This study aimed to determine the effect of antral follicle count (AFC), and pubertal status on the fertility of beef heifers. In this study, 230 Nelore heifers, 20±2 months of age, were subjected to an estradiol progesterone-based timed artificial insemination (TAI) program. On Day 0 of the TAI protocol, the heifers were examined by transrectal ultrasound to record videos of the ovaries. Later, in the darkroom of the laboratory of images, the videos were analyzed for AFC (≥ 3 mm) of each ovary. Females who failed the first TAI were resynchronized with the same hormonal protocol. The pregnancy status was evaluated by ultrasonography 30 days after each FTAI. The general mean of the AFC was 22.0 follicles. Thus, the heifers were divided into 2 groups according to AFC: Low AFC (˂ 22 follicles, n = 114), and High AFC (≥ 22 follicles, n = 116). No differences (P > 0.05) in the pregnancy per AI (P/AI) were observed between the Low and High AFC groups, and between pubertal and prepubertal categories. The P/AI was not different between heifers that displayed or did not estrus (P = 0.2). However, considering the estrus response of each AFC group, High AFC heifers that displayed estrus had greater P/AI (P = 0.01) than High AFC heifers that did not display estrus. In summary, AFC and pubertalstatus did not affect the fertility of Nelore heifers. In contrast, the P/AI of heifers that did not display estrus was lower than heifers observed in estrus only in the High AFC group.

Objective: As one of the most valuable genetic resources of Ongole beef cattle globally, the Sumba Ongole (SO) cattle population is being studied in this investigation of myostatin (MSTN) gene polymorphism and its association with growth traits. Materials and Methods: Blood samples from 161 SO cattle were collected and analyzed. Deoxyribonucleic acid (DNA) was isolated. The DNA was electrophoresed and extracted, and finally, the annealing temperature was optimized, followed by amplification and sequencing. Next, we used a Basic local alignment search tool to assess the sequencing data. Results: The analysis revealed 22 single nucleotide polymorphisms (SNPs) in the MSTN gene in this region that showed genetic variation. Two SNPs, c.424 G > A, and c.467 G > C, were found to be significantly associated with SO cattle phenotypes of wither height, heart girth, and hip height (p < 0.05) but not with body weight or body length (p > 0.05). Conclusion: As a result of our findings, the MSTN gene polymorphism and its correlation with growth traits in SO cattle may be employed as a candidate marker in SO cattle and other beef cattle breeds. [J Adv Vet Anim Res 2022; 9(4.000): 565-572]