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Effect of Lighting Program and Nutrition on Feather Replacement of Molted Single Comb White Leghorn Hens1,2
Effect of Lighting Program and Nutrition on Feather Replacement of Molted Single Comb White Leghorn Hens 1 ' 2 D. K. ANDREWS Department of Animal Sciences, Washington State University, Western Washington Research and Extension Center, Puyallup, Washington 98371-4998 and W. D. BERRY and J. BRAKE Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27695-7608 (Received for publication March 6, 1987) ABSTRACT This experiment concerned the induced molt of 320 60-wk old Single Comb White Leghorn hens placed two per cage in two adjoining sections of a light-tight, fan-ventilated poultry building. Treatments compared were: 1) lighting program: Washington (WSU) re. North Carolina (NCSU). The WSU program used 8 h light/day for 28 days beginning 7 days before fast. The NCSU program used continuous light for 7 days prior to fast, followed by 12 h light/day for 21 days. The light portion of the photoperiod was then increased in steps in both treatments to 16 h. 2) Molt diet: cracked corn (CC) vs. 16% protein molt ration (MR) for 14 days. 3) Laying diet. A 14% protein mash calculated to contain .60% or .65% total sulfur amino acids (TSAA) or ascorbic acid (AA) at 0 or 50 ppm added to the laying mash. Day 1 was designated as the first day of photoperiod modification. Primary and secondary feather loss and subsequent primary feather growth were all significantly increased by the WSU light program at 56, 84, and 112 days. Total and average growth of new primaries was significantly increased by MR at 56 days and total primary feather growth by .65% TSAA at 112 days. No effects due to AA were observed. Photoperiod had the greatest effect on molt per se, with MR and .65% TSAA increasing early and late growth, respectively. (Key words: induced molt, primary feather replacement, photoperiod, molt nutrition) 1987 Poultry Science 66:1635-1639 INTRODUCTION
Molting is a process that involves two phenomena, the shedding of the old part (ecdysis) of the feather, and the growth of a new one (endysis). Watson (1963a) can be quoted: "the dropping of the old generation of feathers is brought about by the initiation of growth of the new generation, which pushes the old feathers passively out of the follicles. Molt in birds is consequently a single growth process actively 'Washington State University Scientific Paper Number 7636, and Washington State University Research Project Number 0643, Washington State University, College of Agriculture and Home Economics, Western Washington Research and Extension Center, Puyallup, WA 98371-4998. Paper Number 10874 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 276957601. 2 A portion of these data was presented at the 74th Annual Meeting of the Poultry Science Association, Inc., July 30, 1985, Ames, IA. Research was conducted while the senior author was on sabbatical leave at North Carolina State University. The use of trade names in this paper does not constitute endorsement of products mentioned nor criticism of similar products not mentioned.
concerned only with the production of a new generation of feathers." "Energy is expended only in producing the incoming generation of feathers and not in shedding the old generation", Watson (1963b). Feather loss and growth during an induced molt is controlled by the management methods used to induce molt and the nutrition provided to meet the requirements of feather growth. Brake (1982) and Decuypere and Verheyen (1986) reviewed molt induction, performance, and the physiological changes and interactions that are known to occur involving the hypothalamus, hypophysis, thyroid, ovary, and adrenal cortex of laying hens proceeding through an induced molt. An increase in the ratio of thyroid hormones to estrogen is probably of crucial importance for inducing new feather formation and could explain the occurrence of feather replacement coincidental with cessation of egg production and cessation of feather replacement coincidental with onset of ovarian recrudescence. Sturkie (1986) notes that the elevation of plasma thyroxine may not only play a role
1635
1636
ANDREWS ET AL.
in the induction of molt, but may also be required for its thermogenic effect during the period of heavy feather loss. Management factors that are used to induce molt and control the length of the molting period must therefore act through effects on the reproductive and associated endocrine systems. Riley and Byerly (1943) noted that the reduction of light in the photoperiod caused a marked loss of feathers and they related completion of primary wing molt to return of production. Hansen (1966, 1969) reported that reduction of light in the photoperiod to 8 h/day 2 wk prior to, during, and after feed withdrawal resulted in a more complete molt and that continuing the reduction of light in the photoperiod kept hens out of production. Brake and Thaxton (1982) found that reducing the number of hours of light during the molting period hastened the initiation of the molting process as well as reducing mortality. Obviously, photoperiod and nutritional deprivation as molt induction methods have similar modes of action through the hypothalamichypophyseal axis, with modulation of the ovary being the pivotal endocrine event. The physiological importance of the extent of feather replacement has been documented by several authors. Krueger et al. (1977), working with turkeys, noted a positive and highly significant correlation between the number of flight feathers missing or replaced by the end of 8 wk of light restriction and the number of days to first egg. Harms (1983) determined that the number of days for a hen to return to production after the resting period was directly related (r = .98) to the number of primaries molted.This suggests that the extent of molt is controlled by the duration of ovarian regression. Feathers have been shown to be protein based, with sulfur-containing amino acids a major component. Availability of crude protein and specific amino acids during molt would be expected to affect the progress of feather replacement (Brake, 1982). Richards (1977) reported that heat stress is confounded with feather condition since the metabolic rate of poorly feathered birds averages some 60% above that of controls. Pardue and Thaxton (1982) noted that ascorbic acid (AA) improved livability in broilers during heat stress. Thus it was thought that some benefit from dietary AA might occur with birds just completing a molt if temperatures increased dramatically during this experiment. The objective of this study was to compare the effects of lighting
program, molt diet, total sulfur amino acids (TSAA) in the postmolt layer diet, and A A in the postmolt layer diet loss of primary and secondary remiges (flight feathers) and rate of regrowth of primary feathers. MATERIALS AND METHODS
Three hundred twenty DeKalb XL, Single Comb White Leghorn (SCWL) hens, 60 wk of age, in 80% production were placed two per cage, five cages per replicate lot, in an insulated, fan-ventilated, light-tight building. The building was divided in half, with a light-proof partition that allowed air movement between the two sections. Both sections shared a common air inlet and the fan ventilation was managed such that the environment of the two sections was the same. Two weeks were allotted for acclimation and sorting for uniformity. The experiment started May 29. The production data, lighting, and diet programs were as described by Andrews et al. (1987). In brief, the North Carolina State University (NCSU) lighting program was initiated with continuous light for 7 days (beginning on Day 1) prior to feed withdrawal, followed by 21 days of a 12-h light: 12-h dark photoperiod, then increased to a 14-h light: 10 h dark photoperiod from Day 29 to Day 56. The Washington State University (WSU) lighting program reduced the light portion on the photoperiod to 8 h for 28 days, beginning 7 days prior to feed withdrawal (Day 1). The light portion of the photoperiod, from Day 29 to Day 42, was increased to 10 h, then advanced to 13 h from Day 43 to Day 56. On Day 57, the light period of both treatments was increased to 15 h and to 16 h on Day 85 for the remainder of the experiment. Following a 14-day fast, either cracked corn (CC) or molt ration (MR) diets were fed from Day 22 to Day 35, at which time 14% protein corn-soy laying mash diets containing 3.5% calcium and .06% total phosphorus with either .60% or .65% TSAA, with or without 50 ppm of supplemental AA, were fed for the remainder of the experiment. Recording of feather molt was confined to the wing flight feathers; body molt was not measured. Primary and secondary wing feathers were counted on the 56th, 84th, and 112th days. To facilitate identification, primary feathers on the right wing were stained a light yellow with picric acid diluted in water (Fisher Scientific, Raleigh, NC). Individual primary feathers were
LIGHT, NUTRITION, MOLT, AND FEATHER
then measured by placing a ruler at the base of each flight feather and recording the length of the shaft in millimeters. Order of molt was taken from primary feather Number 1 beside the axial feather and progressing outward to the wing tip (Card and Nesheim, 1966). Secondary feather count began at the axial feather and proceeded back towards the body. Lucas and Stettenheim (1972) list 17 secondary feathers, five of which are short, blending with the wing coverts. Card and Nesheim (1966) list 14 secondaries present in the domestic hen. In this experiment we considered 16 secondary wing feathers and found only one hen which had molted as many as 15. Feather counts were made by checking the first 9 flight and 16 secondary feathers on the right wing of the same four hens in each lot. The presence or absence of the axial feather was recorded. The following criteria were used (Andrews and Zimmermann, 1983) in assessing primary wing molt: 1) Empty follicles were recorded as 00.0 on the score sheet and were counted as they occupied a space and represented a time in a sequence. 2) The few feathers that were in the growth process when the experiment began were considered as a part of the molt. They were measured in millimeters (mm) and counted. 3) Faded, worn feathers, or broken stubs were considered as old feathers and were not counted. Feather counts and measurements were analyzed for percent primary and secondary feather loss and primary feather growth. Results were subjected to analysis of variance using a 2 x 2 x 2 x 2 factorial arrangement of treat-
1637
ments (160 birds/main effect mean; 20 birds/ subcell) using the SAS Institute Inc. (1982) general linear models procedures. The main effects were lighting program, molt diet, laying diet TSAA, and laying diet AA. Each sample time was analyzed individually. Percentage data were subjected to arcsin transformation prior to analysis. Statements of statistical significance are based on P<.05. RESULTS AND DISCUSSION
It is important to note that lighting control in this experiment began on Day 1, whereas feed restriction was started Day 8. This allowed normal production to continue while the birds were being photosensitized for a more complete and rapid molt following fasting. Lighting program caused the greatest effect among the factors studied (Table 1). The WSU program hens given 42 days of reduced light in the photoperiod (8 h x 28 days; 10 h x 14 days) had by the 56th day significantly more primary and secondary feather loss than the NCSU program hens (24 h x 7 days; 12 h x 21 days; 14 h x 14 days). This amounted to WSU treatment loss of 29% more primaries and 35% more secondaries than in the NCSU treatment; however, the primaries grown by turkeys in the WSU treatment were significantly shorter (11%). Although primary and secondary feather loss essentially ceased at 56 days, growth of primary feathers continued rapidly through 84 days. Primary growth increased, with WSU treatment birds experiencing a 67% increase vs.
TABLE 1. Effects of two different lighting programs at Washington State University (WSU) and North Carolina State University (NCSU) on number of primary and secondary feathers lost, generation of new primary feather growth and average length of primary feathers grown1 Primaries lost Day
WSU
56 84 112
6.2* 6.4* 6.4*
NCSU
Total primary growth WSU
NCSU
60.9* 102.1* 110.3*
52.3D
(no) 4.8 C
5.1 1
Primary length
Secondaries lost
WSU
NCSU
WSU
9.9° 15.9* 17.1*
11.0* 15.5 b 16.7 b
12.3* 13.1* 13.1*
NCSU
9.1b 10.1b 10.1b
(cm) 78.3 b 85.8 b
ab • ' Values with superscripts that differ within the same horizontal row and category are significantly different (P<.05). 'The WSU lighting program decreased light in the photoperiod premolt to 8 h for 1 wk, continued at 8 h during molt for 3 wk, then 10 h for 2 wk, 13 h for 2 wk, 15 h for 4 wk, and 16 h for the remainder of the experiment. The NCSU program increased lighting photoperiod premolt to 24 h for 1 wk, then 12 h for 3 wk, 14 h for 4 wk, 15 h for 4 wk, and 16 h for the remainder of the experiment.
1638
ANDREWS ET AL. TABLE 2. Effects of molt diets of cracked corn (CC) or molt ration (MR) upon number of primary and secondary feathers lost and regrowth of primaries1 Primaries lost
Day
CC
56 84 112
5.6" 5.9" 5.9"
MR (.no; 5.4" 5.6" 5.6"
Total primary growth CC
MR
53.3 b 91.4" 99.5"
60.0" 88.6" 96.1"
Primary length CC
Seco ndaries lost
MR
CC
11.3" 15.8" 16.9"
11.1" 12.0" 12.0"
(cm)
9.5 b 15.6" 16.9"
MR (no) 10.3" 11.1" 11.2"
ab ' Values with superscripts that differ within the same horizontal row and category are significantly different (P<.05). 1
CC and MR fed for 14 days following completion of weight loss period.
the NCSU treatment birds increase of 41%. Growth rates from the 84th through 112th day were identical at 1.2 cm/primary in both treatments. This resulted in a significant difference in both the number of primaries lost and the length of feathers grown for the two treatments, with the reduced WSU photoperiod encouraging primary and secondary feather replacement. Longer photoperiods, as supplied by the NCSU program, significantly reduced primary feather loss by 20%, total primary feather growth by 22%, and secondary feather loss by 23%. This reduction in feather replacement needs coincides with the time during which birds in this treatment gained 7.2 eggs over those on the WSU program with reduced light in the photoperiod (Andrews et al., 1987). This was due to a shortened period of ovarian regression, which allowed fewer feathers to be molted. This, in turn, reduced dietary requirements for feather replacement and provided nutrients for earlier onset of lay. These results give support to the recommendations of
Brake and Carey (1983) that longer photoperiods contribute to increased egg production. A comparison of molt diet effects is given in Table 2. Molt diets fed from Day 22 to Day 35 did not affect the number of primary or secondary feathers molted at 56 days. Growth of primaries as measured by total growth, 60 vs. 53.3 cm, and average length increase, 11.3 vs. 9.5 cm, were both significantly higher for the MR than for the CC treatment at 56 days. By 84 days primary feather length of birds on the CC diet had essentially equalled that of birds on the MR diet. At 112 days primary feather length was identical at 16.9 cm for birds on the two diets. Further growth would be expected, as Lucas and Stettenheim (1972) report that mature SCWL hen primary wing feathers vary between 20.4 and 15.2 cm in length from the 1st through 8th feather. This would average to 18.7 cm and is in keeping with other results at this station. Although primary feather loss essentially stopped at 56 days, one more secondary
TABLE 3. Effects of higher level of total sulfur amino acids in laying rations on mean growth and percent of primary and secondary feathers molted1 % Primaries: molted Wk
600 mg
56 84 112
53.2" 56.1" 55.5"
Total primary growth
650 mg
600 mg
650 mg
57.2" 59.4" 60.0"
54.1" 86.1" 93.2 b
59.1" 93.9" 102.4"
do)
Primary growth (x) 600 mg (uu) 10.4" 15.6" 16.9"
Secondaries: molted
650 mg
600 mg
650 mg
10.5" 15.8" 17.0"
65.2" 70.3" 70.3"
68.8" 74.3" 74.7"
ab ' Values with superscripts that differ within the same horizontal row and category are significantly different (P<.05). 1 Total sulfur amino acid level of 600 and 650 mg of methionine and cystine/kg diet calculated for laying rations.
LIGHT, NUTRITION, MOLT, AND FEATHER
was lost before the 84th day in both the light and molt diet treatments. The MR treatment birds resumed egg production earlier (Andrews et al., 1987) due to an early replacement of feathers. Once egg production commenced, the birds rate of feather growth slowed, thus the more rapid early growth in the MR treatment is indicative of availability of nutrients. The effect of a higher level of TSAA in the laying diet is shown in Table 3. The addition of 50 mg of methionine, raising the TSAA complement in the laying ration to 650 mg/kg, produced a significantly higher total primary feather growth at 112 days. This is in keeping with the report by Brake (1982). As the ration was not fed until the 35th day, effects might be expected to be delayed. The addition of ascorbic acid (50 ppm) to the diets did not significantly affect wing molt. Birds without dietary AA molted 58.6% of primary wing feathers compared with 56.9% for those given 50 ppm of dietary AA. Corresponding secondary feather molt figures were 73.4% vs. 71.6%. Taken together, these data indicate the complexity of the effects of lighting program and nutrition as they relate to the progression of molt. A reduced period of ovarian regression, mediated through the longer light portion of the NCSU photoperiods, produced significantly less feather loss and presumably lower nutrient requirements and allowed birds to resume lay earlier. During the period of molt, the use of a balanced MR increased early feather growth when compared with effects of feeding a CC diet, thus providing additional nutrients during the earlier onset of lay. The use of additional methionine in the laying ration hastened completion of primary feather growth. These results, and the data of Andrews et al. (1987) suggest that maximizing feather loss does not maximize egg production. Optimum production is achieved by a short period of complete reproductive regression and a rapid return to lay. These objectives may be met by a proper combination of photoperiod and nutritional management.
ACKNOWLEDGMENTS
The authors express appreciation to Jimmy Hinnant for care of the poultry and to Grace Brockman for technical assistance. The authors
1639
thank Hoffmann-LaRoche for the gift of ascorbic acid. REFERENCES Andrews, D. K., W. D. Berry, and J. Brake, 1987. Effect of lighting program and nutrition on reproductive performance of molted Single Comb White Leghorn hens. Poultry Sci. 66:1298-1305. Andrews, D. K., and N. G. Zimmermann, 1983. Wing molt observations on laying hens after ahemeral light treatments. Poultry Sci. 62:1373. (Abstr.) Brake, J. T., 1982. Physiological, nutritional, and management aspects of artificially induced molting in poultry. Vol. 1. Pages 306-330 in: Proc. Symp. Management of Food Producing Anim. May 5-7. W. Lafayette, IN. Brake, J. T., and J. B. Carey, 1983. Induced molting of commercial layers. N.C. Agric. Ext. Serv. Poultry Sci. and Tech. Guide No. 10. Raleigh, NC. Brake, J., and P. Thaxton, 1982. Comparative effect of photoperiod modification and/or fasting with a short period without water on physiological and performance parameters associated with molt in SCWL hens. Poultry Sci. 61:1423. (Abstr.) Card, L. E., and M. C. Nesheim, 1966. Poultry Production. 10th ed. Lea and Febiger, Philadelphia, PA. Decuypere, E., andG. Verheyen, 1986. Physiological basis of induced molting and tissue regeneration in fowl. World's Poult. Sci. J. 42:56-68. Hansen, R. S., 1966. Reducing light to facilitate the induced rest (forced molt). Poultry Sci. 45:1089. (Abstr.) Hansen, R. S., 1969. The biology: how, what, when and why of recycling. Proc. Ohio Market Egg Day Program, January 28. The Ohio State Univ., Columbus, OH. Harms, R. H., 1983. The relationship of molted primaries of commercial layers to first egg after molt. Poultry Sci. 62:1123-1124. Krueger, K. K., T. M. Fergerson, J. A. Owen, and C. E. Krueger, 1977. The influence of feather loss on subsequent egg production in force molted turkey hens. Poultry Sci. 56:35. (Abstr.) Lucas, A. L.,andP. R. Stettenheim, 1972. Avian AnatomyIntegument. Part 1. Agric. Handbook 362. US Gov. Print. Off., Washington, DC. Pardue, S. L., and J. P. Thaxton, 1982. Enhanced livability and improved immunological responsiveness in ascorbic acid supplemented cockerels during acute heat stress. Poultry Sci. 61:1522. (Abstr.) Richards, S. A., 1977. The influence of loss of plumage on temperature regulation in laying hens. J. Agric. Soc. Cambridge 89:393-398. Riley, G. M., and T. C. Byeriy, 1943. The influence of increased light on progress of molt and egg production in yearling Rhode Island Red hens. Poultry Sci. 22:301-306. SAS Institute, Inc., 1982. SAS User's Guide: Statistics, 1982 Ed. SAS Institute, Inc., Cary, NC. Sturkie, P. D., 1986. Avian physiology. 4th ed., Springer Verlag, New York, NY. Watson, G. E., 1963a. The mechanism of feather replacement during natural molt. Auk 80:486-495. Watson, G. E., 1963b. Feather replacement in birds. Science 139:50. (Abstr.)
Molting is a process that involves two phenomena, the shedding of the old part (ecdysis) of the feather, and the growth of a new one (endysis). Watson (1963a) can be quoted: "the dropping of the old generation of feathers is brought about by the initiation of growth of the new generation, which pushes the old feathers passively out of the follicles. Molt in birds is consequently a single growth process actively 'Washington State University Scientific Paper Number 7636, and Washington State University Research Project Number 0643, Washington State University, College of Agriculture and Home Economics, Western Washington Research and Extension Center, Puyallup, WA 98371-4998. Paper Number 10874 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 276957601. 2 A portion of these data was presented at the 74th Annual Meeting of the Poultry Science Association, Inc., July 30, 1985, Ames, IA. Research was conducted while the senior author was on sabbatical leave at North Carolina State University. The use of trade names in this paper does not constitute endorsement of products mentioned nor criticism of similar products not mentioned.
concerned only with the production of a new generation of feathers." "Energy is expended only in producing the incoming generation of feathers and not in shedding the old generation", Watson (1963b). Feather loss and growth during an induced molt is controlled by the management methods used to induce molt and the nutrition provided to meet the requirements of feather growth. Brake (1982) and Decuypere and Verheyen (1986) reviewed molt induction, performance, and the physiological changes and interactions that are known to occur involving the hypothalamus, hypophysis, thyroid, ovary, and adrenal cortex of laying hens proceeding through an induced molt. An increase in the ratio of thyroid hormones to estrogen is probably of crucial importance for inducing new feather formation and could explain the occurrence of feather replacement coincidental with cessation of egg production and cessation of feather replacement coincidental with onset of ovarian recrudescence. Sturkie (1986) notes that the elevation of plasma thyroxine may not only play a role
1635
1636
ANDREWS ET AL.
in the induction of molt, but may also be required for its thermogenic effect during the period of heavy feather loss. Management factors that are used to induce molt and control the length of the molting period must therefore act through effects on the reproductive and associated endocrine systems. Riley and Byerly (1943) noted that the reduction of light in the photoperiod caused a marked loss of feathers and they related completion of primary wing molt to return of production. Hansen (1966, 1969) reported that reduction of light in the photoperiod to 8 h/day 2 wk prior to, during, and after feed withdrawal resulted in a more complete molt and that continuing the reduction of light in the photoperiod kept hens out of production. Brake and Thaxton (1982) found that reducing the number of hours of light during the molting period hastened the initiation of the molting process as well as reducing mortality. Obviously, photoperiod and nutritional deprivation as molt induction methods have similar modes of action through the hypothalamichypophyseal axis, with modulation of the ovary being the pivotal endocrine event. The physiological importance of the extent of feather replacement has been documented by several authors. Krueger et al. (1977), working with turkeys, noted a positive and highly significant correlation between the number of flight feathers missing or replaced by the end of 8 wk of light restriction and the number of days to first egg. Harms (1983) determined that the number of days for a hen to return to production after the resting period was directly related (r = .98) to the number of primaries molted.This suggests that the extent of molt is controlled by the duration of ovarian regression. Feathers have been shown to be protein based, with sulfur-containing amino acids a major component. Availability of crude protein and specific amino acids during molt would be expected to affect the progress of feather replacement (Brake, 1982). Richards (1977) reported that heat stress is confounded with feather condition since the metabolic rate of poorly feathered birds averages some 60% above that of controls. Pardue and Thaxton (1982) noted that ascorbic acid (AA) improved livability in broilers during heat stress. Thus it was thought that some benefit from dietary AA might occur with birds just completing a molt if temperatures increased dramatically during this experiment. The objective of this study was to compare the effects of lighting
program, molt diet, total sulfur amino acids (TSAA) in the postmolt layer diet, and A A in the postmolt layer diet loss of primary and secondary remiges (flight feathers) and rate of regrowth of primary feathers. MATERIALS AND METHODS
Three hundred twenty DeKalb XL, Single Comb White Leghorn (SCWL) hens, 60 wk of age, in 80% production were placed two per cage, five cages per replicate lot, in an insulated, fan-ventilated, light-tight building. The building was divided in half, with a light-proof partition that allowed air movement between the two sections. Both sections shared a common air inlet and the fan ventilation was managed such that the environment of the two sections was the same. Two weeks were allotted for acclimation and sorting for uniformity. The experiment started May 29. The production data, lighting, and diet programs were as described by Andrews et al. (1987). In brief, the North Carolina State University (NCSU) lighting program was initiated with continuous light for 7 days (beginning on Day 1) prior to feed withdrawal, followed by 21 days of a 12-h light: 12-h dark photoperiod, then increased to a 14-h light: 10 h dark photoperiod from Day 29 to Day 56. The Washington State University (WSU) lighting program reduced the light portion on the photoperiod to 8 h for 28 days, beginning 7 days prior to feed withdrawal (Day 1). The light portion of the photoperiod, from Day 29 to Day 42, was increased to 10 h, then advanced to 13 h from Day 43 to Day 56. On Day 57, the light period of both treatments was increased to 15 h and to 16 h on Day 85 for the remainder of the experiment. Following a 14-day fast, either cracked corn (CC) or molt ration (MR) diets were fed from Day 22 to Day 35, at which time 14% protein corn-soy laying mash diets containing 3.5% calcium and .06% total phosphorus with either .60% or .65% TSAA, with or without 50 ppm of supplemental AA, were fed for the remainder of the experiment. Recording of feather molt was confined to the wing flight feathers; body molt was not measured. Primary and secondary wing feathers were counted on the 56th, 84th, and 112th days. To facilitate identification, primary feathers on the right wing were stained a light yellow with picric acid diluted in water (Fisher Scientific, Raleigh, NC). Individual primary feathers were
LIGHT, NUTRITION, MOLT, AND FEATHER
then measured by placing a ruler at the base of each flight feather and recording the length of the shaft in millimeters. Order of molt was taken from primary feather Number 1 beside the axial feather and progressing outward to the wing tip (Card and Nesheim, 1966). Secondary feather count began at the axial feather and proceeded back towards the body. Lucas and Stettenheim (1972) list 17 secondary feathers, five of which are short, blending with the wing coverts. Card and Nesheim (1966) list 14 secondaries present in the domestic hen. In this experiment we considered 16 secondary wing feathers and found only one hen which had molted as many as 15. Feather counts were made by checking the first 9 flight and 16 secondary feathers on the right wing of the same four hens in each lot. The presence or absence of the axial feather was recorded. The following criteria were used (Andrews and Zimmermann, 1983) in assessing primary wing molt: 1) Empty follicles were recorded as 00.0 on the score sheet and were counted as they occupied a space and represented a time in a sequence. 2) The few feathers that were in the growth process when the experiment began were considered as a part of the molt. They were measured in millimeters (mm) and counted. 3) Faded, worn feathers, or broken stubs were considered as old feathers and were not counted. Feather counts and measurements were analyzed for percent primary and secondary feather loss and primary feather growth. Results were subjected to analysis of variance using a 2 x 2 x 2 x 2 factorial arrangement of treat-
1637
ments (160 birds/main effect mean; 20 birds/ subcell) using the SAS Institute Inc. (1982) general linear models procedures. The main effects were lighting program, molt diet, laying diet TSAA, and laying diet AA. Each sample time was analyzed individually. Percentage data were subjected to arcsin transformation prior to analysis. Statements of statistical significance are based on P<.05. RESULTS AND DISCUSSION
It is important to note that lighting control in this experiment began on Day 1, whereas feed restriction was started Day 8. This allowed normal production to continue while the birds were being photosensitized for a more complete and rapid molt following fasting. Lighting program caused the greatest effect among the factors studied (Table 1). The WSU program hens given 42 days of reduced light in the photoperiod (8 h x 28 days; 10 h x 14 days) had by the 56th day significantly more primary and secondary feather loss than the NCSU program hens (24 h x 7 days; 12 h x 21 days; 14 h x 14 days). This amounted to WSU treatment loss of 29% more primaries and 35% more secondaries than in the NCSU treatment; however, the primaries grown by turkeys in the WSU treatment were significantly shorter (11%). Although primary and secondary feather loss essentially ceased at 56 days, growth of primary feathers continued rapidly through 84 days. Primary growth increased, with WSU treatment birds experiencing a 67% increase vs.
TABLE 1. Effects of two different lighting programs at Washington State University (WSU) and North Carolina State University (NCSU) on number of primary and secondary feathers lost, generation of new primary feather growth and average length of primary feathers grown1 Primaries lost Day
WSU
56 84 112
6.2* 6.4* 6.4*
NCSU
Total primary growth WSU
NCSU
60.9* 102.1* 110.3*
52.3D
(no) 4.8 C
5.1 1
Primary length
Secondaries lost
WSU
NCSU
WSU
9.9° 15.9* 17.1*
11.0* 15.5 b 16.7 b
12.3* 13.1* 13.1*
NCSU
9.1b 10.1b 10.1b
(cm) 78.3 b 85.8 b
ab • ' Values with superscripts that differ within the same horizontal row and category are significantly different (P<.05). 'The WSU lighting program decreased light in the photoperiod premolt to 8 h for 1 wk, continued at 8 h during molt for 3 wk, then 10 h for 2 wk, 13 h for 2 wk, 15 h for 4 wk, and 16 h for the remainder of the experiment. The NCSU program increased lighting photoperiod premolt to 24 h for 1 wk, then 12 h for 3 wk, 14 h for 4 wk, 15 h for 4 wk, and 16 h for the remainder of the experiment.
1638
ANDREWS ET AL. TABLE 2. Effects of molt diets of cracked corn (CC) or molt ration (MR) upon number of primary and secondary feathers lost and regrowth of primaries1 Primaries lost
Day
CC
56 84 112
5.6" 5.9" 5.9"
MR (.no; 5.4" 5.6" 5.6"
Total primary growth CC
MR
53.3 b 91.4" 99.5"
60.0" 88.6" 96.1"
Primary length CC
Seco ndaries lost
MR
CC
11.3" 15.8" 16.9"
11.1" 12.0" 12.0"
(cm)
9.5 b 15.6" 16.9"
MR (no) 10.3" 11.1" 11.2"
ab ' Values with superscripts that differ within the same horizontal row and category are significantly different (P<.05). 1
CC and MR fed for 14 days following completion of weight loss period.
the NCSU treatment birds increase of 41%. Growth rates from the 84th through 112th day were identical at 1.2 cm/primary in both treatments. This resulted in a significant difference in both the number of primaries lost and the length of feathers grown for the two treatments, with the reduced WSU photoperiod encouraging primary and secondary feather replacement. Longer photoperiods, as supplied by the NCSU program, significantly reduced primary feather loss by 20%, total primary feather growth by 22%, and secondary feather loss by 23%. This reduction in feather replacement needs coincides with the time during which birds in this treatment gained 7.2 eggs over those on the WSU program with reduced light in the photoperiod (Andrews et al., 1987). This was due to a shortened period of ovarian regression, which allowed fewer feathers to be molted. This, in turn, reduced dietary requirements for feather replacement and provided nutrients for earlier onset of lay. These results give support to the recommendations of
Brake and Carey (1983) that longer photoperiods contribute to increased egg production. A comparison of molt diet effects is given in Table 2. Molt diets fed from Day 22 to Day 35 did not affect the number of primary or secondary feathers molted at 56 days. Growth of primaries as measured by total growth, 60 vs. 53.3 cm, and average length increase, 11.3 vs. 9.5 cm, were both significantly higher for the MR than for the CC treatment at 56 days. By 84 days primary feather length of birds on the CC diet had essentially equalled that of birds on the MR diet. At 112 days primary feather length was identical at 16.9 cm for birds on the two diets. Further growth would be expected, as Lucas and Stettenheim (1972) report that mature SCWL hen primary wing feathers vary between 20.4 and 15.2 cm in length from the 1st through 8th feather. This would average to 18.7 cm and is in keeping with other results at this station. Although primary feather loss essentially stopped at 56 days, one more secondary
TABLE 3. Effects of higher level of total sulfur amino acids in laying rations on mean growth and percent of primary and secondary feathers molted1 % Primaries: molted Wk
600 mg
56 84 112
53.2" 56.1" 55.5"
Total primary growth
650 mg
600 mg
650 mg
57.2" 59.4" 60.0"
54.1" 86.1" 93.2 b
59.1" 93.9" 102.4"
do)
Primary growth (x) 600 mg (uu) 10.4" 15.6" 16.9"
Secondaries: molted
650 mg
600 mg
650 mg
10.5" 15.8" 17.0"
65.2" 70.3" 70.3"
68.8" 74.3" 74.7"
ab ' Values with superscripts that differ within the same horizontal row and category are significantly different (P<.05). 1 Total sulfur amino acid level of 600 and 650 mg of methionine and cystine/kg diet calculated for laying rations.
LIGHT, NUTRITION, MOLT, AND FEATHER
was lost before the 84th day in both the light and molt diet treatments. The MR treatment birds resumed egg production earlier (Andrews et al., 1987) due to an early replacement of feathers. Once egg production commenced, the birds rate of feather growth slowed, thus the more rapid early growth in the MR treatment is indicative of availability of nutrients. The effect of a higher level of TSAA in the laying diet is shown in Table 3. The addition of 50 mg of methionine, raising the TSAA complement in the laying ration to 650 mg/kg, produced a significantly higher total primary feather growth at 112 days. This is in keeping with the report by Brake (1982). As the ration was not fed until the 35th day, effects might be expected to be delayed. The addition of ascorbic acid (50 ppm) to the diets did not significantly affect wing molt. Birds without dietary AA molted 58.6% of primary wing feathers compared with 56.9% for those given 50 ppm of dietary AA. Corresponding secondary feather molt figures were 73.4% vs. 71.6%. Taken together, these data indicate the complexity of the effects of lighting program and nutrition as they relate to the progression of molt. A reduced period of ovarian regression, mediated through the longer light portion of the NCSU photoperiods, produced significantly less feather loss and presumably lower nutrient requirements and allowed birds to resume lay earlier. During the period of molt, the use of a balanced MR increased early feather growth when compared with effects of feeding a CC diet, thus providing additional nutrients during the earlier onset of lay. The use of additional methionine in the laying ration hastened completion of primary feather growth. These results, and the data of Andrews et al. (1987) suggest that maximizing feather loss does not maximize egg production. Optimum production is achieved by a short period of complete reproductive regression and a rapid return to lay. These objectives may be met by a proper combination of photoperiod and nutritional management.
ACKNOWLEDGMENTS
The authors express appreciation to Jimmy Hinnant for care of the poultry and to Grace Brockman for technical assistance. The authors
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thank Hoffmann-LaRoche for the gift of ascorbic acid. REFERENCES Andrews, D. K., W. D. Berry, and J. Brake, 1987. Effect of lighting program and nutrition on reproductive performance of molted Single Comb White Leghorn hens. Poultry Sci. 66:1298-1305. Andrews, D. K., and N. G. Zimmermann, 1983. Wing molt observations on laying hens after ahemeral light treatments. Poultry Sci. 62:1373. (Abstr.) Brake, J. T., 1982. Physiological, nutritional, and management aspects of artificially induced molting in poultry. Vol. 1. Pages 306-330 in: Proc. Symp. Management of Food Producing Anim. May 5-7. W. Lafayette, IN. Brake, J. T., and J. B. Carey, 1983. Induced molting of commercial layers. N.C. Agric. Ext. Serv. Poultry Sci. and Tech. Guide No. 10. Raleigh, NC. Brake, J., and P. Thaxton, 1982. Comparative effect of photoperiod modification and/or fasting with a short period without water on physiological and performance parameters associated with molt in SCWL hens. Poultry Sci. 61:1423. (Abstr.) Card, L. E., and M. C. Nesheim, 1966. Poultry Production. 10th ed. Lea and Febiger, Philadelphia, PA. Decuypere, E., andG. Verheyen, 1986. Physiological basis of induced molting and tissue regeneration in fowl. World's Poult. Sci. J. 42:56-68. Hansen, R. S., 1966. Reducing light to facilitate the induced rest (forced molt). Poultry Sci. 45:1089. (Abstr.) Hansen, R. S., 1969. The biology: how, what, when and why of recycling. Proc. Ohio Market Egg Day Program, January 28. The Ohio State Univ., Columbus, OH. Harms, R. H., 1983. The relationship of molted primaries of commercial layers to first egg after molt. Poultry Sci. 62:1123-1124. Krueger, K. K., T. M. Fergerson, J. A. Owen, and C. E. Krueger, 1977. The influence of feather loss on subsequent egg production in force molted turkey hens. Poultry Sci. 56:35. (Abstr.) Lucas, A. L.,andP. R. Stettenheim, 1972. Avian AnatomyIntegument. Part 1. Agric. Handbook 362. US Gov. Print. Off., Washington, DC. Pardue, S. L., and J. P. Thaxton, 1982. Enhanced livability and improved immunological responsiveness in ascorbic acid supplemented cockerels during acute heat stress. Poultry Sci. 61:1522. (Abstr.) Richards, S. A., 1977. The influence of loss of plumage on temperature regulation in laying hens. J. Agric. Soc. Cambridge 89:393-398. Riley, G. M., and T. C. Byeriy, 1943. The influence of increased light on progress of molt and egg production in yearling Rhode Island Red hens. Poultry Sci. 22:301-306. SAS Institute, Inc., 1982. SAS User's Guide: Statistics, 1982 Ed. SAS Institute, Inc., Cary, NC. Sturkie, P. D., 1986. Avian physiology. 4th ed., Springer Verlag, New York, NY. Watson, G. E., 1963a. The mechanism of feather replacement during natural molt. Auk 80:486-495. Watson, G. E., 1963b. Feather replacement in birds. Science 139:50. (Abstr.)