EFFECT OF DIETARY ENERGY LEVEL ON PERFORMANCE AND CARCASS QUALITY OF BROILER CHICKS

Faculty of Agriculture, Omdurman Islamic University

P.O. Box 382, Sudan

Effect of diEtary energy level on Performance and Carcass Quality of Broiler Chicks

(With 8 Tables)

By

Safa M.A. El Tazi

(Received at 18/10/2009)

SUMMARY

The effect of various metabolizable energy level on performance and carcass quality of broiler chicks were studied. A total of one hundred and fifty one-day old, unsexed (Ross) broiler chicks were randomly divided into five experimental groups. Each group was further subdivided into five replicates at the rate of six chicks per pen in complete randomized design. The birds were fed on five levels of metablizable energy (2827, 2972, 3085, 3162 and 3210 Kcal/kg) with constant level of dietary protein (22%) for 7 weeks duration. Health of the stock and performance parameters were recorded. At the end of the experiment, the birds were slaughtered, dressing, and used for different parameters. The results indicated that the energy level had significant (P<0.01) effect on performance and carcass quality of broiler chicks. Birds fed the highest energy diet (3210 Kcal/kg) showed better results in body weight gain, feed efficiency and dressing percentage with the lowest feed intake as compared to the other experimental diets. The birds fed the highest energy diet (3210 kg/kg) had significantly (P<0.01) highest carcass fat content and abdominal fat percentage as compared to the other diets.

Key words: Brioler chicks, carcase quality, feed, metabolizable energy.

Introduction

            The broiler chicks are known to be precisely demanding for essential nutrients in their diets, in order to express their genetic potentials for optimum production. Of these nutrients requirement, energy which constitutes the major entity, as it is required in larger quantities than the other nutrients and it also influences voluntary feed intake and is much related to protein, amino acids and other dietary nutrients consumption and utilization. In addition to, energy constitutes the major cost item in formulation of adequate least-cost diet for broilers and hence would affect the economic efficiency of production. However, limited local research has been conducted to determine the adequate level of dietary metabolizable energy for feeding broiler chicks under open housing system in Sudan (El-Tazi, 2001).

This study was intended to gain more information about the effect of various levels of dietary metabolizable energy on broiler performance and carcass quality in Sudan.

Materials and Methods

            A total of 150 one-day old unsexed (Ross) chicks were randomly distributed into 5 groups of 30 chicks. Each group was further subdivided into 5 replicates with 6 chicks per each. The chicks of each replicate were housed in a pen (1 square meter) in an open-sided deep litter house. Five levels of metabolizable energy (2827, 2972, 3085, 3162 and 3210 Kcal/kg) with constant dietary protein level (22%) were fed during the experimental period for 7 weeks duration. All the experimental diets were formulated to meet the nutrient requirements of boiler chicks according to (NRC, 1994) which was formulated from the local feed ingredients commonly used for poultry feeding in the Sudan. Calculated analysis of the experimental diets was done according to feedstuff analysis outlined by Ellis (1981) while determined chemical analysis was conducted by the methods of AOAC (1988). Formulation and chemical composition of the experimental diets are shown in Tables (1 and 2), while the chemical composition of the super concentrate used in diets is shown in Table (3). Feed and water were offered ad-libitum. The light was continuous throughout of the experimental period. The performance of the experimental birds in term of feed intake, live weight gain and feed efficiency were recorded weekly. Health of the experimental stock and mortality rate were closely observed and recorded daily.

Table 1: Formulation and chemical composition of the experimental diets (percent as fed)

Table 2: Chemical composition of the experimental diets (percent as fed)

Table 3: Energy and chemical composition of the super concentrate used in diet formulation (Hendrix broiler concentrate)

            At the end of 7^th week, the birds were individually weighed after overnight fast (except for water) and slaughtered without stunning. They were then scalded, manually plucked, washed and allowed to drain on wooden tables. Evisceration was performed by a ventral cut and visceral as well as thoracic organs were removed. After evisceration internal organ, head and shanks were removed, weighed individually and expressed as percentage of slaughtered weight. Eviscerated carcasses were weighed and then chilled in a refrigerator for 24 hours at 4^oC. Cold carcasses were recorded.

            All the slaughtered birds were used for dissection. The breast, thigh and drumstick of the left side of each carcass were dislocated, weighed and expressed as percentage of cold carcass weight. After that, the breast and thigh of each carcass were deboned and minced twice and then kept frozen for determination of their chemical composition. Statistical analyses were made by analysis of variance for a completely randomized design, according to Stell and Torrie (1986).

Results

            The effect of various energy levels on broiler's performance is shown in Table (4). The body weight gain and feed conversion ratio were improved significantly (P<0.01) as the level of energy was increased, while the total feed intake tended to decreased significantly (P<0.01) with increasing the level of energy. The diet with the highest level of energy (3210Kcal/kg) showed significantly (P<0.01) highest body weight gain and best feed conversion ratio with the lowest feed intake as compared to the other experimental diets.

Table 4: Effect of various energy levels on the performance of broiler chicks

    SEM:  Standard error of the means

    ** :     Highly significant (P<0.01)

    Means within each treatment row of the same superscripts are not significant  different (P>0.05).

            With regard to NRC (1994) it can be noticed that, all the experimental diets stimulated adequate nutrient intake at all levels of energy (Table 5).

Table 5: Feed and nutrient intake of the experimental diets (g/chick)

            Table (6) shows the effect of dietary energy level on carcass characteristic of the broilers. There was no significant difference (P>0.05) in all the parameters measure except the hot and cold eviscerated carcass weights. Birds fed diet with the highest level of energy (3210 Kcal/kg) gave significantly (P<0.01) heavier hot and cold eviscerated carcass weights, while those fed diet with the lowest level of energy (2827 Kcal/kg) gave the lightest values

Table 6: Means-values for the dressing carcass percentage and commercial cuts of broiler carcasses

SEM:      Standard error of the means

** :         Highly significant (P<0.01)

NS:         Means not significant (P>0.05).

            Table (7) shows the effect of various energy levels on the non-carcass components as a percentage of body weight. There was no significant difference (P>0.05) in the percentage of total viscera, liver, heart, gizzard and head and shanks except the abdominal fat percentage. Birds fed diet with highest energy level (3210 Kcal/kg) gave significantly (P<0.01) the highest abdominal fat percentage while those fed diet with the lowest energy level (2827 Kcal/kg) gave the lowest of these values.

Table 7: Body weight and organ proportions of broiler chickens

  SEM:    Standard error of the means

  ** :       Highly significant (P<0.01)

  NS:       Means not significant (P>0.05).

            Table (8) shows the effect of various energy levels on the chemical composition of breast and thigh muscles of broilers. There was no significant difference (P>0.05) in the percentages of protein, ash and moisture for both breast and thigh muscles of the broiler among the experimental treatments except the fat percentage for both breast and thigh muscles. Birds fed diet with the highest energy level (3210 Kcal/kg) produced significantly (P<0.01) highest carcass fat percentage while those fed diet with the lowest energy level (2827 Kcal/kg) produced the lowest values.  

Table 8: Chemical composition of breast and thigh muscles of broiler chicks

    SEM:  Standard error of the means

    ** :     Highly significant (P<0.01)

    Means within each treatment row of the same superscripts are not significant different (P>0.05)

    NS:     Means not significant (P>0.05).

            The experimental treatments had no significant (P>0.05) effect on the mortality rate. Only one bird from each treatment died, which cannot be related in any way to the experimental treatments.

Discussion

            The effect of feeding various levels of metabolizable energy on the productive performance of broiler is shown in Table (4). Treatment effect on body weight gain, fed intake and fed efficiency was highly significant (P<0.01). Birds fed diet contained 3210 Kcal/kg metabolizable energy produced significantly (P<0.01) the heaviest body weight gain and the lowest feed consumption with the best feed utilization efficiency as compared to other experimental diets. The experimental birds tended to adjust their feed intake according to the dietary energy level by eating less from the high energy diets. The highest body weight gain and the best feed utilization efficiency were attained by the diet containing the highest level of energy. These effects were consistent with the increased nutrients intake from the different experimental diets (Table 5). The experimental birds consumed progressively more energy from the higher energy diets, in spite of the general depressing effect of the dietary energy level on feed consumption. These results are agreement with those reported by Sadagopan et al., (1971); Salmon et al., (1983) and El-Tazi (2001). The result coincided with the finding of Proudfoot and Hulan (1987) who mentioned that the highest dietary energy (3100 Kcal/kg) gave the highest growth rate, the highest profit and the most efficient feed conversion as compared to the lowest energy diet (2900 Kcal/kg). Similar results have been obtained by Bertechini et al., (1991) who stated that, there was a linear increase in weight gain and a decrease in feed intake as the energy intake was increased.

            As shown in Table (6), the dressing percentages on hot and cold carcass base were highly significantly (P<0.01) increased with increasing energy level. These results are consistent with the differences in growth rate and the subsequent final live weight on the different experimental diets. Similar results have been obtained by Preston and William (1973) who indicated that heavier birds at slaughter would have greater dressing percentage and higher eviscerated yield than lighter birds. These results were in line with the findings of El-Tazi et al., (1990) who mentioned that, the increased eviscerated yield obtained from birds that were fed free choice method with unground grains might be due to the heavier slaughter weight.

            As shown in Table (7), the percentage of abdominal fat was increased significantly (P<0.01) with increasing the level of energy. Birds fed diet that contained 3210 Kcal/kg produced the highest percentage of abdominal fat while birds fed diet contained 2827 Kcal/kg produced the lowest percentage values. Thee results are in agreement with those reported by Salmon et al., (1983) and El-Tazi, (2001). Similar results were obtained by Motozonon et al., (1998) who indicating that, abdominal fat of broilers would increase with increasing dietary energy concentration. This dietary effects on abdominal fat deposition are basically associated with the utilization efficiency of nutrients for energy production and lipogensis.

            As shown in Table (8), the chemical composition of the breast and thigh muscles confirms the effect of increasing the energy level which increasing the fat content of the carcasses. Birds fed diet contained 3210 Kcal/kg metabolizable energy produced the highest carcass fat content while those fed diet contained 2827 Kcal/kg energy gave the lowest values. These results were in line with other findings Pesti and Fletcher (1983); Salmon and Torrie (1986) and El-Tazi (2001). Who reported that increased metabolizable energy level would result in an increased carcass fat deposition.

References

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