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The aim of this study was to evaluate the impact of increased shadow supply in integrated crop-livestock-forest systems on in vitro embryonic development and physiological parameters related to stress response in Nellore heifers (Bos indicus). For the study, animals (n = 16) were randomly divided into two groups and kept in areas with different afforestation systems, the integrated crop-livestock-forest (ICLF) and the integrated crop-livestock (ICL) system. The microclimate of the ICLF system provided better comfort conditions than ICL. No differences of respiratory rate, rectal temperature, cortisol, T3, T4, oocyte quality, and cleavage rate between the systems were verified. A higher blastocyst rate was observed in the ICLF (p < 0.05). The results demonstrate that Nellore heifers managed in ICLF during summer in Midwest of Brazil showed higher production of in vitro embryos, without typical changes in its physiological parameters. The results observed in the present study indicate that zebu females are able to respond satisfactorily to the intense heat conditions; however, we believe that the long period to which these animals are exposed to these conditions interferes in the oocyte competence and embryo development.

Antral follicular population (AFP) and antiMüllerian hormone (AMH) concentration are strongly associated. Thus, analyzing AMH concentration is a reliable method to predict animals with high AFP, an important feature to select donor cows for embryos and oocytes. However, not much is known about this parameter in heifers, particularly in crossbred animals. The aim of this study was to assess AFP in heifers and cows and its relation to serum AMH levels. Bos taurus indicus cows (36-60-months-old; n = 30) and heifers (12-14-months-old; n = 17) of the same breed were evaluated. A single procedure of follicular counting was performed by ultrasound for each animal. Random sampling was performed to analyze serum AMH concentration. Cows showed higher AFP than heifers; nonetheless, plasma AMH concentration did not differ between the categories. A high correlation of AFP with plasma AMH concentration was observed in Girolando heifers. Thus, it is suggested that AMH concentration could be a reliable and less invasive method for selecting heifers with high AFP.

RESUMO Nos trópicos, o uso de raças adaptadas tem sido uma estratégia para minimizar o efeito do estresse térmico calórico (ETC). No entanto, faltam informações que quantifiquem o estresse e o seu efeito sobre a reprodução dessas raças. O objetivo deste estudo foi avaliar a qualidade do oócito recuperado e alguns parâmetros fisiológicos indicadores de ETC em bovinos de raças adaptadas. Animais Bos taurus x Bos indicus (n=6) e Bos taurus (raça Pantaneira; n=12), localizados na região de transição entre o Cerrado e o Pantanal brasileiro, foram submetidos à aspiração folicular guiada por ultrassonografia (OPU) em diferentes condições climáticas. Foram realizadas oito sessões de OPU, com intervalo mínimo de sete dias e máximo de 54 dias entre as coletas. Para caracterização climática, foi realizado o cálculo do índice de temperatura e umidade (ITU). Foram quantificados os ITUs do dia da OPU, sete dias antes e 60 dias antes de cada sessão. Os parâmetros fisiológicos e a viabilidade oocitária de fêmeas das raças Girolando e Pantaneira não foram afetados negativamente por ITUs entre 72 e 78. O ETC crônico (60 dias) parece afetar a viabilidade oocitária de doadoras na raça Pantaneira quando ITU é superior a 75.

The objective of this study was to investigate the influence of long-term temperature stress during the in vitro maturation (IVM) of oocytes on the in vitro embryo production (IVP) and the abundance of HSP70 and HSP90 in zebu cattle. Viable cumulus-oocyte complexes (COCs) were incubated for 24 h at 37 °C, 38.5 °C, or 40 °C for the low-, physiological, and high-temperature stress treatments, respectively. Thereafter, they were subjected to in vitro fertilization and culture. Temperature did not affect the polar body extrusion. However, IVP was adversely affected when IVM took place at 37 °C and 40 °C. The highest abundance of HSP70 was observed in cumulus cells after maturation of COCs at 40 °C. In contrast, HSP70 was more abundant in oocytes at both 37 °C and 40 °C; however, at 40 °C, the difference to the control group (38.5 °C) was not significant. In contrast, the highest abundance of HSP90 was observed in oocytes and cumulus cells at 37 °C. It appears that HSP70 and HSP90 respond to cold and heat stress in different ways. In conclusion, moderately high (40 °C) and low (37 °C) thermal stress for 24 h during IVM is detrimental to the developmental competence of oocyte and is accompanied by changes in the abundances of HSP70 and HSP90, especially in cumulus cells.

The aim of this study was to evaluate ovarian antral follicle populations (OAFP) of Nelore and Girolando breed heifers (12-18 months old) and cows (24-60 months old). Animals were assigned to four groups: (1) Nelore cows (n = 18), (2) Girolando cows (n = 20), (3) Nelore heifers (n = 7), and (4) Girolando heifers (n = 7). Cows were treated to synchronize follicular wave emergence by implantation of an intravaginal device containing 1.9 g of progesterone, as well as intramuscular administration of 2 mg of estradiol benzoate and 25 mg of dinoprost. This synchronization treatment was administered at a random day of the estrous cycle of each cow, designated D0. Intravaginal devices were removed on D7, and on D11, OAFP counts were performed by transvaginal ovarian ultrasound. For each cow, all follicles ≥3 mm in diameter were counted in both ovaries and counts were performed three times at 35-day intervals. Counts were also obtained from heifers, but these animals were not treated for synchronization of follicular wave emergence. Analysis of variance (ANOVA) with Tukey's test and Pearson's correlation test were used to compare mean OAFPs between counts as well as mean OAFPs between breed and age groups. No differences were observed in mean OAFPs between Nelore and Girolando cows (30.9 vs. 26.7, respectively; P > 0.05) or heifers (16.2 vs. 18.1, respectively; P > 0.05). However, within each breed, there were differences in mean OAFPs between heifers and cows (for Nelore cattle: 16.2 and 30.9, respectively; for Girolando cattle: 18.1 and 26.7, respectively; both P < 0.05). In conclusion, OAFPs were similar between Nelore and Girolando breeds and were influenced by age. Furthermore, we observed a high correlation for individual animals between the mean numbers of follicles counted in both ovaries and total number of follicles counted in either the right or left ovary, indicating that the evaluation of a single ovary is sufficient to estimate the OAFP of an individual. ResumoEste estudo objetivou avaliar a população folicular antral ovariana (PFAO) de novilhas (12 a 18 meses) e vacas (24 a 60 meses) das raças Nelore e Girolando. Os animais foram divididos em quatro grupos: 1) vacas Nelore (n = 18); 2) vacas Girolando (n=20); 3) Novilhas Nelore (n=7) e; 4) Novilhas Girolando (n=7). Nos grupos das vacas, os animais receberam um dispositivo intravaginal com 1.9 g de progesterona, 2 mg de benzoato de estradiol IM e 25 mg de dinoprost IM, em um dia aleatório do ciclo estral (D0). No D7 o dispositivo de progesterona foi retirado. Os animais foram submetidos à ultrassonografia ovariana via transvaginal para contagem da PFAO no D11. Foram contados todos os folículos ≥ 3 mm de diâmetro em ambos os ovários. O procedimento de contagem da PFAO foi repetido três vezes, com intervalos de 35 dias entre as repetições. Para os grupos de novilhas foram adotados os mesmos procedimentos descritos acima, porém estes animais não receberam o tratamento de sincronização da emergência da onda folicular. Para avaliação da PFAO entre as co...

Summary The aim of this study was to evaluate the production of bovine embryos in vitro when supplemented with l-carnitine for 24 h beginning on day 5 (d 5) under two different oxygen tensions (20% or 5%) and the relationship of nitric oxide (NO) in in vitro culture (IVC) medium to embryo development. Cumulus–oocyte complexes (COC; n = 837) were matured in vitro for 24 h and fertilization was performed for 18 h. Zygotes were cultured in vitro for 9 days after in vitro fertilization in synthetic oviductal fluid (SOF) medium with 5% fetal calf serum. At d 5 the plates were assigned to one of four treatment groups: high (20%) or low (5%) O2 tension either with or without the addition of 3.03 mM l-carnitine (High-Cont, High-Lcar, Low-Cont, Low-Lcar). The concentration of NO in the culture medium was evaluated on d 5, d 6 and d 9. On d 7, parts of the embryos were submitted for evaluation of intracellular lipid droplets. The cleavage rate was similar (P > 0.05) between high and low O2 tension and the blastocyst rate was similar in all conditions evaluated. The hatching rate was higher (P < 0.05) for Low-Cont. The NO concentration was higher at d 9 under low O2 tension (P < 0.1). The addition of 3.03 mM l-carnitine between d 5 and d 6 of IVC was not efficient in reducing cytoplasmic lipid content of bovine embryos. Additionally, IVC at a low oxygen tension without l-carnitine promoted better conditions for embryo development. A higher concentration of NO in medium was observed under low O2 tension.

This study aimed to evaluate the relationship between the antral follicle count (AFC) and the ovarian morphology of Bos indicus in different age groups: 12-23 months (G1), 24-35 months (G2), 36-47 months (G3), 48-59 months (G4), and >60 months (G5). Ovaries were collected individually and sent to the laboratory, where we measured AFC, the diameter and weight of the ovaries, dominant follicle (DF, ≥8mm), corpus luteum (CL), and small follicles (SF, <8mm). AFC were classified as high, intermediate-high, intermediate-low, and low. A group of ovaries was subjected to follicular aspiration to evaluate the morphological quality of the recovered cumulus oocyte complexes (COCs). Mean AFC did not vary between ages. The morphological characteristic that was most closely correlated with AFC was the weight of the small follicles. There was no relationship between AFC and the weight and diameter of the DF and CL. Quality of the COCs was superior in ovaries in which the CL was present, but it did not vary between the AFC classes. We conclude that AFC can be performed on a single ovary, regardless of the presence, diameter, and weight of the CL and DF in zebu between 12 and 60 months old.