Reproductive tract development and puberty in two lines of Nellore heifers selected for postweaning weight

AbstractThe objective was to evaluate reproductive tract development (ovary and uterus) and onset of puberty in two lines of Nellore heifers (Bos indicus) selected for postweaning weight. A total of 123 heifers, including 46 from the control Nellore line (NeC) and 77 from the selection Nellore line (NeS) were used. Every 18 to 21 days from 12 to 24 months of age, average ovarian area (OVA), endometrial thickness (ETh), and diameter of the largest follicle in each ovary were evaluated (using transrectal ultrasonography), and body weight, hip height, and body condition score were measured. There were no differences between NeS and NeC heifers for ETh or OVA (P < 0.05). Genetic selection for higher postweaning weight had no negative influence on the onset of puberty, with 52% and 48% of NeC and NeS heifers, respectively, pubertal at 24 months of age (P = 0.49). Heifers that reached puberty at the end of the study were heavier (NeC, 296.9 vs. 276.7 kg; NeS, 343.5 vs. 327.9 kg; P < 0.01) and younger (NeC, 23.4 vs. 24.2 mo; NeS, 22.7 vs. 24.0 months; P < 0.01) than those that did not. Furthermore, heifers that were heavier at weaning reached puberty earlier. Pubertal heifers had a greater OVA (4.15 vs. 3.14 cm2; P < 0.01) and ETh (12.15 vs. 9.93 mm; P < 0.01) than nonpubertal heifers. Taken together, OVA and ETh had positive effects (P < 0.01) on the onset of puberty and were suitable indicator traits of heifer sexual precocity in pasture management systems. However, selection for weight did not alter ovarian or endometrial development, or manifestation of puberty at 24 months of age. Among the growth traits studied, weaning weight and weight at puberty had significant positive effects on manifestation of first estrus

Optical mapping compendium of structural variants across global cattle breeds

Structural variants (SV) have been linked to important bovine disease phenotypes, but due to the difficulty of their accurate detection with standard sequencing approaches, their role in shaping important traits across cattle breeds is largely unexplored. Optical mapping is an alternative approach for mapping SVs that has been shown to have higher sensitivity than DNA sequencing approaches. The aim of this project was to use optical mapping to develop a high-quality database of structural variation across cattle breeds from different geographical regions, to enable further study of SVs in cattle. To do this we generated 100X Bionano optical mapping data for 18 cattle of nine different ancestries, three continents and both cattle sub-species. In total we identified 13,457 SVs, of which 1,200 putatively overlap coding regions. This resource provides a high-quality set of optical mapping-based SV calls that can be used across studies, from validating DNA sequencing-based SV calls to prioritising candidate functional variants in genetic association studies and expanding our understanding of the role of SVs in cattle evolution