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Light Intensity Effects on Reproductive Performance of Turkey Breeder Hens1
EDUCATION AND PRODUCTION Light Intensity Effects on Reproductive Performance of Turkey Breeder Hens 1 T. D. SIOPES Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27695-7608 (Received for publication December 26, 1990) ABSTRACT Two trials were conducted to evaluate the reproductive performance of turkey hens to different light intensity during the lay period. In Trial 1 the hens were exposed to 16 h of light (L) and 8 h dark (D) per day(16L:8D)atS4,108, or216 be and inTrial 2 a 2 x 2 factorial arrangement of treatments was used withmain treatment factors being intensity level (54 versus 324 lx) and photoperiod (16L:8D versus 14L:10D). Data were collected for time to onset of lay, rate of lay, fertility, hatchability, and egg and poult weight in both trials, and feed intake in Trial 1. In both trials the Ught intensity treatments were similarly effective in the photoinduction of reproductive performance in Large White turkey hens. This occurred with daily photoperiods of both 14L:10Dand 16L:8D in Trial 2 and there was no photoperiod by intensity interaction. There were no significant differences in feed intake or feed efficiency among the 54-, 108-, and 216-lx treatments of Trial 1. It may be concluded that reproductive performance of turkey hens in closed confinement is equivalent within an intensity range of 54 to 324 lx. {Key words: turkey, reproduction, light intensity, feed, recycling) 1991 Poultry Science 70:2049-2054 INTRODUCTION
Effective lighting management of turkey reproductive performance requires the use of artificial light sources. The practical intensity levels that can be achieved with these sources are limited relative to natural light, but they appear to be quite effective. Incandescent Ught sources in commercial and research use generally provide about 108 lx or less light intensity, whereas some of the new highintensity, discharge-type lamps may generate intensity ranges of 55 to 350 lx. The levels of intensity being used for breeder turkeys in industry and research are highly variable, and information is insufficient to permit making recommendations on the most effective light intensity levels. The influence of increased levels of light intensity on reproductive performance of turkey breeder hens is poorly defined. Published reports do not definitively support either the presence or absence of beneficial effects of increased light intensity. Asmundson et al. (1946) reported that a light intensity treatment
The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service nor criticism of similar ones not mentioned.
that ranged from about 21 to 54 lx produced the maximum response in Bronze turkeys with respect to onset of lay and egg production. However, the highest intensity treatment they used ranged from 45 to 112 lx. Campbell et al. (1960) reported no significant differences in egg production by Small White turkeys given intensities of light ranging from 6.5 to 432 lx. The absence of effects of elevated light intensity on reproductive performance of Large White turkeys in closed confinement has also been reported in studies comparing 5.4 versus 86.1 lx (Thomason et al, 1972), 16.2 versus 32.4 lx (McCartney, 1971), and 22 versus 108 lx (Siopes, 1984). The research cited above suggests that once some certain photostimulatory light intensity level is exceeded, there is little benefit from additional levels of light intensity. However, a beneficial effect of increased light intensity has been reported by Nestor and Brown (1972). Large White hens, but not Medium White hens, consistently increased their egg production as the light intensity was raised from 18 to 51 lx. Garland et al. (1961) generally observed that increased light intensity (22 versus 367 lx) improved egg production in Medium White turkey hens. There is only one scientific report of a negative effect of increased light intensity on egg production in turkeys. Jones et al.
2049
2050
SIOPES
(1982) reported that hens exposed to 160 lx had poorer egg production than hens exposed to 85 lx. Of the reports cited above, only those that utilized 14 h of light (L) and 10 h dark (D) per day (14L:10D) (Garland et al, 1961; Nestor and Brown, 1972) showed beneficial effects of increased light intensity, whereas the other reports used daily light :dark cycles of 15L:9D or 16L:8D. This is suggestive of a photoperiod by intensity interaction. The objectives of the present study were to compare the reproductive performance of Large White turkey hens exposed to different incandescent light intensities under closed confinement housing conditions and to determine whether responses to light intensity treatments can be influenced by different, but commonly utilized, photoperiods. MATERIALS AND METHODS
Husbandry Two trials were conducted to evaluate the response of Nicholas Large White turkey breeder hens to levels of light intensity within a range typically used in research and industry facilities. In both trials the same strain of hen, facilities, and management practices were used. The hens were obtained as poults from a commercial breeder and brooded and reared in a curtain-sided growout house on site. The solidwall, light controlled building used during the study was not temperature controlled but was insulated and the room was mechanically ventilated. All light treatments started immediately following an 8-wk period of light restriction (8L:16D) imposed to ensure that the hens would be photosensitive when subsequently exposed to the light treatments. Feed and fresh water were provided for ad libitum intake throughout the study. Feed was a pelleted breeder ration calculated to contain 16% protein, 2,970 kcal ME/kg feed, and 3.05% calcium. All treatments were applied to hens maintained in single or double rows of individual cages (46 cm wide x 61 cm high x 56 cm deep). This allowed for consistent and precise exposure to the light treatments throughout the study. Only artificial light from incandescent lamps
Model 161, United Detector Technology, Hawthorne, CA 90250.
was used, and within the test room the light treatments were separated from one another by black plastic partitions. Light intensity was measured with a photometer-radiometer.2 The reported intensity levels are mean levels taken in the center of the cage at head level in three cages per row (both ends and the middle cage). The range of values within a treatment were within 10% of the mean values. Variables Data were collected, by hen, for initiation of sexual activity, rate of lay, percentage of fertility, percentage of hatch, egg weights, and poult weights in both trials. In Trial 1, feed intake and feed efficiency were also obtained. The initiation of sexual activity was estimated as the time required to lay the first egg following exposure to the light treatments. Egg production was recorded daily and rate of lay was expressed as the cumulative number of eggs produced per hen after 5,10, 15, or 20 wk of egg laying. All hens were artificially inseminated at the same time of day (1400 to 1600 h) with pooled semen within 30 min of semen collection. The semen was diluted 1:1 with a commercial extender and .025 mL of extended semen was inseminated per hen. In Trial 1, two consecutive weekly inseminations were given 4 wk after the start of the treatments and biweekly thereafter. In Trial 2, two consecutive weekly inseminations were given immediately prior to each of two 7-day egg collection periods (11 to 12 and 15 to 16 wk of photostimulation). Percentage fertility was determined by candling eggs after 7 days of incubation and breaking out eggs to differentiate early-dead from infertiles. Percentage hatch was the percentage of hatch from all fertile eggs. Eggs were collected six times daily, physically cleaned, and washed in an automatic turkey egg washer, and immediately stored in an egg cooler (12.8 C and 75% relative humidity). The eggs were placed in incubators within 7 days following collection. Experimental Design Trial 1. Hens were photostimulated with 16 h of light/day (16L:8D) in closed confinement at 32 wk of age (September) at one of the following light intensity levels: 54, 108, or 216 lx. Thirty individually caged hens were assigned to each treatment group and reproductive performance was evaluated over 24 wk of photostimulation.
LIGHT INTENSITY EFFECTS
2051
TABLE 1. The effect of light intensity on photoinduced reproductive performance of turkey breeder henr Light intensity treatment
Days to first egg 2
per hen
Percentage fertility4
Percentage batch of fertile eggs
(lx) 54 108 216
23.2 ± .7 23.8 ± .9 22.5 ± .5
78.1 ± 3.6 78.8 ± 3.6 79.7 ± 2.9
77.8 ± 3.5 69.4 ± 4.8 74.8 ± 2.0
70.1 ± 2.6 79.6 ± 3.5 76.0 ± 3.4
Light intensity treatments had no significant effect (P>.05) on any variable. Days from start of photostimulation. Cumulative to 20 wk of lay. 'Overall mean of four 7-day collection periods (7 to 8, 11 to 12, 15 to 16, and 19 to 20 wk of photostimulation). Numbers of eggs ranged from 438 to 492.
Egg weight, poult weight, fertility, and hatchability data were obtained during four 7-day periods occurring at 7 to 8, 11 to 12, 15 to 16, and 19 to 20 wk after initial photostimulation. Feed intake data were obtained from groups of individual hens over two 14-day periods (14 to 16 and 20 to 22 wk of photostimulation). There were six groups of five hens each for feed intake evaluation at each light intensity treatment, otherwise individual hen data was obtained. Feed efficiency was calculated as the amount of feed consumed per unit of BW per egg produced. Trial 2. Yearling hens were recycled by short-day light restriction (8L: 16D) for 8 wk and then photostimulated into lay at 68 wk of age (March). The light treatments were presented in a 2 x 2 factorial arrangement that evaluated two light intensities (54 versus 324 lx) at two durations (16L:8D versus 14L:10D). There were 20 hens in each of the four treatment groups and performance was evaluated over 19 wk of photostimulation. In this trial two 7-day egg collection periods were used to obtain egg weight, percentage fertility, percentage hatchability, and poult weight. These occurred at 11 to 12 and 15 to 16 wk of photostimulation. One additional 7-day period was used to obtain egg weights at 4 to 5 wk of photostimulation.
estimate significant differences among treatment means. The arc sine transformation was used for all percentage data. Statements of statistical significance are based on P<.05 unless otherwise specified. RESULTS
There were no significant differences among light intensity treatments for eggs per hen at 5, 10, 15, or 20 wk of lay or for fertility and hatchability during any of the four time periods of Trial 1. Therefore, only the cumulative eggs per hen for 20 wk of lay are given and, in addition, the fertility and hatchability data are overall means of the four combined measurement periods (8, 12, 16, and 20 wk of photostimulation) of the study (Table 1). In addition, there were no significant effects of the light intensity treatments on feed intake or feed efficiency during either of the two 14-day measurement periods. Therefore, the data of these time periods were combined and the comparison of overall means are presented in Table 2. Feed intake ranged from 25.8 to 26.4 g feed/kg BW per day across all treatments, whereas feed efficiency (grams of feed:kilogram of BW per egg) ranged from 45.5 to 46.5. In Trial 2, no significant interaction occurred between light intensity and photoperiod Data Analysis for any of the measures of reproductive Analysis of variance according to Steele and performance. Thus, the results are presented in Torrie (1980) was used to evaluate the treatment terms of main treatment factors, intensity and effects using the General Linear Model proce- photoperiod (Table 3). No significant effects of dure of the SAS Institute (1982). In Trial 1 a one- the treatments (intensity or photoperiod) ocway ANOVA was utilized, whereas in Trial 2 a curred, therefore only the cumulative eggs per two-way ANOVA was used. Where appropriate, hen for 15 wk of lay are given and fertility and Duncan's multiple range test was used to hatchability comparisons are for overall treat-
2052
SIOPES TABLE 2. The effect of light intensity on feed intake of turkey breeder hens during photoinduced egg production
Light intensity treatment
Feed intake
(Ix) 54 108 216
(g/kg BW per day) (g:kg BW per egg) 25.8 ± .4 45.3 ± 1.7 26.4 ± .7 46.2 ± 3.8 26.2 ± .5 46.5 ± 2.8
Feed efficiency^
Light intensity treatments had no significant effect (P>.05) on feed intake or feed efficiency. Ti ± SEM over two 14-day measurement periods (14 to 16 and 20 to 22 wk of photostimulation).
ment means from the two 7-day measurement periods. During the course of Trial 1, 2 of 80 hens died. In Trial 2, 2 of 160 hens died and 14 were removed because of obvious physical abnormalities. The remaining hens were healthy and normal in appearance. In both trials, the time to onset of lay and hatchabihty were within expected ranges. The rate of lay was typical in Trial 1, but somewhat less than expected in Trial 2. The latter was a consequence of a reduction in rate of lay during the last 5 wk of lay (June to 1st wk of July) that coincided with the first sharp increase in summer heat. That the Trial 2 hens were recycled hens also likely contributed to the lowered rate of lay. Fertility across all treatment groups of both trials was somewhat depressed from expected levels for unknown reasons.
The effects of the light treatments of both trials on egg weight and poult weight are given in Table 4. Egg weights ranged from 90.5 to 92.8 g and 95.8 to 97.8 g in Trials 1 and 2, respectively, and were not affected differentially by the light treatments in either trial. The 108-lx intensity treatment of Trial 1 had significantly smaller poults (59.1 g) than the 54- or 216-lx groups (61.3 and 60.9 g), which were similar. Poult weights of Trial 2 were similar for both the intensity and photoperiod treatments. DISCUSSION
The results of the present study indicate that light intensity levels between 54 and 324 lx were similarly effective in the photoinduction of reproductive performance of Large White turkey hens. This occurred at photostimulatory daylengths of both 14L:10D and 16L.8D and there was no indication of an interaction between photoperiod and intensity level. Clearly, there appears to be a wide range of intensity levels to which reproductive functions of turkeys respond similarly. A stable response to wide-ranging levels of light intensity is not an unexpected result considering that birds in the natural environment are commonly and frequently exposed to widely fluctuating intensity levels and could ill afford to be responsive to all of these variations. Thus, it appears that once a certain level of light intensity is achieved, sufficient light reaches the photoperiodic apparatus to maximally stimulate reproductive function. The
TABLE 3. Light intensity and duration effects (x ± SEM) on photoinduced reproductive performance of turkey breeder henr
Main treatment factor Intensity, lx 54 324 Photoperiod5 16L:8D 14L:10D
Days to first egg^
Eggs per her?
Percentage fertility4
Percentage hatch of fertile eggs
25.5 + .9 26.2 ± .6
40.9 ± 2.3 40.1 ± 1.5
78.8 ± 7.1 79.0 ± 5.0
71.1 ± 6.8 68.0 ± 3.0
26.1 ± .8 25.6 ± .7
41.6 ± 2.1 39.4 ± 1.8
80.4 ± 5.8 77.4 ± 6.3
73.2 ± 5.5 66.0 ± 4.7
J
Main treatment factors had no significant effect on any variable (P>.05). Days from start of photostimulation. Cumulative to 15 wk of lay. Overall mean of two 7-day collection periods (11 to 12, 15 to 16 wk of photostimulation). Numbers of eggs ranged from 214 to 240. 2
'Hours of light (L):hours of darkness (D).
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LIGHT INTENSITY EFFECTS TABLE 4. The effect of light treatments of Trials 1 and 2 on poult weight and egg weight Poults Treatments
n
weight1
n
(g)
weight1 — (g)
Trial 1 Intensity, Ix 54 108 216 Intensity, lx 54 324 Photoperiod, h 2 16L:8D 14L:10D
452 92.8 ± 1.0s 438 90.5 ± 1.1* 492 92.2 ± .8 a Tria'
252 61.3 ± .4* 238 59.1 ± .4 b 278 60.9 ± .4* ^
231 97.6 ± 1.3* 223 95.9 ± 1.2*
75 63.8 ± .8* 66 63.5 ± .6*
240 95.8 ± 1.0* 214 97.8 ± 1.4*
87 63.1 + .6* 54 64.6 ± .9*
"•"Means within columns and treatments with no common superscripts letters are significantly different (P<05). 1 Means (± SEM) over four 7-day sampling periods ending at 8, 12, 16, and 20 wk of photostimulation (Trial 1) and three periods at 5, 12, or 16 wk of photostimulation (Trial 2). 2 Hours of light (L):hours of darkness (D).
minimum intensity requirement for optimum egg production cannot be determined by the present study, but must be < 54 lx. Asmundson et al. (1946) estimated this level to be in the 21 to 54 lx range. Even though the light intensity level of 324 lx used in the present study would be considered high for typical commercial or research settings it is quite low relative to natural light, which can be about 105 lx. Thus, it seems natural to question potential beneficial effects of higher artificial light intensity but practicality becomes an important consideration. Few studies have been reported for controlled light intensities greater than 324 lx on avian female reproduction. Campbell et al. (1960) reported that reproductive performance in turkeys was similar up to 432 lx. Bobwhite quail had similar photoinduced onsets of lay between 1.1 and 1,080 lx but 3,240 lx accelerated onset of lay (Kirkpatrick, 1955). However, few birds were used in this study and at 3,240 lx only three of six females ovulated. Clearly, these studies do not imply that high light intensity levels are beneficial for confinement-housed birds. Within light intensity ranges typically observed in commer-
cial and research settings (5 to about 300 lx), the present results agree with the majority of existing scientific reports in indicating an absence of light intensity effects on reproductive performance of turkeys (Asmundson et al., 1946; McCartney, 1971; Thomason et al., 1972; Siopes, 1984). A similar lack of intensity effects has also been reported for chickens (Dobie et al., 1946; Ostrander et al., 1960). There are many factors that might influence the reproductive responses of turkeys to light intensity, including type of confinement, season, environmental factors, and strain. Strain effects have been documented by Nestor and Brown (1972) and the effects of an interesting environmental factor, photophase contrast, has been described by Meyer et al. (1988). Under the conditions of the present study, closed confinement-housed hens with treatments starting in March or September, there does not appear to be justification for exposure of turkey hens to light intensity levels beyond 54 lx during the lay period. However, this does not exclude the possibility that light intensity may in fact influence reproductive performance under other conditions, as noted above. Most notable would be conditions related to season, light-dark contrasts, and type of light source. In addition to reproductive performance, energy utilization in the form of electricity and feed is a major concern in turkey breeder management. Certainly, any power used in lighting above that which allows a maximum response is wasted energy and an economic loss. In addition, increased feed utilization could potentially occur as a consequence of increased maintenance energy requirements associated with increased locomotor activity and metabolic rate induced at higher light intensity levels (Aschoff, 1965; Pohl, 1969; Gwinner, 1975). However, no difference in feed intake or feed efficiency occurred among the 54, 108, and 216 lx light intensity treatments of the present study. It may be concluded from the present study that there is no apparent benefit on reproductive performance of exposing Large White turkey hens in closed confinement to artificial light intensities in excess of 54 lx. REFERENCES Aschoff, J., 1965. Orcadian Clocks. North Holland Publishers, Amsterdam, The Netherlands. Asmundson, V. S., F. W. Lorenz, and B. D. Moses, 1946.
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Influence of light intensity on ovulation in turkeys. Poultry Sci. 25:346-354. Campbell, L. E., L. M. Lucas, J. G. Hartsock, C. P. Davis, and S. J. Marsden, 1960. Experiments with controlled light intensity for turkeys. Trans. Am. Soc. Agric. Eng. 3:45-48. Dobie, J. B„ J. S. Carver, and J. Roberts, 1946. Poultry Lighting for Egg Production. Bulletin 471, Washington State Agricultural Experiment Station, Pullman, WA. Garland, F. W., Jr., R. C. Easton, D. E. Greene, H. L. Wilke, and R. M. Belike, 1961. Duration and intensity of light for out of season egg production in turkeys. Poultry Sci. 40:1406-1407. Gwinner, E., 1975. Orcadian and circannual rhythms in birds. Pages 221-274 in: Avian Biology. Vol. 5. D. S. Farner, J. R. King, and R. C. Parker, ed. Academic Press, New York, NY. Jones, J. E., B. L. Hughes, R. J. Thurston, R. A. Hess, and D. P. Frohman, 1982. The effects of red and white light during the prebreeder and breeder periods on egg production and feed consumption in Large White turkeys. Poultry Sci. 61:1930-1932. Kirkpatnck, C. M., 1955. Factors in photoperiodism of Bobwhite quail. Physiol. Zool. 28:255-264. McCartney, M. G., 1971. Reproduction of turkeys as by age at lighting and light intensity. Poultry Sci. 50:
661-662. Meyer, W. E., J. R. Millam, and F. A. Bradley, 1988. Photostimulation of Japanese quail by dim light depends upon photophase contrast, not light intensity. Biol. Reprod. 38:536-543. Nestor, K. E., and K. I. Brown, 1972. Light intensity and reproduction of turkey hens. Poultry Sci. 51: 117-121. Ostrander, C. E., R. K. Ringer, and H. C. Zindel, 1960. The effect of various light intensities on egg production of Single Comb White Leghorn pullets. Q. Bull. Mich. Agric. Exp. Stn. 43:292-297. Pohl, H., 1969. Some factors influencing the metabolic response to cold in birds. Fed. Proc. 28:1059-1064. SAS Institute, 1982. SAS® User's Guide: Statistics. 1982 ed. SAS Institute, Inc., Cary, NC. Siopes, T. D., 1984. The effect of high and low intensity cool-white fluorescent lighting on the reproductive performance of turkey breeder hens. Poultry Sci. 63: 920-926. Steele, R.GX)., and J. H. Torrie, 1980. Principles and Procedures of Statistics. McGraw-Hill Book Co., New York, NY. Thomason, D. M., A. T. Leighton, Jr., and J. P. Mason, Jr., 1972. A study of certain environmental factors on reproductive performance of Large White turkeys. Poultry Sci. 51:1438-1449.
Effective lighting management of turkey reproductive performance requires the use of artificial light sources. The practical intensity levels that can be achieved with these sources are limited relative to natural light, but they appear to be quite effective. Incandescent Ught sources in commercial and research use generally provide about 108 lx or less light intensity, whereas some of the new highintensity, discharge-type lamps may generate intensity ranges of 55 to 350 lx. The levels of intensity being used for breeder turkeys in industry and research are highly variable, and information is insufficient to permit making recommendations on the most effective light intensity levels. The influence of increased levels of light intensity on reproductive performance of turkey breeder hens is poorly defined. Published reports do not definitively support either the presence or absence of beneficial effects of increased light intensity. Asmundson et al. (1946) reported that a light intensity treatment
The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service nor criticism of similar ones not mentioned.
that ranged from about 21 to 54 lx produced the maximum response in Bronze turkeys with respect to onset of lay and egg production. However, the highest intensity treatment they used ranged from 45 to 112 lx. Campbell et al. (1960) reported no significant differences in egg production by Small White turkeys given intensities of light ranging from 6.5 to 432 lx. The absence of effects of elevated light intensity on reproductive performance of Large White turkeys in closed confinement has also been reported in studies comparing 5.4 versus 86.1 lx (Thomason et al, 1972), 16.2 versus 32.4 lx (McCartney, 1971), and 22 versus 108 lx (Siopes, 1984). The research cited above suggests that once some certain photostimulatory light intensity level is exceeded, there is little benefit from additional levels of light intensity. However, a beneficial effect of increased light intensity has been reported by Nestor and Brown (1972). Large White hens, but not Medium White hens, consistently increased their egg production as the light intensity was raised from 18 to 51 lx. Garland et al. (1961) generally observed that increased light intensity (22 versus 367 lx) improved egg production in Medium White turkey hens. There is only one scientific report of a negative effect of increased light intensity on egg production in turkeys. Jones et al.
2049
2050
SIOPES
(1982) reported that hens exposed to 160 lx had poorer egg production than hens exposed to 85 lx. Of the reports cited above, only those that utilized 14 h of light (L) and 10 h dark (D) per day (14L:10D) (Garland et al, 1961; Nestor and Brown, 1972) showed beneficial effects of increased light intensity, whereas the other reports used daily light :dark cycles of 15L:9D or 16L:8D. This is suggestive of a photoperiod by intensity interaction. The objectives of the present study were to compare the reproductive performance of Large White turkey hens exposed to different incandescent light intensities under closed confinement housing conditions and to determine whether responses to light intensity treatments can be influenced by different, but commonly utilized, photoperiods. MATERIALS AND METHODS
Husbandry Two trials were conducted to evaluate the response of Nicholas Large White turkey breeder hens to levels of light intensity within a range typically used in research and industry facilities. In both trials the same strain of hen, facilities, and management practices were used. The hens were obtained as poults from a commercial breeder and brooded and reared in a curtain-sided growout house on site. The solidwall, light controlled building used during the study was not temperature controlled but was insulated and the room was mechanically ventilated. All light treatments started immediately following an 8-wk period of light restriction (8L:16D) imposed to ensure that the hens would be photosensitive when subsequently exposed to the light treatments. Feed and fresh water were provided for ad libitum intake throughout the study. Feed was a pelleted breeder ration calculated to contain 16% protein, 2,970 kcal ME/kg feed, and 3.05% calcium. All treatments were applied to hens maintained in single or double rows of individual cages (46 cm wide x 61 cm high x 56 cm deep). This allowed for consistent and precise exposure to the light treatments throughout the study. Only artificial light from incandescent lamps
Model 161, United Detector Technology, Hawthorne, CA 90250.
was used, and within the test room the light treatments were separated from one another by black plastic partitions. Light intensity was measured with a photometer-radiometer.2 The reported intensity levels are mean levels taken in the center of the cage at head level in three cages per row (both ends and the middle cage). The range of values within a treatment were within 10% of the mean values. Variables Data were collected, by hen, for initiation of sexual activity, rate of lay, percentage of fertility, percentage of hatch, egg weights, and poult weights in both trials. In Trial 1, feed intake and feed efficiency were also obtained. The initiation of sexual activity was estimated as the time required to lay the first egg following exposure to the light treatments. Egg production was recorded daily and rate of lay was expressed as the cumulative number of eggs produced per hen after 5,10, 15, or 20 wk of egg laying. All hens were artificially inseminated at the same time of day (1400 to 1600 h) with pooled semen within 30 min of semen collection. The semen was diluted 1:1 with a commercial extender and .025 mL of extended semen was inseminated per hen. In Trial 1, two consecutive weekly inseminations were given 4 wk after the start of the treatments and biweekly thereafter. In Trial 2, two consecutive weekly inseminations were given immediately prior to each of two 7-day egg collection periods (11 to 12 and 15 to 16 wk of photostimulation). Percentage fertility was determined by candling eggs after 7 days of incubation and breaking out eggs to differentiate early-dead from infertiles. Percentage hatch was the percentage of hatch from all fertile eggs. Eggs were collected six times daily, physically cleaned, and washed in an automatic turkey egg washer, and immediately stored in an egg cooler (12.8 C and 75% relative humidity). The eggs were placed in incubators within 7 days following collection. Experimental Design Trial 1. Hens were photostimulated with 16 h of light/day (16L:8D) in closed confinement at 32 wk of age (September) at one of the following light intensity levels: 54, 108, or 216 lx. Thirty individually caged hens were assigned to each treatment group and reproductive performance was evaluated over 24 wk of photostimulation.
LIGHT INTENSITY EFFECTS
2051
TABLE 1. The effect of light intensity on photoinduced reproductive performance of turkey breeder henr Light intensity treatment
Days to first egg 2
per hen
Percentage fertility4
Percentage batch of fertile eggs
(lx) 54 108 216
23.2 ± .7 23.8 ± .9 22.5 ± .5
78.1 ± 3.6 78.8 ± 3.6 79.7 ± 2.9
77.8 ± 3.5 69.4 ± 4.8 74.8 ± 2.0
70.1 ± 2.6 79.6 ± 3.5 76.0 ± 3.4
Light intensity treatments had no significant effect (P>.05) on any variable. Days from start of photostimulation. Cumulative to 20 wk of lay. 'Overall mean of four 7-day collection periods (7 to 8, 11 to 12, 15 to 16, and 19 to 20 wk of photostimulation). Numbers of eggs ranged from 438 to 492.
Egg weight, poult weight, fertility, and hatchability data were obtained during four 7-day periods occurring at 7 to 8, 11 to 12, 15 to 16, and 19 to 20 wk after initial photostimulation. Feed intake data were obtained from groups of individual hens over two 14-day periods (14 to 16 and 20 to 22 wk of photostimulation). There were six groups of five hens each for feed intake evaluation at each light intensity treatment, otherwise individual hen data was obtained. Feed efficiency was calculated as the amount of feed consumed per unit of BW per egg produced. Trial 2. Yearling hens were recycled by short-day light restriction (8L: 16D) for 8 wk and then photostimulated into lay at 68 wk of age (March). The light treatments were presented in a 2 x 2 factorial arrangement that evaluated two light intensities (54 versus 324 lx) at two durations (16L:8D versus 14L:10D). There were 20 hens in each of the four treatment groups and performance was evaluated over 19 wk of photostimulation. In this trial two 7-day egg collection periods were used to obtain egg weight, percentage fertility, percentage hatchability, and poult weight. These occurred at 11 to 12 and 15 to 16 wk of photostimulation. One additional 7-day period was used to obtain egg weights at 4 to 5 wk of photostimulation.
estimate significant differences among treatment means. The arc sine transformation was used for all percentage data. Statements of statistical significance are based on P<.05 unless otherwise specified. RESULTS
There were no significant differences among light intensity treatments for eggs per hen at 5, 10, 15, or 20 wk of lay or for fertility and hatchability during any of the four time periods of Trial 1. Therefore, only the cumulative eggs per hen for 20 wk of lay are given and, in addition, the fertility and hatchability data are overall means of the four combined measurement periods (8, 12, 16, and 20 wk of photostimulation) of the study (Table 1). In addition, there were no significant effects of the light intensity treatments on feed intake or feed efficiency during either of the two 14-day measurement periods. Therefore, the data of these time periods were combined and the comparison of overall means are presented in Table 2. Feed intake ranged from 25.8 to 26.4 g feed/kg BW per day across all treatments, whereas feed efficiency (grams of feed:kilogram of BW per egg) ranged from 45.5 to 46.5. In Trial 2, no significant interaction occurred between light intensity and photoperiod Data Analysis for any of the measures of reproductive Analysis of variance according to Steele and performance. Thus, the results are presented in Torrie (1980) was used to evaluate the treatment terms of main treatment factors, intensity and effects using the General Linear Model proce- photoperiod (Table 3). No significant effects of dure of the SAS Institute (1982). In Trial 1 a one- the treatments (intensity or photoperiod) ocway ANOVA was utilized, whereas in Trial 2 a curred, therefore only the cumulative eggs per two-way ANOVA was used. Where appropriate, hen for 15 wk of lay are given and fertility and Duncan's multiple range test was used to hatchability comparisons are for overall treat-
2052
SIOPES TABLE 2. The effect of light intensity on feed intake of turkey breeder hens during photoinduced egg production
Light intensity treatment
Feed intake
(Ix) 54 108 216
(g/kg BW per day) (g:kg BW per egg) 25.8 ± .4 45.3 ± 1.7 26.4 ± .7 46.2 ± 3.8 26.2 ± .5 46.5 ± 2.8
Feed efficiency^
Light intensity treatments had no significant effect (P>.05) on feed intake or feed efficiency. Ti ± SEM over two 14-day measurement periods (14 to 16 and 20 to 22 wk of photostimulation).
ment means from the two 7-day measurement periods. During the course of Trial 1, 2 of 80 hens died. In Trial 2, 2 of 160 hens died and 14 were removed because of obvious physical abnormalities. The remaining hens were healthy and normal in appearance. In both trials, the time to onset of lay and hatchabihty were within expected ranges. The rate of lay was typical in Trial 1, but somewhat less than expected in Trial 2. The latter was a consequence of a reduction in rate of lay during the last 5 wk of lay (June to 1st wk of July) that coincided with the first sharp increase in summer heat. That the Trial 2 hens were recycled hens also likely contributed to the lowered rate of lay. Fertility across all treatment groups of both trials was somewhat depressed from expected levels for unknown reasons.
The effects of the light treatments of both trials on egg weight and poult weight are given in Table 4. Egg weights ranged from 90.5 to 92.8 g and 95.8 to 97.8 g in Trials 1 and 2, respectively, and were not affected differentially by the light treatments in either trial. The 108-lx intensity treatment of Trial 1 had significantly smaller poults (59.1 g) than the 54- or 216-lx groups (61.3 and 60.9 g), which were similar. Poult weights of Trial 2 were similar for both the intensity and photoperiod treatments. DISCUSSION
The results of the present study indicate that light intensity levels between 54 and 324 lx were similarly effective in the photoinduction of reproductive performance of Large White turkey hens. This occurred at photostimulatory daylengths of both 14L:10D and 16L.8D and there was no indication of an interaction between photoperiod and intensity level. Clearly, there appears to be a wide range of intensity levels to which reproductive functions of turkeys respond similarly. A stable response to wide-ranging levels of light intensity is not an unexpected result considering that birds in the natural environment are commonly and frequently exposed to widely fluctuating intensity levels and could ill afford to be responsive to all of these variations. Thus, it appears that once a certain level of light intensity is achieved, sufficient light reaches the photoperiodic apparatus to maximally stimulate reproductive function. The
TABLE 3. Light intensity and duration effects (x ± SEM) on photoinduced reproductive performance of turkey breeder henr
Main treatment factor Intensity, lx 54 324 Photoperiod5 16L:8D 14L:10D
Days to first egg^
Eggs per her?
Percentage fertility4
Percentage hatch of fertile eggs
25.5 + .9 26.2 ± .6
40.9 ± 2.3 40.1 ± 1.5
78.8 ± 7.1 79.0 ± 5.0
71.1 ± 6.8 68.0 ± 3.0
26.1 ± .8 25.6 ± .7
41.6 ± 2.1 39.4 ± 1.8
80.4 ± 5.8 77.4 ± 6.3
73.2 ± 5.5 66.0 ± 4.7
J
Main treatment factors had no significant effect on any variable (P>.05). Days from start of photostimulation. Cumulative to 15 wk of lay. Overall mean of two 7-day collection periods (11 to 12, 15 to 16 wk of photostimulation). Numbers of eggs ranged from 214 to 240. 2
'Hours of light (L):hours of darkness (D).
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LIGHT INTENSITY EFFECTS TABLE 4. The effect of light treatments of Trials 1 and 2 on poult weight and egg weight Poults Treatments
n
weight1
n
(g)
weight1 — (g)
Trial 1 Intensity, Ix 54 108 216 Intensity, lx 54 324 Photoperiod, h 2 16L:8D 14L:10D
452 92.8 ± 1.0s 438 90.5 ± 1.1* 492 92.2 ± .8 a Tria'
252 61.3 ± .4* 238 59.1 ± .4 b 278 60.9 ± .4* ^
231 97.6 ± 1.3* 223 95.9 ± 1.2*
75 63.8 ± .8* 66 63.5 ± .6*
240 95.8 ± 1.0* 214 97.8 ± 1.4*
87 63.1 + .6* 54 64.6 ± .9*
"•"Means within columns and treatments with no common superscripts letters are significantly different (P<05). 1 Means (± SEM) over four 7-day sampling periods ending at 8, 12, 16, and 20 wk of photostimulation (Trial 1) and three periods at 5, 12, or 16 wk of photostimulation (Trial 2). 2 Hours of light (L):hours of darkness (D).
minimum intensity requirement for optimum egg production cannot be determined by the present study, but must be < 54 lx. Asmundson et al. (1946) estimated this level to be in the 21 to 54 lx range. Even though the light intensity level of 324 lx used in the present study would be considered high for typical commercial or research settings it is quite low relative to natural light, which can be about 105 lx. Thus, it seems natural to question potential beneficial effects of higher artificial light intensity but practicality becomes an important consideration. Few studies have been reported for controlled light intensities greater than 324 lx on avian female reproduction. Campbell et al. (1960) reported that reproductive performance in turkeys was similar up to 432 lx. Bobwhite quail had similar photoinduced onsets of lay between 1.1 and 1,080 lx but 3,240 lx accelerated onset of lay (Kirkpatrick, 1955). However, few birds were used in this study and at 3,240 lx only three of six females ovulated. Clearly, these studies do not imply that high light intensity levels are beneficial for confinement-housed birds. Within light intensity ranges typically observed in commer-
cial and research settings (5 to about 300 lx), the present results agree with the majority of existing scientific reports in indicating an absence of light intensity effects on reproductive performance of turkeys (Asmundson et al., 1946; McCartney, 1971; Thomason et al., 1972; Siopes, 1984). A similar lack of intensity effects has also been reported for chickens (Dobie et al., 1946; Ostrander et al., 1960). There are many factors that might influence the reproductive responses of turkeys to light intensity, including type of confinement, season, environmental factors, and strain. Strain effects have been documented by Nestor and Brown (1972) and the effects of an interesting environmental factor, photophase contrast, has been described by Meyer et al. (1988). Under the conditions of the present study, closed confinement-housed hens with treatments starting in March or September, there does not appear to be justification for exposure of turkey hens to light intensity levels beyond 54 lx during the lay period. However, this does not exclude the possibility that light intensity may in fact influence reproductive performance under other conditions, as noted above. Most notable would be conditions related to season, light-dark contrasts, and type of light source. In addition to reproductive performance, energy utilization in the form of electricity and feed is a major concern in turkey breeder management. Certainly, any power used in lighting above that which allows a maximum response is wasted energy and an economic loss. In addition, increased feed utilization could potentially occur as a consequence of increased maintenance energy requirements associated with increased locomotor activity and metabolic rate induced at higher light intensity levels (Aschoff, 1965; Pohl, 1969; Gwinner, 1975). However, no difference in feed intake or feed efficiency occurred among the 54, 108, and 216 lx light intensity treatments of the present study. It may be concluded from the present study that there is no apparent benefit on reproductive performance of exposing Large White turkey hens in closed confinement to artificial light intensities in excess of 54 lx. REFERENCES Aschoff, J., 1965. Orcadian Clocks. North Holland Publishers, Amsterdam, The Netherlands. Asmundson, V. S., F. W. Lorenz, and B. D. Moses, 1946.
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SIOPES
Influence of light intensity on ovulation in turkeys. Poultry Sci. 25:346-354. Campbell, L. E., L. M. Lucas, J. G. Hartsock, C. P. Davis, and S. J. Marsden, 1960. Experiments with controlled light intensity for turkeys. Trans. Am. Soc. Agric. Eng. 3:45-48. Dobie, J. B„ J. S. Carver, and J. Roberts, 1946. Poultry Lighting for Egg Production. Bulletin 471, Washington State Agricultural Experiment Station, Pullman, WA. Garland, F. W., Jr., R. C. Easton, D. E. Greene, H. L. Wilke, and R. M. Belike, 1961. Duration and intensity of light for out of season egg production in turkeys. Poultry Sci. 40:1406-1407. Gwinner, E., 1975. Orcadian and circannual rhythms in birds. Pages 221-274 in: Avian Biology. Vol. 5. D. S. Farner, J. R. King, and R. C. Parker, ed. Academic Press, New York, NY. Jones, J. E., B. L. Hughes, R. J. Thurston, R. A. Hess, and D. P. Frohman, 1982. The effects of red and white light during the prebreeder and breeder periods on egg production and feed consumption in Large White turkeys. Poultry Sci. 61:1930-1932. Kirkpatnck, C. M., 1955. Factors in photoperiodism of Bobwhite quail. Physiol. Zool. 28:255-264. McCartney, M. G., 1971. Reproduction of turkeys as by age at lighting and light intensity. Poultry Sci. 50:
661-662. Meyer, W. E., J. R. Millam, and F. A. Bradley, 1988. Photostimulation of Japanese quail by dim light depends upon photophase contrast, not light intensity. Biol. Reprod. 38:536-543. Nestor, K. E., and K. I. Brown, 1972. Light intensity and reproduction of turkey hens. Poultry Sci. 51: 117-121. Ostrander, C. E., R. K. Ringer, and H. C. Zindel, 1960. The effect of various light intensities on egg production of Single Comb White Leghorn pullets. Q. Bull. Mich. Agric. Exp. Stn. 43:292-297. Pohl, H., 1969. Some factors influencing the metabolic response to cold in birds. Fed. Proc. 28:1059-1064. SAS Institute, 1982. SAS® User's Guide: Statistics. 1982 ed. SAS Institute, Inc., Cary, NC. Siopes, T. D., 1984. The effect of high and low intensity cool-white fluorescent lighting on the reproductive performance of turkey breeder hens. Poultry Sci. 63: 920-926. Steele, R.GX)., and J. H. Torrie, 1980. Principles and Procedures of Statistics. McGraw-Hill Book Co., New York, NY. Thomason, D. M., A. T. Leighton, Jr., and J. P. Mason, Jr., 1972. A study of certain environmental factors on reproductive performance of Large White turkeys. Poultry Sci. 51:1438-1449.