Effect of time of initiation of feeding after hatching and influence of dietary lysine supplementation on productivity and carcass characteristics of Ross 308 broiler chickens in South Africa

C A Mbajiorgu, J W Ng’ambi and D Norris

Department of Animal Production, University of Limpopo, P Bag X1106, Sovenga 0727, South Africa

anayochukwumbajiorgu@gmail.com

Abstract

An experiment was conducted to evaluate the effect of time of initiation of feeding after hatching and influence of dietary lysine supplementation during realimentation on productivity, carcass characteristics and mortality of Ross 308 broiler chickens. The study was a factorial arrangement in a complete randomized design. Three hundred and sixty unsexed day old Ross 308 broiler chicks with an initial weight of 30 ± 2 g per bird were assigned to 12 treatments in a 4 (times of initiation of feeding) x 3 (lysine supplemental levels) factorial arrangement with three replications, each having ten birds. The experimental diets were isocaloric and isonitrogenous but with different lysine supplementation levels. Lysine supplementation started three days after hatching.

Lysine supplementation during realimentation only reduced the number of days of ‘catch-up’ irrespective of time of initiation of feeding after hatching and thereafter had no effect (P>0.05) on productivity and mortality of the birds. However, the birds ‘caught-up’ within eight days of realimentation. This compensatory growth could be explained in terms of higher intakes. Generally, more than 50 % of the birds died between 1 and 3 days of age when initiation of feeding after hatching was above 36 hours.

It is concluded that time of initiation of feeding above 36 hours after hatching is not desirable, mainly because of its negative effect on mortality. Beneficial effect of lysine supplementation in the diet of broiler chickens subjected to delayed initiation of feeding after hatching could be exploited in accelerating the rate of ‘catch-up’ growth response.

Keywords: Growth rate, lysine supplementation, time of initiation of feeding

Introduction

Broiler chicken production plays a major role in food security for the rapidly growing South African human population (Sonaiya 1999). Their short production cycle, high feed efficiency and high biomass per unit of agricultural land are particularly attractive and have aroused a growing interest in South African agricultural production systems.      

Over the period 1957 to 2000, the age to slaughter and the amount of feed required to produce a given quantity of chicken meat have been more than halved due to genetic selection for fast growth and efficient feed utilization (Harvestein et al 1994). The main increase in growth rate is manifested primarily in the first four weeks after hatching (Marks 1979). However, in Limpopo province, farmers receive chicks late, sometimes two days or more after hatching. This leaves the residual yolk sac as the only source of nutrients for the chicks during this period (Dibner et al 1998). These authors also observed that during such a period the residual yolk sac nutrients are not always sufficient to satisfy the chick’s optimal metabolic nutrient requirements. This limits the chick’s growth, leading to poor productivity. Such initial starvation may also lead to poor digestive tract development and immune responses (Fanguy et al 1980). Thus, the effect of delayed initiation of feeding after hatching in Limpopo province and elsewhere requires further evaluation.

After hatching, the broiler chicks are exposed to environmental, pathological and nutritional stresses. Supplementation with exogenous nutrients such as lysine provides benefits to growing chicks (Plavnik and Hurwitz 1989). Jones and Farrell (1992) observed higher growth rates and leaner carcasses in previously feed-restricted birds supplemented with lysine in comparison to the non-restricted birds. However, there are other studies indicating no significant beneficial effects of lysine supplementation in previously feed-restricted birds compared to non-restricted ones (Acar et al 1991). It is, therefore, important to ascertain such responses in broiler chickens under different times of initiation of feeding after hatching. Such information would be very beneficial to poultry farmers in rural areas of Limpopo province and elsewhere

The main objective of this study was to determine the effect of delayed initiation of feeding after hatching and influence of dietary lysine supplementation during realimentation on productivity and carcass characteristics of Ross 308 broiler chickens.

 

Methodology

Study site

This study was conducted in 2006 in an open-sided house with curtains at the Experimental farm of the University of Limpopo, Limpopo Province, South Africa. The farm is located at about 10 km northwest of the University campus. The ambient temperatures around the study area are above 32 ⁰C during summer and around 25 ⁰C or lower during the winter season. The mean annual rainfall is between 446.8 and 468.4 mm.

Birds, treatments, design and data collection

Day old Ross 308 broiler chicks were used in the study. They were purchased from South Africa Chicks Hatchery in Pretoria. On arrival, 360 unsexed day old Ross 308 broiler chicks were allocated to 12 treatments (Table 1) with three replications in a 4(initiation of feeding after hatching) x 3(supplemental lysine levels) factorial arrangement in a complete randomized design (SAS 2000).

Ten chicks were used in each replication. Lysine supplementation started 72 hours post-hatching. At each stage of the experiment, diets were isocaloric and isonitrogenous except for lysine and time of initiation of feeding after hatching. The birds were offered feed and fresh water ad-libitum. The daily lighting program was 24 hours. The experiment was terminated when the birds were 42 days of age.

During the experiment, the initial average live weights of the chickens were taken at 24 hours old and every 12 hours thereafter until they were 72 hours old. Daily mean live weights and feed intake were measured until the end of the experiment. Daily growth rates and feed conversion ratio were calculated. Mortality was measured throughout the experiment. At Day 36, four birds were randomly selected from each replication and transferred to metabolic cages for measurement of apparent digestibility. At 42 days old, all remaining birds were slaughtered by cervical dislocation to determine the carcass characteristics.

Nutrient analysis

The dry matter, nitrogen, crude protein, phosphorus, fat and lysine contents were determined as described by AOAC (2000). The gross energy (GE) of the diets and excreta samples were determined using an adiabatic bomb calorimeter (University of Kwazulu-Natal Laboratory, South Africa). The apparent metabolizable energy (AME) content of the diets was calculated (AOAC 2000)

Data analysis

Effect of time of initiation of feeding after hatching and influence of dietary lysine supplementation on live weight, feed intake, feed conversion ratio, digestibility, carcass characteristics and mortality were analyzed using the General Linear Models (GLM) procedures of statistical analysis of variance (SAS 2000). Tukey test for multiple comparisons was used to test the significance of differences between treatment means (P<0.05) (SAS 2000). Regression analysis was used to determine the relationships between times of initiation of feeding after hatching, live weight and mortality responses of the broiler chickens (SAS 2000).
 

Results

The nutrient compositions of the starter and grower diets are presented in Table 2. The diets at each phase (i.e. starter and grower phases) were isocaloric and isonitrogenous but with different levels of lysine supplementation. Levels of other nutrients of the diets were similar.

 Results of the effect of time of initiation of feeding after hatching on live weight and feed intake at three days old, and mortality of Ross 308 broiler chickens between one and three days of age are presented in Table 3.  

Time of initiation of feeding after hatching had effect (P<0.05) on live weight and feed intake at 3 days of age and mortality of Ross 308 broiler chickens between 1 and 3 days old. Broiler chickens on initiation of feeding within 1 to 24 hours and those within 24 to 36 hours after hatching weighed and ate more (P<0.05) than those on initiation of feeding within 36 to 48 hours and those within 48 to 60 hours after hatching. Mortality was also lower (P<0.05) in broiler chickens on initiation of feeding within 36 hours after hatching than those on initiation of feeding above 36 hours after hatching. However, broiler chickens on initiation of feeding within 36 to 48 hours and those within 48 to 60 hours after hatching had similar (P>0.05) live weight and feed intake at three days of age, and similar (P>0.05) mortality between one and three days of age. Similarly,  chickens on initiation of feeding within 1 to 24 hours and those within 24 to 36 hours after hatching had similar (P>0.05) live weight and feed intake at three days of age, and similar (P>0.05) mortality between one and three days of age.

Table 4 presents a series of linear regressions that predict mortality and live weight of Ross 308 broiler chickens at 3 days after hatching.  Mortality was positively and strongly correlated (r = 0.92) with time of initiation of feeding after hatching. Live weight was negatively and strongly correlated (r = -0.91) with time of initiation of feeding after hatching. 

The effects of time of initiation of feeding after hatching and lysine supplementation during “catch up” period on intake per bird, intake as percentage of live weight and feed conversion ratio of Ross 308 broiler chickens following realimentation are presented in Table 5.  

Time of initiation of feeding after hatching and lysine supplementation during ‘catch-up’ period had effect (P<0.05) on intake per bird and intake as percentage of live weight of Ross 308 broiler chickens. Lysine supplementation during realimentation tended to reduce the number of days of ‘catch-up’. The overall ‘catch-up’ rate tended to be faster in those birds supplemented with 5 g lysine per kg feed, ‘catching-up’ at two days, followed by those supplemented with 2.5 g lysine per kg feed, ‘catching-up’ at three days, while those without lysine supplementation had a ‘catch-up’ period of five days. This trend was similar in all the birds irrespective of the time of initiation of feeding after hatching (Table 5 and Figures 1, 2 and 3).

Broiler chickens supplemented with 5 g lysine per kg feed had higher (P<0.05) feed intake as a percentage of live weight than those supplemented with 2.5 g lysine per kg feed and those fed without lysine supplementation. There were significant (P<0.05) differences in feed intake as a percentage of live weight between broiler chickens supplemented with 2.5 g lysine per kg feed and those fed without lysine supplementation. Time of initiation of feeding after hatching and lysine supplementation during ‘catch-up’ period had no effect (P>0.05) on feed conversion ratio of the chickens.

Time of initiation of feeding after hatching and lysine supplementation had no effect (P>0.05) on growth rate, feed intake, feed conversion ratio and mortality of Ross 308 broiler chickens between 3 and 21 days of age (Table 6).        

Similarly, lysine supplementation within each period of initiation of feeding after hatching had no effect (P>0.05) on live weight of the chickens up to 21 days of age (Figures 4, 5, 6 and 7). 

Time of initiation of feeding after hatching and lysine supplementation had no effect (P>0.05) on diet dry matter and nitrogen digestibilities, nitrogen retention and metabolisable energy in Ross 308 broiler chickens between 40 and 42 days of age. Metabolizable energy values of the different diets ranged between 15 and 16 MJ / kg DM (Table 7).  

Time of initiation of feeding after hatching and lysine supplementation had no effect (P>0.05) on live weight, dressing percentage, carcass parts and intestinal length of the chickens at 42 days old (Table 8). 

Metabolizable energy values of the different diets ranged between 15 and 16 MJ/kgDM. Similarly, time of initiation of feeding after hatching and lysine supplementation had no effect (P>0.05) on live weight, dressing percentage, carcass parts and intestinal length of the chickens at 42 days old.
 

Discussion

Times of initiation of feeding after hatching affected live weight at three days of age, feed intake and mortality of Ross 308 broiler chickens between one and three days of age. It was observed that initiation of feeding within 1 to 36 hours after hatching promoted good growth and feed intake in broiler chickens. Increasing time of initiation of feeding above 36 hours after hatching retarded live weight and reduced feed intake by the age of three days. These results are similar to the findings of Noy and Sklan (1998). However, these results are different from the findings of Dibner et al (1998) and Maiorka et al (2000) which indicated that initiation of feeding within 24 hours after hatching enhanced growth and feed intake, while increasing initiation of feeding above 24 hours after hatching retarded growth and reduced feed intake in broiler chickens. In explaining the reason for enhanced growth and improved feed intake following initiation of feeding within 36 hours after hatching, Noy and Sklan (1999) reported that immediately after hatching, most nutrients are used for maintenance activities and growth, specifically for intestinal growth. This preferential growth occurs regardless of initiation of feeding after hatching. When the nutrients are not supplied by exogenous feed, newly hatched chicks use the nutrients from the yolk sac for intestinal growth (Maiorka et al 2000). However, as observed by Dibner et al (1998), the maximum amount of nutrients produced by the york sac is less than the optimal maintenance requirements of the chick during the first day of life. Therefore, in order to achieve its optimal nutrient requirements for maintenance during this period, intake of nutrients from exogenous feed is necessary. Nitsan et al (1991) and Shehata and Skalan (1984) observed that intestinal growth immediate post-hatch is accompanied by increase in the production and activity of digestive enzymes such as amylase, trypsin and pancreatic lipase from intestinal membranes. However, Sell et al (1991) and Traber (1991) reported that these digestive enzymes are already in gastrointestinal tract during embryo phase but the presence of nutrients from oral intake of exogenous feed improves their activity. Therefore, birds fed immediately after hatching have a constant secretion of these enzymes resulting in higher trypsin, amylase and lipase activities in intestinal mucosa, which results in higher intestinal weight and body weight growth (Sklan and Noy 2000). Feeding immediately after hatching, therefore, seems to improve the activities of the digestive enzymes in the intestinal mucosa, increases digestion, and consequently enhances body growth and feed intake of broiler chickens. Feed restriction above 36 hours immediate post-hatch might have led to low enzymatic activity in the intestinal mucosa and hence a decrease in digestion. This might have led to lower growth rates. These results support the finding that residual york sac nutrients are optimally utilized for enhancing growth and intake where initiation of feeding after hatching is within 36 hours

Different times of initiation of feeding after hatching affected mortality rates in broiler chickens. More than 50% of the chicks died by the age of 60 hours when initiation of feeding was delayed to above 36 hours after hatching. This observation is similar to that of Dibner et al (1998). These authors explained that when initiation of feeding after hatching is longer than 24 hours, the chick degrades maternal immunoglobulins present in the vitelline residue to produce its own proteins necessary for survival. During this time of fasting, exogenous food and non-food particles, which constitute an important antigen battery, are not introduced to the chick. Thus, the diversity of the immunoglobulin pool produced is negatively affected and this tends to weaken the immune system of the bird. Furthermore, Lowenthal et al (1994) observed that lymphocytes of one day-old chicks, although apparently mature, are functionally immature at hatch and gradually acquire immune activity with the intake of exogenous nutrients. Similarly, Rose and Rogaush (1974), and Klasing (1998) indicated that lack of oral intake of exogenous nutrients during the first days of life may lead to the absence of a specific and well developed humoral response in the chick and this condition leads the chick to be very dependent on maternal antibodies, which might not satisfy the required immune needs of the bird within this period. Thus, intake of nutrients from exogenous feed are essential for the adequate development of the bird’s immune system after hatching. As a result, delayed initiation of feeding after hatching leads to high mortality rates. A critical time of initiation of feeding after hatching was found to be 36 hours in the present study.   The current study indicated that mortality was positively and strongly correlated with time of initiation of feeding after hatching while live weight at three days of age was negatively and strongly correlated with time of initiation of feeding after hatching. This is in agreement with the findings of Fanguy et al (1980) and Wyatt et al (1985) which indicated that delayed initiation of feeding post-hatch induces high mortality rate in broiler chickens due to its negative effect on immune organs which play a key role in enhancing immune competence.

After three days of age, mortality rates stabilized irrespective of time of initiation of feeding after hatching and lysine supplementation. It is possible that the reduction in mortality rate was as a result of intake of exogenous nutrients (Dibner et al 1998). Lysine supplementation during realimentation tended to reduce the number of days of ‘catch-up’ irrespective of time of initiation of feeding after hatching. The overall ‘catch-up’ period tended to be shorter in those birds supplemented with 5 g lysine per kg feed, ‘catching-up’ at two days, followed by those supplemented with 2.5 g lysine per kg feed, ‘catching-up’ at three days, while those without lysine supplementation had a ‘catch-up’ period of five days. Hays et al (1995) also observed that restricted steers realimented on diets of increasing protein levels (9, 12 or 15 % CP) showed a differential growth response to dietary protein in the first two weeks of realimentation. These authors suggested that the responsiveness to dietary protein in the realimentation diet was directly related to the severity of the restriction period. Thus, the more severe the restriction as measured by the depletion of protein stores, the greater the initial growth rates were on the higher protein diet. Although the present results showed existence of a differential growth response to dietary lysine supplementation, they do not support the idea that the more severe the restriction, as measured by the delayed time of initiation of feeding after hatching, the greater the initial growth rates. However, based on the shorter 'catch-up' period of broiler chickens on a diet supplemented with 5 g lysine per kg feed, it may be concluded that lower amounts of lysine in the realimentation diet may have been limiting optimal ‘catch-up’. Plavnik and Hurwitz (1989) also concluded that broiler chickens require higher amounts of lysine and methionine during realimentation. However, present results are contrary to the findings of Jones and Farrell (1992) who observed little or no response to lysine and methionine supplementation when fed from 4 to 7 weeks of age. In the present study, higher feed intake relative to the body weight seemed to have been the main reason for shorter ‘catch-up’ periods. Zubair and Leeson (1994) observed the same occurrence of significantly increased feed intake relative to body weight in restricted-refed broiler chickens. However, Carstens et al (1991) did not observe any differences in feed intake upon realimentation when steers were measured at similar body weight, even though the restricted steers showed higher growth rates when realimented. Yambayamba et al (1996) did not observe a significant increase in feed intake in restricted steers compared to the control steers at the same age. However, based on the available data from that trial, one could deduce that if feed intake had been measured as a percent of body weight, significant differences in feed intake would have been observed. In the present study, It was not possible to estimate the optimum level because of the short range of lysine supplementation levels used.  However, full recovery of body weight was at the latest by the age of 8 days. Thereafter, lysine supplementation had no effect on live weight, feed intake, growth rate, feed conversion ratio and carcass characteristics of the broiler chickens.

The results of the present study indicate that different times of initiation of feeding after hatching and dietary lysine supplementation had no significant effect on dry matter and nitrogen digestibilities, nitrogen retention, metabolisable energy, dressing percentage, carcass parts, intestinal length, and nitrogen content of Ross 308 broiler chickens during the grower phase. According to Acar et al (1991), lysine concentrations of 7.5 g to 11.5 g / kg diet has no effect on performance or carcass yield of broilers aged between six and eight weeks. However, in other studies, dietary lysine has been shown to impact on the performance of broilers, particularly with respect to breast meat accretion and yield (Corzo and Kidd 2004).

 

Conclusions

• The time from hatching to initiation of feeding is a critical period in the development of the broiler chickens. Time of initiation of feeding above 36 hours after hatching resulted in growth reduction. However, the birds ‘caught-up’ within 8 days of realimentation. This compensatory growth could be explained in terms of higher intakes. On the other hand, time of initiation of feeding above 36 hours after hatching resulted in high mortality rates. This is a big loss as overall productivity is adversely affected. Lysine supplementation during realimentation tended to reduce the number of days of ‘catch-up’ irrespective of time of initiation of feeding after hatching. Generally, the higher the level of lysine supplementation, the lower was the number of days of ‘catch-up’ upon realimentation. It is concluded that lysine supplementation in the diet of broiler chickens subjected to feed stress might play a key role in accelerating the rate of ‘catch-up’ growth response. However, time of initiation of feeding above 36 hours after hatching is not desirable, mainly because of its effect on mortality.    

  
  

• Time of initiation of feeding after hatching and dietary lysine supplementation had no significant effect on dry matter and nitrogen digestibilities, nitrogen retention, metabolisable energy, dressing percentage, carcass parts, intestinal length, and nitrogen content of Ross 308 broiler chickens during the grower phase. This, possibly, may indicate that the level of dietary lysine used in the present study were equal or above the optimum requirements for these parameters. 
   

Acknowledgements

The authors wish to acknowledge the National Research Foundation (NRF) for financial support.
 

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Received 4 July 2007; Accepted 7 July 2007; Published 4 October 2007

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