Journal of Veterinary Advances
Estrus Identification Through Colpocytology in Sows in
Intensive Free-Range Breeding
Vidal B. R., Silva G. F. D., Santos J. S., Dias F. E. F., Lima A. K. F., Viana E. B., Neves W. C.,
Viana G. E. N., Gomes M. G. T. and Cavalcante T. V.
J Vet Adv 2013, 3(10): 281-284
Online version is available on: www.grjournals.com
ISSN: 2251-7685
VIDAL ET AL.
Original Article
Estrus Identification Through Colpocytology in
Sows in Intensive Free-Range Breeding
1
1
Vidal B. R., 2Silva G. F. D., 3Santos J. S., 2Dias F. E. F., 2Lima A. K. F., 2Viana E. B.,
4
Neves W. C., 4Viana G. E. N., 2Gomes M. G. T. and 2Cavalcante T. V.
PIBIC/CNPq, Escola de Medicina Veterinária e Zootecnia, campus de Araguaína, Universidade Federal do Tocantins [UFT].
2
Escola de Medicina Veterinária e Zootecnia, campus de Araguaína,Universidade Federal do Tocantins [UFT].
3
Ciência Animal Tropical [PGCAT], Universidade Federal do Tocantins, campus de Araguaína.
4
Departamento de Morfofisiologia Veterinária, Centro de Ciências Agrárias, Universidade Federal do Piauí [UFPI].
Abstract
The objective of the present study was to identify the first estrus postpartum, through vaginal cytology, in
sows subjected to intensive free-range pig breeding (Sistema Intensivo de Criação de Suínos ao Ar Livre SISCAL), in the northern region of the state of Tocantins. The assessment began 48 hours after farrowing, and
continued until heat behavior was identified. This study was conducted at School of the Veterinary Medicine
and Animal Science of the Federal University of Tocantins, at Campus de Araguaína, in the period between
August/2010 and July/2011. The coefficients analyzed were the percentage of epithelial cells in the phases of
postpartum anoestrus, proestrus and estrus, using vaginal smear cytology, in six sows, in which four types of
cells were identified: parabasal, intermediary, superficial with nucleolus or without nucleus. During the weaning
period until the onset of estrus, and during estrus, a higher percentage of superficial cells, with or without
nucleus was detected (32.68% and 38.50%) and (51.67% and 58.0%), respectively. The conclusion was that,
through vaginal smear cytology, it was possible to identify the onset of estrus in weaning sows, submitted to the
intensive free-range breeding system (SISCAL), in the state of Tocantins, thus facilitating the identification of
the best moment for natural breeding or artificial insemination, as with other species, such as dogs or goats.
Keywords: Colpocytology, estrous, swine, SISCAL.

Corresponding author: PIBIC/CNPq, Escola de Medicina Veterinária e Zootecnia, campus de Araguaína, Universidade Federal do Tocantins [UFT].
Received on: 20 Jun 2013
Revised on: 18 Jul 2013
Accepted on: 15 Oct 2013
Online Published on: 30 Oct 2013
281
J. Vet. Adv., 2013, 3(10): 281-284
ESTRUS IDENTIFICATION THROUGH COLPOCYTOLOGY IN ...
Introduction
Swine culture is currently enjoying a great
expansion in Brazil, and has an important economic
and social role in Brazilian industry, especially as
an instrument to keep populations in the
countryside, as intensive farming is primarily done
in small areas and is largely a family-run business
(Basso et al., 2012). Nowadays, Brazilian
production represents 10% of the volume of pork
exports worldwide, with annual revenues of more
than US$ 1 billion. As a result of investments in the
swine farming industry, it is estimated that pork
production and consumption will increase on
average 2.84% and, 1.79% per year, respectively, in
the period between 2008/2009 and 2018/2019. In
relation to exports, the participation of Brazilian
pork products is expected to leap from 10, 1%, in
2008, to 21% in 2018/2019 (MAPA, 2011).
In this scenario, maximizing the reproductive
efficiency of any given swine production unit is
fundamental for its economic feasibility. In order to
do so, it is necessary to design managing
techniques, which result in reproductive rates which
conduce to favorable cost-benefit, as determined by
those responsible for production (Sobestiansky et
al., 1998).
Vaginal cytology or colpocytology is a
diagnostic method which allows the monitoring of
several phases of the estrous cycle. It easy to
conduct, low-cost examination, which consists of
assessing vaginal epithelial cells in different species
(Porto et al., 2007; Raposo et al., 2000; Snoeck et
al., 2011), for the selection of the best moment for
natural breeding or artificial insemination, as
observed in dogs (Schutte, 1967), bovine and
bubaline (Rama Rao et al., 1976), caprine (Toniollo
et al., 2005) e ovine (Ghannam et al., 1972). In fact,
there is a correlation between the morphology of
vaginal epithelium and changes in the
predominance of ovarian hormone in peripheral
circulation (Krajnicáková et al., 1991). The
objective of the present study is to identify the first
estrus postpartum, through vaginal cytology, in
sows subjected to intensive free-range pig breeding
(Sistema Intensivo de Criação de Suínos ao Ar
282
J. Vet. Adv., 2013, 3(10): 281-284
Livre - SISCAL), in the northern region of the state
of Tocantins.
Materials and Methods
The present study was conducted at School of
the Veterinary Medicine and Animal Science of the
Federal University of Tocantins, at Campus of the
Araguaína, at the Swine Culture Sector and Animal
Reproduction Laboratory in the period between
august/2010 and July/2011. Six cyclic mix-breed
females, with average age between 14 and 16
months, were selected, and farmed in intensive freerange pig breeding system (SISCAL).
Cytological material collection was done via
vaginal smear, obtained in a single sample, taken
from each animal once a week, beginning 48 hours
postpartum until the 42nd day (weaning). Then,
collection frequency was changed, occurring every
day at the same time, 07:00AM, until the day of
presentation of estrus behavior, as recommended by
Silva et al., (2004). The weaning-to-heat interval,
in hours, began at the start of weaning, at 07:00
AM, and ended in the moment the sow showed
signs of standing heat reflex in the presence of the
male.
The slides for cytological examination, made
from the smear, were fixed and dyed according to
Papanicolau methodology. Vaginal smear was
analyzed under a 400x-optical microscope, counting
100 cells per slide.
Comparisons were conducted using Chisquared test with a 5% significance level. Multiple
correspondence analyses were conducted with the
objective of assessing the interrelationships between
groups of epithelial cells and puerperium. In order
to do so, PROC CORRESP procedures from
Statistical Analysis System (SAS, 2002) were used.
Results and Discussion
Citoscopy revealed epithelial cells originated
from three functional layers (deep, intermediary and
superficial), simultaneously, in all the phases of the
estrous cycle. Similarly to what was described by
Sobestiansky et al., (1998), during lactation, heat
behavior was not observed, however, on average
96h after the weaning, all animals started
VIDAL ET AL.
manifesting standing heat reflex and positive
response to back-pressure test. The results, in
percentages, for the different types of epithelial
cells during puerperium, which encompasses the
phases of anoestrus, postpartum, weaning-to-estrus
interval (WOH), and estrus are presented in Table 1.
Table 1: Percentage of epithelial cells observed in puerperium (postpartum up to 42nd day (weaning),
weaning-to-estrus interval and estrus, obtained by vaginal smear cytology in six sows, farmed the SISCAL
system, in Araguaína (TO).
Puerperium
Cells
Postpartum
WOI
Estrus
Superficial Enucleated
Superficial
Intermediary
Parabasal
22.42(807) Ca
28,39(1022) Aa
21,33(768) Da
27,86(1003) Ba
32,86(601) Bb
51,67(945) Ab
8,58(157) Cb
6,89(126) Db
38,50(231) Bc
58,00(348) Ac
2,17(13) Cc
1,33(8) Cc
abc
Distinct lower-case superscripts in a line indicate a statistically significant difference (p<0,05) according to chisquared test.
abc
Distinct upper-case superscripts in a column indicate a statistically significant difference (p<0,05) according to
chi-squared test.
The predominance of desquamative epithelial
cells (superficial, with and without nucleus)
observed during the weaning-to-heat interval, as
well as the first day of estrus; 84.53% and 96.50%
respectively, did not represent a statistical
difference (p>0, 05). The duration of the weaningto-estrus interval plays an important role in the
determination of the efficiency of artificial
insemination programs, as the moment for the
conduction of AI must be synchronized with
ovulation (Correa et al., 2001). It is the optimal
period to increase the number of litters/sow/year
and, as a result, the number of pigs
weaned/sow/year (Antunes, 2007).
The increased number of superficial cells, with
and without nucleus, during estrus is justified by the
significant influence of estrogen on the vaginal
epithelium, resulting in intense desquamation and
consequent identification of this type of cell in the
citoscopy (Krajnicáková et al., 1992).
Such results corroborate those found by Schutte
(1967) as well as Santos et al., (1997) who, when
working with female-dogs found more than 90% of
superficial epithelial cells in the same phases.
Monteiro et al., (2002), when conducting
colpocytologic evaluations in two females of Crabeating Fox (Cerdocyon thous), observed that the
differentiation of vaginal cell types during distinct
estrous cycle phases follows the same patterns
found in domestic female dogs.
283
Raposo et al., (2000) and Toniollo et al.,
(2005), while studying colpocytology of goats,
observed a higher number of superficial cells with
and without nucleus, when compared to other
phases of the estrous cycle. Similar results were
observed by Porto et al., (2007) when studying
cyclic Santa Inês sheep farmed in the State of
Tocantins. Ghannam et al., (1972) observed that
during the estrogenic phase of the estrous cycle of
sheep, there is an increase in superficial and
intermediary cell numbers. However, both
Krajnicáková et al., (1992) and Gomes (2007),
when working with merino and Santa Inês sheep,
respectively, did not observe any predominance in
the cellular pattern during estrus.
The changes in the cellular pattern occurring in
the vaginal epithelium of females, even during
lactation, is probably due to the fact that there are
intermittent moments between follicle group
growth, without dominance, and follicular growth,
which are responsible for ovarian estrogen
synthesis, thus the predominance of superficial and
parabasal cells with nucleus, between postpartum
and the period before the weaning-to-heat interval.
Postpartum cellular patterns, during lactation
anoestrus were similar to those found by Ribeiro et
al., (2012), when studying 27 Spotted Paca
(Cuniculus paca). Krajnicáková et al., (1992), using
colpocytology up to the 51st day of puerperium, in
sheep, observed a decline in the percentage of basal
J. Vet. Adv., 2013, 3(10): 281-284
ESTRUS IDENTIFICATION THROUGH COLPOCYTOLOGY IN ...
and parabasal cells, on the seventh day, and an
increase in their frequency¸ representing 66% of
vaginal cells, close to the 14th day postpartum.
However, this was not observed with superficial
cells, which displayed low percentages throughout
the whole experiment, amounting to an average of
11% of all cell types. Gomes (2007) observed a
predominance of superficial and intermediary cells
in the same period, with approximately 30%
incidence for each of the types, and only 13% and
6% of parabasal and basal cells, respectively.
The conclusion is that vaginal cytology smear
is an efficient method for the identification of
estrus, as an adjuvant to standing reflex and back
pressure test, thus facilitating detection of the best
moment for natural breeding or artificial
insemination.
Acknowledgements
The present study was conducted with the
support of Conselho Nacional de Desenvolvimento
Científico e Tecnológico – CNPq – Brasil and
Conselho Estadual de Ciência e TecnologiaTocantins.
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