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Reproductive Traits of First Eggs of Clutches Vs. Other Clutch Positions in Turkeys1
Reproductive Traits of First Eggs of Clutches Vs. Other Clutch Positions in Turkeys1 WAYNE L. BACON and KARL E. NESTOR Department of Poultry Science, Ohio Agricultural Research and Development Center, Wooster, Ohio 44691 (Received for publication March 16, 1978) ABSTRACT Reproductive traits were compared for first eggs of clutches (including single egg clutches) vs. eggs in all other clutch positions. Lower percent fertility, percent hatch of fertile eggs, percent hatch of all eggs, and higher percent 7-day dead embyros were associated with first eggs of clutches. No difference was found in percent 7 to 28 day dead embryos. INTRODUCTION The fertility of turkey eggs declines as the duration of the hatching season increases (Harper and Arscott, 1969). Egg production shows a similar decline, which indicates that later in the production season a greater percentage of eggs may be laid as first eggs of clutches or as single egg clutches. This paper reports observations on female reproductive traits, all relatively early in a production season, comparing first eggs of clutches (including single egg clutches) to eggs laid in all other positions in clutches. MATERIALS AND METHODS Fertility, hatchability (of fertile and of total eggs), 7-day dead germs, and 28-day dead germs were measured for first eggs of clutches (including single egg clutches) vs. all other eggs in multiple egg clutches during the fifth through twelfth weeks of a hatching season (beginning when hens first attained approximately 50% production). Data were obtained for 157 medium weight and 233 large weight hens from various lines described by Nestor (1977). The medium weight lines consisted of a randombred control population and sublines of the randombred control which were selected for increased egg production and high and low plasma level of corticosterone after cold stress. The large weight lines were a second randombred control line and sublines of this control selected for increased 16-week body weight, increased clutch length, decreased broodiness, increased fertility,
'Approved for publication as Journal Article No. 30—78 of the Ohio Agricultural Research and Development Center, Wooster, Ohio 44691. 1979 Poultry Sci 58:257-258
and high and low blood estrogen level at first eggA paired mating system was used for all lines (Nestor, 1977). Inseminations were made twice the first week after production of the first egg by the flock, and biweekly thereafter. In almost all cases the amount of semen inseminated was greater than .025 ml., with an upper limit of about .050 ml. First eggs of clutches (and single egg clutches were identified by the caretaker after examining the trapnest record by placing an X on these eggs as well as the hens 1 to 3 digit identification number. Thereafter all eggs were handled as usual at this station for pedigree hatching (Nestor, 1977). The hens were housed in floor pens (Nestor, 1977) under our normal operating procedures (Nestor, 1977). The lights (incandescent; average 100 lux intensity at bird height) came on at 0300 hr and the first collection of eggs started at 0700 hr. Collections of eggs were periodic throughout the day with the last collection initiated at 1630 hr. The lights went out at 1700 hr. For each hen, the average of the first egg of all clutches (including single egg clutches) was compared to the average for subsequent eggs of all clutches using a paired " t " test. RESULTS AND DISCUSSION Percent fertility was significantly lower in first eggs of clutches (including single egg clutches) than in eggs in other clutch positions in both the medium (P<.05) and heavy (P<.01) weight hens (Table 1). Fertility was determined by candling at 7 days, and no breakout of infertile eggs for macroscopic germinal disc examination was conducted. It is therefore possible
257
258
BACON AND NESTOR TABLE 1. Reproductive traits for medium and heavy weight groups of hens
Fertility
Hatch of fertile eggs
Hatch of all eggs
7-Day dead
embry os
7-28 Day dead embryos
U)
Medium weight 1st egg Other ta dfb
80.0 82.6 -2.1* 155
80.7 84.7 -2.7" 155
65.4 70.5 -3.6" 155
8.5 6.0 2.1* 155
10.0 8.9 .9 155
Heavy weight 1st egg Other ta dfb
78.1 80.7 -2.8" 231
78.0 82.3 -2.7" 231
62.5 67.6 -4.1" 231
9.4 6.2 3.5" 231
11.2 12.9 -1.3 231
"Student's" t test. Degrees of freedom for hens. *P<.05. "P<.01.
that some of the eggs classified as "infertile" were in fact very early dead, and thus fertile. This observation is in agreement with Kosin and Mun (1960) who reported that single egg clutches had lower fertility and hatchability than eggs in clutches of 2 to 5 eggs. Percent hatch of fertile eggs and percent hatch of all eggs (Table 1) were also lower (P<.01) in both the medium and heavy groups of hens, an observation which also agrees with Kosin and Mun (1960). The lower percent hatch of fertile eggs was associated with increased percent 7-day dead embryos in both the medium (P<.05) and heavy (P<.01) weight groups of hens. This indicates the lowered percent hatch of fertile eggs is associated with early rather than late incubation. ' Bacon and Cherms (1968) found that the interval from follicular maturation to oviposition ("rest") was greater in first eggs of clutches of up to 6 eggs than in subsequent eggs in these clutches. Middlekoop (1972) noted poor hatchability in chicken eggs (13 to 26%) with an extra deposit of shell calcium, or "held" eggs. At this station, the majority of eggs with an extra deposit of shell calcium are laid on the
floor, and are therefore not set or included in the present data. The data cited above indicate that the first eggs have a longer "rest" period or are possibly "held" longer than subsequent eggs in clutches. These observations may explain the lower percent hatch of all eggs and lower percent hatch of fertile eggs presently being reported in first eggs of clutches, including single egg clutches.
REFERENCES Bacon, W. L., and F. L. Cherms, 1968. Ovarian follicular growth and maturation in the domestic turkey. Poultry Sci. 47:1303-1314. Harper, J. A., and G. H. Arscott, 1969. Seasonal decline in fertility of turkey eggs. Poultry Sci. 48: 2109-2113. Kosin, I. L., and A. M. Mun, 1960. Clutch size, oviposition time, and "floor" eggs as factors in turkey hatchability. Poultry Sci. 39:82-92. Middlekoop, J. H., van, 1972. Hatching problems of hard-shelled eggs with additional shell deposition produced by broiler mothers. Arch Gefugelk. 36: 63-70. Nestor, K. E., 1977. The use of a paired mating system for the maintenance of experimental populations of turkeys. Poultry Sci. 56:60-65.
'Approved for publication as Journal Article No. 30—78 of the Ohio Agricultural Research and Development Center, Wooster, Ohio 44691. 1979 Poultry Sci 58:257-258
and high and low blood estrogen level at first eggA paired mating system was used for all lines (Nestor, 1977). Inseminations were made twice the first week after production of the first egg by the flock, and biweekly thereafter. In almost all cases the amount of semen inseminated was greater than .025 ml., with an upper limit of about .050 ml. First eggs of clutches (and single egg clutches were identified by the caretaker after examining the trapnest record by placing an X on these eggs as well as the hens 1 to 3 digit identification number. Thereafter all eggs were handled as usual at this station for pedigree hatching (Nestor, 1977). The hens were housed in floor pens (Nestor, 1977) under our normal operating procedures (Nestor, 1977). The lights (incandescent; average 100 lux intensity at bird height) came on at 0300 hr and the first collection of eggs started at 0700 hr. Collections of eggs were periodic throughout the day with the last collection initiated at 1630 hr. The lights went out at 1700 hr. For each hen, the average of the first egg of all clutches (including single egg clutches) was compared to the average for subsequent eggs of all clutches using a paired " t " test. RESULTS AND DISCUSSION Percent fertility was significantly lower in first eggs of clutches (including single egg clutches) than in eggs in other clutch positions in both the medium (P<.05) and heavy (P<.01) weight hens (Table 1). Fertility was determined by candling at 7 days, and no breakout of infertile eggs for macroscopic germinal disc examination was conducted. It is therefore possible
257
258
BACON AND NESTOR TABLE 1. Reproductive traits for medium and heavy weight groups of hens
Fertility
Hatch of fertile eggs
Hatch of all eggs
7-Day dead
embry os
7-28 Day dead embryos
U)
Medium weight 1st egg Other ta dfb
80.0 82.6 -2.1* 155
80.7 84.7 -2.7" 155
65.4 70.5 -3.6" 155
8.5 6.0 2.1* 155
10.0 8.9 .9 155
Heavy weight 1st egg Other ta dfb
78.1 80.7 -2.8" 231
78.0 82.3 -2.7" 231
62.5 67.6 -4.1" 231
9.4 6.2 3.5" 231
11.2 12.9 -1.3 231
"Student's" t test. Degrees of freedom for hens. *P<.05. "P<.01.
that some of the eggs classified as "infertile" were in fact very early dead, and thus fertile. This observation is in agreement with Kosin and Mun (1960) who reported that single egg clutches had lower fertility and hatchability than eggs in clutches of 2 to 5 eggs. Percent hatch of fertile eggs and percent hatch of all eggs (Table 1) were also lower (P<.01) in both the medium and heavy groups of hens, an observation which also agrees with Kosin and Mun (1960). The lower percent hatch of fertile eggs was associated with increased percent 7-day dead embryos in both the medium (P<.05) and heavy (P<.01) weight groups of hens. This indicates the lowered percent hatch of fertile eggs is associated with early rather than late incubation. ' Bacon and Cherms (1968) found that the interval from follicular maturation to oviposition ("rest") was greater in first eggs of clutches of up to 6 eggs than in subsequent eggs in these clutches. Middlekoop (1972) noted poor hatchability in chicken eggs (13 to 26%) with an extra deposit of shell calcium, or "held" eggs. At this station, the majority of eggs with an extra deposit of shell calcium are laid on the
floor, and are therefore not set or included in the present data. The data cited above indicate that the first eggs have a longer "rest" period or are possibly "held" longer than subsequent eggs in clutches. These observations may explain the lower percent hatch of all eggs and lower percent hatch of fertile eggs presently being reported in first eggs of clutches, including single egg clutches.
REFERENCES Bacon, W. L., and F. L. Cherms, 1968. Ovarian follicular growth and maturation in the domestic turkey. Poultry Sci. 47:1303-1314. Harper, J. A., and G. H. Arscott, 1969. Seasonal decline in fertility of turkey eggs. Poultry Sci. 48: 2109-2113. Kosin, I. L., and A. M. Mun, 1960. Clutch size, oviposition time, and "floor" eggs as factors in turkey hatchability. Poultry Sci. 39:82-92. Middlekoop, J. H., van, 1972. Hatching problems of hard-shelled eggs with additional shell deposition produced by broiler mothers. Arch Gefugelk. 36: 63-70. Nestor, K. E., 1977. The use of a paired mating system for the maintenance of experimental populations of turkeys. Poultry Sci. 56:60-65.