Induction of fertile estrus during seasonal anestrus in ewes and fall born ewe lambs

Knights, M.

doi:10.33915/etd.1347

Cited by 3 publications

(18 citation statements)

References 189 publications

(518 reference statements)

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“…Several methods of inducing reproductive cycles in the anestrous ewe have been researched extensively and reviewed (Knights, 2001). Some of the approaches investigated include introduction of rams, treatment with P 4 in conjunction with introduction of rams, treatment with GnRH in conjunction with introduction of rams, manipulation of light, and treatment with melatonin.…”

Section: Management Methods That Can Induce Reproductive Cycles In Thmentioning

confidence: 99%

“…In addition to photoperiodic signals, many other factors, including breed and its geographic origin, individual genetics, age, and nutritional and lactational status, influence the duration and timing of the breeding season in ewes. These factors were discussed in detail in reviews by Whisnant and Inskeep (1992) and Knights (2001), and will be summarized briefly. The effects of lactation on seasonal reproduction will be discussed in detail in subsequent sections.…”

Section: Factors Affecting Length Of the Breeding Seasonmentioning

confidence: 99%

“…In anestrous ewes, E 2 is capable of inducing an LH surge within as little as 6 to 8 hours after treatment, but the average is nearer 18 hours. As noted by Knights (2001), responsiveness of follicles to gonadotropic stimulation is reduced in anestrous ewes, which may limit the synthesis of E 2 that can be attributed to ram-induced increases in the synthesis of gonadotropins. Additionally, Martin and colleagues (1986) observed that the period from introduction of rams to the LH surge (approximately 36 hours) is shorter than the normal follicular phase in cycling ewes.…”

Section: Introduction Of Ramsmentioning

confidence: 99%

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Approaches to improve the ovulatory response and reproductive performance of ewes introduced to rams during seasonal anestrus

Jordan¹

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Section: Management Methods That Can Induce Reproductive Cycles In Thmentioning

confidence: 99%

Section: Factors Affecting Length Of the Breeding Seasonmentioning

confidence: 99%

Section: Introduction Of Ramsmentioning

confidence: 99%

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Approaches to improve the ovulatory response and reproductive performance of ewes introduced to rams during seasonal anestrus

Jordan¹

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“…Seasonal anestrus is characterized by changes in both estrous activity and occurance of ovulation (reviewed by Knights, 2001). Ovulation rate at estrus follows a similar pattern as estrous cyclic activity, being highest during the breeding season, lowest when estrus is induced during anestrus, and intermediate during transitional periods (Dermody et al, 1970;Mallampati et al, 1971;Hulet et al, 1974;Hall et al, 1986).…”

Section: Seasonal Anestrusmentioning

confidence: 99%

“…The specific environmental cues and biological and endocrine responses for transition into anestrus have been reviewed (Whisnant and Inskeep, 1992;Knights, 2001;Goodman and Inskeep, 2006). Historically, lactating ewes have not responded to treatments for the induction of estrus that are effective in dry ewes during the anestrous season or in lactating ewes in the estrous season.…”

Section: Seasonal Anestrusmentioning

confidence: 99%

Effects of ovulation of aged follicles, pregnancy diagnosis by ultrasonography, and treatments during lactation on reproduction in ewes

Wurst¹

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Ewes are polyestrous and litter-bearing seasonal breeders. Although average ovulation rates are sufficient, many ovulations do not result in live offspring and ewes normally breed only once per year. As ovulation rate increases, so does the number of ovulations not represented by live births. When ultrasonographic analysis is limited to ovarian follicles that grow from 3 to 5 mm, follicular waves can be identified in sheep. In most cases, ovulatory follicle(s) develop from the ultimate follicular wave; however, ovulatory follicles can be derived from penultimate or earlier follicular waves. The relationship between lifespan of large follicles and fertility is controversial in sheep. In experiment 1, three approaches to create a model to compare fertility when ovulatory follicles developed from only the ultimate follicular wave or both ultimate and penultimate waves were tested. Ewes were treated on d 10 or 11 with 50 μg of GnRH i.m., the largest follicle(s) (≥ 4 mm) on each ovary were electrocauterized, or ewes were treated with 50 µg estradiol benzoate and 50 mg progesterone or 100 µg estradiol benzoate and 50 mg progesterone in attempts to induce follicular regression or luteinization. Corpora lutea were counted by ultrasound 7 days following estrus in order to verify ovulation of follicles that disappeared post estrus. Pregnancy was determined and embryos were counted 20 to 30 days following estrus. Neither treatment with GnRH nor estradiol and progesterone consistently caused regression or luteinization of ovulatory-sized follicles. Follicular ablation was successful in increasing the proportion of ovulations originating from the ultimate follicular wave in Dorset/Suffolk cross ewes, but did not alter the proportions of ovulations fom different waves in Polypay ewes. Average age of the ovulatory follicle was affected only in Dorset/Suffolk cross ewes. Due to lack of treatment effects, ovulatory follicles were evaluated regardless of treatment for effects on embryonic or fetal losses. Although loss tended to differ among follicular age combinations and wave sources of ovulatory follicles within ewes, older follicles did not have worse outcomes than younger follicles. Lactating ewes have not responded to treatments for the induction of estrus that are effective in dry ewes during the anestrous season. In experiment 2, lactating anestrous ewes 26 to 71 days postpartum were treated with either 25 or 50 mg progesterone/day for five days before ram introduction (RI). Twelve hours after RI, lambs were removed from half of the ewes in each group for 72 hours. Estrous response was recorded and ewes were scanned by transrectal ultrasonography on days 8 and 35 to 45 to determine ovulation rate, and pregnancy rate and number of embryos/fetuses, respectively. Number of lambs born was recorded at lambing. No effect of lamb removal was found for any variable examined. However, the lower dosage of progesterone reduced the mean time to estrus, increased the proportion of ewes ovulating, and decreased an incredible work ethic ...

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Male effect associated with suckling interruption on the reproductive performance of Santa Inês ewes

et al. 2015

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This study aimed to evaluate the effect of temporary suckling interruption associated with the male effect on reproductive performance of pluriparous Santa Inês ewes. The females were kept apart from the males for 60 days and then randomly distributed into three treatments associated with the male effect (DT0, DT24 and DT48); in DT0, there was no suckling interruption; in DT24, suckling was interrupted for 24 hours, and in DT48, sucking was interrupted for 48 hours. Estrous distribution was observed within 31 (DT0), 27 (DT24) and 38 (DT48) days of the breeding season. Estrous synchronization up to the 5th day of the mating season was observed in 15% (DT0), 30% (DT24) and 25% (DT48) of the females, with no difference among treatments. Estrous percentages were 90% (DT0), 100% (DT24) and 100% (DT48), with no difference among treatments. Pregnancy rates were 38.4% (DT0), 60.0% (DT24) and 45.0% (DT48) with no difference among treatments. Prolificacy was 1.43 (DT0), 1.17 (DT24) and 1.22 (DT48) and did not differ between treatments. In conclusion, temporary suckling interruption associated with the male effect is efficient to induce estrous but not to synchronize estrous or increase the pregnancy rates and prolificacy of Santa Inês ewes during a 45-day breeding season.Keywords: anestrous, biostimulation, reproduction, sheep. EFEITO MACHO ASSOCIADO AO DESMAME TEMPORÁRIO NO DESEMPENHO REPRODUTIVO DE OVELHAS SANTA INÊSRESUMO: O estudo teve como objetivo avaliar o efeito do desmame temporário associado ao efeito macho sobre o desempenho reprodutivo de ovinos Santa Inês. As fêmeas foram mantidas distantes dos machos por 60 dias e aleatoriamente distribuídas em três tratamentos associados ao efeito macho (DT0, DT24 e DT48), no qual em DT0, não houve interrupção da amamentação; em DT24, amamentação interrompida por 24 horas e em DT48, interrupção da amamentação por 48 horas. Distribuição de estro foi observada em 31 (DT0), 27 (DT24) e 38 (DT48) dias da estação de monta. Sincronização de estro até o quinto dia da estação de monta foi observada em 15% (DT0), 30% (DT24) e 25% (DT48) das fêmeas, não havendo diferença entre os tratamentos. Percentagens de estro foram de 90% (DT0), 100% (DT24) e 100% (DT48), não havendo diferença entre os tratamentos. As taxas de prenhez foram de 38,4% (DT0), 60,0% (DT24) e 45,0% (DT48), sem diferença entre os tratamentos. A prolificidade foi de 1,43 (DT0), 1,17 (DT24) e 1,22 (DT48), e não diferiu entre os tratamentos. Em conclusão, o desmame temporário associado ao efeito macho é eficiente na indução do estro, embora não seja eficiente na sincronização de estros e não aumente as taxas de gestação e prolificidade das ovelhas Santa Inês durante uma estação de monta de 45 dias.Palavras-chave: anestro, bioestimulação, ovinos, reprodução.

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Induction of fertile estrus during seasonal anestrus in ewes and fall born ewe lambs

Abstract: Role in display of behavioral estrus. Role in maintenance of the induced CL in anestrous. Role in the induction of gonadotropin secretion Types of progestogens Methods of progestogen administration Duration of progestogen treatment Dosage of progestogen required

Cited by 3 publications

References 189 publications

Approaches to improve the ovulatory response and reproductive performance of ewes introduced to rams during seasonal anestrus

Approaches to improve the ovulatory response and reproductive performance of ewes introduced to rams during seasonal anestrus

Effects of ovulation of aged follicles, pregnancy diagnosis by ultrasonography, and treatments during lactation on reproduction in ewes

Male effect associated with suckling interruption on the reproductive performance of Santa Inês ewes

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