Acta Veterinaria Hungarica 52 (4) (2004)

Acta Veterinaria Hungarica 52 (4) (2004)

CONTENTS AND ABSTRACTS

Biochemistry and physiology

Changes in thyroxine, 3,3’,5-triiodothyronine and 3,3’5’-triiodothyronine content in the thyroid gland and in serum to thyroid tissue iodothyronine ratios during ontogenesis in the fetal pig. Ewa Brzezińska-Ślebodzińska and A. B. Ślebodziński 379

Regulation of growth hormone expression by thyrotropin-releasing hormone through the pituitary-specific transcription factor Pit-1 in chicken pituitary. P. Van As, C. Careghi, V. Bruggeman, O. M. Onagbesan, S. Van der Geyten, V. M. Darras and E. Decuypere 389

Effect of excess selenium supplementation on the glutathione redox system in broiler chicken. K. Balogh, Mária Weber, Márta Erdélyi and M. Mézes 403

Effect of vitamin E on carbonic anhydrase enzyme activity in rainbow trout (Oncorhynchus mykiss) erythrocytes in vitro and in vivo. Ş. Aras-Hisar, O. Hisar, Ş. Beydemir, I. Gülçin and T. Yanik 413
Clinical veterinary science

Cystoscopy in cattle – a valuable additional tool for clinical examination. Sonja Franz, Petra Winter and W. Baumgartner 423
Genetics

Antimutagenic effects of extracts from sage (Salvia officinalis) in mammalian system in vivo. M. Vujošević and Jelena Blagojević 439
Infectious diseases

Examination of the role of Mycoplasma bovis in bovine pneumonia and a mathematical model for its evaluation. M. Tenk, L. Stipkovits and L. Hufnagel 445
Nutrition

Changes in daily energy amounts of main milk components (lactose, protein and fat) during the lactation of high-yielding dairy cows. A. Gáspárdy, Z. Schwartz, L. Zöldág, T. Veresegyházy and S. Fekete 457
Parasitology

Molecular phylogeny of the kidney-parasitic Sphaerospora renicola from common carp (Cyprinus carpio) and Sphaerospora sp. from goldfish (Carassius auratus auratus). Edit Eszterbauer and Cs. Székely 469
Reproduction

Survival of mouse blastocysts after low-temperature preservation under high pressure. Cs. Pribenszky, M. Molnár, S. Cseh and L. Solti 479

Progesterone profiles and oestrous cycle changes following superovulatory treatment of Holstein-Friesian dairy cows in a tropical environment. B. Bényei, Margit Kulcsár, A. Gáspárdy and Anna Pécsi 489

Induction of ovulation with GnRH and PGF₂alpha in lactating Bos taurus × Bos indicus cows. C. Ahuja and F. Montiel 501

Acta Veterinaria Hungarica 52 (4), pp. 379–387 (2004)

CHANGES IN THYROXINE, 3,3’,5-TRIIODOTHYRONINE AND 3,3’5’-TRIIODOTHYRONINE CONTENT IN THE THYROID GLAND AND IN SERUM TO THYROID TISSUE IODOTHYRONINE RATIOS DURING ONTOGENESIS IN THE FETAL PIG

Ewa Brzezińska-Ślebodzińska and A. B. Ślebodziński^*

Department of Hormonal Action Mechanisms, Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences in Olsztyn, ul. Grunwaldzka 250, 60-166 Poznań, Poland

(Received February 11, 2004; accepted May 24, 2004)

The concentrations of thyroxine (T₄), 3,3’,5-triiodothyronine (T₃) and 3,3’,5’-triiodothyronine (reverse T₃; rT₃) in thyroid gland tissue and serum of the fetal pig (n = 68) from day 39 to 113 of gestation were measured. Tracer quantities of iodothyronines, displaying the onset of thyroid hormone activity, were found in the thyroid tissue on day 39, i.e. before the appearance of a measurable quantity of iodothyronines in the serum. The T₄ and T₃ thyroidal content showed the first rise between days 56 and 76. Then, T₃ was increasing sharply from day 92 till birth, while T₄ content was decreasing from about day 76 to a low value between day 92 and 105, and then showing an increase shortly before birth. The rT₃ content was the highest on day 39 and then it was steadily decreasing to reach a nadir on about day 76. Measurable amounts of thyroid hormones (TH) in the serum were observed not earlier than on day 46 of gestation. Near birth, the tissues of the pig fetus are in a milieu characterised by the highest blood TH concentrations. The serum to thyroid concentration ratio for rT₃ and T₄ was generally below 1.0 until the last trimester of gestation, when it was over 5.0 for rT₃ and over 4.0 for T₄. By contrast, the T₃ serum to thyroid ratio was below 0.5 throughout the gestation. The results show that the fetal pig thyroid displays a low rT₃ and T₄ content, but the marked T₃ elevation observed near term supports the view that a high production and secretion of T₃ near term may be a critical factor for normal postnatal adaptation to extrauterine cooling in the pig.

Key words: Thyroxine, triiodothyronine, reverse triiodothyronine, thyroid gland, fetal pig

^{*Corresponding author: Professor
emeritus A. B. Ślebodziński; E-mail: endocrin@ rose.man.poznan.pl; Fax: 48 (61) 868 53
28

Acta Veterinaria Hungarica 52 (4), pp. 389–402
(2004)
REGULATION OF GROWTH HORMONE EXPRESSION BY THYROTROPIN-RELEASING
HORMONE THROUGH THE PITUITARY-SPECIFIC TRANSCRIPTION FACTOR PIT-1 IN CHICKEN
PITUITARY
P. Van As^1*, C. Careghi¹, V.
Bruggeman¹, O. M. Onagbesan¹, S. Van der Geyten², V. M.
Darras² and E. Decuypere¹
1Laboratory for Physiology and Immunology of Domestic Animals,
Department of Animal Production, Katholieke Universiteit Leuven, Kasteelpark Arenberg 30,
B-3001 Leuven, Belgium; ²Laboratory of Comparative Endocrinology, Zoological
Institute, Katholieke Universiteit Leuven, Naamsestraat 61, B-3000 Leuven, Belgium
(Received January 9, 2004; accepted May 24, 2004)

Pit-1 is a pituitary-specific POU-domain DNA binding factor, which
binds to and trans-activates promoters of growth hormone- (GH), prolactin- (PRL) and
thyroid stimulating hormone beta- (TSHß)
encoding genes. Pit-1 has been identified in several mammalian and
avian species. Thyrotropin-releasing hormone (TRH) is located in the hypothalamus and it
stimulates TSH, GH and PRL release from the pituitary gland. In the present study, we
successfully developed a competitive RT-PCR for the detection of Pit-1 expression in the
chicken pituitary, that was sensitive enough to detect picogram levels of Pit-1 mRNA.
Applying this method, the effect of TRH injections on Pit-1 mRNA expression was determined
in the pituitary of chick embryos and growing chicks. In both 18-day-old embryos and
10-day-old male chicks the Pit-1 mRNA expression was significantly increased following TRH
injection, thereby indicating that the stimulatory effects of TRH on several pituitary
hormones is mediated via its effect on Pit-1 expression. Therefore, a semi-quantitative
RT-PCR method was used to detect possible changes in GH levels. TRH affected the GH mRNA
levels at both developmental stages. These results, combined with the data on Pit-1 mRNA
expression, indicate that Pit-1 has a role in mediating the stimulatory effects of TRH on
pituitary hormones like GH.

Key words: Chicken, pituitary, Pit-1, TRH, GH

*Corresponding author: Pieter Van As; E-mail:
pieter.vanas@agr.kuleuven.ac.be; Phone: +32 (16) 321729; Fax: +32 (16) 321994

Acta Veterinaria Hungarica 52 (4), pp. 403–411 (2004)
EFFECT OF EXCESS SELENIUM SUPPLEMENTATION
ON THE GLUTATHIONE REDOX SYSTEM IN BROILER CHICKEN
K. Balogh, Mária Weber, Márta Erdélyi and M. Mézes^*
Department of Nutrition, Szent
István University, H-2103 Gödöllő, Páter K. u. 1, Hungary

(Received February 12, 2004; accepted May 24, 2004)

Selenium, as part of selenocysteine, is the active centre of
selenoenzymes. Excess amount of selenium generates oxygen free radicals and reacts with
thiol compounds such as reduced glutathione, composing seleno-diglutathione. These
reactions impair the amount and/or activity of the biological antioxidant defence system.
In the present experiment the effects of two inorganic selenium sources (Na₂SeO₃,
Na₂SeO₄) on lipid peroxidation and on the content and activity of
some components of the antioxidant defence mechanism were studied in Ross 308 hybrid
cockerels. In the tissues examined, the glutathione redox system was altered in different
ways as an effect of excess selenium. The amount of glutathione and, consequently,
glutathione peroxidase activity declined in the blood plasma and in the red blood cell
haemolysate, while in the liver malondialdehyde concentration increased only at the end of
the experimental period as a result of the boosted enzyme activity. The authors suppose
that the cause of increased lipid peroxidation was the potential toxic effect of selenium
accumulation above the actual demand.
Key words: Selenium, toxicity, glutathione redox system, broiler
chicken

*Corresponding author: Prof. Dr. Miklós
Mézes; E-mail: Mezes.Miklos@mkk.szie.hu; Fax: +36 (28) 410804

Acta Veterinaria Hungarica 52 (4), pp. 413–422 (2004)
EFFECT OF VITAMIN E ON CARBONIC ANHYDRASE ENZYME ACTIVITY IN RAINBOW
TROUT (ONCORHYNCHUS MYKISS) ERYTHROCYTES IN VITRO AND IN VIVO
Ş. Aras-Hisar¹,
O. Hisar^1*, Ş. Beydemir², I. Gülçin² and T. Yanik¹

1Department of Aquaculture, Agriculture Faculty, Atatürk
University, 25240 Erzurum, Turkey; ²Department of Chemistry, Arts and Science
Faculty, Atatürk University, Erzurum, Turkey
(Received October 2, 2003; accepted March 2, 2004)

Considering that the excessive usage of vitamin E causes
hypervitaminosis and thus reduces blood erythrocyte concentrations, therefore it is worth
studying how its pharmacological dosage affects the activity of carbonic anhydrase (CA)
enzyme found in erythrocytes of rainbow trout (Oncorhynchus mykiss) in vitro
and in vivo. Vitamin E inhibited CA enzyme and the IC₅₀ value of the
vitamin was 0.039 mM in vitro. Similarly, it was seen that vitamin E inhibited CA
enzyme activity after the first hour following vitamin E injections in vivo. The
activities of CA in groups of trout given vitamin E injection were measured at 1, 3 and 5
h and the corresponding activities were found to be 772.7 ± 290.5 (P < 0.05), 1286.4
± 378.2 and 1005.7 ± 436.1 enzyme units (EU) g Hb^–1. The difference over
the control was significant (P < 0.05) in the first hour and insignificant at 3 and 5 h
(P > 0.05). The activity of CA in the control, which did not contain vitamin E,
was determined as 1597.7 ± 429.0 EU g Hb^–1.
Key words: Carbonic anhydrase, erythrocyte, vitamin E, trout

*Corresponding author: Dr. Olcay Hisar; E-mail:
ohisar@atauni.edu.tr; Fax: +90 (442) 236-0948

Acta Veterinaria Hungarica 52 (4), pp. 423–438 (2004)
CYSTOSCOPY IN CATTLE – A VALUABLE ADDITIONAL TOOL FOR CLINICAL
EXAMINATION
Sonja Franz^*, Petra Winter and W. Baumgartner
Clinic for Ruminants, University of Veterinary Medicine Vienna,
Veterinärplatz 1, 1210 Vienna, Austria
(Received July 21, 2003; accepted May 24, 2004)

Based on the findings of physical examination and on laboratory
findings the urinary bladder of 23 cows was examined endoscopically in order to
investigate the application of cystoscopy in cattle. The endoscopic findings of all
examined cows were compared with the findings of physical examination and the results of
macroscopic and microscopic urinalysis and the bacteriological culture of the urine. By
physical examination only 3 cows were diagnosed to have urinary tract disease, whereas all
other cows were suspected of having an urinary tract disease. Bacteriological culture of
the urine revealed Corynebacterium renale and Escherichia coli
infection in 18 cows, while the remaining 5 cows were negative. By cystoscopy catarrhal
cystitis was diagnosed in 2 cases, haemorrhagic cystitis in 5 cases, and
fibrinous-purulent and fibrinous-haemorrhagic cystitis in 13 cases. Three cows showed no
pathological changes of the urinary bladder mucosa by endoscopic examination. Cystoscopy
facilitates diagnosis through the direct visualisation of mucosal lesions and makes it
possible to give a more accurate prognosis based upon the findings.
Key words: Endoscopy, cystoscopy, urinary tract infection,
cystitis, cattle, cow

*Corresponding author; E-mail: sonja.franz@vu-wien.ac.at;
Fax: +43 (1) 25077/5290

Acta Veterinaria Hungarica 52 (4), pp. 439–443 (2004)
ANTIMUTAGENIC EFFECTS OF EXTRACTS FROM SAGE (SALVIA OFFICINALIS)
IN MAMMALIAN SYSTEM IN VIVO
M. Vujošević^* and Jelena Blagojević

Department of Genetics, Institute for Biological Research ‘Siniša
Stanković’, 29 novembra 142, 11060 Belgrade, Serbia and
Montenegro

(Received October 2, 2003; accepted May 24, 2004)

Naturally occurring antimutagenic factors, especially those of plant
origin, have recently become a subject of intensive research. Antimutagenic properties of
terpenoid fractions of sage (Salvia officinalis) were tested in mammalian system in
vivo through examining the ability of sage to decrease the frequency of aberrant cells
induced by a potent mutagen. First, groups of mice were treated with three concentrations
of sage alone and it was established that the frequency of aberrant cells after treatment
with a concentration of 25 µL/kg was not significantly different from the negative
control (olive oil), while that found after treatment with the 50 µL/kg concentration
differed significantly (X²₍₁₎ = 4.05, p < 0.05). Sage used at a
concentration of 100 µL/kg was cytotoxic. Mitomycin C (MMC), known as a potent mutagen,
was used for induction of chromosome aberrations. Post-treatment with sage suppressed the
effects of MMC significantly. Both concentrations (25 µL/kg and 50 µL/kg) produced a
significant decrease in the frequency of aberrations relative to MMC (X²₍₁₎
= 5.42, p < 0.02, X²₍₁₎ = 14.93, p < 0.001,
respectively). The percent of aberrations decreased with increasing concentrations of
sage. Only nontoxic concentrations of sage without mutagenic effects can be recommended
for use as inhibitors of mutagenesis or carcinogenesis.
Key words: Sage, antimutagenesis, chromosome aberrations

*Corresponding author: Mladen Vujošević; E-mail: mladenvu@ibiss.bg.ac.yu;
Fax: +38 111761433

Acta Veterinaria Hungarica 52 (4), pp. 445–456 (2004)
EXAMINATION OF THE ROLE OF MYCOPLASMA BOVIS IN BOVINE
PNEUMONIA AND A MATHEMATICAL MODEL FOR ITS EVALUATION
M. Tenk¹, L. Stipkovits^2* and L.
Hufnagel³
1Central Veterinary Institute, H-1149 Budapest, Tábornok u. 2,
Hungary; ²Veterinary Medical Research Institute, Hungarian Academy of Sciences,
Budapest, Hungary; ³Department of Mathematics and Informatics, Szent István
University, Budapest, Hungary
(Received July 29, 2003; accepted March 24, 2004)

The authors screened 34 large cattle herds for the presence of Mycoplasma
bovis infection by examining slaughtered cattle for macroscopic lung lesions, by
culturing M. bovis from lung lesions and at the same time by testing sera for the
presence of antibodies against M. bovis. Among the 595 cattle examined, 33.9% had
pneumonic lesions, mycoplasmas were isolated from 59.9% of pneumonic lung samples, and
10.9% of sera from those animals contained antibodies to M. bovis. In 25.2%
of the cases M. bovis was isolated from lungs with no macroscopic lesions. The
proportion of seropositive herds was 64.7%. The average seropositivity rate of individuals
was 11.3% but in certain herds it exceeded 50%. A probability model was developed for
examining the relationship among the occurrence of pneumonia, the isolation of M. bovis
from the lungs and the presence of M. bovis specific antibodies in sera.
Key words: Mycoplasma bovis infection, ELISA, culture,
pneumonia

*Corresponding author: Dr. László Stipkovits, Veterinary Medical Research Institute, Hungarian
Academy of Sciences, H-1581 Budapest, P.O. Box 18, Hungary; E-mail:
stipkovits@novell.vmri.hu; Fax: +36 (1) 467 4067

Acta Veterinaria Hungarica 52 (4), pp. 457–467 (2004)
CHANGES IN DAILY ENERGY AMOUNTS OF MAIN MILK COMPONENTS (LACTOSE,
PROTEIN AND FAT) DURING THE LACTATION OF HIGH-YIELDING DAIRY COWS
A. Gáspárdy^1*, Z.
Schwartz¹, L. Zöldág¹, T. Veresegyházy² and S. Fekete¹

1Department of Animal Breeding, Nutrition and Laboratory Animal
Science and ²Department of Physiology and Biochemistry, Faculty of Veterinary
Science, Szent István University, H-1078 Budapest, István u. 2, Hungary
(Received October 1, 2003; accepted March 2, 2004)

The aim of this study was to examine the changes of the daily energy
amount of lactose, protein and fat throughout the lactations, and compare them to each
other. A total of 309 Israeli Holstein-Friesian cows from one kibbutz were investigated in
three lactations, and information was given for a period of five years from 1996 to the
end of 2000. The distribution of milk components and milk yield during lactation, and
changes of the absolute and relative energy amount in the different milk components were
calculated and evaluated. The results showed changes in the energy content of milk and its
different components throughout the lactation. Each component (fat, lactose and protein)
is dominant in different periods during the lactation. The energy amount from fat reaches
a peak first, between days 40 and 50. Lactose has a peak at about day 66 of lactation, and
protein reaches the peak last, approximately at day 104 of lactation. It seems that this
peak sequence is constant and it is considered to be physiological. It might be suggested
that there is a regulation governing the secretion of the different components at
different times, and only one component is dominant in a given period. Each component
exerts negative and positive influences on the secretion of the other components, which
interact with each other and are not fully independent.
Key words: Synthesis of milk components, energy content of milk,
lactose, protein, fat, dairy cow

*Corresponding author: Dr. András Gáspárdy; E-mail: agaspard@univet.hu; Fax: +36
(1) 478 4128

Acta Veterinaria Hungarica 52 (4), pp. 469–478 (2004)
MOLECULAR PHYLOGENY OF THE KIDNEY-PARASITIC SPHAEROSPORA RENICOLA
FROM COMMON CARP (CYPRINUS CARPIO) AND SPHAEROSPORA SP. FROM GOLDFISH (CARASSIUS
AURATUS AURATUS)
Edit Eszterbauer^* and Cs. Székely
Veterinary Medical Research Institute, Hungarian Academy of Sciences,
H-1581 Budapest, P.O. Box 18, Hungary
(Received June 23, 2004; accepted September 1, 2004)

The genetic relatedness of two kidney-parasitic Sphaerospora species
was studied. Although S. renicola, the causative agent of swimbladder inflammation
of common carp fingerlings (Cyprinus carpio), and Sphaerospora sp.
originating from goldfish (Carassius auratus auratus) were indistinguishable on the
basis of spore morphology, they were found to be genetically different as their 18S rDNA
sequences shared only 71.9% identical nucleotides. In the phylogenetic trees, Sphaerospora
sp. from goldfish grouped with Myxidium truttae (AJ582061) within the clade of the
coelozoic freshwater species. Sphaerospora renicola clustered with S. molnari
(AF378345) within the group of myxosporeans histozoic in gills. The topology of the six Sphaerospora
species on the phylogenetic trees implied that myxospore morphology does not correlate
with the genetic relationships, and the genus seems to be polyphyletic.
Key words: Myxosporeans, Sphaerospora spp., carp,
goldfish, kidney tubules, swimbladder inflammation, 18S rDNA, molecular phylogeny

*Corresponding author; E-mail: eedit@vmri.hu; Fax: +36 (1)
467 4076

Acta Veterinaria Hungarica 52 (4), pp. 479–487 (2004)
SURVIVAL OF MOUSE BLASTOCYSTS AFTER LOW-TEMPERATURE PRESERVATION
UNDER HIGH PRESSURE
Cs. Pribenszky^1*, M. Molnár², S.
Cseh¹ and L. Solti¹
1Department and Clinic of Obstetrics and Animal Reproduction,
Faculty of Veterinary Science, Szent István University, H-1078 Budapest, István u. 2,
Hungary; ²Ybl Miklós School, Szent István University, H-1146 Budapest,
Thököly u. 74, Hungary
(Received March 1, 2004; accepted May 24, 2004)

Cryoinjuries are almost inevitable during the freezing of embryos. The
present study examines the possibility of using high hydrostatic pressure to reduce
substantially the freezing point of the embryo-holding solution, in order to preserve
embryos at subzero temperatures, thus avoiding all the disadvantages of freezing. The
pressure of 210 MPa lowers the phase transition temperature of water to –21°C.
According to the results of this study, embryos can survive in high hydrostatic pressure
environment at room temperature; the time embryos spend under pressure without significant
loss in their survival could be lengthened by gradual decompression. Pressurisation at 0°C
significantly reduced the survival capacity of the embryos; gradual decompression had no
beneficial effect on survival at that stage. Based on the findings, the use of the
phenomena is not applicable in this form, since pressure and low temperature together
proved to be lethal to the embryos in these experiments. The application of hydrostatic
pressure in embryo cryopreservation requires more detailed research, although the
experience gained in this study can be applied usefully in different circumstances.
Key words: Embryo cryopreservation, high hydrostatic pressure,
freezing point depression, blastocyst, freezing

*Corresponding author: Csaba Pribenszky; E-mail:
cpriban@univet.hu; Fax: +36 (1) 478 4207

Acta Veterinaria Hungarica 52 (4), pp. 489–499 (2004)
PROGESTERONE PROFILES AND OESTROUS CYCLE CHANGES FOLLOWING
SUPEROVULATORY TREATMENT OF HOLSTEIN-FRIESIAN DAIRY COWS IN A TROPICAL ENVIRONMENT
B. Bényei^1*, Margit Kulcsár², A.
Gáspárdy³ and Anna Pécsi⁴
1Research Institute, Faculty of Veterinary Science, Szent István
University, Üllő, Dóra-major, Hungary, ²Department and Clinic for Obstetrics and Reproduction and ³Department
of Animal Breeding, Nutrition and Laboratory Animal Science, Faculty of Veterinary
Science, Szent István University, Budapest, Hungary; ⁴Department of Animal
Physiology and Animal Health, University of Debrecen, Debrecen, Hungary

(Received January 19, 2004; accepted May 24, 2004)

Changes of progesterone (P4) profiles and oestrous cycle were
investigated up to 70 days in 20 superovulated Holstein-Friesian cows in a dry tropical
environment (Brazil). Superovulated cows showed no significant differences in relation to
P4 level at the time of embryo recovery (39.0 ± 27.1 nmol/L, P = 0.536), first and second
(12.0 ± 6.0 and 10.7 ± 2.2 nmol/L, P = 0.543) cycle. There was a close correlation
between serum P4 concentration and the number of corpora lutea (CL; 13.3 ± 9.5) at the
recovery (P < 0.0001). After the embryo collection, cows returned to cycle in different
ways: (i) group of donors returning to cycle after 2.2 ± 0.8 days, (ii)
group with a delay of 11.0 ± 1.9 days; and (iii) animals having a long (28.8 ±
2.2 days) acyclic period, which is significant (P < 0.001). The remaining animals (30%)
showed cystic ovarian malformations. P4 level at the time of embryo recovery does not
influence the oestrous cycle changes. The results suggest that Holstein-Friesian donor
cows may suffer from cystic ovarian degeneration and may have a long acyclic period after
superovulatory treatment in a tropical climate.
Key words: Superovulation, heat stress, progesterone
concentration, P4, Holstein-Friesian cows, oestrous cycle changes

*Corresponding author:
Balázs Bényei, Institute of Experimental Medicine of the Hungarian Academy of Sciences,
H-1083 Budapest, Szigony u. 43, Hungary; E-mail: benyei@koki.hu; Phone/Fax: +36 (1)
2991002

Acta Veterinaria Hungarica 52 (4), pp. 501–508
(2004)
INDUCTION OF OVULATION WITH GNRH AND PGF_2alpha IN LACTATING BOS TAURUS × BOS INDICUS
COWS
C. Ahuja and F. Montiel^*
Department of Reproduction, Faculty of Veterinary Medicine, University
of Veracruz, Circunvalación S/N Esquina Yanez, Código Postal 91740 Veracruz, Ver.,
Mexico
(Received November 21, 2003; accepted March 2, 2004)

Induction of ovulation for timed artificial insemination (TAI) with the
Ovsynch protocol was evaluated in 49 anoestrous and lactating Bos taurus × Bos indicus
cows. Palpation per rectum and transrectal ultrasonography were used on Days –30, –20,
–10 and 0 (start of treatment) to confirm anoestrus but with the presence of follicles
alpha 10 mm, and every other day during treatment to determine ovarian activity. Cows were
randomly assigned to: (1) Ovsynch (n = 24; Day 0, 200 µg GnRH; Day 7, 150 µg PGF_2alpha; Day 9, 200 µg
GnRH + TAI 16 to 20 h later) and (2) control (n = 25; no treatment). Rates of ovulation
for the first GnRH injection, detection of a corpus luteum (CL) at PGF_2alpha injection,
pregnancy and induction of cyclicity were greater (P < 0.05) with Ovsynch. There was no
effect of body condition score (P > 0.05). In conclusion, the Ovsynch protocol was not
effective in obtaining acceptable pregnancy rate for TAI, but it was effective for
induction of cyclicity in anoestrous and lactating Bos taurus × Bos indicus cows
under tropical conditions.

Key words: Cattle, GnRH, induction of ovulation, Ovsynch, timed
artificial insemination

*Corresponding author: Dr. Felipe Montiel; E-mail: fmontiel@uv.mx;
fmontielp@hotmail.com; Fax: +52 (229) 9344053}