Ultrasonic Imaging of Reproductive Events in Muskoxen

To our knowledge, this is the first detailed report of ovarian follicular dynamics in a wild species. It seems that the pattern in muskoxen, with major and minor waves and a short first cycle, is similar to that in goats. Insight of this kind is important in the design of appropriate artificial breeding systems and in this respect, the muskox may provide a useful model for the endangered takin {Budorcas taxicolor). A detailed knowledge of ovarian events may also be critical to the interpretation of the response of wild populations to environmental stress

Diferenças sazonais no padrão endócrino e ovariano do ciclo estral de novilhas Bos taurus indicus (Nelore)

Estrous cycle of eight Nelore heifers were evaluated during different seasons of the year (autumn n=11; winter n=8; spring n=9 and summer n=9) with daily count and measurement of follicles ≥3mm, blood was collected every 12h for LH and progesterone (P4), and after estrous every 3h for LH peak. Five ovariectomized heifers were injected with 17β-estradiol (2μg/kg) every season and blood samples collected every 3h (for 30h) thereafter for LH quantification. The monthly percent body weight difference (Δ%) did not vary among seasons. P4 concentration was higher (p<0.01) and follicle number lower during autumn and summer compared to winter and spring. During winter there were more estrous cycles with three and during summer only cycles with two follicular waves (p<0.01). As LH secretion did not vary despite P4 concentration and as there was negative correlation between higher P4 values and daily percentile variation of photoperiod (Δ%, p<0.01; r= -0.45) it is possible to suppose that there is seasonal variation on luteal cell sensitivity to LH. In the ovariectomized Nelore heifers, the LH basal concentration (without estradiol stimulus, p=0.02) and the LH response to estradiol (p<0.01) were lower during summer, leading to the hypothesis that there is seasonal variation of hypothalamic sensitivity to estradiol. According to the present experiment there are suggestions of seasonal reproduction in Nelore heifers.Ciclos estrais em oito novilhas Nelore foram acompanhados durante diferentes estações (outono n=11; inverno n=8; primavera n=9; verão n=9) com contagem e diâmetro de folículos ≥ 3 mm diariamente, com colheitas de sangue a cada 12 h para LH e P4, e a cada 3 h para o pico de LH. Cinco novilhas ovariectomizadas receberam 17β estradiol (2μg/kg) em cada estação, com colheitas de sangue a cada 3 h para quantificar LH. A diferença percentual (Δ%) do peso entre os meses não variou entre as estações. Durante o ciclo estral, a concentração de P4 (média e máxima) foi maior (p<0,01), e o número de folículos menor (p<0,01), no outono e verão, se comparados ao inverno e primavera. No inverno houve mais ciclos com três ondas e no verão somente ciclos com duas ondas foliculares (p<0,01). Como as características da secreção de LH não foram diferentes apesar da variação na concentração de P4, e como houve correlação negativa entre os valores máximos de P4 e a variação percentual (Δ%) diária no fotoperíodo (p<0,01; r= -0,45), supõe-se que haja variação sazonal na sensibilidade das células luteínicas ao LH. Nas novilhas ovariectomizadas, a concentração basal (sem estradiol) circanual de LH foi menor no verão (p=0,02), assim como a sua secreção em resposta ao estradiol (p<0,01), o que permite supor que também haja uma variação sazonal na sensibilidade hipotalâmica ao estradiol. De acordo com o presente experimento, há indícios de sazonalidade reprodutiva em novilhas Nelore

THE EFFECT OF NUTRITIONAL LEVEL ON ADVANCING AGE AT PUBERTY IN NELORE HEIFERS

The objective of this study was to verify the effect of nutritional level on advancing age at Renata puberty in Nelore heifers. Thirty-one animals at 6 months of agewere randomly assigned in two groups: GI, or control, with 15 heifers that received a basal diet, and GII, or supplemented, with 16 heifers that received a diet with higher energy and crude protein levels. The development of the animals was accompanied by weighing them at 21-day intervals to verify the daily weight gain from 6 months to puberty. The diets were readapted when necessary. The reproductive status was monitored by ultrasound every two days; and by progesterone concentrations from blood samples drawn twice a week. The ovulation was determined when progesterone concentrations were higher than 1 ng/mL in three consecutive samples, and by ultrasound images of corpus luteum; and oestrous behavior in some animals. The GII group manifested puberty at 16.33 ±0.89 months of age and GI at 20.58 ±1.83 months of age (p<0.05). The mean weight at puberty was 302.33 ±21.31Kg for GI and 326.19 ±27.78Kg for GII. The daily weight gain was 0.647 ±0.08Kg for GII and 0.447 ±0.03Kg for GI (p<0.05). Progesterone levels at puberty were 2.7801 ±0.27 ng/mL for GI and 2.5747 ±0.26 ng/mL to GII. Only 13% of all heifers manifested oestrous behavior. The nutritional supplementation decreased the age of puberty onset in GII and both groups manifested puberty earlier than heifers feeding only on pasture in Subtropical conditions. It is possible to have an earlier puberty onset in Nelore heifers through nutritional supplementation, without negative effects on their reproductive physiology.RESUMO O objetivo deste trabalho foi verificar o efeito do nível nutricional na antecipação da idade à puberdade em novilhas nelore. Trinta e um animais de seis meses de idade foram aleatoriamente divididos em dois grupos: GI, ou testemunha, com 15 novilhas que receberam uma dieta basal, e GII ou suplementado, com 16 novilhas que receberam uma dieta com altos níveis de energia e proteína bruta. O desenvolvimento dos animais foi acompanhado por pesagens a cada 21 dias para verificar o ganho de peso diário. As dietas foram re-adaptadas quando necessárias. O estado reprodutivo foi monitorado por ultra-sonografia a cada dois dias, e por concentração de progesterona de amostras de sangue colhidas duas vezes por semana. A ovulação foi determinada quando as concentrações de progesterona forma maior que 1ng/mL em três amostras consecutivas, e por imagem ultra-sonográfica de corpo lúteo; e comportamento de estro em alguns animais. O grupo GII manifestou puberdade aos 16,33 ± 0,89 meses de idade e o GI 20,58 ± 1,83 meses de idade (p £ 0,05). A média do peso à puberdade foi 302,33 ± 21,31 Kg para o GI e 326,19 ± 27,78 Kg para o GII. O ganho médio diário foi de 0,647 ± 0,08 Kg para o GII e 0,447 ± 0,03 Kg para o GI (p £ 0,05). Os níveis de progesterona à puberdade foram 2,7801 ± 0,27 ng/mL para o G I e 2,5747 ± 0,26 ng/mL para o GII. Somente 13% das novilhas apresentaram manifestação de estro. A suplementação Nutricional retrocedeu a idade à puberdade no grupo GII e ambos os grupos manifestaram puberdade mais cedo que novilhas se alimentando somente em condições subtropicais de pastoreio. É possível antecipar o início da puberdade através da suplementação nutricional sem efeitos negativos na fisiologia reprodutiva de novilhas Nelore

Efeito dos períodos seco e chuvoso sobre a maturação nuclear e incidência de apoptose em oócitos ovinos

Objetivou-se determinar o efeito dos períodos seco e chuvoso na maturação nuclear e incidência de apoptose em oócitos ovinos maturados in vitro. Os ovários foram colhidos em abatedouro e transportados para o laboratório durante os períodos seco (Outubro a Março) e chuvoso (Abril a Setembro). Os oócitos foram recuperados de folículos de 2 a 6 mm, selecionados e maturados in vitro em 12 réplicas. Após a maturação, o estádio da meiose foi determinado pela coloração DAPI e a apoptose foi avaliada pela atividade das Caspases e pela fragmentação de DNA. As taxas de oócitos nos estádios de vesícula germinativa, metáfase I, telófase I e metáfase II foram semelhantes (P &gt; 0,05). A atividade das enzimas Caspases foi mais frequente nos oócitos maturados in vitro durante o período seco, embora a incidência de fragmentação do DNA tenha sido semelhante entre os grupos (P &gt; 0,05). Em conclusão, os períodos do ano exercem influência na viabilidade dos oócitos ovinos maturados in vitro aferida pela incidência da atividade das Caspases

Altering the timing of fixed-time artificial insemination and the interval from progestin withdrawal to prostaglandin F2a administration in estrus synchronization protocols for beef heifers

An experiment (Chapter 2) was designed to evaluate later timepoints for fixedtime artificial insemination (FTAI) of beef heifers, with the hypothesis that use of a later timepoint would allow a greater proportion of heifers to express estrus prior to FTAI and result in greater conception rates among estrous heifers inseminated with sex-sorted semen. Estrus was synchronized for 1640 heifers in 7 locations using the 14-d CIDR-PG protocol: insertion of an intravaginal progesterone-releasing insert (CIDR; 1.38 g progesterone) on Day -33 and removal on Day -19, and administration of prostaglandin F2a (PG; 500 [mu]g cloprostenol sodium) on Day -3. Within location, heifers were blocked based on reproductive tract score and body weight and were randomly assigned to one of three FTAI timepoints: 66 h, 70 h, or 74 h after PG administration. Estrus detection aids (Estrotect) were applied at PG administration, with activation recorded at FTAI. Heifers that expressed estrus prior to FTAI were inseminated with sex-sorted semen (SexedULTRA 4M[trademark]). Heifers that failed to express estrus were inseminated with conventional semen. Gonadotropin-releasing hormone (GnRH; 100 [mu]g gonadorelin) was administered coincident with FTAI for heifers that failed to express estrus. The proportion of heifers that expressed estrus prior to FTAI (66 h: 62%; 70 h: 67%; 74 h: 71%) was greater when FTAI was performed at 74 h versus 66 h (P 0.10) with respect to the conception rates of heifers that expressed estrus and were serviced with sex-sorted semen (66 h: 56%; 70 h: 53%; 74 h: 53%). Among heifers that failed to express estrus and were serviced with conventional semen, conception rates were greater (P = 0.02) when FTAI was performed at 66 h versus 70 h (66 h: 37%; 70 h: 25%; 74 h: 31%). Results indicate that performing FTAI later following the 14-d CIDR-PG protocol increases the proportion of heifers that express estrus and are serviced with sex-sorted semen, but later timing of FTAI does not improve conception rates. A series of experiments (Chapter 3) was designed to evaluate treatment schedules for control of the estrous cycle in which luteolysis is induced prior to atresia of the first follicular wave following a long-term progestin presynchronization treatment in beef heifers. The overarching hypothesis was that the proportion of heifers undergoing luteolysis and expressing estrus would be affected by the duration of treatment with an intravaginal progesterone-releasing insert (CIDR[registered trademark ownership]; 1.38 g progesterone) and/or by the interval from CIDR removal to prostaglandin F2[alpha] (PG; 500 [mu]g cloprostenol) administration. In Experiment 1, heifers (n = 91) were blocked by reproductive tract score (RTS) and body weight (BW) and were assigned randomly within block to one of four treatments in a 2 x 2 factorial design: presynchronization via CIDR treatment for either 14 d (Treatments 14-8 and 14-9) or 18 d (Treatments 18-8 and 18-9) with administration of PG either 8 d (Treatment 14-8 and 18-8) or 9 d (Treatment 14-9 and 189) following CIDR removal. In Experiment 2, heifers (n = 63) were blocked by RTS and BW and randomly assigned to receive administration of PG either 9 d or 10 d following a 14 d CIDR presynchronization. In Experiment 3, heifers (n = 83) were blocked by RTS and BW and randomly assigned to receive administration of PG either 9 d or 16 d following a 14 d CIDR presynchronization. In all three experiments, estrus detection aids (Estrotect) were applied at the time of PG administration. In Experiments 1 and 2, heifers were observed for expression of estrus three times daily for 4 d following PG administration and received artificial insemination (AI) based on estrous response. For heifers that failed to express estrus by 96 h after PG administration, timed AI was performed and gonadotropin-releasing hormone (GnRH; 100 [mu]g gonadorelin) was administered. In Experiment 3, Estrotect patch activation was recorded at 66 h, and heifers that expressed estrus by 66 h were inseminated at that timepoint. Heifers that failed to express estrus by 66 h were inseminated at 90 h. For heifers that failed to express estrus by 90 h, GnRH was administered at timed AI. In all three experiments, blood samples were collected at the time of PG administration and, for heifers that failed to express estrus, at timed AI to determine serum progesterone concentrations via radioimmunoassay. In Experiment 1, serum estradiol concentrations were also determined via radioimmunoassay. Transrectal ovarian ultrasonography was performed to determine CL status and to measure largest follicle diameter (LFD) at PG administration and, for heifers that failed to express estrus, at timed AI. Transrectal ultrasonography was performed 60-80 d after AI to determine pregnancy status. In Experiment 1, there was a tendency for a greater proportion of heifers to express estrus by 96 h after PG administration when PG administration occurred 9 d after CIDR removal versus 8 d after CIDR removal (P < 0.07; 8 d: 57% [26/46]; 9 d: 76% [34/45]). Additionally, serum E2 levels were greater at the time of PG administration when PG was administered 9 d after CIDR removal versus 8 d after CIDR removal following an 18-d CIDR treatment (P < 0.006; 18-8: 5.7 [plus-minus sign] 1.0 pg/mL; 18-9: 9.6 [plus-minus sign] 0.9 pg/mL). In Experiment 2, pregnancy rate to AI (P/AI) was greater among heifers receiving PG administration 9 d after CIDR removal versus 10 d after CIDR removal (P < 0.03; 14-9: 58% [18/31]; 14-10: 28% [9/32]). There was a tendency for LFD to be greater among non-estrous heifers in treatment 14-10 versus non-estrous heifers in treatment 14-9 when measured at timed AI (P < 0.08; 14-9: 11.9 [plus-minus sign] 1.6; 14-10: 13.6 [plus-minus sign] 1.3). In Experiment 3, there was a tendency for serum progesterone concentrations at the time of PG administration to be greater among heifers in treatment 14-16 versus heifers in treatment 14-9 (P = 0.07; 14-9: 1.2 [plus-minus sign] 0.2 pg/mL; 14-16: 1.8 [plus-minus sign] 0.2 pg/mL). These results provide a preliminary evaluation of the feasibility of inducing luteolysis prior to atresia of the first follicular wave following long-term progestin presynchronization.Includes bibliographical references

Characteristics of subordinate follicles following removal of the dominant follicle: Induction of selection

In mammals, ovarian follicles begin as primordial follicles. Over time these follicles are gradually activated and begin growth. As they proceed, granulosal and thecal cells are acquired. Eventually, the follicles become dependent on FSH for survival. Two or three times each cycle, a transient increase in FSH allows a cohort of follicles, including the follicle that will ovulate, to continue growing. However, these follicles secrete inhibin and estradiol, which suppress FSH secretion. Eventually, all the follicles of the cohort undergo atresia due to the declining concentrations of FSH, except for the follicle which has the potential to ovulate. This follicle survives the decline in FSH because the granulosal cells of that follicle develop LH receptors that allow stimulation to keep the follicle healthy. The concentrations of estrogen and free insulin-like growth factor I are different in the selected follicles compared to the follicles that underwent atresia in the cohort of follicles. However, because the ovulatory follicle cannot be identified until after it is selected, it is difficult to study the initial changes causing selection. One phenomenon from which insights to selection can be gained is compensatory hypertrophy, which is the ability of an animal to maintain the same ovulation rate after removal of one ovary. This compensation occurs at the next estrus, unless the unilateral-ovariectomy is carried out at the end of the cycle. Therefore, the present study determined the fate of the subordinate follicles following removal of the selected follicle at different stages of the estrous cycle of the cow. Results indicated that if the dominant follicle of a second wave and the CL were removed at day 13 post estrus, the largest subordinate follicle remaining became dominant. However, all treatments later in the cycle resulted in regression of the remaining follicles and emergence of a new wave of follicles before ovulation

組換え体ヒツジインヒビンαサブユニットの免疫が黒毛和種における一次主席卵胞の消長に及ぼす影響

Inhibin immunization increases the ovulation rate in cows, though its precise effect on the ovarian response during the luteal phase has not yet been investigated. The aim of this study was to examine the effect of inhibin immunization on the fate of the first dominant follicle (1st. D. F. )in Japanese Black cows. Eighty-nine estrous cycles were divided into four groups, as follows ： ablation groups (10 in the non-immunized group, 8 in the immunized group), made up of cows receiving follicle ablation at estrus, and non-ablation groups (24 in the non-immunized group, 47 in the immunized group), comprising the control animals. Concentrations of blood plasma estradiol-17β (E2β)were measured. The transient E2β peak corresponding to the 1st. DF. development was observed earlier in the immunized ・non-ablation group than in the non-immunized ・non-ablation group. In the immunized ・non-ablation group, the emergence and development of the follicles occurred continuously throughout the pre- and post-estrus phase. On the other hand, the transient E2β peak in the immunized ・ablation group had not appeared by the day on which the peak was found in the non-immunized ・non-ablation group, because the 1st. D. F. development, similar to that in the non-immunized ・non-ablation group, was induced after the ablation. This study demonstrates that multiple "1st. D. F." begins to develop as early as the preceding estrous phase in inhibin-immunized Japanese Black cows.本研究では, ウシのインヒビン免疫で誘起される卵巣反応のうち, 一次主席卵胞 (first dominantfollicle ； 1st. D. F. )の消長について調べた。免疫は28 日間隔でインヒビンワクチン2 ml (組換え体ヒツジインヒビンαサブユニットとして0.5 ㎎)を皮下に投与することで行った。黒毛和種について観察した延べ89 発情周期について, 発情日に卵胞を除去した卵胞除去区 (非免疫区 ： ｎ =10, 免疫区 ： ｎ =8)と非除去区 (非免疫区 ： ｎ =24, 免疫区 ： ｎ =47)に分け, 血中estradiol-17β (E2β)の推移を比較検討した。免疫・非除去区では, 発情前後に持続的な複数の卵胞発育が観察され, 1st.D.F.の発育時期と一致すると考えられる一過性のE2βピークは, 発情後3.0 ± 0.2 日目と, 非免疫・非除去区 (4.9 ± 0.3 日目)より有意 (P<0.01)に早く形成された。しかし, 免疫・除去区では, 非免疫・非除去区の排卵後と同様の1st.D. F. の発育が観察され, E2βピークの時期も非免疫・非除去区と同じになった。以上のことから, インヒビン免疫を行った黒毛和種では, 主席化する複数の卵胞の一部は発情時にすでに発育を開始していると考えられた

Estratégias anti-luteínicas sobre a fertilidade de novilhas de Corte

This study was carried out to evaluate the effects of progesterone (P4) supplementation after fixed-time artificial insemination (AI) through two different routes of administration (oral and intramuscular) on pregnancy rate of Nellore heifers. Fortyfive Nellore heifers were used averaging months (30 ± 2.08) of age, (330 ± 0.707) kg BW and 2.5 BCS (five-point scale) at the beginning of the experiment. Heifers were randomly assigned to three experimental groups of fifteen animals each and maintained on an extensive grazing system (Andropogon pasture) with mineral supplementation and water ad libitum. Experimental groups (treatments) included: group 1 (control group) (no exogenous P4 administration (G1)); group 2: intramuscular (IM) administrationof 1.0 mL P4 (Sincrogest injectable; OuroFino) on day 4 afterAI (G2); and group 3: supplementation of 2.28 mg/animal/day P4 (melengestrol acetate MGA; Zoetis), starting 4 days afterAI and remaining until day9 (d 4 – d 9). Progesterone (MGA) was incorporated to the mineral-protein energy supplement (Phósverão–Acabamento–Matsuda) and offered to the animals (G3), daily in the morning. All animals were submitted to the following fixed-time AI protocol: On d zero, an ear implant of P4 was placed (Crestar, MSD) and 2 mg estradiol benzoate (EB, Fertilcare Sincronização, MSD) was administered IM. Eight days later (d 8), the ear implant was removed and 2 ml of synthetic prostaglandin (Ciosin, MSD), 1.5 ml ecG (Folligon 5000 UI, MSD) and 1 ml estradiol cypionate (Fertilcare Ovulação, MSD) were administrated IM. On d 10 of the protocol, AI was performed and the diameter of preovulatory follicles were measured by transrectal ultrasonography. Pregnancy diagnosis was performed thirty-five days after-AI. Estrus expression was evaluated by tail-painting of each cow on d 8 of the protocol, and evaluating the presence of paint at AI. Statistical analyses were performed using the ONE PARWAY procedure of SAS. The Kruskal-Wallis test was used to check for significant differences among treatments. There was no significative difference on pregnancy rate among experimental groups. Supplementation of P4 from d 4 to d 9 after AI, through oral administration, resulted in numerically higher percentage of pregnantanimals (G3) compared to IMP4 administration (G2) and no P4 administration (G3). Both diameter of dominant follicle and the estrus expression showed no positive effect on conception rate in Nellore heifers during the dry season.O presente trabalho tem como objetivo avaliar a eficiência do uso de progesterona exógena, sob duas vias de administração, intramuscular e oral, sobre a taxa de prenhez de novilhas bovinas após protocolo de IATF. Utilizou-se quarenta e cinco novilhas Nelores, com idade média de trinta meses e peso médio de onze arrobas. Os animais foram distribuídos aleatoriamente em três grupos e colocados em sistema de pastejo extensivo com suplementação de sal mineral, sendo cada grupo constituído de 15 animais. Sendo G1: grupo controle, sem administração de progesterona exógena; G2: recebendo no 4º dia pós-inseminação, por via intramuscular 1,0 mL de progesterona injetável (Sincrogest® Injetável, Ourofino); e G3: a partir do 4º dia pós-protocolo de IA receberam progesterona (MGA®, Zoetis) na dosagem de 2,28 mg/animal/dia, durante seis dias consecutivos adicionada a suplementação mineral protéica com fontes energéticas (Phós verão –Acabamento – Matsuda). Todos os grupos receberam implantes auriculares (Crestar®; MSD) juntamente com 2,0 ml (2,0mg) de Fertilcare Sincronização (Benzoato de estradiol; MSD) intramuscular no dia zero (D0). No dia oito (D8) foi efetuada a retirada dos implantes auriculares e realizada a administração de 2,0 ml de Ciosin® (Prostaglandina sintética; MSD), 1,5ml de Folligon® 5000 UI (ecG; MSD) e 1,0 ml de Fertilcare Ovulação (Cipionato de estradiol; MSD) todos por via intramuscular. No Dia dez (D10) as vacas foram inseminadas em tempo fixo (IATF) e o diâmetro do folículo pré-ovulatório foi mensurado por ultrassonografia transretal (Modelo MINDRY DP-2200 VET, com transdutor linear de 10 Mhz). O diagnóstico gestacional foi realizado aos 35 pós-IATF através de ultrassonografia transretal. Os dados foram analisados através do procedimento ONE PARWAY do software SAS, e as médias comparadas através do teste de Kruskal-Wallis. Não foram observadas diferenças significativas entre os grupos experimentais, tendo o G3 maior taxa de prenhez. O diâmetro folicular, a presença de cio, e adição de progesterona exógena não exerceram influencia positiva sobre a taxa de concepção de novilhas Nelore durante o período seco