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XXXVIII Annual Meeting of the EAAP, Lisboa. Vol. II, p. 732 (1987)
THE EFFECT OF CALVING SEASON ON THE DURATION OF POSTPARTUM ANOESTRUS IN ALENTEJANO BEEF COWS

J. Robalo Silva, A.E.M. Horta, M. Irene Vasques, R.M. Leitão and D. Cláudio
Departamento de Reprodução, EZN-INIA
2000 Vale de Santarém, Portugal

One hundered and eighty three Alentejano beef cows were checked for the duration of postpartum anoestrus during the January-March (Group A) and August-October (Group B) calving seasons, over a two year study. Based on progesterone profiles, the mean interval from parturition to the onset of ovarian cyclic activity was (mean ± sd) 53.9 ± 28.8 and 92.1 ± 38.9 days for cows from goup A that calved in 1984 (n=36) and 1985 (n=71), respectively, and 26 ± 10.6 and 30.3 ± 13.6 days for cows from group B that calved in 1984 (n=13) and 1985 (n=55), respectively. Cows that calved in late Summer/Autumn resumed postpartum ovarian activity significantly sooner than cows calving in Winter/early Spring (P< 0.01). The interval from parturition to the longest day of the year was significantly correlated with postpartum anoestrus in group A (r=0.41, P< 0.01), as it was the interval from the longest day to parturition with postpartum anoestrus in group B (r=0.30, P< 0.05).
Reproductive performance was assessed during the period from mating to pregnancy diagnosis by rectal palpation at 45 to 60 days after service (mating seasons were in April/May and November/December for groups A and B, respectively). During a 60 days mating period, the percentage the percentage of served cows in 1984 was 91.5 and 87.5 in groups A and B, respectively, with correspondent conception rates (by 45-60 days post-mating) of 71.9% and 83.3%, respectively. In 1985, there were 67.6% and 74.19% of served cows in groups A and B, respectively, with correspondent conception rates of 89.6% and 87%. Fertility ((calved cows / cows to be mated) x 100) was lower in Spring (63.9% and 57.8% in 1984 and 1985, respectively) than in the Autumn (76.9% and 62.9% in 1984 and 1985, respectively). The lower fertility observed in group B/1985 was mainly due to 11.3% of the calved cows failing to cycle before the end of matings. The same was evident in group A in 1985, where there were 28.2% acyclic cows till the end of matings, except that they were pluripara.
The results above show that Winter/Spring calving season decreases ability for cows to resume their ovarian activity after parturition, which can account for a lower fertility when a calf/year/cow in an extensive pasture model is aimed for this breed. Conception rates by 45-60 days post-mating did not appear to be influenced by seasonal factors.


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Jornadas Hispano-Lusas sobre Producción de Carne de Vacuno en Regimen Extensivo, Salamanca, 26-28 Nov. (1987)
PERFORMANCE REPRODUTIVA EM BOVINOS DA RAÇA ALENTEJANA. COMPARAÇÃO ENTRE DUAS ÉPOCAS DE COBRIÇÃO.

António E. M. Horta
Departamento de Fisiologia e Reprodução Animal,
Estação Zootécnica Nacional - INIA
Vale de Santarém, 2000 SANTARÉM, PORTUGAL


São apresentados os resultados de experiências realizadas ao longo de três anos sucessivos, sobre a duração do anestro puerperal e índices reprodutios de vacas da raça Alentejana. Em cada ano consideraram-se duas épocas de parto (Janeiro-Março e Agosto-Outubro) às quais corresponderam duas épocas de cobrição natural (em Abril e Maio e em Novembro e Dezembro). Os resultados destes trabalhos, relativamente a anos específicos, foram já apresentados noutras fontes (ROBALO SILVA et al., 1987; HORTA et al., 1987).
Os animais encontraram-se sujeitos a um regime de pastoreio permanente, e o início da actividade cíclica do ovário após o parto foi determinada pelos teores da progesterona plasmática sanguínea (RIA) usando colheitas semanais.
Os resultados do conjunto dos três anos de estudo, englobando um total de 290 partos confirmam a existência de variações sazonárias do comportamento reprodutivo inicialmente evidenciadas para a raça por MASCARENHAS et al. (1986). Assim, nas vacas pluríparas com partos de Inverno, a duração do anestro puerperal é significativamente superior ao das paridas no Verão (73,96 ± 36,45 dias vs 33,08 ± 16,45 dias, respectivamente; P< 0,001). Nas vacas primíparas aquele valor foi também significativamente superior na época de Inverno relativamente à época de Verão (111,07 ± 38,98 dias vs 35,64 ± 19,69 dias, respectivamente; P< 0,001). A diferença entre primíparas e pluríparas dentro da mesma época foi significativa nos animais paridos no Inverno (P< 0,001). Em 111 animais, o peso ao parto foi significativamente inferior na época de Inverno, quer nas pluríparas quer nas primíparas (565,83 ± 65,97 Kg vs 642,83 ± 65,28 Kg e 435,77 ± 41.51 Kg vs 577 ± 59.01 Kg, respectivamente; P< 0,001). Regressões univariadas entre o anestro puerperal e o peso ao parto ou a distância entre o parto e o solstício de Junho (21/6), foram realizadas para as primíparas e pluríparas. As duas variáveis independentes (X1=peso ao parto e X2=distância do parto ao dia 21/6), foram seleccionadas por "stepwise" para integrarem uma equação de regressão linear múltipla (Y = 162,17 - 0,222.X1 + 0,316.X2; P< 0,001), tendo o anestro como variável dependente. A equação anterior permite explicar parcialmente (coeficiente de determinação = 41,36%) a diferença significativa observada entre épocas para a duração do anestro pós-parto, através do peso ao parto (menor peso = anestro mais longo) e da distância do parto ao solstício de verão (maior distância a 21/6 = anestro mais longo). Estes resultados estão de acordo com as observações feitas para outras raças de carne em latitudes superiores (PETERS e RILEY, 1982a; 1982b; MONTGOMERY et al., 1985).
Duma forma geral, a taxa de fertilidade foi sensivelmente inferior na época de cobrição da Primavera, facto que se ficou a dever a um anestro puerperal mais longo, não se evidenciando diferenças entre épocas relativamente à capacidade de fecundação dos animais cíclicos.


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V Jornadas Internacionales en Reproducción e I.A. (Ponencias y comunicaciones no incluidas n los tomos I y II), Asociación Española de Especialistas en Reproducción Animal, Inseminación Artificial e Nuevas Tecnologias, Zaragoza - Espanha, pp. 51-69. (1990)
INÍCIO DA ACTIVIDADE OVÁRICA PÓS-PARTO NA VACA ALENTEJANA: INFLUÊNCIA DE ÉPOCAS DE PARIÇÃO E DE ANOS DIFERENTES

A.E.M. HORTA, M. Irene VASQUES, R.M. LEITÃO, J. ROBALO SILVA
Departamento de Fisiologia e Reprodução Animal,
Estação Zootécnica Nacional - Instituto Nacional de Investigação Agrária,
Vale de Santarém 2000, Portugal

A actividade ovárica pós-parto (PP) da vaca Alentejana em regime de pastoreio extensivo, foi estudada através de análises de progesterona plasmática pelo método de radioimunoanálise (RIA). A duração da aciclia ovárica PP foi comparada entre vacas parindo em duas épocas diferentes (Janeiro-Março e Agosto-Outubro). Diferenças entre vacas primíparas e pluríparas, interrupção temporária do aleitamento (72 horas ao 20º dia PP) e o peso das mães ao parto, foram também considerados relativamente à sua influência sobre o reinício da actividade ovárica. A fertilidade após duas épocas de cobrição natural (Abril-Maio e Novembro Dezembro), foi igualmente estudada. A aciclia ovárica PP foi significativamente superior após a estação de partos de inverno do que após a do verão, quer em vacas pluríparas quer nas primíparas (74 vs 33,1 e 111,1 vs 35,6 dias, respectivamente; P< 0,001). As vacas primíparas demoraram significativamente mais tempo para reiniciarem a sua actividade ovárica do que as pluríparas durante a época invernal (P< 0,001). A estação do ano interagiu com a paridade, relativamente à duração da inactividade ovárica pós-parto (P< 0,0001). O peso vivo das vacas na altura do parto foi significativamente inferior durante a estação de inverno, nas primíparas e pluríparas (435,8 vs 577 Kg e 565,8 vs 642,8 Kg, respectivamente; P< 0,001). A interrupção temporária do aleitamento resultou em períodos de anestro PP mais curtos somente durante a época de verão (30,1 vs 39 dias; P< 0,05). O peso vivo ao parto (PVP) e o intervalo entre o parto e o dia 21 de Junho (P-21J), mostraram-se significativamente correlacionados com a duração da inactividade ovárica pós-parto (Y = 162,17-0,222*(PVP)+ 0,316*(P-21J); r²=0,41; P< 0,03). As vacas paridas no inverno mostraram variações significativas na duração do anestro entre anos diferentes, relacionando-se este fenómeno com as condições nutritivas dos animais sob influência pluviométrica. Devido a um anestro pós-parto muito longo, a fertilidade durante a época de primavera foi inferior à do outono durante três dos anos estudados (63,9 vs 76,9%, 57,8 vs 62,9% e 36,5 vs 60,6%, respectivamente em 1984, 1985 e 1986). Os resultados apresentados aqui, mostram que a estação de partos de inverno atrasa o início da actividade ovárica subsequente, nesta raça e nas nossas condições, diminuindo consequentemente a fertilidade. O efeito sazonário parece estar associado a uma diminuição da disponibilidade alimentar durante o inverno. A interrupção temporária do aleitamento encurta o período de aciclia somente durante a época de verão. As vacas primíparas durante a época de inverno, precisam de um período significativamente mais longo para reciclarem a função ovárica do que as pluríparas.
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* · Trabalho realizado com o apoio do Instituto Nacional de Investigação Agrária (Portugal) e a Agência ·Internacional de Energia ·Atómica ·(IAEA, Viena, Austria) sob o contracto de investigação No. 3259/RB. Parte deste trabalho foi originalmente publicado em língua inglesa pela IAEA.


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12th INT. CONG. ANIM. REPROD., The Hague, The Netherlands, 23-27 Aug, poster 267, pp. 895-897. (1992)
EFFECT OF INDUCING CALVINGS ON CALF BIRTH WEIGHT (1)

A.E.M. Horta, C.M. Marques, M.I. Vasques and R.M. Leitão
Estação Zootécnica Nacional, Vale de Santarém 2000, Portugal


Thirty eight Alentejano (AL) pregnant beef cows carrying 20 ALxAL calves from A.I. and 24 crossed calves from IVM-IVF embryo transfer (ET) were allowed to calve naturally (NC). Seventeen AL cows (IC) carrying 13 ALxAL calves from A.I. and 8 crossed calves from IVF-IVM embryo transfers were induced to calve as follows: Group IC-I (n=8) receiving implants containing 3 mg of norgestomet in both ears, 3 mg of norgestomet + 5 mg of oestradiol benzoate IM, 25 mg of PGF2alpha IM and 45 mg of dexametasone, on day 256 of gestation; group IC-II (n=9) receiving the same treatment on day 264. Implants were removed on days 264 and 268 in groups IC-I and IC-II, resulting in a retention period of 7 and 4 days, respectively.
The NC groups of cows produced 15 sets of twins (39.5%) vs 4 sets of twins (23.5%) in the IC group. Single and twin ALxAL calves were significantly lighter in IC vs. NC group (27.75 vs. 38.5 Kg, and 23.4 vs. 32.3 Kg respectively for singles and twins; P< 0.001). In both NC and IC groups, single calves were significantly heavier than twins (more 6.2 and 4.35 Kg respectively; P< 0.001). Gestation length was significantly reduced in IC vs. NC cows (266.25 vs. 287.75 days and 266.8 vs. 281.08 days, respectively for single and twin carrying cows; P< 0.001). Single gestations were significantly longer than twin ones in NC group of cows (P< 0.001). In the IC-I group, 3 out of 8 cows calved before the day of implant removal (mean gestation length = 264.78 days; range = 263 - 268 days). In the IC-II group, 7 out of 9 cows calved within 48 hours next to implant removal, the two remaining cows calving by 72 and 96 hrs after. In the IC group, calves born from ET (crossbred) presented a stillborn rate of 26.7% and 27.6% for singles and twins, respectively. No calf mortality was observed in the IC group due to problems related with early calving induction or calf birth weight either in IA or ET produced calves.

(1) Research granted by the EEC-ECLAIR contract nr. AGRE 018




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Jornadas Internacionais sobre Reprodução Ovina e Caprina, SPRA / SPOC, Évora. pp. 129-140. (1991)
PRODUÇÃO DE SOROS ANTI-EMBRIÃO PARA DIAGNÓSTICO PRECOCE DE GESTAÇÃO EM OVINOS

Rosa Lino Neto Pereira (1), A.E.M. Horta e R.M. Leitão
(1) Escola Superior Agrária de Beja
Departamento de Reprodução Animal-EZN-INIA Vale de Santarém, 2000 Santarém

O trabalho realizado teve por principal objectivo a produção de soros de coelho anti-embrião ovino, para desenvolver um método imunológico de diagnóstico precoce de gestação em ovinos.
Procedeu-se à sincronização, superovulação e cobrição de 13 ovelhas, sendo recolhidos 22 embriões por método cirúrgico. Estes embriões, após homogenização, foram utilizados na imunização de coelhos e num teste de imunodifusão em gel. Os anti-soros obtidos foram adsorvidos com homogenados de fígadoe rim de ovelha não gestante (FR) e, posteriormente, com FR e glóbulos vermelhos e góbulos vermelhos lavados de carneiro (FRG) para remoção de anti-corpos inespecíficos da gestação.
No teste de imunodifusão em gel só aparecem linhas de precipitação entre o homogenado de embriões (AG) e e anti-soros não adsorvidos.
Para diagnóstico de gestação foram sincronizadas e cobertas 20 ovelhas e realizados doseamentos de progesterona no plasma por RIA em D0 e D16, e testes de hemaglutinação em D0, D4, D8, D16 e D50 usando soluções a 2% de glóbulos vermelhos (GV) lavados dessas ovelhas e os vários anti-soros de coelho adsorvidos com FRG.
As leituras com hemaglutinação detectadas pouco diferiram entre ovelhas gestantes (concentrações plasmáticas de progesterona (P4) >0,5 ng/ml em D16) e não gestantes (P4<0,5 ng/ml em D16).
O teste de hemaglutinação desenvolvido não detectou a presença de antigénios específicos da gestação nos GV das ovelhas gestantes. As leituras positivas obtidas podem reflectir a recolha de proteínas específicas da fêmea, presentes no útero juntamente com os embriões, e cujos anti-corpos produzidos pelos coelhos não foram adsorvidos, dada a utilização de GV de carneiro e não de ovelha na técnica de adsorção praticada.


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Rev. Port. Ciênc. Veter., 77: 215-230. (1982)
REPRODUCTIVE CYCLE SYNCHRONIZATION IN A PORTUGUESE DAIRY HERD

A.E.M. Horta and C.M.S.G. Costa*
Department of Animal Reproduction, EZN, Vale de Santarém 2000, Portugal *Departamento de Regadio da Herdade da Fataca-INIAER

Results of two methods of reproductive cycle synchronisation of a portuguese dairy herd (n=42) on two consecutive years with PGF2 alpha, are presented.
In order to achieve synchronisation between both grass and lactation growing curves, the authors sought for a batch of cows calving during June and July.
Conception rates at first AI (pregnant cows:treated cows):100 were, 76.1% and 70,7% in 1980 and 1981, respectively.
It is concluded that artificial insemination fulfilled at induced oestrus, after the first PGF2alpha injection, contributed to the obtained success.


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Rev. Port. Ciênc. Veter., 78: 277-289 (1983)
PROSTAGLANDINS AND PLACENTAL RETENTION IN COWS: A REVIEW.

A.E.M. Horta
Department of animal Reproduction - EZN, Vale de Santarém, 2000, Portugal

The dynamic synthesis of prostanoids by uterine, placental and fetal tissues at parturition, as well as the role of these compounds in the mechanism of the first and second stages of labour is discussed after a a brief review on actual names and synthesis pathways of prostaglandins.
The effect of prostaglandins in the separation and expulsion of the placenta in the cow is reviewed on the light of data obtained by the author and published elsewhere. In this particular it is suggested that during the third stage of labour, prostaglandins interfere directly on placental separation at the placentome level, as it is shown by the positive trend of PGF2alpha and the negative effect of PGE2 upon the mechanism of placental detachment.


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Zootechnia, 33: 39-48 (1984)
[Effects of prostaglandins E2 and F2alpha on placental retention induced by lysine acetil-salycilate in dairy cows].

A.E.M. Horta
Department of animal Reproduction - EZN, Vale de Santarém, 2000, Portugal

Twenty three dairy cows were randomly assigned to the following treatments: Placebo (n=7); lysine acetil-salycilate, an inhibitor of cyclooxigenase (LAS, 20 gr iv, n=5); LAS (20 gr iv) + PGE2 (5 mg i.u., n=5); and LAS (20 g iv) + PGF2alpha (25 mg im, n=6). All but two animals were submitted to uterine contractions measurements by tocographic records during the 6th hour after calving. Treatments above were administered twice: immediately after calf delivery and half past five hours later.
LAS treatment alone induced placental retention (PR) in all animals (P< 0.01), tocographic records showing a significant decrease on uterine contractions amplitude mean values (18.72 ± 4.96 vs. 39.79 ± 6.56 mm Hg) relatively to the Placebo group (P< 0.05). PGE2 treatment potentiated the effect of LAS on PR measured at 48h postpartum (P< 0.02) although similar patterns of uterine contractions relative to Placebo were found (P>0.05). PGF2alpha could prevent placental retention on 50% of the treated cows in spite of a significant decrease in the amplitude of uterine contractions induced by LAS being detected relatively to the Placebo group (25.29 ± 5.55 vs 39.79 ± 6.56 mm Hg; P< 0.05).
The results above suggest that: 1) - The process of placental separation/expulsion in the cow seems to depend on a balanced synthesis of prostaglandins during the 3rd stage of labour; 2) - Placental retention is not necessarily acompanied by a decrease of the strenght of uterine contractions; 3) - Factors favouring an imbalance on prostaglandins bio-synthesis leading to an increase of PGE2 and a decrease on PGF2alpha early after calving, may lead to placental retention in bovine.


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Anim. Reprod. Sci., 10: 251-259 (1986)
SEASONAL VARIATION IN THE OVARIAN ACTIVITY OF BEEF COWS ASSESSED BY MONITORING PROGESTERONE CONCENTRATIONS

R.D. Mascarenhas, M.I.A.M. Rios Vasques, A.E.M. Horta, J. Robalo Silva and A.V. Portugal
Department of Animal Reproduction, EZN, Vale de Santarém, 2000, Portugal

Ovarian activity assessed for over a year in 16 beef cows, 10 of the Alentejano and 6 of the Mirandes breeds, by measuring plasma progesterone twice weekly. It was observed that there were acyclic cows from January to the end of May and from the end of August to the end of September. The gratest number of acyclic cows (3 out of 16) was observed in April. Progesterone determinations showed that after the period of acyclia there was a small short-lasting increase in progesterone, then a cycle with a short dioestrus followed by cycles of normal duration. Oestrous cycles were on average 23.16 ± 0.16 days long; the difference between breeds was not significant. The duration of cycles throughout the year was statistically different (P< 0.05) betwen months. Minimum and maximum values were observed in March (21.5 ± 0.6 days) and December (25.05 ± 0.58 days) respectively.


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Theriogenology, 25: 291- 301 (1986)
POSSIBILITY OF REDUCING THE LUTEOLYTIC DOSE OF CLOPROSTENOL IN CYCLIC DAIRY COWS

A.E.M. Horta, C.M.S.G. Costa*, J. Robalo Silva, M.I. Rios Vasques
Department of Animal Reproduction, EZN, Vale de Santarém 2000, Portugal *Departamento de Regadio da Herdade da Fataca-INIAER

The administration of cloprostenol by intravulvosubmucous (i.v.s.m.) injection at 1/2 and 1/4 of the dose usually given by intramuscular (i.m.) injection, was tested in dairy cows for luteolysis and estrus synchronization. The i.m. injection was used in ten adult cows at the usual dose of 500 ug/animal. Eleven adult cows and 11 heifers were treated i.v.s.m. with a dose equivalent to 250 ug/animal and 125 ug/animal, respectively. Two injections of cloprostenol were administered 11 days apart to the cows not detected in oestrus after a single injection. Forty-three out of the total 46 animals were detected to be in dioestrus at the time of at least one of the injections, as reflected by the plasma progesterone concentrations at the time of treatments.
Three out of the 43 animals injected during dioestrus were refractory to the luteolytic effect of cloprostenol; this appeared to be independent of the dosage and route of administration (refractory cows were: one adult cow treated i.m. and two treated i.v.s.m. with 125 ug of cloprostenol). The mean time interval from injection to the onset of heat was 82.8 hours with a confidence limit for 95% of probability between 67.9 hours and 92.7 hours. The difference between treatments was not significant.
The results suggest that in heifers and adult cows cloprostenol can be given i.v.s.m. route at a reduced dose of 1/4 of the usual 500 ug i.m. dosage without affecting the luteolytic effect of the drug or fertility.


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Annales de Recherches Vétérinaires, 17: 395-399 (1986)
PROSTAGLANDIN F2 ALPHA AND PROSTACYCLIN IMBALANCE IN COWS WITH PLACENTAL RETENTION: NEW FINDINGS.

A.E.M. Horta*, Michelle Chassagne and M. Brochart
*Department of Animal Reproduction, EZN, Vale de Santarém 2000, Portugal Laboratoire D'Éco-Pathologie, CRZV-INRA Theix, 63122 Ceyrat, France

The aim of this work was to investigate possible differences in peripheral blood concentrations o 13,14 dihydro 15 keto PGF alpha (PGFM) and 6 keto PGF1 alpha (PGIM), between dairy cows retaining (RP) and not retaining (NRP) their placenta. Blood samples wee collected 5, 30 and 60 minutes postpartum from 8 RP and 17 NRP cows.
PGFM concentrations were significantly lower in RP than in NRP cows 60 minutes after birth (8156 pg/ml vs. 12016 pg/ml; P< 0.05). There was a significant rise of PGFM levels between 30 and 60 minutes in NRP cows (6225 pg/ml vs. 12016 pg/ml; P< 0.01), while in RP cows PGFM remained fairly constant along the period studied. No significant differences were found between RP and NRP cows regarding PGIM levels during this period although absolute values were slightly higher in RP cows. The PGFM/PGIM ratio was significantly higher at 60 minutes postpartumin NRP cows than in RP cows (15.5 vs 8.8; P< 0.01). This ratio increased significantly in NRP cows between 30 and 60 minutes (7.2 vs 15.5; P< 0.01), a pattern not observed in RP cows. There was no correlations between PGIM and PGFM levels during the first 60 minutes postpartum in the NRP cows. However, the same correlation was significantly positive in the RP cows (r=0.75; P< 0.01).
The above results suggest that the synthesis of PGF2 alpha betwwen 30 and 60 minutes postpartum is significantly decreased in cows with placental retention as reflected by the levels of PGFM. They further suggest that prostacyclin synthesis in cows not retaining their placenta does not increase during the first 60 minutes postpartum, as it does in cows with placental retention as reflected by the positive correlation between the levels of PGIM and PGFM found in these animals during the same period. It is proposed that an imbalance in the synthesis of PGF2 alpha and a relative increase in PGI2 is associated with placental retention in bovine.


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