Mating behavior in commercial broiler breeders: Female effects
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©2010 Poultry Science Association, Inc.
Mating behavior in commercial broiler breeders:
Female effects
J. R. Moyle, D. E. Yoho, R. S. Harper, and R. K. Bramwell1
Department of Poultry Science, University of Arkansas, Fayetteville 72701
Primary Audience: Broiler Breeder Managers, Flock Supervisors, Researchers
SUMMARY
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Commercial broiler breeder managers have reported differences in fertility among strains of
birds, with the assumption that less feathering on the backs of hens results from more frequent
mating. To determine if mating frequency is associated with back feathering, a study was under-
taken to compare the mating behavior of 2 different lines of broiler breeder hens housed with a
single strain of roosters. Each pen used in this study contained between 80 and 85 hens and 9
males. Mating behavior activities recorded included aggression, neck flares, male approaches,
male waltzes, hen crouches, attempted mounts, completed mounts, attempted matings, and
completed matings. Mating observations took place in the evening because this was the most
active time for mating. Perivitelline layer sperm penetration, fertility, and hatchability were de-
termined on eggs collected at each observation period. The hen strain with greater feather loss
had fewer mounts by males as well as fewer completed matings, indicating that feather loss is
not necessarily a good indicator of mating activity and, in fact, that it may deter such behavior.
Sperm penetration, fertility, and hatchability were not different between the hen lines. In con-
clusion, although mating behavior varies in some genetic strains of broiler breeders, it does not
fully explain the differences in feather loss, indicating that feather loss on the backs of hens is
not a good indicator of mating activity. Furthermore, even though mating activity varied in the
2 hen strains, it did not result in differences in fertility.
Key words: mating behavior, broiler breeder, hatch
2010 J. Appl. Poult. Res. 19:24–29
doi:10.3382/japr.2009-00061
INTRODUCTION factors play a role in broiler breeder fertility, in-
In the broiler breeder industry, it has long cluding the physical condition of the birds [2, 3],
been assumed that hens with more feather loss the ratio of males to females [4], nutrition, the
on their backs are mating more frequently than growth curve, and environmental factors such as
hens with less feather loss. Jones and Prescott disease and temperature [5]. Siegel [6] observed
[1] proposed that hens with less feather cover- a negative relationship between breast yield and
ing may be those that more readily acquiesce to fertility, whereas Hocking and Duff [7] found
males for mating. Thus, it is assumed that hens that a decline in fertility was caused by a reduc-
with more feather loss, particularly as they age, tion of overall reproductive fitness. Bowling et
will have higher fertility than hens with more al. [3] also reported a negative relationship be-
feather covering on their backs. Many known tween sperm mobility and BW.
1
Corresponding author: bramwell@uark.eduMoyle et al.: MATING BEHAVIOR IN BROILER BREEDERS 25
A study was initiated to determine if a dif- tained throughout production. New spare or re-
ference in mating behavior and fertility existed placement males were not introduced during the
between 2 strains of broiler breeder hens when observation periods. A total of 216 males and
a single male strain was used. This study was approximately 2,000 hens were observed during
undertaken when it was noticed in commercial the study. Mating activity was observed hourly
flocks that strain 1 (S1) hens had fewer feath- throughout the day, and it was determined that
ers on their backs than strain 2 (S2) hens, with mating activity peaked in the evening hours. The
the actual cause of this difference not known. results of these observations are consistent with
It was therefore postulated that greater mating the findings of other authors [10–13]. Therefore,
activity in S1 hens caused the increased feather all observations for this study were made in 1-h
loss. It was further postulated that if the S1 hens periods from 1800 to 1900 h, which was 14 to 15
mated more frequently, they would have higher h after the onset of light (16.75L:7.15D).
fertility and greater sperm activity at the site of A total of 15 paired observations were made,
fertilization. Bramwell et al. [8, 9] reported that with the same individual observing a pair of
increased mating activity and increased num- adjoining pens containing the same male strain
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bers of sperm inseminated result in increased housed with 1 of 2 hen strains. All observations
sperm penetration of the perivitelline layer (PL) were made during a 14-d period of time. Hens
and increased fertility. Therefore, this study was were 49 wk old at the beginning of the trial.
conducted to evaluate actual mating activity and Males were maintained with the same line of
the behavioral patterns of broiler breeder males hens for the duration of the trial. All males used
when housed with 2 different hen strains, as well were of the same strain and age and were reared
as their fertility and PL sperm penetration val- sex separate at the same facility as the hens so
ues. that any difference in mating behavior could be
attributed to the hens. Both female strains were
MATERIALS AND METHODS reared in the same facility and were reared to
meet recommended BW.
All observations took place at the University At the conclusion of all the observation peri-
of Arkansas Broiler Breeder Research Farm. ods, eggs were sent to a commercial hatchery by
This project complied with the provisions of hen strain group to determine fertility, hatchabil-
the Institute Animal Care and Use Committee ity, and embryo livability through embryo diag-
as specified by the Animal and Plant Health nosis of unhatched eggs. Additionally, 2 random
Inspection Service, USDA, in 9 CFR Part samples of eggs (n = 120) were collected from
1(1–91). Birds used in this trial were housed in each hen strain and subjected to the sperm pen-
a production facility that contained 48 experi- etration assay procedure to determine the PL
mental and 5 spare pens measuring 4.3 m2 (14 sperm penetration rates [8, 9].
ft2). The birds were reared on the research farm Sperm penetration assays was performed us-
in a separate pullet-rearing facility according to ing the technique described by Bramwell et al.
industry standards and were housed in the pro- [8] to determine fertility because the number of
duction house at 21 wk of age, at which time holes has been shown to be closely correlated
the males and females were commingled. Each with fertility [8, 9]. Initially 120 eggs per treat-
pen observed contained between 80 and 85 hens ment were used; however, some data were not
and 9 males. Although this female-to-male ra- obtained because the PL tore or egg yolks broke
tio (9:1) may by lower than that recommended before the PL could be removed.
by the primary breeder, our past experience has Breakout analysis was performed on a mini-
shown that in pen trials, more males are needed mum of 770 eggs per treatment. Early dead em-
to obtain adequate fertility. Each pen contained bryos were those that died before 8 d of incu-
separate feeders for the males and females to bation. Those that died between 8 and 14 d of
control BW, water was provided ad libitum, and incubation were classified as midterm deaths,
nests were provided to facilitate egg collection. and those that died after d 14 were recorded as
Spare males were housed in the same facility late dead embryos. Fertility was also evaluated
so that a constant number of males were main- at the time of breakout.26 JAPR: Research Report
Table 1. Results from the observation of mating behavior1
Item M-F MW HC AM CM ATM SM
Strain
1 7.73 0.47 1.67 12.00 8.40a 7.93a 6.26a
2 5.07 0.33 3.60 16.07 12.60b 11.13b 9.26b
P-value 0.1569 0.6615 0.1069 0.0562 0.0023 0.0145 0.0120
a,b
Means within a column with different superscripts within a column differ significantly (P < 0.05).
1
M-F = male-hen aggression (male aggression not directly related to mating activity); MW = male waltz (dancing around or up
to the hen in a courting manner); HC = hen crouch (when a hen crouches to the ground with wings at the shoulder elevated in
an attempt to allow the rooster to mount); AM = attempted mounts (when a male makes an attempt to mount the hen for mating
purposes); CM = completed mounts (when the male obtains a position on top of the hen); ATM = attempted mating (when a
male mounts and tries to mate the hen); SM = successful mating (when a male makes cloacal contact with a hen). The results
are reported as number of observations per hour.
Characteristics observed were male-male sulted in the male obtaining a position on top
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aggression, male-hen aggression, hen-hen ag- of the female where mating activity could occur.
gression, male waltzes, hen crouches, attempted Unsuccessful matings after a successful mount
hen mounts, completed hen mounts, attempted occurred as a result of balance lost by the male
hen matings, and completed hen matings. Male- during the act of copulation, by aggression by
male aggression included fighting, aggressively other males, causing the male mounted atop the
pecking the head of another male, or disrupting female to lose his position, or by the male appar-
the mating action of another male. Male-hen ag- ently losing interest and voluntarily dismounting
gression included aggressive attacks to the head after mounting the female and gaining a mating
or body of a hen in such a way as not to be as- position.
sociated with an attempted mating, or when the Attempted matings were recorded each time
male attacked the hen in an aggressive way and a male had successfully mounted the female and
tried to force the female into mating. Hen-hen then made an actual attempt to complete the
aggression included any aggressive confronta- mating process through copulation. The caus-
tion and pecking. ative factors for incomplete matings after an
Incidence of a male waltz was the approach initial attempt are similar to those listed in the
of a male to a female while the male dropped a previous paragraph. Successful matings were
wing to the ground and performing a semicircu- recorded as the number of times males success-
lar movement around the hen in a courting man- fully completed copulations (i.e, a male made
ner [14, 15]. This type of courtship behavior is contact with the cloaca of the female). From this
commonly observed among feral or backyard- contact, it was assumed that ejaculation took
type domestic chickens, in which courtship of place and that semen was transferred. Each of
the hens is more common [1]. In broiler breed- the previous events that occurred was recorded
ers, this behavior is seen less often and may not
be exhibited as vigorously. Hen crouches were
recorded when a hen crouched to the ground Table 2. Sperm penetration analysis on 2 random
with wings at the shoulder, elevated in an at- samples of eggs (n = 120 per treatment) from strain
tempt to allow the rooster to mount for mating 1 (S1) and strain 2 (S2) hens taken at the time of
activity. Hen crouches were recorded only if the observations1
crouch was independent of male mating activity Holes, no. S1, % S2, %
and not after the male had attempted to mount
0–10 1.6 2.5
the hen. 11–30 3.2 2.5
Attempted mounts were recorded when a 31–60 4.8 5.0
male made an attempt to mount the female for 61–100 17.7 20.0
mating purposes, usually including grabbing the 100+ 72.6 70.0
female at the back of the neck behind the head 1
None of these treatment means are significantly different
or comb. Completed mounts were those that re- (P > 0.05).Moyle et al.: MATING BEHAVIOR IN BROILER BREEDERS 27
Table 3. Results of embryonic breakout from the study (n > 720 per treatment)1
Strain Fertile, % Hatch, % Early, % Mid, % Late, %
a
1 96.25 86.25 7.27 0.20 6.73
2 96.39 85.28 7.80 1.40b 6.80
a,b
Means with different superscripts differ significantly (P < 0.05).
1
Early = number of dead embryos between d 1 and 7; mid = number of embryos that died between d 8 and 15; late = number
that died after d 15, including those that pipped.
independently of other events that occurred in because of sexual rejection by the hens, or the
the process. increased aggression may have been an attempt
All data collected were evaluated by ANOVA at intimidating the hens into mating. This ag-
using JMP statistical software, and means were gressive behavior had been noticed in field
compared using the LSD method [16]. Differ- studies conducted by researchers at the Univer-
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ences were deemed to be significant when the sity of Arkansas (unpublished data). When the
P-value was less than 0.05. males matured more quickly than the females,
they became more aggressive and attacked the
RESULTS AND DISCUSSION females. This aberrant behavior occasionally led
to forced copulations. Millman et al. [18] report-
The results of the behavioral observations ed that male broiler breeders displayed a greater
from this study are shown in Table 1 and are re- than normal aggression toward females and that
ported as the number of observations per hour. it could lead to injuries to the females. At the
The S2 hens were mounted, attempted to mate, time of the study, males attempted to mount the
and mated more frequently than the S1 hens. S1 females less frequently but did tend to peck
The S2 hens may have been more receptive to aggressively at the S1 females more often. This,
males, or males may have responded more read- however, would not account for the feather loss
ily to hen signals or cues or were simply more on the backs of the females. We have observed
interested in these hens, and the hens were there- male aggression toward females peaking at ap-
fore mated more often than S1 hens. Marin and proximately 28 wk of age and then declining
Satterlee [17] found that males mated more of- rapidly thereafter (unpublished data). Therefore,
ten with hens that had been selected for low lev- previous injury to the hens would have taken
els of stress compared with hens that had high place 20 wk before the observation and the fe-
levels of stress. Therefore, it may be that the S2 males would have had time to recover.
hens had inadvertently been selected for some Table 2 contains the results of the PL sperm
other traits or other characteristics that the males penetration analysis performed on samples of
preferred that were undetectable to the human eggs laid by both strains of hens [8, 9]. There
eye. This is in line with observations by industry were no differences in the percentages for each
personnel who have reported that S2 birds are category. Results showed both strains to have
better adapted to varied environments than S1 very good sperm activity at the site of fertil-
birds. Therefore, the increased loss of feathers ization. Although the S1 hens were mated less
in the S1 hens was not a result of more frequent frequently than the S2 hens, they were able to
mating or mating behavior and must therefore be maintain PL sperm penetration values as high as
attributed to some other factor. Feather loss may those of S2 birds. Brillard and Bakst [19] report-
be genetic, the feather strength of the S1 hens ed a strong correlation between the number of
may be inferior to that of the S2 hens, or the S1 sperm in the sperm storage tubules and the holes
hems may simply be less densely feathered. in the PL. Therefore, a possible explanation for
Although not statistically significant, there the higher than expected sperm activity at the
was a trend (P = 0.16) for more male-female site of fertilization is that the S1 hens were able
aggression from the males housed with the S1 to store sperm for a longer duration [20] or that
hens (Table 1). The trend toward increased ag- they had a greater capacity for oviductal sperm
gression appeared to be caused by frustration storage. Last, there is also the possibility that28 JAPR: Research Report
a difference existed between the strains of fe- 4. The role of the hens is often overlooked
males in their physiological ability to select and when searching for reasons for low fer-
transport sperm [21]. If sperm in S1 hens had tility in broiler breeders, and this needs
increased selection and transport, then S1 hens to be investigated more thoroughly.
would need to be mated less frequently than the
S2 hens. The question may then arise whether REFERENCES AND NOTES
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