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Research Reports |
Department of Poultry Science, North Carolina State University, Raleigh 27695
Correspondence: 1 Corresponding author: ken_anderson{at}ncsu.edu
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SUMMARY |
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 TOP SUMMARY DESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Key Words: laying hen • population • molting program • egg production • egg size • net income
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DESCRIPTION OF PROBLEM |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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It has been known for many years that as the number of layers per cage increases and floor space or cage density increases, productivity of the birds involved decreases [6, 10, 11], and this has been discussed in general reviews [12, 13]. Marks et al. [10] found that genetic strain x cage density interactions are not important and that all of the strains they tested reacted in the same manner to increasing density in 1-, 2-, and 5-bird cages. Most of the early cage density studies had cage floor space and feeder space confounded so that as cage space declined feeder space also declined. Thus, researchers could not determine whether the decline in performance was due to increased density or to the limitation in feeder space. Some speculated that the density effects could be overcome with higher density diets, but Carew et al. [14, 15] found that increasing the diet density did not overcome the decline in performance caused by increasing the numbers of birds per cage. In the late 1980s, a study was designed to separate the effect of lay house cage density and feeding space using cages designed to have the same feeder space at 2 density levels [16]. That study involved 4 vs. 6 birds per cage at density levels of 316 and 406 cm2, and it was found that the increased cage density and the increase from 4 to 6 birds per cage resulted in reductions in egg production of 2.2 and 2.6%, respectively. Anderson and coworkers [17] also reported that brown-egg layers had improved performance when housed 6 hens per cage with 482 vs. 361 cm of floor space and 10.2 lineal cm of feeder space.
In 2003, the United Egg Producers released "Animal Husbandry Guidelines for U.S. Egg Laying Flocks". Those guidelines [18] were updated in 2005 and called for a minimum of 64 in.2 and 72 in.2 of laying cage space for white-egg and brown-egg layers, respectively, by October 1, 2006. Those guidelines along with the fact that most commercial layers are kept in 3-bird or 4-bird cages were the basis for the choice of the cage size and densities used in the current study.
Induced molting is a practice that has been used since the 1930s to rejuvenate laying flocks for a second or third cycle of production [for a historical review, see 19]. Several molting methods have been studied over the years, including: 1) feed removal or limitation, 2) low nutrient rations, and 3) various feed-additives [19]. Based on numerous research studies, the commercial egg industry over the past 50 + yr has generally used a total feed withdrawal of up to 14 d with water supplied ad libitum to initiate the molt. In fact, as reported by Bell [19], an informal survey of egg industry nutritionists in 2002 indicated that virtually all commercial flocks were being molted using a feed withdrawal program at that point in time. When done properly, the feed withdrawal molting program results in very satisfactory improvements in egg production and shell quality and allows the flock to continue to be maintained in an economically sound manner for an additional 25 to 30 wk. Over the past 10 to 15 yr, however, the animal rights and animal welfare communities have become increasingly critical of the total feed withdrawal practice for inducing the molt. Thus, the industry has for some time been looking for alternative procedures for molting their flocks [20]. One potential procedure that has been looked at to a limited degree in the past [21] is the maintenance of birds on a very low density (i.e., low protein, low energy, high fiber) diet during the normal feed withdrawal part of the molt, and that is the method that was studied herein.
The objective of this paper was to summarize the primary data from the management options that were included in the 35th NCLM& PT, and how the white and brown egg strains involved reacted to the options of cage population and to an alternative nonfasted molting program.
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MATERIALS AND METHODS |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Complete details of the experimental design and pullet management of the 35th NCLP&MT are provided in 4 reports [23, 24, 25, 26].
Layer Housing
The pullets were moved into a totally enclosed force ventilated laying facility during wk 16 and were randomly assigned to 252 replicates for a total of 6,048 hens. Blocks of laying cages with the white egg and brown egg strains were interspersed among the replicates that were contained in 2 banks of 3-deck cages and 4 banks of 4-deck cages. Each replicate block contained 8 cages with 3 hens/cage or 6 cages with 4 hens/cage. Each block is equipped with a feed hopper for monitoring feed consumption, and the feed is distributed by an automatic feeding system. The house was cleaned and manure was removed on a weekly basis via a pit scraper manure handling system.
Layer Management and Nutrition
Lay House Nutrition Programs.
The laying rations utilized are summarized in Table 1
. The rations provided for the white-egg and brown-egg strains involved a phase feeding program, which provided for the minimum daily intake of nutrients required to meet the brown-egg or white-egg strain’s intake requirements depending on age-related level of production and consumption as shown in Tables 2 and 3. Layer diets were identified as diets D, E, F, G, H, I, M, N, O, P, and Q, which consisted of a prelay and a series of lay diets formulated to assure the minimum daily protein, mineral, and amino acid intakes shown in Table 3 for the consumption rates and production stages shown in Table 3. All feed was offered ad libitum in the form of crumbles to reduce feed separation and feed wastage.
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Molting Programs.
All strains were randomly divided into 3 groups such that all strains, cage population sizes, cage banks, cage rows, and cage levels were approximately equally represented. Thus, there were at least 3 replicates for each strain, population, and molt treatment combination, when the 3 molt treatment groups were initiated at 66 wk of age: 1) control—nonmolted and full fed (coded NM); 2) feed restriction molted—no feed provided for 13 to 14 d (coded FR), then placed on maintenance diet for 14 d; and 3) nonfast molted—maintenance diet with low protein and low energy (coded NF). Three randomly selected replicates of brown and white egg layers from each molt, strain, and population group were monitored for BW loss. The hens were weighed prior to the initiation of the molt, then at 7 and 9 d after the molt was initiated to determine rate of BW loss, when the FR group was placed back on feed, and then at the end of the molt period. When the BW loss target was reached for the molt treatment groups, all replicates within the layer type/molt treatment group were weighed. At the end of the molt period, all molted hens were placed on diet E (Table 1
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The following molt regimens were followed:
Control nonmolted (NM): All replicates assigned to this treatment were maintained on the normal laying program as previously described. The laying house was partitioned so that the normal lighting program to continue maximum production independently of the molted groups. Birds in the NM treatment group were maintained in lay throughout the entire 119 to 791 d laying period. A booster vaccination for New-castle/bronchitis was provided to this treatment group at the same time it was provided to the white and brown egg strains on the 2 molting programs.
Feed restriction molted (FR): The FR feed withdrawal/restriction molting program included a maximum 14-d fasting period and in general was representative of existing US egg-industry molting programs.
Day – 7. The lighting period was increased to 24 h at 65 wk of age.Day – 7. Samples of white-egg and brown-egg birds were weighed to determine the premolt BW. Target weight (i.e., a 30% BW loss) was calculated using the premolt BW.
Day 0. Remaining feed was removed from the feeders and the light period was reduced to 9 h. All moribund birds were removed and euthanized before feed restriction.
Day + 1. A booster vaccination for Newcastle/bronchitis was provided.
Day + 7 to 9. Samples of white-egg and brown-egg birds were weighed at 7 and 9 d after feed removal, and the 2 sample weights were then averaged to determine daily BW loss. The BW loss/d was used to estimate the days needed to reach the targeted 30% BW loss target.
Day + 13 to 14. Birds were weighed based on the target BW loss to determine actual BW loss. Strains or treatment groups were placed on full feed using the reduced protein and energy molt diet (Table 1
Day + 24. The light period was increased to 12 h.
Day + 28. All of the randomly selected replicates chosen for monitoring BW were reweighed. Birds on this treatment were returned to layer diet E (Table 1
Day + 31. Lights were returned to 16.5 h.
Non-fast molted (NF): Hens on the NF treatment were fed a low protein and low energy diet throughout the molt period. The molt diet (Table 1) was balanced for the amounts of vitamins and minerals required for body maintenance, and it has been shown (data unpublished [27]) that this diet can be used to maintain a healthy anovulatory state.
Day – 7. Light period was increased to 24 h at 65 wk of age.Day – 7. Samples of white-egg and brown-egg birds were weighed to determine the premolt BW. A target BW (24% BW loss) was calculated using the premolt BW.
Day 0. All remaining laying feed was removed and replaced with the low protein and low energy molt diet, which was provided ad libitum throughout the molting period. The light period was reduced to 9 h. All moribund birds were removed and euthanized before feed restriction.
Day + 1. A booster vaccination for Newcastle/bronchitis was provided.
Day + 7 to 9. The BW monitoring replicates were reweighed on 7 and 9 d after the feed change and the differences in BW were used to determine BW loss. The BW loss/d was then used to estimate when the 24% target BW loss would be reached.
Day + 13. All birds in the monitoring replicates were reweighed to determine BW loss.
Day + 24. Light period was increased to 12 h.
Day + 28. All BW monitoring replicates were reweighed, and birds on this treatment were returned to layer diet E (Table 1
Day + 31. Lights were returned to 16.5 h.
Production Data Collection
All eggs that had the potential of being marketed were collected and recorded on a daily basis for all replicates, regardless of the shell condition. Egg production was reported on a hen-day basis and summarized at 28-d intervals for the entire production and molting period from 119 to 791 d of age. Feed consumption/100 hens/d was also recorded for each 28-d interval over the same time period. During the third week of each 28-d period, all eggs produced during the previous 24 h were collected, weighed, sorted, and graded using the USDA grading standards. The blending of the egg sizes was done with the weight cutoff between medium and large being 23.5 ounces/dozen, which maximizes the number of USDA large eggs, as done in a commercial egg processing plant. The income per hen housed was calculated using a 3-yr regional average egg price by egg size category [23]. Feed consumption was expressed as kilograms of feed consumed/d per 100 hens housed or per 100 hen days for the period. Feed conversion was calculated as grams of egg produced per gram of feed consumed. Feed costs were based on the actual feed prices for each feed delivery, which were calculated and summarized for the complete production cycle. Mortality is reported as the percentage of birds that died during the first production cycle (119 to 462 d), molt period (463 to 490 d), and second cycle (491 to 791 d).
Statistical Analysis
All data were subjected to ANOVA utilizing the GLM procedure of SAS [28] with main effects of strain, cage population, and molting program. Separate analyses were conducted for white and brown egg strains. The interaction of molting procedure and cage population was included in the analysis of the molt and second cycle (postmolt). Mean differences were separated via the PDIFF option of the GLM procedure of SAS.
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RESULTS AND DISCUSSION |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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. The data provided are the averages for the 7 white-egg and 3 brown-egg strains. Mortality levels and the age at 50% production were not significantly different between the 3-bird and 4-bird cages for either type of layers. For both types of layers, birds housed in 4-bird cages had significantly higher feed consumption (P < 0.01 for white egg strains; P < 0.05 for brown egg strains) than did those housed in 3-bird cages. The white egg strains in 4-bird cages also had significantly higher hen-day egg production (P < 0.05) and significantly higher daily egg mass (P < 0.05) than did their counterparts housed in 3-bird cages. Even though the number of eggs per hen-housed was not significantly different for the 2 cage populations for the white egg strains, the significant differences that were present in hen-day rate resulted in a 0.5 g larger daily egg mass being produced by the birds in the 4-bird cages. None of the production parameters were significantly different between the brown-egg layers (Table 4) housed in 3-bird vs. 4-bird cages. These results are not in agreement with other research [16, 17] that showed when white and brown egg layers were housed at 6 birds/cage they had lower productivity than those housed 4 birds/cage. This is probably due to the finding of Cunningham [16] that the productivity of populations above 4 will result in diminished performance.
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. The differences in average egg weights between the birds housed in the 3-bird and 4-bird cages were not significant for either type of layer. Most of the differences in average egg size and egg grade for both sets of data were not significant either. The primary exception was that white egg strains in 3-bird cages produced 0.5% fewer USDA grade A eggs (P < 0.05) and 0.4% more cracked eggs (P < 0.05) than did the white egg strains in 4-bird cages. Brown egg strains in 3-bird cages produced 0.9% more peewee and small eggs (P < 0.05) than did their counterparts in 4-bird cages.
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. No differences were observed in egg income for the 2 population sizes for either type of layer, but due to their higher feed consumption, the white egg birds in the 4-bird cages had 18 cents higher feed cost per hen for the first production cycle. The increased feed cost was offset by the egg income generated in this population that was associated with their production rate and egg size.
Molt Period, 463 to 490 d of Age
Cage Population Number Effects.
Performance measurements by layer type, population number, and molting program during the 463 to 490 d molt period are summarized in Table 6. Because each group of layers was molted within their assigned laying cages, which included both 3-bird and 4-bird cages, a cage population x molting program interaction effect was included in the statistical analysis. None of those interactions were significant for any of the traits measured for either type of layer.
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), but during the molt this difference was significant only for the brown egg strains (P < 0.01). Again, as was the case during the first production cycle, the higher rate of feed consumption resulted in significantly higher (P < 0.05) feed costs for the brown-egg birds in the 4-bird cages during the molt than for those housed in 3-bird cages. However, population number had no effect on the numbers of eggs produced per hen-housed, nor did it affect hen-day production, mortality rate, or egg income during the molting period for either type of layer.
Molting Program Effects.
Three molt treatment groups were compared (i.e., those that were not molted; the FR program where the birds were provided water at all times, but no feed for the first 13 d before being placed on the same low protein molt diet used for the NF treatment of the remainder of the molt period; and the NF or nonrestricted group that was provided the low protein, low energy molt diet throughout the molt period). Performance data from these 3 molt treatment groups for the 2 types of layers are summarized in Table 6.
As expected, the NM hens that were continued on feed and in normal production had significantly higher feed consumption, egg production, feed cost, and egg income during the molting period than did the 2 molted groups for both layer types (Table 6). These results are in good agreement with the results from numerous previous studies [19]. Not surprisingly, the NF layers placed on the low protein molt diet throughout the molt period consumed approximately 70% more feed (P < 0.01) than did those on the FR program, and because of that the molt period feed costs for the NF layers were 68 and 94% higher than for the FR birds for the white and brown egg layers, respectively. Mortality rates among the NM, NF, and FR programs for the white-egg strains were not significantly different. The NM brown-egg layers had significantly (P < 0.05) less mortality than did the birds placed on the NF and FR programs. Hen-day production (79.2% for white egg; 77.1% for brown egg) and hen-housed egg number (19.8 for white egg; 19.6 for brown egg) were significantly higher for the NM groups, which resulted in $1.18 of egg income for the nonmolted hens of both layer types during the molting period. The NF and FR groups also had egg income during the molt, but the level of income during the molting period for the white egg layers and brown egg layers on the NF program was 78 and 70% lower than for the NM groups, respectively. Similarly, egg income from the FR groups of white-egg and brown-egg layers was reduced by 81 and 85% below the NM groups, respectively. These differences in egg income during the molting period are important for the overall economic assessment of nonmolting vs. alternative molting programs.
Body Weight Changes During the Molt.
Body weights were taken at various ages for the test flock involved. Some of those BW and BW gains are summarized in Table 7. As shown, none of the cage population or molting program groups differed in BW at the time they were placed into the lay house (17 wk), or at the end of the first production cycle (66 wk), and consequently none of the groups differed in BW gain during the first cycle. Both NM groups of white and brown egg layers lost about 3% of their BW during the molting period, probably due to slightly reduced feed consumption during the summer season when the molt period occurred. The NF groups of white egg and brown egg layers lost 21.1 and 17.4% of their BW, respectively. The FR white egg and brown egg groups lost 32.2 and 27.9% of their BW, respectively. Thus, in agreement with previous reports [21], it is more difficult to reduce the BW of brown-egg layers than white-egg layers (Table 7) and to take them out of production (Table 6).
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. None of the differences in production, feed consumption, feed conversion, or mortality between the 3-bird and 4-bird cage treatment groups were significant, except for the feed consumption of the brown egg birds in the 4-bird cages. In that case, in agreement with the data from the first production cycle and the molt cycle, the birds in 4-bird cages consumed more feed than did those in the 3-bird cages. This resulted in slightly, although not significantly, higher feed costs and egg income for the 4-bird cage brown egg layers than for those in the 3-bird cages (Table 9).
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). For the white-egg comparison, the NF and FR test groups produced 28.4 and 33.3 more eggs per hen-housed than the NM layers during the second production cycle.
Average egg weight (Table 9) did not differ significantly for the 3 molt test groups for the white or the brown egg data sets. Neither did the average USDA egg size grades differ for the 3 test groups, except for the extra large category for the white egg layers. In those cases, the NF and FR molted groups, respectively, had 4.2 and 2.7% more extra large eggs than did the NM group. Again, as expected, the NF and FR groups for the white egg layers had significantly more USDA Grade A, and significantly less Grade B eggs than did the NM groups. For the brown egg layers, the FR groups had significantly more USDA Grade A eggs and fewer Grade B eggs than did the NM groups. The NF brown egg group had 2.4% more grade A than did their NM counterparts, but the difference was not significant. Due to their higher production rate during the second production cycle, feed costs and egg income were significantly higher for the NF and FR groups than for the NM group in both data sets. Again, the NF and FR groups were not significantly different with regard to feed costs and egg income (Table 9). Even though the NF and FR feed costs did not differ, egg income from the brown-egg FR group was higher than for the brown-egg NF group.
Total Production Cycle, 119 to 791 d of Age
Because none of the 3-bird vs. 4-bird cage comparisons during the first production, molt, or second production cycles were significantly different, they will not be discussed here. Evaluation of the overall economic performance of the 3 molt groups was based on the data presented in Tables 5, 6, and 9 (i.e., assigning the average egg income over feed costs for the 3-bird and 4 bird cages in Table 5 from the first cycle to all 3 molt groups) indicates that the NM, NF, and FR molt treatments resulted in $11.72, $12.04, and $12.61 of egg income over feed costs per bird for the white egg layers, respectively. The egg income was calculated based on a 3-yr regional egg prices by egg size category, and feed costs were calculated based on the actual costs of the feed delivered. On this basis, both white-egg molt groups outperformed the nonmolted group on a total life of flock basis. The FR group also outperformed the NF molt treatment group of white egg layers. Using the same comparison for the brown egg layers provides egg income over feed costs of $10.72, $10.91, and $11.91 for the NM, NF, and FR molt groups, respectively. Thus, from an economic standpoint, the traditional fasting type molting program (FR) provided the greatest economic return for both layer types, followed by the nonfasting (NF) program. With both layer types, the nonmolting program provided the least income over feed costs, and, of course due to its poorer shell quality for the second production cycle for both layer types, presents additional challenges related to egg processing and egg breakage.
The results herein related to the productivity of the birds molted with the low protein, low-energy diet are in contrast to results from several studies involving birds molted with a continuous molt-diet feeding program [29,30, 31]. The total reason for this result is not clear but may be due to the fact that provision of the molt diet used herein caused reductions in BW for the white-egg and brown-egg layers of only 21.1 and 17.4%, respectively, during the molt, compared with over 30% for most of the alternative diets. However, the Zimmerman et al. study [29] showed comparable production levels to that of the industry-type fasted program. Biggs et al. [30, 31] concluded that the feeding of wheat middlings, corn gluten meal, or a combination wheat middling:corn diet could be used for molting without feed removal. Regardless, a clear contributing factor is the significant reduction in total mortality in the hens molted with the NF and FR programs vs. the NM hens. This was true in the white-egg and brown-egg strains and for both molt treatments. In the white-egg strains both the NF and FR molted hens had 8% fewer mortalities than the NM hens. In the brown-egg strains a 7.8% reduction in mortality in the NF hens, and a 12% reduction in the FR hens from the 18.1% mortality in the NM hens resulted in greater total egg production and subsequent income. However, in our estimation, with the ineffectiveness of the alternative molt programs for reducing BW and considerable differences (although not statistically different) in the postmolt performance compared with the level of production achieved with the traditional fasted program, the diets shown would be of questionable acceptance to the commercial industry. This indicates that further refinements of the NF methods are needed. A larger study should be conducted with greater statistical power of the test using the Zimmer-man et al. [29] and Biggs et al. [30, 31] diets to determine whether these diets do provide equal postmolt performance to the traditional fasted molting program.
Final Body Weight 119 to 791 d of Age
The cage population had no effect upon the weight gain of the hens within the 3 molt treatment groups (Table 10). The overall weight gain for the nonmolted group was significantly (P < 0.05) lower than in either of the molted groups.
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CONCLUSIONS AND APPLICATIONS |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Effects of the Alternative Molting Programs
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ACKNOWLEDGMENTS |
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REFERENCES AND NOTES |
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TOPSUMMARYDESCRIPTION OF PROBLEMMATERIALS AND METHODSRESULTS AND DISCUSSIONCONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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