Responses to heat stress in commercial and local broiler stocks. 2. Developmental stability of bilateral traits.

1. Developmental stability of bilaterally symmetrical traits was measured in two fast (G1 and G2) and one slower growing (G3) broiler stocks when conditioned (chicks exposed to 36 degrees C for 24 h at 5 d of age) or food restricted (food withdrawn 2 h before the hot period and chicks fed between 17.00 and 08.00 h) during heat stress administered daily from 28 to 49 d of age. 2. Length of face, length, width and weight of shanks, weights of P. major and P. minor muscles, and weights of lung and caeca were chosen as bilateral traits representative of skeletal, muscle, respiratory and digestive systems. 3. Development of skeletal bilateral traits was affected primarily by genotype and sex. The heart:lung ratio decreased with conditioning in stocks G1 and G2 at 21 d. Face length, shank length and shank weight exhibited antisymmetry, whereas shank width and weights of P. minor, lung and caeca exhibited fluctuating asymmetry and antisymmetry. For P. major weight, there was directional asymmetry. 4. In general, relative asymmetry of skeletal traits was lower than for traits associated with muscle and with respiratory and digestive systems. Relative asymmetry of P. major weight was lower in conditioned and G3 broilers than in their respective counterparts. 5. If relative asymmetry is a valid indicator, item heat stress may be less in slower growing and conditioned broilers.     

Alleviation of acute heat stress by food withdrawal or darkness

1. Growing 33-d-old broiler fowl were exposed to air temperatures of 35 to 40 degrees C for a period of 4 h each day for 5 d. 2. The birds were fed on diets providing widely differing proportions and intakes of energy as protein, carbohydrate and fat. 3. Three lighting and feeding treatments were superimposed on the 4-h heat stress period. The treatments were: LF (control) lights and food throughout, NL (no light) extinguished throughout the hot period, NF (no food) food withdrawn 2 h before the hot period and replaced immediately after it. 4. Diet had no significant effect on rate of increase of rectal temperature (TR) during heat stress. 5. The NL and NF treatments significantly reduced the rate of increase of TR and the TR attained after 4 h of heat exposure.     

The effects of early‐age thermal manipulation and daily short‐term fasting on performance and body temperatures in broiler exposed to heat stress

This study was conducted to investigate the effects of thermal manipulation at 5 days of age and short‐term fasting during the warmest part of the day on responses to prolonged heat stress of broilers. A total of 240‐day‐old Ross 308 female broiler chicks were divided into three groups: control, thermal manipulation (chicks were exposed to 36 °C for 24 h at 5 days of age) and short‐term fasting during the warmest part of the day (10.00–17.00 h). Prolonged heat stress was induced daily from 28 to 42 days by heating until the ambient temperature reached 32–35 °C between 10.00 and 17.00 h. Both thermal manipulation and short‐term fasting resulted in a decrease in rectal temperatures and haematocrit values at 35 and 41 days of age. Thermal manipulation improved body weight, feed consumption and feed conversion. However, short‐term fasting caused a reduction in body weight and a deterioration in feed conversion. Short‐term fasting lowered the percentages of carcass, whereas thermal manipulation highered breast yield. Both thermal manipulation and short‐term fasting decreased heart mass and abdominal fat.     

The effect of early-age food restriction on heat shock protein 70 response in heat-stressed female broiler chickens

1. This study was conducted to determine the effect of early-age food restriction on heat shock protein (hsp) 70 synthesis in the brains of female broiler chickens exposed to high ambient temperatures. 2. Chicks were brooded for 3 weeks and then maintained at 24+/-1 degrees C. 3. On d 0, chicks were assigned to one of 4 feeding regimens; each regimen was applied to 4 cages of chicks. The regimens were: (1) ad libitum feeding (AL); (2) 80% food restriction at 4, 5 and 6 d of age (F80); (3) 60% food restriction at 4, 5, and 6 d of age (F60); and (4) 40% food restriction at 4, 5 and 6 d of age (F40). From d 35 to d 41, all chicks were subjected to 38+/-1 degrees C for 2 h/d. 4. One day following food restriction (d 7), hsp 70 expression in the brain samples of F60 and F40 chicks was augmented but not those fed AL and F80. 5. Prior to the heat challenge (d 35), all chicks had similar hsp 70 response. Irrespective of feeding regimen, there was a marked increase in hsp 70 expression after 4 d of heat treatment (d 38). Following 7 d of heat exposure (d 41), except for the F60 chicks, the augmented hsp 70 expression in the brains of AL, F80 and F40 birds was not maintained. 6. Enhancement of hsp 70 expression was noted in birds subjected to F60, but not AL, F80 or F40, throughout the period of heat exposure.     

Growth performance and immune response of two commercial broiler strains fed diets containing Lactobacillus cultures and oxytetracycline under heat stress conditions

1. Hubbard x Hubbard (HH) and Shaver x Shaver (SS) chicks given a dietary supplement of either 50 mg/kg oxytetracycline (OTC) or 1 g/kg Lactobacillus culture (LC) were exposed to 36 +/- 1 degrees C for 3 h daily from day (d) 21 to 42. 2. Prior to heat treatment, body weight (d 21) and weight gain (d 1 to d 21) of OTC and LC birds were greater than those fed the control diet. Chicks given LC had the best food efficiency followed by OTC and control birds during d 1 to d 21. Body weight (d 1 and d 21) and weight gain (d 1 to d 21) were greater for HH tlhan SS chicks. 3. After 3 weeks of heat exposure, birds receiving the LC diet had greater body weight and weight gain, higher food intake and lower food efficiency than OTC and control chicks. 4. Antibody production against Newcastle discase vaccine on d 21 was not affected by strain or diet. On d 42, while diet had negligible effect on this variable among the SS broilers, HH birds fed LC had higher antibody production than those on the control diet. 5. Neither strain nor diet had a significant effect on mortality.     

Effect of diurnal or nocturnal heat stress on egg formation.

1. Mature laying hens were subjected to ambient temperatures sufficient to maintain body temperature of 43 degrees C for periods of 6 to 7 h during the day (eight periods) or the night (five periods). This did not reduce total daily food consumption. 2. The effect of heat stress during the day was mostly on egg-shell quality, being adverse and significant. During the night heat stress caused a significant decrease in egg production, its effect during the day was less marked in this respect. 3. Heat stress thus seems mostly to affect the early stages of shell formation, while its effect on egg production seems to depend on the time at which it occurs in relation to ovulation. 4. These results suggest that egg production is directly affected by heat stress; prolonged heat stress probably also acts indirectly, by suppression of food intake.     

Chick responses to dietary arginine and methionine levels at different environmental temperatures

1. Two experiments were conducted with broiler chicks in battery brooders from 1 to 21 d to determine the broiler chicks' responses to arginine (Arg) and methionine (Met) combinations at control (22 to 25 degrees C) and warm (32 to 35 degrees C) temperatures. 2. In Experiment 1, two levels of Arg (15.2 and 25.2 g/kg of the diet) and two levels of Met (3.5 and 5.5 g/kg) of a maize-soy based diet were fed at two temperatures, 22 or 32 degrees C. Results of Experiment 1 were similar to those of Experiment 2, but most treatment differences were not significant. 3. In Experiment 2, chicks were randomly allotted to 9 dietary treatments: 3 levels of Arg (15.2, 25.2 and 35.2 g/kg of the diet) x 3 levels of Met (3.5, 5.5 and 7.5 g/kg of the diet) at 25 or 35 degrees C. At the warmer temperature, chick growth depression from supplemental Arg was not as severe as at the control temperature (significant Arg x temperature interaction); neither were growth increases as large from supplemental Met (significant Met x temperature interaction). 4. Kidney and breast muscles were collected for arginase activity and creatine analysis, respectively. Remaining chicks were fasted for 10 h and re-fed. Excreta from the next 24 h were collected for total creatine and creatinine analysis. There were no effects of either Arg or Met on muscle creatine concentration at either control or warm temperatures. Chicks raised at 25 degrees C excreted more creatine and creatinine than those raised at 35 degrees C. 5. These results confirm that temperature affects responses to dietary Arg and Met and suggest that the higher temperature slowed the Arg metabolism of chicks through the creatine synthesis pathway.     

Circadian variation in heat production and respiratory quotient in growing broilers maintained at different food intakes and ambient temperatures.

1. Circadian variations in heat production (HP) rate and respiratory quotient (RQ) were measured in growing broilers maintained at 5 ambient temperatures (14 degrees, 17 degrees, 22 degrees, 27 degrees and 32 degrees C) and at 5 rates of feeding [ad libitum intake and 75%, 50%, 25% and 0% (fasting) of ad libitum intake]. 2. In most cases, the HP rate decreased from 10.30 h just after food was given) until 00.30 h (the 1-h dark period), showed an overshoot just after the 1-h dark period and then changed little. 3. Circadian variation in RQ, except in the fasted group, showed a similar pattern, which consisted of increase, decrease and constant phases. 4. Food intake affected the pattern of circadian variation in RQ, although ambient temperature had little effect. Possible effects of food intake on the pattern of circadian variation in HP rate were discussed.     

Protein requirement of fast- and slow-growing chicks

1. Responses of male broiler chicks and male chicks of an egg-laying stock to dietary crude protein (CP) concentrations ranging from 167 to 251 g/kg (metabolisable energy content 13 MJ/kg) were compared from 0 to 21 d of age, using 20 groups of 9 or 10 chicks (5 diets x 2 stocks x 2 replicates). 2. Average growth rate in the broilers was three times that of the layer chicks. The broilers needed at least 251 g CP/kg to maximise their liveweight gain but the layer chicks needed only about 188 g CP/kg. 3. The broiler chicks ate less than twice as much food as the layers and their maximum gain/food ratio was 0.6 compared with 0.4 for the layer chicks. These maximum efficiencies of conversion of food to liveweight were achieved in both cases with a diet containing 230 g CP/kg. 4. The efficiency of protein utilisation (above maintenance) was the same in fast- and slow-growing genotypes (about 0.47 g protein gain/g protein consumed). 5. Carcase analysis at 3 weeks of age showed that the broilers had deposited more fat than the layers and that protein content of the diet had markedly influenced fat deposition in both stocks. Fat in the whole body increased from 29 to 87 g/kg in the layer chicks and from 81 to 123 g/kg in the broilers as dietary protein was reduced from 251 to 167 g/kg. 6. The optimum protein to energy ratio of a chick starter diet will depend on the growth potential of the stock, as well as the cost of ingredients and the value of fatter or leaner carcases.     

Brooding temperatures for chicks acclimated to heat during incubation: effects on post-hatch intestinal development and body weight under heat stress

1.?The objective was to evaluate the effects of brooding temperature on intestinal development, oxidative organ damage, and performance of chicks acclimated to high temperature during incubation. The effects of acclimation and brooding temperatures on slaughter weights of broilers under heat stress were also investigated.

2.?Eggs were incubated at either 37?8°C (INC_Cont) or heat-acclimated at 39?5°C for 6 h daily from d 10 to d 18 of incubation (INC_H). Brooding temperatures at floor level were set at 32, 33?5 and 35°C (Bt₃₂, Bt_33?5, Bt₃₅, respectively) for the first 5 d. The temperature was reduced gradually to 30°C from d 6 to d 10. From 21 to 42 d, broilers from INC_Cont Bt₃₂ and INC_H Bt₃₂ and Bt₃₅ were divided into two groups; half from each group was exposed to daily cyclic higher ambient temperatures, while the other half was reared at control temperature.

3.?INC_H chicks had lower jejunum, but greater liver and residual yolk sac weights than INC_Cont chicks on the day of hatching. Although INC_H chicks from Bt_33?5 and Bt₃₅ had lighter body weights than Bt₃₂ on d 5, no significant differences were observed in the body weight of broilers among treatments at 10 and 21 d.

4.?Similar jejunum protein, alkaline phosphatase, maltase, glutathione, and malondialdehyde contents of chicks from INC_Cont and INC_H suggested that heat acclimation during incubation has no effect on jejunum enzyme activity or oxidative status of chicks.

5.?Taking into account INC_H Bt₃₅ chicks having lower T₃ levels on d 5, lower heterophil/lymphocyte (H/L) ratios and similar weights at 42 d under heat stress compared with control broilers, the results suggested that although higher brooding temperatures had no effect on body weights of INC_H chicks during the brooding period, those broilers may able to cope better with heat stress.     

Comparison of post‐hatch holding time and subsequent early performance of broiler chicks and Turkey poults

1. The effect of a holding period, lasting up to 48 h post‐hatch, on early growth and mortality rate was studied in broiler chicks and turkey poults.

2. After 48 h of food and water deprivation, birds of both species lost about a tenth of their initial post‐hatch weight. Weight loss was more marked in poults subjected to heat stress. Thus, duration of the holding period adversely affected early growth.

3. During the 48‐h holding period, the relative weight of residual yolk decreased in both species by approximately half of its weight in the just hatched chicks and poults. Relative yolk size was much higher in poults than in broilers.

4. On day 1 weight loss was attributed to degradation of the yolk sac, whereas on day 2 only about two‐thirds of the loss could be attributed to residual yolk. Body composition of newly‐hatched broiler chicks did not differ from those held for 24 h despite shortages of energy. However, after 48 h body fat content was markedly reduced compared to newly‐hatched or 24‐h‐old birds.

5. Irrespective of access to food, the relative size of the gastrointestinal tract increased with holding time in both species, reflecting its importance.

6. It was concluded that post‐hatch birds deprived of food and water for 48 h face a severe shortage of energy, causing alterations in body composition. This in turn adversely affects early growth and increases mortality rate under heat stress.     

Energy and nitrogen metabolism of diseased chickens: aflatoxicosis.

1. New Hampshire chicks were fed on diets containing 0 (control), 0-7 (A), or 1-1 (B) ppm of aflatoxin B1. In two trials 1-d-old chicks were offered ad libitum the three diets for 14 d. The gaseous exchange of five chickens from each group was measured for 3 or 4 d, the same diets being fed, at 2, 3, 4 and 5 weeks of age in two series of experiments. The controls were fed at the lower intake of the two other groups. Following each series of experiments at the various ages, birds were starved for 24 h and their heat production was re-measured over the next 24 h. 2. Mortality was highest and growth and food conversion poorest where the diet with the highest aflatoxin concentration was fed. Mortality was confined to the first 2 weeks. 3. Performance of birds in the chambers was improved in the second series due to differences in food intake. It also improved with age suggesting some resistance to the toxin. 4. Mean respiratory quotient was 0-97 for fed chickens on diet B. This was significantly different from 0-92 for the two other groups. Similarly, during starvation the RQ was 0-76 compared with 0-73. 5. birds fed on diet B generally grew better, retained more nitrogen and had a better energy balance in the respiration chambers than the other two groups. Metabolisability of dietary energy was less (68.5%) for all groups at 2 to 3 weeks than when older (70%) but availability of ME was the same (71%) for all groups. 6. Heat production (kJ/kg0-75) of starved birds on diet B was significantly lower than the other two groups, while endogenous nitrogen excretion was higher. 7. Water consumption (ml/g food and g/100 g body weight) was greatest for birds on diet B. 8. Although aflatoxin in the diet substantially reduced intake there was no indication that at these reduced levels of intake, nitrogen or energy metabolism were measurably impaired.     

Effect of dietary amino acids and metabolisable energy on the performance of broilers kept at high temperatures

Increasing dietary metabolisable energy (ME) at particular amino acid: ME ratios significantly improved growth and food utilisation of broilers kept at moderate (18 to 26 degrees C) and high (25 to 35 degrees C) ambient temperatures during the finishing period from 22 d of age. The optimum amino acid: ME ratio varied with dietary ME concentration in the hot, but not in the moderate environment. Relatively greater increases in food intake and growth rate occurred in the hot environment when dietary ME was increased and the amino acid: ME ratio was reduced. The minimum rate of food intake did not coincide with the period of maximum temperature. Increasing the dietary protein at particular ME concentrations had little or no effect on the food intake and growth rate of birds kept at high temperatures. Supplementation with dietary fat had no beneficial effect on performance at high temperatures. The rectal temperatures of birds in the hot environment increased with age and, towards the end of the finishing period, when higher energy diets were fed.     

Water consumption and the effects of water restriction on performance of broilers in the tropics

1. The water requirements of broilers in a hot, humid tropical environment were measured and the effects of four forms of water restriction were investigated over 9 weeks.

2. Voluntary water intake was 10 1 over 9 weeks, about 4–3 1 being consumed during the last 2 weeks.

3. Various degrees and methods of water restriction adversely affected body weight and food conversion throughout the growing period. Food intake was depressed only during the last 4 weeks. High mortality in the restricted birds was due mainly to drowning and heat stress.     

Effect of early-stage thermal conditioning and food restriction on performance and thermotolerance of male broiler chickens.

1. The effects of early-age thermal conditioning and food restriction on performance and thermotolerance were studied in male broiler chickens, in 2 trials. 2. Chickens were exposed to 36 degrees +/- 1 degree C and 70% to 80% relative humidity (RH) for 24 h at the age of 5 d (thermal conditioning, TC), or to food restriction (FR) at the age of 7 to 14 d, or to both treatments (TC+FR), while a control group was reared under standard conditions. At the age of 42 d, chickens were thermally challenged by a heat stress of 350 degrees +/- 1 degree C and 20% to 30% RH for 6 h. 3. In both experiments, weight gain of the TC chickens between the ages of 7 and 42 d was significantly higher than those of other treatments and was associated with higher food intake. 4. Early-age TC significantly increased body temperature (Tb). Thermal challenge at the age of 42 d markedly increased Tb in all groups but that of the TC groups was the lowest. 5. Mortality during thermal challenge was significantly lower in the treated chickens, except for the FR group in trial 2. 6. Plasma triiodothyronine (T3) concentration was greatly depressed in all treatment groups during the thermal challenge. However, the lowest concentration was observed in the TC group, suggesting that these chickens exhibit the lowest rate of heat production under such conditions. 7. Thermal conditioning reduced the increase of haematocrit with age, whereas food restriction resulted in an increase in haematocrit immediately after FR. Thermal challenge resulted in a haematocrit decline in all groups, with the lowest values in the TC and TC+FR chickens. 8. It can be concluded that, because the TC treatment improved thermotolerance (possibly by reducing heat production) and performance, it has advantages over the FR and TC+FR treatments.     

Hepatic concentration of heat shock protein 70 kD (Hsp70) in broilers subjected to different thermal treatments.

1. The relationship between repeated thermal treatments and hepatic synthesis of Hsp 70 was studied in broiler chickens. 2. Sixty broilers were submitted to 5 different treatments (12 birds each) from day 1 to day 42. Four groups were kept in a thermoneutral environment and subjected to 0, 1, 2 and 3 heat stress episodes at 35 degrees C for 4 h per week (TN-0, TN-1, TN-2 and TN-3, respectively). The last group (HT-35) was reared at a room temperature of 35 degrees C. 3. From 39 to 42 old, the birds experienced acute heat stress at 41 degrees C. Resistance to heat stress was evaluated by the time taken for rectal temperature to increase by 3 degrees C above the pre-treatment value. Livers were collected (before and after heat stress) and Hsp70 was determined using Western Blot analysis with monoclonal anti-Hsp70 antibody. 4. Resistance to heat stress and concentration of Hsp70 were higher in those birds subjected to more heat stress episodes during the experimental period (TN-3) and HT-35. A positive correlation was observed between Hsp70 concentration and the time taken for a 3 degrees C increase in rectal temperature (r = 0.42; P<0.01). 5. Exposing birds to episodes of heat stress (35 degrees C) during rearing may improve their resistance to acute heat stress, but the previous thermal history did not seem to influence the hepatocyte Hsp70 content after exposure to more severe heat stress (41 degrees C).     

Effects of environmental temperature on heat production associated with food intake and on abdominal temperature in laying hens.

An experiment was carried out to verify the relationship between the heat production associated with food intake and environmental temperature. Four laying hens were trained to eat two meals per day and were kept under artificial illumination with dark, dim and light periods. 2. Metabolic heat production was measured using two open-circuit respiratory chambers. Abdominal temperatures were measured, using thermocouples, at environmental temperatures of 12, 16, 20, 24, 28, 32 and 36 degrees C and at food intakes of 90, 60, 30 and 0 g/d. 3. The rate of heat production was dependent on both environmental temperature and food intake. Increasing environmental temperature resulted in a decrease in total metabolic rate at any food intake, indicating that heat production associated with food intake was not directly linked with thermoregulation at low environmental temperatures. 4. Abdominal temperature varied little with either food intake or environmental temperature below 28 degrees C. Above 28 degrees C, abdominal temperature increased with both environmental temperature and quantity of food, indicating that the heat production associated with food intake adds to the heat load at high environmental temperatures. 5. Both heat production and abdominal temperature declined with decreasing light intensity and increased before feeding time. These effects were considered to result from changes in physical activity.     

Effect of clinoptilolite on performance of Japanese quail (Coturnix coturnix japonica) during experimental aflatoxicosis

Clinoptilolite (CLI, a natural zeolite), incorporated into the diet at 50 g/kg, was evaluated for its ability to reduce the deleterious effects of 2.0 mg total aflatoxin (AF;83.06% AFB1, 12.98% AFB2, 2.84% AFG1 and 1.12% AFG2)/kg diet on growing Japanese quail chicks from 10 to 45 d of age. A total of 40 Japanese quail chicks were divided into 4 treatment groups (control, AF, CLI, AF plus CLI) each consisting of 10 chicks. The performance of the birds was evaluated. The AF treatment significantly decreased food consumption and body weight gain from the 3rd week onwards. The adverse effect of AF on food conversion ratio was also significant from week 4 of the experiment. The addition of CLI to an AF-containing diet significantly reduced the deleterious effects of AF on food consumption, body weight gain and food conversion ratio. Food consumption was reduced by 14% in quail chicks consuming the AF diet without CLI, but by only 6% for quail chicks consuming the AF plus CLI diet. Similarly, overall body weight gain was reduced by 27% in birds consuming the AF diet without CLI, but by only 8% for birds consuming the AF plus CLI diet. The addition of CLI to the AF-free diet significantly decreased food consumption and body weight gain during week 4, but these parameters were similar to the controls in week 5. No mortality was observed in any of the groups. These results suggest that CLI effectively diminished the detrimental effects of AF on the variables investigated in this study.     

Responses of sexually-maturing pullets to self-selection feeding under different temperature and lighting regimens

1. Pullets allowed to self-select nutrients from a protein concentrate and either a separate complete diet or cereal-based, energy-rich mixture showed preferences for protein and energy which varied in relation to the time of their onset of lay. 2. The selected protein:metabolisable energy (ME) intake ratio increased from 14 g protein per MJ of ME 2 to 3 weeks before sexual maturity to approximately 19 g protein per MJ of ME at and after sexual maturity. 3. This response to self-selection feeding was consistent with different temperatures, lighting patterns and dietary manipulations. 4. Egg mass output was improved by self-selection feeding at hot (25 degrees to 35 degrees C) temperatures in experiments 1 and 2 and at ambient temperatures in experiment 3. No beneficial response in egg mass from self-selection feeding was observed at cold (6 degrees to 16 degrees C) temperatures in experiment 1. 5. Providing 2 h of additional light during the dark (cool) part of the day, with or without 2 h of darkness in the middle of the extended light (hot) period, had no effect on the egg mass output of pullets at hot (25 degrees to 35 degrees C) temperatures.     

Influences of wet feeding and supplementation with ascorbic acid on performance and carcass composition of broiler chicks exposed to a high ambient temperature.

In two experiments was investigated whether feeding with an air-dry feed mixed with different amounts of water and/or supplemental ascorbic acid affect performance and carcass compositions of broilers exposed to a high ambient temperature (35 to 37 degrees C for 8 h/d and thermoneutral for 16 h/d). In the first trial, 64 one-week-old male broiler chicks were fed ad libitum in four dietary treatment groups for a 6-week period. Experimental mash diets were prepared by mixing a maize-soybean based standard broiler starter or finisher with tap water in the ratios of 0.0:1.0, 0.5:1.0, 1.0:1.0 and 1.5:1.0 (water:air-dry feed, w/w). More water in the diet increased BWG, DMI, abdominal fat and carcass weight, carcass CP, crude fat, but it deteriorated DM conversion efficiency. In the second experiment, 64 one-week-old male broiler chicks were given air-dry or wet (water:feed, 1.5:1) starter or finisher diets without or with ascorbic acid supplementation (0 and 250 mg/kg air-dry feed, resp.) ad libitum for a 6-week period. Ascorbic acid supplementation increased BWG, carcass weight and carcass CP significantly, while reducing carcass crude fat content. However, feeding broilers with a diet mixed with water in a ratio of 1.5:1.0 increased BWG, DMI, carcass weight and carcass lipid markedly, but deteriorated DM conversion efficiency. There was also a significant interaction between ascorbic acid and wet feeding, whereby ascorbic acid supplementation induced a significant reduction in carcass lipid contents of broilers fed on air-dry diets but not on wet diets. It is concluded that wet feeding, especially an addition of 150% water to produce a porridge like consistency, improved growth performance by increasing fat, ash and protein deposition in the body, while reducing DM conversion efficiency. It is also concluded that under heat stress supplemental ascorbic acid in air-dry diets stimulates broiler performance but not in wet diets.