PSXIV-18 Impact of stocking method on heifer performance and reproductive outcomes.

Abstract Areas of the Great Plains have been experiencing a reduction in forage land base, leading to the need for more efficient stocking strategies to optimize beef production. The objective of this experiment was to evaluate heifer performance when managed under continuous season-long stocking (CSLS) or modified intensive early stocking (MIES) conditions. Across five years, 474 heifers were utilized and subjected to either CSLS or MIES which was defined at heifers stocked at 1.6× CSLS May through July and 1× for the rest of the season. Heifer body weight and body condition score were recorded at season start (May), mid-season (July), and end (October). Heifers were examined for pregnancy via transrectal ultrasonography between 30 and 35 days following fixed-time artificial insemination (AI), and again at the end of the grazing season to assess final pregnancy status. Data were analyzed using the MIXED procedure of SAS 9.4 (SAS Institute, Cary, NC), with treatment included as a fixed effect year(pasture) as a random effect. The early grazing period was defined as May through mid-July, and the late period as mid-July through October. During the early grazing period, CSLS heifers had greater average daily gain than MIES heifers (P < 0.001), with a tendency for increased average daily gain in CSLS heifers during the late grazing period (P = 0.071). Total average daily gain was also increased in CSLS heifers compared to the MIES group (P = 0.016). Body condition score did not differ between treatments throughout the grazing season. MIES heifers had greater early gain per acre than CSLS heifers (P < 0.001), with a similar effect observed during the late grazing period (P < 0.001). The proportion of heifers that conceived to first-service AI was 0.456 and 0.4567 for the CSLS and MIES, respectively. The MIES system successfully translated beef stocker efficiencies into a replacement heifer framework without compromising reproductive outcomes. Despite early-season stocking at 1.6× density, MIES heifers attained comparable first service AI conception rates, body weights, and body condition scores to continuously stocked cohorts although the CSLS heifer did have higher total average daily gain. These findings demonstrate that MIES can increase production output per acre in semi-arid western Kansas while preserving heifer fertility, offering producers a viable strategy to improve production efficiency on diminishing rangeland resources.