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J APPL POULT RES 2008. 17:1-10. doi:10.3382/japr.2006-00053
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Research Reports

Effect of Molting Method and Dietary Energy on Postmolt Performance of Two Strains of Single Comb White Leghorn Hens

G. Wu, P. Gunawardana, M. Bryant, R. Voitle and D. Roland1

Department of Poultry Science, Auburn University, Auburn, AL 36849

1 Corresponding author: roland1{at}auburn.edu


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
This experiment was a 4 x 2 x 2 factorial arrangement of 4 dietary energy levels (2,767, 2,806, 2,846, and 2,886 kcal of ME/kg), 2 molting methods (feed withdrawal and the low-salt diet), and 2 strains (Bovans White and Dekalb White). The objective of this study was to determine the effect of dietary energy and molting method on postmolt performance of 2 strains of commercial White Leghorns. Before the molt, Bovans and Dekalb hens were randomly divided into 2 groups. Feed was withdrawn from half of the hens (66 wk of age) for 9 d. A molt feed was fed from d 10 to 28. The other half of the hens was fed a low-salt diet for 28 d. After the molt, Bovans White hens (n = 720) and Dekalb White hens (n = 720) at 70 wk of age were randomly divided into 16 treatments (6 replicates of 15 birds per treatment). Bovans hens had significantly lower egg weight, percent of eggshell, egg specific gravity, and Haugh units than Dekalb hens, whereas Bovans hens had significantly higher egg production than Dekalb hens. Increasing dietary energy had no significant effect on any parameter other than yolk color. As dietary energy increased, feed conversion improved numerically from 2.13 to 2.05, resulting in a 3.8% improvement of feed conversion. With increasing dietary energy, hens adjusted feed intake, according to egg mass, to achieve the quantities of dietary energy (5.8 to 5.9 kcal) intake per gram of egg. An ideal dietary energy level for optimal postmolt performance and profits could not be determined for hens during phase 1 of the second cycle. Other than slightly reduced egg production and egg specific gravity during phase 1, feeding the low-salt diet to induce molt could be used as an alternative for the conventional feed withdrawal method.

Key Words: strain • dietary energy • molting method


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Induced molting has been widely used to revive the productivity of aged laying hens by the egg industry in the United States for 40 yr. Induced molting increased egg production, renewed feather growth, and improved egg quality including egg specific gravity and shell thickness [1–3]. Induced molting not only improves performance, but also extends the economically useful life of laying hens from 80 to 110 wk or even to 140 wk of age, which reduces the number of replacement pullets needed. Feed withdrawal with light reduction is widely used to induce molting. In recent years, induced molting by conventional feed withdrawal has been vigorously criticized by animal welfare groups. The United Egg Producers (UEP) Scientific Advisory Committee on Animal Welfare urged researchers and producers to work together to develop molting methods other than feed withdrawal [4].

Effectiveness of several nonfeed removal molting diets including low-sodium diets [5–15], low-calcium diets [16], high-zinc diets [17–19], and low-protein and low-energy diets [20, 21] have been evaluated. Naber et al. [14] and Said et al. [15] reported that low-sodium diets can be effective in recycling hens for a second period of egg production. However, hens molted using low-salt diets had decreased egg production and eggshell thickness during postmolt egg production [11] compared with the conventional feed withdrawal program. Different strains showed performance differences after the molt, compared with the conventional feed withdrawal [15, 22]. In addition, there is little or no research concerning the effects of the low-salt diets on egg composition and egg solids, which are important factors influencing profits in the breaker egg market. Therefore, it is necessary to have more knowledge concerning the effect of the low-salt diets on performance, egg quality, egg components, and egg solids in current strains of commercial Leghorns to determine acceptable alternatives for conventional feed withdrawal methods.

Increasing dietary energy by the addition of poultry oil or corn oil had significant effects on feed intake [23–27], egg weight [24, 28–31], feed conversion [25, 26], and egg specific gravity [25]. However, Summers and Leeson [32] and Jalal et al. [33] reported that dietary energy had no effect on feed intake and egg weight. Feed intake and egg weight can significantly affect profits of egg producers. As hens age, the protein requirement decreases so that more corn and less soybean meal are used, which results in a higher energy content for older hens. Increasing dietary energy in the older hens may not decrease feed intake as well as in young hens because of the higher dietary energy content in diets for old hens. There is limited information in the literature on the effect of dietary energy on performance, egg composition, egg solids, egg quality, and profits of postmolt hens. In addition, egg weight and egg production during phase 1 of the second cycle (approximately 12 wk after the 4-wk molt) normally change dramatically. It is necessary to have a better understanding concerning how to optimize the use of dietary energy to obtain optimal performance and profits.

The objective of this study is to determine the effect of molting method and dietary energy on performance, egg components, egg solids, egg quality, and profits in Bovans White and Dekalb White hens during phase 1 of the second cycle (wk 70 to 82 of age).


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
This experiment was a 4 x 2 x 2 factorial arrangement with 4 dietary energy levels (2,767, 2,806, 2,846, and 2,886 kcal of ME/kg), 2 molting methods (feed withdrawal and the low-salt diet), and 2 strains (Bovans White and Dekalb White [34]). This experiment lasted 12 wk (phase 1 of postmolt). This is only a part of an experiment lasting 18 to 140 wk, including first treatments and several cycle hens. Because treatments other than energy and strain were used for different phases and diets (protein and energy levels varied) according to phase, the experiment had to be broken into parts to be manageable. Ingredients and nutrient composition of experimental diets are shown in Table 1Go. From wk 70 to 76, the 4 experimental diets containing 17.3% protein were used. From wk 77 to 82, protein level in 4 diets was decreased to 15.3% to better control egg weight, because egg weight from wk 70 to 76 was higher than the Bovans [35] recommended egg weight.


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  		Table 1. Ingredients and nutrient composition of experimental diets
 
Feed was withdrawn from half of the hens (66 wk of age) for 9 d. A molt feed was fed from d 10 to 28 (Table 1Go). The other half of hens was fed a low-salt diet for 28 d (Table 1Go). After the molt, the 2 treatments of Bovans White hens (n = 720) and Dekalb White hens (n = 720) at 70 wk of age were randomly divided into 16 treatments (6 replicates of 15 birds per treatment). Replicates were equally distributed into upper and lower cage decks to minimize cage level effect. All hens were housed 3 per cage (40.6 x 45.7 cm2) cage and 5 adjoining cages consisted of a replicate. All hens were housed in an environmentally controlled house with temperature maintained as close to 25.6°C as possible. The light period was reduced from 16 to 8 h daily from d 1. On d 29 the light period was returned to 16 h daily. All hens were supplied with feed and water ad libitum. Egg production was recorded daily, feed consumption was recorded weekly, and egg weight was recorded every other week. Egg specific gravity was determined monthly. Egg weight and egg specific gravity were measured for each replicate using all eggs produced on 2 consecutive days without storage. Egg specific gravity was determined using 11 gradient saline solutions varying in specific gravity from 1.060 to 1.100 with 0.005-unit increments [36]. Feed consumption per hen daily = (the ending feed weight of each trough – the beginning feed weight each trough)/number of hens each trough/7 d. Mortality was determined daily and feed consumption was adjusted accordingly. Body weight was obtained by randomly weighing 3 hens (1 of 5 cages) per replicate. Egg mass and feed conversion (g of feed/g of egg) were calculated from egg production, egg weight, and feed consumption.

Egg components and albumen and yolk solids were measured using 4 eggs from each replicate on 2 consecutive days in the middle (wk 6) and the end (wk 12) of the experiment. Two eggs from each replicate were collected to measure whole egg solids on 2 consecutive days in the middle and the end of the experiment. The procedures for measuring egg components, whole egg solids, and albumen and yolk solids were the same as those of Wu et al. [25]. Yolk color and Haugh units were measured (3 eggs from each replicate) at the end of experiment using an egg multitester EMT-5200 [37].

Data were analyzed by PROC MIXED procedures of Statistical Analysis System [38] for a randomized complete block with a factorial treatment design. Dietary energy, molting method, and strain were fixed, whereas blocks were random. The factorial treatment arrangement consisted of 4 dietary energy levels, 2 molting methods, and 2 layer strains. The following model was used to analyze data:


Formula

where Yijkl = individual observation; µ = experimental mean; {alpha}i = dietary energy effect; βj = molting method; {gamma}k = layer strain effect; ({alpha}β)ij = interactions between dietary energy and molting method; (β{gamma})jk = interactions between molting method and strain; ({alpha}{gamma})ik = interaction between dietary energy and strain; ({alpha}β{gamma})ijk = interactions among dietary energy, molting method, and strain; Pk = effect of block; and {varepsilon}ijkl = error component.

If differences in treatment means were detected by ANOVA, Duncan’s multiple range test [38] was applied to separate means. A significance level of P ≤ 0.05 was used during analysis.


   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
The average beginning body weights of the Bovans and Dekalb hens prior to molt were 1.62 and 1.57 kg, respectively. Feed was withdrawn from the hens (66 wk of age) for 9 d. Bovans and Dekalb hens lost 32.8 and 32.9% BW by d 9, respectively. A molt diet was fed from d 10 to 28 (Table 1Go). The other half of hens were fed a low-sodium diet for 28 d. Bovans and Dekalb hens lost 16.4 and 17.8% BW, respectively, by d 9, and 21.8 and 19.8% at the end of the 28-d molt period. Production of hens molted by feed withdrawal was 0% by d 7. The hens fed the low-sodium diet ceased production at a slower rate decreasing to 0% after approximately 17 d.

There were no interactions among strain, dietary energy, and molting method in feed intake, egg production, egg weight, egg mass, feed conversion, energy intake, body weight, and mortality (Table 2Go). Strain had no significant effect on feed intake. With increasing dietary energy, feed intake did not decrease linearly. Although there was a clear numerical decrease, this is inconsistent with that of Wu et al. [25], who reported that feed intake decreased linearly as dietary energy increased. This might be to due to smaller increments between dietary energy levels (approximately 40 kcal of ME/kg) in this experiment, compared with that (approximately 80 kcal of ME/kg) of Wu et al. [25]. In addition, the experiment was conducted during the winter. Although target temperature (25.6°C) was set, the average house temperature was less than the target temperature. Although feed intake of hens molted by feed withdrawal was significantly higher than that of hens molted by the low-salt diet in wk 2, 5, and 9, there was no significant difference in overall feed intake between hens molted by feed withdrawal and hens molted by the low-salt diet. This result was similar to that of Naber et al. [14].


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  		Table 2. Influence of dietary energy and molting method on postmolt performance of Bovans White and Dekalb White hens from 70 to 82 wk of age
 
Bovans hens had significantly higher egg production and lower egg weight than Dekalb hens (Table 2Go). Dietary energy had no significant effect on egg production (Table 2Go). This was consistent with that of Wu et al. [26, 27] and Jalal et al. [33], who reported that there was no significant effect of dietary energy on egg production (Table 2Go). Dietary energy had no significant effect on egg weight (Table 2Go), which is inconsistent with that of Wu et al. [25], who reported that egg weight increased linearly with increasing dietary energy. Wu et al. [25] suggested that the increase of egg weight was mainly due to increased yolk weight for young hens. Sell et al. [39] hypothesized that hens during early egg production might need more exogenous fat to supply lipids for egg yolk development. Percent egg yolk did not increase with increasing dietary energy by the addition of poultry oil (Table 3Go). Because hens were fed the high dietary energy molt diets, hens might already have enough fat reserve so that increasing dietary energy had no effect on egg weight during postmolt production periods.


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  		Table 3. Influence of dietary energy and molting method on postmolt egg component, egg solids, and egg quality in Bovans White and Dekalb White hens from 70 to 82 wk of age
 
Egg production of hens molted by feed withdrawal was numerically lower than that of hens molted by the low-salt diet in wk 1 and 2, and then increased quickly from wk 3. Although hens molted by feed withdrawal had significantly higher egg production than hens molted by the low-salt diet in wk 6, 7, 9, 10, and 11, there was no significant difference in overall average egg production between hens molted by feed withdrawal and hens molted by the low-salt diet (Table 2Go). Similarly, Said et al. [15] and Naber et al. [14] reported that molting method had no effect on egg production. In contrast, Ross and Herrick [11] reported that hens molted by feed withdrawal had significant higher egg production than hens molted by the low-salt diet. The difference among researchers might be due to higher sodium content in the low-salt diet of Ross and Herrick [11].

Egg weight of hens molted by feed withdrawal was significantly lower than that of hens molted by the low-salt diet in wk 1, and then increased quickly from wk 2. Hens molted by feed withdrawal had significantly higher egg weight than hens molted by the low-salt diet in wk 4. From wk 5, there was no significant difference between hens molted by feed withdrawal and hens molted by the low-salt diet. Overall average egg weight of hens molted by feed withdrawal was the same as that of hens molted by the low-salt diets (Table 2Go). This result was in agreement with those of Ross and Herrick [11], Said et al. [15], and Naber et al. [14], who reported that there was no significant difference in egg weight due to molting method.

There was no significant effect of strain on egg mass (Table 2Go). Dietary energy had no significant effect on egg mass. This result was in agreement with that of Wu et al. [24–26], who reported that there was no significant effect of dietary energy on egg mass. Strain had no significant effect on feed conversion. As dietary energy increased from 2,767 to 2,886 kcal of ME/kg, there was a numerical but nonsignificant improvement in feed conversion. With increasing dietary energy hens adjusted feed intake, according to egg mass, to achieve similar quantities of energy (5.8 to 5.9 kcal/g of egg). Because increasing dietary energy by addition of poultry oil had no significant effect on feed intake, egg mass, and feed conversion, an ideal dietary energy level for optimal postmolt performance could not be determined. This conclusion was different from that of Wu et al. [25], who reported that there was an ideal energy/protein ratio for optimal performance during phase 1, probably because egg weight increased linearly and feed intake decreased linearly with increasing dietary energy in the experiment of Wu et al. [25].

Hens molted by feed withdrawal had the same feed conversion and egg mass as hens molted by the low-salt diet. In addition, hens molted by feed withdrawal used the same quantity of dietary energy (5.8 kcal) to produce 1 g of egg (Table 2Go). This suggests that molting method has no effect on efficiency of dietary energy utilization. Strain and dietary energy had no influence on body weight and mortality (Table 2Go). There was no significant difference in body weight of hens and mortality between hens molted by feed withdrawal and hens molted by the low-salt diet. Similar results were reported by Naber et al. [14] and Said et al. [15]. However, Ross and Herrick [11] reported that hens molted by the low-salt diet had significantly higher mortality than hens molted by feed withdrawal.

There was no interaction among strain, dietary energy, and molting method in percent of yolk, albumen, and shell, percent of whole egg solids, yolk solids, and albumen solids, egg specific gravity, Haugh units, or yolk color (Table 3Go). Whereas Bovans hens had a similar percent of yolk and albumen as Dekalb hens, Bovans hens had significantly lower percent of shell and egg specific gravity than Dekalb hens. These results and those of Wu et al. [25] suggest that Dekalb hens have a slightly better eggshell quality than Bovans hens. Bovans hens had similar percent of whole egg solids, yolk solids, and albumen solids as Dekalb hens. Increasing dietary energy had no effect on egg specific gravity (Table 3Go) probably because egg weight did not increase with increasing dietary energy. Dietary energy had no effect on percent of yolk, albumen, shell, or percent of whole egg solids, yolk, or albumen solids. These results were in agreement with Wu et al. [25], who reported that there was no significant effect of dietary energy on egg components and egg solids, which are very important factors influencing profits of the breaker egg industry.

Percent of yolk, albumen, and shell and percent of whole egg solids, yolk solids, and albumen solids of hens molted by feed withdrawal were similar to those of hens molted by the low-salt diet (Table 3Go). Molting method had no effect on postmolt egg composition and egg solids. Although hens molted by feed withdrawal had significantly higher egg specific gravity than hens molted by the low-salt diet during wk 8, there was no significant difference in overall average egg specific gravity due to molting method. In addition, hens molted by feed withdrawal had the same percent of eggshell as hens molted by the low-salt diet. These results and the results of Ross and Herrick [11], Naber et al. [14], and Said et al. [15] suggested molting methods had no significant effect on eggshell quality. It is possible that the small differences observed in eggshell quality between the molt-methods could increase as hen ages. Dekalb hens had significantly higher Haugh units than Bovans hens. A similar result was reported by Wu et al. [25] in first cycle hens. Dietary energy had no effect on Haugh units. Hens molted by feed withdrawal had similar Haugh units as hens molted by the low-salt diet. This result was in agreement with that of Ross and Herrick [11] and Said et al. [15], who reported that there was no significant difference in Haugh units due to molting methods. Neither strain nor molting method had a significant effect on yolk color. Increasing dietary energy significantly increased yolk color (darker).

An Economic Feeding and Management Program developed by Roland et al. [40, 41] was used to calculate profits of different dietary energy levels at different poultry oil prices. When poultry oil price was $0.26/kg, maximum profits per dozen eggs were obtained in hens fed the diet containing 2,846 kcal of ME/kg of dietary energy (Table 4Go). However, when poultry oil price increased to $0.40/kg, maximum profits were obtained in hens fed the diet containing 2,767 kcal of ME/kg of dietary energy. Because feed ingredient prices and egg price vary, there can be no fixed ideal dietary energy level for optimal profits for postmolt hens. Although no significant effects of dietary energy was observed on feed intake, egg production, egg weight, or egg mass, a trend for improvement was observed.


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  		Table 4. Influence of dietary energy and poultry oil price on profits1,2
 

   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 
  1. Bovans hens had significantly lower egg weight, percentage of eggshell, egg specific gravity, and Haugh units than Dekalb hens, whereas Bovans hens had significantly higher egg production than Dekalb hens.
  2. Increasing dietary energy by the addition of poultry oil had no significant effect on performance, egg components, egg solids, or Haugh units after molt.
  3. As dietary energy increased from 2,767 to 2,886 kcal of ME/kg, feed conversion improved numerically from 2.13 to 2.05, resulting in a 3.8% improvement in feed conversion. With increasing dietary energy levels, hens adjusted feed intake, according to egg mass, to achieve the similar quantities of dietary energy (5.8 to 5.9 kcal/g of egg).
  4. An ideal dietary energy level for optimal postmolt performance could not be determined, and there can be no fixed ideal dietary energy level for optimal profits because energy and egg prices vary.
  5. Egg production of hens molted by feed withdrawal was significantly higher than that of hens molted by the low-salt diet in wk 6, 7, 9, 10, and 11. Hens molted by feed withdrawal had significantly higher egg specific gravity than hens molted by the low-salt diet during wk 8. There were no significant differences in overall average egg production and egg specific gravity due to molting method.
  6. Other than slightly reduced egg production and egg specific gravity, feeding the low-salt diet to induce molt could be used as an alternative for a conventional feed withdrawal method.


   ACKNOWLEDGMENTS
 
The authors thank Centurion Poultry Inc., Lexington, GA, and Ridley Inc., Mankato, MN, for funding support of this research.


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

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