial control diet and their nitrogen excretion was reduced by 26%. The percentage carcase yield and protein was unaffected by the dietary regimen but carcase fat content and AFD increased as the protein content of the diet decreased.

5. These results show that it is possible to obtain the same performances with low protein diets supplemented with synthetic amino acids, using an ideal amino acid balance. However, low protein diets result in a higher carcase fat content.     

Supplementation of groundnut‐based broiler chick diets with pyridoxine

1. Broiler chicks fed on a semi‐purified diet containing 230 g crude protein and less than 5 mg pyridoxine/kg had poor growth rates and high mortality.

2. When a milled, unsupplemented diet based on rice and groundnut was fed, food utilisation, carcass fat content and serum aspartate amino transferase [EG 2.6.1.1] activity indicated the need for supplementation with at least 3 mg pyridoxine, or a total concentration of 8.8 mg/kg diet.

3. With a maize‐groundnut diet body‐weight gain, food intake and tissue aspartate aminotransferase activities suggested that dietary supplementation with pyridoxine was unnecessary, but food utilisation indicated a need for supplementation with 3 mg or a total intake of 9 mg pyridoxine/ kg diet.

4. A practical broiler chick starter diet was used to show that the total concentration of pyridoxine should be at least 7.2 mg/kg when maize‐groundnut diets are fed.     

Effects of dietary energy concentration on utilisation of energy by broiler chickens and on body composition determined by carcass analysis and predicted using tritium

Groups of 10 male, 10 female and 10 unsexed broiler chickens were given eight diets with energy concentrations ranging from 2.3 to 3.6 Mcal ME/kg in two experiments. Diets with a metabolisable energy concentration of about 3.1 Mcal/kg were found to be optimal for growth to a specified live‐weight. Carcass analysis gave much smaller values for nitrogen retention than did estimates from food intake and excreta. Retention measured by the latter method was influenced by the energy concentration of the diets.

Body composition was influenced by both dietary energy concentration and sex. In general, the energy and fat content of the carcass increased with increasing dietary energy concentration although there were overall differences in fat content between male and female chickens, and also between birds in experiment 1 and experiment 2.

Tritiated water was used to predict body water space enabling body composition to be estimated. Comparisons between determined body water content and tritiated water space showed that the former was overestimated, on average, by 18%. Residual standard deviation of prediction equations based on 240 chickens was 52.6 g for water space, 21.4 g for protein and 34.6 g for fat.     

Synthetic oestrogens in the production of roasting fowl. II. Dietary nutrient concentration and time of implantation

Three experiments have been carried out using broiler‐type birds reared beyond the normal broiler stage to 14 weeks of age. In the first experiment control cockerels were compared with birds injected with either a 15 mg. hexoestrol pellet or a 15 mg. pellet of diethylstilboestrol at 9 weeks of age: at this stage three diets of different nutrient density were offered. As the nutrient density was increased, food utilisation progressively improved and growth rates were raised. Hexoestrol implantation resulted in an increase in voluntary food intake of 23 per cent above the control whereas diethylstilboestrol implantation increased voluntary food intake by only 14 per cent. These increases in food intake were associated with proportional increases in live‐weight gain.

In a second experiment pullets received 15 mg. implants of hexoestrol at 64 days of age, and were then fed diets of different nutrient concentrations to 98 days of age. Live‐weight gain tended to improve as nutrient density was raised, and efficiency of food utilisation was inversely proportional to nutrient density.

In a third experiment male birds were reared from 70 to 119 days of age. Four different implantations with hexoestrol at various ages were compared: only in those receiving two implants was there any difference in performance. Six diets varying in energy level and protein level were offered. Growth rates improved as dietary protein levels were raised progressively from 13.3 to 16.3 per cent, though food utilisation was most efficient at 14.8 and 16.3 per cent crude protein. Growth rate was 7.6 per cent greater when the dietary energy level was raised from 3065 to 3275 kcal. metabolisable energy per kg.     

Influence of activity and dietary energy on broiler performance,carcase yield and sensory quality

1. A total of 2560 male and female Ross broilers were raised to 42 days of age in a 2 × 2 treatment factorial arrangement experiment to investigate the influence of different degrees of physical activity and dietary energy on broiler performance, abdominal fat content, carcase yield and sensory quality.

2. Vertical fans were used to force the treatment birds to walk 3 to 4 times as far as the normal activity birds; birds were fed a normal and a high energy diet (12.55 compared with 13.81 MJ ME/kg) with the same energy/protein, energy/lysine and energy/methionine + cystine ratios.

3. High activity birds had greater body weight ( + 4.1%), food intake ( + 5.1%) and ME intake ( + 5.1%) than normal activity birds. Birds receiving high energy diet had a lower food conversion and food intake than birds receiving normal energy diet. There were no significant differences in body weight or ME intake between birds with different diets.

4. Slaughter yields, both absolute and relative to live body weight, were affected by activity or dietary energy to varying degrees. Breast meat was increased with more activity. The absolute weight of abdominal fat was independent of activity and in males the relative weight of abdominal fat was decreased in high activity birds.

5. Different degrees of activity and dietary energy had only minor influences on broilers' sensory quality.     

Effects of dietary protein content,addition of nonessential amino acids and dietary methionine to cysteine balance on responses to dietary sulphur‐containing amino acids in broilers

1. Two experiments were conducted with male broiler chicks from 2 to 5 weeks of age to determine the effect of dietary protein content and amino acid balance on the response to dietary sulphur‐containing amino acids (SAA) in terms of performance and carcase quality.

2. In experiment 1, 5 graded amounts of a DL‐methionine and L‐cysteine (1:1 by weight) mixture were added to basal diets containing 197 or 233 g crude protein/kg. The diets containing 197 g protein/kg were fed with or without the further addition of 36 g crude protein/kg from nonessential amino acids. The amino acid balance of all diets was kept constant for all essential amino acids except the SAA. In experiment 2, 5 graded amounts of SAA from either a crystalline source (DL‐methionine or a mixture of DL‐methionine and L‐cysteine) or from intact proteins were added to a diet containing 208 g protein/kg.

3. At each protein concentration there were significant responses to the SAA addition in weight gain, food conversion efficiency, and carcase quality. Non‐linear exponential regression analyses were used to describe bird responses to SAA concentration. The broiler chick's requirement for SAA increased with increasing dietary protein concentrations ranging from 197 to 259 g protein/kg.

4. The utilisation of SAA differed also with differences in origin (crystalline or peptide‐bound), and methionine:cysteine balances. Compared to DL‐methionine, a 1:1 mixture of DL‐methionine and L‐cysteine was only 81% or 86% as effective in supporting growth or food conversion, respectively. SAA from added protein was even less effectively utilised.

5. The addition of nonessential amino acids tended to decrease food intake without affecting SAA utilisation.

6. Slaughter yield and breast meat yield were clearly increased while fat deposition was clearly decreased, by SAA addition. The response in breast meat yield suggested an important economic benefit for further meat processing. Nitrogen retention was significantly enhanced by SAA supplementation from crystalline sources, and this led to reductions of up to 30% in the amount of nitrogen excreted per kg weight gain.     

Effect of dietary energy concentration on the response of laying hens to amino acids

1. A hypothesis, that the optimum amino acid concentration in the diet is not directly proportional to the dietary energy concentration, but changes in inverse proportion to the change in food intake resulting from a change in energy concentration, was tested in three experiments.

2. Response experiments involving the amino acids methionine, lysine and isoleucine were conducted, in each case at three dietary energy concentrations, using a diet dilution and blending technique, thereby ensuring a constant ratio between background amino acids and the first‐limiting amino acid in all diets, and also keeping the ratio of amino acids to energy constant as energy varied.

3. A common response curve relating egg output (g/bird d) to amino acid intake (mg/bird d) for each amino acid, fitted by means of the Reading Model, adequately described the response at each of the dietary energy contents. This implies that energy does not influence egg output directly, but only indirectly through its effect on food intake and hence on amino acid intake.

4. Both amino acid and energy concentration significantly influenced food intake. Energy intake was not constant over all dietary energy concentrations, being lower at low energy levels and higher at high energy concentrations.

5. It is concluded that amino acid requirements should not be stated either as percentages or as ratios with energy. Optimum amino acid intakes and energy concentrations should be calculated; the expected food intake should then be predicted, after which the appropriate concentration of nutrients in the diet can be determined.     

Effect of low-energy cereals and cereal by-products and of a vegetable fat supplement on egg production and food conversion in caged layers

The aim of this work was to ascertain the value of alterations in the energy concentration in layers' diets by the incorporation of high‐energy cereals and fat in diets composed of ingredients commonly used in the United Kingdom. Two similar experiments, employing 22 individually‐fed Light Sussex pullets on each diet, were carried out using cereal and cereal by‐products in four diets containing 1200, 1050, 1000 and 880 k cal. M.E./lb. Significant improvements in food conversion efficiency were found when low energy cereals were replaced by maize. Furthermore, the diet of lowest energy content led to a considerable reduction in the total energy intake of the pullets accompanied by a fall in production. There is evidence that the efficiency of utilisation of M.E. for egg production is not affected by the dietary level of M.E. over the range of energy concentration studied in these experiments.

In two further experiments four groups of 48 Brown Leghorn x Light Sussex pullets were fed diets containing three levels of vegetable fat as groundnut oil to give dietary concentrations of 1170, 1240, 1270 and 1340 k cal. M.E./lb.

The results show that fat addition had no significant effect on egg production or egg size.     

An experimental study of the utilisation, by the laying hen, of dietary energy partially supplied as animal fat

Experiments were carried out at two centres in which laying hens were fed diets containing up to 28.25 per cent tallow and in which an attempt was made to maintain a fairly constant calorie : protein ratio. The most satisfactory production was obtained on a diet containing 3.5 per cent added fat in one experiment and 7.5 per cent added fat in the other experiment. Food conversion efficiency (kg food/kg eggs) increased with increasing dietary fat content.

The efficiency of ME utilisation (Mcal/kg egg) decreased with increasing dietary ME content. The data indicate that at the higher levels of fat addition the net utilisation of ME was decreased.

In both experiments mean egg weight was increased by the addition of tallow to the diet whilst at the highest level of addition there was a very high mortality.     

Effect of growth promoters on monensin toxicity in broiler chicks 1

1. An experiment was carried out with male broiler chicks to evaluate the combined effect of monensin (150 mg/kg) and the growth promoters (GPs) Zn bacitracin (BAC, 50 mg/kg), virginiamycim (VIR, 25 mg/kg) and avoparcin (AVO, 20 mg/kg) fed from 7 to 28 d of age on performance, utilisation of dietary nutrients, yield of defeathered eviscerated carcases (DEC) and size of various organs. The effect of the GPs in the monensin‐unsupplemented diets fed up to 49 d of age on performance and carcase was also determined.

2. Monensin significantly (P < 0.05) depressed food intake, weight gain and food efficiency from 7 to 28 d of age. None of the GPs was able to counteract these effects. However, AVO slightly ameliorated them. AVO also significantly increased food intake and improved gain and food efficiency during 7 to 28, but not 28 to 49 or 7 to 49 d of age. VIR and BAC did not affect performance in either age period.

3. Monensin did not affect the utilisation of dietary dry matter, fat or energy, but it significantly decreased nitrogen utilisation. AVO improved nitrogen and fat utilisation and increased dietary AME_n content. AME_n was also increased by VIR. The utilisation of these nutrients was not affected by the interactions between monensin and the GPs.

4. Monensin did not affect yield of the DEC or the relative liver size at 31 d of age. It significantly increased the relative length of the small intestine (SI) and decreased its specific weight. AVO significantly increased yield at 31, but not at 53 d of age. BAC and VIR did not affect this variable. AVO and VIR, but not BAC, at both age periods reduced, at times significantly, the size, length and specific weight of the SI.

5. Our conclusions: BAC, VIR and AVO do not counteract the toxic effect of monensin. The effect of GPs in improving performance decreases and even disappears with age, while their effect in reducing the size of the SI is still evident in 49‐d‐old birds.     

The replacement of some of the soybean meal by the first‐limiting amino acids in practical broiler diets

1. Four trials were carried out with broilers from 5 to 9 weeks of age in order to determine the effect of reducing dietary protein concentration, with and without special supplementations of methionine and lysine, on the amount of carcass fat.

2. In all trials fat deposition increased progressively as the protein concentrations of well‐balanced standard finisher diets were lowered by replacing soybean meal with sorghum grains (milo).

3. The increased degree of fatness was the result of graded increases in food consumption, and consequent decreases in food utilisation, caused by inadequate dietary protein.

4. In three out of four trials the above negative trends could be partly or completely reversed by special supplementations with methionine and lysine in amounts to restore the dietary concentration of these first‐limiting amino acids to those of the control diets.

5. It appears that broilers overeat in a compensatory attempt to obtain the limiting amino acids required for optimal growth rate, as long as the deficiency is not severe enough to cause an amino acid imbalance.     

Replacing maize with sweet potato in diets for chicks

1. Rhode Island Red chicks and chicks of the indigenous fowl of Nigeria were fed for ten weeks on diets of 227.5 g protein and 11.92 to 13.72 MJ ME/kg in which sweet potato was substituted for maize.

2. Replacing up to 344.3 g maize/kg with sweet potato did not significantly affect body weight, food intake, food conversion, nitrogen retention, mortality and relative weights of body parts at 10 weeks of age.

3. Whereas crude protein contents of liver, gizzard, heart, lung and breast were not significantly affected by the diets, fat contents were significantly decreased by the replacement of 344–3 g maize/kg with sweet potato.