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.     

Effect of deficiencies of single essential amino acids on nitrogen and energy utilisation in chicks.

1. Diets 50% deficient in single essential amino acids were fed to chicks from day 8 to day 18 after hatching to evaluate body-weight gain, food consumption, body composition, nitrogen (N) and energy utilisation. 2. Body-weight gain was reduced most severely by deficiency of isoleucine followed in decreasing order by threonine, arginine, valine, histidine, tryptophan, methionine plus cystine, phenylalanine plus tyrosine, leucine and lysine, and possible reasons for the differences are discussed. 3. Body-weight gain and food efficiency were highly correlated with food consumption but metabolisable energy value of diets was not affected by single essential amino acid deficiencies. 4. Generally N retention (N retained/N consumed) and energy retention (energy retained/energy consumed) reflected food consumption, except for a lower N retention by chicks fed on the methionine plus cystine-deficient diet and for a lower energy retention by chicks fed on the valine deficient diet. 5. The amino acid deficient in the diet was present at very low concentration in the blood plasma.     

Effect of dietary factors on the responses of chicks to corticosterone injections

Corticosterone-injected chicks fed on a diet based on sorghum gained less weight and accumulated more hepatic fat than chicks treated similarly and fed on a diet based on maize. The retention of nitrogen and dry matter and the apparent metabolisable energy of these diets were not affected by type of grain, either in corticosterone-injected or in untreated birds. A slight methionine deficiency in the maize diet resulted in an additional increase in the concentration of hepatic lipids in corticosterone-injected chicks. However, hepatic lipid concentration was not affected by either a deficiency or an excess of methionine in the diet based on sorghum. The dietary fat concentration of isocaloric and isonitrogenous diets and the energy concentration of diets containing similar energy-to-protein ratios did not affect the response of the chicks to corticosterone. There was a negative correlation between the relative weight gain of corticosterone-treated chicks and the relative hepatic fat content. The latter was positively correlated with relative abdominal fat pad size.     

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.     

The response of broilers to the feeding of mash or pelleted diets containing maize of varying particle sizes

1. The effects of maize particle size and steam pelleting on growth and nutrient utilisation were studied with broiler chicks. 2. The presence or absence of 10 microg/kg of 1,25 dihydroxycholecalciferol in diets adequate or deficient in phosphorus was also investigated. Food efficiency was superior with the fine maize diets but calcium retention and phytate phosphorus retention were greatest with the coarse maize diets. Pelleting improved food efficiency and growth in both experiments while phytate phosphorus utilisation was decreased. 3. Addition of 1,25-dihydroxycholecalciferol to the diet increased 16-d body weight, bone ash, plasma dialysable phosphorus and retentions of total phosphorus and phytate phosphorus while decreasing phosphorus deficiency rickets and tibial dyschondroplasia. 4. There were significant interactions between maize particle size and food form. The improvement in calcium retention observed with the coarse maize diets was reduced when the diets were pelleted. When fed as a mash, coarse maize diets resulted in increased plasma dialysable phosphorus levels but when the diet was pelleted this response was eliminated. 5. There was also a significant interaction between particle size and phosphorus concentration in that chicks given diets deficient in phosphorus had improved bone ash when fed coarse maize as compared to fine maize. However, this response was eliminated when the diets were adequate in phosphorus. 6. In one experiment, fine maize diets had higher metabolisable energy values and there was a significant interaction between maize particle size and food form as pelleting improved the metabolisable energy value of coarse maize diets but not fine maize diets. In another experiment only pelleting of the factors studied improved the metabolisable energy value of the diets.     

Influence of energy intake on growth and utilisation of dietary protein and energy in germ-free and conventional chicks

The effect of metabolisable energy (ME) intake on the growth and utilisation of dietary protein and energy in germ-free (GF) and conventional (CV) chicks was investigated in two experiments. In experiment 1 a high energy diet (HED, 14.8 kJ ME/g) and a marginally-adequate energy diet (AED, 11.7 kJ ME/g) were fed to the GF and CV chicks at 240 g/2 birds/10 d. In experiment 2 a diet with 13.7 kJ ME/g was fed at 118 g (low level, LL) or 128 g (high level, HL)/bird/10 d. Body weight gain, protein retention and protein retention rate were similar in GF and CV chicks on both AED and HED in the first experiment, but in the second were higher in GF than in CV chicks. The increased ME intake of the CV chicks in experiment 2 may be too small to compensate for the increased requirement. ME intake was significantly higher in the CV chicks than in the GF chicks, whereas energy retention was similar in both groups.     

Effect of short chain fatty acids on the performance and intestinal weight in germ-free and conventional chicks

1. In experiment 1, the performance and tissue weights of germ-free (GF) and conventional (CV) chicks fed on diets containing 25.4 g acetic acid/kg diet (AD) or 25.4 g kaolin/kg diet (KD) were investigated. Body weight gain in GF chicks was significantly higher on the AD, but significantly lower on the KD compared with their CV counterparts. The values for food efficiency, protein retention and energy retention followed a similar pattern to that of the body weight gain. 2. The weights of all sections of the intestine except the colon were significantly greater in CV chicks. In CV but not in GF birds the jejunum and ileum were heavier from birds fed on the AD than from those on the KD diet. 3. In experiment 2, the influence of butyric acid administration on the weight of some organs in chicks was investigated. The weight of duodenum, jejunum and ileum was significantly increased by intraperitoneal administration of butyric acid (2 ml of 100 mM solution/d) for 4 d, but no significant effect was observed by oral administration. 4. It might be suggested that short chain fatty acids such as acetic and butyric acids formed by bacterial action in the crop and subsequently absorbed are at least partly responsible for the heavier gut weight in CV birds.     

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.     

Lactobacilli counts in crop,ileum and caecum of growing broiler chickens fed on practical diets containing whole or dehulled sweet lupin (Lupinus angustifolius) seed meal

1. Four experiments with growing broiler chickens were carried out to study the effects of the inclusion in their diets of lupin (Lupinus angustifolius ) seed meal on E. coli and lactobacilli counts in crop, ileum and caeca at 3 or 4 weeks of age. 2. Diets were formulated to contain the same amounts of metabolisable energy (12.55 MJ/kg) and protein (210 g/kg). Raw whole (heat-untreated) or dehulled sweet (low in alkaloids) lupin seed meal (400 and 320 g/kg respectively) were used to prepare the lupin-based diets, whose protein content was completed with either defatted soyabean meal or casein. 3. Final body weight and food intake of chickens fed on whole lupin seed meal diets were lower than controls, but gain: food ratios were not different. However, birds given the diet with dehulled lupin seed meal had similar body weight, food intake and gain: food values as those of controls. 4. While E. coli counts were not affected, lactobacilli numbers were consistently increased compared to controls in all intestinal sections of chickens fed on the whole or dehulled lupin-based diets, irrespective of the age of the birds or the presence of soyabean meal or casein in the diet. The lactobacilli species isolated were: Lactobacillus fermentum, L. acidophilus, L. salivarius and L. brevis 5. The results suggest that the use of whole or dehulled sweet lupin seed meal in diets for growing broilers might enhance the growth of lactic acid-fermenting bacteria in the gut.     

Nutritional value of raw and autoclaved kabuli and desi chickpeas (Cicer arietinum L.) for growing chickens.

1. Two experiments were carried out to determine the effect of inclusion of raw (kabuli and desi) and autoclaved (desi) chickpea seeds in wheat-based starter diets in chickens grown to 28 d of age on the performance, digestive organ sizes, nitrogen-corrected apparent metabolisable energy (AMEn), ileal apparent protein and starch digestibilities (APD and ASD) and intestinal alpha-amylase and trypsin activities. 2. In the first experiment, diets were formulated to contain 0, 150, 300 and 450 g/kg of raw kabuli chickpea seeds. Increasing the proportion of seed in the diet negatively influenced body weight gain, food intake and food efficiency. The relative weights of the pancreas, liver and gizzard and the relative lengths of duodenum, jejunum, ileum and caeca were increased significantly when the chickpea seeds were included in the diets. Correspondingly, APD, ASD, alpha-amylase and trypsin activities and AMEn were reduced significantly when the chickpea seed was incorporated in the diets. 3. In the 2nd experiment, diets were formulated to contain 75 and 150 g/kg of raw and autoclaved desi chickpea seeds. Weight gain and food intake of the chicks given desi chickpea diets were significantly reduced compared with those fed on the control diet. Increasing the proportion of seed in the diet negatively influenced body weight gain, food intake and food efficiency. Moreover, a significant increment in the relative weights of liver and pancreas, and in the relative lengths of duodenum, ileum and caeca was observed when the concentration of chickpea seeds in the diets was increased. Feeding autoclaved seeds significantly increased the weight gains and the food intakes. However, food efficiency was not modified by the autoclaving. Relative weights of gizzard and liver and relative lengths of ileum were decreased significantly by the inclusion of autoclaved desi chickpea in the diet. 4. We concluded that the inclusion of kabuli (up to 450 g/kg) and desi (up to 150 g/kg) chickpea seeds produced a negative effect on the performance of the birds, and an increment in the relative weights and lengths of the digestive organs. In addition, the incorporation of kabuli chickpea produced a reduction of protein and starch digestibilities, alpha-amylase and trypsin activities, and AMEn of food compared with the birds given the control diet. Autoclaved treatment of desi chickpea improved the performance of the birds.     

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.     

Comparison of the utilisation of palm kernel meal,brewers' dried grains and maize offal by broiler chicks

1. Palm kernel meal (PKM), brewers dried grains (BDG) and maize offal (MO) were included in broiler diets, each at 100, 150 or 200 g/kg; the diets were fed up to 35 d of age. 2. Overall food intake and weight gain decreased in the order BDG, PKM and MO. There were, however, significant interactions between the test ingredients and dietary concentrations in all the growth responses. Food intakes increased with the dietary concentrations of each test ingredient, but the increase was greater for BDG than PKM or MO. For weight gain, at 100 g/kg, the final body weights of the chicks fed on the diets with BDG and MO were similar, and those of chicks fed on the diet with PKM slightly lower. However, at 200 g/kg, growth rate of chicks fed on the BDG and PKM diets were similar while those of chicks fed on the MO diet was 7% lower. Efficiency of food utilisation was similar at 100 g/kg for all the ingredients and decreased as their concentrations increased; however, the decrease was considerably less for the PKM than for the MO and BDG diets. 3. Broilers fed on the BDG-based diets voided most excreta followed by those fed on the PKM and MO diets; excreta water content was highest from birds fed on the MO diets followed by the PKM and BDG diets. Apparent retention of dry matter was similar with all the test ingredients, but it decreased only significantly at 200 g/kg dietary concentration. The rate of passage was faster with the PKM diets followed by the MO and BDG diets; it was increased at 200 g/kg dietary concentration of the test ingredients.     

European reference method of in vivo determination of metabolisable energy in poultry: reproducibility, effect of age, comparison with predicted values

1. Apparent metabolisable energy corrected to zero-nitrogen retention (AMEn) was measured using the European reference procedure in 9 European laboratories. Seven pelleted diets were evaluated. AMEn was measured with adult cockerels and young birds. 2. Between-laboratory standard deviations were for dry matter (DM) 12.5 g/kg, gross energy 0.085 MJ/kg DM, Kjeldahl nitrogen 0.768 g/kg DM, AMEn (adults) 0.256 MJ/kg DM, and AMEn (young) 0.337 MJ/kg DM. Corresponding coefficients of variation between laboratories were 1.42, 0.45, 2.15, 1.88 and 2.60% respectively. 3. AMEn values of experimental diets were always significantly lower when measured with young birds. This effect was more pronounced when diets contained added fat. 4. Tallow or soyabean oil were incorporated into two basal diets at 40 g/kg inclusion rate. No significant differences were observed between AMEn values of either diet with adults or young birds, suggesting that AMEn energy values of these fats are indistinguishable at this inclusion rate. 5. Similar AMEn values were obtained in young birds by estimating nitrogen accretion, either by the difference between intake and excreta nitrogen or by measuring body weight gain. Determined AMEn values were very similar to those predicted using three different regression equations.     

Effects of beta-glucanase-producing Lactobacillus strains on growth, dry matter and crude protein digestibilities and apparent metabolisable energy in broiler chickens

The effects of beta-glucanase expressed by transformed Lactobacillus strains on growth performance, apparent digestibilities of dry matter and crude protein, and apparent metabolisable energy were studied. Two hundred and forty 1-d-old chicks (Avian-43) were randomly divided into three dietary treatment groups and fed with the following diets: (i) basal diet (control) (BD); (ii) basal diet with parental Lactobacillus strains (BDP) and (iii) basal diet with transformed Lactobacillus strains (BDT). At 21 d of age, the body weight, body weight gain and feed conversion ratio of the BDT-fed chickens were significantly improved. At 14 and 21 d of age, the proportions of dry matter in the duodenum, jejunum, ileum, caeca and excreta of chickens given the BDT diet were significantly higher than those of chickens given the BD and BDP diets. Apparent metabolisable energy, digestibilities of crude protein and dry matter were also significantly improved (by 3.5, 5.6 and 3.5%, respectively) by the BDT diet. These results showed that the transformed Lactobacillus strains improved digestibility as well as enhanced the growth performance of chickens.     

Supplementation of diets containing pea meal with exogenous enzymes: effects on weight gain,feed conversion,nutrient digestibility and gross morphology of the gastrointestinal tract of growing broiler chicks

1. The potential for the nutritional improvement of pea-based diets by supplementation with a cocktail of exogenous carbohydrases was investigated using growing broiler chicks. 2. Pea meals (grown in the UK) were included in wheat-based diets at 300 g/kg as a partial replacement for an approximately isonitrogenous mixture of wheat and soybean meal. A wheat/soybean meal diet served as a control and each diet was supplemented with a cocktail of alpha-amylase, pectinase and cellulase. The diets were fed to 1-d-old broiler chicks for a period of 21 d. Weight gain and feed conversion were monitored weekly and excreta were collected during the final week in order to determine nutrient digestibility coefficients and metabolisable energy. On d 21, the gastrointestinal (GI) tract was excised and gross morphology measured. 3. Inclusion of pea meal reduced weight gain, feed conversion, nutrient digestibility and also increased the relative sizes of the distal sections of the GI tract. 4. Enzyme addition partially ameliorated the detrimental effects of pea meal inclusion although similar improvements were also noted for birds fed on the control diet. 5. It is concluded that the nutritive value of pea-meal-based diets can be improved by the addition of carbohydrases, and that some pea cultivars show considerable potential as vegetable protein sources for broiler chicks.     

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.     

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.     

Effect of dietary high- and low-methylated citrus pectin on the activity of the ileal microflora and morphology of the small intestinal wall of broiler chicks.

1. A study was conducted with broiler chicks to evaluate the effects of dietary high-methylated citrus pectin (HMC) or low-methylated citrus pectin (LMC) on the performance, nutrient digestibility, morphology of the small intestinal wall and ileal microbial activity. 2. Both pectin products were tested at a dietary content of 30 g/kg using a diet based on maize and soya flour. 3. Inclusion of HMC in the diet depressed weight gain and food utilization significantly. With a dietary addition of LMC there were only small decreases in weight gain and food utilisation. 4. Digestibility of dry matter, organic matter, crude fat, starch and amino acids, nitrogen retention and metabolisable energy value were reduced significantly when HMC was added to the diet. The addition of LMC to the diet reduced fat and ash digestibility and metabolisable energy value significantly. 5. Inclusion of LMC in the diet increased ileal viscosity marginally, whilst HMC had such an effect that the supernatant could not be extracted. Microbial activity in the ileum, particularly that of Enterococci, Bacteroidaceae, Clostridia and E. coli, was increased significantly with dietary addition of HMC. Inclusion of LMC in the diet did not greatly affect microbial activity as only the number of Clostridia was increased. 6. The addition of HMC to the diet markedly affected the morphology of the intestinal wall and significantly increased the number of goblet cells per 100 villus cells and the sucrase isomaltase activity was increased significantly. However, the morphology of the intestinal wall was hardly affected by LMC, whereas the number of goblet cells per 100 villi cells was significantly increased. 7. Results of the present study indicate that the inclusion of water-soluble pectins in diets of chicks changes ileal microbial activity and the morphology of the small intestinal wall. The magnitude of these changes depends on the degree of methylation of the pectins.     

Nutritional value of D-xylose and L-arabinose for broiler chicks.

1. Two experiments were conducted to examine the effect of feeding D-xylose and L-arabinose on broiler performance, body composition, caecal length and weight, and liver weight. 2. Graded amounts (25, 50 and 75 g/kg) of D-xylose or L-arabinose were added to either a practical type (Exp. A) or a semi-purified (Exp. B) basal diet. As reference, a diet containing 75 g D-glucose/kg was included in both experiments, which were conducted in battery brooders, the birds receiving the isocaloric [on metabolisable energy (ME) basis] diets as dry mash ad libitum from 6 to 27 d of age. 3. A negative dose-dependent effect of both pentose sugars on weight gain and feed utilisation was observed. The same was true for daily food intake of the D-xylose diets. Water intake increased linearly (P less than 0.05) as the dietary concentrations of both pentose sugars was increased. Consequently, dry matter content of the droppings decreased. 4. Fat content of the chick body tended to decrease when either D-xylose or L-arabinose was included in the diets. 5. Caecal weight was increased markedly by feeding L-arabinose. Liver weight was not affected by feeding either D-xylose or L-arabinose to birds. 6. From data for ME intake and gain in body energy it was estimated that utilisation of the ME of both pentose sugars was inferior to that of D-glucose.     

Productive performance of Creole chickens and their crosses raised under semi-intensive management conditions in Yucatan, Mexico

1. The productive performance of 4 chicken breed groups managed under semi-intensive conditions in Yucatan, Mexico was evaluated. Thirty-six mixed chickens, one week of age of each of the 4 breed groups (Creole, F1 Hubbard x Creole, 7/8 Hubbard x 1/8 Creole and Hubbard) were used. 2. During 1 to 3 weeks of age all birds were fed on a diet containing 210 g/kg crude protein (CP) and 12.95 MJ/kg metabolisable energy (ME). From weeks 4 to 7, they were given a diet with 190 g/kg CP and 12.55 MJ/kg ME. Food consumption and live body weight were recorded weekly. Statistical analysis of the data was performed according to complete randomised design and means comparison using Tukey test was carried out when necessary. 3. Creole chicks had the lightest weights at all ages as compared to their crosses and the Hubbard birds. At 7 weeks of age, Creole chicks were 2.11, 2.44 and 2.90 times lighter than their contemporary F1, 7/8 Hubbard x 1/8 Creole and Hubbard birds, respectively. Hubbard birds were heavier than F1 and 7/8 commercial x 1/8 Creole birds, and the latter group heavier than the F1 birds. Similarly, Creole chicks had the lowest growth rate compared to the other genetic groups. Heterosis for body weight up to 7 weeks of age was 8.2%. 4. Feed consumption was also lower for the Creole chicks at all ages. Food:gain ratio, however, was higher for the Creole chicks at all ages. Food:gain ratios from weeks 2 to 7 were 2.18, 2.65, 3.04 and 4.36 for the Hubbard, 7/8 Hubbard x 1/8 Creole, F1 and Creole birds, respectively. Heterosis for food:gain ratio from 2 to 7 weeks of age was -7.0%. 5. Crossbreeding of Mexican Creole birds with commercial type broilers might improve productive performance.