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Reproductive Development and Response of White Leghorn Pullets Subjected to Increasing Day-Lengths at Different Ages1
ETHOPABATE TOLERANCE
p.p.m. during the first week, as these birds gained 14.3% less (P = 0.01) than controls. Interestingly enough, growth in the birds at this level gradually improved, so that during the last week of the trial they grew only 4% less than control birds. The results of these experiments indicate that the tolerance of chickens for ethopabate is approximately 100 p.p.m. when it is administered in a growing ration containing 100 p.p.m. of amproHum. SUMMARY
The tolerance of growing chickens for
1021
ethopabate when given in a ration containing 100 p.p.m. of amprolium was studied in two experiments using a total of 700 broiler chicks. Measured in terms of growth, 80 to 100 p.p.m. of ethopabate were tolerated without significant effects. At these levels, a slight and transient depression of growth was seen in the second week of the experiment, indicating that these doses must be taken as a tolerance limit. When the drug concentration was raised to 200 p.p.m. or more, marked depression in early growth was produced. No appreciable negative influences on feed consumption were observed.
Reproductive Development and Response of White Leghorn Pullets Subjected to Increasing Day-Lengths at Different Ages1 P. C. HARRISON, G. SCHUMAIER AND J. MCGINNIS Department of Animal Sciences, Washington State University, Pullman, Washington 99163 (Received for publication November 28, 1968)
R
EPRODUCTIVE responses of birds to increasing and decreasing photoperiods has been the subject of many studies. However, few reports have dealt with reproductive responses to increasing photoperiod changes at various ages. Change in length of the photoperiod had a greater effect on rate of sexual development and egg production than a constant photoperiod (Morris and Fox, 1958; King, 1958; Lert et al., 1960). Increasing light during the rearing period resulted in early sexual maturity, whereas, decreasing day-lengths retarded sexual development (King, 1961; Shutze et al., 1961; Shutze et ah, 1961, 1963; Lowe and 1 Scientific Paper No. 3199, College of Agriculture, Washington State University, Pullman. Project 1444.
Heywang, 1964). Pullets reared on decreasing or short day-lengths, then subjected to increasing day-lengths, responded to the light stimulus with increased production and increased egg size (Morris and Fox, 1958; Shutze et al., 1963; Lowe and Heywang, 1964). Preconditioning of pullets by a reduction in photoperiod initiated prior to 14 weeks of age, resulted in increased egg production when exposed to increased hours of light during the laying period (Biellier, 1960; Harrison et al., 1962). The amount of light required to stimulate early sexual development, following exposure to 6 hours of daily light, is reported to be between 10 and 14 hours of light per day (Harrison et al., 1965). The experiment reported here was de-
1022
P . C. H A R R I S O N , G. SCHUMAIER AND J. M C G I N N I S
TABLE 1.—Average age at first egg (days) Age at initial increase in photoperiod (weeks) 14 16 18 20 Mean
Photoperiod change 6->14
6->12
6->8
163 163 173 178 169
161 167 174 177 170
190 186 196 189 190
171 180 181 181
signed to further investigate the hours of increase in photoperiod required to stimulate reproductive activity. Also of special interest was the relationship between amount of increase in light and the age at which the increase was given. METHODS OF PROCEDURE White Leghorn pullets were floor-brooded and reared on a daily photoperiod of 6 hours of light and 18 hours of dark (6 L / 1 8 D) from one d a y of age until placed in individual laying cages. One hundred twenty pullets were randomly placed in each of three different laying period light treatments at 14, 16, 18 and 20 weeks of age. Laying period light t r e a t m e n t s were: (1) 14 L / 1 0 D ; (2) 12 L / 1 2 D to 20 weeks of age, then an increase in light period b y 15 minutes per week to 14 L / 1 0 D ; (3) 8 L / 1 6 D to 20 weeks of age, then an increase in light period of 15 minutes per week to 14 L / 1 0 D . Egg weights were taken at four-week intervals from eggs collected on three consecutive days. Egg yields (grams of egg/ bird/day) were calculated as described b y Bray (1964). Feed consumption for the three light t r e a t m e n t s and mortality in both age and light treatments were recorded throughout the experiment, beginning at 19 weeks of age. RESULTS AND DISCUSSION Sexual development was definitely affected b y both amount of increase in pho-
toperiod and age when the photoperiod was increased (Table 1). There was no difference in sexual development of pullets increased to 12 L / 1 2 D and 14 L / 1 0 D . However, those increased to 8 L / 1 6 D showed an increased average age at first egg. Average age at first egg was about 20 days earlier in the 12 L / 1 2 D and 14 L / 1 0 D t r e a t m e n t s as compared with the 8 L / 1 6 D treatment. Harrison et al. (1965) reported an increase from 6 hours of light to 14 hours of daily photoperiod at 16 weeks stimulated pullets to 50 percent hen-day production 3 weeks before pullets subjected to 10 hours of light at this same age. These d a t a further bracket the hours of light needed to stimulate reproductive response at 16 weeks to be between 10 and 12 hours of light per day. Age at which the birds were transferred to the 12 L / 1 2 D and 14 L / 1 0 D treatments affected age at sexual m a t u r i t y . T h e older the birds when placed on the 12 L / 1 2 D and 14 L / 1 0 D , the greater the age a t first egg. Readiness of the pullets to respond to increasing hours of light at 20 weeks is shown b y the age at first egg. Those transferred to 14 L / 1 0 D and 12 L / 1 2 D at 20 weeks showed an average age at first egg only 5 and 3 days later than those transferred at 18 weeks of age. In the 6 L / 1 8 D to 8 L / 1 6 D t r e a t m e n t the age a t which the 2-hour increase was given did not influence age at first egg. The light t r e a t m e n t and the age at TABLE 2.—Percent hen-day egg production between 19 and 62 weeks of age Age at initial increase in photoperiod (weeks) 14 16 18 20 Mean
Photoperiod change 6->14
6->12
6->8
62 64 65 70 65
64 67 60 67 65
63 69 62 67 65
1023
D A Y L E N G T H AND REPRODUCTION 90 80
I"o 7° I 60 en 50 o> U >» 40 a Q 30
Laying Period Light Treatments I4L/I0D I2L/I2D + I5min/wk 8L/I6D + I5min/wk
20
I
10
i 20
24
28
32
36 40 44 Age (Weeks)
48
52
56
60
FIG. 1. Egg production pattern of White Leghorn pullets subjected to different rates of increase in photoperiod. treatment had no real effect on total egg production through 62 weeks of age (Table 2). A trend toward lower egg production was indicated for the birds exposed to the 14 L / 1 0 D t r e a t m e n t at 14 weeks of age. Even though total egg production was not altered, the p a t t e r n of production was different (Fig. 1). Birds on the 14 L / 1 0 D and 12 L/12 D treatments attained peak egg production earliest. Those on the 8 L / 1 6 D t r e a t m e n t showed a higher peak in production and maintained a higher production rate over a longer period of time. These results indicate t h a t the weekly 15-minute increases in daily photoperiod were effective in stimulating reproductive processes in the 8 L / 1 6 D treatment, b u t not in the 12 L / 1 2 D treatment. However, in both treatments the rate of egg production was decreasing before the weekly increases in light had attained 14 hours of light. These d a t a indicate t h a t even though the 15-minute per week in-
creases in daily photoperiod were effective in stimulating reproductive processes, the birds m a y become refractory to this light stimulus. T h e lower total egg production in the birds transferred to 8 L / 1 6 D at 14 and 18 weeks of age was due to a shorter maximum production period followed b y a more rapid decrease in egg production during the last 2-3 months of the experiment. Those transferred to 12 L / 1 2 D at 18 weeks showed a lower rate of production throughout the experiment. T h e age a t which light t r e a t m e n t started had an effect on length of maximum egg production (weeks over 80 percent) when the birds were placed on 14 L / 1 0 D (Table 3). T h e same trend was indicated in the 12 L / 1 2 D treatment, with the exception of the pullets transferred at 18 weeks of age. I n these two treatments, the older the birds when subjected to the initial increase in day-length, the longer the period of hen-day egg production over 80 per-
1024
P. C. HARRISON, G. SCHUMAIER AND J. MCGINNIS
TABLE 3.—Weeks of ken-day egg production over 80% Age at initial increase in photoperiod (weeks)
6^14
6^12
6-^8
14 16 18 20
2 4 12 16
6 10 2 14
12 20 14 18
Photoperiod change
cent. In the 8 L/16 D treatment, all age treatments maintained over an 80 percent hen-day egg production between 12 and 20 weeks. However, there was no correlation between the length of the maximum production period and the age at which the pullets received the initial 2hour increase in daily photoperiod. Even though sexual maturity was delayed by about 3 weeks in the 8 L/16 D treatment, the persistency of a high maximum production enabled these birds to equal the total egg production of the earlier maturing treatment. Light treatment and age at exposure to different light treatments affected egg size. In the 12 L/12 D and 14 L/10 D treatments, the younger the pullets were, when exposed to the initial 6 and 8 hour increase in daily photoperiod, the smaller the egg size (Table 4). Also, the younger the pullet was, at sexual maturity, the smaller the egg size. This decreased egg weight was not only due to smaller eggs during the initial egg production phase, but the production of smaller eggs through the entire laying period (Fig. 2). In the 8 L/16 D treatment, that increased by 15 minutes per week, the age when the birds were exposed to the 2-hour increase in daily photoperiod had no influence on egg size. The birds in all of the groups within this treatment matured later and had greater egg size than any of the other groups within the other treatments. Feed consumption was directly related to egg production. The pullets in the 8
L/16 D treatment consumed less feed during the early part of the egg production period and more during the latter portion. The maximum mean difference in feed consumed per bird per day between treatments was 4.8 grams for the entire laying period. Mortality rate was greatest in the birds transferred to the laying house light treatments at 14 weeks of age (Table 5). Mortality was greatest in the birds transferred to 14 L/10 D at 14 weeks of age. Mortality rate appeared to be related to the age at transfer rather than to the length of photoperiod into which they were moved, since the second highest mortality was in the 8 L/16 D treatment transferred at 14 weeks of age. Mean mortality rate in the 14-week treatment was twice that of any of the other age groups. However, there was no difference in mean mortality between photoperiod treatments. The efficiency of production of the birds subjected to the different rates of increase in light is shown in Table 6. There was no difference in the eggs produced per hen housed, in egg mass yield, nor feed efficiency (grams feed/gram egg). The birds receiving the initial two hour increase, followed by 15-minute per week increase in photoperiod, showed the poorest feed efficiency. However, this is due to the late sexual maturity. Since these birds were in a higher rate of egg production at the end TABLE 4.—Mean egg weight (gms.) between 19 and 62 weeks of age Age at initial increase in photoperiod (weeks) 14 16 18 20 Mean
Photoperiod change 6-^14
6->12
6^8
52.50 53.94 54.28 54.85 53.89
53.05 54.25 54.24 55.44 54.25
55.47 55.92 56.09 55.61 55.77
i025
DAY LENGTH AND REPRODUCTION
38
42
Age (Weeks) FIG. 2. Egg weights of White Leghorn pullets subjected to an 8-hour increase in photoperiod at different ages.
of the experiment (Figure 1), the feed efficiency should increase as the length of the laying period increased. SUMMARY White Leghorn pullets reared on 6 hours of daily light were subjected to 3 different laving period light treatments at 14, 16, 18 and 20 weeks of age. Laying period light treatments were: (1) 14 L/10 D; (2) 12 L/12 D to 20 weeks, then increased 15 minutes per week to 14 L/10 D; TABLE 5.—Percent mortality between 19 and 62 weeks of age Hours of light
14 12 8 .ean
(3) 8 L/16 D to 20 weeks, then increased 15 minutes per week to 14 L/10 D. The younger the age at transfer to 14 L/10 D and 12 L/12 D treatments, the younger the average age at first egg. Age at transfer to the 8 L/16 D treatment did not affect sexual development, and average age at first egg was around 20 days greater than the other two treatments. Birds transferred to 14 and 12 hours of daily light at 20 weeks of age maintained peak production over a longer period of TABLE 6.—Efficiency of production between 19 and 62 weeks of age for White Leghorn pullets exposed to different rates of increase in photoperiod
Age at light treatment (wks.) 14
16
18
20
X
9.2 5.8 8.3 7.8
0.8 4.2 1.7 2.2
5.0 4.2 1.7 3.6
2.5 2.5 4.2 3.1
4.4 4.2 4.0 4.2
Light Eggs/hen Grams Grams treatment housed egg/hen/day feed/gram egg 6->14 6->12 6-^8
194.96 194.48 192.83
36.02 + 1.63 35.81 + 1.61 35.98 + 2.62
2.578 2.691 2.713
1026
P. C. HARRISON, G. SCHTJMAIER AND J. MCGINNIS
time than those transferred earlier. Peak production was maintained longer in the 8 L/16 D treatment than in the other two treatments. However, rate of egg production was decreasing before the increases of 15 minutes per week had attained a photoperiod of 14 L/10 D. Even though egg production pattern was altered, total egg production was not affected by light treatment. Egg weight was affected by age at exposure to the 14 L/10 D and 12 L/12 D treatments. Egg weights were less throughout the entire laying period in early maturing birds. REFERENCES Biellier, H. V., 1960. The effect of age of restricting light during the adolescent period on reproductive performance of chickens subjected to various day-lengths. Poultry Sci. 39: 1235. Bray, D. J., 1964. Studies with corn-soya laying diets. Poultry Sci. 43: 396-401. Harrison, P. C , H. V. Biellier and E. M. Funk, 1962. Effect of light restriction during growing period on reproductive performance of chickens sub-
jected to various light regimes. Poultry Sci. 41: 1648-1649. Harrison, P. C , H. V. Biellier and E. M. Funk, 1965. Effect of rate of decrease and increase in photoperiod on sexual maturity of S.C. White Leghorn pullets. Poultry Sci. 44: 1377. King, D. F., 1958. A brand new way to light your layers. Farm J. February, p. 36-37. King, D. F., 1961. Effects of increasing, decreasing and constant light treatments on growing pullets. Poultry Sci. 40: 479-484. Lert, P. J., W. O. Wilson and S. A. Hart, 1960. Effect of restricted lighting of pullets on subsequent egg production. Poultry Sci. 39: 1270. Lowe, R. W., and B. W. Heywang, 1964. Effect of various light treatments during growing period on egg production of October hatched White Leghorn pullets. Poultry Sci. 43: 11-15. Morris, T. R., and S. Fox, 1958. Artificial light and sexual maturity in the fowl. Nature, 182: 1522— 1523. Shutze, J. V., W. E. Matson and J. McGinnis, 1961. Influence of different photoperiods during brooding and rearing on subsequent productive characteristics in chickens. Poultry Sci. 40: 16041611. Shutze, J. V., W. E. Matson and J. McGinnis, 1963 Effect of light on economic and physiological characters of laying hens. Poultry Sci. 42: 150156.
NEWS AND NOTES {continued from page 993) CONGRESS PAPERS The Spanish Commission responsible for staging the World Poultry Congress in Madrid on September 6-12, 1970, has announced the final details concerning submission of papers and panel summaries. Summaries of papers are not to exceed 500 words. The final texts of original manuscripts are not to exceed 2,500 words. The Congress will present a number of two and one-half hour panels. Summaries of panel presentations are not to exceed 5,000 words. The original announcement indicated that Americans would have to submit abstracts in English and Spanish and that papers would be submitted in English only. Final instructions by the Congress Commission indicates that English, French, German and Spanish are the official languages and the only stipulation is that papers will be submitted in one of the four languages.
Questions re submission should be referred to Dr. R. N. Shoffner, Animal Science Department, University of Minnesota, St. Paul, Minnesota 55101. DIAMOND NOTES Diamond Automation, Inc., Farmington, Michigan, has combined the marketing of Page automated egg processing systems and Keenco automated cage systems under the new name Diamond Systems. WHITMOYER NOTES William P. Ambrogi has been appointed President of Whitmoyer Laboratories, Inc., Myerstown, Pennsylvania, a subsidiary of Rohm and Haas Company, Philadelphia. He succeeds Glenn Trout. Frederick W. Robinson has been appointed Director of Manufacturing. He will be responsible for overall coordination and director of production, engineering and development, and plant safety.
(continued on page 1033)
p.p.m. during the first week, as these birds gained 14.3% less (P = 0.01) than controls. Interestingly enough, growth in the birds at this level gradually improved, so that during the last week of the trial they grew only 4% less than control birds. The results of these experiments indicate that the tolerance of chickens for ethopabate is approximately 100 p.p.m. when it is administered in a growing ration containing 100 p.p.m. of amproHum. SUMMARY
The tolerance of growing chickens for
1021
ethopabate when given in a ration containing 100 p.p.m. of amprolium was studied in two experiments using a total of 700 broiler chicks. Measured in terms of growth, 80 to 100 p.p.m. of ethopabate were tolerated without significant effects. At these levels, a slight and transient depression of growth was seen in the second week of the experiment, indicating that these doses must be taken as a tolerance limit. When the drug concentration was raised to 200 p.p.m. or more, marked depression in early growth was produced. No appreciable negative influences on feed consumption were observed.
Reproductive Development and Response of White Leghorn Pullets Subjected to Increasing Day-Lengths at Different Ages1 P. C. HARRISON, G. SCHUMAIER AND J. MCGINNIS Department of Animal Sciences, Washington State University, Pullman, Washington 99163 (Received for publication November 28, 1968)
R
EPRODUCTIVE responses of birds to increasing and decreasing photoperiods has been the subject of many studies. However, few reports have dealt with reproductive responses to increasing photoperiod changes at various ages. Change in length of the photoperiod had a greater effect on rate of sexual development and egg production than a constant photoperiod (Morris and Fox, 1958; King, 1958; Lert et al., 1960). Increasing light during the rearing period resulted in early sexual maturity, whereas, decreasing day-lengths retarded sexual development (King, 1961; Shutze et al., 1961; Shutze et ah, 1961, 1963; Lowe and 1 Scientific Paper No. 3199, College of Agriculture, Washington State University, Pullman. Project 1444.
Heywang, 1964). Pullets reared on decreasing or short day-lengths, then subjected to increasing day-lengths, responded to the light stimulus with increased production and increased egg size (Morris and Fox, 1958; Shutze et al., 1963; Lowe and Heywang, 1964). Preconditioning of pullets by a reduction in photoperiod initiated prior to 14 weeks of age, resulted in increased egg production when exposed to increased hours of light during the laying period (Biellier, 1960; Harrison et al., 1962). The amount of light required to stimulate early sexual development, following exposure to 6 hours of daily light, is reported to be between 10 and 14 hours of light per day (Harrison et al., 1965). The experiment reported here was de-
1022
P . C. H A R R I S O N , G. SCHUMAIER AND J. M C G I N N I S
TABLE 1.—Average age at first egg (days) Age at initial increase in photoperiod (weeks) 14 16 18 20 Mean
Photoperiod change 6->14
6->12
6->8
163 163 173 178 169
161 167 174 177 170
190 186 196 189 190
171 180 181 181
signed to further investigate the hours of increase in photoperiod required to stimulate reproductive activity. Also of special interest was the relationship between amount of increase in light and the age at which the increase was given. METHODS OF PROCEDURE White Leghorn pullets were floor-brooded and reared on a daily photoperiod of 6 hours of light and 18 hours of dark (6 L / 1 8 D) from one d a y of age until placed in individual laying cages. One hundred twenty pullets were randomly placed in each of three different laying period light treatments at 14, 16, 18 and 20 weeks of age. Laying period light t r e a t m e n t s were: (1) 14 L / 1 0 D ; (2) 12 L / 1 2 D to 20 weeks of age, then an increase in light period b y 15 minutes per week to 14 L / 1 0 D ; (3) 8 L / 1 6 D to 20 weeks of age, then an increase in light period of 15 minutes per week to 14 L / 1 0 D . Egg weights were taken at four-week intervals from eggs collected on three consecutive days. Egg yields (grams of egg/ bird/day) were calculated as described b y Bray (1964). Feed consumption for the three light t r e a t m e n t s and mortality in both age and light treatments were recorded throughout the experiment, beginning at 19 weeks of age. RESULTS AND DISCUSSION Sexual development was definitely affected b y both amount of increase in pho-
toperiod and age when the photoperiod was increased (Table 1). There was no difference in sexual development of pullets increased to 12 L / 1 2 D and 14 L / 1 0 D . However, those increased to 8 L / 1 6 D showed an increased average age at first egg. Average age at first egg was about 20 days earlier in the 12 L / 1 2 D and 14 L / 1 0 D t r e a t m e n t s as compared with the 8 L / 1 6 D treatment. Harrison et al. (1965) reported an increase from 6 hours of light to 14 hours of daily photoperiod at 16 weeks stimulated pullets to 50 percent hen-day production 3 weeks before pullets subjected to 10 hours of light at this same age. These d a t a further bracket the hours of light needed to stimulate reproductive response at 16 weeks to be between 10 and 12 hours of light per day. Age at which the birds were transferred to the 12 L / 1 2 D and 14 L / 1 0 D treatments affected age at sexual m a t u r i t y . T h e older the birds when placed on the 12 L / 1 2 D and 14 L / 1 0 D , the greater the age a t first egg. Readiness of the pullets to respond to increasing hours of light at 20 weeks is shown b y the age at first egg. Those transferred to 14 L / 1 0 D and 12 L / 1 2 D at 20 weeks showed an average age at first egg only 5 and 3 days later than those transferred at 18 weeks of age. In the 6 L / 1 8 D to 8 L / 1 6 D t r e a t m e n t the age a t which the 2-hour increase was given did not influence age at first egg. The light t r e a t m e n t and the age at TABLE 2.—Percent hen-day egg production between 19 and 62 weeks of age Age at initial increase in photoperiod (weeks) 14 16 18 20 Mean
Photoperiod change 6->14
6->12
6->8
62 64 65 70 65
64 67 60 67 65
63 69 62 67 65
1023
D A Y L E N G T H AND REPRODUCTION 90 80
I"o 7° I 60 en 50 o> U >» 40 a Q 30
Laying Period Light Treatments I4L/I0D I2L/I2D + I5min/wk 8L/I6D + I5min/wk
20
I
10
i 20
24
28
32
36 40 44 Age (Weeks)
48
52
56
60
FIG. 1. Egg production pattern of White Leghorn pullets subjected to different rates of increase in photoperiod. treatment had no real effect on total egg production through 62 weeks of age (Table 2). A trend toward lower egg production was indicated for the birds exposed to the 14 L / 1 0 D t r e a t m e n t at 14 weeks of age. Even though total egg production was not altered, the p a t t e r n of production was different (Fig. 1). Birds on the 14 L / 1 0 D and 12 L/12 D treatments attained peak egg production earliest. Those on the 8 L / 1 6 D t r e a t m e n t showed a higher peak in production and maintained a higher production rate over a longer period of time. These results indicate t h a t the weekly 15-minute increases in daily photoperiod were effective in stimulating reproductive processes in the 8 L / 1 6 D treatment, b u t not in the 12 L / 1 2 D treatment. However, in both treatments the rate of egg production was decreasing before the weekly increases in light had attained 14 hours of light. These d a t a indicate t h a t even though the 15-minute per week in-
creases in daily photoperiod were effective in stimulating reproductive processes, the birds m a y become refractory to this light stimulus. T h e lower total egg production in the birds transferred to 8 L / 1 6 D at 14 and 18 weeks of age was due to a shorter maximum production period followed b y a more rapid decrease in egg production during the last 2-3 months of the experiment. Those transferred to 12 L / 1 2 D at 18 weeks showed a lower rate of production throughout the experiment. T h e age a t which light t r e a t m e n t started had an effect on length of maximum egg production (weeks over 80 percent) when the birds were placed on 14 L / 1 0 D (Table 3). T h e same trend was indicated in the 12 L / 1 2 D treatment, with the exception of the pullets transferred at 18 weeks of age. I n these two treatments, the older the birds when subjected to the initial increase in day-length, the longer the period of hen-day egg production over 80 per-
1024
P. C. HARRISON, G. SCHUMAIER AND J. MCGINNIS
TABLE 3.—Weeks of ken-day egg production over 80% Age at initial increase in photoperiod (weeks)
6^14
6^12
6-^8
14 16 18 20
2 4 12 16
6 10 2 14
12 20 14 18
Photoperiod change
cent. In the 8 L/16 D treatment, all age treatments maintained over an 80 percent hen-day egg production between 12 and 20 weeks. However, there was no correlation between the length of the maximum production period and the age at which the pullets received the initial 2hour increase in daily photoperiod. Even though sexual maturity was delayed by about 3 weeks in the 8 L/16 D treatment, the persistency of a high maximum production enabled these birds to equal the total egg production of the earlier maturing treatment. Light treatment and age at exposure to different light treatments affected egg size. In the 12 L/12 D and 14 L/10 D treatments, the younger the pullets were, when exposed to the initial 6 and 8 hour increase in daily photoperiod, the smaller the egg size (Table 4). Also, the younger the pullet was, at sexual maturity, the smaller the egg size. This decreased egg weight was not only due to smaller eggs during the initial egg production phase, but the production of smaller eggs through the entire laying period (Fig. 2). In the 8 L/16 D treatment, that increased by 15 minutes per week, the age when the birds were exposed to the 2-hour increase in daily photoperiod had no influence on egg size. The birds in all of the groups within this treatment matured later and had greater egg size than any of the other groups within the other treatments. Feed consumption was directly related to egg production. The pullets in the 8
L/16 D treatment consumed less feed during the early part of the egg production period and more during the latter portion. The maximum mean difference in feed consumed per bird per day between treatments was 4.8 grams for the entire laying period. Mortality rate was greatest in the birds transferred to the laying house light treatments at 14 weeks of age (Table 5). Mortality was greatest in the birds transferred to 14 L/10 D at 14 weeks of age. Mortality rate appeared to be related to the age at transfer rather than to the length of photoperiod into which they were moved, since the second highest mortality was in the 8 L/16 D treatment transferred at 14 weeks of age. Mean mortality rate in the 14-week treatment was twice that of any of the other age groups. However, there was no difference in mean mortality between photoperiod treatments. The efficiency of production of the birds subjected to the different rates of increase in light is shown in Table 6. There was no difference in the eggs produced per hen housed, in egg mass yield, nor feed efficiency (grams feed/gram egg). The birds receiving the initial two hour increase, followed by 15-minute per week increase in photoperiod, showed the poorest feed efficiency. However, this is due to the late sexual maturity. Since these birds were in a higher rate of egg production at the end TABLE 4.—Mean egg weight (gms.) between 19 and 62 weeks of age Age at initial increase in photoperiod (weeks) 14 16 18 20 Mean
Photoperiod change 6-^14
6->12
6^8
52.50 53.94 54.28 54.85 53.89
53.05 54.25 54.24 55.44 54.25
55.47 55.92 56.09 55.61 55.77
i025
DAY LENGTH AND REPRODUCTION
38
42
Age (Weeks) FIG. 2. Egg weights of White Leghorn pullets subjected to an 8-hour increase in photoperiod at different ages.
of the experiment (Figure 1), the feed efficiency should increase as the length of the laying period increased. SUMMARY White Leghorn pullets reared on 6 hours of daily light were subjected to 3 different laving period light treatments at 14, 16, 18 and 20 weeks of age. Laying period light treatments were: (1) 14 L/10 D; (2) 12 L/12 D to 20 weeks, then increased 15 minutes per week to 14 L/10 D; TABLE 5.—Percent mortality between 19 and 62 weeks of age Hours of light
14 12 8 .ean
(3) 8 L/16 D to 20 weeks, then increased 15 minutes per week to 14 L/10 D. The younger the age at transfer to 14 L/10 D and 12 L/12 D treatments, the younger the average age at first egg. Age at transfer to the 8 L/16 D treatment did not affect sexual development, and average age at first egg was around 20 days greater than the other two treatments. Birds transferred to 14 and 12 hours of daily light at 20 weeks of age maintained peak production over a longer period of TABLE 6.—Efficiency of production between 19 and 62 weeks of age for White Leghorn pullets exposed to different rates of increase in photoperiod
Age at light treatment (wks.) 14
16
18
20
X
9.2 5.8 8.3 7.8
0.8 4.2 1.7 2.2
5.0 4.2 1.7 3.6
2.5 2.5 4.2 3.1
4.4 4.2 4.0 4.2
Light Eggs/hen Grams Grams treatment housed egg/hen/day feed/gram egg 6->14 6->12 6-^8
194.96 194.48 192.83
36.02 + 1.63 35.81 + 1.61 35.98 + 2.62
2.578 2.691 2.713
1026
P. C. HARRISON, G. SCHTJMAIER AND J. MCGINNIS
time than those transferred earlier. Peak production was maintained longer in the 8 L/16 D treatment than in the other two treatments. However, rate of egg production was decreasing before the increases of 15 minutes per week had attained a photoperiod of 14 L/10 D. Even though egg production pattern was altered, total egg production was not affected by light treatment. Egg weight was affected by age at exposure to the 14 L/10 D and 12 L/12 D treatments. Egg weights were less throughout the entire laying period in early maturing birds. REFERENCES Biellier, H. V., 1960. The effect of age of restricting light during the adolescent period on reproductive performance of chickens subjected to various day-lengths. Poultry Sci. 39: 1235. Bray, D. J., 1964. Studies with corn-soya laying diets. Poultry Sci. 43: 396-401. Harrison, P. C , H. V. Biellier and E. M. Funk, 1962. Effect of light restriction during growing period on reproductive performance of chickens sub-
jected to various light regimes. Poultry Sci. 41: 1648-1649. Harrison, P. C , H. V. Biellier and E. M. Funk, 1965. Effect of rate of decrease and increase in photoperiod on sexual maturity of S.C. White Leghorn pullets. Poultry Sci. 44: 1377. King, D. F., 1958. A brand new way to light your layers. Farm J. February, p. 36-37. King, D. F., 1961. Effects of increasing, decreasing and constant light treatments on growing pullets. Poultry Sci. 40: 479-484. Lert, P. J., W. O. Wilson and S. A. Hart, 1960. Effect of restricted lighting of pullets on subsequent egg production. Poultry Sci. 39: 1270. Lowe, R. W., and B. W. Heywang, 1964. Effect of various light treatments during growing period on egg production of October hatched White Leghorn pullets. Poultry Sci. 43: 11-15. Morris, T. R., and S. Fox, 1958. Artificial light and sexual maturity in the fowl. Nature, 182: 1522— 1523. Shutze, J. V., W. E. Matson and J. McGinnis, 1961. Influence of different photoperiods during brooding and rearing on subsequent productive characteristics in chickens. Poultry Sci. 40: 16041611. Shutze, J. V., W. E. Matson and J. McGinnis, 1963 Effect of light on economic and physiological characters of laying hens. Poultry Sci. 42: 150156.
NEWS AND NOTES {continued from page 993) CONGRESS PAPERS The Spanish Commission responsible for staging the World Poultry Congress in Madrid on September 6-12, 1970, has announced the final details concerning submission of papers and panel summaries. Summaries of papers are not to exceed 500 words. The final texts of original manuscripts are not to exceed 2,500 words. The Congress will present a number of two and one-half hour panels. Summaries of panel presentations are not to exceed 5,000 words. The original announcement indicated that Americans would have to submit abstracts in English and Spanish and that papers would be submitted in English only. Final instructions by the Congress Commission indicates that English, French, German and Spanish are the official languages and the only stipulation is that papers will be submitted in one of the four languages.
Questions re submission should be referred to Dr. R. N. Shoffner, Animal Science Department, University of Minnesota, St. Paul, Minnesota 55101. DIAMOND NOTES Diamond Automation, Inc., Farmington, Michigan, has combined the marketing of Page automated egg processing systems and Keenco automated cage systems under the new name Diamond Systems. WHITMOYER NOTES William P. Ambrogi has been appointed President of Whitmoyer Laboratories, Inc., Myerstown, Pennsylvania, a subsidiary of Rohm and Haas Company, Philadelphia. He succeeds Glenn Trout. Frederick W. Robinson has been appointed Director of Manufacturing. He will be responsible for overall coordination and director of production, engineering and development, and plant safety.
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