Starch and digestible fiber-based supplementation impact on first calf heifer performance and nutrient mobilization through the production cycle.

A study at the ISU McNay Research Farm in south central Iowa observed 2-year-old heifers from their first parturition over the course of a production year. From calving through four weeks post-AI, heifers were allocated to one of three treatment groups: an unsupplemented control, a corn supplement group (CORN), or a gluten supplement group (GLU). Supplements were delivered through a Super SmartFeed™ feeder, from C-Lock Inc., which utilizes EID tags to provide a set amount of supplement to individual animals. Supplement levels (5.56 lbs for CORN and 6.12 lbs for GLU) were based on a hay sample analysis for the first month after calving, when hay made up the base diet and were adjusted (2.38 lbs for CORN and 2.95 lbs for GLU) when pasture became the primary forage source and hay feeding ceased. For the pasture supplement level, assumptions were made on the pasture quality. Variables collected included carcass ultrasound measures (rib fat, ribeye area, intramuscular fat) and body weight at five time points from about one month prior to the expected start of the 2023 calving season to about one month prior to the start of the 2024 calving season. The 2023 calf weaning weights were collected and the first two cycles of calving in 2024 were used to confirm pregnancy data. The high nutritional demands of peak lactation caused females to lose weight and condition between calving and breeding season. Heifer numbers utilized in the study limited the statistical differences observed, but when observing numeric differences, unsupplemented heifers had the poorest condition at the time of synchronization. Supplementing first calf heifers improved conception to artificial insemination and the number of open heifers after the 65-day breeding season. Likewise, supplementation treatments averaged a 25-pound 205 adjusted weaning weight advantage compared to calves nursing unsupplemented dams. In addition to heifer and calf performance measures, cool season, unimproved fescue-based pasture samples were taken weekly during the supplementation period and analyzed for yield and quality. The results showed that pasture quality was overestimated and drought significantly restricted quantity. Applying some simple math can help evaluate the supplement return on investment. To limit our example to just the corn-supplemented group, the weaning weight advantage was 18 lbs/calf. If we assume a calf price of $2.50/lb, that’s about a $45 added value. On average, each heifer in the corn group consumed just shy of 5 bu of corn per heifer. At $6.23/bu, corn was $31/heifer for the supplementation period. In this scenario, the economics dictated that supplementation of first calf heifers from calving to breeding was economical, even without considering the next calf crop’s advantage from CORN realizing fewer open heifers and more calves sired AI.