Reproductive changes in a cyclic population of snowshoe hares

2001 ◽  
Vol 79 (11) ◽  
pp. 2101-2108 ◽  
Author(s):  
Carol I Stefan ◽  
Charles J Krebs
Keyword(s):  
Pregnancy Rate ◽  
Breeding Season ◽  
Litter Size ◽  
Reproductive Output ◽  
Yukon Territory ◽  
The Body ◽  
Decline Phase ◽  
Snowshoe Hares ◽  
Early Increase ◽  
Changes In Pregnancy

Reproductive output was estimated for a cyclic population of snowshoe hares (Lepus americanus) in the Kluane Lake region of the southwest Yukon Territory. Data collected by five researchers were collated over 8 years (1989–1996). Pregnant hares were captured and held in cages until they gave birth so that reproductive characteristics could be measured. Pregnancy rate, litter size, and neonate size fluctuated significantly throughout the cycle, changes occurring about 2 years before corresponding changes in density. Pregnancy rates were nearly 100% early in the breeding season, but declined up to 20% in the last gestation periods of the year. The number of litters produced in a breeding season varied between two (decline phase) and four (low, early increase phase). Litter size varied among years as well as among litters within a year, larger litters being born later in the breeding season. The body mass and size of newborn hares varied by 5–33% among years. The combined changes in pregnancy rate and litter size resulted in a cyclic change in total reproductive output ranging from a low of 6.9 young per female during the decline phase to a maximum of 18.9 during the second year of the low and early increase phases.

Reproductive change in the 10-year cycle of snowshoe hares

1979 ◽  
Vol 57 (2) ◽  
pp. 375-390 ◽  
Author(s):  
John R. Cary ◽  
Lloyd B. Keith
Keyword(s):  
Pregnancy Rate ◽  
Litter Size ◽  
Weight Change ◽  
Ovulation Rate ◽  
Population Cycle ◽  
Snowshoe Hare ◽  
Cyclic Variation ◽  
Reproductive Parameters ◽  
Snowshoe Hares ◽  
Hare Population

Reproduction was monitored during a 16-year study of snowshoe hare (Lepus americanus) populations near Rochester, Alberta. Pregnancy rate, ovulation rate, and litter size changed markedly between successive litters within the breeding season; these parameters were thus further categorized by litter in our analyses. Most reproductive components varied significantly between years; a significant '10-year' periodicity was the dominant source of this variation. The cyclic fluctuations of reproductive parameters were broadly synchronous and tended to precede the population cycle by about 3 years, thereby producing a range in potential natality annually of 7.5 to 17.9 young per female. The year-to-year variability of pregnancy rate, ovulation rate, and litter size was markedly larger in the later litters than in the early ones. Paunched weight, mean age, incidence of endoparasites, liver and spleen weights, and midwinter-to-spring weight change also possessed significant 10-year cycles; paunched weight cycled directly with the hare population, but the others cycled either directly with or counter to reproduction. We believe that the correspondence between midwinter-to-spring weight change and reproduction implicates winter nutrition as the primary cause of the cyclic variation. Onset of spring accounted for a significant amount of variability in onset of breeding, adding to that due to the periodic change.

scholarly journals Comparison of sexual performance and testicular characteristics of melatonin treated Kivircik and Charollais rams during the non-breeding season

2017 ◽  
Vol 69 (2) ◽  
pp. 278-284
Author(s):  
M. Cevik ◽  
C. Yilmazer ◽  
A. Kocyigit
Keyword(s):  
Ambient Temperature ◽  
Pregnancy Rate ◽  
Breeding Season ◽  
Litter Size ◽  
Reproductive Performance ◽  
Slow Release ◽  
Experimental Period ◽  
Day Length ◽  
Sexual Performance ◽  
Estrus Response

ABSTRACT This study was conducted to investigate the effects of melatonin implantation on basic testicular characteristics and reproductive performance of Kivircik and Charollais rams and ewes during the non-breeding season. In this study, 8 Kivircik and 6 Charollais rams were used. Rams were implanted with 54 mg melatonin according to the manufacturer's instructions. At melatonin implantation and at ram introduction the reproductive performance and testicular characteristics were evaluated. Throughout the experimental period, rams were permanently kept outdoors under conditions of natural day length and at ambient temperature. The effects of exogenous melatonin treatments on the reproductive performances of rams and ewes, estrus response, pregnancy rate, litter size and twinning rate of ewes were evaluated in all groups. Libido values were significantly higher in Charollais rams compared to Kivircik rams (P<0.001). Testicular volume (TV) was increased in both ram breeds. Scrotal length (SL) was also increased in both Kivircik and Charollais rams (P<0.01). In conclusion, we showed that the treatment of rams with slow release melatonin implants increased scrotal diameters and testicular volumes in both Kivircik and Charollais rams. Furthermore, melatonin implantation improved the reproductive performances of ewes naturally mated with these melatonin implanted rams during non-breeding season.

scholarly journals Effect of barium selenate injections on fertility of Pirlak ewes subjected to estrus synchronization during non-breeding season

2017 ◽  
Vol 73 (8) ◽  
pp. 479-482 ◽  
Author(s):  
Mushap Kuru ◽  
Osman Sogukpinar ◽  
Mustafa Makav ◽  
Nebi Cetin
Keyword(s):  
Pregnancy Rate ◽  
Breeding Season ◽  
Litter Size ◽  
Chorionic Gonadotropin ◽  
Conception Rate ◽  
Transrectal Ultrasonography ◽  
Estrus Synchronization ◽  
Equine Chorionic Gonadotropin ◽  
Synchronization Protocol ◽  
Lambing Rate

This study was aimed at determining the effect of barium selenate injections on the fertility of Pirlak ewes which had been subjected to progesterone-assisted estrus synchronization during the non-breeding season. A total of 150 Pirlak ewes between the ages of 2 and 5 years were used in the study. Sponges containing progesterone were inserted into the vaginas of the ewes for 11 (groups I and III) or 14 days (groups II and IV) for the purpose of estrus synchronization, and 500 IU equine chorionic gonadotropin (eCG) was administered on the day of sponge removal. In addition, barium selenate was injected s.c. immediately before estrus synchronization protocol in groups I and III. After the sponges had been removed, estrus was observed for four days. The ewes were mated with fertile rams. The pregnancy was determined by transrectal ultrasonography 30 days after mating. It was observed that the estrus rate, pregnancy rate, conception rate, lambing rate, twinning rate, and litter size were not statistically different (P > 0.05) between the groups, but estrus onset was different (P < 0.001). In conclusion, barium selenate injections did not affect the fertility parameters before progesterone-assisted synchronization was applied to the Pirlak ewes during the non-breeding season

scholarly journals 142 Reproductive performance of land race hair sheep ewes in different breeding seasons under a semi-continuous production

2020 ◽  
Vol 98 (Supplement_2) ◽  
pp. 76-76
Author(s):  
Stephan Wildeus ◽  
Dahlia O’Brien
Keyword(s):  
Pregnancy Rate ◽  
Litter Size ◽  
Production System ◽  
Continuous Production ◽  
Transrectal Ultrasound ◽  
Late Gestation ◽  
Production Cycle ◽  
Hair Sheep ◽  
Mating Period ◽  
Lamb Survival

Abstract A system for semi-continuous lamb production was evaluated using Barbados Blackbelly and St. Croix hair sheep ewes under 8-mo accelerated mating. Ewes were managed in a forage-based production system using rotational grazing. Two flocks of ewes (n = 30–35), equally representing the breeds, were bred 4 mo apart. Ewes were synchronized by feeding melengestrol acetate for 10 d, and mated in two single sire groups to like breed sires in November (NOV), March (MAR), and July (JUL) in a 25-d mating period. Pregnancy was recorded by transrectal ultrasound 22 d after breeding. Ewes were supplemented with corn/soybean meal during late gestation (0.75% of BW) and during lactation (1.5% of BW). They lambed on pasture with limited supervision, and lambs were weaned at 2 mo of age. Lambs had access to the supplement provided to ewes. Ewe performance (pregnancy rate, litter size, lamb survival, and birth and weaning weight) was recorded during a 2 yr production cycle, and analyzed for the effect of mating season. Pregnancy rate was not statistically different (P &gt; 0.1) between season, and ranged from 93.9% in NOV, to 85.9 and 86.6% in MAR and JUL. Litter size (lambs born/ewe lambing) was higher (P &lt; 0.05) in NOV (2.09) than MAR (1.68) and JUL (1.82). Lamb survival at birth was reduced (P &lt; 0.001) in JUL (86.5%) compared to NOV (99%) and MAR (100 %), but was not different between seasons for survival to weaning (86 to 90%). Lamb birth weights were higher (P &lt; 0.05) in MAR (3.16 kg) than JUL (2.99 kg), with NOV (3.05 kg) intermediate, while lamb weaning weights were higher (P &lt; 0.001) in NOV (13.6 kg) compared with MAR (11.9 kg) and JUL (11.4 kg) mating. Data suggest that dual flock, accelerated mating of landrace hair sheep ewes can produce lamb cohorts of similar size in 4 mo intervals under a low-input, forage-based production system.

scholarly journals 142 Evaluation of estrus detection patches as a tool to classify postpartum beef cows as estrous cycling or anestrous prior to the start of the breeding season

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 116-117
Author(s):  
Emily G Smith ◽  
Rachael C Bonacker ◽  
Carson M Andersen ◽  
Jordan M Thomas
Keyword(s):  
Pregnancy Rate ◽  
Breeding Season ◽  
Beef Cows ◽  
Estrus Synchronization ◽  
Serum Progesterone ◽  
Estrus Detection ◽  
Estrous Cyclicity ◽  
Type Ii Errors ◽  
Estrous Cycling

Abstract Estrus detection patches were evaluated as a tool to classify postpartum cows as estrous cycling or anestrous at the start of the breeding season. EstrotectTM Breeding Indicators were applied to 257 postpartum beef cows in three locations 25 days prior to the start of estrus synchronization. Coincident with the start of estrus synchronization, patches were scored using a 1 to 4 scale (1 = 0–25%; 2 = 25–50%; 3 = 50–75%; 4 = 75–100%) with scores of 3 or 4 considered activated. Blood samples were collected from each cow 10 days prior to, and at the start of the estrus synchronization. Serum progesterone concentrations were determined via radioimmunoassay; cows were considered estrous cycling if one or both samples exceeded a concentration of 0.5 ng/ml. Based on progesterone, 54.9% of cows were estrous cycling at the start of estrus synchronization. When missing patches were considered inconclusive results, use of patches to infer estrous cyclicity resulted in 85.0% sensitivity and 79.2% specificity with a positive predictive value of 87.2%. However, 75.1% of all cows presented with missing patches at the start of synchronization. If missing patches were considered activated, sensitivity was 95.7%, but specificity (16.4%) and PPV (58.2%) were poor, as 47.6% of cows presenting with missing patches were anestrous based on progesterone. Across all cows, pregnancy rate to AI was 58.0% (149/257). Cows with activated patches that were classified as false positives based on serum progesterone concentrations achieved a 71.4% (5/7) pregnancy rate to AI, raising questions as to whether sensitivity was underestimated due to inherent Type II errors in classification of cyclicity via progesterone. In summary, estrus detection aids are a sensitive tool to identify estrous cycling postpartum cows prior to the start of the breeding season; however, poor specificity and patch retention are limitations for this application.

REPRODUCTIVE POTENTIAL AND SEX RATIOS OF SNOWSHOE HARES IN NORTHERN ALBERTA

1956 ◽  
Vol 34 (4) ◽  
pp. 273-281 ◽  
Author(s):  
Wm. Rowan ◽  
L. B. Keith
Keyword(s):  
Litter Size ◽  
Sex Ratios ◽  
Reproductive Potential ◽  
Post Mortem ◽  
Comparable Data ◽  
Snowshoe Hares ◽  
Average Litter Size ◽  
Northern Regions ◽  
Two Factors ◽  
Northern Alberta

In conjunction with studies of the "10-year cycle" of snowshoe hares, almost 900 hares were collected in the Anzac district of Alberta during the period May, 1949, to April, 1956. Embryo numbers and sex ratios were among the data gathered from post-mortem examinations of these hares. It was found that the average litter size was 3.82; the modal litter size was four and the range was from one to seven. The average number of litters each season was calculated at 2.75. The annual reproductive potential is thus 10.51 (3.82 × 2.75) young per female hare. This is more than 50% greater than that indicated by comparable data from Minnesota. It is suggested that herein lies the cause of higher peak populations in northern regions. Sex ratios shifted from a marked excess of females in the year 1949–1950 to about even numbers of both sexes during the two subsequent years. Since the change in sex ratio occurred at the peak of the cycle, the two factors are believed to be in some manner correlated.

Efficiency of mating, artificial insemination or resynchronisation at different times after first timed artificial insemination in postpartum Nellore cows to produce crossbred calves

2019 ◽  
Vol 59 (2) ◽  
pp. 225 ◽  
Author(s):  
Walvonvitis Baes Rodrigues ◽  
Jean do Prado Jara ◽  
Juliana Correa Borges ◽  
Luiz Orcirio Fialho de Oliveira ◽  
Urbano Pinto Gomes de Abreu ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Breeding Season ◽  
Chorionic Gonadotropin ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Beef Cows ◽  
Device Removal ◽  
Oestradiol Benzoate ◽  
Timed Artificial Insemination ◽  
Equine Chorionic Gonadotropin

The objective of this trial was to evaluate different post-timed artificial insemination (TAI) reproductive managements in postpartum beef cows to produce crossbred calves from artificial insemination (AI). Nellore cows (n = 607), with 45 days postpartum, were inseminated at a fixed time, using a protocol that included an intravaginal progesterone-releasing device along with oestradiol benzoate, prostaglandin, equine chorionic gonadotropin, and oestradiol cypionate, followed TAI 48 h post-device removal. Four post-TAI treatments were evaluated: in CONTROL (T1, n = 161), cows were exposed to Nellore clean-up bulls until the end of the breeding season (75 days). In OBSERVATION (T2, n = 132), heat detection was performed for 15–25 days post-TAI, followed by AI. In RESYNC22 (T3, n = 157) and RESYNC30 (T4, n = 157), resynchronisation started after 22 or 30 days, following second TAI at Day 32 or 40 days after first TAI. In T2, T3 and T4, after the second AI, cows were exposed to Nellore clean-up bulls until the end of the breeding season (75 days). The pregnancy rate (PR) for the first TAI did not differ (54.6%, 53.0%, 59.2%, and 51.6% for CONTROL, OBSERVATION, RESYNC 22, and RESYNC 30, respectively; P = 0.66), and no difference was observed for the second TAI (RESYNC 22 = 45.31% and RESYNC30 = 46.05%; P = 0.137), in the PR at the end of the breeding season (86.33%, 86.36%, 78.98%, and 81.52%, P = 0.43), or embryonic losses (4.54%, 2.85%, 6.45% and 7.40%, respectively; P = 0.61), but the percentage of crossbred pregnancy was higher in groups with resynchronisation (RESYNC22 and RESYNC30) than CONTROL and OBSERVATION (98.38%, 90.62%, 63.30%, 78.95%, P &lt; 0.001). In conclusion, resynchronisation programs of 22 or 30 days are more efficient to produce AI products, and the final pregnancy rate is similar among the treatments, differing only in the amount of calves produced by AI.

The effect of melatonin treatment during the seasonal anoestrus on the superovulatory response and embryo production of high-prolificacy Rasa Aragonesa ewes before culling

2003 ◽  
Vol 2003 ◽  
pp. 82-82
Author(s):  
F. Forcada ◽  
J.A. Abecia ◽  
J.A. Valares
Keyword(s):  
Embryonic Development ◽  
Breeding Season ◽  
Litter Size ◽  
Direct Effect ◽  
Ovulation Rate ◽  
Corpora Lutea ◽  
Melatonin Treatment ◽  
Embryo Production ◽  
Spring Equinox

The efficacy of melatonin implants inserted around the spring equinox to improve fertility and ovulation rate or litter size in Mediterranean ewes has been previously reported (Chemineau et al., 1996; Forcada et al., 2002a.), indicating the ability of the hormone to regulate the hypothalamic activity (Viguié et al., 1995). Moreover, a direct effect of melatonin on corpora lutea and embryonic development has been also reported (Wallace et al., 1988; Abecia et al., 2002). The use of prolific Rasa Aragonesa (RA) ewes (a Mediterranean breed) before culling as embryo donors has been previously tested in the breeding season (Forcada et al., 2002b.). The aim of this experiment was to improve embryo production during the seasonal anoestrus period in selected superovulated RA ewes at the end of their reproductive lives through the use of melatonin.

scholarly journals Litter size components traits in two Algerian rabbit lines

2021 ◽  
Vol 29 (1) ◽  
pp. 51
Author(s):  
Rafik Belabbas ◽  
Maria de la Luz García ◽  
Hacina AinBaziz ◽  
Ali Berbar ◽  
Maria José Argente
Keyword(s):  
Body Weight ◽  
Litter Size ◽  
Principal Components ◽  
Local Population ◽  
The Body ◽  
Ovulation Rate ◽  
Phenotypic Correlation ◽  
Limiting Factor ◽  
Corpora Lutea ◽  
Synthetic Line

<p>The aim of this study was to estimate the limiting litter size components in rabbit females from a Synthetic line (n=32) and a Local population (n=34). Ovulation rate, number of implanted and live embryos were counted by laparoscopy at 12 d after mating. Prolificacy (total newborn, number born alive and mortality) and embryonic, foetal and prenatal survival at day of birth of the 3<sup>rd</sup> gestation were measured. The analysed traits were body weight of the female at mating, ovulation rate, implanted, live and resorbed embryos, embryonic, foetal and prenatal survival, as well as total newborn, number born alive and mortality at birth. Synthetic line females had a higher ovulation rate compared to the Local population (11.03±0.23 vs. 8.41±0.23 corpora lutea; <em>P</em>&lt;0.0001). Synthetic line displayed a higher number of implanted embryos (10.00±0.25 vs. 7.85±0.25 embryos; <em>P</em>&lt;0.0001). No difference was found between groups for number of resorbed embryos. Similar embryonic, foetal and prenatal survival rates were reported between the Synthetic line and the Local population. Additionally, total newborn was higher in the Synthetic line than in the Local population (+1.46 kits; <em>P</em>&lt;0.05). A principal components analysis was performed. The first four principal components (PC) explained more than 90% of the total variation in both lines. Total newborn, number born alive and live embryos were the main variables defining the 1<sup>st</sup> PC. Resorbed embryos and foetal survival were located in the 2<sup>nd</sup> PC. Ovulation rate and embryonic survival were the predominant variables defining the 3<sup>rd</sup> PC. The body weight of females was located in the 4<sup>th</sup> PC. The phenotypic correlation between total newborn and its components were high and positive in both lines, except for ovulation rate and total newborn, where it was moderate in Synthetic line. In conclusion, the females from Synthetic line have a higher total newborn than those from Local population, as a consequence of a higher number of released oocytes and embryos that successfully reach implantation. However, a higher uterine crowding in Synthetic line seems to limit survival of foetuses that reach term of gestation, while ovulation rate is the principal limiting factor of total newborn in Local population.</p>

scholarly journals AVALIAÇÃO DO DESEMPENHO REPRODUTIVO DE VACAS NA REGIÃO DO PANTANAL SUL-MATO-GROSSENSE SUBMETIDAS A IATF Com Aplicação De GnRH

Nativa ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 281-285
Author(s):  
Gabriel Rodrigo Hass Perucchi ◽  
Gabriela de Souza Sartori ◽  
Richarlla Aparecida Buscariol Silva ◽  
Murilo da Silva Garcia ◽  
Rodrigo José Delgado Jardim ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Pregnancy Rate ◽  
Reproductive Performance ◽  
Artificial Insemination ◽  
Body Condition Score ◽  
The Body ◽  
Mato Grosso ◽  
Condition Score ◽  
Timed Artificial Insemination ◽  
Mato Grosso Do Sul

A Inseminação artificial em tempo fixo (IATF) está se difundindo no Brasil, pois contribui para o aumento da produtividade. O objetivo neste trabalho foi avaliar o uso do GnRH em protocolos de IATF de vacas criadas no pantanal Sul-mato-grossense. Participaram da pesquisa 531 vacas paridas da raça Nelore, que foram avaliadas de acordo com o escore de condição corporal (ECC), submetidas a três tipos de protocolos de IATF (lote 1, 2 e 3). Após 40 dias da inseminação artificial foi realizado diagnóstico de gestação. As matrizes que não receberam GnRH no lote 1 (estro aparente), lote 2 (estro parcial) e lote 3 (sem apresentação de estro) apresentaram, respectivamente 55,4%, 19,2% e 25,9% de prenhez, enquanto as que receberam o fármaco apresentaram 48,6%, 37,2% e 38,8%. Relacionado ao ECC, pode-se observar que a maior taxa de prenhez ocorreu em animais com ECC 3. Primíparas apresentaram melhor taxa de prenhez quando receberam GnRH independente do ECC. Concluiu-se que o uso de GnRH mostrou-se eficiente para melhoria da taxa de prenhez principalmente em primíparas, assim como nos animais que não apresentaram estro ou apresentaram estro parcial, e que matrizes com ECC 3 apresentaram melhores taxas de prenhez que vacas com escore inferior. Palavras-chave: bovino de corte; inseminação artificial em tempo fixo; produtividade; GnRH; Nelore.   Evaluation of cow reproductive performance in the region of Mato Grosso do Sul swamp submitted to TAI with GnRH application   ABSTRACT: The technique of timed artificial insemination (TAI) is spreading in Brazil, as it contributes to the increase of productivity. The objective of this work was to evaluate the use of GnRH in TAI protocols of cows raised in the swamp of Mato Grosso do Sul. 531 Nelore breed calved cows participate in the survey, which were evaluated according to the body condition score (BCS), and then performed three types of TAI protocols (batch 1, 2 and 3). After 40 days of the insemination, a pregnancy diagnosis was made. The matrices that did not receive GnRH in batch 1 (apparent oestrus), batch 2 (partial oestrus) and batch 3 (no oestrus presentation) presented respectively 55.4%, 19.2% and 25.9% of pregnancy, while those receiving the drug showed 48.6%, 37.2% and 38.8%. Related to BCS, it can be observed that the highest pregnancy rate occurred in animals with BCS 3. Primiparous had a better pregnancy rate when receiving GnRH regardless of BCS. It was concluded that the use of GnRH was efficient to improve the pregnancy rate mainly in primiparous as well as animals that showed no oestrus or partial oestrus, and matrices with BCS 3 had better pregnancy rates than cows with lower scores. Keywords: beef cattle; timed artificial insemination; productivity; GnRH; Nelore.

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