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 metabolic use of energy from dietary fat in broilers is affected by fatty acid saturation

1. Two experiments were performed to evaluate the effect of dietary fat on performance and fat and protein accretion in broiler chickens according to the degree of saturation. 2. The first experiment was designed to test 2 sources of dietary fat and 3 levels of dietary energy using a factorial (2x3) experimental design. The foods were formulated to maintain a constant ratio of energy to protein (and other nutrients). There were no significant differences in weight gain, intake, final body weight or food to gain ratio between broilers fed on diets differing solely in the degree of fat saturation. Broilers fed on diets containing animal fat showed higher whole-body fat retention (P=0.02) and lower protein accretion (P=0.03) than those fed on diets containing vegetable oils. 3. In the second experiment, only 1 concentration of fat (tallow, lard or sunflower oil) was incorporated into the experimental diets, providing different energy to protein ratios. The carcase protein content was not affected by dietary fat source, while total fat accretion (P=0.01) and energy retention (P=0.14) were highest in broilers fed on a diet containing tallow. 4. The findings suggest that the degree of saturation of dietary fats affects their metabolic use and fat accumulation in broiler chickens.     

Effects of energy concentration and duration of feeding on the response of broiler chicks to growth promoters 1

1. Two experiments were carried out with male broiler chicks from 7 to 49 d of age to evaluate the combined effect of the growth promoters (GPs) avoparcin (AVO, 20 mg/kg), Zn bacitracin (BAC, 25 mg/kg) and nitrovin (NIT, 18 mg/kg), and dietary energy concentration (EC) (experiment 1) and the effect of age of feeding AVO (experiment 2) on performance, utilisation of dietary nutrients, yield of defeathered eviscerated carcases (DEC) and size of various organs.

2. AVO, in contrast to BAC and NIT, significantly (P<0–05) decreased fat excretion and increased dry matter, fat and nitrogen retention, dietary AME_n content, weight gain and food efficiency. AVO also significantly decreased the size of the liver and the small intestine (SI), the length of the SI and its specific weight. The effect of BAC and NIT on the variables of the SI was less pronounced than that of AVO. Although the effect of AVO on increasing fat retention, growth and food efficiency was more pronounced with the high EC diet, neither of the variables of performance, nutrient utilisation (except for fat retention) or organ size, was significantly affected by the interactions between GPs and dietary EC.

3. AVO fed continuously or from 28 d of age significantly improved food efficiency during 7 to 49 d of age, increased the yield of DEC and decreased the size of the liver and the SI, the length of the SI, and its specific weight. None of these effects was observed when AVO was omitted from the diet at 28 d of age. Feeding AVO from 28 d of age did not improve weight gain during the entire period, as did the continuous feeding of this GP.

4. It is concluded that BAC and NIT are not effective as GPs under the conditions of the present study. The effect of AVO on improving performance and on carcase characteristics is hardly dependent on dietary EC. Feeding AVO from 28 to 49 d of age improves food efficiency and has similar effects on carcase characteristics to those of continuous feeding.     

Involvement of food intake in the decreased energy retention associated with single deficiencies of lysine and sulphur-containing amino acids in growing chicks.

1. Growth and energy utilisation were determined in growing chicks fed ad libitum on diets deficient either in lysine (5.95 g/kg) or in sulphur-containing amino acids (SAA, 3.5 g/kg). Food intake, body weight gain, energy retained as protein and as fat, and total energy retention were significantly (P less than 0.05) reduced by single deficiencies of either lysine or SAA. 2. Another two experiments were conducted to determine if the decreased total energy retentions in chicks fed on diets deficient in lysine (experiment 3) or SAA (experiment 4) were associated with reduced food intake, by using tube-feeding to control the amount and pattern of food consumption. Chicks fed on diets deficient in lysine or SAA retained less energy as protein and more energy as fat than the control chicks. Neither total energy retention nor heat increment was affected by these deficiencies. Total energy retention was proportional to metabolisable energy (ME) intake alone. 3. It is concluded that the decreased total energy retentions caused by single deficiencies of lysine and SAA were associated with decreased food intake.     

Improvement of dietary protein utilisation in chicks by medium chain triglyceride

1. To improve the influence of variation of ME intake, an experiment was carried out using equalised feeding to investigate the comparative effects on protein and energy utilisation in chicks of diets containing medium chain triglyceride (MCT) and long chain triglyceride (LCT). Experimental diets were given at 3 different food intakes, namely, 100, 120 or 147 g/bird/10 d. The diets contained MCT or LCT on an isoenergetic basis. Maize oil and caprylic acid triglyceride respectively, were used as LCT and MCT sources.

2. Body weight gain and food efficiency of chicks significantly increased with the supplement of dietary MCT compared with dietary LCT at all food intakes. Protein retention and the efficiency of protein utilisation (protein retained/protein intake) at all food intakes also significantly increased with dietary MCT, while body fat and fat retention were significantly reduced. Chicks fed the LCT‐supple‐mented diet, on the other hand, had a lower protein retention, but significantly higher fat retention. The value for energy retention and the efficiency of energy utilisation (energy retained/ME intake) were not significantly different between MCT‐ and LCT‐supplemented diets.

3. It was concluded that supplementing MCT to the chick diet would improve body weight gain and protein utilisation while regulating fat deposition compared to the LCT supplemented diet, under equalised feeding conditions.     

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.     

Energy utilisation in germ-free and conventional chicks fed diets containing sorbose

1. In experiment 1, growing conventional (CV) chicks were fed on diets containing graded amounts (0, 100, 200 and 300 g/kg diet) of sorbose from 4 to 14 d. Protein, fat and energy deposition were determined after carcase analysis. The values for growth, food efficiency, metabolisable energy (ME) and fat and energy depositions declined as the dietary sorbose content increased. 2. In experiment 2, the performances of germ-free (GF) and CV chicks fed on diets with (100 g sorbose/kg diet) or without sorbose were investigated. On both diets, body weight gain, food consumption and protein accumulation in GF chicks were significantly higher than those in CV birds. No significant differences were observed between the dietary treatment except for ME values, which were significantly lower for the sorbose diet. 3. It is suggested that dietary sorbose decreased energy utilisation, and that the microbial contribution to the utilisation of dietary sorbose was negligible in the chicken.     

Lack of interrelationship between the effects of dietary factors and food withdrawal on carcase quality of broiler chickens

1. Four factorial experiments were carried out to determine whether there is any interrelationship between dietary energy-to-protein (E:P) ratio (experiments 1, 2 and 3) or pelleting the diet (experiment 4) and the duration of food withdrawal (FW), in their effect on carcase quality of broiler male chickens. The quality was evaluated by yields of carcase and breast meat, abdominal fat pad size, and the content and composition of the fat in the meat. The effect of sex on the response to FW was also determined in experiment 3 and that of age in experiment 4. 2. The diet with an E:P ratio higher than recommended decreased the weights of carcase and breast meat significantly (P 0.05) in 2 of the 3 experiments, and consistently increased the size of the abdominal fat pad and the fat content in thigh, but not in breast meat. Abdominal fat pad and the fat in meat of birds fed on this diet contained a significantly higher amount of oleic acid and a lower amount of linoleic acid, than the fat of birds fed on the diets with the recommended and the low E:P ratios. The pellets increased significantly the weights of carcase and breast meat and the relative size of abdominal fat pad. 3. FW for 24 h decreased significantly the weight at slaughter in all 4 experiments, carcase weight in 3 experiments, and breast weight in 1 experiment. However, it did not affect the relative size of the abdominal fat pad, the fat content in thigh and breast meat, and the composition of fatty acids in these tissues and in abdominal fat. None of the variables mentioned was affected significantly by the interaction between the dietary factors evaluated, sex or age of the birds on the one hand, and FW on the other hand. 4. It is concluded that the effect of 24 h of FW on weight at slaughter, carcase and breast meat weights and on fattening, is not affected by dietary E:P ratio, pelleting the diet, or sex and age of the broilers.     

饲粮蛋白质和脂肪来源对育成前期蓝狐营养物质消化率和氮代谢的影响

本试验旨在研究饲粮蛋白质和脂肪来源对育成前期蓝狐营养物质消化率和氮代谢的影响。试验采用双因子试验设计,设植物性蛋白质(P植)和动物性蛋白质(P动)2个蛋白质来源,豆油(F植)和猪油(F动)2个脂肪来源,配制4种试验饲粮(P植F植、P植F动、P动F植、P动F动)。选取(55±5)日龄、体重相近的健康蓝狐80只,随机分成4组(每组20只,公母各占1/2),每组随机饲喂1种试验饲粮。预试期14 d,正试期60 d。结果表明:P植组蓝狐的干物质、粗蛋白质和总能消化率显著或极显著高于P动组(P<0.05或P<0.01),但蛋白质生物学价值却极显著低于P动组(P<0.01);F动组蓝狐的粗脂肪消化率极显著低于F植组(P<0.01),但氮摄入量、氮沉积、净蛋白质利用率和蛋白质生物学效价则显著或极显著高于F植组(P<0.05或P<0.01)。由此得出,蓝狐对植物性蛋白质饲料中各营养物质的消化率较高,但蛋白质生物学价值却极显著低于动物性蛋白质饲料,所以蓝狐实际生产中要想以植物性蛋白质饲料为主则要考虑氨基酸平衡问题;豆油的脂肪消化率虽较高,但猪油可以提高氮的利用和沉积,所以动、植物混合油脂的生产效果会更好。     

Effect of dietary phosphorus concentration and electrolyte balance on the growth performance of broiler chickens

The performance of 1680 male and female broiler chickens given diets with either a low (4.7-4.3 g/kg) or high (8.9-8.2 g/kg) content of inorganic phosphorus and four (150, 200, 250 and 300 mEq/kg) electrolyte balances (Na+K-Cl) was measured from 1-d-old to 49 d of age. Diets with the higher concentration of inorganic phosphorus reduced body weight gains in the starter (P less than 0.01) and finisher (P less than 0.05) phases but the efficiency of food utilisation was reduced only in the starter phase (P less than 0.05). The reduction in body weight gain was greater in males than in females. The growth depression caused by the higher concentration of inorganic phosphorus in the finisher diets was partially alleviated by increasing the electrolyte balance to either 250 or 300 mEq/kg diet. The higher concentration of inorganic phosphorus significantly reduced the dressing percentage and increased the abdominal fat pad weight and litter moisture content. Electrolyte balance had no significant effects on efficiency of food utilisation, abdominal fat pad weights or litter moisture content. Neither the dietary concentration of phosphorus nor the electrolyte balance had a significant effect on mortality or ash content of the tibia.     

Influence of protein intake, energy intake and stage of gestation on growth, reproductive performance, nitrogen balance and carcass composition in gestating gilts

Thirty-six crossbred gilts were fed three levels of protein (146, 255 and 364 g/d) and two levels of energy (6,200 and 7,440 kcal of digestible energy/d) throughout gestation in a 3 x 2 factorial arrangement of treatments. Five-day N balance studies were conducted in early (0 to 30 d), mid- (30 to 60 d) and late (60 to 90 d) gestation. At slaughter (90 d of gestation), reproductive tracts were weighed and evaluated for reproductive performance and samples of the reproductive tract, liver and semimembranosus muscle (SM) were analyzed for crude protein. The right half of the carcass was subjected to a physical separation of fat, lean and bone. Neither dietary protein nor energy level significantly affected weight gain or reproductive performance. Nitrogen retention increased as dietary protein level increased and stage of gestation progressed (linear effect, P less than .01), but efficiency of N utilization and dry matter digestibility decreased with increasing protein intakes (quadratic effect, P less than .05 and linear effect, P less than .01, respectively). Nitrogen retention (P less than .01), efficiency of N retention (P less than .05) and dry matter digestibility (P less than .01) were higher in gilts fed high (H) energy compared with gilts receiving moderate (M) energy diets. Increasing dietary protein increased total carcass separable lean tissue (quadratic effect, P less than .01), liver weight (linear effect P less than .01) SM weight (quadratic effect, P less than .05) and SM percentage M (linear effect P less than .10). Similarly, total carcass N and carcass lean N increased as protein level increased (quadratic effect, P less than .10, P less than .05, respectively). In contrast to the increase in muscle N, N in uterine tissue and fluids was not affected by dietary protein level. The results of this experiment suggest that 146 g of crude protein/d during gestation is just as effective as higher levels of crude protein for litter size or storage of N in reproductive tissue, but 255 to 364 g of protein/d are required to maximize muscle N.     

Effect of Eimeria acervulina infection on nutrient retention with special reference to fat malabsorption in chickens.

Nutritional balance studies were conducted to determine the effect of Eimeria acervulina infection on the retention of nutrients and the efficiency of utilization of protein and energy in the diet during the course of intestinal coccidiosis in chickens. Both light and electronmicroscopic studies were conducted to elucidate the pathogenesis of fat malabsorption in the infected chickens. The infection with E. acervulina during the acute phase of the disease (day 4 to day 8 postinfection) caused a reduction (P smaller than 0.01) in the retention of percent protein, percent ether extract and percent gross energy of the diet with a concomitant increase (P smaller than 0.01) in the concentration of ether extract and gross energy of the excreta. The metabolizable energy value of the diet was also depressed during this phase. During the recovery phase of the disease (day 9 to day 13 postinfection) infected chickens voided excreta containing a slightly greater concentration of ether extract when compared to the controls but differences in the retention of percent protein and percent gross energy were no longer observed. An increased retention of percent phosphorus also occured during the recovery phase. Studies involving the carcass composition revealed that the efficiency of utilization of protein and metabolizable energy of the diet for tissue deposition was reduced (P smaller than 0.05) during day 0 to day 8 postinfection but only the efficiency of metabolizable energy utilization was found to be depressed (P smaller than 0.05) when data for day 0 to day 14 postinfection were analyzed. Both light and electronmicroscopic studies of the duodenal villi of infected chickens during day 5 to day 6 postinfection revealed accumulation of large globules of fat in the villus epithelial cells parasitized by the gammonts of E. acervulina indicating a possible blackade of "fat exit" from these cells.     

The effect of copper and fat addition to the diets of weanling swine on growth performance and serum fatty acids.

A 2 x 3 factorial experiment, encompassing three 28-d trials involving a total of 420 weanling pigs, was conducted to determine the effect of dietary Cu (5 or 250 ppm) and animal fat (0, 2.5, or 5%) on the performance and serum fatty acid profiles of weanling pigs. Pigs had ad libitum access to corn-soybean meal-based diets containing 10% whey and 5% fish meal and similar lysine:calorie ratios. Pigs were weighed and pen feed intakes were recorded weekly. Weekly blood samples were collected during the first two trials (n = 270) for serum fatty acid analysis. There was a Cu x fat interaction for ADG from d 1 to 14 (P less than .07) and over the 28-d experiment (P less than .05). The ADG of pigs fed 250 ppm of Cu increased, whereas the ADG of pigs fed 5 ppm of Cu was not affected as dietary fat increased. The addition of 250 ppm of CU increased (P less than .01) ADFI throughout the 28-d experiment. The addition of fat quadratically increased ADG (P less than .05) during d 14 to 28 and gain:feed ratios (P less than .01) during d 14 to 28 and over the 28-d experiment. The addition of fat decreased (P less than .05) the weight percentage of serum saturated fatty acids and increased (P less than .01) the weight percentage of serum monounsaturated fatty acids on d 28. The addition of 250 ppm of Cu decreased (P less than .01) the weight percentage of monounsaturated fatty acids on d 14 and 28.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of the gut microflora on chick growth and utilisation of protein and energy at different concentrations of dietary protein

The effect of the gut flora on chick growth and protein and energy utilisation at a marginal dietary energy level (calculated metabolisable energy value 11.7 MJ/kg) was determined with diets containing 227 or 293 g protein/kg. Germ-free (GF) and conventional (CV) chicks were reared for 10 d on the diets, and excreta were collected during the last 4 d. The chicks were killed and carcases and droppings were analysed for N and fat. The GF chicks grew significantly faster than the CV controls on both diets. The growth of CV chicks given the high protein diet was similar to that of GF chicks given the adequate protein diet. Protein and energy utilisation were significantly less for CV than for GF chicks on both diets. It was concluded that the energy requirement of CV chicks was greater than that of their GF counterparts, and that their poorer growth was due to utilisation of some dietary protein as an energy source.     

The effect of dietary calcium upon growth rate, food utilisation and plasma constituents in lines of chickens selected for aspects of growth or body composition

1. The effect of increasing dietary calcium from 10.3 to 20 g/kg on 5- to 17-day growth performance and plasma minerals, electrolytes, total protein, albumin and glucose in chickens from 4 lines selected for: high 8-week body weight (W), low abdominal fat (L), high abdominal fat (F) or at random (C) was studied in two experiments. 2. High dietary calcium significantly reduced weight gain and plasma phosphate and potassium but increased food:gain ratio, plasma total calcium, glucose and albumin. 3. Significant correlations were found between plasma total calcium and plasma phosphate (r = -0.5, P less than 0.01), plasma total calcium and protein (r = 0.4, P less than 0.01) and between plasma total protein and albumin (r = 0.55, P less than 0.01). 4. Genotypes differed in their response to dietary calcium content. There was a substantial response in line F but little effect in line L. 5. In contrast to the three other lines, in line F high dietary calcium significantly increased plasma ionised calcium without altering plasma phosphate or total calcium concentration. 6. It was concluded that genetic selection has produced lines which vary in their tolerance to high dietary concentrations of calcium. Birds selected for increased fatness were less tolerant to high dietary calcium than their lean-selected counterparts.     

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.     

Differential effect of age on metabolisable energy content of high protein‐low energy and low protein‐high energy diets in young broiler chicks1

1. An experiment was carried out with 6‐d old male broiler chicks in an attempt to understand better the effect of age on dietary AME_n of high protein‐low energy (HPLE) and low protein‐high energy (LPHE) diets which are used in the determination of the AME_n content of grains when substituted for the entire diet. The experiment was carried out in a split‐plot design in which the effects of 2 diets (HPLE‐reference and LPHE‐test, containing maize) on food intake, faecal excretion, dietary AME_n and the utilisation of the nutrients were evaluated in 3 age periods (A = 11–13, B = 15–17 and C = 20–22 d of age).

2. Chicks fed on the HPLE diet consumed significantly less food than those fed on the LPHE diet during periods A and B, but not in G. They also produced a significantly larger amount of droppings during periods B and C. Food‐to‐droppings ratio, which was consistently and significantly lower in chicks fed on the HPLE diet, decreased markedly in period C only in these birds.

3. Absolute and relative retention (RR) of dry matter (DM) and starch, and RR of nitrogen (N) from birds fed on the HPLE diet, were consistently and significandy lower than from those fed on the LPHE diet, but fat retention (absolute and relative) was higher. RR of DM and of N in period C was significantly lower than in periods A and B, while RR of fat and of starch was not affected by age. The effect of age on RR of N was observed only with the HPLE diet.

4. AME_n of the HPLE diet, but not of the LPHE diet, in period C was significandy lower than in periods A and B, resulting in a significant interaction between age and diet and a general reduction with age. The calculated AME_n contents of the maize in periods A and B were essentially the same (14.91 and 14.85 MJ/kg, respectively), and lower than in period C (15.28 MJ/kg). It is concluded, therefore, that because of its effect on AME_n of the HPLE reference diet in chicks older than 17 d, bird age is of considerable importance in the determination of AME_n in grains when substituted for the entire diet.     

饲粮粗蛋白和蛋氨酸水平对育雏期笼养金定鸭性能的影响

采用饲养试验、代谢试验和屠宰试验研究在等能条件下 (ME :1 1 .9MJ kg) ,不同蛋白质水平 (CP :1 7% ,1 9% ,2 1 % )和蛋氨酸水平 (Met CP :0 .0 2 0、0 .0 2 5、0 .0 30 )完全交叉组成的 9种饲粮对笼养金定鸭育雏期 (0～ 4周龄 )生长性能、养分利用、体成分沉积方面的影响。结果表明 :不同蛋白质水平饲粮对试鸭 0～ 4周龄的体增重、采食量、蛋白、能量、钙、磷的利用率以及蛋白、钙、磷沉积量影响显著 (P <0 .0 5或P <0 .0 1 ) ;不同蛋氨酸水平饲粮对试鸭的上述指标 ,除钙利用率、磷沉积量外 ,影响均不显著 (P >0 .0 5)。氮存留率与能量、钙、磷的利用率随饲粮CP(% )的升高而是降低 ,且各水平间差异显著 (P <0 .0 5) ,却随蛋氨酸水平的升高而升高。蛋白水平与蛋氨酸水平的互作结果为 :对氮存留率、能量和磷的利用率影响差异不显著 (P >0 .0 5) ,且以第 3组 (CP =1 7% ,Met CP =0 .0 30 )效果最好 ,而钙的利用率第 3组效果也较好。因此 ,在本试验条件下 ,饲粮适宜粗蛋白和蛋氨酸水平分别为 :CP(% ) =1 7,Met CP =0 .0 30。     

Growth, food intake and energy balance of layer and broiler chickens offered glucose in the drinking water and the effect of dietary protein content

1. Four experiments were carried out to study the effect of offering a 91.5 g/l solution of glucose, compared to tap water, on fluid intake, food intake and growth of individually-caged immature chickens of both layer and broiler strains. 2. Male chicks of an egg-laying strain were offered glucose solution or tap water from 27 to 62 d after hatching. There was no effect of glucose on fluid intake but it depressed food intake (P less than 0.01) to give equal total energy intakes for each treatment. Body weight gain was reduced (P less than 0.001) and carcase fat content increased (P less than 0.001) by the glucose to yield no difference to total carcase energy. 3. When birds were placed in a respiration chamber for two 23-h periods there was no effect of treatment on outputs of energy as faeces + urine or as heat. 4. Male broilers were offered glucose solution or tap water with diets containing either 150 or 195 g protein/kg from 20 to 55 d after hatching. With the low-protein diet glucose depressed food intake (P less than 0.01) but total energy intake and carcase energy were not significantly affected. With the high-protein diet glucose did not depress food intake but increased total energy intake and total body fat. 5. Layer and broiler chicks were offered either a choice of the low- and high-protein diets or a single diet intermediate in protein content, with glucose solution or tap water. With broilers total food intake was depressed by glucose, mainly by a reduced intake of the low-protein diet. Intake of neither diet by the layer chicks was significantly affected by glucose. 6. It is concluded that provision of extra energy in glucose solution depresses food intake when the resultant energy:protein ratio becomes limiting. With a higher protein diet, or with birds having lower protein requirements, glucose solution does not depress food intake and increased fat deposition occurs.     

Effect of dietary fat concentration and energy to protein ratio on the performance,yield of carcass components and composition of skin and meat of turkeys as related to age

The effects of up to 12.9% added dietary fat (ADF) and a 10% variation in the relative energy to protein ratio (E : P) on performance to 24 weeks and the carcass composition of male turkeys at 4‐weekly intervals were determined. Poults given a low level of ADF required a narrower E : P to 4 weeks and were more sensitive to E : P imbalance than those given higher levels of ADF. The E : P requirement was less critical after 4 weeks. Energy conversion was more efficient with lower ADF to 4 weeks but became more efficient with higher ADF as the birds approached maturity. Energy utilisation was more, and protein utilisation less, efficient with narrower than with wider E : P's. Increased deposition of tissue fat at high ADF levels may explain the increased energy tolerance of poults fed on fat‐rich diets.

Carcass finish and tissue fat deposition were influenced more strongly by the level of ADF than by varying the E : P. The pronounced influence of ADF on the skin and tissue fat of immature turkeys indicates the potential value of increased ADF in diets for early marketed small turkeys.

The yield of carcass components other than skin was not strongly influenced by either ADF or E : P. The percentage eviscerated carcass and edible meat yield increased with age. The percentage yield of wing segments and drumstick decreased with age. Skin yield and tissue fat content first decreased, then increased with age.

Equations were derived to express the relationship of fat content with protein, moisture and age in thigh and breast meat.