Rodrigo Arruda de Oliveira

USE OF DIFFERENT EXTENDERS TO CRYOPRESERVATION OF MANGALARGA MARCHADOR SPERM

The techniques applied to animal reproduction such as artificial insemination, transfer and in vitro production of embryos, heat synchronization and induction, and gametes cryopreservation have been more utilized in veterinary practice each day. Nevertheless, some techniques have not achieved their full technical capacity within the equine reproduction field, such as semen cryopreservation. The aim of this study was to evaluate the characteristics of post-thawing semen (total motility, strength, plasmatic and acrosomal membrane integrity) of Mangalarga Marchador breed stallions, using three different extenders (Botucrio, FR5 and FR6). Ejaculates from five stallions were collected and the gel-free semen was diluted in a 1:1 dilution in skim milk extender, and centrifuged at 600 g for 10 minutes. After the centrifugation the supernatant was removed and sperm pellet was divided and re-suspended using three different extenders to a concentration of 200 x 10 cells/mL. The samples were packed into 0.5 mL straws, placed in a stainless steel support and kept inside the refrigerator (5 C) for one hour. Subsequently, these straws were kept at a height of 6 cm from liquid nitrogen for 15 minutes in an isotherm box and, after that, plunged into liquid nitrogen (-196 C) and stored in a liquid nitrogen holding tank. There were no differences in the parameters evaluated when extenders using mixed amides and glycerol (Botucrio and FR6) were used (P > 0.05). All parameters evaluated were lower for the extender containing only glycerol (P<0.05). The use of cryoprotectants (methylformamide and dimethylformamide) in association with glycerol concentrations around 1 to 2% is an alternative for semen cryopreservation of Mangalarga Marchador breed stallions.

Avaliação de diferentes doses de eCG na ressincronização da ovulação em vacas nelore lactantes submetidas à IATF

The aim was to evaluate the use of eCG in resynchronization (RS) in lactating Nelore cows, understand the interaction between dose, presence or absence of estrus, presence or absence of the corpus luteum (CL) and pregnancy rate. Were used 775 cows in first TAI and that not pregnant (449) were resynchronized 30 days after. Ultrasound (US) to observe the presence or absence of CL was performed before first TAI and when the RS. On day 0 (D0) an intravaginal device (IVD) with 1 g of progesterone and intramuscular (IM) 2 mg estradiol benzoate was administered. On D8 devices were removed and applied IM 1mg estradiol cypionate; 0.53mg of sodium cloprostenol, Group - 0 (G0) didn´t received eCG, G200 received 200 IU and G300 300 IU. Estrus was observed and insemination (AI) performed 48 hours after the removal of the IVD. US was performed 30 days after AI. The treatments didn´t affect the occurrence of pregnancy in estrus. In cows that didn´t show estrus, there´s no difference in the occurrence of pregnancy between the G200 and G300 but with G0. The cumulative pregnancy rate after 40 days of the breeding season was (77.54%). The cumulative pregnancy rate in 40 days enables the RS as a way to optimize reproductive management on beef cattle farms.

TAXA DE GESTAÇÃO EM ÉGUAS DA RAÇA CRIOULA APÓS ASPIRAÇÃO FOLICULAR GUIADA POR ULTRASSOM

There are few studies about transvaginal ultrasoundguided follicle aspiration in equine medicine regarding potential complications to future fertility of aspirated mares. In order to evaluate the effect of follicular aspiration on subsequent fertility in mares, two experiments were conducted. In Experiment I, fifteen Criollo mares were allocated to one of three groups according to the diameter of the aspirated follicle during estrus: 25-29mm (n=4; Group 1); 30-34mm (n=6; Group 2);  35mm (n=5; Group 3) and control group (n=15; Group 4). In Experiment II, the follicular aspiration was attempted in twenty-five mares during diestrous, when at least four follicles ( 5mm) were seen in the transrectal ultrasonography of both ovaries. All visible follicles, between 4 and 8 mm, were aspirated. Thirty-one mares served as control. In Experiments I and II, the pregnancy rates in the following cycle after aspiration were 75.0% (Group 1), 83.3% (Group 2), 60.0% (Group 3), and 73.3% (Group 4 Control); and 76.0% in the aspirated diestrous group and 77.4% in the control group (non aspirated), respectively. On both experiments, pregnancy rates were similar (P>0.05) in treated and control mares. The results of this study show that the conception rates of the first estrus period following follicular aspiration are not affected by the procedure.

Pregnancy rates using frozen semen of Criollo stallions with glycerol or dimethylformamid as cryoprotectants

Pregnancy rates using stallionss frozen semen are variable; moreover, some breeds present low freezability. One hundred and four (104) mares were inseminated and separeted into two experiments to evaluate fertility of frozen semens of Criollo stallions (n=5), with 5% of dimethylformamide (DMF) or 5% of glycerol (GLY) as cryoprotectants. In Experiment I, the inseminations were made during pre-ovulation with fresh and frozen semen with DMF. In Experiment II, the mares were inseminated during post-ovulation with fresh semen, DMF and GL. The inseminations with frozen semen were performed deep in the uterine horn ipsilateralis to the dominant follicle. Control mares were inseminated with fresh semen in the uterus. Only one estrus period per mare was used to evaluate the pregnancy rates of the groups. Pregnancy diagnosis through ultrasonography was performed on the 15th day post-ovulation. The mean post-thawing motility was 40% and 20%, respectively, for frozen semen with DMF and GLY (P<0.05). All stallions had higher post-thawing motility when using DMF. In Experiment I, pregnancy rates were 12% (5/42) and 62% (20/32), respectively for DMF and fresh semen (P<0.0001). In Experiment II, pregnancy rates were 40% (4/10), 10% (1/10) and 70% (7/10), respectively for DMF, GLY (P<0.05) and fresh semen (P 0.0001). Insemination with frozen semen performed with more frequent follicular control showed the best results. The low sperm motility after thawing was attributed to the GLY used in experiment II. The DMF can be used alternatively to Criollos Stallions semen feezing.