129 Late-Breaking: Effect of adopting multiple management technologies on cattle performance in a small grazing beef cow-calf system: impacts on reproductive performance.

Abstract This three-year experiment evaluated the effects of adopting proven technologies on the performance of a grazing beef cow-calf system. A total of 108 Brangus cows were assigned to 1 of 2 cow-calf systems: 1) high technology (HT; n = 46) or 2) low technology (LT; n = 62). Cows from each treatment were allocated to 3 groups and evaluated for 3 consecutive years using the criteria described in Table 1. All animals grazed bermudagrass during the spring/summer, ryegrass during the winter and were supplemented with bermudagrass hay during the fall. Each HT replicate was stocked at 2 cows/ha, with priority grazing given to primiparous heifers and females with lower body condition scores (BCS). LT replicates were continuously stocked at 1 cow/ha. HT females were synchronized for artificial insemination (AI) and exposed to a bull 14 d post-AI. LT females were exposed to a bull for 60 ± 5-d. Pregnancy rates were calculated 42 ± 4 d following AI and bull removal. BCS were recorded at calving for all females. Replacement females were developed for both systems, with 50% of needed replacements being purchased for the HT system. Ionophores were fed through creep feed -70 d prior to weaning in the HT system. Weaning occurred at an average d 205 ± 10 post-calving. Treatments did not affect (P = 0.74) BCS of cows, but HT vs. LT cows had greater (P = 0.05) pregnancy rates in yr 1 (82.1 vs. 64.9 ± 5.6%) and yr 2 (92.6 vs. 78.3 ± 5.6%), but not yr 3 (83.3 vs. 88.1 ± 5.6%). During the calving season, calving rate was greater (P < 0.01) for HT vs. LT females in yr 1 (wk 3 – 9), yr 2 (wk 1 – 5) and yr 3 (wk 1 - 4). Besides no effects of treatment on calf birth BW (P ≥ 0.56), HT vs. LT calves were heavier (P < 0.01) at weaning in yr 1 (279 vs. 251 ± 3.73 kg), yr 2 (297 vs. 247 ± 3.70 kg) and yr 3 (268 vs. 248 ± 3.74 kg). Replacement heifer BW at the beginning of the breeding season was heavier (P < 0.01) in HT vs. LT heifers during yr 1(336 vs. 288 ± 7.95 kg) and yr 2 (376 vs. 298 ± 9.27 kg), then tended to be heavier (P = 0.09) in HT vs. LT heifers in yr 3 (341 vs. 322 ± 7.95 kg). Pelvic area was greater (P = 0.03) in HT vs. LT heifers (161 vs. 150 ± 2.90 cm2). Data suggests that implementing management technologies, including AI, creep feeding with ionophores, and rotational grazing, can lead to improved female performance and heifer development for small beef cattle producers.