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A Study of Certain Environmental Factors on the Reproductive Performance of Large White Turkeys1
A Study of Certain Environmental Factors on the Reproductive Performance of Large White Turkeys 1 D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON, JR. Department of Poultry Science and Department of Agricultural Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (Received for publication December 14, 1971)
ABSTRACT The study presented was designed to determine the effects of light intensities of 5.4 and 86.1 lux, of laying cages versus conventional litter floors and of constant environmental temperatures of 12.8°, 21.1° and 2°.4°C. on the reproductive performance of Large White female turkeys. A light intensity of 5.4 lux yielded comparable results to that of 86.1 lux when 16 hours of light were provided. Turkey females in laying cages laid at a higher rate over the first 12 weeks of production and showed an increase in feed consumption and body weight over those maintained in conventional litter pens. No significant differences were observed between the two pen environments for total egg production, hatchability of fertile eggs and egg weights. Percentage settable eggs and percentage fertility were lower from females maintained in cages. The percentage of cracked and broken, and soft- and thin-shelled eggs from cage birds increased over the production period. A constant pen temperature of 29.4° C. dramatically reduced egg production below that obtained from females maintained at 12.8° and 21.1 °C. The high pen temperature also reduced feed consumption, body weights, egg weights, the effectiveness of broodiness control and increased the incidence of birds molting and mortality. Fertility, hatchability, percentage settable eggs and shell thickness were unaffected by the imposed temperature environments. Pen temperatures of 12.8° and 21.°C. yielded comparable results for all reproductive parameters studied. It is concluded that reproductive potential of turkeys in the present study was maximized on conventional litter floors with constant temperatures between 12.8° and 21.1°C. and light intensities between S.4 and 86.1 lux. POULTRY SCIENCE 51: 1438-1449,
I
T has become apparent, with the trend toward complete confinement of turkey breeder hens, that very little is known about the environmental factors that infiuence reproductive functions of turkeys under housed conditions. It is important, therefore, that research be developed that will allow experimental control of certain environmental factors in order to evaluate the relative contributions each makes toward the expression of maximum reproductive potential. The stimulatory effect of artificial illumination on egg production in turkeys was demonstrated by Albright and Thompson (1933) and Marsden (1936). Asmundson 7~. ; " ~ ~ \ 7~
1972
et al. (1946) found that a minimum light intensity of 21.5 lux was needed to induce the most rapid response in egg production and that this level of light intensity increased total egg production over that obtained with 1.1, 3.2 or 10.8 lux. Garland et al. (1961) reported similar results. The latter also reported that increasing the light intensity from 21.S to 366.0 lux by gradual increments at four week intervals resulted in higher total egg production. The egg production industry has accepted the use of laying cages for chickens. The turkey industry, consequently, has been pondering the applicability of cages for turkey reproduction. Woodard et al. (1961) showed that Broad Breasted
A portion of a thesis prepared by the senior .1 ' . B r o n z e females ke author in partial fulfillment of the requirements Pt ln ca8es lald m o r e for the degree of Master of Science. eggs than did floor birds, but they also laid 1438
ENVIRONMENT AND TURKEY REPRODUCTIVE PERFORMANCE
many more soft-shelled eggs. Similar problems with egg shell quality were found by Wolford and Zindel (1970). Preliminary studies at this station utilizing Medium White turkeys showed no differences in egg production, egg weights, hatchability of fertile eggs, feed consumed per bird and the amount of feed consumed per egg produced between birds maintained in cages and those on conventional litter floors. Fertility, however, appeared to be somewhat lower in birds maintained in cages. While studies concerning the effects of ambient temperature on the reproductive performance of chickens are voluminous, little has been reported with reference to turkeys. Initial information by Parkerj (1947) and later by Shoffner et al. (1962) suggests that egg production decreases as seasonal temperatures increase during the breeding season. Mitchell and Kosin (19S4) and Kosin and Mitchell (1955a) found that pre-heating hens before they commenced egg production resulted in higher initial egg production levels. Total egg production was unaffected by pre-heating treatments. They also reported that maintaining hens at 10°C. during the breeding season was detrimental to egg production due to increased broodiness. Marsden et al. (1966) noted that an ambient temperature of 18.3°C. provided a stimulatory effect on egg production of birds under an 11-hour photoperiod. The effect, however, was considerably less under 13- and 15-hour photoperiods. Parker (1947) found that egg weights; increased from January to June. Mitchell and Kosin (1954) observed that egg weights were lower in constant 18.3°C. pens than in uncontrolled temperature pens. In his report, Parker (1947) found fertility to be high until May and June, followed by a gradual decline thereafter. Hatchability of fertile eggs increased to
1439
late February (point of highest production) followed by a decline as the breeding season progressed. Pre-conditioning of males by supplemental heat when they were in a cold environment was reported by Kosin et al. (1952) and Kosin and Mitchell (1955a) to be advantageous for fertility under natural mating conditions. Kosin and Mitchell (1955b) also reported that the cooling of Broad Breasted Bronze males in the months of May, June and July, at least temporarily, halted the seasonal downward trend in fertility. Marsden et al. (1966), on the other hand, found that fertility and hatchability under their experimental conditions were unaffected by temperature and light. The incidence of broodiness in turkey populations is a major consideration in the production of turkey hatching eggs. The deleterious effects of broodiness on egg production and on subsequent poult production has been well documented by Parker and Barton (1945), Jones and Kohlmeyer (1947), Smyth and Leighton (1953) and McCartney (1956). In comparing constant environmental temperatures with uncontrolled ones, Mitchell and Kosin (1954) and Kosin and Mitchell (1955a) found that broodiness increased in constant temperature pens, resulting in lower egg production. Marsden et al. (1966) also observed an increasing incidence of broodiness during the summer months. The objectives of this study were: (1) to determine the effect of environmental temperature and light intensity on reproductive performance; (2) to evaluate the relative merits of conventional litter pens versus laying cages on egg production, fertility, hatchability, broodiness, egg weight and egg shell quality; and (3) ascertain the optimum combination of temperature, light intensity and floor pen environment for maximum expression of reproductive potential.
1440
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR.
was 0.64 cm. wide and spaced 0.64 cm. apart. The light intensity of 5.4 lux was proPen Light Pen Number vided in half of the pens by two 7.5-watt environment in%nfy temperature of (lux) (°C.) females bulbs in each pen. A light intensity of 86.1 ; S.4 12.8 120 lux was provided in the remaining half of 21.1 ' > .20 the pens by two 60-watt bulbs in each of 29.4 ;*W['M Floor these pens. 86.1 12.8 20 Pen temperatures were maintained at the 21.1 20 29.4 20 designated temperatures ± 2.8°C. through the use of thermostatically controlled (Day5.4 12.8 20 21.1 20 ton temperature control thermostats, models 29.4 20 21E 206 and 21E 207) heaters and air Cage 86.1 12.8 20 conditioners. 21.1 20 Duplicate pens of ten females each were 29.4 20 placed in each treatment combination. The observational unit for this experiment consisted of ten females within each pen enviMATERIALS AND METHODS ronment, light intensity and pen temperaTwo hundred forty Large White turkey ture subclass. For a two-day period at the beginning of females and 60 males of the same age and strain were restricted at 24 weeks of age to this experiment, light intensity was mainsix hours of light per day. On February 28, tained in all pens at 86.1 lux to insure that 1969, the 3 4-week-old males were exposed the birds would find feed and water. The to stimulatory light levels of 16 hours of V.P.I. & S.U. turkey breeder diet (Table natural plus artificial light per day at a 2) and water were provided ad libitum to minimum light intensity of 86.1 lux. On all birds. Feed records were kept on an inMarch 21, 1969, after being under re- dividual bird basis for the cage birds and stricted lighting for 13 weeks, 120 females on a pen basis for the floor pens. Feed was were randomly assigned to laying cages and weighed back every 28 days beginning with another 120 were placed in conventional lit- March 21. Body weight and molt condition ter floor pens. Females within each pen en- were also recorded at that time. Egg weights were obtained on April 28 vironment were exposed to two light intensities and three temperature treatments in a (Period 1), June 23 (Period 2) and August factorial arrangement (Table 1). Sixteen 18, 1969 (Period 3). Egg shell thickness hours of continuous artificial illumination measurements were determined from threeper day were provided throughout the ex- day samples of eggs beginning on May 13, July 22 and September 7, 1969. Shell thickperimental period. Pen environments used were conven- ness of each egg represented the average of tional wood-shaving floors and single bird, a measurement taken from each end and double-decked laying cages. One birds was from the middle of each egg by cracking place in each of five cages on the top and the egg and peeling off a piece of shell. The bottom deck. An individual cage measured instrument used to measure these shells 43.2 cm. wide, 61.0 cm. long and 64.8 cm. was an Ames Thickness Measurer Model high. The floor of each cage was 16 gauge, 2SE, having a curved anvil, and allowing plastic coated, flat metal strapping which an approximation to the nearest 0.0001 of TABLE 1.—Experimental design and the number offemales used
ENVIRONMENT AND TURKEY REPRODUCTIVE PERFORMANCE
an inch which was converted to millimeters. Broody birds from the floor pens were treated for five days following detection by placing them in a broody coop equipped with a wire floor. Cage birds were not treated for broodiness because it was felt that the cage units were not conducive to broodiness and because the accuracy of detecting broody females in laying cages was questionable. Females were artificially inseminated for the first time on April 10, 1969, with 0.03 ml. of pooled semen. They were inseminated weekly for the next two weeks and at bi-weekly intervals thereafter. All females were trapnested, and data were obtained on egg production, fertility and hatchability throughout the experimental period. Fertile
80
EGG PROD LIGHT INTENSITY BROODINESS 5.4 86.1
70
/A
60 1- 50 z
-
1
-
u
a. 30 20 10
" ^ x
-1
;' v --,-<---
L .
2
lux lux
^"^^"K
UJ (U
1441
4
6
8
' • /
10
.
12 14 WEEKS
16
''•'
"•
18
20
22
24
FIG. 1. Weekly variation in percentage hen day egg production and broodiness by light intensity treatment (broodiness obtained for floor pens only).
eggs were determined by candling after 23 days of incubation. RESULTS
TABLE 2.—Turkey breeder diet (TB-2) crumbles Percentage by weight
Ingredient Ground yellow corn Stabilized fat Dehulled soybean meal (49% protein) Fish meal Meat and bone scrap Alfalfa meal Distillers dried solubles Defluorinated phosphate Ground limestone Iodinized salt Trace mineral mix1 Vitamin premix2 Total
65.05 2.00 12.50 5.00 5.00 2.50 2.50 1.00 3.50 0.40 0.05 0.50 100.00
Nutrient analysis Crude protein Crude fat Calcium Inorganic phosphorus 1
Egg production and broodiness. Figures 1, 2 and 3 show the weekly variation in percentage hen day egg production and percentage broodiness by treatments. Since broodiness in cages could not be determined accurately, percentages shown were calculated for those birds maintained on the conventional litter floors only, and only if they were treated for broodiness during the week in question. Figure 1 shows that, with respect to seasonal trends in egg production and broodiBO
EGG PROD. PEN TREAT. BROODINESS
70
18.72 5.33 2.51 0.67
Trace mineral mix contained 12% manganese and 12% zinc. 2 Vitamin premix contained the following ingredients per kg.: vit. A, 2.20 million I.U.; vit. D, 0.66 million I.C.U.; vit. E, 6.61 thousand I.U.; thiamine HC1, 0.22 g.; menadione sodium bisulfite, 0.71 g.; riboflavin, 1.32 g.; calcium-d-pantothenate, 3.31 g.; niacin, 8.82 g.; choline chloride, 74.96 g.; vit. Bj 2) 3.31 mg.; folic acid, 0.22 mg.; procaine penicillin, 2.20 mg.; ethoxyquin, 24.91 mg., plus a limestone carrier.
Cage
bO
/
50
"' ^ ^S*—\
40 30
I'
"""""^_ ^^^"^
20 10
•^ '
10
12 14 WEEKS
16
20
22
24
FIG. 2. Weekly variation in percentage hen day egg production and broodiness by pen treatment (broodiness obtained for floor pens only).
1442
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR. EGG PROD.
ff
_ /
TEMP
> S ^ ^ \
- -
_
{I \ ^ ^ X '••••..
\ \
N_ —» /
i
SROODINESS
I2.8°C 2I.I'C 29.4'C
X i
v
/ N . '"'••->••
i / i •
^w
\C. i
A^es^CN^,.,--^...../^..
V->/'. . 10 12 14 WEEKS
i
16
i •
18
i
20
• ^ - I
22
24
FIG. 3. Weekly variation in percentage hen day egg production and broodiness by temperature treatment (broodiness obtained for floor pens only).
ness, birds exposed to the two light intensities responded similarly. Figure 2 demonstrates that birds in cages maintained a higher rate of production from the fifth through the nineteenth week of production. The rapid decline following the peak of egg production by birds on the floor coincided closely to the initial broodiness cycle as is shown in the figure. Since a similar abrupt decline in egg production did not occur in cages, this could relate to a possible lower incidence of broodiness in cages. Some birds in cages did exhibit, on occasion, the classical symptoms of broodiness. In those cases, they went out of production and remained out of production for the remainder of the experiment. Egg production trends in Figure 3 show that birds in a constant temperature environment of 29.4°C. tended to lay at a lower rate than those maintained in 12.8° and 21.1°C. temperature pens. Temperature, as a factor in lowering egg production by increasing the incidence of broodiness, may be partially eliminated because the incidence of broodiness in the 21.1°C. pens was almost as high as that observed in the 29.4°C. pens (Figure 3); yet, egg production was lower in the latter. A more detailed study of the data revealed that
broodiness in females from the high temperature pens could not be effectively controlled by our method of treatment. The data showed that 91.7 and 84.2 percent of the time, broody symptoms of females in the 12.8 and 21.1°C. temperature environments, respectively, ceased and birds started laying again following broodiness treatment. On the other hand, only 47.4 percent of the birds came back into production in the 29.4°C. pens. Further evaluation of the temperature effects showed that 79.2 percent of the birds were out of production in the 29.4°C. pens at the termination of the experiment, while only 45.4 and 49.4 percent were out of production in the 12.8° and 21.1°C. environments, respectively. The averages for the number of eggs laid per hen are presented in Table 3 by treatments for 12- and 24-week production periods. Analyses of variance of these data (Table 4) showed that 12-week egg production was significantly affected by type of pen and temperature environments. Females in cages laid an average of 6.9 more eggs than those on the conventional litter floors. On the average, birds in the 29.4°C. environment laid 12.5 and 11.2 fewer eggs than those in the 12.8° and 21.1°C. tem-
TABLE 3.—Average egg production and percentage seltable eggs by light intensity, pen and temperature treatment1 Egg production/bird Treatment
Percentage settable eggs
12 weeks 24 weeks 12 weeks 24 weeks produc- produc- produc- production tion tion tion
Light intensity (lux)
5.4 86.1
37.4 41.2
60.1 66.9
86.5 85.4
84.4 82.7
Pen
Floor Cage
35.9 42.8
58.2 68.9
94.8 77.1
94.3 72.7
Temperature <°C.)
12.8 21.1 29.4
43.9 42.6 31.4
75.2 72.0 43.5
83.4 87.8 86.7
81.1 84.3 85.1
39.3
63.5.
86.0
83.5
Experimental mean 1
Unweighted means.
ENVIRONMENT AND TURKEY REPRODUCTIVE PERFORMANCE
1443
TABLE 4.—A nalyses of variance of average egg production and of percentage settable eggs (% transformed to arc sine) Mean squares Source of variation
Egg production
Degrees of
12 week period Treatment combinations (TC) 5 Temperature Ti vs. T 2 T i + T 2 vs. T 3 Light Temp. X light Pen treatment (PT) 1 PTXTC 5 PTXtemp. PTXlight P T X temp. X light Among pens (error) 12 Total
2 1 1 1 2 2 1 2
181.1** 376.6** 7.3 745.8** 84.4 33.9 285.2** 23.7 53.7 10.2 8.1 19.5
Settable eggs
24 week period
12 week period
24 week period
1188.6** 2428.1** 41.5 4814.6** 278.6 404.2 684.3 123.5 178.5 53.7 103.5 175.8
10.1 19.7 33.2 6.3 3.7 3.7 1465.3** 30.6 20.8 10.1 50.7 13.6
10.7 19.2 18.8 19.4 10.9 2.2 1938.3** 17.9 6.1 2.6 37.5 14.9
23
T!= 12.8°C, T2= 21.1°C.,T 3 =29.4 0 C. **P<0.01.
Figure 4 dramatically illustrates the perature pens, respectively. The temperature effects on the 2 4-week production data effects of the pen environments on biwere more dramatic. Birds in the 29.4°C. weekly percentages of settable, thin- and pens averaged 43.5 eggs, while those in the soft-shelled, and cracked and broken eggs. 12.8° and 21.1°C. pens laid an average of The percentage of settable eggs laid by 75.2 and 72.0 eggs, respectively. Total egg birds in cages decreased consistently production was not significantly different through 14 weeks of production as the perbetween the cage and floor pens for the 24- centage of thin- and soft-shelled eggs and week production period due to the in- the percentage of cracked and broken eggs creased variation among pens treated alike. Egg shell quality and egg weight. As eggs were collected, they were recorded as normal, thin-shelled, soft-shelled (no shell), cracked or broken. If an egg was broken and soft-shelled, it was considered softshelled. Utilizing these data, the percentages of settable (or saleable) eggs were calculated and the mean values summarized in Table 3. The cage pens caused a significantly lower percentage of settable eggs (Table 4) than did the conventional litter floor pens (72.7 and 94.3 percent, respectively). Environmental temperature and light intensity had no significant effect on percentage settable eggs.
80 70
_ 60 z o 50
PEN TREAT.
SETTABLE
CRACKED AND BROKEN
SOFT AND THIN SHELLED
Cage Floor
20 " 10 10
12 14 WEEKS
16
IS
20
22
24
FIG. 4. Bi-weekly variation in percentage settable eggs, cracked and broken eggs, soft and thin shelled eggs produced by pen environment.
1444
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR. TABLE 5.—Average egg weights and shell thickness by light intensity, pen and temperature treatment1 Means 2 and standard errors3
Treatment
Shell thickness (mm.)4
Egg weights (g.) Period 1
Period 2
Period 3
Period 1
Period 2
Period 3
Light intensity 5.4 (lux) 86.1
83.8 + 0.4" 83.8 + 0.4"
84.7 + 0.8" 84.7±0.8"
87.9 + 1.6" 86.5 + 1.1"
35.3 + 0.5" 34.5 + 0.5"
34.0 + 0.8" 34.0 + 0.8"
32.5 + 1.0" 33.8 + 0.8"
Pen
Floor Cage
84.1+0.4" 83.5±0.4»
85.4 + 0.8" 84.0 + 0.8"
87.2 + 1.7" 87.2 + 1.0"
35.0+0.5" 34.8 + 0.5"
35.3 + 1.0" 32.8 + 0.8 b
33.8 + 1.3" 33.5 + 0.8"
Temperature (°C.)
12.8 21.1 29.4
84.9 + 0.6" 83.9 + 0.6" 82.5±0.6b
86.5 + 0.9" 85.5 + 0.9" 82.1+0.9"
88.4+1.3" 88.6+1.3" 84.5 + 2.4"
35.0+0.5" 34.5±0.5" 35.0 + 0.5"
34.3 + 1.0" 34.3±1.0» 33.3 + 1.3"
34.0 + 0.8" 32.5±0.8" 32.0 + 1.8"
83.8
84.7
87.2
34.9
34.0
33.2
Experimental mean 1 2
Data subjected to least squares analysis to adjust for missing cells. Unweighted means. Any means within each sampling period and treatment that are designated with the same superscript are not significantly different from each other (P<0.05). 8
nxio- 2 .
increased over the same period. The incidence of thin- and soft-shelled eggs, and cracked and broken eggs remained rather low and constant over the entire experimental period in the floor pens. Since mechanical factors were constant, the increasing incidence of cracked and broken eggs indicates that the egg shells were gradually becoming weaker. Indeed, shell thicknesses for the second sampling period (Table 5) were found to be significantly less (P<0.05) for those birds maintained in cages when compared to those on the floors. It was noted that the average shell thickness of cracked eggs was 0.297 mm. and 0.320 mm. for the second and third periods, respectively. Eggs weights (Table 5) were significantly (P<0.05) higher for eggs taken after six (Period 1) and 14 (Period 2) weeks of production from birds in the 12.8° and 21.1°C. temperature environments than those in the 29.4°C. pens. Light intensity and pen treatments, however, did not significantly affect egg weights. As the breeding season progressed, egg weights tended to increase.
Fertility and hatchability. Percentage fertility and percentage hatchability of fertile eggs are presented in Table 6. The analyses of variance utilizing the arc sine transformation of these data (Table 7) showed that the percentage of fertile eggs from females maintained in laying cages was significantly less than from those on conventional litter floors. Neither light intensity nor pen temperature had any detectable
TABLE 6.—Average percentage fertility and hatchability of fertile eggs for the experimental period by light intensity, pen and temperature treatment1 Percentage Percentage hatchof eggs ability of fertile fertile eggs
Treatment
Light intensity (lux)
5.4 86.1
78.2 74.1
62.9 60.0
Pen
Floor Cage
80.4 71.9
63.9 59.0
Temperature (°C.)
12.8 21.1 29.4
74.8 74.3 79.4
62.6 63.6 58.2
76.2
61.4
Experimental mean Unweighted means.
E N V I R O N M E N T AND T U R K E Y REPRODUCTIVE PERFORMANCE
effect on percentage fertility. Unfortunately, the apparent infertile eggs were not broken-out to determine the exact nature of the problem. Hatchability of fertile eggs, under normal conditions at this station, averages approximately 80 percent, but in this experiment it averaged only 62 percent. Closer examination of the data showed that 10 to IS percent of the fertile eggs were pipped but did not hatch. Although the reason for the low hatchability in this experiment is not apparent at this time, the possibility does exist that the stock used or that some unknown deficiency in the diet could be contributing factors. Incubator effects can be discounted because eggs from other experiments set at the same time hatched normally. Since all eggs were treated alike, any treatment effects should have been detected. As it was, hatchability of fertile eggs was unaffected by the factors under study (Table 7). Feed consumption. Feed consumption per bird, summarized in Table 8, was found to be significantly affected by the pen and temperature environments (Table 9). Fecales maintained in cages consumed more feed than those in the floor pens. The method of orthogonal contrasts showed that each temperature effect was different.
TABLE 7.—Analyses of variance of fertility and
hatchability (% transformed to arc sine) Source of variation
Degrees of freedom
Treatment combinations (TC) 5 Temperature Light TempXlight Pen treatment (PT) 1 PTXTC 5 PTXtemp PTXlight PTXtemp Xlight Among pens (error) 12 Total *• (P<0.01).
2 1 2 2 1 2
Mean squares Fertility 24.4 37.2 41.8 2.9 217.5** 20.0 21.2 7.2 25.0 13.1
Hatchability 18.2 22.8 19.7 12.8 51.6 39.3 65.9 22.3 21.1 58.6
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TABLE 8.—Average feed consumption per bird for
0-12 and 0-24 weeks of production by light intensity, pen and temperature treatment1 Feed (kg.)/bird Treatment 0-12 weeks 0-24 weeks Light intensity (lux)
5.4 86.1
17.01 17.30
32.73 33.89
Pen
Floor Cage
15.72 18.59
30.99 35.63
Temperature
12.8 21.1 29.4
19.07 17.36 15.04
37.79 33.38 28.76
17.16
33.31
PC.)
Experimental mean 1
Unweighted means.
Further analysis showed a significant linear trend in both periods with feed consumption decreasing with increasing temperature. These trends reflect differential feed requirements for body maintenance and for egg production. Since broody birds tended to eat less feed, broodiness in floor pens may have been a factor in the differences found between floor environments. Body weights. Body weights at the end of 24 weeks of production were also found to be significantly affected by the pen and temperature environments. The average body TABLE 9.—Analyses of variance of average feed con-
sumption for 0-12 and 0-24 weeks of production
Source of variation
Mean squares Degrees of" Feed per bird freedom 0-12 weeks 0-24 weeks
Treatment combination (TC) 5 Temperature 2 T I S J . T2 1 T I + T I U J . Ta 1 Light 1 TempXlight 2 Pen treatment (PT) 1 PTXTC 5 PTXtemp 2 PTXlight 1 PTXtempXUght 2 Among pens (error) 12 Total
23
Ti = 12.8°C, Tj=21.1°C, Ts=29.4°C. >P<0.05. **P<0.01,
13.4** 32.8** 11.7* 53.8** 0.5 0.4 49.2** 2.2 3.8 1.2 1.1 1.6
71.1** 163.3** 77.9** 248.8** 8.2 10.3 129.1" 4.6 8.9 2.3 1.6 5.2
1446
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR.
weights and the standard errors for the temperature treatments were 9.6 ± 0.1 kg., 9.4 ± 0.1 kg. and 9.1 ± 0.1 kg. for the 12.8°, 21.1° and 29.4°C. pens, respectively. Caged birds weighed 9.6 ± 0.1 kg. while those on litter floors weighed only 9.1 ± 0.1 kg. The reduction of body weights in the high temperature pens was thought to have been due to reduced feed consumption and increased water consumption relative to feed consumption, while the body weight in the cage birds could be related to inactivity. Broody birds also lost weight; and broodiness, therefore, may have been a confounding factor. Molting. It was also observed that some females began molting during the fourth month of the experiment. At the end of the experiment the average percentage of birds molting was 45.7, 44.4 and 76.6 percent in the 12.8°, 21.1° and 29.4°C. temperature environments, respectively. The fact that molting birds generally go out of production or lay at reduced rates would indicate that this factor may have played a significant role in reducing egg production in the high temperature pens. Mortality. Another indication of the stress imposed by the 29.4°C. constant temperature environment was that 11.25 percent of the birds died in these pens. This compares with 2.75 percent in the 12.8°C. temperature pens and 3.75 percent in the 21.1°C. temperature pens. Mortality in the 5.4 and 86.1 lux light environments was 4.2 and 8.3 percent, respectively. Mortality in the floor pens averaged 8.75 percent while it averaged 10.0 percent in the cages. DISCUSSION Light intensity. The lack of light intensity effects on egg production in this study differs from the reports of Asmundson et al.
(1946) and Garland et al. (1961) who utilized 13 and 14 hours of light per day, respectively. Dorminey et al. (1970), however, found no light intensity effects while using 12 hours of light on pullets until peak production and then using 15 hours thereafter. It is possible that using 16 hours of light per day in the present experiment negated the effects of light intensity within the range studied. Laying cages vs. conventional litter pens. The 12-week findings in this work support those of Woodard et al. (1961) who observed during a 16-week period a higher percentage egg production from birds in laying cages as compared to those on litter floors. Laying cages appeared to cause a reduction in the percentage of settable eggs produced. Similar results were obtained by Woodard et al. (1961) and Wolford and Zindel (1970). The latter authors also found that oyster shell top-dressing of feed did not aid the situation. Increasing calcium levels of the diet (Atkinson et al., 1967) did not increase the percentage of settable eggs. The reduction in shell thickness which occurred suggests that the problem may be one of either nutritional or physiological factors or a combination of both involved in egg shell formation. Fundamental research designed to determine the basic causes of the high incidence of low shell quality in caged birds may be one of the most important areas of research in the immediate future. If egg shell quality can be improved, it would be instrumental in convincing turkey breeders to convert to caged breeder operations. Lowry et al. (1956), Bailey et al. (1959), Shupe and Quisenberry (1961), and Logan (1965) found that laying cages caused an increase in the average weight of eggs laid by chickens. Species differences may explain why cages did not have the
ENVIRONMENT AND TURKEY REPRODUCTIVE PERFORMANCE
same effect on egg weights of turkeys in this study. Higher average feed consumption in the cage birds in combination with their relative inactivity probably explains the higher body weight found for these birds. Bailey et al. (1959), Shupe and Quisenberry (1961) and Logan (1965) noted similar effects. The possibility exists that genotype by pen environment interactions, as suggested by Gowe (1955), Bailey et al. (1959), and Biswas and Craig (1970) with chickens, and with turkeys by Atkinson et al. (1967), could be an important consideration when interpreting the effects of cages versus floor pens on reproductive performance. It would appear, therefore, that selection of genotypes specifically suited to cage and floor pen environments should receive consideration by commercial breeders. Environmental temperature. Of the three factors considered, constant environmental temperatures appeared to have the most pronounced effect on the breeder turkeys used in this study. The report of Mueller (1961) indicates that chickens are similarly affected. As it is, temperature effects on egg production may be very complicated. High constant temperatures seem to inhibit effective broodiness control by conventional methods and to increase the percentage of birds molting and subsequently going out of production. This is further complicated by the fact that feed consumption is reduced in the high temperature environments. The report of Bray and Gesell (1961) suggests that egg production in various temperature environments will not differ if an adequate protein intake is maintained. In analyzing the situation, one must also consider the hormonal aspects. Thyroid activity has been shown to be closely related to egg production (Glick et al.,
1447
1959; and Sturkie, 1965). Therefore, increased egg production at the lower temperatures may be due to increased thyroid activity at these temperatures. Indeed, Glick et al. (1959) and Huston (1960) have shown that thyroids of chickens were larger at lower temperatures than at higher ones. A temperature-hormonal interaction has been further indicated because molting, which may be under progesterone and thyroid hormonal control (Sturkie, 1965), was found to be more prominent in the high temperature pens. Mueller (1961) suggested that constant high temperatures reduce egg shell thickness and egg weights in chickens. The present study indicated that egg weights but not shell thickness in turkeys are lowered by high constant temperatures. Species differences between turkeys and chickens may partially explain the differences in response found for shell thickness. It has been well documented that chickens under increasing temperatures lay thinner eggs [Warren and Schnepel (1940), Wilhelm (1940), Wilson (1949), Hutchinson (1953), Thornton and Moreng (1959) and Harrison and Biellier (1969)] and smaller eggs (Bennion and Warren, 1933; Bruckner, 1936; Lorenz and Almquist, 1936; Wilson, 1949; Mueller et al., 1951; Glick et al., 1959; Campos et al, 1960; Clark and Amin, 1965; and Lyle and Moreng, 1968). The results of the present experiment and of Marsden et al. (1966) showed no temperature effect on fertility or hatchability. These findings differ from those of Heywang (1944) and Glick et al. (1959). Since the latter two investigators were working with chickens, species differences may partially explain this contradiction. Another possible explanation for the different results is that they utilized natural matings while artificial insemination was used in the present experiment. It should be noted, however, that reports in which
1448
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR.
artificial insemination of chickens was used are also contradictory. Wilson (1949) found no effects, while Wilson et al. (1957), Howes et al. (1961), and Clark and Sarakoon (1967) reported that temperature does affect fertility and hatchability. The feed consumption and body weight results as affected by temperature in the present study agree with the results of experiments in which chickens were the tested species (Bennion and Warren, 1933; Bruckner, 1936; Campos et al., 1960; and Mueller, 1961). Since hens exhibiting broody characteristics were observed to eat relatively little feed, increased broodiness, compounded the temperature effect. ACKNOWLEDGEMENT Sincere appreciation is expressed to the Virginia Agricultural Foundation which provided a grant-in-aid in partial support of this investigation. The authors wish also to acknowledge the invaluable aid given by Lee Roy Barnett, Farm Manager, and the employees of the Turkey Research Center at Virginia Polytechnic Institute and State University. REFERENCES Albright, W. P., and R. B. Thompson, 1933. Securing early turkeys by stimulated egg production. Poultry Sci. 12: 124-128. Asmundson, V. S., F. W. Lorenz and B. D. Moses, 1946. Influence of light intensity on ovulation in turkeys. Poultry Sci. 25: 346-354. Atkinson, R. L., J. W. Bradley, J. R. Couch and J. H. Quisenberry, 1967. The calcium requirement of breeder turkeys. Poultry Sci. 46: 207214. Bailey, B. B., J. H. Quisenberry and J. Taylor, 1959. A comparison of performance of layers in cage and floor housing. Poultry Sci. 38: 565568. Bennion, N. L., and D. C. Warren, 1933. Temperature and its effect on egg size in the domestic fowl. Poultry Sci. 12: 69-82. Biswas, D. K., and J. V. Craig, 1970. Genotypeenvironment interactions in chickens selected
for high and low social dominance. Poultry Sci. 49:681-692. Bray, D. J., and J. A. Gesell, 1961. Studies with corn-soya laying diets. 4. Environmental temperature-a factor affecting performance of pullets fed diets suboptimal in protein. Poultry Sci. 40: 1328-1335. Bruckner, J. H., 1936. The effect of environmental conditions on winter egg production. Poultry Sci. 15:417-418. Campos, A. C , F. H. Wilcox and C. S. Shaffner, 1960. The influence of fast and slow rises in ambient temperature on production traits and mortality of laying pullets. Poultry Sci. 39: 119-129. Clark, C. E., and M. Amin, 1965. The adaptability of chicken to various temperatures. Poultry Sci. 44: 1003-1009. Clark, C. E., and K. Sarakoon, 1967. Influence of ambient temperature on reproductive traits of male and female chickens. Poultry Sci. 46: 1093-1098. Dorminey, R. W., J. E. Parker and W. H. McCluskey, 1970. Effects of light intensity on leg horn pullets during the development and laying periods. Poultry Sci. 49: 1657-1661. Garland, F. W., Jr., R. C. Eaton, D. E. Greene, H. L. Wilcke and R. M. Bethke, 1961. Duration and intensity of light for out-of-season egg production in turkeys. Poultry Sci. 40: 1406. Glick, B., J. Griffin and A. van Tienhoven, 1959. Effect of environment on reproduction characters and endocrine organs of New Hampshire chickens. Poultry Sci. 38: 1078-1087. Gowe, R. S., 1955. A comparison of the egg production of seven White Leghorn strains housed in two environments-floor pens and a laying battery. Poultry Sci. 34: 1198. Harrison, P. C , and H. V. Biellier, 1969. Physiological response of domestic fowl to abrupt changes of ambient air temperature. Poultry Sci. 48: 1034-1045. Heywang, B. W., 1944. Fertility and hatchability when the environmental temperature of chickens is high. Poultry Sci. 23 : 334-339. Howes, J. R., W. Grub and C. A. Rollo, 1961. The effects of high constant environmental temperatures upon the duration of fertility. Poultry Sci. 40: 1416. Huston, T. M., 1960. The effects of high environmental temperatures upon blood constituents and thyroid activity of domestic fowl. Poultry Sci. 39: 1260. Hutchinson, J. C. D., 1953. Effect of hot climates on egg weight. Poultry Sci. 32: 692-690.
ENVIRONMENT AND T U R K E Y REPRODUCTIVE PERFORMANCE
Jones, D. G., and W. Kohlmeyer, 1947. The relationship of broodiness and pause to reproductive performance in turkeys. Poultry Sci. 26: 545. Kosin, I. L., M. S. Mitchell and W. T. Burrows, 1952. Influence of temperature on the reproductive performance of Broad Breasted Bronze toms. Poultry Sci. 3 1 : 180-182. Kosin, I. L., and M. S. Mitchell, 1955a. Ambient temperature as a factor in turkey reproduction. 1. The effect of preheating males and females on their subsequent breeding pen performance. Poultry Sci. 34: 484-496. Kosin, I. L., and M. S. Mitchell, 1955b. 2. The effect of artificially lowered air temperature on the breeding activity of males in late spring and summer. Poultry Sci. 34: 499-505. Logan, V. A., 1965. Influence of cage versus floor, density and dubbing on laying house performance. Poultry Sci. 44: 974-979. Lorenz, F. W., and H. J. Almquist, 1936. Seasonal variations in egg quality. Poultry Sci. 15: 1418. Lowry, D. C , I. M. Lerner and L. W. Taylor, 1956. Intra-flock genetic merit under floor and cage managements. Poultry Sci. 35: 1034-1043. Lyle, G. R., and R. E. Moreng, 1968. Elevated environmental temperature and duration of post exposure ascorbic acid administration. Poultry Sci. 47 : 410-417. Marsden, S. J., 1936. A study of egg production in bronze turkeys. Poultry Sci. 15: 439^45. Marsden, S. J., L. M. Lucas and S. P. Wilson, 1966. The influence of day length and environment on reproduction, broodiness, and mortality of turkeys. Poultry Sci. 45: 668-675. McCartney, M. G., 1956. Reproductive performance in broody and non-broody turkeys. Poultry Sci. 35: 763-765. Mitchell, M. S., and I. L. Kosin, 1954. The effect of controlled ambient temperature on some factors associated with egg laying in turkeys. Poultry Sci. 3 3 : 186-191. Mueller, W. J., 1961. The effect of constant and fluctuating environmental temperatures on the biological performance of laying pullets. Poultry Sci. 40: 1562-1571.
1440
Mueller, C. D., T. B. Avery, H. D. Smith and R. E. Clegg, 1951. Effects of controlled light and temperature for laying hens. Poultry Sci. 30: 679-686. Parker, J. E., 1947. The influence of season on reproduction in turkeys. Poultry Sci. 26: 118121. Parker, J. E., and O. A. Barton, 1945. Relation of broodiness to reproduction in turkey hens. N. Dak. Bimo. Bui. 8 ( 2 ) : 3-5. Shoffner, R. N., C. R. Polley, R. E. Burger and E. L. Johnson, 1962. Light regulation in turkey management. 2. Female reproductive performance. Poultry Sci. 4 1 : 1563-1570. Shupe, W. D., and J. H. Quisenberry, 1961. Effect of certain rearing and laying house environments on performance of incross egg production type pullets. Poultry Sci. 40: 1165-1171. Smyth, J. R., Jr., and A. T. Leighton, Jr., 1953. A study of certain factors affecting fertility in the turkey. Poultry Sci. 32: 1004-1013. Sturkie, 1965. Avian Physiology. Ithaca, New York: Comstock Publishing Associates, Cornell University Press. Thornton, P. A., and R. E. Moreng, 1959. Further evidence on the value of ascorbic acid for maintenance of shell quality in warm environmental temperature. Poultry Sci. 38: 594-599. Warren, D. C , and R. L. Schnepel, 1940. The effect of air temperatures on egg shell thickness in the fowl. Poultry Sci. 19: 67-72. Wilhelm, L. A., 1940. Some factors affecting variations in egg shell quality. Poultry Sci. 19: 246253. Wilson, W. O., 1949. High environmental temperatures as affecting the reaction of laying hens to iodized casein. Poultry Sci. 29: 581-592. Wilson, W. O., E. H. McNally and H. Ota, 1957. Temperature and calorimeter study on hens in individual cages. Poultry Sci. 36: 1254-1261. Wolford, J. H., and H. C. Zindel, 1970. Caged turkey breeder hens: shell quality versus oyster shell supplementation. Poultry Sci. 49: 814816. Woodard, A. E., H. Abplanalp and F. X. Ogasawara, 1961. Egg and semen production performance of turkeys under cage management. Poultry Sci. 49: 884-890.
APRIL 11-13, 1973. FACT FINDING CONFERENCE, POULTRY AND EGG INSTITUTE OF AMERICA. RIVERGATE EXHIBITION CENTER, NEW ORLEANS, LOUISIANA
ABSTRACT The study presented was designed to determine the effects of light intensities of 5.4 and 86.1 lux, of laying cages versus conventional litter floors and of constant environmental temperatures of 12.8°, 21.1° and 2°.4°C. on the reproductive performance of Large White female turkeys. A light intensity of 5.4 lux yielded comparable results to that of 86.1 lux when 16 hours of light were provided. Turkey females in laying cages laid at a higher rate over the first 12 weeks of production and showed an increase in feed consumption and body weight over those maintained in conventional litter pens. No significant differences were observed between the two pen environments for total egg production, hatchability of fertile eggs and egg weights. Percentage settable eggs and percentage fertility were lower from females maintained in cages. The percentage of cracked and broken, and soft- and thin-shelled eggs from cage birds increased over the production period. A constant pen temperature of 29.4° C. dramatically reduced egg production below that obtained from females maintained at 12.8° and 21.1 °C. The high pen temperature also reduced feed consumption, body weights, egg weights, the effectiveness of broodiness control and increased the incidence of birds molting and mortality. Fertility, hatchability, percentage settable eggs and shell thickness were unaffected by the imposed temperature environments. Pen temperatures of 12.8° and 21.°C. yielded comparable results for all reproductive parameters studied. It is concluded that reproductive potential of turkeys in the present study was maximized on conventional litter floors with constant temperatures between 12.8° and 21.1°C. and light intensities between S.4 and 86.1 lux. POULTRY SCIENCE 51: 1438-1449,
I
T has become apparent, with the trend toward complete confinement of turkey breeder hens, that very little is known about the environmental factors that infiuence reproductive functions of turkeys under housed conditions. It is important, therefore, that research be developed that will allow experimental control of certain environmental factors in order to evaluate the relative contributions each makes toward the expression of maximum reproductive potential. The stimulatory effect of artificial illumination on egg production in turkeys was demonstrated by Albright and Thompson (1933) and Marsden (1936). Asmundson 7~. ; " ~ ~ \ 7~
1972
et al. (1946) found that a minimum light intensity of 21.5 lux was needed to induce the most rapid response in egg production and that this level of light intensity increased total egg production over that obtained with 1.1, 3.2 or 10.8 lux. Garland et al. (1961) reported similar results. The latter also reported that increasing the light intensity from 21.S to 366.0 lux by gradual increments at four week intervals resulted in higher total egg production. The egg production industry has accepted the use of laying cages for chickens. The turkey industry, consequently, has been pondering the applicability of cages for turkey reproduction. Woodard et al. (1961) showed that Broad Breasted
A portion of a thesis prepared by the senior .1 ' . B r o n z e females ke author in partial fulfillment of the requirements Pt ln ca8es lald m o r e for the degree of Master of Science. eggs than did floor birds, but they also laid 1438
ENVIRONMENT AND TURKEY REPRODUCTIVE PERFORMANCE
many more soft-shelled eggs. Similar problems with egg shell quality were found by Wolford and Zindel (1970). Preliminary studies at this station utilizing Medium White turkeys showed no differences in egg production, egg weights, hatchability of fertile eggs, feed consumed per bird and the amount of feed consumed per egg produced between birds maintained in cages and those on conventional litter floors. Fertility, however, appeared to be somewhat lower in birds maintained in cages. While studies concerning the effects of ambient temperature on the reproductive performance of chickens are voluminous, little has been reported with reference to turkeys. Initial information by Parkerj (1947) and later by Shoffner et al. (1962) suggests that egg production decreases as seasonal temperatures increase during the breeding season. Mitchell and Kosin (19S4) and Kosin and Mitchell (1955a) found that pre-heating hens before they commenced egg production resulted in higher initial egg production levels. Total egg production was unaffected by pre-heating treatments. They also reported that maintaining hens at 10°C. during the breeding season was detrimental to egg production due to increased broodiness. Marsden et al. (1966) noted that an ambient temperature of 18.3°C. provided a stimulatory effect on egg production of birds under an 11-hour photoperiod. The effect, however, was considerably less under 13- and 15-hour photoperiods. Parker (1947) found that egg weights; increased from January to June. Mitchell and Kosin (1954) observed that egg weights were lower in constant 18.3°C. pens than in uncontrolled temperature pens. In his report, Parker (1947) found fertility to be high until May and June, followed by a gradual decline thereafter. Hatchability of fertile eggs increased to
1439
late February (point of highest production) followed by a decline as the breeding season progressed. Pre-conditioning of males by supplemental heat when they were in a cold environment was reported by Kosin et al. (1952) and Kosin and Mitchell (1955a) to be advantageous for fertility under natural mating conditions. Kosin and Mitchell (1955b) also reported that the cooling of Broad Breasted Bronze males in the months of May, June and July, at least temporarily, halted the seasonal downward trend in fertility. Marsden et al. (1966), on the other hand, found that fertility and hatchability under their experimental conditions were unaffected by temperature and light. The incidence of broodiness in turkey populations is a major consideration in the production of turkey hatching eggs. The deleterious effects of broodiness on egg production and on subsequent poult production has been well documented by Parker and Barton (1945), Jones and Kohlmeyer (1947), Smyth and Leighton (1953) and McCartney (1956). In comparing constant environmental temperatures with uncontrolled ones, Mitchell and Kosin (1954) and Kosin and Mitchell (1955a) found that broodiness increased in constant temperature pens, resulting in lower egg production. Marsden et al. (1966) also observed an increasing incidence of broodiness during the summer months. The objectives of this study were: (1) to determine the effect of environmental temperature and light intensity on reproductive performance; (2) to evaluate the relative merits of conventional litter pens versus laying cages on egg production, fertility, hatchability, broodiness, egg weight and egg shell quality; and (3) ascertain the optimum combination of temperature, light intensity and floor pen environment for maximum expression of reproductive potential.
1440
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR.
was 0.64 cm. wide and spaced 0.64 cm. apart. The light intensity of 5.4 lux was proPen Light Pen Number vided in half of the pens by two 7.5-watt environment in%nfy temperature of (lux) (°C.) females bulbs in each pen. A light intensity of 86.1 ; S.4 12.8 120 lux was provided in the remaining half of 21.1 ' > .20 the pens by two 60-watt bulbs in each of 29.4 ;*W['M Floor these pens. 86.1 12.8 20 Pen temperatures were maintained at the 21.1 20 29.4 20 designated temperatures ± 2.8°C. through the use of thermostatically controlled (Day5.4 12.8 20 21.1 20 ton temperature control thermostats, models 29.4 20 21E 206 and 21E 207) heaters and air Cage 86.1 12.8 20 conditioners. 21.1 20 Duplicate pens of ten females each were 29.4 20 placed in each treatment combination. The observational unit for this experiment consisted of ten females within each pen enviMATERIALS AND METHODS ronment, light intensity and pen temperaTwo hundred forty Large White turkey ture subclass. For a two-day period at the beginning of females and 60 males of the same age and strain were restricted at 24 weeks of age to this experiment, light intensity was mainsix hours of light per day. On February 28, tained in all pens at 86.1 lux to insure that 1969, the 3 4-week-old males were exposed the birds would find feed and water. The to stimulatory light levels of 16 hours of V.P.I. & S.U. turkey breeder diet (Table natural plus artificial light per day at a 2) and water were provided ad libitum to minimum light intensity of 86.1 lux. On all birds. Feed records were kept on an inMarch 21, 1969, after being under re- dividual bird basis for the cage birds and stricted lighting for 13 weeks, 120 females on a pen basis for the floor pens. Feed was were randomly assigned to laying cages and weighed back every 28 days beginning with another 120 were placed in conventional lit- March 21. Body weight and molt condition ter floor pens. Females within each pen en- were also recorded at that time. Egg weights were obtained on April 28 vironment were exposed to two light intensities and three temperature treatments in a (Period 1), June 23 (Period 2) and August factorial arrangement (Table 1). Sixteen 18, 1969 (Period 3). Egg shell thickness hours of continuous artificial illumination measurements were determined from threeper day were provided throughout the ex- day samples of eggs beginning on May 13, July 22 and September 7, 1969. Shell thickperimental period. Pen environments used were conven- ness of each egg represented the average of tional wood-shaving floors and single bird, a measurement taken from each end and double-decked laying cages. One birds was from the middle of each egg by cracking place in each of five cages on the top and the egg and peeling off a piece of shell. The bottom deck. An individual cage measured instrument used to measure these shells 43.2 cm. wide, 61.0 cm. long and 64.8 cm. was an Ames Thickness Measurer Model high. The floor of each cage was 16 gauge, 2SE, having a curved anvil, and allowing plastic coated, flat metal strapping which an approximation to the nearest 0.0001 of TABLE 1.—Experimental design and the number offemales used
ENVIRONMENT AND TURKEY REPRODUCTIVE PERFORMANCE
an inch which was converted to millimeters. Broody birds from the floor pens were treated for five days following detection by placing them in a broody coop equipped with a wire floor. Cage birds were not treated for broodiness because it was felt that the cage units were not conducive to broodiness and because the accuracy of detecting broody females in laying cages was questionable. Females were artificially inseminated for the first time on April 10, 1969, with 0.03 ml. of pooled semen. They were inseminated weekly for the next two weeks and at bi-weekly intervals thereafter. All females were trapnested, and data were obtained on egg production, fertility and hatchability throughout the experimental period. Fertile
80
EGG PROD LIGHT INTENSITY BROODINESS 5.4 86.1
70
/A
60 1- 50 z
-
1
-
u
a. 30 20 10
" ^ x
-1
;' v --,-<---
L .
2
lux lux
^"^^"K
UJ (U
1441
4
6
8
' • /
10
.
12 14 WEEKS
16
''•'
"•
18
20
22
24
FIG. 1. Weekly variation in percentage hen day egg production and broodiness by light intensity treatment (broodiness obtained for floor pens only).
eggs were determined by candling after 23 days of incubation. RESULTS
TABLE 2.—Turkey breeder diet (TB-2) crumbles Percentage by weight
Ingredient Ground yellow corn Stabilized fat Dehulled soybean meal (49% protein) Fish meal Meat and bone scrap Alfalfa meal Distillers dried solubles Defluorinated phosphate Ground limestone Iodinized salt Trace mineral mix1 Vitamin premix2 Total
65.05 2.00 12.50 5.00 5.00 2.50 2.50 1.00 3.50 0.40 0.05 0.50 100.00
Nutrient analysis Crude protein Crude fat Calcium Inorganic phosphorus 1
Egg production and broodiness. Figures 1, 2 and 3 show the weekly variation in percentage hen day egg production and percentage broodiness by treatments. Since broodiness in cages could not be determined accurately, percentages shown were calculated for those birds maintained on the conventional litter floors only, and only if they were treated for broodiness during the week in question. Figure 1 shows that, with respect to seasonal trends in egg production and broodiBO
EGG PROD. PEN TREAT. BROODINESS
70
18.72 5.33 2.51 0.67
Trace mineral mix contained 12% manganese and 12% zinc. 2 Vitamin premix contained the following ingredients per kg.: vit. A, 2.20 million I.U.; vit. D, 0.66 million I.C.U.; vit. E, 6.61 thousand I.U.; thiamine HC1, 0.22 g.; menadione sodium bisulfite, 0.71 g.; riboflavin, 1.32 g.; calcium-d-pantothenate, 3.31 g.; niacin, 8.82 g.; choline chloride, 74.96 g.; vit. Bj 2) 3.31 mg.; folic acid, 0.22 mg.; procaine penicillin, 2.20 mg.; ethoxyquin, 24.91 mg., plus a limestone carrier.
Cage
bO
/
50
"' ^ ^S*—\
40 30
I'
"""""^_ ^^^"^
20 10
•^ '
10
12 14 WEEKS
16
20
22
24
FIG. 2. Weekly variation in percentage hen day egg production and broodiness by pen treatment (broodiness obtained for floor pens only).
1442
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR. EGG PROD.
ff
_ /
TEMP
> S ^ ^ \
- -
_
{I \ ^ ^ X '••••..
\ \
N_ —» /
i
SROODINESS
I2.8°C 2I.I'C 29.4'C
X i
v
/ N . '"'••->••
i / i •
^w
\C. i
A^es^CN^,.,--^...../^..
V->/'. . 10 12 14 WEEKS
i
16
i •
18
i
20
• ^ - I
22
24
FIG. 3. Weekly variation in percentage hen day egg production and broodiness by temperature treatment (broodiness obtained for floor pens only).
ness, birds exposed to the two light intensities responded similarly. Figure 2 demonstrates that birds in cages maintained a higher rate of production from the fifth through the nineteenth week of production. The rapid decline following the peak of egg production by birds on the floor coincided closely to the initial broodiness cycle as is shown in the figure. Since a similar abrupt decline in egg production did not occur in cages, this could relate to a possible lower incidence of broodiness in cages. Some birds in cages did exhibit, on occasion, the classical symptoms of broodiness. In those cases, they went out of production and remained out of production for the remainder of the experiment. Egg production trends in Figure 3 show that birds in a constant temperature environment of 29.4°C. tended to lay at a lower rate than those maintained in 12.8° and 21.1°C. temperature pens. Temperature, as a factor in lowering egg production by increasing the incidence of broodiness, may be partially eliminated because the incidence of broodiness in the 21.1°C. pens was almost as high as that observed in the 29.4°C. pens (Figure 3); yet, egg production was lower in the latter. A more detailed study of the data revealed that
broodiness in females from the high temperature pens could not be effectively controlled by our method of treatment. The data showed that 91.7 and 84.2 percent of the time, broody symptoms of females in the 12.8 and 21.1°C. temperature environments, respectively, ceased and birds started laying again following broodiness treatment. On the other hand, only 47.4 percent of the birds came back into production in the 29.4°C. pens. Further evaluation of the temperature effects showed that 79.2 percent of the birds were out of production in the 29.4°C. pens at the termination of the experiment, while only 45.4 and 49.4 percent were out of production in the 12.8° and 21.1°C. environments, respectively. The averages for the number of eggs laid per hen are presented in Table 3 by treatments for 12- and 24-week production periods. Analyses of variance of these data (Table 4) showed that 12-week egg production was significantly affected by type of pen and temperature environments. Females in cages laid an average of 6.9 more eggs than those on the conventional litter floors. On the average, birds in the 29.4°C. environment laid 12.5 and 11.2 fewer eggs than those in the 12.8° and 21.1°C. tem-
TABLE 3.—Average egg production and percentage seltable eggs by light intensity, pen and temperature treatment1 Egg production/bird Treatment
Percentage settable eggs
12 weeks 24 weeks 12 weeks 24 weeks produc- produc- produc- production tion tion tion
Light intensity (lux)
5.4 86.1
37.4 41.2
60.1 66.9
86.5 85.4
84.4 82.7
Pen
Floor Cage
35.9 42.8
58.2 68.9
94.8 77.1
94.3 72.7
Temperature <°C.)
12.8 21.1 29.4
43.9 42.6 31.4
75.2 72.0 43.5
83.4 87.8 86.7
81.1 84.3 85.1
39.3
63.5.
86.0
83.5
Experimental mean 1
Unweighted means.
ENVIRONMENT AND TURKEY REPRODUCTIVE PERFORMANCE
1443
TABLE 4.—A nalyses of variance of average egg production and of percentage settable eggs (% transformed to arc sine) Mean squares Source of variation
Egg production
Degrees of
12 week period Treatment combinations (TC) 5 Temperature Ti vs. T 2 T i + T 2 vs. T 3 Light Temp. X light Pen treatment (PT) 1 PTXTC 5 PTXtemp. PTXlight P T X temp. X light Among pens (error) 12 Total
2 1 1 1 2 2 1 2
181.1** 376.6** 7.3 745.8** 84.4 33.9 285.2** 23.7 53.7 10.2 8.1 19.5
Settable eggs
24 week period
12 week period
24 week period
1188.6** 2428.1** 41.5 4814.6** 278.6 404.2 684.3 123.5 178.5 53.7 103.5 175.8
10.1 19.7 33.2 6.3 3.7 3.7 1465.3** 30.6 20.8 10.1 50.7 13.6
10.7 19.2 18.8 19.4 10.9 2.2 1938.3** 17.9 6.1 2.6 37.5 14.9
23
T!= 12.8°C, T2= 21.1°C.,T 3 =29.4 0 C. **P<0.01.
Figure 4 dramatically illustrates the perature pens, respectively. The temperature effects on the 2 4-week production data effects of the pen environments on biwere more dramatic. Birds in the 29.4°C. weekly percentages of settable, thin- and pens averaged 43.5 eggs, while those in the soft-shelled, and cracked and broken eggs. 12.8° and 21.1°C. pens laid an average of The percentage of settable eggs laid by 75.2 and 72.0 eggs, respectively. Total egg birds in cages decreased consistently production was not significantly different through 14 weeks of production as the perbetween the cage and floor pens for the 24- centage of thin- and soft-shelled eggs and week production period due to the in- the percentage of cracked and broken eggs creased variation among pens treated alike. Egg shell quality and egg weight. As eggs were collected, they were recorded as normal, thin-shelled, soft-shelled (no shell), cracked or broken. If an egg was broken and soft-shelled, it was considered softshelled. Utilizing these data, the percentages of settable (or saleable) eggs were calculated and the mean values summarized in Table 3. The cage pens caused a significantly lower percentage of settable eggs (Table 4) than did the conventional litter floor pens (72.7 and 94.3 percent, respectively). Environmental temperature and light intensity had no significant effect on percentage settable eggs.
80 70
_ 60 z o 50
PEN TREAT.
SETTABLE
CRACKED AND BROKEN
SOFT AND THIN SHELLED
Cage Floor
20 " 10 10
12 14 WEEKS
16
IS
20
22
24
FIG. 4. Bi-weekly variation in percentage settable eggs, cracked and broken eggs, soft and thin shelled eggs produced by pen environment.
1444
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR. TABLE 5.—Average egg weights and shell thickness by light intensity, pen and temperature treatment1 Means 2 and standard errors3
Treatment
Shell thickness (mm.)4
Egg weights (g.) Period 1
Period 2
Period 3
Period 1
Period 2
Period 3
Light intensity 5.4 (lux) 86.1
83.8 + 0.4" 83.8 + 0.4"
84.7 + 0.8" 84.7±0.8"
87.9 + 1.6" 86.5 + 1.1"
35.3 + 0.5" 34.5 + 0.5"
34.0 + 0.8" 34.0 + 0.8"
32.5 + 1.0" 33.8 + 0.8"
Pen
Floor Cage
84.1+0.4" 83.5±0.4»
85.4 + 0.8" 84.0 + 0.8"
87.2 + 1.7" 87.2 + 1.0"
35.0+0.5" 34.8 + 0.5"
35.3 + 1.0" 32.8 + 0.8 b
33.8 + 1.3" 33.5 + 0.8"
Temperature (°C.)
12.8 21.1 29.4
84.9 + 0.6" 83.9 + 0.6" 82.5±0.6b
86.5 + 0.9" 85.5 + 0.9" 82.1+0.9"
88.4+1.3" 88.6+1.3" 84.5 + 2.4"
35.0+0.5" 34.5±0.5" 35.0 + 0.5"
34.3 + 1.0" 34.3±1.0» 33.3 + 1.3"
34.0 + 0.8" 32.5±0.8" 32.0 + 1.8"
83.8
84.7
87.2
34.9
34.0
33.2
Experimental mean 1 2
Data subjected to least squares analysis to adjust for missing cells. Unweighted means. Any means within each sampling period and treatment that are designated with the same superscript are not significantly different from each other (P<0.05). 8
nxio- 2 .
increased over the same period. The incidence of thin- and soft-shelled eggs, and cracked and broken eggs remained rather low and constant over the entire experimental period in the floor pens. Since mechanical factors were constant, the increasing incidence of cracked and broken eggs indicates that the egg shells were gradually becoming weaker. Indeed, shell thicknesses for the second sampling period (Table 5) were found to be significantly less (P<0.05) for those birds maintained in cages when compared to those on the floors. It was noted that the average shell thickness of cracked eggs was 0.297 mm. and 0.320 mm. for the second and third periods, respectively. Eggs weights (Table 5) were significantly (P<0.05) higher for eggs taken after six (Period 1) and 14 (Period 2) weeks of production from birds in the 12.8° and 21.1°C. temperature environments than those in the 29.4°C. pens. Light intensity and pen treatments, however, did not significantly affect egg weights. As the breeding season progressed, egg weights tended to increase.
Fertility and hatchability. Percentage fertility and percentage hatchability of fertile eggs are presented in Table 6. The analyses of variance utilizing the arc sine transformation of these data (Table 7) showed that the percentage of fertile eggs from females maintained in laying cages was significantly less than from those on conventional litter floors. Neither light intensity nor pen temperature had any detectable
TABLE 6.—Average percentage fertility and hatchability of fertile eggs for the experimental period by light intensity, pen and temperature treatment1 Percentage Percentage hatchof eggs ability of fertile fertile eggs
Treatment
Light intensity (lux)
5.4 86.1
78.2 74.1
62.9 60.0
Pen
Floor Cage
80.4 71.9
63.9 59.0
Temperature (°C.)
12.8 21.1 29.4
74.8 74.3 79.4
62.6 63.6 58.2
76.2
61.4
Experimental mean Unweighted means.
E N V I R O N M E N T AND T U R K E Y REPRODUCTIVE PERFORMANCE
effect on percentage fertility. Unfortunately, the apparent infertile eggs were not broken-out to determine the exact nature of the problem. Hatchability of fertile eggs, under normal conditions at this station, averages approximately 80 percent, but in this experiment it averaged only 62 percent. Closer examination of the data showed that 10 to IS percent of the fertile eggs were pipped but did not hatch. Although the reason for the low hatchability in this experiment is not apparent at this time, the possibility does exist that the stock used or that some unknown deficiency in the diet could be contributing factors. Incubator effects can be discounted because eggs from other experiments set at the same time hatched normally. Since all eggs were treated alike, any treatment effects should have been detected. As it was, hatchability of fertile eggs was unaffected by the factors under study (Table 7). Feed consumption. Feed consumption per bird, summarized in Table 8, was found to be significantly affected by the pen and temperature environments (Table 9). Fecales maintained in cages consumed more feed than those in the floor pens. The method of orthogonal contrasts showed that each temperature effect was different.
TABLE 7.—Analyses of variance of fertility and
hatchability (% transformed to arc sine) Source of variation
Degrees of freedom
Treatment combinations (TC) 5 Temperature Light TempXlight Pen treatment (PT) 1 PTXTC 5 PTXtemp PTXlight PTXtemp Xlight Among pens (error) 12 Total *• (P<0.01).
2 1 2 2 1 2
Mean squares Fertility 24.4 37.2 41.8 2.9 217.5** 20.0 21.2 7.2 25.0 13.1
Hatchability 18.2 22.8 19.7 12.8 51.6 39.3 65.9 22.3 21.1 58.6
1445
TABLE 8.—Average feed consumption per bird for
0-12 and 0-24 weeks of production by light intensity, pen and temperature treatment1 Feed (kg.)/bird Treatment 0-12 weeks 0-24 weeks Light intensity (lux)
5.4 86.1
17.01 17.30
32.73 33.89
Pen
Floor Cage
15.72 18.59
30.99 35.63
Temperature
12.8 21.1 29.4
19.07 17.36 15.04
37.79 33.38 28.76
17.16
33.31
PC.)
Experimental mean 1
Unweighted means.
Further analysis showed a significant linear trend in both periods with feed consumption decreasing with increasing temperature. These trends reflect differential feed requirements for body maintenance and for egg production. Since broody birds tended to eat less feed, broodiness in floor pens may have been a factor in the differences found between floor environments. Body weights. Body weights at the end of 24 weeks of production were also found to be significantly affected by the pen and temperature environments. The average body TABLE 9.—Analyses of variance of average feed con-
sumption for 0-12 and 0-24 weeks of production
Source of variation
Mean squares Degrees of" Feed per bird freedom 0-12 weeks 0-24 weeks
Treatment combination (TC) 5 Temperature 2 T I S J . T2 1 T I + T I U J . Ta 1 Light 1 TempXlight 2 Pen treatment (PT) 1 PTXTC 5 PTXtemp 2 PTXlight 1 PTXtempXUght 2 Among pens (error) 12 Total
23
Ti = 12.8°C, Tj=21.1°C, Ts=29.4°C. >P<0.05. **P<0.01,
13.4** 32.8** 11.7* 53.8** 0.5 0.4 49.2** 2.2 3.8 1.2 1.1 1.6
71.1** 163.3** 77.9** 248.8** 8.2 10.3 129.1" 4.6 8.9 2.3 1.6 5.2
1446
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR.
weights and the standard errors for the temperature treatments were 9.6 ± 0.1 kg., 9.4 ± 0.1 kg. and 9.1 ± 0.1 kg. for the 12.8°, 21.1° and 29.4°C. pens, respectively. Caged birds weighed 9.6 ± 0.1 kg. while those on litter floors weighed only 9.1 ± 0.1 kg. The reduction of body weights in the high temperature pens was thought to have been due to reduced feed consumption and increased water consumption relative to feed consumption, while the body weight in the cage birds could be related to inactivity. Broody birds also lost weight; and broodiness, therefore, may have been a confounding factor. Molting. It was also observed that some females began molting during the fourth month of the experiment. At the end of the experiment the average percentage of birds molting was 45.7, 44.4 and 76.6 percent in the 12.8°, 21.1° and 29.4°C. temperature environments, respectively. The fact that molting birds generally go out of production or lay at reduced rates would indicate that this factor may have played a significant role in reducing egg production in the high temperature pens. Mortality. Another indication of the stress imposed by the 29.4°C. constant temperature environment was that 11.25 percent of the birds died in these pens. This compares with 2.75 percent in the 12.8°C. temperature pens and 3.75 percent in the 21.1°C. temperature pens. Mortality in the 5.4 and 86.1 lux light environments was 4.2 and 8.3 percent, respectively. Mortality in the floor pens averaged 8.75 percent while it averaged 10.0 percent in the cages. DISCUSSION Light intensity. The lack of light intensity effects on egg production in this study differs from the reports of Asmundson et al.
(1946) and Garland et al. (1961) who utilized 13 and 14 hours of light per day, respectively. Dorminey et al. (1970), however, found no light intensity effects while using 12 hours of light on pullets until peak production and then using 15 hours thereafter. It is possible that using 16 hours of light per day in the present experiment negated the effects of light intensity within the range studied. Laying cages vs. conventional litter pens. The 12-week findings in this work support those of Woodard et al. (1961) who observed during a 16-week period a higher percentage egg production from birds in laying cages as compared to those on litter floors. Laying cages appeared to cause a reduction in the percentage of settable eggs produced. Similar results were obtained by Woodard et al. (1961) and Wolford and Zindel (1970). The latter authors also found that oyster shell top-dressing of feed did not aid the situation. Increasing calcium levels of the diet (Atkinson et al., 1967) did not increase the percentage of settable eggs. The reduction in shell thickness which occurred suggests that the problem may be one of either nutritional or physiological factors or a combination of both involved in egg shell formation. Fundamental research designed to determine the basic causes of the high incidence of low shell quality in caged birds may be one of the most important areas of research in the immediate future. If egg shell quality can be improved, it would be instrumental in convincing turkey breeders to convert to caged breeder operations. Lowry et al. (1956), Bailey et al. (1959), Shupe and Quisenberry (1961), and Logan (1965) found that laying cages caused an increase in the average weight of eggs laid by chickens. Species differences may explain why cages did not have the
ENVIRONMENT AND TURKEY REPRODUCTIVE PERFORMANCE
same effect on egg weights of turkeys in this study. Higher average feed consumption in the cage birds in combination with their relative inactivity probably explains the higher body weight found for these birds. Bailey et al. (1959), Shupe and Quisenberry (1961) and Logan (1965) noted similar effects. The possibility exists that genotype by pen environment interactions, as suggested by Gowe (1955), Bailey et al. (1959), and Biswas and Craig (1970) with chickens, and with turkeys by Atkinson et al. (1967), could be an important consideration when interpreting the effects of cages versus floor pens on reproductive performance. It would appear, therefore, that selection of genotypes specifically suited to cage and floor pen environments should receive consideration by commercial breeders. Environmental temperature. Of the three factors considered, constant environmental temperatures appeared to have the most pronounced effect on the breeder turkeys used in this study. The report of Mueller (1961) indicates that chickens are similarly affected. As it is, temperature effects on egg production may be very complicated. High constant temperatures seem to inhibit effective broodiness control by conventional methods and to increase the percentage of birds molting and subsequently going out of production. This is further complicated by the fact that feed consumption is reduced in the high temperature environments. The report of Bray and Gesell (1961) suggests that egg production in various temperature environments will not differ if an adequate protein intake is maintained. In analyzing the situation, one must also consider the hormonal aspects. Thyroid activity has been shown to be closely related to egg production (Glick et al.,
1447
1959; and Sturkie, 1965). Therefore, increased egg production at the lower temperatures may be due to increased thyroid activity at these temperatures. Indeed, Glick et al. (1959) and Huston (1960) have shown that thyroids of chickens were larger at lower temperatures than at higher ones. A temperature-hormonal interaction has been further indicated because molting, which may be under progesterone and thyroid hormonal control (Sturkie, 1965), was found to be more prominent in the high temperature pens. Mueller (1961) suggested that constant high temperatures reduce egg shell thickness and egg weights in chickens. The present study indicated that egg weights but not shell thickness in turkeys are lowered by high constant temperatures. Species differences between turkeys and chickens may partially explain the differences in response found for shell thickness. It has been well documented that chickens under increasing temperatures lay thinner eggs [Warren and Schnepel (1940), Wilhelm (1940), Wilson (1949), Hutchinson (1953), Thornton and Moreng (1959) and Harrison and Biellier (1969)] and smaller eggs (Bennion and Warren, 1933; Bruckner, 1936; Lorenz and Almquist, 1936; Wilson, 1949; Mueller et al., 1951; Glick et al., 1959; Campos et al, 1960; Clark and Amin, 1965; and Lyle and Moreng, 1968). The results of the present experiment and of Marsden et al. (1966) showed no temperature effect on fertility or hatchability. These findings differ from those of Heywang (1944) and Glick et al. (1959). Since the latter two investigators were working with chickens, species differences may partially explain this contradiction. Another possible explanation for the different results is that they utilized natural matings while artificial insemination was used in the present experiment. It should be noted, however, that reports in which
1448
D. M. THOMASON, A. T. LEIGHTON, JR. AND J. P. MASON. JR.
artificial insemination of chickens was used are also contradictory. Wilson (1949) found no effects, while Wilson et al. (1957), Howes et al. (1961), and Clark and Sarakoon (1967) reported that temperature does affect fertility and hatchability. The feed consumption and body weight results as affected by temperature in the present study agree with the results of experiments in which chickens were the tested species (Bennion and Warren, 1933; Bruckner, 1936; Campos et al., 1960; and Mueller, 1961). Since hens exhibiting broody characteristics were observed to eat relatively little feed, increased broodiness, compounded the temperature effect. ACKNOWLEDGEMENT Sincere appreciation is expressed to the Virginia Agricultural Foundation which provided a grant-in-aid in partial support of this investigation. The authors wish also to acknowledge the invaluable aid given by Lee Roy Barnett, Farm Manager, and the employees of the Turkey Research Center at Virginia Polytechnic Institute and State University. REFERENCES Albright, W. P., and R. B. Thompson, 1933. Securing early turkeys by stimulated egg production. Poultry Sci. 12: 124-128. Asmundson, V. S., F. W. Lorenz and B. D. Moses, 1946. Influence of light intensity on ovulation in turkeys. Poultry Sci. 25: 346-354. Atkinson, R. L., J. W. Bradley, J. R. Couch and J. H. Quisenberry, 1967. The calcium requirement of breeder turkeys. Poultry Sci. 46: 207214. Bailey, B. B., J. H. Quisenberry and J. Taylor, 1959. A comparison of performance of layers in cage and floor housing. Poultry Sci. 38: 565568. Bennion, N. L., and D. C. Warren, 1933. Temperature and its effect on egg size in the domestic fowl. Poultry Sci. 12: 69-82. Biswas, D. K., and J. V. Craig, 1970. Genotypeenvironment interactions in chickens selected
for high and low social dominance. Poultry Sci. 49:681-692. Bray, D. J., and J. A. Gesell, 1961. Studies with corn-soya laying diets. 4. Environmental temperature-a factor affecting performance of pullets fed diets suboptimal in protein. Poultry Sci. 40: 1328-1335. Bruckner, J. H., 1936. The effect of environmental conditions on winter egg production. Poultry Sci. 15:417-418. Campos, A. C , F. H. Wilcox and C. S. Shaffner, 1960. The influence of fast and slow rises in ambient temperature on production traits and mortality of laying pullets. Poultry Sci. 39: 119-129. Clark, C. E., and M. Amin, 1965. The adaptability of chicken to various temperatures. Poultry Sci. 44: 1003-1009. Clark, C. E., and K. Sarakoon, 1967. Influence of ambient temperature on reproductive traits of male and female chickens. Poultry Sci. 46: 1093-1098. Dorminey, R. W., J. E. Parker and W. H. McCluskey, 1970. Effects of light intensity on leg horn pullets during the development and laying periods. Poultry Sci. 49: 1657-1661. Garland, F. W., Jr., R. C. Eaton, D. E. Greene, H. L. Wilcke and R. M. Bethke, 1961. Duration and intensity of light for out-of-season egg production in turkeys. Poultry Sci. 40: 1406. Glick, B., J. Griffin and A. van Tienhoven, 1959. Effect of environment on reproduction characters and endocrine organs of New Hampshire chickens. Poultry Sci. 38: 1078-1087. Gowe, R. S., 1955. A comparison of the egg production of seven White Leghorn strains housed in two environments-floor pens and a laying battery. Poultry Sci. 34: 1198. Harrison, P. C , and H. V. Biellier, 1969. Physiological response of domestic fowl to abrupt changes of ambient air temperature. Poultry Sci. 48: 1034-1045. Heywang, B. W., 1944. Fertility and hatchability when the environmental temperature of chickens is high. Poultry Sci. 23 : 334-339. Howes, J. R., W. Grub and C. A. Rollo, 1961. The effects of high constant environmental temperatures upon the duration of fertility. Poultry Sci. 40: 1416. Huston, T. M., 1960. The effects of high environmental temperatures upon blood constituents and thyroid activity of domestic fowl. Poultry Sci. 39: 1260. Hutchinson, J. C. D., 1953. Effect of hot climates on egg weight. Poultry Sci. 32: 692-690.
ENVIRONMENT AND T U R K E Y REPRODUCTIVE PERFORMANCE
Jones, D. G., and W. Kohlmeyer, 1947. The relationship of broodiness and pause to reproductive performance in turkeys. Poultry Sci. 26: 545. Kosin, I. L., M. S. Mitchell and W. T. Burrows, 1952. Influence of temperature on the reproductive performance of Broad Breasted Bronze toms. Poultry Sci. 3 1 : 180-182. Kosin, I. L., and M. S. Mitchell, 1955a. Ambient temperature as a factor in turkey reproduction. 1. The effect of preheating males and females on their subsequent breeding pen performance. Poultry Sci. 34: 484-496. Kosin, I. L., and M. S. Mitchell, 1955b. 2. The effect of artificially lowered air temperature on the breeding activity of males in late spring and summer. Poultry Sci. 34: 499-505. Logan, V. A., 1965. Influence of cage versus floor, density and dubbing on laying house performance. Poultry Sci. 44: 974-979. Lorenz, F. W., and H. J. Almquist, 1936. Seasonal variations in egg quality. Poultry Sci. 15: 1418. Lowry, D. C , I. M. Lerner and L. W. Taylor, 1956. Intra-flock genetic merit under floor and cage managements. Poultry Sci. 35: 1034-1043. Lyle, G. R., and R. E. Moreng, 1968. Elevated environmental temperature and duration of post exposure ascorbic acid administration. Poultry Sci. 47 : 410-417. Marsden, S. J., 1936. A study of egg production in bronze turkeys. Poultry Sci. 15: 439^45. Marsden, S. J., L. M. Lucas and S. P. Wilson, 1966. The influence of day length and environment on reproduction, broodiness, and mortality of turkeys. Poultry Sci. 45: 668-675. McCartney, M. G., 1956. Reproductive performance in broody and non-broody turkeys. Poultry Sci. 35: 763-765. Mitchell, M. S., and I. L. Kosin, 1954. The effect of controlled ambient temperature on some factors associated with egg laying in turkeys. Poultry Sci. 3 3 : 186-191. Mueller, W. J., 1961. The effect of constant and fluctuating environmental temperatures on the biological performance of laying pullets. Poultry Sci. 40: 1562-1571.
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Mueller, C. D., T. B. Avery, H. D. Smith and R. E. Clegg, 1951. Effects of controlled light and temperature for laying hens. Poultry Sci. 30: 679-686. Parker, J. E., 1947. The influence of season on reproduction in turkeys. Poultry Sci. 26: 118121. Parker, J. E., and O. A. Barton, 1945. Relation of broodiness to reproduction in turkey hens. N. Dak. Bimo. Bui. 8 ( 2 ) : 3-5. Shoffner, R. N., C. R. Polley, R. E. Burger and E. L. Johnson, 1962. Light regulation in turkey management. 2. Female reproductive performance. Poultry Sci. 4 1 : 1563-1570. Shupe, W. D., and J. H. Quisenberry, 1961. Effect of certain rearing and laying house environments on performance of incross egg production type pullets. Poultry Sci. 40: 1165-1171. Smyth, J. R., Jr., and A. T. Leighton, Jr., 1953. A study of certain factors affecting fertility in the turkey. Poultry Sci. 32: 1004-1013. Sturkie, 1965. Avian Physiology. Ithaca, New York: Comstock Publishing Associates, Cornell University Press. Thornton, P. A., and R. E. Moreng, 1959. Further evidence on the value of ascorbic acid for maintenance of shell quality in warm environmental temperature. Poultry Sci. 38: 594-599. Warren, D. C , and R. L. Schnepel, 1940. The effect of air temperatures on egg shell thickness in the fowl. Poultry Sci. 19: 67-72. Wilhelm, L. A., 1940. Some factors affecting variations in egg shell quality. Poultry Sci. 19: 246253. Wilson, W. O., 1949. High environmental temperatures as affecting the reaction of laying hens to iodized casein. Poultry Sci. 29: 581-592. Wilson, W. O., E. H. McNally and H. Ota, 1957. Temperature and calorimeter study on hens in individual cages. Poultry Sci. 36: 1254-1261. Wolford, J. H., and H. C. Zindel, 1970. Caged turkey breeder hens: shell quality versus oyster shell supplementation. Poultry Sci. 49: 814816. Woodard, A. E., H. Abplanalp and F. X. Ogasawara, 1961. Egg and semen production performance of turkeys under cage management. Poultry Sci. 49: 884-890.
APRIL 11-13, 1973. FACT FINDING CONFERENCE, POULTRY AND EGG INSTITUTE OF AMERICA. RIVERGATE EXHIBITION CENTER, NEW ORLEANS, LOUISIANA