132 Weight and Reproduction Response to a Peanut Skins Plus Corn Supplement Offered to Heifers Grazing Spring Wheat Pasture During Artificial Insemination Breeding

Abstract

The objective was to assess heifer weight and reproduction response to a peanut skins plus corn supplement during spring wheat grazing. In spring of 2021 and 2022, 10 and 8 pastures (1.62 ha/pasture) of fall overseeded wheat were randomly assigned to supplement (SUP) or control (CONT) constrained to the same number of replications per treatment. Pastures were stocked with 6 heifers/pasture each year. The initial goal was to use peanut skins as a single ingredient; however, testing palatability in year 1, before spring grazing, demonstrated a need to create a mixed supplement for improved acceptance. Over 5 weeks from initiation of grazing to breeding, heifers were transitioned from a 33:67 to a 50:50 peanut skins:corn mix. Supplement was offered at 0.5% BW, as-fed, at the start of spring wheat grazing in early March. An additional 2.4% and 8.3% inclusion of dried molasses was incorporated to further enhance acceptance in year 1 and 2, respectively. Estrus synchronization (ES) began March 31 and April 5 for each year. Data were analyzed across year with year considered as a random effect and pasture the experimental unit. Initial weight was 12 ± 5.8kg greater (P = 0.05) for SUP. Weight at ES tended (P = 0.11) to be 9.4 ± 5.55kg greater for SUP. Reproduction tract score was similar (P = 0.55), averaging 4.2 ± 0.13, and heifers were of similar (P = 0.33) age (405 ± 4.1 days) at time of insemination. Average daily gain from initial wheat grazing until removal for natural service breeding did not differ between treatments (P = 0.92) and averaged 1.0 ± 0.21 kg. Body condition score was similar (P = 0.43) at ES and averaged 5.7 ± 0.7. The heavier initial BW of SUP heifers was sustained through wheat grazing (P = 0.05). Ultrasound determined pregnancies averaged 66.7 and 50.0 ± 6.6% for SUP and CONT, respectively, for an odds ratio of 2.1 ± 0.79 (P = 0.08) at 30 days after insemination. Overall pregnancy rates following natural service averaged 88.9 and 79.6 ± 4.88% for SUP and CONT, respectively with an odds ratio of 2.1±1.12 (P=0.19). High dietary protein has been associated with reduced reproductive performance. Using the peanut skins plus corn supplement was hypothesized to improve reproduction on a high protein diet due to the possible effect of peanut skins tannins on dietary protein utilization and corn altering the rumen degradable protein to organic matter ratio. While the fixed time artificial insemination pregnancy rates for CONT would not be considered poor, there was a tendency for SUP to secure more pregnancies among heifers of similar age, reproductive tract score, and body condition.