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Ahemeral lighting of turkey breeder hens. 2. Early age at lighting and reproductive performance
Ahemeral Lighting of Turkey Breeder Hens. 2. Early Age at Lighting and Reproductive Performance1 T. D. SIOPES and E. R. NEELY Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27695-7608 Percentage fertility and hatchability were similar between ahemeral and control treatment groups. However, ahemeral lighting decreased the number of poults per hen when started at 26, but not 30, wk of age. Hens photostimulated early at 26 wk of age were delayed in onset of lay by 5.9 d but produced more eggs per hen to 54 wk of age (95.8) than hens photostimulated at 30 wk (89.7); however, during equivalent lay periods, egg production was similar between the two groups. Early lighting did not have an adverse effect on fertility, hatchability, or poults per hen but egg weight and poult weight were depressed. It was concluded that although ahemeral lighting increased egg weight and poult weight in turkey hens photostimulated early, continuous application of ahemeral lighting throughout the lay period had adverse effects on some components of reproductive performance.
(Key words: turkey, ahemeral light, egg weight, photoperiod, poult weight) 1997 Poultry Science 76:1783–1788
INTRODUCTION To induce egg laying, turkey hens are typically photostimulated with long day lengths in excess of 13 h/d at 29 or 30 wk of age and egg production follows in about 2 to 3 wk. Hens photostimulated at 24 or 26 wk of age have a similar or slightly lower rate of egg production than hens photostimulated at 30 wk of age (Woodard et al., 1974; Siopes, 1992). However, deficiencies may be compensated for by increased time in lay and total egg production (Hocking, 1992). A primary reason hens are not photostimulated at an earlier age than 29 wk is the occurrence of small eggs and the associated small poults (Woodard et al., 1974; Siopes, 1992). A very potent means of increasing egg size is the use of ahemeral lighting (AH), that is, non-24 h light-dark
Received for publication February 24, 1997. Accepted for publication July 31, 1997. 1The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products mentioned, nor criticism of similar products not mentioned.
cycles. Although this increase in egg size has been reported for chickens (review, Shanawany 1982; 1992), similar work in turkeys is sparse. However, we recently reported that egg weight of turkeys increased in a curvilinear manner as cycle lengths increased or decreased from 24 h (Siopes and Neely, 1997). In addition, it appeared that as light-dark cycle lengths increased towards 28 h, egg production remained the same or declined only slightly. These responses seemed to be qualitatively similar to those in chickens with respect to egg weight and rate of lay. Thus, it seemed reasonable that ahemeral lighting might be a useful means of inducing egg laying in turkey hens at an earlier age than is conventional. There exists no previous scientific literature on this subject. Also, information of the effects of ahemeral lighting on fertility, hatchability, and poult quality is nonexistent. However, studies with chickens (review, Shanawany, 1993) indicated no adverse expectations for these factors. The present study was done with turkeys to address the above points using a light-dark cycle length of 28 h. This cycle length was previously determined to be most suitable for maximizing egg weight while minimizing a reduction in egg production (Siopes and Neely, 1997).
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ABSTRACT An experiment was conducted to determine whether ahemeral lighting (AH) could be used to obtain increased egg weight and poult weight and otherwise normal reproductive performance in Large White turkey hens lit as early as 26 wk of age. The experimental design utilized a 2 × 2 factorial arrangement of treatments that evaluated two light cycle lengths (24 h, control and 28 h, ahemeral) at two hen ages (26 and 30 wk). Treatments were continued for 24 wk and the following variables were measured: BW, feed intake, onset and rate of lay, fertility, hatchability, incidence of floor eggs, egg weight, poult production, and poult weight. As compared to the response of hens in the control lighting treatment, ahemeral lighting increased egg weight and poult weight early in the lay period only and resulted in delayed onset of lay (+ 3.4 d) and depressed egg production (–7 eggs to 54 wk of age).
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SIOPES AND NEELY
MATERIALS AND METHODS
RESULTS Light cycle length and age at lighting effects on cumulative eggs per hen and the days required to reach 50% hen-day production are given in Table 1. A 28-h ahemeral light cycle slowed onset of lay by about 3.4 d from that with 24-h cycle lengths and a 5.9 d delay occurred when hens were photostimulated at 26 rather than 30 wk of age. Whereas hens photostimulated at 26 wk of age laid six more eggs by 54 wk of age than those photostimulated at 30 wk, hens given 28-h cycles laid about seven fewer eggs than controls. However, for equivalent treatment periods, egg production was similar for age at lighting but not for cycle length. Biweekly hen-day egg production by weeks of photostimulation (treatment) are presented in Figure 1. From the peak of lay to 24 wk of treatment there was not an age at lighting effect on rate of lay as determined by repeated measures ANOVA. However, ahemeral (28 h) lighting depressed egg production (P = 0.03). Treatment main effects on egg weight are given in Table 2. Hens on 28-h cycles had heavier eggs than those on 24-h cycles to at least 13 wk of treatment. The biggest difference, 2.6 g, occurred with the initially laid eggs. Hens photostimulated at 30 wk of age had heavier eggs (2.9 to 4.4 g range) than those from hens photostimulated at 26 wk throughout the treatment period. Both fertility and hatchability of eggs were similar among the treatment groups (Table 1). This was consistently observed at 5, 12, 17, and 22 wk of photostimulation, so only overall means are presented. Fertility levels exceeded 90% in all treatment groups at
Downloaded from http://ps.oxfordjournals.org/ at University of Findlay on March 17, 2015
An experiment was conducted to determine whether ahemeral lighting could be used to obtain normal reproductive performance and to correct small egg size and poult size in hens photostimulated at 26 wk of age. The hens (Nicholas) were obtained as poults from a commercial breeder during the summer and brooded and reared in a curtain-sided growout house on site. To ensure photosensitivity, all birds were light restricted with 8 h of light/d (8L:16D) from 16 wk of age to lighting (start of treatments). Photostimulation occurred at 26 or 30 wk of age in the months of December and January, respectively, and continued to 54 wk of age. The study was conducted in closed-confinement floor pens with wood shavings litter. The pens were 2.9 × 4.6 m and had four nest boxes and one feeder and waterer. The building used during the study was not temperature controlled but was insulated, and the rooms were mechanically ventilated. Only light from incandescent lamps was used and the mean intensity level was 54 lx at turkey head height, about 66 cm from the floor. Feed and fresh water were provided for ad libitum intake throughout the study. During the prelay light restriction period, the feed was formulated to contain 12% CP, 0.85% calcium, and 3,084 kcal of ME/kg of feed. At the onset of photostimulation, and to the end of the experiment, a breeder ration was fed that was formulated to contain 16% CP, 3.05% calcium, and 2,970 kcal of ME/kg of feed. The experimental design utilized a 2 × 2 factorial arrangement of treatments that evaluated two light cycle lengths (24 h, control vs 28 h, ahemeral) at two hen ages (26 vs 30 wk). There were 20 hens in each of the four treatment groups arranged as four pens of five hens. In each light treatment there was a 15-h photophase per cycle. All light treatments were controlled by computer and validated on an electronic recorder. Individual BW were obtained every 4 wk from the start of treatments. In addition, feed intake was determined, by pen, in 7-d periods immediately preceding the BW determinations. Eggs were collected a minimum of four times during the photophase throughout the study, and the number of eggs laid on the floor or in the nest was recorded by pen. Time to onset of lay was defined as days to reach 50% hen-day egg production from the start of the light treatments. Egg production was evaluated as cumulative eggs produced per hen or as a weekly hen-day percentage. All hen-day egg production values were based on a 24-h day. Individual egg weights were obtained for the first 7 d of lay in each pen. In addition, egg weights were obtained in 7-d periods immediately preceding 8, 13, 17, and 23 wk of photostimulation. 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 0.03 mL of extended semen was inseminated per hen. Two consecutive
weekly inseminations were given immediately prior to each of four 7-d egg collection periods ending at 5, 12, 17, and 22 wk of photostimulation. Eggs were stored at about 13 C and 75% relative humidity and placed in incubators within 7 d of collection. Percentage true fertility was determined by candling eggs after 14 d of incubation and breaking out eggs to differentiate earlydead from infertiles. Percentage hatch was the percentage of hatch from all fertile eggs. Incubators were checked for poults on Day 26, 27, and 28 of incubation and at each check poults were removed and weighed immediately. A two-way ANOVA was used to evaluate the treatment effects using the General Linear Models (GLM) procedure of SAS software (SAS Institute, 1990). Main effects were light cycle (24 vs 28 h), and age at lighting (26 vs 30 wk). Where no significant treatment interaction occurred, results are presented as main effects only. The arc sine transformation was applied to all percentage data prior to analysis. In addition, repeated measures ANOVA was used to evaluate rate of lay occurring from post-peak production. The least squares means option was used to estimate significant differences among treatment means. Statements of statistical significance are based on P ≤ 0.05 unless specified otherwise.
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AHEMERAL LIGHTING TABLE 1. Light cycle length and age at lighting main effect means for the onset of lay, cumulative eggs per hen to 54 wk of age and for equal treatment periods, percentage fertility, and percentage hatch of fertile eggs. Associated root mean square error (RMSE) and statistical probabilities are also given Eggs per hen Days to 50% production1
Treatment
54 wk of age
24 wk of treatment
Percentage fertility
(%)
(d) Cycle length (CL) 24 h 28 h Age 26 h 30 h RMSE
1From 2Mean
19.6 23.0
96.4 89.1
93.0 84.3
93.0 95.4
81.4 78.0
24.3 18.4 2.8
95.8 89.7 5.7
87.5 89.8 5.7 Probability
92.6 95.7 6.6
79.4 79.8 11.2
0.03 0.001 NS
0.03 0.05 NS
0.01 0.45 NS
0.15 0.06 NS
0.20 0.89 NS
start of treatment. of eggs set at 5, 12, 17, and 22 wk of treatment. For each mean n = 611 to 647.
all assessment times. Likewise, hatchability always exceeded 70%. Poult production from each of the treatment groups is presented in Table 3. Because the cycle length by age interaction was marginally significant, treatment means as well as main effect means are given. Cycle lengths of 28 h had an adverse effect on poult production when hens were photostimulated at 26 wk of age but not at 30 wk of age. Age at lighting did not significantly affect poult production. Treatment effects on poult weight from four hatches are given in Table 4. Ahemeral lighting increased poult weight whereas early lighting decreased poult weight. Both responses were transient, being most evident in the first half of the lay period. There were no significant differences in BW or feed intake among treatment groups evaluated at six weekly periods through 24 wk of photostimulation. Body weight at the start of photostimulation ranged from 10.1 to 10.9 kg, whereas the overall mean feed intake ranged from 23.5 to 24.6 g/kg BW per d.
DISCUSSION When turkey hens were photostimulated at 26 rather than 30 wk of age, egg weight was reduced and remained reduced throughout 23 wk of photostimulation. This effect was not dependent on BW, and is in agreement with previous reports by Woodard et al. (1974) and Siopes (1992) but not with that of Hocking (1992). Hens photostimulated at 26 wk of age also had a delayed onset of lay but nevertheless produced more eggs per hen to 54 wk of age (96) than hens photostimulated at 30 wk of age (90 eggs per hen) (Table 1). However, this result was more a consequence of
FIGURE 1. Mean biweekly percentage hen-day egg production of turkey hens photostimulated at either 30 or 26 wk of age (bottom) with 24 or 28 light-dark cycle lengths (top). The photophase was 15 h in each cycle. Each mean derived from the response of 40 hens in eight pens and the pooled SEM from repeated measures ANOVA is 5.3. Age at lighting and light cycle length interaction was not significant (P ≤ 0.05).
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Variable CL Age CL × age
Percentage hatch of fertile eggs
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SIOPES AND NEELY TABLE 2. Mean egg weights as influenced by cycle length and age of photostimulation for the first 7 d of lay and for 7-d laying periods ending 8, 13, 17, and 23 wk after photostimulation (n = 100 – 103 eggs/mean)
Treatment
First 7 d of lay
Weeks of photostimulation 8
13
17
23
x
(g) Cycle length (CL) 24 h 28 h Age 26 wk 30 wk RMSE
83.8 86.2
88.8 90.4
92.2 92.3
94.2 93.8
98.8 90.7
74.0 77.0 7.1
82.6 87.0 6.5
88.1 91.1 91.0 93.3 6.1 6.1 Probability
92.9 95.2 6.6
88.7 91.6 7.4
0.002 0.008 0.78
extended time in lay rather than increased rate of lay and, as such, is in agreement with previous reports (Woodard et al., 1974; Hocking, 1992; Siopes, 1992). Other than the delayed onset of lay, the rate of egg production by hens photostimulated at 26 wk of age was generally similar to that of hens photostimulated at 30 wk during equal treatment periods (Table 1, Figure 1). Thus, egg weight is a more prominent problem with early lighting than is egg production when using standard lighting cycles. There are reports of reduced egg production and/or egg quality when turkeys are photostimulated at 26 wk or earlier (Woodard et al., 1974; Hocking, 1992; Siopes, 1992). These deficiencies have been explained by Hocking et al. (1988) and Hocking (1992) as caused by abnormal (multiple) follicular development. The response of turkey hens to ahemeral lighting was consistent with our previous report (Siopes and Neely, 1997) with respect to egg production and egg weight. That is, a slight decrease in egg production but increased egg weight. This result is also in agreement with the reported inverse relationship between egg production and egg weight in chickens (Shanawany, 1982). As noted in an earlier report (Siopes and Neely, 1997), there was a significant increase in the number of floor eggs from hens treated with ahemeral lighting. The incidence of floor eggs during the 24-wk treatment was about 12% in the 24-h control light treatments and 43 to 46% in the ahemeral light treatments; quite similar to the values previously reported. There was no adverse effect of early age at lighting on incidence of floor eggs. It seems clear from the results of the present study that an ahemeral photoperiod providing 15 h of light in 28-h cycles (15 h light:13 h dark) can increase the weight of the initially laid eggs and thus overcome the adverse effect of early lighting on egg weight. The effect on egg weight persisted to 13 wk of photostimulation but not to 17 or 23 wk, even though the ahemeral lighting was present continuously. This transient effect appeared to
0.0007 0.0001 0.10
0.02 0.0001 0.93
0.89 0.003 0.56
0.60 0.015 0.83
0.003 0.0001 0.40
be more a consequence of increasing egg weight in controls than diminished effect of ahemeral lighting. As with early photostimulated hens, the effects of ahemeral lighting on egg weights were not dependent on BW or feed intake. The hens exposed to ahemeral lighting had delayed onset of lay and also produced about nine fewer eggs per hen (P = 0.01) during 24 wk of treatment than the controls. Egg production was consistently lowest in the ahemeral treatment through 20 wk of photostimulation (Figure 1) and, from peak lay to 24 wk, this response was significant (P = 0.03). This was consistent with previous studies (Siopes and Neely, 1997), in which egg production declined sequentially as cycle lengths in-
TABLE 3. Light cycle length and age at lighting effects on mean poults produced per hen. Each mean derived from hatches at 5, 12, 17, and 22 wk of photostimulation
Treatments 24 h, 26 wk 24 h, 30 wk 28 h, 26 wk 28 h, 30 wk RMSE Main effects Cycle length (CL) 24 h 28 h Age 26 wk 30 wk Variable CL Age CL × age
x number poults/hen/hatch
Total poults/hen
3.2 2.8 2.6 3.0 0.89
12.3a 11.0ab 10.2b 12.0ab 1.3
2.9 2.8
11.7 11.1
2.8 2.9
11.3 11.5 Probability
0.57 0.74 0.09
0.43 0.70 0.04
a,bMeans in a column with no common superscript differ significantly (P ≤ 0.05).
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Variable CL Age CL × age
74.2 76.8
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AHEMERAL LIGHTING TABLE 4. Cycle length and age at lighting effects on poult weights from four hatches over the treatment period. The number of poults for each mean ranged from 82 to 149 Weeks of photostimulation Treatment
5
12
17
22
(g) Cycle length (CL) 24 h 28 h Age 26 wk 30 wk RMSE
54.7 55.7
57.1 59.3
64.3 60.7
50.3 55.1 1.8
52.9 59.3 57.5 57.1 1.5 1.5 Probability
64.5 60.6 10.9
0.03 0.0003 NS
0.08 0.002 NS
0.54 0.50 NS
0.02 0.02 NS
creased from 23 to 28 h in duration. Actually, it might be expected that onset of lay would be delayed and rate of egg production would be reduced on 28-h light-dark cycles. In a fixed period of time, there are fewer total cycles with 28- than 24-h periods. If one egg is laid per cycle, fewer eggs will be produced with 28- than 24-h cycles. As has been reported by others (Woodard et al., 1974; Hocking, 1992), early lighting of turkey hens had no adverse effect on fertility or hatchability of eggs. Likewise, ahemeral lighting had no significant effect on either of these factors in the present study and this is the first report of such a response in turkeys. It is notable that for each of the four hatches, fertility was consistently higher in hens receiving ahermeral lighting than controls, whereas hatchability was consistently lower. The degree of difference was about the same in both cases. The adverse effects of using ahemeral lighting may be summarized as a slight delay in onset of lay, a slightly decreased egg production, and a consistent, but not significant, decline in hatchability. Any one of these effects may be tolerable, but together they present what could be an important problem. This problem expresses itself when all these factors converge on the bottom-line factor for breeder hens, that is, poult production. As presented in Table 4, total poults per hen for four hatches had a marginally significant (P = 0.04) interaction between light-dark cycle length and age at lighting. This interaction was because ahemeral lighting had an adverse effect on number of poults per hen when applied at 26, but not 30, wk of age. This effect seems to be a consequence of compounding of otherwise minimally adverse effects, most notably fewer eggs and, secondarily, a consistent but slight decrease in hatchability. Lighting at 26 wk of age did not significantly alter the number of poults per hen from that for hens photostimulated at 30 wk as determined from four hatches.
ACKNOWLEDGMENT The study was supported by funds provided by U. S. Poultry and Egg Association, Tucker, GA 30084.
REFERENCES Applegate, T. J., and M. S. Lilburn, 1996. Independent effects of hen age and egg size on incubation and poult characteristics in commercial turkeys. Poultry Sci. 75:1210–1216. Fitzsimmons, R. C., and M. Newcombe, 1991. The effects of ahemeral light-dark cycles early in the laying cycle on egg
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Variable CL Age CL × age
51.5 53.9
This result was not surprising, as rate of lay and hatchability were similar between the two groups. However, to a given age, such as 54 wk, early lighting should improve poult production as a consequence of more time in lay. It was clear from the results that ahemeral lighting increased poult weight and that early lighting decreased poult weight. However, both of these effects were transient, as ahemeral lighting effects persisted to 17 wk of photostimulation whereas early lighting effects disappeared between 12 and 17 wk of photostimulation. This latter response was very similar to that reported earlier in turkey hens (Siopes, 1992). It appears that at least a part of the cause of the disappearance of response was due to increasing egg weight (and associated larger poult weight) in the groups with smaller poults rather than a reduction in treatment effects causing the larger poult weight. With respect to the initially (early) laid eggs, it is important to note that the increased egg weight induced by ahemeral lighting was reflected in a proportional increase in poult weight. This increase in poult weight did not occur later in the lay period. Poult weight increases with increasing egg weight (Siopes, 1992; Applegate and Lilburn, 1996). However, there is some question as to the degree of importance of egg weight in this response. For example, whereas ahemeral effects on increasing poult weight persisted to 17 wk of photostimulation, egg weight was not different from controls at 17 wk and later. In addition, depressed poult weight due to early lighting persisted only to 12 wk of photostimulation, but egg weight was depressed throughout 23 wk of photostimulation. These responses, especially when poult weight per unit egg weight is evaluated, suggest that some of the changes in poult weight may be independent of egg weight. This effect was also indicated in an earlier publication (Siopes, 1992). There are some detrimental effects on reproductive performance of hens when ahemeral lighting is applied throughout the lay period. Because beneficial effects on egg weight and poult weight occur most prominently early in lay, the possibility exists for a transient, early use of ahemeral lighting to maximize benefits and minimize adverse effects. This early use has been addressed in chickens with both negative and positive results (Zimmermann and Nam, 1989; Fitzsimmons and Newcombe, 1991; Hawes et al., 1991; Shanawany, 1992).
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SIOPES AND NEELY Shanawany, M. M., 1992. Response of layers to ahemeral light cycles incorporating age at applications and change in effective photoperiod. World’s Poult. Sci. J. 48:156–164. Shanawany, M. M., 1993. Ahemeral lighting and reproduction efficiency in breeding flocks. World’s Poult. Sci. J. 49: 213–218. Siopes, T. D., 1992. Effects of age at lighting on reproduction of turkey hens. Poultry Sci. 71:2099–2105. Siopes, T. D., and E. R. Neely, 1997. Ahemeral lighting of turkey breeder hens: I. Cycle length effects on egg production and egg characteristics. Poultry Sci. 76: 761–766. Woodard, H. E., H. Abplanalp, V. Stinnett, and R. L. Snyder, 1974. The effect of age at lighting on egg production and pausing in turkey hens. Poultry Sci. 53:1681–1686. Zimmermann, N. G., and C. H. Nam, 1989. Temporary ahemeral lighting for increased egg size in maturing pullets. Poultry Sci. 68:1624–1630.
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production in White Leghorn hens. Poultry Sci. 70:20–25. Hawes, R. O., N. Lakshmanan, and L. J. Kling, 1991. Effect of ahemeral light:dark cycles on egg production in early photostimulated brown-egg poults. Poultry Sci. 70: 1481–1486. Hocking, P. M., A. B. Gilbert, C. C. Whitehead, and M. H. Walker, 1988. Effects of age and of early lighting on ovarian function in breeding turkeys. Br. Poult. Sci. 29: 223–229. Hocking, P. M., 1992. Effects of photostimulation at 11, 24, and 30 weeks of age on the productivity of female turkeys fed ad libitum or restricted until point of lay. Br. Poult. Sci. 33: 253–269. SAS Institute, 1990. SAS/STAT User’s Guide. Version 6. Fourth Edition. Vol. 2. SAS Institute Inc., Cary, NC. Shanawany, M. M., 1982. The effect of ahemeral light and dark cycles on the performance of laying hens. World’s Poult. Sci. J. 38:120–126.
(Key words: turkey, ahemeral light, egg weight, photoperiod, poult weight) 1997 Poultry Science 76:1783–1788
INTRODUCTION To induce egg laying, turkey hens are typically photostimulated with long day lengths in excess of 13 h/d at 29 or 30 wk of age and egg production follows in about 2 to 3 wk. Hens photostimulated at 24 or 26 wk of age have a similar or slightly lower rate of egg production than hens photostimulated at 30 wk of age (Woodard et al., 1974; Siopes, 1992). However, deficiencies may be compensated for by increased time in lay and total egg production (Hocking, 1992). A primary reason hens are not photostimulated at an earlier age than 29 wk is the occurrence of small eggs and the associated small poults (Woodard et al., 1974; Siopes, 1992). A very potent means of increasing egg size is the use of ahemeral lighting (AH), that is, non-24 h light-dark
Received for publication February 24, 1997. Accepted for publication July 31, 1997. 1The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products mentioned, nor criticism of similar products not mentioned.
cycles. Although this increase in egg size has been reported for chickens (review, Shanawany 1982; 1992), similar work in turkeys is sparse. However, we recently reported that egg weight of turkeys increased in a curvilinear manner as cycle lengths increased or decreased from 24 h (Siopes and Neely, 1997). In addition, it appeared that as light-dark cycle lengths increased towards 28 h, egg production remained the same or declined only slightly. These responses seemed to be qualitatively similar to those in chickens with respect to egg weight and rate of lay. Thus, it seemed reasonable that ahemeral lighting might be a useful means of inducing egg laying in turkey hens at an earlier age than is conventional. There exists no previous scientific literature on this subject. Also, information of the effects of ahemeral lighting on fertility, hatchability, and poult quality is nonexistent. However, studies with chickens (review, Shanawany, 1993) indicated no adverse expectations for these factors. The present study was done with turkeys to address the above points using a light-dark cycle length of 28 h. This cycle length was previously determined to be most suitable for maximizing egg weight while minimizing a reduction in egg production (Siopes and Neely, 1997).
1783
Downloaded from http://ps.oxfordjournals.org/ at University of Findlay on March 17, 2015
ABSTRACT An experiment was conducted to determine whether ahemeral lighting (AH) could be used to obtain increased egg weight and poult weight and otherwise normal reproductive performance in Large White turkey hens lit as early as 26 wk of age. The experimental design utilized a 2 × 2 factorial arrangement of treatments that evaluated two light cycle lengths (24 h, control and 28 h, ahemeral) at two hen ages (26 and 30 wk). Treatments were continued for 24 wk and the following variables were measured: BW, feed intake, onset and rate of lay, fertility, hatchability, incidence of floor eggs, egg weight, poult production, and poult weight. As compared to the response of hens in the control lighting treatment, ahemeral lighting increased egg weight and poult weight early in the lay period only and resulted in delayed onset of lay (+ 3.4 d) and depressed egg production (–7 eggs to 54 wk of age).
1784
SIOPES AND NEELY
MATERIALS AND METHODS
RESULTS Light cycle length and age at lighting effects on cumulative eggs per hen and the days required to reach 50% hen-day production are given in Table 1. A 28-h ahemeral light cycle slowed onset of lay by about 3.4 d from that with 24-h cycle lengths and a 5.9 d delay occurred when hens were photostimulated at 26 rather than 30 wk of age. Whereas hens photostimulated at 26 wk of age laid six more eggs by 54 wk of age than those photostimulated at 30 wk, hens given 28-h cycles laid about seven fewer eggs than controls. However, for equivalent treatment periods, egg production was similar for age at lighting but not for cycle length. Biweekly hen-day egg production by weeks of photostimulation (treatment) are presented in Figure 1. From the peak of lay to 24 wk of treatment there was not an age at lighting effect on rate of lay as determined by repeated measures ANOVA. However, ahemeral (28 h) lighting depressed egg production (P = 0.03). Treatment main effects on egg weight are given in Table 2. Hens on 28-h cycles had heavier eggs than those on 24-h cycles to at least 13 wk of treatment. The biggest difference, 2.6 g, occurred with the initially laid eggs. Hens photostimulated at 30 wk of age had heavier eggs (2.9 to 4.4 g range) than those from hens photostimulated at 26 wk throughout the treatment period. Both fertility and hatchability of eggs were similar among the treatment groups (Table 1). This was consistently observed at 5, 12, 17, and 22 wk of photostimulation, so only overall means are presented. Fertility levels exceeded 90% in all treatment groups at
Downloaded from http://ps.oxfordjournals.org/ at University of Findlay on March 17, 2015
An experiment was conducted to determine whether ahemeral lighting could be used to obtain normal reproductive performance and to correct small egg size and poult size in hens photostimulated at 26 wk of age. The hens (Nicholas) were obtained as poults from a commercial breeder during the summer and brooded and reared in a curtain-sided growout house on site. To ensure photosensitivity, all birds were light restricted with 8 h of light/d (8L:16D) from 16 wk of age to lighting (start of treatments). Photostimulation occurred at 26 or 30 wk of age in the months of December and January, respectively, and continued to 54 wk of age. The study was conducted in closed-confinement floor pens with wood shavings litter. The pens were 2.9 × 4.6 m and had four nest boxes and one feeder and waterer. The building used during the study was not temperature controlled but was insulated, and the rooms were mechanically ventilated. Only light from incandescent lamps was used and the mean intensity level was 54 lx at turkey head height, about 66 cm from the floor. Feed and fresh water were provided for ad libitum intake throughout the study. During the prelay light restriction period, the feed was formulated to contain 12% CP, 0.85% calcium, and 3,084 kcal of ME/kg of feed. At the onset of photostimulation, and to the end of the experiment, a breeder ration was fed that was formulated to contain 16% CP, 3.05% calcium, and 2,970 kcal of ME/kg of feed. The experimental design utilized a 2 × 2 factorial arrangement of treatments that evaluated two light cycle lengths (24 h, control vs 28 h, ahemeral) at two hen ages (26 vs 30 wk). There were 20 hens in each of the four treatment groups arranged as four pens of five hens. In each light treatment there was a 15-h photophase per cycle. All light treatments were controlled by computer and validated on an electronic recorder. Individual BW were obtained every 4 wk from the start of treatments. In addition, feed intake was determined, by pen, in 7-d periods immediately preceding the BW determinations. Eggs were collected a minimum of four times during the photophase throughout the study, and the number of eggs laid on the floor or in the nest was recorded by pen. Time to onset of lay was defined as days to reach 50% hen-day egg production from the start of the light treatments. Egg production was evaluated as cumulative eggs produced per hen or as a weekly hen-day percentage. All hen-day egg production values were based on a 24-h day. Individual egg weights were obtained for the first 7 d of lay in each pen. In addition, egg weights were obtained in 7-d periods immediately preceding 8, 13, 17, and 23 wk of photostimulation. 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 0.03 mL of extended semen was inseminated per hen. Two consecutive
weekly inseminations were given immediately prior to each of four 7-d egg collection periods ending at 5, 12, 17, and 22 wk of photostimulation. Eggs were stored at about 13 C and 75% relative humidity and placed in incubators within 7 d of collection. Percentage true fertility was determined by candling eggs after 14 d of incubation and breaking out eggs to differentiate earlydead from infertiles. Percentage hatch was the percentage of hatch from all fertile eggs. Incubators were checked for poults on Day 26, 27, and 28 of incubation and at each check poults were removed and weighed immediately. A two-way ANOVA was used to evaluate the treatment effects using the General Linear Models (GLM) procedure of SAS software (SAS Institute, 1990). Main effects were light cycle (24 vs 28 h), and age at lighting (26 vs 30 wk). Where no significant treatment interaction occurred, results are presented as main effects only. The arc sine transformation was applied to all percentage data prior to analysis. In addition, repeated measures ANOVA was used to evaluate rate of lay occurring from post-peak production. The least squares means option was used to estimate significant differences among treatment means. Statements of statistical significance are based on P ≤ 0.05 unless specified otherwise.
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AHEMERAL LIGHTING TABLE 1. Light cycle length and age at lighting main effect means for the onset of lay, cumulative eggs per hen to 54 wk of age and for equal treatment periods, percentage fertility, and percentage hatch of fertile eggs. Associated root mean square error (RMSE) and statistical probabilities are also given Eggs per hen Days to 50% production1
Treatment
54 wk of age
24 wk of treatment
Percentage fertility
(%)
(d) Cycle length (CL) 24 h 28 h Age 26 h 30 h RMSE
1From 2Mean
19.6 23.0
96.4 89.1
93.0 84.3
93.0 95.4
81.4 78.0
24.3 18.4 2.8
95.8 89.7 5.7
87.5 89.8 5.7 Probability
92.6 95.7 6.6
79.4 79.8 11.2
0.03 0.001 NS
0.03 0.05 NS
0.01 0.45 NS
0.15 0.06 NS
0.20 0.89 NS
start of treatment. of eggs set at 5, 12, 17, and 22 wk of treatment. For each mean n = 611 to 647.
all assessment times. Likewise, hatchability always exceeded 70%. Poult production from each of the treatment groups is presented in Table 3. Because the cycle length by age interaction was marginally significant, treatment means as well as main effect means are given. Cycle lengths of 28 h had an adverse effect on poult production when hens were photostimulated at 26 wk of age but not at 30 wk of age. Age at lighting did not significantly affect poult production. Treatment effects on poult weight from four hatches are given in Table 4. Ahemeral lighting increased poult weight whereas early lighting decreased poult weight. Both responses were transient, being most evident in the first half of the lay period. There were no significant differences in BW or feed intake among treatment groups evaluated at six weekly periods through 24 wk of photostimulation. Body weight at the start of photostimulation ranged from 10.1 to 10.9 kg, whereas the overall mean feed intake ranged from 23.5 to 24.6 g/kg BW per d.
DISCUSSION When turkey hens were photostimulated at 26 rather than 30 wk of age, egg weight was reduced and remained reduced throughout 23 wk of photostimulation. This effect was not dependent on BW, and is in agreement with previous reports by Woodard et al. (1974) and Siopes (1992) but not with that of Hocking (1992). Hens photostimulated at 26 wk of age also had a delayed onset of lay but nevertheless produced more eggs per hen to 54 wk of age (96) than hens photostimulated at 30 wk of age (90 eggs per hen) (Table 1). However, this result was more a consequence of
FIGURE 1. Mean biweekly percentage hen-day egg production of turkey hens photostimulated at either 30 or 26 wk of age (bottom) with 24 or 28 light-dark cycle lengths (top). The photophase was 15 h in each cycle. Each mean derived from the response of 40 hens in eight pens and the pooled SEM from repeated measures ANOVA is 5.3. Age at lighting and light cycle length interaction was not significant (P ≤ 0.05).
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Variable CL Age CL × age
Percentage hatch of fertile eggs
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SIOPES AND NEELY TABLE 2. Mean egg weights as influenced by cycle length and age of photostimulation for the first 7 d of lay and for 7-d laying periods ending 8, 13, 17, and 23 wk after photostimulation (n = 100 – 103 eggs/mean)
Treatment
First 7 d of lay
Weeks of photostimulation 8
13
17
23
x
(g) Cycle length (CL) 24 h 28 h Age 26 wk 30 wk RMSE
83.8 86.2
88.8 90.4
92.2 92.3
94.2 93.8
98.8 90.7
74.0 77.0 7.1
82.6 87.0 6.5
88.1 91.1 91.0 93.3 6.1 6.1 Probability
92.9 95.2 6.6
88.7 91.6 7.4
0.002 0.008 0.78
extended time in lay rather than increased rate of lay and, as such, is in agreement with previous reports (Woodard et al., 1974; Hocking, 1992; Siopes, 1992). Other than the delayed onset of lay, the rate of egg production by hens photostimulated at 26 wk of age was generally similar to that of hens photostimulated at 30 wk during equal treatment periods (Table 1, Figure 1). Thus, egg weight is a more prominent problem with early lighting than is egg production when using standard lighting cycles. There are reports of reduced egg production and/or egg quality when turkeys are photostimulated at 26 wk or earlier (Woodard et al., 1974; Hocking, 1992; Siopes, 1992). These deficiencies have been explained by Hocking et al. (1988) and Hocking (1992) as caused by abnormal (multiple) follicular development. The response of turkey hens to ahemeral lighting was consistent with our previous report (Siopes and Neely, 1997) with respect to egg production and egg weight. That is, a slight decrease in egg production but increased egg weight. This result is also in agreement with the reported inverse relationship between egg production and egg weight in chickens (Shanawany, 1982). As noted in an earlier report (Siopes and Neely, 1997), there was a significant increase in the number of floor eggs from hens treated with ahemeral lighting. The incidence of floor eggs during the 24-wk treatment was about 12% in the 24-h control light treatments and 43 to 46% in the ahemeral light treatments; quite similar to the values previously reported. There was no adverse effect of early age at lighting on incidence of floor eggs. It seems clear from the results of the present study that an ahemeral photoperiod providing 15 h of light in 28-h cycles (15 h light:13 h dark) can increase the weight of the initially laid eggs and thus overcome the adverse effect of early lighting on egg weight. The effect on egg weight persisted to 13 wk of photostimulation but not to 17 or 23 wk, even though the ahemeral lighting was present continuously. This transient effect appeared to
0.0007 0.0001 0.10
0.02 0.0001 0.93
0.89 0.003 0.56
0.60 0.015 0.83
0.003 0.0001 0.40
be more a consequence of increasing egg weight in controls than diminished effect of ahemeral lighting. As with early photostimulated hens, the effects of ahemeral lighting on egg weights were not dependent on BW or feed intake. The hens exposed to ahemeral lighting had delayed onset of lay and also produced about nine fewer eggs per hen (P = 0.01) during 24 wk of treatment than the controls. Egg production was consistently lowest in the ahemeral treatment through 20 wk of photostimulation (Figure 1) and, from peak lay to 24 wk, this response was significant (P = 0.03). This was consistent with previous studies (Siopes and Neely, 1997), in which egg production declined sequentially as cycle lengths in-
TABLE 3. Light cycle length and age at lighting effects on mean poults produced per hen. Each mean derived from hatches at 5, 12, 17, and 22 wk of photostimulation
Treatments 24 h, 26 wk 24 h, 30 wk 28 h, 26 wk 28 h, 30 wk RMSE Main effects Cycle length (CL) 24 h 28 h Age 26 wk 30 wk Variable CL Age CL × age
x number poults/hen/hatch
Total poults/hen
3.2 2.8 2.6 3.0 0.89
12.3a 11.0ab 10.2b 12.0ab 1.3
2.9 2.8
11.7 11.1
2.8 2.9
11.3 11.5 Probability
0.57 0.74 0.09
0.43 0.70 0.04
a,bMeans in a column with no common superscript differ significantly (P ≤ 0.05).
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Variable CL Age CL × age
74.2 76.8
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AHEMERAL LIGHTING TABLE 4. Cycle length and age at lighting effects on poult weights from four hatches over the treatment period. The number of poults for each mean ranged from 82 to 149 Weeks of photostimulation Treatment
5
12
17
22
(g) Cycle length (CL) 24 h 28 h Age 26 wk 30 wk RMSE
54.7 55.7
57.1 59.3
64.3 60.7
50.3 55.1 1.8
52.9 59.3 57.5 57.1 1.5 1.5 Probability
64.5 60.6 10.9
0.03 0.0003 NS
0.08 0.002 NS
0.54 0.50 NS
0.02 0.02 NS
creased from 23 to 28 h in duration. Actually, it might be expected that onset of lay would be delayed and rate of egg production would be reduced on 28-h light-dark cycles. In a fixed period of time, there are fewer total cycles with 28- than 24-h periods. If one egg is laid per cycle, fewer eggs will be produced with 28- than 24-h cycles. As has been reported by others (Woodard et al., 1974; Hocking, 1992), early lighting of turkey hens had no adverse effect on fertility or hatchability of eggs. Likewise, ahemeral lighting had no significant effect on either of these factors in the present study and this is the first report of such a response in turkeys. It is notable that for each of the four hatches, fertility was consistently higher in hens receiving ahermeral lighting than controls, whereas hatchability was consistently lower. The degree of difference was about the same in both cases. The adverse effects of using ahemeral lighting may be summarized as a slight delay in onset of lay, a slightly decreased egg production, and a consistent, but not significant, decline in hatchability. Any one of these effects may be tolerable, but together they present what could be an important problem. This problem expresses itself when all these factors converge on the bottom-line factor for breeder hens, that is, poult production. As presented in Table 4, total poults per hen for four hatches had a marginally significant (P = 0.04) interaction between light-dark cycle length and age at lighting. This interaction was because ahemeral lighting had an adverse effect on number of poults per hen when applied at 26, but not 30, wk of age. This effect seems to be a consequence of compounding of otherwise minimally adverse effects, most notably fewer eggs and, secondarily, a consistent but slight decrease in hatchability. Lighting at 26 wk of age did not significantly alter the number of poults per hen from that for hens photostimulated at 30 wk as determined from four hatches.
ACKNOWLEDGMENT The study was supported by funds provided by U. S. Poultry and Egg Association, Tucker, GA 30084.
REFERENCES Applegate, T. J., and M. S. Lilburn, 1996. Independent effects of hen age and egg size on incubation and poult characteristics in commercial turkeys. Poultry Sci. 75:1210–1216. Fitzsimmons, R. C., and M. Newcombe, 1991. The effects of ahemeral light-dark cycles early in the laying cycle on egg
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Variable CL Age CL × age
51.5 53.9
This result was not surprising, as rate of lay and hatchability were similar between the two groups. However, to a given age, such as 54 wk, early lighting should improve poult production as a consequence of more time in lay. It was clear from the results that ahemeral lighting increased poult weight and that early lighting decreased poult weight. However, both of these effects were transient, as ahemeral lighting effects persisted to 17 wk of photostimulation whereas early lighting effects disappeared between 12 and 17 wk of photostimulation. This latter response was very similar to that reported earlier in turkey hens (Siopes, 1992). It appears that at least a part of the cause of the disappearance of response was due to increasing egg weight (and associated larger poult weight) in the groups with smaller poults rather than a reduction in treatment effects causing the larger poult weight. With respect to the initially (early) laid eggs, it is important to note that the increased egg weight induced by ahemeral lighting was reflected in a proportional increase in poult weight. This increase in poult weight did not occur later in the lay period. Poult weight increases with increasing egg weight (Siopes, 1992; Applegate and Lilburn, 1996). However, there is some question as to the degree of importance of egg weight in this response. For example, whereas ahemeral effects on increasing poult weight persisted to 17 wk of photostimulation, egg weight was not different from controls at 17 wk and later. In addition, depressed poult weight due to early lighting persisted only to 12 wk of photostimulation, but egg weight was depressed throughout 23 wk of photostimulation. These responses, especially when poult weight per unit egg weight is evaluated, suggest that some of the changes in poult weight may be independent of egg weight. This effect was also indicated in an earlier publication (Siopes, 1992). There are some detrimental effects on reproductive performance of hens when ahemeral lighting is applied throughout the lay period. Because beneficial effects on egg weight and poult weight occur most prominently early in lay, the possibility exists for a transient, early use of ahemeral lighting to maximize benefits and minimize adverse effects. This early use has been addressed in chickens with both negative and positive results (Zimmermann and Nam, 1989; Fitzsimmons and Newcombe, 1991; Hawes et al., 1991; Shanawany, 1992).
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SIOPES AND NEELY Shanawany, M. M., 1992. Response of layers to ahemeral light cycles incorporating age at applications and change in effective photoperiod. World’s Poult. Sci. J. 48:156–164. Shanawany, M. M., 1993. Ahemeral lighting and reproduction efficiency in breeding flocks. World’s Poult. Sci. J. 49: 213–218. Siopes, T. D., 1992. Effects of age at lighting on reproduction of turkey hens. Poultry Sci. 71:2099–2105. Siopes, T. D., and E. R. Neely, 1997. Ahemeral lighting of turkey breeder hens: I. Cycle length effects on egg production and egg characteristics. Poultry Sci. 76: 761–766. Woodard, H. E., H. Abplanalp, V. Stinnett, and R. L. Snyder, 1974. The effect of age at lighting on egg production and pausing in turkey hens. Poultry Sci. 53:1681–1686. Zimmermann, N. G., and C. H. Nam, 1989. Temporary ahemeral lighting for increased egg size in maturing pullets. Poultry Sci. 68:1624–1630.
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production in White Leghorn hens. Poultry Sci. 70:20–25. Hawes, R. O., N. Lakshmanan, and L. J. Kling, 1991. Effect of ahemeral light:dark cycles on egg production in early photostimulated brown-egg poults. Poultry Sci. 70: 1481–1486. Hocking, P. M., A. B. Gilbert, C. C. Whitehead, and M. H. Walker, 1988. Effects of age and of early lighting on ovarian function in breeding turkeys. Br. Poult. Sci. 29: 223–229. Hocking, P. M., 1992. Effects of photostimulation at 11, 24, and 30 weeks of age on the productivity of female turkeys fed ad libitum or restricted until point of lay. Br. Poult. Sci. 33: 253–269. SAS Institute, 1990. SAS/STAT User’s Guide. Version 6. Fourth Edition. Vol. 2. SAS Institute Inc., Cary, NC. Shanawany, M. M., 1982. The effect of ahemeral light and dark cycles on the performance of laying hens. World’s Poult. Sci. J. 38:120–126.