Poor reproductive response of anestrous Suffolk ewes to ram exposure is not due to failure to secrete luteinizing hormone acutely.

Minton, J. Ernest; Coppinger, T.; Spaeth, C. W.; Martín, Lourdes

doi:10.2527/1991.6983314x

Cited by 43 publications

(30 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…First, 97% of ewes responded to the GnRH test with a pulse of LH and in 93% of ewes, pulsatile secretion of LH was induced by the introduction of the rams regardless of breed or period of anoestrus, suggesting that the hypothalamo-pituitary axis is functional in anoestrus (Minton et al, 1991). The LH response to the GnRH test was greater in animals that went on to ovulate suggesting that this response may predict ovulatory outcome.…”

Section: Discussionmentioning

confidence: 99%

New insights into the influence of breed and time of the year on the response of ewes to the ‘ram effect’

Chanvallon

Sagot

Pottier

et al. 2011

Animal

View full text Add to dashboard Cite

Exposure of anoestrous ewes to rams induces an increase in LH secretion, eventually leading to ovulation. This technique therefore is an effective, low-cost and hormone-free way of mating sheep outside the breeding season. However, the use of this technique is limited by the variability of the ewes' responses. In this study, our objective was to understand more completely the origins of this variability and to determine the relative roles of breed, the point in time during anoestrus and the depth of anoestrus on the response to the 'ram effect'. In the first experiment, the pattern of anoestrus on the basis of the concentration of progesterone determined weekly, was determined in four breeds including two less seasonal (Mé rinos d'Arles and Romane), one highly seasonal (Mouton Vendé en) and one intermediate (Iˆle-de-France) breeds. Anoestrus was longer and deeper in Mouton Vendé en and Iˆle-deFrance than in Romane or Mé rinos d'Arles. In the second experiment, we used the same four breeds and tested their hypophyseal response to a challenge with a single dose of 75 ng gonadotrophin-releasing hormone (GnRH) in early, mid and late anoestrus, and then we examined their endocrine and ovarian responses to the 'ram effect'. Most (97%) ewes responded to GnRH and most (93%) showed a short-term increase in LH pulsatility following the 'ram effect'. The responses in both cases were higher in females that went on to ovulate, suggesting that the magnitude of the hypophyseal response to a GnRH challenge could be a predictor of the response to the 'ram effect'. As previously observed, the best ovarian response was in Mé rinos d'Arles at the end of anoestrus. However, there was no relationship between the proportion of females in the flock showing spontaneous ovulation and the response to the 'ram effect' of anoestrous ewes from the same flock.

show abstract

Section: Discussionmentioning

confidence: 99%

New insights into the influence of breed and time of the year on the response of ewes to the ‘ram effect’

Chanvallon

Sagot

Pottier

et al. 2011

Animal

View full text Add to dashboard Cite

show abstract

“…De acordo com Minton et al (1990), valores plasmáticos de progesterona inferiores a 1 ng/mL podem caracterizar as fases de estro ou de anestro, enquanto valores superiores a 3 ng/mL caracterizam a fase de diestro (luteal) ou gestação. A fase de anestro diferencia-se da fase de estro quando as concentrações de progesterona permanecem baixas por um período superior a dez dias.…”

Section: Groups With Different Superscripts Within the Same Columms Aunclassified

“…Níveis hormonais inferiores a 1 ng/mL por período superior a dez dias, as fêmeas eram consideradas em anestro (Minton et al, 1990). Devido à freqüência de colheitas para as dosagens de progesterona ter sido baixa, confrontaram-se os registros de detecção do estro pelos machos vasectomizados e os das dosagens plasmáticas de progesterona para cada animal.…”

Section: Introductionunclassified

Concentrações plasmáticas de progesterona em borregas lanadas e deslanadas no período de abril a novembro, no Estado de São Paulo

Sasa

Teston²,

Rodrigues

et al. 2002

R. Bras. Zootec.

View full text Add to dashboard Cite

RESUMO -Objetivou-se com este trabalho o fornecimento de informações sobre o padrão de secreção da progesterona (P 4 ) e as características de manifestação do ciclo estral em borregas lanadas e deslanadas, durante o período de abril a novembro, no Estado de São Paulo. Amostras de sangue foram coletadas da veia jugular de 12 borregas das raças Santa Inês (SI), Romney Marsh (RM) e Suffolk (SU), e as concentrações foram determinadas pelo método de radioimunoensaio utilizando-se kits comerciais. O estro foi detectado por machos vasectomizados (impregnados com tinta pó xadrez + óleo comestível na região peitoral) em 31 borregas (10 SI, 11 RM e 10 SU). O estro foi determinado pelo confronto da observação de fêmeas marcadas pelos machos vasectomizados e dos valores de concentrações plasmáticas de progesterona inferiores a 1 ng/mL. Os resultados mostraram que a maioria dos ciclos estrais foi de duração normal (14 -19 dias) para todas as raças. A duração dos ciclos de duração normal das borregas SU foi inferior aos das borregas SI e RM, as quais não diferiram entre si. Não houve diferença entre as raças na duração dos ciclos curtos (< 14 dias) e longos (20 -26 dias). O padrão de secreção de P 4 mostrou a presença de ciclos estrais múltiplos (27 -57 dias) indicando a incidência de ovulações silenciosas. As borregas SI encontravam-se em atividade cíclica reprodutiva apresentando valores que variaram de 0,08 a 7,36 ng/mL, enquanto que as raças RM e SU encontravam-se em atividade somente no período de abril a julho com valores que variaram de 0,13 a 7,05 ng/mL e de 0,15 a 7,30 ng/mL, respectivamente. De agosto a novembro, estas duas raças encontravam-se em anestro. Conclui-se que, em São Paulo, a raça SI não possui estacionalidade no ciclo reprodutivo como as raças RM e SU. Palavras-chave: ciclo estral, ovinos, progesterona, raças Plasma Concentrations of Progesterone in Hair and Wool Ewe Lambs from April toNovember, in São Paulo State ABSTRACT -The goal of this experiment was to provide information about the pattern of progesterone secretion (P 4 ) and on the oestrus cycle characteristics in hair and wool ewe lambs, from April to November, in São Paulo State. Blood samples from jugular vein were collected from 12 ewe lambs Santa Inês (SI), Romney Marsh (RM) and Suffolk (SU) breeds, and the concentrations were determined by radioimmunoassay method, using commercial kits. Oestrus was detected by using vasectomized rams (fitted with raddle crayons + comestible oil on pectoral area) in 31 ewe lambs (10 SI, 11 RM and 10 SU). The oestrus was determined by confronting the observation of marked females by vasectomized rams and values of plasma progesterone concentrations lower than 1 ng/mL. The results showed that the majority of oestrus cycles were of normal lenght (14 -19 days) for all breeds. The normal cycles lenght for the SU ewe lambs was shorter than SI and RM, which did not differ from each other. There was no difference for short (<14 days) and long (20 -26 days) oestrus cycles duration between the breeds. The pattern of P...

show abstract

“…Samples were then centrifuged at 3000 × g for 20 min, and serum was collected within 24 h and frozen at − 20ºC in plastic tubes. Progesterone concentrations in serum were determined in duplicate in a single assay for each experiment using the Coat-A-Count Progesterone RIA Kit (Siemens Healthcare Diagnostics, Inc., Los Angeles, CA, USA) as validated by Minton et al (1991). The assay was sensitive to 0.1 ng/ml progesterone; intra-and inter-assay coefficients of variation were 9.5% and 14.5%, respectively.…”

Section: Methodsmentioning

confidence: 99%

Strategies for rapid rebreeding of lactating ewes in the spring

Goff

Notter

Vanimisetti

et al. 2014

Animal

View full text Add to dashboard Cite

Rapid rebreeding of winter-and spring-lambing ewes is essential if ewes are to lamb more than once per year, but fertility of lactating ewes is often low and early weaning of lambs may be undesirable in forage-based production systems. Selection to improve fertility in spring matings has been successful and led to development of ewes with a reduced seasonal anestrus. Potential for rapid rebreeding of lactating out-of-season breeding (OOS) ewes was tested in three studies. In Experiment 1, effects of short-term lamb removal on rebreeding was evaluated over 2 years using 71 January-lambing OOS ewes. At an average of 63 days postpartum, 36 ewes had lambs removed for 72 h, and all ewes were joined with rams. Circulating progesterone levels indicated that 74% of ewes ovulated before lamb separation; 91% of ewes mated within 5 weeks of ram exposure, 85% were diagnosed as pregnant and 75% lambed. The average interval between lambings was 225 days. In contrast to results observed in cattle, none of the measured variables was affected by lamb separation ( P > 0.20). Experiment 2 compared rebreeding performance of 24 OOS and 23 St. Croix ewes that lambed in January and averaged 60 days postpartum at ram introduction. More OOS ewes ovulated, mated and became pregnant during the first 21 days of ram exposure (83.3%, 58.3%, and 41.7%, respectively; P < 0.001) compared with St. Croix ewes (26.1%, 0%, and 0%, respectively). After 39 days of ram exposure, pregnancy rates still favored OOS ewes (66.7% v. 39.1%; P = 0.06), but the percentage of ewes that lambed did not differ ( P > 0.20) between OOS (47.8%) and St. Croix ewes (34.8%). In the third study, 34 March-lambing OOS ewes were exposed to rams on May 3 at an average of 40 days postpartum to characterize their reproductive performance. After 39 days of ram exposure, 52.9 ± 8.7% of the ewes had mated, and 38.2 ± 8.5% were diagnosed as pregnant. However, only 20.6 ± 7.0% of the ewes produced viable lambs, suggesting a high level of uterine insufficiency. Spring fertility of lactating OOS ewes in these studies was one of the highest reported in the literature and indicated that selection for fertility in spring mating would improve reproductive performance in accelerated lambing programs. However, exposure of lactating OOS ewes to rams at 30 to 50 days postpartum was associated with high prenatal lamb mortality.

show abstract

Poor reproductive response of anestrous Suffolk ewes to ram exposure is not due to failure to secrete luteinizing hormone acutely.

Cited by 43 publications

References 5 publications

New insights into the influence of breed and time of the year on the response of ewes to the ‘ram effect’

New insights into the influence of breed and time of the year on the response of ewes to the ‘ram effect’

Concentrações plasmáticas de progesterona em borregas lanadas e deslanadas no período de abril a novembro, no Estado de São Paulo

Strategies for rapid rebreeding of lactating ewes in the spring

Contact Info

Product

Resources

About