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THE ROLE OF PHEROMONES IN ANIMAL REPRODUCTION – A REVIEW

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Abstract

The pheromones play an important role in animal behavior and reproductive processes. Pheromones in the urine, feces, or from cutaneous glands can be perceived through the olfactory system to elicit both behavioral and endocrine responses in various species. These can exert profound effects on reproductive activity via the hypothalamic system that generates pulses of gonadotropin-releasing hormone. The role of pheromones in bovine reproduction is not as clearly defined as that in other species such as sheep, goats and swine. The knowledge acquired on the effectiveness of biostimulation; the factor which conditions it and the biological mechanism which produces it in livestock species, allows its use as a breeding management tool. The biostimulation technique through pheromones, offers a practical way to improve reproductive efficiency of the domestic animals by enhancing early onset of puberty and reducing postpartum anestrus period. However, the exact nature of the cues and the role of biostimulation in livestock species especially swine, sheep, goats and cattle require more attention.
THE ROLE OF PHERO MONES IN AN I MAL RE PRO DUC TION – A RE VIEW
A.A. Wani1, S.S. Dhindsa2, T.A. Shafi3, S.R.A. Chowdhary4 and Balwinder Kumar5
1De part ment of Vet er i nary Gy nae col ogy and Ob stet rics, 2, 5De part ment of An i mal Ge net ics and Breed ing,
3De part ment of Vet er i nary Med i cine, 4De part ment of Vet er i nary Phys i ol ogy and Bio chem is try,
Guru Angad Dev Vet er i nary and An i mal Sci ences Uni ver sity, Ludhiana-141004, Punjab, In dia.
Email : shahbazdhindsa76@ya hoo.co.in
ABSTRACT
The pheromones play an important role in animal behavior and reproductive processes.
Pheromones in the urine, feces, or from cutaneous glands can be perceived through the olfactory
system to elicit both behavioral and endocrine responses in various species. These can exert
profound effects on reproductive activity via the hypothalamic system that generates pulses of
gonadotropin-releasing hormone. The role of pheromones in bovine reproduction is not as clearly
defined as that in other species such as sheep, goats and swine. The knowledge acquired on the
effectiveness of biostimulation; the factor which conditions it and the biological mechanism which
produces it in livestock species, allows its use as a breeding management tool. The biostimulation
technique through pheromones, offers a practical way to improve reproductive efficiency of the
domestic animals by enhancing early onset of puberty and reducing postpartum anestrus period.
However, the exact nature of the cues and the role of biostimulation in livestock species especially
swine, sheep, goats and cattle require more attention.
Key Words : Biostimulation, bovine, goat, pheromones, pig, sheep, vomero-nasal or gan.
Animals from same species communicate information
concerning reproduction with each other in order to
co-ordinate reproductive activities. The term
Pheromone was coined by Karlson and Luscher and
the name of first pheromone was proposed as
Bombykal extracted from Honey Bee (Karlson and
Luscher 1959). It is a biologically active substance like
hormone, air borne chemical substance secreted
externally in urine, feces, or by sub-cutaneous glands
and cause specific reactions in a receiving animal. It
causes release of a specific behavior or physiological
changes in recipient’s endocrine or reproductive
system (Izard 1983). Exteroceptive cues that are likely
to play role in male and female interactions include
olfactory, visual, auditory and tactic stimuli (Zalesky et
al., 1984). Extensive studies in insects, rodents, swine,
sheep, goats and cattle have established the
importance of pheromones in the strong influence
exerted by the male on reproductive activity in the
female. It has been demonstrated that the urine of male
mice, rats, feral species and other wild rodents contains
a priming pheromone that is responsible for hastening
puberty in the females. Pheromones in the wool, wax
and urine of a ram are sufficient to stimulate ewes to
ovulate, while the buck has a strong characteristic
seasonal odor. The mere presence of the boar at the
time of insemination of the sow improves sperm
transport and ovulation, while the presence of the
vasectomised bull has been reported to hasten the
onset of puberty in heifers and also early resumption of
ovarian activity in cattle following parturition.
Types of Pheromones
Releaser pheromones
These pheromones elicit an immediate behavioral
response. In the pig, the male stimulates the
immobilization reflex of the sow by using sex
pheromones contained in its saliva. These
pheromones were identified as the steroids
5á-androst-16-en-3-one and 5á- androst-16-en-3á-ol
(Patterson 1966, Patterson 1968), which are
synthesized in the testes and released in boar saliva.
Primer pheromones
These pheromones mediate slow developing and
longer-lasting changes to the endocrine state or
development. In domestic mammals, especially small
ruminants, priming pheromones from the male seems
to have an influence on the induction of puberty, the
termination of seasonal anestrus and shortening of
postpartum anestrus (Gelez and Fabre-Nys 2004).
Pro gres sive Re search 8 (1) : 14-18 (2013) So ci ety for Sci. Dev. in Agric. and Tech.
Signaler pheromones
These pheromones convey the information about the
sender, such as individual or group identity, which are
important for parent-offspring recognition and mate
choice (Pageat and Gaultier 2003, Yamazaki et al.,
2000).
Major urinary proteins (MUPs) and Odorant binding
protein (OBPs)
Major urinary proteins (MUPs) and á2u proteins are
lipocalins that were first described in mouse and rat,
which are synthesized in the liver and excreted in the
urine (Shaw et al., 1983). Their roles are : (1) To
transport the pheromone in biological fluids, (2) To
extend the period of bioavailability of the pheromone by
delaying its liberation, and (3) To modulate the
pheromone activity (Hurst and Beynon 2004). The
odorant binding protein (OBPs) discovered in the nasal
tissues of several vertebrates have strong similarity with
MUPs (Cavaggioni et al., 1987).
Biostimulation in Various Species
Dog and cat
The Perception of pheromones in dog is via vomero
nasal organ (VNO). There are two VNOs situated on
each side of the nasal septum in small fossa. Each VNO
is 4 cm long in the dog (Wada et al., 1991). The suction
of pheromones by VNO follows the flehman or similar
behaviour (raising/movement of upper lip, half open
mouth and movements of the tongue) in dairy animals.
In dog flehman is controversial but shows analogous
behaviour that is panting, raising of upper lip, creasing
the nose or flecking the tongue against papilla.
The expression of flehman induces aspiration of
pheromone into the VNO, where it is mixed with the
mucus. This suction occurs because of vasoconstric-
tion in the wall of the VNO. This increases the diameter
of the lumen of organ and thus creates the fall in
pressure necessary for the suction. The components of
pheromone bind with the pheromone binding proteins
and so can stimulate the receptors located on
membrane of sensory cells (Pageat and Gaultier 2003).
After the suction period the wash out of the VNO
begins. The blood pressure increases and the diameter
of the VNO lumen decreases, thus expelling the mucus.
In cat, five different facial pheromones named F1
to F5 have been isolated from the sebaceous
secretions of cheeks and out of these five types, F2
(Composition: oleic acid, palmitic acid, propanoic acid
and p-hydroxy phenyl acetic acid) has been found to
be involved in sexual marking (MacDonald 1985).
During sexual behaviour male rubs his nose to some
points, around the place where he is with the female
cat and deposits the F2 pheromone. This pheromone
seems to improve the efficiency of sexual display
(Pageat and Gaultier 2003). In the peri-anal area, the
supra-caudal glands are well developed especially in
cat. These consist of high concentration of sebaceous
glands located at the dorsal aspect of the root of tail
(Mac Donald 1985). The sebaceous activity of these
glands is increased during spermatogenesis. Thus,
this secretion is involved in the stimulation of bitch
during sexual display (Pageat and Gaultier 2003). The
circumanal glands include the sebaceous and
modified sweat glands that are disseminated all
around the anus. These glands of male dogs are more
developed and their size increases with age. During
estrus, these glands produce tri-methyl amine rich
secretions in bitches that are highly attractive to male
dogs (Donovan 1969). In bitches during estrus, a
secretion of methyl-dihydroxy benzoate seems to be
highly attractive to male dogs and enhances sexual
excitement. It is interesting to note that this compound
is commonly used as a preservative in many human
cosmetic products. It could be involved in some sexual
behaviour shown by some dogs towards their owners
(Pageat and Gaultier 2003).
Pig
One of the mammalian species in which puberty in
females has been shown to be accelerated by the
presence of the male is the domestic pig. Gilts reared
in confinement that were exposed to a boar reached
puberty at an earlier age than gilts reared without being
exposed to a boar (Books and Cole 1970). The
presence of boars reduces the age of onset of puberty
in gilts and postpartum period in lactating sows
(Kirkwood et al., 1981). The presence of a boar can
accelerate puberty in gilts by about 30 days and also
introduction of boars to gilts at about 190 days of age
(i.e. mean age at puberty) can lead to a marked
The role of pheromones in animal reproduction—A Review 15
synchrony in attainment of the pubertal estrus (Books
and Cole 1970).
The sensory cues involved in the boar’s effect on
puberty are thought to be olfactory cues and that
exposing the gilts to a pen previously occupied by a
boar and presumably permeated with his odor was
effective in inducing early puberty (Signoret and
Lindsay 1982) Apparently, priming pheromones
remaining in the boar’s pen after his removal are
sufficient to induce early puberty. Boar’s presence
provides enough stimulation to overcome some of the
adverse effects of confinement on puberty, lowering
the age at first farrowing, thereby increasing lifetime
productivity (Thomson and Savege). Gilts reaching
early puberty through boar contact have higher
ovulation rates, more estrous cycles therefore higher
reproductive potential than controls (Izard 1983).
Sows go through a period of postpartum anoestrus,
the cause of which is thought to be inhibition of the
synthesis of Luteinizing Hormone (LH) and release of
Follicle Stimulating Hormone (FSH) via the suckling
stimulus. Some researchers have been successful in
reliably inducing estrus in lactating sows by grouping
sows with their litters in the presence of a boar (Izard
1983). Specific boar stimuli are known to be of
importance for the onset of estrus in sows after
weaning (Hughes et al. 1990). It is known that specific
boar stimuli at or around the moment of insemination
can influence reproductive processes such as sperm
transport and ovulation processes and consequently
affect reproductive performance (Soede 1993). This is
an essential management practice in systems of
production that rely on rebreeding at lactation estrus
for efficient operation (Izard 1983). It has also been
hypothesized that the presence of the boar increases
levels of pituitary FSH in lactation and that these
higher FSH at weaning provoke a more rapid onset of
estrus and ovulation. There is a possibility that a
priming pheromone (5á-androstenone) produced by
the boar could shorten the interval between weaning
and breeding (Izard 1983).
Age of the boar has been determined to have an
effect on inducing onset of puberty. Gilts exposed to
either 2 year-old or 11 month-old boars attained
puberty 24 days earlier than gilts exposed to boars
that were 6.5 months of age (Kirkwood et al., 1981).
The inability of young boars to advance puberty in gilts
has been attributed to a lack of production of the
priming pheromone or to a decreased ability to produce
the pheromone as compared to the older boars. There
are age differences in the ability of boars to produce the
gonadal 19-carbon steroids 5á-androstenone and
3á-androstenol (Booth, 1975), as well as age
differences in the morphological and biochemical
development of the sub-maxillary salivary gland from
which priming pheromones are released (Izard 1983).
The primary mechanism initiating onset of puberty in
gilts seems to be the production or release
of pheromone(s) from the boar, which is (are) secreted
in saliva from the sub-mandibular salivary gland
(Kirkwood et al., 1981).
Sheep and goat
Priming pheromones from the ram and buck have been
found to hasten the onset of puberty and estrus in sheep
and goats. “The ram effect” (priming pheromones) has
been reported to accelerate onset of estrus activity and
promote varying degree of estrus synchronization. The
introduction of males before the normal breeding season
hastens the onset of estrus cycle in seasonally anestrus
ewes (Knight et al., 1978). The stimulated ovulation in
ewes following ram introduction were preceded by LH
peaks. This change through olfaction would, suggest the
involvement of the VNO (which has neural connections
with the hypothalamus and is thought to be a mediator of
effects of priming pheromones that influence ovarian
function).
Physical or visual contact may not be necessary for
the ram to induce estrus in ewe. Knight and Lynch
(1980) tested the capacity of ram urine or a combination
of wax, collected from around the eyes and from the
flanks of ram and wool to induce ovulation in ewes early
in breeding season. Urine, wax and wool were as
effective as contact with rams. Similarly, the introduction
of a buck to a group of does resulted in initiation of
synchronized estrus, 5-10 days after onset of exposure
to the buck (Shelton 1960).
Bovine
The role of priming pheromones in bovine reproduction
is not as clearly defined as in sheep, goat and swine
(Robertson et al., 1991). While there are reports
supporting the evidence of priming pheromones or
16 Wani, et al.,
biostimulation in cattle, e.g. the presence of teaser bull
did not hasten puberty in a group of prepubertal heifers
(Berardinelli et al., 1978). Similarly, Wehrman et al.,
(1996) observed that incidence of precocious puberty
in developing beef heifers was not affected by the
presence of bulls. However, it has been reported that
67 per cent of heifers exposed to bull urine (by
oro-nasal treatment i.e. 1 ml of bull urine in each nostril
and 1 ml in oral cavity) and 32 per cent of heifers
exposed to only water attained puberty, supporting the
hypothesis that bull urine contains a priming
pheromone that hastens the onset of puberty in heifers
(Izard and Vandenbargh 1982). Similarly, Robertson et
al., (1991) supported the hypothesis that social
interactions between bulls and prepubertal heifers
results in a decreased age of attainment of puberty. In
another study, it was observed that heifers exposed to
vasectomised bulls attained puberty at 23.1 months,
significantly lower than the age of 26.4 months at onset
of puberty for the non exposed heifers (Rekwot et al.,
2000). The duration of post-partum anestrous in
multiparous cows decreased when cows were exposed
to bulls following parturition (Zalesky et al., 1984). After
bull exposure, interval to estrus was shorter than for
cows isolated from bulls and greater proportion of cows
exhibited estrus by 60-90 days after calving (Custer et
al., 1990). In this study, an increase in progesterone
concentration was observed before first estrus,
whereas LH was not altered by bull exposure
speculating that pre-estrus progesterone rise
associated with bull exposure may be the mechanism
of “bull effect” in postpartum cows. But this does not
preclude the probability that the effect of bull on
resumption of cyclicity is mediated via CNS by
stimulating LH release immediately following exposure.
Acosta et al., (1983) hypothesized that the “bull effect”
acts to increase the sensitivity of the positive feed back
centre for LH release in the hypothalamus to estrogen,
thus overriding inhibitory effects of low concentration of
estrogen on the hypothalamus. Another possible
explanation for this effect may be that stimulus from the
bulls acted directly to alter sensitivity of the ovary to LH
by increasing the number of LH receptors (Custer et al.,
1990).
It seems that cows of average body condition at
calving respond to the presence of bull by having a
shorter duration of postpartum anestrous than they
would have if they were isolated from bulls (Monje et
al., 1983 and Stumpf et al., 1987). Stumpf et al., (1987)
presumed that the presence of bulls stimulated
secretion of LH- releasing hormone in cows of
moderate body conditions.
In conclusion, biostimulation or pheromonal
communication plays an important role in mammalian
reproduction. The role of pheromones in bovine
reproduction is not as clearly defined as that in other
species, possibly due to nutritional and other
environmental stresses. The economic benefits of
using biostimulation through pheromones to enhance
early onset of puberty and the significant reduction of
postpartum anestrus period in domestic animals, may
serve as a management tool in tropical areas, where
livestock production has some constraints.
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(Abstract).
18 Wani, et al.,
... These pheromones can stimulate the production of oestrogen and progesterone, leading to estrus (either inducing or inhibiting), pregnancy termination, and the regulation of sexual maturation cycles (Meghna 2024). Unlike releaser pheromones, the priming pheromones have a slower onset but a longer duration of effect (Wani et al. 2013). They modulate physiological processes by either inhibiting or stimulating various endocrine, reproductive, and other bodily systems (Kekan et al. 2017). ...
... In these species, the exposure of anestrus females to sexually active males stimulates luteinizing hormone (LH) secretion and synchronized ovulation. This effect is mediated by olfactory cues, likely involving the vomeronasal organ (VNO), which is connected to the hypothalamus and plays a crucial role in reproductive regulation (Wani et al. 2013). ...
... Gilts that experience early puberty through boar contact tend to have higher ovulation rates and more estrous cycles, thus higher reproductive potential (Izard 1983). The presence of a boar during the insemination of a sow enhances sperm transport and ovulation (Wani et al. 2013). ...
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... In the pig, the male stimulates the immobilization reflex of the sow by using sex pheromones contained in its saliva. These pheromones were identified as the steroids 5-androst-16-en-3-one and 5-androst-16en-3-ol (Patterson 1966, Patterson 1968), which are synthesized in the testes and released in boar saliva (Wani et al 2013). ...
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... Detailed studies of pheromones in goats, sheep, cattle, pigs, insects and rodents have shown that male pheromones have a significant effect on reproductive activity in females [8]. In addition, it has been reported that in sheep and goats, the male effect is more than a pheromone-triggered response, and is a multifaceted process involving sociosexual signals provided by men [9]. ...
... cated at the base of the nasal septum (Vanderburgh, 2008 ;Haga et. al., 2010). Examples of pheromones are copulin in vaginal secretions which attract males (Grammer et. al., 2004), androgen-like substances in male mice urine affects female mice estrus cycles (Haga et. al., 2010) and androstenol and androstenone in the saliva of boars attracts sows (Wani et. al., 2013). Pheromone elements in mice include both volatile organic compounds and non-volatile proteins, such as exocrine gland-secreted peptide 1 (ESP1), which is secreted by tear glands (Bind et. al., 2013) and darcin (MUP20), a member of the major urinary proteins (MUPs) (Roberts et. al., 2010). ...
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Introduction: Pheromones are chemicals produced by an animal that affects the behavior of another animal or the same species. Information conveyed includes location, presence of food or threat, sexual attraction, courtship, and dam–pup interactions. Pheromones are used widely in laboratory mice facilities to synchronize estrus and simultaneous breeding for logistic purposes. Female mice housed together in the absence of the male exhibit the Lee-Boot effect of lengthened diestrus or ovarian inactive period of up to several weeks. Whitten effect is described when a large number of female mice housed together in the absence of the male and having diestrus, will enter estrous 48 to 72 hours later upon exposure to male odors or male mouse urine soaked-bedding. Objective: The aim of this study is to determine the time taken for the Whitten effect to occur based on changes in vaginal cell characteristics, vulva appearance and behavior in grouped female mice. Methodology: Ten female mice were acclimatized to the animal facility for 3 estrus cycles or 12 days. Phases of the estrus cycle were evaluated by visual observation to assess changes to the vulva and vaginal cytology. Male urine soaked-bedding were exposed to females for 3 days and the time taken for the Whitten effect to occur was determined based on changes in vaginal cell characteristics, vulva appearance and observation of behavior. Result: The Cochran's Q test was used to observe the changes from diestrus to proestrus and later estrus. The results showed a significant difference (p
... Analyzing the issue of canine sex pheromones, we can clearly see that the publication by Goodwin at al. (1979) is still the most often cited study (Person 1985, Pageat and Gaulnier 2003, Kustritz 2005, Santos et al. 2013, Wani et al. 2013. Described as a primary dog sex pheromone, methyl paraben has become a component of commercially available products (Eau D'Estrus, Synbiotics, USA) recommended to both veterinarians and breeders as a useful tool for male canine sexual stimulation (Kustritz 2005, Kutzler 2005). ...
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The attempts of identification of sex pheromones playing crucial role in creation and modulation of the sexual behavior have been taken in many various domestic and wild species. In the present study, we evaluated the presence of methyl paraben, considered as a main sex pheromone in dogs, in secretions of bitches (GC/MS analysis) and, via behavioral tests, the ability of this substance to stimulate sexual arousal in stud dogs. We verified that some dogs can detect the most fertile period during estrus and we examined various objective methods for the evaluation of sex pheromone activity. Results obtained demonstrated that methyl paraben is not present in the urine of the bitch during estrus. Also, the effectiveness of methyl paraben (Eau D’Estrus, Synbiotics, USA) in causing sexual stimulation in male dogs has been questioned. The ability of male dogs to identify the most fertile period in bitches was confirmed, what suggest more complex characteristics of the semiochemical signal emitted by the bitch during estrus. We also concluded that bacteria present in the bitch’s vagina during estrus could significantly influence the production of semiochemicals. Moreover we found the evaluation of the blood flow (color Doppler) in ramifications of the penile artery in response to specific semiochemical signals, as a useful and specific method for detection of pheromonal stimulation in males. Taking into account the postulated complex character of sex pheromones in dogs, further studies including also detection of specific proteins and evaluation of reactivity of specific brain structures (fMRI) toward pheromones should be considered.
... Analyzing the issue of canine sex pheromones, we can clearly see that the publication by Goodwin at al. (1979) is still the most often cited study (Person 1985, Pageat and Gaulnier 2003, Kustritz 2005, Santos et al. 2013, Wani et al. 2013. Described as a primary dog sex pheromone, methyl paraben has become a component of commercially available products (Eau D'Estrus, Synbiotics, USA) recommended to both veterinarians and breeders as a useful tool for male canine sexual stimulation (Kustritz 2005, Kutzler 2005). ...
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The literature concerning the issue of canine sex pheromones includes reports presenting completely conflicting opinions about the chemical composition of the canine urine in the context of semiochemical communication. At present, the predominant report cited by many different authors is the article published in Science in 1979 by Goodwin at al., presenting methyl p-hydroxybenzoate (methyl paraben) as the main canine sex pheromone. While it has been proved that pure methyl paraben lacks semiochemical activity as do commercially available products containing this substance (Eau D'Estrus, Synbiotics, USA), in view of the conflicting published reports the aim of this study was to revaluate using modern techniques the presence of methyl p-hydroxybenzoate in canine urine during different phases of the ovarian cycle. Ten female dogs of different breeds were used. Urine samples from bitches collected during various stages of the ovarian cycle were examined with using the SPME and GC/MS methods. Methyl paraben was not detected in any of the samples. In conclusion, because of the lack of methyl-p-hydroxybenzoate in the samples examined, the present study confirmed negative opinions on the possibility of this substance playing a crucial role in semiochemical communication during reproduction in dogs (Canis familiaris).
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Chemical signals that mediate communication within animals of a species have been referred to as ‘pheromone’ a Greek word comprised of ‘pheran’ (means to transfer) and ‘hormon’ (to excite). These chemical messengers are transported outside the body and have a direct developmental effect on hormone levels and behavior, and therefore, have a potential role in modulating animal behavior and reproductive management. The sources of these chemical messengers are urine, vaginal secretions, feces, saliva, milk, sweat, breath and specialized cutaneous glands including the odor produced from hair and wool. After their release, are perceived through the olfactory system, eliciting both behavioral and endocrine responses characterized by profound effects on reproductive activity via the hypothalamic system that generates pulses of gonadotropin-releasing hormone. Their potential to transform the animal behavior and reproduction management has led to development and use of synthetic pheromones to manipulate estrous cycle, enhance estrous behavior, determination of time of estrus, and also facilitating collection of semen. Pheromones can act as a marker to detect estrus, diagnosing early pregnancy in farm animals and used for improving sexual desire. There is huge scope of application of pheromones once chemically synthesized and characterized, and would be of great interest to livestock owners and consumers. This chapter will discuss in detail the role of chemical signaling in shaping the behavior, reproduction and understanding the ways of communication in bovines.
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Post-pubertal Holstein heifers with palpable corpora lutea were injected i.m. with 25 mg PGF-2α to bring all animals to the follicular phase of the oestrous cycle. After 3 oronasal treatments with secretions from oestrous cows or water, heifers were observed for oestrus and inseminated about 12 h after the onset of oestrus. In Exp. I, heifers were treated with water or a mixture of urine and cervical mucus from oestrous cows at 6, 30 and 56 h after the PGF-2α injection. The percentage of heifers in oestrus within 72 h after PGF-2α was 86% for urine + cervical mucus-treated heifers and 60% for water-treated heifers (P > 0·05). Days to oestrus and conception rate after A.I. did not differ between the treatments. The degree of synchrony of oestrus after PGF-2α was significantly greater (P < 0·05) in the animals receiving urine + mucus treatment. In Exp. II, urine and cervical mucus from oestrous cows were separately tested in comparison to water. Test substances were applied at the time of PGF-2α injection, and 6 and 30 h later. The percentage of heifers in oestrus within 72 h after PGF-2α (100%) was highest (P < 0·05) in the cervical mucus-treated heifers but the conception rate (24%) was the lowest. The days to oestrus did not differ amongst groups but the degree of synchrony of oestrus after PGF-2α was greatest (P < 0·05) in animals treated with cervical mucus. These data indicate that a priming pheromone in the cervical mucus of oestrous cows can affect the ovarian function of herdmates and thereby improve synchrony of oestrus after PGF-2α injection.
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Three experiments were conducted to determine if electrical stimulation or the presence of a bull would hasten puberty in Angus and Hereford heifers. In experiment I, electrical stimulation of the genital tract per rectum given once on day 0 of the experiment failed to hasten puberty and did not alter the size of large follicles. The presence of a teaser bull, for a period of three weeks, did not hasten puberty in a group of prepuberal heifers in experiment II. Experiment III was designed to determine whether a response to bulls could be discerned if heifers were treated with 12 mg progesterone daily for nine days. Introduction of teaser bulls to progesterone-treated heifers did not influence the percentage of heifers that reached puberty in either of two 30-day trials of this experiment. Progesterone alone did not significantly increase the percentage of heifers that reached puberty, but it appeared to synchronize estrus in heifers that reached puberty after treatment.
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Many mammals use scent marks to advertise territory ownership, but only recently have we started to understand the complexity of these scent signals and the types of information that they convey. Whilst attention has generally focused on volatile odorants as the main information molecules in scents, studies of the house mouse have now defined a role for a family of proteins termed major urinary proteins (MUPs) which are, of course, involatile. MUPs bind male signalling volatiles and control their release from scent marks. These proteins are also highly polymorphic and the pattern of polymorphic variants provides a stable ownership signal that communicates genome-derived information on the individual identity of the scent owner. Here we review the interaction between the chemical basis of mouse scents and the dynamics of their competitive scent marking behaviour, demonstrating how it is possible to provide reliable signals of the competitive ability and identity of individual males. (C) 2004 Wiley Periodicals, Inc.
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The wool and wax collected from entire Dorset rams contained odoriferous substances (pheromones) that stimulated 48% of a group of Romney ewes to ovulate in 5 days. The response was similar to that obtained in ewes running with Dorset rams. Only 7% of the ewes isolated from rams ovulated in the same period.Ram urine was not found to be a major source of the pheromone.
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The introduction of Dorset rams to Romney ewes at the beginning of the breeding season (February 14 to March 1) stimulated 39% to 70% of the non-cycling ewes to ovulate. Most of the ewes that ovulated did so within 65 to 72 hours of ram introduction. The ovulations were preceded by LH peaks, the mean onset of which was 35.0±4.8 (SE) hours after ram introduction. The mean oestradiol-17β concentration per ewe ranged from 0.3 to 14.9 pg/ml plasma and there were large fluctuations among the samples collected every 3 hours. All ewes, irrespective of treatment, had similar mean concentrations of oestradiol-17β and ovarian follicular activity, and there were no changes in oestradiol-17β concentration that could be attributed to the presence of the rams.