Abstract Managing bunks correctly is critical for maximizing feedlot performance. Feedlots primarily use either an ad-libitum system where cattle have the full 24 h to consume feed, or a slick bunk system where a specific feed access time is targeted for cattle to finish their feed prior to the next day’s feeding. A finishing experiment was conducted to evaluate the effects of feed access time on feedlot performance, feeding behavior, ruminal pH and carcass characteristics in yearling heifers. Heifers (n = 234; initial BW = 447 kg, SD = 36 kg) were fed in a randomized complete block design and blocked by body weight into eight pens, each equipped with five electronic feed bunks (Insentec Roughage Intake Control System, Hokofarm Group). Heifers were assigned randomly to one of five feed bunks within each pen, and bunks were assigned randomly to one of five treatments. Treatments were based on access time to feed, either 12, 15, 18, 21, or 24 h of access to feed beginning at 0830 each day. All heifers were fed a common step-up and finishing diet and individual animal dry matter intake and feeding behavior were collected for 104 days. A subset of heifers (n = 16) from the same pen received pH boluses (Moonsyst International) on d 0 (n = 3-4 boluses/treatment). Data were analyzed using a mixed model including treatment and pen as fixed effects. Orthogonal contrasts were used to test linear, quadratic and cubic effects of feed bunk access time. There were no differences in carcass adjusted final BW, ADG, or G:F (P ≥ 0.11). As feed access time increased, dry matter intake increased linearly (P 0.01). The DMI of heifers allowed 24 h was 4.9% greater than 12 h, but not different compared to 15, 18, or 21 h treatments. The day-to-day variation (CV) of DMI (P = 0.02) and the incidence of liver abscesses (P = 0.03) increased linearly as feed access time increased. As access time to feed increased from 12-h to 24-h, bunk visit duration, and the day-to-day variation of bunk visit duration increased linearly (P 0.01), and a linear decrease was observed in eating rate as g DMI/min (P 0.01) with heifers having 12 h access time eating 14% faster compared to heifers having 24 h of feed access. As access time to feed increased, the magnitude of ruminal pH change within a day decreased linearly (P 0.01), as cattle having less feed access time exhibited a greater intraday pH change. Feed access time greater than or equal to 15 h did not negatively impact DMI, ADG or HCW as cattle modified their behavior based on the feed access time available to them.
Loseke et al. (2026) studied this question.