PSI-7 - Evaluating the Relationship of Puberty Status at 10 Months of Age with Heifer Characteristics

Abstract: The objective was to evaluate the relationship of heifer puberty status at 10 months of age with body weight (BW), hair shedding score (HSS), and dam age. Puberty status was assessed at 10 months of age on 177 fall-born, Simmental × Angus heifers (birth date 9/26/2020 ± 18.7 d) using fabric heat patches (Estrotect; Hermitage, Tennessee) for 22 days. Patches were scored as 0, 50, or 100% activated with heifers scored 50 or 100% considered pubertal. Heifers with missing patches (n = 10) were excluded from the analysis. Heifers grazed endophyte-infected tall fescue pastures from 6 to 12 months of age. Heifers were assigned HSS at 10, 11, and 12 months of age. A HSS of 1 indicates a slick summer coat and a 5 is a full winter coat. The MIXED procedure of SAS 9.4 was used to analyze data. Heifers classified as pubertal at 10 months of age had greater (P = 0.01) birth BW than prepubertal heifers (33.1 kg vs. 30.8 kg, respectively). Heifers that were pubertal at 10 months of age also had greater (P ≤ 0.05) BW at 6, 8, 10, and 12 months of age than prepubertal heifers. Additionally, pubertal heifers had greater (P = 0.01) ADG from 6 to 12 months of age while grazing. Pubertal heifers tended (P = 0.10) to have a lesser, more desirable HSS at 10 months of age and had a lesser (P < 0.01) HSS at 11 and 12 months of age compared with prepubertal heifers. Dam age was not different (P = 0.60) between heifer puberty status at 10 months of age. In conclusion, pubertal heifers were heavier at birth, heavier from 6 to 12 months, and had more desirable HSS compared with prepubertal heifers at 10 months of age.