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Performance of Leghorn Hens Induced to Molt by Limited Feeding of Diets Varying in Nutrient Density1
Performance of Leghorn Hens Induced to Molt by Limited Feeding of Diets Varying in Nutrient Density1 N. G. ZTMMERMANN and D. K. ANDREWS Department of Animal Sciences, Washington State University, Puyallup Research and Extension Center, Puyallup, Washington 98371-4998 (Received for publication March 19, 1990)
1990 Poultry Science 69:1883-1891 INTRODUCTION
The majority of laying hens providing table eggs in the United States are induced to molt one or more times during their productive life (Bell, 1989). The most frequently used method of inducing molt incorporates feed deprivation for BW reduction (BWR) in conjunction with decreased photoperiod (John Brake, North Carolina State University, Raleigh, NC and Don Bell, University of California, Riverside, CA, personal communication). Mrosovsky and Sherry (1980), working with wild birds, found mat weight loss is a natural physiologic phenomenon having survival value. The success of induced molt by fasting techniques to improve egg quality and numbers during the subsequent lay cycle has been researched and documented. Len et al. (1964) analyzed 2 yr of California random sample tests and associated molting and the loss of BW with feed efficiency and improved income over feed costs in the molted flocks. Brake and
'Project 0643. Animal Sciences Scientific Paper Number 8019. College of Agriculture and Home Economics Research Center, Washington State University, Pullman, WA 99164.
Thaxton (1979) postulated that weight loss of the liver, oviduct, and ovary and their subsequent rejuvenation were related to postmolt performance. Baker et al. (1981, 1983) stated that molt induced by fasting until 27 to 31% BWR produced optimal postmolt performance. Ruszler (1984) indicated that periodic feeding on recurring days equitably lowered average feed intake, induced molt, and avoided prolonged feed deprivation to reduce BW. Zimmermann et al. (1987), seeking alternative, less severe methods of inducing weight reduction during molt, tested limited feeding as a method to achieve 30% BWR. Limited feeding was achieved by allowing hens to feed ad libitum for 6 h per period on 3rd, 4th, or 5th recurring days. Results indicated that limited feeding of layer diet was as effective in obtaining acceptable postmolt performance as other methods employing fasting. Dietary composition during the post-BWR prelay interval of an induced molt may (Brake et al, 1979, 1984; Harms, 1983; Andrews et al., 1987) or may not (Bell, 1984; Zimmermann et al., 1987) affect postmolt lay performance. Perhaps the diet fed during a limited feeding induced molt could also affect subsequent lay performance.
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ABSTRACT The effects of diet type and of the periodicity of limited feeding used to induce molt in 78-wk-old Leghorn hens on postmolt performance were evaluated. The experimental design was a 3 x 3 factorial arrangement of treatments, plus a fasted control. Either ground corn, a 22% protein starter, or a 15% protein layer mash diets were available ad libitum for 6 h on the 3rd, 4th, or 5th recurring days; approximately 30% BW reduction was attained after 23,20, and 17 days, respectively, of limited feeding. A pullet developer feed was then full fed until the end of the 35-day molt period. Records of lay performance during the 35-day, molt-inducing period and for the following seven, 28-day periods were kept. Many significant (P£.05) treatment effects and interactions were observed during the 35-day, molt inducing period. However, when these data were integrated with the following seven periods of data, no significant (P>.05) treatment difference or main effect interaction was observed for egg production, egg weight, feed per hen per day, Haugh units, shell weight, shell weight per unit surface area, or mortality. The results demonstrate that neither the diet fed during limited feeding nor the period of limited time feeding used to induce molt in the present experiment was of long-term importance. Further, the results demonstrate that molt induced by limited feeding is an acceptable alternative to continuous fasting. (Key words: molt, induced, limited feeding, diet, layer performance)
1884
ZEMMERMANN AND ANDREWS TABLE 1. Ingredients and calculated nutrients of diets utilized
Ingredient and analyses
Ground corn
layer diet
Starter diet -
Calculated analyses Me, kcal/kg Protein, % Calcium, % Phosphorus (total), % Methionine, %
100 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3,360 8.9 .01 .25 .17
y/uj
72.35 14.00 0 5.50 0 0 0 0 7.50 0 0 0.10 .25 .25 .05 0
54.00 16.50 7.50 2.50 5.00 5.00 5.00 1.00 .84 1.17 .22 .08 .25 .25 .05 .64
82.25 12.00 0 4.00 0 0 0 0 .30 1.00 0 0 .15 .25 .05 0
2,843 15.35 3.50 .56 .34
2,784 21.94 120 .60 .50
3,106 14.60 .80 .50 .24
'Provided the following in each kilogram of mixed diet: vitamin A, 5,614 IU; vitamin D, 1,653 IU; vitamin E, 2.2 IU; vitamin Bj2, .009 mg; riboflavin, 4.4 mg; niacin, 27.6 mg-, d-calcium pantothenate, 6.6 mg; choline chloride, 276 mg; menadione, .5 mg. 2 Provided the following in parts per million of mixed diet: manganese, 50; zinc, 50; iron, 50; copper, 5; cobalt, .5; iodine, 15.
The purpose of the present experiment was to determine if the diet fed during a 3rd, 4th, or 5th recurring day limited time feeding to induce molt had an effect on postmolt performance. Another purpose was to further demonstrate that molt induced by limited feeding is an acceptable alternative to fasting. MATERIALS AND METHODS
Materials and methods similar to Zimmermann et al. (1987) were followed as they pertain to the limited feeding to induce molt. One thousand eighty Hisex2 Single Comb White Leghorn hens 78 wk of age randomly divided into 60 replicate lots of 18 hens each in an insulated and ventilated single room light-proof house, were induced to molt during September. A replicate lot consisted of a row of nine 30.5- (width) x 40.6- (depth x
2
Pilch-Hisex, P. O. Box 438, Troutman, NC 28166.
35.6- (height) cm single deck wire cages, each containing two healthy hens, regardless of existence of previous molt. The 10 treatment groups, including a continuous fasting control, were replicated six times and equally distributed throughout the room. Prior to starting the experiment, the hens were allowed a 2-wk adjustment period after randomization plus an 18-day premolt period during which daily egg production, weekly egg weight, egg specific gravity, shell weight, and shell weight per unit surface area (SWUSA), and Haugh units were measured. Treatments, excluding the control, were designed as a 3 x 3 factorial having three diet types and three periodicitiess of recurrent feeding days as main effects. All diets were available ad libitum for 6 h every 3rd, 4th, or 5th recurring day following introduction of fasting (Day 0) until an estimated 30% BWR was obtained. The three diets fed during this time consisted of eitfier ground corn, layer mash, or starter mash (Table 1). Ground corn was the lowest nutrient density diet, whereas
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Ground corn Soybean meal Alfalfa meal Meat and bone meal Brewers dried grains Brewers yeast Fish meal Safflower oil Limestone Dicalcium phosphate Lysine DL-methionine Salt Vitamin mix* Mineral mix 2 Inert filler
Developer diet
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INDUCED MOLT BY LIMITED FEEDING
1960). All data were analyzed using two different models: 1) all 10 treatments (10treatment model) to compare limited feeding to fasting induced molting and 2) 3 x 3 factorial analysis (factorial model) excluding the control to determine if any combination of main effects (diet and limited feeding periodicity) interacted. Covariance and correlation analysis with initial BW were utilized to determine if initial BW difference affected results. Significant differences (P<.05) between treatment means were identified by Duncan's multiple range test or by least squares means predicted differences (PDIFF) probability procedure (SAS Institute, 1985). RESULTS
Analysis of premolt lay performance indicated no significant (P<.05) difference in any of the measured lay performance variables among treatments or main effects prior to induced molt treatment. Based on BWR from sample hens, all replicate lots were reweighed and developer feed was available ad libitum to all fasted hens after 12 days of feed deprivation and to all 3rd, 4th, and 5th recurring day limited feeding treatments after 23, 20, and 17 days, respectively (Table 2). Initial BW and percentage BWR of the whole flock were 1798 ± 7 g and 29.7 ± .1 (x ± SEM), respectively. Mean BW at the termination of the experiment was 1874 ± 7 g (x ± SEM); no significant (P^.05) treatment differences existed. However, initial BW of randomly assigned lots receiving layer diet were significantly higher than several other treatments (Table 2). Factorial analysis showed that hens fed the layer diet had significantly (P<.05) higher initial BW, lost less percentage BW, and consumed more feed during and after BWR than either the birds given the starter or corn diets suggesting a relationship between initial BW, percentage BWR and feed consumption. Covariance analysis using the 10-treatment model revealed initial BW affected BW after BWR (P<.001), percentage BWR (P=.059), and final BW (P<.001) but did not affect feed per hen per day during BWR (P=.473), feed per hen per day of developer (P*=.126) or total feed per hen per day (P=.249) during the molt inducing period. Covariance analysis with the factorial model resulted in similar probability values. Interpretation of main effects and interactions did not change
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the starter mash provided the highest nutrient density. The layer diet was that fed by Zimmermann et al. (1987) during limited feeding experimentation. Six hours (0800 to 1400h) of full feeding on the assigned recurring days was assured by appropriate placement and removal of the feed troughs. Water was available ad libitum in cup waterers. Both hens in five to six cages from each treatment were individually weighed at intervals to estimate rate of BWR. Estimated day of 30% BWR was determined within each recurrent feeding day treatment and across all diets; thus, percentage of BWR was a measured variable between diets. After BWR, the hens entered a prelay period during which all groups received pullet developer mash (Table 1) ad libitum until Day 35. The hens were then (Day 36) fed layer mash for seven, 28-day laying periods. Hens were individually weighed before and after BWR and during the seventh period on spring balances accurate to 20 g. The photoregimen for all treatments was changed from 14 h of light and 10 h of dark (14L:10D) to 8L:16D (light on at 0500 and 0800 h, respectively) on the 1st day of feed deprivation (Day 0) and remained there for 28 days, then returned 14L:10D for the remainder of the trial. Illumination was supplied by 75-W incandescent bulbs attached to the sloping ceiling 2.2 to 3.4 m (minimum and maximum, respectively) above the feed troughs providing 8.3 to 18.2 cosine-corrected lux of illumination. Egg production, feed consumption, and daily mortality were recorded and separately analyzed during each phase (i.e., BWR and prelay) of the 35-day molt induction period. During the subsequent seven 28-day postmolt periods, egg production and mortality were recorded daily and egg weight weekly. Haugh units, specific gravity, shell weight, SWUSA, and feed consumption were recorded at the end of each period. Egg measurements were taken from all eggs laid during a 24-h interval. Shell weight, SWUSA, and days to 50% production were determined as described by Zimmermann et al. (1987). Data were summarized by period and were subjected to ANOVA with a split-plot design over period using general linear model procedures (SAS Institute, 1985). Arcsin square root transformation of percentage mortality was performed prior to analysis (Steel and Torrie,
3rd 4th 5th
1,4,7 2,5,8 3,6,9 Probability
Ground corn Layer Starter
<001, <001
<.001, .001
.108
23 20 17
<001, <001
1816 ± 12 1782 ± 12 1801 ± 13 .142
.011
14.8 ± 1.2b-v 16.9 ± 12s* 12.1 ± 13 c,w <001, <001
Means in columns with no common superscripts are significantly different (P4.05); results of IBW covariance ana
12 15 18
12 15 18 12 15 18 12 15 18 23
Days fed developer diet after BWR
Without and with IBW covariance analysis, respectively.
Analysis excludes fasted hens.
3
2
*x ± SEM. n = 100 to 107 hens per treatment for BW and percentage of BWR statistics, n = 6 (replicate lot means of 16 to
u_z
(g)1 ± .8b-v ± .3 C - W ± .3e-y ± .9a,u ± !6°' w ± .4 d,x ± 4b,v ± A**± jtz
30.8 ± .2 a - u 28.1 ± .3 b - v 31.0 ± 2^u
20.0 15.9 8.4 23.4 14.6 12.6 18.8 12.0 5.4 0
1793 ± l l b 1828 ± 13a 1778 ± 12b .012
(%)
20.7 ± .6W 14.2 ± .4 b,v 8.8 ± TC.W <001, <001
(n) 23 20 17 23 20 17 23 20 17 12
30.1 ± .3"^ 30.8 ± .2 a - u 29.1 ± 2h* -C.001, <001
(g) ± 20 ab ± 18* ± 21 b c ± 21 a b ± 23 bc ± 24 a ± 20 abc ± 21 b c ± 19c ± 19 t e
Actual BWR
<001, <001
1819 1771 1790 1821 1798 1865 1806 1778 1750 1780
Ground corn Ground corn Ground corn Layer Layer Layer Starter Starter Starter
Days to BWR 31.5 ± .4 ab - uv 30.5 ± .4 b c - v w 30.5 ± J1*-™ 28.5 ± .5** 29.8 ± .4C-W 26.0 ± Au 30.3 ± .4 bc - w 31.9 ± A** 30.7 ± .3 a b c . u v w 27.3 ± .3 e , v <001, <.001
IBW
Diet
^Means in columns with no common superscripts are significantly different (P<.05).
Interaction probability
1,2,3 4,5,6 7,8,9 Probability
3rd 4th 5th 3rd 4th 5th 3rd 4th 5th Fasting
Day fed
1 2 3 4 5 6 7 8 9 10 Probability3
Treatment number
Induced molt treatment
Feed per hen per day during BWR2
TABLE 2. Initial BW (IBW), BW reduction (BWR), feed consumption, and mortality during the first 35 Analysis of variance of Treatments 1 to 10: factorial analysis of Treatments 1 to 9. Tar
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1887
INDUCED MOLT BY LIMITED FEEDING
Egg production during induced molt treatment ceased after approximately 5 to 6 days during which time each treatment recorded between 1.1 and 1.4 eggs per hen housed; no significant differences were observed among treatments (Table 3, 10-treatment ANOVA). Lengthening the number of days between limited feeding reduced (P=.062) days to cessation of lay (Table 3, factorial ANOVA).
Although there were no significant differences in total hen-day production or total eggs per hen housed among the limited feeding treatments (Table 3; factorial ANOVA), highly significant differences were observed when limited feeding and fasting treatments were compared (Table 3; 10-treatment ANOVA). These data suggest that hens induced to molt by fasting return to lay more rapidly than limited feeding treatments. However, no significant treatment effect on days to 50% production was observed (Table 4). Analysis of accumulated data from the first day of induced molt to the end of the seventh postmolt period (Table 4) found no significant treatment effects for hen-day production, eggs per hen-housed, feed per egg, or percentage mortality. However, factorial analysis of postmolt data showed that limited feeding of layer diet to induce molt significantly increased feed per hen per day compared with limited feeding of the ground corn or pullet starter diets. However, covariance analysis showed initial BW significantly affected total feed per hen per day (Pi=.006) and feed per egg (P=.004) variables in the 10-treatment model. Results of covariance analysis indicated neither diet fed nor period of limited feeding to induce molt significantly affected percentage of hen-day production, eggs per hen-housed, feed per hen per day, or feed per egg. The data in Table 5 shows that induced molt treatments had no significant effect on egg weight, Haugh unit, SWUSA, specific gravity, or shell weight during postmolt lay. In the present experiment mortality was low throughout, and no significant differences were noted. DISCUSSION
The multiplicity of induced molt programs in the literature and the lack of agreement for an optimal program stems from differences in genetics, health, age, environment, and previous flock history (Swanson and Bell, 1971). Premolt egg production being a covariant of postmolt egg production (Roland and Brake, 1982) influenced the interpretation of an induced molting experiment (Zimmermann et al., 1987). The extent to which other premolt differences affect results is unknown. In the present experiment, the data in Table 2 show the lack of initial BW uniformity between treatments. Weight loss during induced molt is assumed to be a factor of bird size, fasting
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after covariance analysis was used to eliminate the effect of initial BW differences. Few changes in comparisons of treatment means occurred after covariance analysis. The correlation coefficient between initial BW and percentage of BWR calculated on the whole flock using individual hen BW was .02 (P=.490). These analyses suggested that differences in initial BW, within the range of this experiment, did not confound subsequent observations during the 35-day, induced molting period. All limited feeding treatments, with the exception of 5th day layer diet, consumed significantly less feed per hen per day than the fasted control during the 35-day-induced molting period (Table 2; 10-treatment ANOVA). The treatment factorial ANOVA (Table 2) showed that increased frequency of limited feeding increased feed per hen per day during BWR and increased feed per hen per day of developer diet fed after BWR, but only the 5th day feeding significantly (P<.05) increased total feed per hen per day during the molt period. The diet fed during the BWR phase significantly affected percentage of BWR, feed per hen per day during BWR and total feed per hen per day; hens fed layer diet lost less BW and consumed more feed. Four significant interactions between diet and period of limited feeding occurred during the 35-day molt period: 1) limited feeding of layer diet caused less BWR, especially on the 3rd and 5th day schedules; 2) feed consumed during BWR was increased by layer diet fed on the 3rd day and reduced by starter diet fed on the 4th or 5th recurring days; 3) consumption of developer diet after BWR was increased by starter diet fed every 3rd recurring day but was decreased by starter diet fed on every 5th recurring day; 4) total feed per hen per day during the molt period was increased by 5th day feeding of layer diet and reduced by 5th day feeding of starter diet. Mortality was low and nonsignificantly different among treatments during the molting period.
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ZIMMERMANN AND ANDREWS TABLE 3. Egg production during the first 35 days of induced molt treatment. Analysis of variance of Treatments 1 to 10: factorial analysis of Treatments 1 to 9
Treatment number
Induced molt treatment
Days to
Diet
of lay
3rd 4th 5th 3rd 4th 5th 3rd 4th 5th Fasting
Ground com Ground com Ground com Layer Layer Layer Starter Starter Starter
62 ± 62 ± 55 ± 6.0 ± 6.0 ± 52 ± 6.7 ± 6.0 ± 5.3 ± 5.8 ± .550
Total hen-day production
(trt 1 2 3 4 5 6 7 8 9 10 Probability 1,4,7 2,5,8 3,6,9 Probability
3rd 4th 5th
1,2,3 4,5,6 7,8,9 Probability Interaction ;probability
Ground com Layer Starter
.4 .6 .3 .4 .4 .4 .7 .5 .6 .2
1.3 ± 1.3 ± 1.4 ± 1.4 ± 1.2 ± 1.3 ± 1.4 ± 1.2 ± 1.1 ± 1.2 ± .534
Total eggs per hen housed
(%) .1 .1 .2 .1 .1 .1 .1 .1 .1 .1
3.6 ± 3.9 ± 4.4 ± 4.1 ± 3.5 ± 4.4 ± 4.1 ± 3.5 ± 3.2 ± 5.4 ± .003
.3*° .4*" .6 1 * 31* 2*° .2*° .3 1 * A* .3C .3 a
1.2 1.3 1.5 1.4 12 1.5 1.4 12 1.1 1.9
± ± ± ± ± ± ± ± ± ±
(n) .1** .l 1 * .2* .l* .1*° .1* .l b c .1^ .1° .la
.003
6.3 ± .3 6.1 ± .3 5.3 ± .2 .062
1.4 ± .1 1.3 ± .1 1.4 ± .1 .411
3.9 ± 2 3.6 ± 2 4.0 ± .3 .365
1.4 ± .1 1.3 ± .1 1.4 ± .1 .328
5.9 ± .3 5.7 ± .2 6.0 ± .4
1.3 ± .1 1.3 ± .1 1.2 ± .1
4.0 ± .3 4.0 ± 2 3.6 ± 2 284
1.4 ± .1 1.4 ± .1 1.3 ± .1 291
.770
.612
.944
.329
.143
.145
"""Means in columns with no common superscripts are significantly different (PS.05). x ± SEM. n = 6 (replicate lot means of 16 to 18 hens) per treatment.
time, and feed consumption. In the present experiment, initial BW became an uncontrolled parameter despite randomization. Covariance ANOVA and correlation analysis demonstrated that initial BW, within this genetic strain and range of BW, did not significantly affect subsequent observations during the molt period. However, the significant (P<.05) effect of initial BW on the combined data from the molt period and the 7 postmolt periods indicated initial BW did affect feed per hen per day and feed per egg. These results contradict the results of Smith et al. (1957), who observed significant differences (P5.05) in initial BW and assumed them to be inconsequential. The present results are in harmony with the findings of Baker (1981) that larger hens do not require greater BWR to achieve equal postmolt lay performance. Also, Baker et al. (1983) found variation in BWR during molt among heavier hens and did not differentiate between 27 to 30% BWR. Zimmermann et al.
(1987) were unable to detect significant (P<.05) differences in postmolt lay performance between hens fasted to 25, 30, or 35% BWR. The results of the present experiment support the conclusions of Zimmermann et al. (1987). Days to cessation of lay (Table 3) were similar between hens induced to molt by fasting or limited feeding, as found by Zimmermann et al. (1987). The reason for the significant interactions between diet and day fed that occurred during the molting period is unknown (Table 2). These interactions during molt may be of little practical importance because they disappeared when integrated with the subsequent seven periods of lay performance. In the present experiment limited feeding of layer diet caused hens to consume significantly more feed during the 35-day, moltinducing period while losing significantly less weight (Table 2). A possible explanation of these data may relate to the hens familiarity
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Day fed
Eggs per hen housed to cessation of lay
Induced molt treatment
3rd 4th 5th
1,4,7 2,5,8 3,6,9 Probability
Ground corn Layer Starter
Ground com Ground com Ground com Layer Layer Layer Starter Starter Starter
.5 .8 12 .823
65.1 ± 65.7 ± 64.7 ± .724,
.430, .312
.954
64.7 ± .9 66.3 ± .7 64.4 ± 1.1
1.1 1.4 2.1 1.0 .9 1.7 .9 1.6 2.6 1.6 .378
(%) —
64.7 ± 63.6 ± 65.8 ± 65.5 ± 67.6 ± 65.8 ± 65.0 ± 65.9 ± 62.4 ± 65.1 ± .647,
—
.312, .162
.4 .5 .6
.9 .8 1.4 .4 .8 1.0 .6 .7 .4 .8
Hen-day production
46.6 ± .6 45.1 ± .5 45.9 ± .3 .123
.379
45.7 ± 45.4 ± 46.4 ±
(n) 46.5 ± 46.2 ± 47.0 ± 45.0 ± 44.3 ± 46.0 ± 45.7 ± 45.8 ± 46.2 ± 46.5 ± .576
production
.659, .489
1.9 1.6 2.3 .227
1.8 1.6 1.2 .793
126.2 ± 126.0 ± 124.7 ± .854, 124.6 ± 127.8 ± 124.5 ± .429,
2.6 2.0 4.9 3.3 2.7 2.8 3.8 3.2 4.8 3.7 .697
126.4 ± 122.1 ± 125.4 ± 127.6 ± 128.1 ± 127.7 ± 124.5 ± 127.9 ± 121.1 ± 125.4 ± .873,
00
Eggs per hen-housed
.17
103.7 105.5 103.5 .03
.32
104.9 103.7 104.1
103.4 104.0 103.7 105.9 104.3 106.4 105.5 102.8 102.1 104.0 .08
Feed p hen p
Without and with initial BW covariance, respectively.
l x ± SEM n = 6 (replicate lot means of 16 to 18 hens) per treatment Eggs laid, feed consumed and mortality during 35 day in eggs per hen-housed, feed per egg, and mortality variables, respectively.
"•Cleans in columns with no common superscripts are significantly different (PZ.05).
Interaction probability
1,2,3 4,5,6 7,8,9 Probability
3rd 4th 5th 3rd 4th 5th 3rd 4th 5th Fasting
Day fed Diet
1 2 3 4 5 6 7 8 9 10 Probability2
Treatment number
TABLE 4. Laying performance during seven 28 day periods following induced mo Analysis of variance of Treatments 1 to 10: factorial analysis of Treatments
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3rd 4th 5th
1,4,7 2,5,8 3,6,9 Probability
2
SWUSA = shell weight per unit surface area.
(g) — ± 2 ± 2 ± .2 ± .2 ± .1 ± .2 ± .2 ± 2
(mg/cm
.613
.591
.947
.867
74.7 ± 74.6 ± 74.4 ±
74.6 ± .3 74.8 ± .3 74.9 ± .3 .877
65.7 ± .1 65.7 ± .1 65.5 ± .1 .771
74.7 ± 74.7 ± 74.7 ± 74.5 ± 75.2 ± 142 ± 74.0 ± 74.8 ± 74.4 ± 733 ± .914 74.4 ± 74.9 ± 74.4 ± .627
.5 .5 .5 .5 .5 .5 .5 .4 .5 .5
SWUSA
74.8 ± .3 75.1 ± .3 74.3 ± .3 .360
74.6 ± 75.3 ± 73.8 ± 74.3 ± 75.1 ± 74.9 ± 75.5 ± 74.9 ± 74.2 ± 75.3 ± .978
Haugh units
65.9 ± .1 65.4 ± .1 65.5 ± .1 .410
65.1 ± 2 All
6S2 ± 2
— 65.7 65.7 65.6 66.3 65.0 65.8 65.7 65.5
Egg weight
'x ± SEM. n = 6 (replicate lot means of 16 to 18 hens) per treatment.
Interaction probability
Ground corn Layer Starter
Ground corn Ground corn Ground corn Layer Layer Layer Starter Starter Starter
3rd 4th 5th 3rd 4th 5th 3rd 4th 5th Fasl
1 2 3 4 5 6 7 8 9 10 Probability
1,2,3 4,5,6 7,8,9 Probability
Diet
Induced molt treatment
Day fed
Treatment number
TABLE 5. Egg weight and quality during seven 28 day periods following induced Analysis of variance of Treatments 1 to 10: factorial analysis of Treatment
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INDUCED MOLT BY LIMITED FEEDING
ACKNOWLEDGMENTS
The authors wish to thank the poultry farm workers, technicians, and office staff at this Washington State University Puyallup Research and Extension Center for their continued support throughout this research. REFERENCES Andrews, D. K., W. D. Berry, and J. Brake, 1987. Effects of lighting program and nutrition on reproductive performance of molted Single Comb White Leghorn hens. Poultry Sci. 66:1298-1305. Baker, M, 1981. The relationship between adipose accumulation and reproductive dysfunction in Gallus domesticus. PhJ5. diss., Auburn University, Auburn, AL. Baker, M., J. Brake, and G. R. McDaniel, 1981. Total body lipid and uterine lipid changes during a forced molt of caged layers. Poultry Sci. 60:1593.(Abstr.)
Baker, M., J. Brake, and G. R. McDaniel, 1983. The relationship between body weight loss during an induced molt and postmolt egg production, egg weight, and shell quality in caged layers. Poultry Sci. 62:409-413. Bell, D. D., 1984. Fast/slow molting techniques. Calif. Poul. Lett. (Oct):2-5. Bell, D., 1989. An Egg Economics Update. Number 94, Cooperative Extension, University of California, Riverside, CA. Brake, J., J. D. Garlich, and T. A. Carter, 1984. Relationship of dietary calcium level during the prelay phase of an induced molt to postmolt performance. Poultry Sci. 63:2497-2500. Brake, J., and P. Thaxton, 1979. Physiological changes in caged layers during a forced molt 2. Gross changes in organs. Poultry Sci. 58:707-716. Brake, J., P. Thaxton, T. D. Garlich, and D. H. Sherwood, 1979. Comparison of fortified ground com and pullet grower feeding regimes during a forced molt on subsequent layer performance. Poultry Sci. 58: 785-790. Harms, R. H. 1983. Influence of protein level in the resting diet upon performance of force rested hens. Poultry Sci. 62:273-276. Len, R. E., H. Abplanalp, and E. A. Johnson, 1964. Second year production of force molted hens in the California random sample test. Poultry Sci. 43: 638-646. Mrosovsky, N., and D. F. Sherry, 1980. Animal anorexias. Science 207:837-842. Roland, D. A., Sr., and J. Brake, 1982. Influence of premolt production on postmolt performance with explanation for improvement in egg production due to force molting. Poultry Sci. 61:2473-2481. Ruszler, P. L., 1984. The keys to successful force molting. Virginia Cooperative Extension Service Publication Number 408-026, Blacksburg, VA. SAS Institute, 1985. SAS® User's Guide: Statistics, Version 5 Edition. Chapter 20. SAS Inst, Inc., Cary, NC. Smith, A. H., G. H. Bond, K. W. Ramsey, D. G. Reck, and J. E. Spoon, 1957. Size and rate of involution of the hen's reproductive organs. Poultry Sci. 36:346-353. Steel, R.GX>., and J. H. Torrie, 1960. Page 158 in Principles and Procedures of Statistics. McGraw-Hill Book Co., New York, NY. Swanson, M. H., and D. D. Bell, 1971. Field tests of forced molting practices and performance in commercial egg production flocks. Proc. XTV World Poult Congr. 3:87-97. Professional School of the Sacred Heart of Jesus, Madrid, Spain. Zimmermann, N. G., D. K. Andrews, and J. McGinnis, 1987. Comparison of several induced molting methods on subsequent performance of single comb White Leghorn hens. Poultry Sci. 66:408-417.
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with the existing feed, texture, palatability, and digestibility. Possibly the continuation of normal calcium levels, which, in turn, diluted the nutrient composition approximately 7%, offers a possible explanation for the differences in feed consumption. Within the breed, assuming that the larger birds have a larger crop and greater digestive system, the dietary differences would probably be minor compared with the energy they retain as stored fat. The retained abdominal fat pad and mesentery fat apparently supply more than adequate reserves for the limited feeding period. In summary, using either the treatment or factorial analysis, only one significant (P<.05) effect on postmolt performance was observed (Tables 4 and 5), and it was eliminated by covariance analysis with initial BW. These results suggest that nutrient density of diets used during the BWR phase of molt induced by limited feeding has little effect on subsequent laying performance. Although it has proven difficult to find an induced molt program superior to the traditional method of fasting, the 3-, 4-, and 5-day limited feeding programs offer a reasonable alternative.
1891
1990 Poultry Science 69:1883-1891 INTRODUCTION
The majority of laying hens providing table eggs in the United States are induced to molt one or more times during their productive life (Bell, 1989). The most frequently used method of inducing molt incorporates feed deprivation for BW reduction (BWR) in conjunction with decreased photoperiod (John Brake, North Carolina State University, Raleigh, NC and Don Bell, University of California, Riverside, CA, personal communication). Mrosovsky and Sherry (1980), working with wild birds, found mat weight loss is a natural physiologic phenomenon having survival value. The success of induced molt by fasting techniques to improve egg quality and numbers during the subsequent lay cycle has been researched and documented. Len et al. (1964) analyzed 2 yr of California random sample tests and associated molting and the loss of BW with feed efficiency and improved income over feed costs in the molted flocks. Brake and
'Project 0643. Animal Sciences Scientific Paper Number 8019. College of Agriculture and Home Economics Research Center, Washington State University, Pullman, WA 99164.
Thaxton (1979) postulated that weight loss of the liver, oviduct, and ovary and their subsequent rejuvenation were related to postmolt performance. Baker et al. (1981, 1983) stated that molt induced by fasting until 27 to 31% BWR produced optimal postmolt performance. Ruszler (1984) indicated that periodic feeding on recurring days equitably lowered average feed intake, induced molt, and avoided prolonged feed deprivation to reduce BW. Zimmermann et al. (1987), seeking alternative, less severe methods of inducing weight reduction during molt, tested limited feeding as a method to achieve 30% BWR. Limited feeding was achieved by allowing hens to feed ad libitum for 6 h per period on 3rd, 4th, or 5th recurring days. Results indicated that limited feeding of layer diet was as effective in obtaining acceptable postmolt performance as other methods employing fasting. Dietary composition during the post-BWR prelay interval of an induced molt may (Brake et al, 1979, 1984; Harms, 1983; Andrews et al., 1987) or may not (Bell, 1984; Zimmermann et al., 1987) affect postmolt lay performance. Perhaps the diet fed during a limited feeding induced molt could also affect subsequent lay performance.
1883
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ABSTRACT The effects of diet type and of the periodicity of limited feeding used to induce molt in 78-wk-old Leghorn hens on postmolt performance were evaluated. The experimental design was a 3 x 3 factorial arrangement of treatments, plus a fasted control. Either ground corn, a 22% protein starter, or a 15% protein layer mash diets were available ad libitum for 6 h on the 3rd, 4th, or 5th recurring days; approximately 30% BW reduction was attained after 23,20, and 17 days, respectively, of limited feeding. A pullet developer feed was then full fed until the end of the 35-day molt period. Records of lay performance during the 35-day, molt-inducing period and for the following seven, 28-day periods were kept. Many significant (P£.05) treatment effects and interactions were observed during the 35-day, molt inducing period. However, when these data were integrated with the following seven periods of data, no significant (P>.05) treatment difference or main effect interaction was observed for egg production, egg weight, feed per hen per day, Haugh units, shell weight, shell weight per unit surface area, or mortality. The results demonstrate that neither the diet fed during limited feeding nor the period of limited time feeding used to induce molt in the present experiment was of long-term importance. Further, the results demonstrate that molt induced by limited feeding is an acceptable alternative to continuous fasting. (Key words: molt, induced, limited feeding, diet, layer performance)
1884
ZEMMERMANN AND ANDREWS TABLE 1. Ingredients and calculated nutrients of diets utilized
Ingredient and analyses
Ground corn
layer diet
Starter diet -
Calculated analyses Me, kcal/kg Protein, % Calcium, % Phosphorus (total), % Methionine, %
100 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3,360 8.9 .01 .25 .17
y/uj
72.35 14.00 0 5.50 0 0 0 0 7.50 0 0 0.10 .25 .25 .05 0
54.00 16.50 7.50 2.50 5.00 5.00 5.00 1.00 .84 1.17 .22 .08 .25 .25 .05 .64
82.25 12.00 0 4.00 0 0 0 0 .30 1.00 0 0 .15 .25 .05 0
2,843 15.35 3.50 .56 .34
2,784 21.94 120 .60 .50
3,106 14.60 .80 .50 .24
'Provided the following in each kilogram of mixed diet: vitamin A, 5,614 IU; vitamin D, 1,653 IU; vitamin E, 2.2 IU; vitamin Bj2, .009 mg; riboflavin, 4.4 mg; niacin, 27.6 mg-, d-calcium pantothenate, 6.6 mg; choline chloride, 276 mg; menadione, .5 mg. 2 Provided the following in parts per million of mixed diet: manganese, 50; zinc, 50; iron, 50; copper, 5; cobalt, .5; iodine, 15.
The purpose of the present experiment was to determine if the diet fed during a 3rd, 4th, or 5th recurring day limited time feeding to induce molt had an effect on postmolt performance. Another purpose was to further demonstrate that molt induced by limited feeding is an acceptable alternative to fasting. MATERIALS AND METHODS
Materials and methods similar to Zimmermann et al. (1987) were followed as they pertain to the limited feeding to induce molt. One thousand eighty Hisex2 Single Comb White Leghorn hens 78 wk of age randomly divided into 60 replicate lots of 18 hens each in an insulated and ventilated single room light-proof house, were induced to molt during September. A replicate lot consisted of a row of nine 30.5- (width) x 40.6- (depth x
2
Pilch-Hisex, P. O. Box 438, Troutman, NC 28166.
35.6- (height) cm single deck wire cages, each containing two healthy hens, regardless of existence of previous molt. The 10 treatment groups, including a continuous fasting control, were replicated six times and equally distributed throughout the room. Prior to starting the experiment, the hens were allowed a 2-wk adjustment period after randomization plus an 18-day premolt period during which daily egg production, weekly egg weight, egg specific gravity, shell weight, and shell weight per unit surface area (SWUSA), and Haugh units were measured. Treatments, excluding the control, were designed as a 3 x 3 factorial having three diet types and three periodicitiess of recurrent feeding days as main effects. All diets were available ad libitum for 6 h every 3rd, 4th, or 5th recurring day following introduction of fasting (Day 0) until an estimated 30% BWR was obtained. The three diets fed during this time consisted of eitfier ground corn, layer mash, or starter mash (Table 1). Ground corn was the lowest nutrient density diet, whereas
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Ground corn Soybean meal Alfalfa meal Meat and bone meal Brewers dried grains Brewers yeast Fish meal Safflower oil Limestone Dicalcium phosphate Lysine DL-methionine Salt Vitamin mix* Mineral mix 2 Inert filler
Developer diet
1885
INDUCED MOLT BY LIMITED FEEDING
1960). All data were analyzed using two different models: 1) all 10 treatments (10treatment model) to compare limited feeding to fasting induced molting and 2) 3 x 3 factorial analysis (factorial model) excluding the control to determine if any combination of main effects (diet and limited feeding periodicity) interacted. Covariance and correlation analysis with initial BW were utilized to determine if initial BW difference affected results. Significant differences (P<.05) between treatment means were identified by Duncan's multiple range test or by least squares means predicted differences (PDIFF) probability procedure (SAS Institute, 1985). RESULTS
Analysis of premolt lay performance indicated no significant (P<.05) difference in any of the measured lay performance variables among treatments or main effects prior to induced molt treatment. Based on BWR from sample hens, all replicate lots were reweighed and developer feed was available ad libitum to all fasted hens after 12 days of feed deprivation and to all 3rd, 4th, and 5th recurring day limited feeding treatments after 23, 20, and 17 days, respectively (Table 2). Initial BW and percentage BWR of the whole flock were 1798 ± 7 g and 29.7 ± .1 (x ± SEM), respectively. Mean BW at the termination of the experiment was 1874 ± 7 g (x ± SEM); no significant (P^.05) treatment differences existed. However, initial BW of randomly assigned lots receiving layer diet were significantly higher than several other treatments (Table 2). Factorial analysis showed that hens fed the layer diet had significantly (P<.05) higher initial BW, lost less percentage BW, and consumed more feed during and after BWR than either the birds given the starter or corn diets suggesting a relationship between initial BW, percentage BWR and feed consumption. Covariance analysis using the 10-treatment model revealed initial BW affected BW after BWR (P<.001), percentage BWR (P=.059), and final BW (P<.001) but did not affect feed per hen per day during BWR (P=.473), feed per hen per day of developer (P*=.126) or total feed per hen per day (P=.249) during the molt inducing period. Covariance analysis with the factorial model resulted in similar probability values. Interpretation of main effects and interactions did not change
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the starter mash provided the highest nutrient density. The layer diet was that fed by Zimmermann et al. (1987) during limited feeding experimentation. Six hours (0800 to 1400h) of full feeding on the assigned recurring days was assured by appropriate placement and removal of the feed troughs. Water was available ad libitum in cup waterers. Both hens in five to six cages from each treatment were individually weighed at intervals to estimate rate of BWR. Estimated day of 30% BWR was determined within each recurrent feeding day treatment and across all diets; thus, percentage of BWR was a measured variable between diets. After BWR, the hens entered a prelay period during which all groups received pullet developer mash (Table 1) ad libitum until Day 35. The hens were then (Day 36) fed layer mash for seven, 28-day laying periods. Hens were individually weighed before and after BWR and during the seventh period on spring balances accurate to 20 g. The photoregimen for all treatments was changed from 14 h of light and 10 h of dark (14L:10D) to 8L:16D (light on at 0500 and 0800 h, respectively) on the 1st day of feed deprivation (Day 0) and remained there for 28 days, then returned 14L:10D for the remainder of the trial. Illumination was supplied by 75-W incandescent bulbs attached to the sloping ceiling 2.2 to 3.4 m (minimum and maximum, respectively) above the feed troughs providing 8.3 to 18.2 cosine-corrected lux of illumination. Egg production, feed consumption, and daily mortality were recorded and separately analyzed during each phase (i.e., BWR and prelay) of the 35-day molt induction period. During the subsequent seven 28-day postmolt periods, egg production and mortality were recorded daily and egg weight weekly. Haugh units, specific gravity, shell weight, SWUSA, and feed consumption were recorded at the end of each period. Egg measurements were taken from all eggs laid during a 24-h interval. Shell weight, SWUSA, and days to 50% production were determined as described by Zimmermann et al. (1987). Data were summarized by period and were subjected to ANOVA with a split-plot design over period using general linear model procedures (SAS Institute, 1985). Arcsin square root transformation of percentage mortality was performed prior to analysis (Steel and Torrie,
3rd 4th 5th
1,4,7 2,5,8 3,6,9 Probability
Ground corn Layer Starter
<001, <001
<.001, .001
.108
23 20 17
<001, <001
1816 ± 12 1782 ± 12 1801 ± 13 .142
.011
14.8 ± 1.2b-v 16.9 ± 12s* 12.1 ± 13 c,w <001, <001
Means in columns with no common superscripts are significantly different (P4.05); results of IBW covariance ana
12 15 18
12 15 18 12 15 18 12 15 18 23
Days fed developer diet after BWR
Without and with IBW covariance analysis, respectively.
Analysis excludes fasted hens.
3
2
*x ± SEM. n = 100 to 107 hens per treatment for BW and percentage of BWR statistics, n = 6 (replicate lot means of 16 to
u_z
(g)1 ± .8b-v ± .3 C - W ± .3e-y ± .9a,u ± !6°' w ± .4 d,x ± 4b,v ± A**± jtz
30.8 ± .2 a - u 28.1 ± .3 b - v 31.0 ± 2^u
20.0 15.9 8.4 23.4 14.6 12.6 18.8 12.0 5.4 0
1793 ± l l b 1828 ± 13a 1778 ± 12b .012
(%)
20.7 ± .6W 14.2 ± .4 b,v 8.8 ± TC.W <001, <001
(n) 23 20 17 23 20 17 23 20 17 12
30.1 ± .3"^ 30.8 ± .2 a - u 29.1 ± 2h* -C.001, <001
(g) ± 20 ab ± 18* ± 21 b c ± 21 a b ± 23 bc ± 24 a ± 20 abc ± 21 b c ± 19c ± 19 t e
Actual BWR
<001, <001
1819 1771 1790 1821 1798 1865 1806 1778 1750 1780
Ground corn Ground corn Ground corn Layer Layer Layer Starter Starter Starter
Days to BWR 31.5 ± .4 ab - uv 30.5 ± .4 b c - v w 30.5 ± J1*-™ 28.5 ± .5** 29.8 ± .4C-W 26.0 ± Au 30.3 ± .4 bc - w 31.9 ± A** 30.7 ± .3 a b c . u v w 27.3 ± .3 e , v <001, <.001
IBW
Diet
^Means in columns with no common superscripts are significantly different (P<.05).
Interaction probability
1,2,3 4,5,6 7,8,9 Probability
3rd 4th 5th 3rd 4th 5th 3rd 4th 5th Fasting
Day fed
1 2 3 4 5 6 7 8 9 10 Probability3
Treatment number
Induced molt treatment
Feed per hen per day during BWR2
TABLE 2. Initial BW (IBW), BW reduction (BWR), feed consumption, and mortality during the first 35 Analysis of variance of Treatments 1 to 10: factorial analysis of Treatments 1 to 9. Tar
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1887
INDUCED MOLT BY LIMITED FEEDING
Egg production during induced molt treatment ceased after approximately 5 to 6 days during which time each treatment recorded between 1.1 and 1.4 eggs per hen housed; no significant differences were observed among treatments (Table 3, 10-treatment ANOVA). Lengthening the number of days between limited feeding reduced (P=.062) days to cessation of lay (Table 3, factorial ANOVA).
Although there were no significant differences in total hen-day production or total eggs per hen housed among the limited feeding treatments (Table 3; factorial ANOVA), highly significant differences were observed when limited feeding and fasting treatments were compared (Table 3; 10-treatment ANOVA). These data suggest that hens induced to molt by fasting return to lay more rapidly than limited feeding treatments. However, no significant treatment effect on days to 50% production was observed (Table 4). Analysis of accumulated data from the first day of induced molt to the end of the seventh postmolt period (Table 4) found no significant treatment effects for hen-day production, eggs per hen-housed, feed per egg, or percentage mortality. However, factorial analysis of postmolt data showed that limited feeding of layer diet to induce molt significantly increased feed per hen per day compared with limited feeding of the ground corn or pullet starter diets. However, covariance analysis showed initial BW significantly affected total feed per hen per day (Pi=.006) and feed per egg (P=.004) variables in the 10-treatment model. Results of covariance analysis indicated neither diet fed nor period of limited feeding to induce molt significantly affected percentage of hen-day production, eggs per hen-housed, feed per hen per day, or feed per egg. The data in Table 5 shows that induced molt treatments had no significant effect on egg weight, Haugh unit, SWUSA, specific gravity, or shell weight during postmolt lay. In the present experiment mortality was low throughout, and no significant differences were noted. DISCUSSION
The multiplicity of induced molt programs in the literature and the lack of agreement for an optimal program stems from differences in genetics, health, age, environment, and previous flock history (Swanson and Bell, 1971). Premolt egg production being a covariant of postmolt egg production (Roland and Brake, 1982) influenced the interpretation of an induced molting experiment (Zimmermann et al., 1987). The extent to which other premolt differences affect results is unknown. In the present experiment, the data in Table 2 show the lack of initial BW uniformity between treatments. Weight loss during induced molt is assumed to be a factor of bird size, fasting
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after covariance analysis was used to eliminate the effect of initial BW differences. Few changes in comparisons of treatment means occurred after covariance analysis. The correlation coefficient between initial BW and percentage of BWR calculated on the whole flock using individual hen BW was .02 (P=.490). These analyses suggested that differences in initial BW, within the range of this experiment, did not confound subsequent observations during the 35-day, induced molting period. All limited feeding treatments, with the exception of 5th day layer diet, consumed significantly less feed per hen per day than the fasted control during the 35-day-induced molting period (Table 2; 10-treatment ANOVA). The treatment factorial ANOVA (Table 2) showed that increased frequency of limited feeding increased feed per hen per day during BWR and increased feed per hen per day of developer diet fed after BWR, but only the 5th day feeding significantly (P<.05) increased total feed per hen per day during the molt period. The diet fed during the BWR phase significantly affected percentage of BWR, feed per hen per day during BWR and total feed per hen per day; hens fed layer diet lost less BW and consumed more feed. Four significant interactions between diet and period of limited feeding occurred during the 35-day molt period: 1) limited feeding of layer diet caused less BWR, especially on the 3rd and 5th day schedules; 2) feed consumed during BWR was increased by layer diet fed on the 3rd day and reduced by starter diet fed on the 4th or 5th recurring days; 3) consumption of developer diet after BWR was increased by starter diet fed every 3rd recurring day but was decreased by starter diet fed on every 5th recurring day; 4) total feed per hen per day during the molt period was increased by 5th day feeding of layer diet and reduced by 5th day feeding of starter diet. Mortality was low and nonsignificantly different among treatments during the molting period.
1888
ZIMMERMANN AND ANDREWS TABLE 3. Egg production during the first 35 days of induced molt treatment. Analysis of variance of Treatments 1 to 10: factorial analysis of Treatments 1 to 9
Treatment number
Induced molt treatment
Days to
Diet
of lay
3rd 4th 5th 3rd 4th 5th 3rd 4th 5th Fasting
Ground com Ground com Ground com Layer Layer Layer Starter Starter Starter
62 ± 62 ± 55 ± 6.0 ± 6.0 ± 52 ± 6.7 ± 6.0 ± 5.3 ± 5.8 ± .550
Total hen-day production
(trt 1 2 3 4 5 6 7 8 9 10 Probability 1,4,7 2,5,8 3,6,9 Probability
3rd 4th 5th
1,2,3 4,5,6 7,8,9 Probability Interaction ;probability
Ground com Layer Starter
.4 .6 .3 .4 .4 .4 .7 .5 .6 .2
1.3 ± 1.3 ± 1.4 ± 1.4 ± 1.2 ± 1.3 ± 1.4 ± 1.2 ± 1.1 ± 1.2 ± .534
Total eggs per hen housed
(%) .1 .1 .2 .1 .1 .1 .1 .1 .1 .1
3.6 ± 3.9 ± 4.4 ± 4.1 ± 3.5 ± 4.4 ± 4.1 ± 3.5 ± 3.2 ± 5.4 ± .003
.3*° .4*" .6 1 * 31* 2*° .2*° .3 1 * A* .3C .3 a
1.2 1.3 1.5 1.4 12 1.5 1.4 12 1.1 1.9
± ± ± ± ± ± ± ± ± ±
(n) .1** .l 1 * .2* .l* .1*° .1* .l b c .1^ .1° .la
.003
6.3 ± .3 6.1 ± .3 5.3 ± .2 .062
1.4 ± .1 1.3 ± .1 1.4 ± .1 .411
3.9 ± 2 3.6 ± 2 4.0 ± .3 .365
1.4 ± .1 1.3 ± .1 1.4 ± .1 .328
5.9 ± .3 5.7 ± .2 6.0 ± .4
1.3 ± .1 1.3 ± .1 1.2 ± .1
4.0 ± .3 4.0 ± 2 3.6 ± 2 284
1.4 ± .1 1.4 ± .1 1.3 ± .1 291
.770
.612
.944
.329
.143
.145
"""Means in columns with no common superscripts are significantly different (PS.05). x ± SEM. n = 6 (replicate lot means of 16 to 18 hens) per treatment.
time, and feed consumption. In the present experiment, initial BW became an uncontrolled parameter despite randomization. Covariance ANOVA and correlation analysis demonstrated that initial BW, within this genetic strain and range of BW, did not significantly affect subsequent observations during the molt period. However, the significant (P<.05) effect of initial BW on the combined data from the molt period and the 7 postmolt periods indicated initial BW did affect feed per hen per day and feed per egg. These results contradict the results of Smith et al. (1957), who observed significant differences (P5.05) in initial BW and assumed them to be inconsequential. The present results are in harmony with the findings of Baker (1981) that larger hens do not require greater BWR to achieve equal postmolt lay performance. Also, Baker et al. (1983) found variation in BWR during molt among heavier hens and did not differentiate between 27 to 30% BWR. Zimmermann et al.
(1987) were unable to detect significant (P<.05) differences in postmolt lay performance between hens fasted to 25, 30, or 35% BWR. The results of the present experiment support the conclusions of Zimmermann et al. (1987). Days to cessation of lay (Table 3) were similar between hens induced to molt by fasting or limited feeding, as found by Zimmermann et al. (1987). The reason for the significant interactions between diet and day fed that occurred during the molting period is unknown (Table 2). These interactions during molt may be of little practical importance because they disappeared when integrated with the subsequent seven periods of lay performance. In the present experiment limited feeding of layer diet caused hens to consume significantly more feed during the 35-day, moltinducing period while losing significantly less weight (Table 2). A possible explanation of these data may relate to the hens familiarity
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Day fed
Eggs per hen housed to cessation of lay
Induced molt treatment
3rd 4th 5th
1,4,7 2,5,8 3,6,9 Probability
Ground corn Layer Starter
Ground com Ground com Ground com Layer Layer Layer Starter Starter Starter
.5 .8 12 .823
65.1 ± 65.7 ± 64.7 ± .724,
.430, .312
.954
64.7 ± .9 66.3 ± .7 64.4 ± 1.1
1.1 1.4 2.1 1.0 .9 1.7 .9 1.6 2.6 1.6 .378
(%) —
64.7 ± 63.6 ± 65.8 ± 65.5 ± 67.6 ± 65.8 ± 65.0 ± 65.9 ± 62.4 ± 65.1 ± .647,
—
.312, .162
.4 .5 .6
.9 .8 1.4 .4 .8 1.0 .6 .7 .4 .8
Hen-day production
46.6 ± .6 45.1 ± .5 45.9 ± .3 .123
.379
45.7 ± 45.4 ± 46.4 ±
(n) 46.5 ± 46.2 ± 47.0 ± 45.0 ± 44.3 ± 46.0 ± 45.7 ± 45.8 ± 46.2 ± 46.5 ± .576
production
.659, .489
1.9 1.6 2.3 .227
1.8 1.6 1.2 .793
126.2 ± 126.0 ± 124.7 ± .854, 124.6 ± 127.8 ± 124.5 ± .429,
2.6 2.0 4.9 3.3 2.7 2.8 3.8 3.2 4.8 3.7 .697
126.4 ± 122.1 ± 125.4 ± 127.6 ± 128.1 ± 127.7 ± 124.5 ± 127.9 ± 121.1 ± 125.4 ± .873,
00
Eggs per hen-housed
.17
103.7 105.5 103.5 .03
.32
104.9 103.7 104.1
103.4 104.0 103.7 105.9 104.3 106.4 105.5 102.8 102.1 104.0 .08
Feed p hen p
Without and with initial BW covariance, respectively.
l x ± SEM n = 6 (replicate lot means of 16 to 18 hens) per treatment Eggs laid, feed consumed and mortality during 35 day in eggs per hen-housed, feed per egg, and mortality variables, respectively.
"•Cleans in columns with no common superscripts are significantly different (PZ.05).
Interaction probability
1,2,3 4,5,6 7,8,9 Probability
3rd 4th 5th 3rd 4th 5th 3rd 4th 5th Fasting
Day fed Diet
1 2 3 4 5 6 7 8 9 10 Probability2
Treatment number
TABLE 4. Laying performance during seven 28 day periods following induced mo Analysis of variance of Treatments 1 to 10: factorial analysis of Treatments
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3rd 4th 5th
1,4,7 2,5,8 3,6,9 Probability
2
SWUSA = shell weight per unit surface area.
(g) — ± 2 ± 2 ± .2 ± .2 ± .1 ± .2 ± .2 ± 2
(mg/cm
.613
.591
.947
.867
74.7 ± 74.6 ± 74.4 ±
74.6 ± .3 74.8 ± .3 74.9 ± .3 .877
65.7 ± .1 65.7 ± .1 65.5 ± .1 .771
74.7 ± 74.7 ± 74.7 ± 74.5 ± 75.2 ± 142 ± 74.0 ± 74.8 ± 74.4 ± 733 ± .914 74.4 ± 74.9 ± 74.4 ± .627
.5 .5 .5 .5 .5 .5 .5 .4 .5 .5
SWUSA
74.8 ± .3 75.1 ± .3 74.3 ± .3 .360
74.6 ± 75.3 ± 73.8 ± 74.3 ± 75.1 ± 74.9 ± 75.5 ± 74.9 ± 74.2 ± 75.3 ± .978
Haugh units
65.9 ± .1 65.4 ± .1 65.5 ± .1 .410
65.1 ± 2 All
6S2 ± 2
— 65.7 65.7 65.6 66.3 65.0 65.8 65.7 65.5
Egg weight
'x ± SEM. n = 6 (replicate lot means of 16 to 18 hens) per treatment.
Interaction probability
Ground corn Layer Starter
Ground corn Ground corn Ground corn Layer Layer Layer Starter Starter Starter
3rd 4th 5th 3rd 4th 5th 3rd 4th 5th Fasl
1 2 3 4 5 6 7 8 9 10 Probability
1,2,3 4,5,6 7,8,9 Probability
Diet
Induced molt treatment
Day fed
Treatment number
TABLE 5. Egg weight and quality during seven 28 day periods following induced Analysis of variance of Treatments 1 to 10: factorial analysis of Treatment
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INDUCED MOLT BY LIMITED FEEDING
ACKNOWLEDGMENTS
The authors wish to thank the poultry farm workers, technicians, and office staff at this Washington State University Puyallup Research and Extension Center for their continued support throughout this research. REFERENCES Andrews, D. K., W. D. Berry, and J. Brake, 1987. Effects of lighting program and nutrition on reproductive performance of molted Single Comb White Leghorn hens. Poultry Sci. 66:1298-1305. Baker, M, 1981. The relationship between adipose accumulation and reproductive dysfunction in Gallus domesticus. PhJ5. diss., Auburn University, Auburn, AL. Baker, M., J. Brake, and G. R. McDaniel, 1981. Total body lipid and uterine lipid changes during a forced molt of caged layers. Poultry Sci. 60:1593.(Abstr.)
Baker, M., J. Brake, and G. R. McDaniel, 1983. The relationship between body weight loss during an induced molt and postmolt egg production, egg weight, and shell quality in caged layers. Poultry Sci. 62:409-413. Bell, D. D., 1984. Fast/slow molting techniques. Calif. Poul. Lett. (Oct):2-5. Bell, D., 1989. An Egg Economics Update. Number 94, Cooperative Extension, University of California, Riverside, CA. Brake, J., J. D. Garlich, and T. A. Carter, 1984. Relationship of dietary calcium level during the prelay phase of an induced molt to postmolt performance. Poultry Sci. 63:2497-2500. Brake, J., and P. Thaxton, 1979. Physiological changes in caged layers during a forced molt 2. Gross changes in organs. Poultry Sci. 58:707-716. Brake, J., P. Thaxton, T. D. Garlich, and D. H. Sherwood, 1979. Comparison of fortified ground com and pullet grower feeding regimes during a forced molt on subsequent layer performance. Poultry Sci. 58: 785-790. Harms, R. H. 1983. Influence of protein level in the resting diet upon performance of force rested hens. Poultry Sci. 62:273-276. Len, R. E., H. Abplanalp, and E. A. Johnson, 1964. Second year production of force molted hens in the California random sample test. Poultry Sci. 43: 638-646. Mrosovsky, N., and D. F. Sherry, 1980. Animal anorexias. Science 207:837-842. Roland, D. A., Sr., and J. Brake, 1982. Influence of premolt production on postmolt performance with explanation for improvement in egg production due to force molting. Poultry Sci. 61:2473-2481. Ruszler, P. L., 1984. The keys to successful force molting. Virginia Cooperative Extension Service Publication Number 408-026, Blacksburg, VA. SAS Institute, 1985. SAS® User's Guide: Statistics, Version 5 Edition. Chapter 20. SAS Inst, Inc., Cary, NC. Smith, A. H., G. H. Bond, K. W. Ramsey, D. G. Reck, and J. E. Spoon, 1957. Size and rate of involution of the hen's reproductive organs. Poultry Sci. 36:346-353. Steel, R.GX>., and J. H. Torrie, 1960. Page 158 in Principles and Procedures of Statistics. McGraw-Hill Book Co., New York, NY. Swanson, M. H., and D. D. Bell, 1971. Field tests of forced molting practices and performance in commercial egg production flocks. Proc. XTV World Poult Congr. 3:87-97. Professional School of the Sacred Heart of Jesus, Madrid, Spain. Zimmermann, N. G., D. K. Andrews, and J. McGinnis, 1987. Comparison of several induced molting methods on subsequent performance of single comb White Leghorn hens. Poultry Sci. 66:408-417.
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with the existing feed, texture, palatability, and digestibility. Possibly the continuation of normal calcium levels, which, in turn, diluted the nutrient composition approximately 7%, offers a possible explanation for the differences in feed consumption. Within the breed, assuming that the larger birds have a larger crop and greater digestive system, the dietary differences would probably be minor compared with the energy they retain as stored fat. The retained abdominal fat pad and mesentery fat apparently supply more than adequate reserves for the limited feeding period. In summary, using either the treatment or factorial analysis, only one significant (P<.05) effect on postmolt performance was observed (Tables 4 and 5), and it was eliminated by covariance analysis with initial BW. These results suggest that nutrient density of diets used during the BWR phase of molt induced by limited feeding has little effect on subsequent laying performance. Although it has proven difficult to find an induced molt program superior to the traditional method of fasting, the 3-, 4-, and 5-day limited feeding programs offer a reasonable alternative.
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