Abstract The number of antral follicles is considered an important fertility trait because animals with a high follicle count (HFC) produce more oocytes and embryos per cycle. Identification of these animals by genetic markers such as single nucleotide polymorphisms (SNPs) can accelerate selection of future generations. The aim of this study was to perform a genome wide association study (GWAS) on Nelore and Angus heifers with HFC and low (LFC) antral follicle counts. The groups HFC and LFC for genotyping were formed based on the average of total follicles (≥ 3 mm) counted in each breed consistently ± standard deviation. A total of 72 Nelore heifers (32 HFC and 40 LFC) and 48 Angus heifers (21 HFC and 27 LFC) were selected and the DNA was extracted from blood and hair bulb. Genotyping was done using the Illumina Bovine HD 770K BeadChip. The GWAS analysis showed 181 and 201 SNPs with genotype/phenotype association (P ≤ 0.01) in Nelore and Angus heifers, respectively. Functional enrichment analysis was performed on candidate genes that were associated with SNPs. A total of 97 genes were associated to the 181 SNPs in the Nelore heifers and the functional analysis identified genes (ROBO1 and SLIT3) in the ROBO-SLIT pathway that can be involved in the control of germ cell migration in the ovary as it is involved in lutheal cell migration and fetal ovary development. In the Angus heifers, 57 genes were associated with the 201 SNPs, highlighting Fribilin 1 (FBN1) gene, involved in regulation of growth factors directly involved in follicle activation and development. In summary, GWAS for Nelore and Angus heifers showed SNPs associated with higher follicle count phenotype. Furthermore, these findings offer valuable insights for the further investigation of potential mechanism involved in follicle formation and development, important for breeding programs for both breeds. (HFC cycle (SNPs generations (GWAS (LFC counts ≥ ( mm deviation 7 32 (3 4 21 (2 2 bulb K BeadChip 18 20 genotypephenotype genotype phenotype P 0.01 001 0 01 respectively 9 ROBO1 ROBO (ROBO SLIT3 SLIT ROBOSLIT development 5 FBN1 FBN (FBN1 gene summary Furthermore breeds 0.0 00 (FBN 0.

Avaliaram-se os efeitos da remoção temporária de bezerros (RTB) ou da aplicação de gonadotrofina coriônica eqüina (eCG) na taxa de prenhez (TP) de vacas Nelore lactantes tratadas com um dispositivo intravaginal liberador de progesterona (DILP). No experimento 1, 83 vacas Nelore e 102 mestiças (Nelore × Red Angus) foram distribuídas em três grupos. Em dia aleatório do ciclo estral (D0), os animais do grupo 1 foram tratados com benzoato de estradiol (BE; 2,5 mg, IM, Estrogin®) e um DILP (1 g de progesterona, DIB®), removido no D9, quando também se administrou d-cloprostenol (150 µg, IM, Prolise®) e aproximadamente 12 horas após identificação do estro realizou-se a inseminação artificial. No grupo 2 (IATF), o tratamento foi semelhante ao aplicado no grupo 1, porém, administrou-se uma segunda dose de benzoato de estradiol (1 mg) no D10 e 30-36 horas mais tarde realizou-se a inseminação artificial em tempo fixo (IATF). No grupo 3 (IATF/RTB), os bezerros foram removidos a partir do D9 até a inseminação artificial com tempo fixo (IATF). As taxas de prenhez para as vacas Nelore e mestiças foram, respectivamente, de 7,69 e 41% (Controle); 23,52 e 59,57% (IATF); 69,44 e 55,81% (IATF/RTB). No experimento 2, 255 vacas Nelore lactantes foram distribuídas em três grupos. Os animais do grupo 4 (IATF) foram tratados com benzoato de estradiol (2 mg) e um DILP (1,9 g de progesterona, CIDR-B®) no D0 e no D8 sofreram remoção do DILP no D8 e administração de 25 mg de dinoprost (IM, Lutalyse®). No D9, foi aplicado benzoato de estradiol (1 mg) realizando-se a IATF 30-36 horas mais tarde. No grupo 5 (IATF/RTB), os bezerros foram removidos no D9 até a IATF. O grupo 6 (eCG) foi semelhante ao IATF, exceto pela aplicação de eCG no D9 (400 UI, IM, Novormon®). As taxas de prenhez foram de 50,57 (IATF), 53,57 (IATF/RTB) e 54,76% (eCG). A associação de RTB ao tratamento hormonal com DILP aumenta as taxas de prenhez, enquanto a adição de eCG ao tratamento não melhora as taxa de prenhez de vacas Nelore lactantes ciclando e em boa condição corporal.

This study aimed to evaluate the effects of temporary calf removal (TCR) or eCG administration on pregnancy rates of milking Nelore cows treated with a intravaginal progesterone releasing device (IPRD). In the first experiment 83 Nelore and 102 Nelore vs. Red Angus crossbred cows were randomly allocated to 3 groups. Animals in Group 1 (CON) received estradiol benzoate (EB; 2.5 mg, i.m., Estrogin®) and an IPRD (1g progesterone, DIB®) in a random stage of the estrous cycle (D0). At D9 the IPRD was removed and the animals were treated with d-cloprostenol (150µg, i.m., Prolise®). The animals were artificially inseminated (AI) 12 h after estrus detection. Group 2 (FTAI) was similar to CON, except that another dose of EB (1mg) was administered at D10, and 30-36 hours later artificial insemination (FTAI) was performed at a fixed time. In Group 3 (FTAI/TCR) the calves were removed from D9 to the FTAI. Pregnancy rates for Nelore and crossbred cows were, respectively, 7.69 and 41% (CON); 23.52 and 59.57 (FTAI); 69.44 and 55.81 (FTAI/TCR). In the second experiment, 255 lactating Nelore cows were allocated to 3 groups. At D0, animals in Group 4 (FTAI) received EB (2 mg) and one IPRD (1.9g progesterone, CIDR-B®), which was removed at D8 when the cows received 25 mg of dinoprost (i.m., Lutalyse®). At D9 EB (1 mg) was administered and 30-36 hours later all animas were FTAI. In Group 5 (FTAI/TCR) the calves were removed from D9 to FTAI. The Group 6 (eCG) was similar to IATF except for the administration of eCC in D9 (400 IU, i.m., Novormon®). Pregnancy rates were: 50.57% (FTAI), 53.57% (FTAI/TCR) and 54.76% (eCG). These results indicated that TCR associated with IPRD increase pregnancy rates, whereas the addition of eCG to IPRD do not improve pregnancy rates in Nelore cows which are cycling and in lactation with good body condition.