Feeding distiller’s grains as an energy source to gestating and lactating beef heifers: Impact on female progeny growth, puberty attainment, and reproductive processes.

This study compared postweaning growth, puberty attainment, and reproductive processes of female progeny (n = 33) born to Angus-Simmental beef heifers treated with either a control diet or a diet in which dried distiller’s grains with solubles (DDGS) were fed as an energy source during late gestation and early lactation. From 192 d of gestation through 118 ± 4 d in lactation, dams were fed either a corn silage–based control diet (CON) orcorn residue with DDGS, where DDGS were supplemented as an energy source (DG). Diets were formulated to provide similar daily NEg between diets, but CP requirements were drastically exceeded in the DG treatment. Heifer progeny (n = 33) were weaned, commingled at 191 ± 4 d of age, and similarly managed for the remainder of the project. Heifer BW and blood samples for progesterone assessment to determine onset of puberty were collected weekly beginning at weaning. At 255 ± 4 d of age, a single follicular wave was mapped via ultrasonography in 10 prepubertal heifers per treatment. Prepubertal antral follicle count and ovarian size were determined at 253 ± 4 d of age. Hip height was recorded at 213,297, and 437 ± 4 d of age. Estrous synchronization and AI was initiated at 447 ± 4 d of age. Binary data were analyzed with the GLIMMIX procedures of SAS and all other data were analyzed with the MIXED procedures of SAS. Progeny from DG-treated dams tended to be heavier (P = 0.08) than progeny from CON-treated dams from weaning until breeding. In addition, DG progeny had a greater (P < 0.01) frame score than CON throughout the developmental period. Ovarian size, antral follicle count, and follicular growth parameters did not differ between treatments. Age at puberty did not differ between CON (303 ± 10 d) and DG (320 ± 10 d) progeny; however, BW at puberty was greater (P = 0.01) for DG (326 ± 7 kg) than CON (298 ± 8 kg) progeny. Pregnancy rates to AI were greater (P = 0.05) in DG progeny (70.6%) than CON (33.3%), but overall breeding season pregnancy rate did not differ (P = 0.97). Moreover, rate of dystocia in female progeny at first parturition and grand-offspring birth BW did not differ due to treatment (P ≥ 0.74). In summary, feeding DDGS as an energy source during late gestation and early lactation to first-parity heifers resulted in female progeny with greater skeletal growth that were heavier at onset of puberty and had increased AI pregnancy rates.