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Influences of wet feeding and supplementation with ascorbic acid on
performance and carcass composition of broiler chicks exposed to high
ambient temperature
Article in Archives of Animal Nutrition · February 2001
DOI: 10.1080/17450390109381972 · Source: PubMed
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Influences of wet feeding and supplementation with ascorbic acid on
performance and carcass composition of broiler chicks exposed to a high
ambient temperature
H. R. Kutlu a
a Agricultural Faculty, Department of Animal Science, Çukurova University, Adana, Turkey
To cite this Article Kutlu, H. R.(2001) 'Influences of wet feeding and supplementation with ascorbic acid on performance
and carcass composition of broiler chicks exposed to a high ambient temperature', Archives of Animal Nutrition, 54: 2, 127 — 139
To link to this Article: DOI: 10.1080/17450390109381972
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INFLUENCES OF WET FEEDING
AND SUPPLEMENTATION WITH ASCORBIC
ACID ON PERFORMANCE AND CARCASS
COMPOSITION OF BROILER CHICKS
EXPOSED TO A HIGH AMBIENT
TEMPERATURE
H. R. KUTLUThe University of Çukurova, Agricultural Faculty, Department of Animal Science, Adana, Turkey
(Received 4 April 2000)
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 composi-tions of broilers exposed to a high ambient temperature (35 to 37°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 con-version efficiency. In the second experiment, 64 one-week-old male broiler chicks were given air-dry or wet (waterfeed, 1.5:1) starter or finisher diets without or with ascorbic acid supple-mentation (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
Address for correspondence: Prof. Dr. H. R. Kutlu, Çukurova University, Agricultural Faculty, Department of Animal Science, 01330 Adana-Turkey. Tel.: +90.322.3386822, Fax: +90.322.3386576, e-mail: hrk@mail.cu.edu.tr
127
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.
Keywords: Wet feeding; Ascorbic acid; Broilers; Performance; Carcass composition
1. INTRODUCTION
In many countries of the world, particularly in the hot and humid tropics, high environmental temperature is of major concern for broiler producers. It is well documented that high environmental temperatures reduce feed intake, body growth and feed conversion efficiency (e.g., Kutlu and Forbes, 1993a). Very often the reduction in performance of broiler chicks is attributed to a rapidly reduced feed intake at high environmental temperature to avoid the thermogenic effect of the ingested feed (Donkoh, 1989). Many studies have been done to alleviate the heat stress effect on broiler performance. Dietary studies revealed that feeding with highly moisturised diets could be of benefit in increasing broiler performance at high environmental tempera-tures. Abasiekong (1989) reported that water addition to the diet in the ratios of 0.33:1 or 0.5:1 (watenfeed, w/w) increased both feed intake and body growth under high temperatures (37°C), but depressed feed intake and body growth considerably at normal temperatures (20°C). Similarly, Tadtiyanant et al. (1991) reported that DMI of layers maintained at high environmental temperatures (33.3°C) could be increased by wet feeding with a diet contain-ing 50% moisture. These studies revealed that birds' response to wet feedcontain-ing under high environmental temperature depends upon water or moisture level in the diet. It has been reported that diets containing more than 60% mois-ture (a porridge-like consistency) increased BWG and DMI of broilers at normal (20 to 22°C) temperatures (Kutlu et al. 1995a,b,c) and feed intake of layers under heat stress conditions (35 to 37°C) (Kutlu et al. 1995d). Yalda and Forbes (1995, 1996) and Yasar and Forbes (1999) also showed increased gain, feed intake and better feed conversion efficiency when they fed broiler chicks with highly moisturised diets at thermoneutral conditions (20 to 22°C). These authors concluded that the most effective mixing ratio of water with feed could be dependent upon dietary ingredients and the maximum progress could be achieved by mixing dry feed with water up to the maximum water holding capacity or so called "porridge-like consistency".
CHICKENS AND HIGH AMBIENT TEMPERATURE 129
It has been reported that in stressful situations such as high temperature, humidity, high productive rate and parasitic infestation, endogenous ascor-bic acid synthesis by birds is insufficient to meet physiological needs and under such conditions supplementation with ascorbic acid could be benefi-cial (Horning e tal., 1984). Ascorbic acid has been, therefore, one of the most widely studied nutrients in alleviating the effect of heat stress on poultry per-formance, with varying degrees of success. It has been reported that supple-mental ascorbic acid improved BWG of broilers under heat stress (Kafri and Cherry, 1984; Pardue et al., 1985a; Njoku, 1986; Kutlu and Forbes, 1993b,c; McKee etal., 1997). However, no improvements in growth performance of broilers were reported in other studies when dietary supplemental ascor-bic acid was provided at high temperatures (Pardue et al., 1985b; Stilborn et al, 1988). McKee et al. (1997) attributed the variability in the literature with respect to responses to ascorbic acid supplementation in poultry to the vitamin's inherent stability, experimental methodology or the paradoxical biphasic effect of ascorbic acid on steroidogenesis.
The presented literature suggest that wet feeding could be of value in alleviating heat stress effects on broiler performance, however, the litera-tures could not provide consistent results, regarding watenfeed ratio to achieve the maximum effect of wet feeding. In fact, none of these stud-ies carried out on broilers at high temperatures described above used a porridge-like consistency in terms of watenfeed mixing ratio, which has now been appeared to be one of the most significant prerequisites to attain the maximum effect on improving growth performance. Furthermore, bene-ficial effects of dietary supplemental ascorbic acid on performance of heat-stressed broilers in wet feeding has not been studied. The present study was, therefore, initiated to determine whether wet feeding with diets mixed with different amounts of water and/or supplemental ascorbic acid would affect performance and carcass composition of broilers at high environmental temperature.
2. MATERIALS AND METHODS
Effects of wet feeding and/or ascorbic acid supplementation on growth per-formance were assessed in two consecutive experiments using one-week-old male broiler chicks (Ross PM3) obtained from TKV Poultry Breeding Unit, Tarsus-Turkey. Standard broiler starter (from day 8 to 28) and finisher (from
day 29 to 49) mash feeds (Tab. I) were used as basal diets throughout the experiments.
In the first experiment, 64 chicks were divided into 4 groups of similar mean BW, comprising 16 birds each. The desired porridge-like consistency of the feed was achieved by addition of 1.5 kg of water to each kg of air-dry basal feeds, which was the highest wetting ratio in the trial. The experimental diets were prepared daily by adding tap water to the pre-weighed basal diets in following ratios (watenfeed, w/w): 0.0:1.0 (air-dry), 0.5:1.0 (50% wet),
1.0:1.0 (100% wet) and 1.5:1.0 (150% wet).
In the second experiment, 64 chicks were divided into 4 groups of similar mean BW, comprising 16 birds each. A 2 x 2 factorial arrangement was
TABLE I Composition and nutrient contents of the experimental diets
Ingredients \g/kg]
Maize, ground
Soybean meal (CP 440 g/kg) Full fat soya
Wheat middlings
Meat and bone meal (CP 340 g/kg) Fish meal (CP 660 g/kg) Vegetable oil Dicalcium phosphate Limestone, ground NaCl DL-methionine Vitamin premix1 Trace-mineral premix2 Coccidiostat Analyses [g/kg] Dry matter Crude protein Ether extract Crude fiber Crude ash Lysine Methionine + Cystine Ca Available P Sodium ME [MJ/kg] Basal diets
Starter (day 8 to 28) Finisher {day 29 to 49)
500.0 194.8 150.0 50.0 50.0 13.1 21.7 6.2 3.1 3.9 2.6 2.5 1.0 1.0 892.4 223.2 71.9 40.5 47.3 12.0 9.5 9.5 5.0 2.3 12.8 500.0 162.0 150.0 70.0 30.0 10.4 47.4 11.8 6.9 4.4 2.6 2.5 1.0 1.0 893.2 202.8 98.4 38.2 38.3 10.8 9.0 9.8 5.0 2.3 13.4 1 Provided per kg diet: 12,000,000 IU vit. A, 1400,000 IU vit. D3,50g vie. E, 5 g vit. K Î , 3 g vit. Bi, 6 g vit. Ba, 25 g Niacin, 12g Ca-D-Pantothenate, 5 g vit B6,30mg vit. B u , 1 g folie acid, 50mg D-biotin, 2.5 g apo carotenoic acidesther, 400 g choline chloride.
2 Provided per kg diet: 80 g Mn, 60 g Fe, 60 g Zn, 5 g Cu, 0.2 g Co, 1 g 1,0.15 g Se.
CHICKENS AND HIGH AMBIENT TEMPERATURE 131
employed with two levels of ascorbic acid (0 or 250mg/kg air-dry feed) in wet versus air-dry diets as main effects. According to the experimental design, four feeding treatments ( 1 : air-dry diet, 2: ascorbic acid supplemented air-dry diet, 3: wet diet, 4: ascorbic acid supplemented wet diet) were applied. Ascorbic acid (coated ascorbic acid, Roche Must. A. §. Levent-istanbul) was supplemented by dissolving 250 mg ascorbic acid in 50 ml distilled water, spraying onto and thoroughly mixing with each kg of air-dry feeds. Unsupplemented air-dry feeds were also sprayed with 50 ml distilled water to equalise DM contents of ascorbic acid supplemented and unsupplemented diets. Wet diets were prepared daily by adding tap water in the ratio of 1.5:1.0 (watenfeed, w/w; 150% wet).
Each experiment lasted 6 weeks and during this time birds were housed in 64 individual cages of three tier wire blocks in a complete randomised design. Referring to temperature, moisture, ventilation and light the experimental room was fully controlled. During both experiments the chicks were reared at conventional ambient temperature (from 30 reducing to 21°C by 3°C/week) and a relative humidity of 60 to 70%, except during periods of heating when the environmental temperature fluctuated from 35 to 37°C with a relative humidity of 40 to 50% for 8 h per day (09.00 to 17.00). Feed and water were always available and light was provided for 24 h per day.
In each experiment, broiler growth performance was assessed by mea-suring DMI daily, BWG and DM conversion efficiency weekly. In order to calculate DMI of birds, DM content of each experimental diet was deter-mined and also adjusted according to daily evaporation loss by filling and placing a feed container in an empty cage for each diet separately. At the end of each experiment when the birds were 7 weeks of age all the birds were slaughtered to determine carcass weight and carcass yield. Five birds which had similar BW to the mean BW of their group at 49 d of age were selected for carcass analysis. Minced carcass was analysed for CA, CP and EE. Frozen samples from carcass was freeze-dried to constant weight for 48 h, fat was, then, extracted from the dried sample with boiling ether using the Soxhlet apparatus. Carcass CA was measured by heating in a muffle
furnace at 500cC for 6 h. CP content of minced carcass were estimated by
nitrogen determination using the Kjeldahl method. All analyses were carried out according to the methods published by MAFF (1985).
Data of the first experiment were analysed statistically by GLM proce-dure and data obtained in the second experiment were subjected to two-way variance analyses using ANOVA procedure of SAS software (SAS Institute,
1985). In both experiments treatment means were separated using Duncan's New Multiple Range Test.
3. RESULTS 3.1. Experiment 1
The results obtained in the first experiment are summarised in Tables II and III. At both 28 and 49 d of age wet feeding affected BWG, DMI and DM conversion efficiency significantly. The groups receiving the 150% wet diet achieved significantly higher BWG than the other groups. At day 28 and 49 DMI was also significantly increased in groups receiving 50, 100 or 150% wet diets compared to the air-dry feeding group. However, the air-dry fed ani-mals converted feed into gain much more efficiently than the wet fed aniani-mals. Carcass weights were effected in a similar manner to BW: the group receiving the 150% wet diet provided a significantly heavier carcass than the other groups. Wet diets also increased abdominal fat pad weight in a dose related manner. The groups fed with 150% wet diets exhibited the greatest abdominal fat pad weight or percentage followed by 100% wet and 50% wet or air-dry feeding groups. Carcass yield was not affected by wet feeding, but increased water level in the diet induced a concomitant increase in carcass crude fat and protein contents.
TABLE II Effect of wet feeding on growth performance of broiler chicks (Experiment 1 )
8 to 28 days of age
BWG [g per bird in 21 d] DMI [g per bird in 21 d] DM conversion efficiency [kg DMI/kg BWG] 8 to 49 days of age BWG [g per bird in 42 d] DMI [g per bird in 42 d] DM conversion efficiency [kg DMI/kg BWG] Air-dry 721b 1034e 1.44b 1972b 3874e 1.96b Feeding groups 50% wet 740b 1.49ab 2028b 4041e 1.99b 100% wet 764ab 1155b 1.52a 2075b 4345b 2.09a 150% wet 812a 1253a 1.55a 2182a 4645" 2.13a SED1 9.26 14.4 0.02 17.7 41.4 0.01
Means in same line with different superscript letters are significantly different (P<0.05). 'SED: SD of difference between means.
TABLE III Effect of wet feeding on carcass parameters of broiler chicks (Experiment 1)
Carcass weight [g/antmal] Carcass yield
[%ofBWatday49] Abdominal fat weight
[g/animal]
Relative abdominal fat weight [% of carcass weight] Carcass crude ash
[g/kg carcass] Carcass crude protein
[g/kg carcass] Carcass crude fat
[g/kg carcass] Air-day 1506b 72.8 28.8C 1.91° 32.7 177b 132" Feeding groups 50% wet 1533b 72.1 31.4C 2.06c 32.8 181ab 139ab 100% wet 1571" 72.3 41.4b 2.62b 34.1 186a 143a 150% wet 1672a 73.2 53.5a 3.19a 32.4 182ab 144a SED1 16.7 0.33 1.06 0.06 0.71 0.82 1.47 Means in same line with different superscript letters are significantly different (P<0.05).
"SED: SD of difference between means.
TABLE IV Effect of wet feeding and ascorbic acid supplementation on growth performance of broiler chicks (Experiment 2)
8 to 28 d of age BWG[gperbirdin21d] DMI[gperbirdin21d] DM conversion efficiency [kgDMI/kgBWG] 8 to 49 d of age BWG[gperbirdin42d] DMI[gperbirdin21d] DM conversion efficiency [kg DMI/kg BWG] Ascorbic acid {mg/kgfeed] 0 250 X 0 250 X 0 250 X 0 250 X 0 250 X 0 250 X Dry 718C 764b 740" 1027b 1075b 1050x 1.43b 1.41b 1.42" 1982e 2073b 2026" 3812b 3919b 3864" 1.92b 1.89b 1.91" Feed Wet 816a 850" 833" 1279a 1319a 1299» 1.57a 1.56a 1.56" 2157a 2184a 2170* 4474a 4517a 4495* 2.08a 2.07a 2.07* X 765" 807" 1149 1197 1.50 1.48 2067" 2128? 4132" 4218* 2.00 1.98 SED1 7.72 12.3 0.01 12.3 36.7 0.01
*b c Means with different superscript letters represent a significant interaction ( P < 0.05). x y Means with different superscript letters represent a significant main effects (P<0.05). 1 SED: SD of difference between interaction means.
TABLE V Effect of wet feeding and ascorbic acid (AA) supplementation on carcass param-eters of broiler chicks (Experiment 2)
Variables
Carcass weight [g/animal]
Carcass yield [%ofBWatday49] Abdominal fat weight
[g/animal]
Relative abdominal fat weight [% of carcass weight] Carcass CA [g/kg carcass] Carcass CP [g/kg carcass] Carcass EE [g/kg carcass] Ascorbic acid [mg/kgfeed] 0 250 X 0 250 X 0 250 X 0 250 X 0 250 X 0 250 X 0 250 X Feed Dry 1514e 1586b 1549" 73.5 73.6 73.6 35.3b 32.6b 34.0* 2.34b 2.06b 2.21" 35.2 34.0 34.6 183b 190a 187 137a 124b 130* Wet 1653a 1664a 1659* 73.8 73.9 73.9 47.5a 47.1a 47.3* 2.86a 2.83a 2.84* 34.1 34.2 34.1 185b 187ab 186 143a 141a 142^ X 1582* 1625" 73.7 73.7 41.2 39.8 2.59 2.45 34.6 34.1 184" 188* 140" 132* SOT1 9.92 0.16 0.94 0.05 0.16 0.72 1.02
*b c Means with different superscript letters represent a significant interaction (P<0.05).
"•' Means with different superscript letters represent a significant main effects (P<0.05).
1 SED: SD of difference between interaction means.
Additionally, wet feeding caused rapid growth/heat stress-associated mortality only in the last week of the experiment. A total of 4 birds, 1 from the 50% wet group, 1 from the 100% group and 2 birds from the 150% wet group, died. After post-mortem examination, the mortality was attributed to sudden death syndrome (SDS).
3.2. Experiment 2
The results obtained in the second experiment are summarised in Tables IV and V. Wet feeding affected BWG, DMI and DM conversion efficiency of chickens in both feeding periods. The groups fed on wet diets had a signifi-cant greater weight gain and DMI than the groups receiving air-dry diets. Wet feeding, however, increased also DM conversion efficiency until 28 and 49 d of age.
CHICKENS AND HIGH AMBIENT TEMPERATURE 135
Carcass weight, carcass crude fat, abdominal fat weight and percentage were also affected by wet feeding which increased carcass weight, car-cass crude fat, abdominal fat weight, and percentage in a similar manner to weight gain. However, carcass yield, carcass ash and carcass protein were not affected by wetting.
The results obtained at 49 d of age also showed that supplemental ascorbic acid affected BWG, DMI, carcass protein and fat contents. The air-dry fed animals receiving supplemental ascorbic acid attained significantly higher BWG and DMI and exhibited higher carcass protein and lower carcass fat values than its unsupplemented counterpart. However, no significant differ-ences were observed between the performance and carcass parameters of the groups receiving ascorbic acid supplemented or unsupplemented wet diets. In this experiment altogether 2 birds, one from each wet feeding group, died suddenly in the last week of the experiment. After post-mortem exam-ination the mortality was also attributed to SDS.
4. DISCUSSION
The results of the two experiments clearly demonstrate a considerable advan-tage for wet feeding in terms of improving feed intake and weight gain with a proportionate increase in body fatness but with a significant reduction in feed conversion efficiency in broilers under high environmental temperature. Our results regarding BWG and DMI are in agreement with those reported by Abasiekong (1989); Yalda and Forbes (1995,1996) and Yasar and Forbes (1999). However, with respect to DM conversion efficiency our results do not support the findings of Yalda and Forbes (1995, 1996). They reported that at thermoneutral conditions the improvements in BWG by wet feeding were due to increases in feed intake and also in feed conversion efficiency (Yalda and Forbes, 1996), but the latter was significantly affected in only three trials out of five (Yalda and Forbes, 1995). With respect to the most effective mixing proportion of water and feed to increase performance of broilers under high temperatures, the results obtained in this study are not in agreement with those reported by Abasiekong (1989). He reported that at high temperatures (37°C) wet feeding in the ratio of 0.33:1.0 (watenfeed, w/w) induced greater feed intake and BWG than a ratio of 0.5:1.0. Although a ratio of watenfeed lower than 0.5:1.0 was not tested in the present experi-ment, DMI and BWG were greater with an increasing water content in the
diet and the highest DMI and BWG were achieved at a ratio of 1.5:1.0 or so called "porridge-like consistency".
The increase in BWG as a result of wet feeding could be attributed to increased DMI. Our results showed that DMI can be stimulated easily by water addition. This may offer an effective way to increase DMI under heat stress. However, the increase in BWG was not proportional to the increase in DMI, so DM conversion efficiency was poorer. This may be explained by the time requirement for proper digestion. In fact, wetting makes the diet much more soluble and induces a very rapid transit of feed, particularly in broilers, which exhibit high satiety. Increased transit rate of feed through gastrointestinal tract is normally expected to stimulate feed intake but also reduce feed conversion efficiency owing to less time for digestion and nutri-ent absorption (Duke, 1986). Rayner and Millar (1990) reported that in pigs receiving dry or wet feed (2:1, watenfeed) rates of eating and stomach emp-tying were approximately doubled by wetting. Therefore, it can be expected that increased feed intake would result in a lower efficiency of conversion of feed into gain. This might provide a relevant explanation for increased feed intake but reduced feed conversion efficiency by wet feeding in broilers.
At high environmental temperature a supplementation of ascorbic acid improved feed intake, weight gain and feed conversion of air-dry fed broilers only. The positive effects of ascorbic acid with air-dry diets are in agreement with the findings of Kafri and Cherry (1984); McKee et al. (1997); Njoku, (1986) and Kutlu and Forbes (1993a,b). This may suggest that efficacy of ascorbic acid are closely related to the degree of instability in the ascor-bate molecule. McDowell (1989) has described ascorbic acid as "the least stable, and therefore most easily destroyed, of all vitamins". Factors that con-tribute to oxidative degradation of ascorbic acid include the presence of metal ions, oxygen, moisture, light, heat and neutral to alkaline pH (Pardue et al., 1993). Although the ascorbic acid used in the present study was coated with ethylcellulose to retain biological activity against the destructive factors, in wet diets it did not seem to retain its biological activity. In fact, not only moisture itself but presumably its positive effects on solubility of metal-ions or influence on vitamins by metal ions interactions in the diet may contribute to a destruction of ascorbic acid in wet diets.
The likely mechanisms whereby ascorbic acid alleviates heat stress are discussed by Kutlu and Forbes (1993a), who supported the hypothesis of Kitabchi and West (1975) that ascorbic acid inhibits steroidogenesis. It appears that under heat stress, increasing ascorbic acid in the diet prevents
CHICKENS AND HIGH AMBIENT TEMPERATURE 137
the negative influences of corticosteroid hormones by reducing their synthe-sis and this improves the performance of heat stressed birds. Ascorbic acid may also play a significant role in maintaining body temperature under heat or cold stress (Thornton, 1962). Regulation of body temperature by ascorbic acid certainly helps to maintain haemostasis in homeothermic animals, like birds. Furthermore, McKee et al. (1997) reported that ascorbic acid influ-ences body nutrients stores that are used for energy purposes during periods of reduced energy intake as happens during heat stress or feed withdrawal. It has been reported that an increase in environmental temperature (Baziz et al, 1996) or plasma corticosterone (Kutlu and Forbes, 1994) enhanced fat deposition in broilers. Any attempt to reduce corticosterone synthesis or secretion under heat stress would, therefore, result in lower fat deposition. Our results confirm the above claim, as ascorbic acid reduced carcass crude fat and increased carcass crude protein without any significant change in car-cass crude ash. This means that dietary supplemental ascorbic acid increases lipid metabolism by increasing lipid utilisation for energy and enhances pro-tein deposition in the body. Increased lipid utilisation by ascorbic acid may be explained in ascorbic acid and carnitine-related lipid metabolism. It is well documented that the synthesis of carnitine from lysine and methionine is of vital importance for the transport of fatty acids through mitochondrial membranes (e.g., Nelson, 1981). A reduction in this synthesis as occurs dur-ing ascorbic acid deficiency may reduce lipid utilisation, leaddur-ing to lipid accumulation.
These obtained results suggest that depressed feed intake and body weight gain by heat stress could be prevented by wet feeding up to a certain extent but at the expense of the reduction in feed conversion efficiency. However, under practical conditions, application of wet feeding is not an easy task, especially on a large scale intensive production. Firstly, it requires an auto-mated mixing and delivery system, and secondly it needs greater attention to control microbial growth, especially at high temperatures. Additionally, the mortality associated to wet feeding suggest that too rapid rates of growth pre-dispose chicks to leg weakness and heart disease and following wet feeding could also lead to increases in health and welfare problems by encouraging more rapid growth.
However, in the case of ascorbic acid supplementation of broiler diets under heat stress conditions, broilers receive physiological support against heat stress and they perform better, in the present trial with increases of 5% in BWG, 3% in feed intake and 2% in feed conversion efficiency. Although
ascorbic acid was ineffective when added to wet diets, its addition to dry feeds seems to be of practical relevance in the present rearing conditions for broilers.
In conclusion, wet feeding, especially at 150% water addition level or with a diet of porridge-like consistency, improved growth performance by increas-ing fat and protein deposition in the body, while reducincreas-ing feed conversion efficiency. It is also concluded that supplemental ascorbic acid (250mg/kg) in air-dry feeds stimulates broiler performance at high temperatures.
Acknowledgements
The author is grateful to Mr. Ö. Yiicelt of Roche Must. A. §. for gifts of coated ascorbic acid and to Mrs. H. Özdemir for technical assistance.
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