Effect of dietary supplementation of energy and protein on production performance and egg quality of scavenging crossbred hens in rural areas under tropical conditions

M M Rashid***, M N Islam**, B C Roy***, K Jakobsen* and C Lauridsen*

*Department of Animal Nutrition and Physiology, Danish Institute of Agricultural Sciences, Research Centre Foulum,
8830 Tjele, Denmark
charlotte.lauridsen@agrsci.dk
**Bangladesh Livestock Research Institute, Savar, Dhaka, Bangladesh,
***Department of Livestock Services, Krishi Khamar Sharak, Farmgate, Dhaka, Bangladesh

Abstract

An on-farm experiment was conducted in rural areas of Bangladesh for a period of 16 weeks to assess the effect of supplementing two energy levels (2900 and 2500 kcal ME/kg diet), each at two protein levels (19 and 15%) with 60 g feed daily on production performance and egg quality of scavenging hens. In addition, the performance of hens under fully scavenging was compared to supplementary feed condition. Ninety crossbred Sonali (Rhode Island Red x Fayoumi) hens of 26 weeks were distributed among 18 farmers with 5 birds each, referring each bird to each of 5 groups: Group 1 (2900 kcal/kg and 19% CP); Group 2 (2900 kcal/kg and 15% CP); Group 3 (2500 kcal/kg and 19% CP); Group 4 (2500 kcal/kg and 15% CP), and Group 5 (fully scavenging without feed supplementation).

Feed supplementation significantly (P<0.01) improved body weight gain, egg production, egg weight, egg mass output and shell thickness compared to no feed supplementation. Hen-house egg production was 39.3, 35.9, 38.4, 35.2 and 24.3% for groups 1, 2, 3, 4 and 5, respectively.

Chemical analysis of the feed mixtures showed that the energy content of the high energy experimental diets was 5-7 % lower than stipulated, and expressed in terms of energy, the protein content was 183, 140, 194, and 144 g/10 MJ ME of Groups 1, 2, 3, and 4, respectively. The high protein level (Group 1 and 3) significantly (P<0.01) increased hen-house egg production, egg weight, egg mass, feed efficiency and shape index (P<0.05), but depressed shell thickness (P<0.05) compared to low protein level (Group 2 and 4). The birds fed the diet with the stipulated high energy levels (Group 1 and 2) had a significantly improved egg weight (P<0.01) and shape index (P<0.05) compared to birds in Groups 3 and 4.

Key words: egg quality, energy, hens, production, protein, scavenging

Introduction

Bangladesh has been endeavouring to boost up its chicken meat and egg production in order to meet the increasing "protein gap" in human food. The efforts have been made through improvement of the scavenging poultry production system, and introduction of exotic breeds and their crossbred chickens in this system. Identification of suitable breeds or breed combinations for sustainable production in this rural environment has been studied for many years (Rahman et al 1997; Rahman et al 1998; Akhtar-uz-Zaman 2002). In addition, several studies (Rahman et al 1997; Rahman et al 1998; Islam et al 1992; Akhtar-uz-Zaman 2002; Ali 2002) have shown that in order for the exotic breeds and their crossbreds in the scavenging production system to fully express their genetic potentiality, the birds need feed supplementation. Ali (2002) studied the effect of increasing amounts of feed supplementation (0, 30, 60, 120 g) of a diet containing 16% CP and 2700 kcal/kg energy on the production rate of scavenging crossbred hens, and found that 60 g of feed improved hen house egg production (32.8%) significantly compared to 30 g of feed and no feed supplementation with 21.2% and 20.2% hen house egg production, respectively. Except for the amount of feed, the level of protein and energy, being major components in a diet, influences the production performance of the hens. However, very little information is available on the influence of nutrient composition such as energy and protein concentration in supplementary diets on the production performance and egg quality of scavenging hens under rural conditions in Bangladesh. Thus, the present study was carried out to investigate the effect of varying energy and protein level in the supplementary diet (60 g/day) on production performance and egg quality of scavenging crossbred hens.

Materials and methods

The experiment was conducted for a period of 20 weeks among rural farmers located in the northern part of Bangladesh. The selection of farmers was based on equal economic status and on nearly uniform scavenging area for the birds.

Experimental birds and housing

A total of 90 Sonali (crossbred of ♂ Rhode Island Red x ♀ Fayoumi) hens aged 26 weeks were used for the present study. The hens were randomly distributed among 18 farmers with 5 birds each, referring one bird at random to each of 5 treatment groups. Vaccination against Newcastle disease was done before the distribution of birds.

A shelter made of bamboo divided into 5 coops of equal size (36 cm x 76 cm) was placed at each farmer's house to accommodate the five experimental birds. Each coop was equipped with a clay feeder and a plastic drinker. The climatic season (from November to February) covered by the experimental period was winter with temperature range from minimum 7 to13^oC to maximum of 24 to 31^oC, and with high humidity (75 to 86%). The birds were given a 4-week adaptation period with a reduced amount of layer diet to be gradually acquainted with the rural environment and  level of feed supplementation.

Dietary treatments

The four experimental diets consisted of two levels of energy (2900 and 2500 kcal ME/kg diet) and two levels of protein (19 and 15% CP). Group 1 was the combination of 2900 kcal ME and 19% CP, group 2 the combination of 2900 kcal ME and 15% CP, group 3 the combination of 2500 kcal ME and 19% CP, and group 4 the combination of 2500 kcal ME and 15% CP. In addition to the four groups, a fifth group was included, which was fully scavenging without feed supplementation.

Formulation of diets and chemical analysis

Experimental diets were based on ingredients as presented in Table 1. The proximate components of maize, soybean meal, rice polishings and wheat bran were analysed in accordance with AOAC (1990) at the Department of Livestock Services, Dhaka, Bangladesh. Calcium and phosphorus of the ingredients and of dicalcium phosphate and oyster shell were determined by atomic absorption and spectrophotometry, respectively (FAO 1980). Based on the given nutrient values of the presented feed items (Table 1), experimental diets were formulated to obtain the planned combinations of energy and protein level.

The ingredient composition of the four formulated experimental diets is shown in Table 2.

The chemical analysis of the four mixed diets was performed at the Department of Animal Nutrition and Physiology, Danish Institute of Agricultural Sciences, Denmark. The following analyses were made: DM content by oven drying at 100^oC for 20 hours, protein (N x 6.25) by a modified Kjeldahl method (KjellFoss 16200 Autoanalyser; Foss Electric A/S, Denmark). Ash was analysed according to AOAC (1990), and fat was extracted with diethyl ether after acid hydrolysis (Stoldt 1952). Starch and sugar were analysed according to Bach Knudsen et al (1993).

Feeding and management

Sixty grams of the experimental diets were divided into two portions and fed to the assigned birds. The first time, at 6.30 a.m., the birds were moved from the night shelter to the coops and offered 30 g feed and were kept confined until 10.00 a.m. The second time, at 4.00 p.m., the birds were collected again and offered the remaining 30 g of feed and transferred to the night shelter at 6.00 p.m. Between the confinement periods, the birds were allowed to scavenge. There was a continuous supply of drinking water in the coops, which were easily accessible during the day when the birds were scavenging. Birds of group 5 were released at 6.00 a.m. and housed again at 18.00 p.m., but had free access to their coops during the day. De-worming of the birds was performed every two months during the experimental period.

Data recording

Production performance and egg quality responses were obtained during a period of 16 weeks (from 31 to 46 weeks of age), and this period was divided into four 4-weekly periods.

Production parameters

Body weight of the birds was obtained at the beginning and end of the experiment (at 31 and 46 weeks of age, respectively). Total body weight gain was calculated by subtracting the initial body weight from the body weight obtained at the end of the study. Egg production and individual egg weight were obtained daily, and mortality was recorded as it occurred. Hen-house egg production (%), daily egg mass (g/hen/day), total egg number/hen and feed efficiency of supplemented diets in terms of egg mass production was also calculated.

Egg quality characteristics

Evaluation of egg quality was performed using the first egg from each hen laid during the fourth week of each period. The eggs were broken in the evening of the respective day of lay. Following this procedure, a total of 360 eggs, 90 in each period, were subjected to measurement of shell weight, shell thickness and internal qualities: albumen height, yolk height, yolk diameter, fresh yolk weight and yolk colour. Yolk weight was taken according to Chowdhury (1988). The albumen weight was determined by subtracting the yolk plus shell weight from the total egg weight. The shell weight was determined instantly after removing the shell membranes from the shell. Shell thickness and yolk colour were measured by a digital micrometer (Mitutoy, Tokyo, Japan) and the Roche Colour Fan (RYC, F. Hoffman-La Roche), respectively. Fifty eggs were randomly taken from the pooled eggs of each treatment group during the 4^th period of the experiment irrespectively of farmers, to determine the shape index, which was calculated dividing the egg width by the egg length. Yolk index and haugh unit were calculated according to Wesley and Staldelman (1959), and Haugh (1937), respectively.

Statistical analysis

The following models were used:

A) Y_ijk= m + D_i + F_j + E_ijk
B) Y_ik = m + D_i + E_ik           
                  C) Y_ijk= m + C_i + P_j + (CP)_ij + E_ijk

Where:
            Y_ijk (A)= the k^th observation in i^th diet and jth farmer,
            Y_ik (B)= the k^th observation in i^th diet, and
            Y_ijk (C)= the k^th observation in i^th energy level and j^th protein level.

In the models:
             m = the general mean,
             D_i = the effect of the i^th diet group,
             F_j = the effect of the j^th farmer,
             C_i = the effect of the i^th energy level,
             P_j = the effect of the j^th protein level,
             (CP)_ij = the interaction effect between i^th energy and j^th protein level and
             E_ijk or E_ik = residual effect associating to Y_ijk or Y_ik.

Model A was used to compare the effect of dietary treatments on production performance and egg quality variables. Model B was considered for the shape index of eggs, and model C was used to evaluate the energy and protein levels in diets (excluding group 5). Descriptive analysis was performed using mean and standard deviation for each outcome variable. The analysis of all data was performed using General Linear Models (GLM) procedure  with SAS software (SAS 1999). Duncan's multiple-range test was used to compare treatment means (Steel and Torrie 1980).

Results

Table 3 shows the chemical analysis of the mixed diets used in this study. Protein levels in feed mixtures were consistent with the planned levels, although 1% higher for the stipulated low levels, and 5 to 8% higher for the stipulated high levels. However, energy content showed discrepancy with the expected level of diets; particularly in the high energy diets (groups 1 and 2), where the energy content was 5 to 7% lower than the planned level. When the protein content was expressed per 10 MJ energy, the feed mixtures contained 183, 140, 194, and 144 g protein/10 MJ for groups 1, 2, 3, and 4, respectively.

No mortality among the hens occurred, and no sign of (severe) disease was seen during the experimental period. Table 4 illustrates the production performance of hens. The hens under fully scavenging had significantly lower performance compared to the birds fed supplementary diets. The birds in groups 1 to 4 gained similar body weight during the study period. However, with regard to egg performance, hens of group 1 and 3 had the highest performance, which differed significantly from the performance of groups 2 and 4. With regard to feed conversion, group 1 showed a significantly better performance compared to all other groups, and group 3 had a significantly improved feed efficiency compared to groups 2 and 4.

Table 5 illustrates the egg quality characteristics of the groups during the experimental period. The shell thickness and yolk index of the eggs were significantly lower in fully scavenging birds compared to birds fed with supplementary diets, and other variables did not vary between the two groups of birds, although fully scavenging birds tended to produce eggs with higher yolk colour score. Shell percentage, shell thickness, albumen quality, yolk colour score and yolk weight did not differ significantly among groups 1 to 4. The birds in group 1 laid eggs with higher shape index number compared to the birds of groups 2, 3 or 4. The yolk index for groups 1, 3 and 4 did not differ, but group 2 showed depressed yolk index compared to groups 1 and 4.

The analysed protein content per 10 MJ energy was similar in groups 2 and 4 (low protein level, 140 to 144 g protein/10 MJ), and in groups 1 and 3 (high protein level, 183 to 194 g protein/10 MJ), and Table 6 therefore shows the effect of the two dietary levels of protein on production performance and egg quality. Birds fed the high protein diets showed significantly improved production traits compared to birds fed the low protein diets except for the body weight gain, which was similar. High protein level in the diets significantly decreased shell thickness and conversely, increased shape index number, but other egg quality traits did not differ significantly between the two protein levels.

By analysis of the effect of the stipulated dietary energy level on the performance and egg quality, only egg weight (45.1 g vs. 44.6 g, P<0.001) and shape index (0.766 vs. 0.756, P=0.027) was higher in birds fed the stipulated 2900 kcal/kg diet than in birds fed the 2500 kcal/kg diet, respectively.

Discussion

The calculated energy concentration (AMEn) obtained by chemical analysis of the nutrient content (Table 3) in diets 1 and 2 (average 2720 kcal) was lower than the stipulated (2900 kcal), and the calculated (2908 kcal, Table 2) energy content. Improper mixing of the oil with other ingredients may be the reason for this discrepancy. Higher presence of soybean meal in samples due to bigger particle size could be the reason for the generally slightly higher protein in the analysed feed samples (Table 3).

The present results clearly showed that feed supplementation significantly improved production performance of hens compared to without feed supplementation. The average egg production of the supplemented feed groups and the fully scavenging group was 37.2 and 24.3%, respectively, and this difference was consistent with the results of Ali (2002). In the latter study, increasing amounts of feed supplementation (0, 30, 60, 120 g) of a diet containing 16% CP and 2700 kcal/kg energy were studied for similar genotype hens as used in the present study. Ali (2002) concluded that 60 g of feed improved egg production (32.8%) significantly compared to 30 g of feed and no feed supplementation with 21.2% and 20.2%, respectively, and therefore it was decided to use an amount of 60 g of feed in the present study. The slightly higher egg production obtained in the present study could be due to the variation of scavenging feed availability in the locality, as well as to the difference in age of the birds.

Previous studies have also shown beneficial effects of feed supplementation with regard to performance of birds. Dessie and Ogle (1997), Demeke (1996), Smith (2001) and Sonaiya et al (2002) reported significantly increased egg production by indigenous birds provided different amounts of supplementary feed, when compared with the fully scavenging indigenous birds. In addition, positive effects of feed supplementation on egg weight were observed in previous research (Ali 2002; Akhtar-uz-Zaman 2002; Dessie and Ogle 1997). Akhtar-uz-Zaman (2002) reported that egg quality did not vary among three levels (15, 30 and 45 g) of feed supplementation, which complied with the present study as only minor influence of feed supplementation was observed with regard to egg quality. The reduced shell thickness in full scavenging group may be due to deficiency of Ca and P in scavenged food, which is corroborated by the crop content analysis of scavenging laying hens collected from the same area (Rashid 2003).

As the feed analysis showed no difference between stipulated high and low dietary energy levels, it was not surprising to find no effect of dietary energy on measured performance and egg quality in the present study. It was, therefore, not possible to conclude if energy or protein was the major limiting nutrient in the diet for the scavenging birds. However, analysing crop contents of scavenging laying hens from the same area in another trial, Rashid (2003) reported that scavenging feed resources are found to be much lower in protein (11.4%) and slightly lower in energy (2776 kcal ME/kg DM) relative to the requirements according to NRC (1994). On the contrary, Dessie and Ogle (1997) reported from a study in Ethiopia that indigenous hens receiving daily allowances of 2.49 g CP and 111 kcal, 10.1 g CP and 55 kcal, and 10.1 g CP and 157 kcal per day as supplementation,  produced eggs at a rate of 25, 20 and 30%, respectively, and it was concluded that energy rather than protein was the major limiting nutrient in the diet of scavenging hens, although high protein consumption significantly increased the egg weight. Baset et al (2000) obtained no significant difference in weight gain and egg production (39.3% vs. 42.1%) between two groups of Fayoumi hens in rural areas of Bangladesh, which were offered 122 kcal and 8.7 g CP through 51 g diet/day, and 155 kcal and 11.1 g CP through 65 g diet/day.

The present study showed that birds receiving 19% CP laid 3.44% more eggs compared to birds receiving 15% CP (Table 6), and that increasing the dietary protein level also improved the egg weight and the feed conversion of the birds. In other words, hens on low protein diets could not manage to find enough protein from scavenging sources to perform equally to hens on high protein diets receiving 2.4 g more protein daily. Thus, from the overall results, it may be concluded that high protein level (190 g/10 MJ) in a supplementary diet could be recommended for a viable production of crossbred hens under rural conditions. However, since protein-rich feeds are expensive, future research should focus on the possibility of using cheap conventional and non-conventional protein-rich feed resources as feed supplement for scavenging chicken in rural areas in developing countries.

Acknowledgements

The study was financially supported by the Danish International Development Agency (DANIDA) through the Network for Smallholder Poultry Development with a MSc. grant for the first author. The authors wish to express their gratitude to Dr. Guosheg Su (Department of Animal Breeding and Genetics, Danish Institute of Agricultural Sciences) for his help regarding statistical analysis of data.

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