Abstract The objective was to evaluate individual intake and variation of both loose granular mineral and salt when offered concomitantly to beef cows grazing native Flint Hills rangeland. Over 76 d, intake of both a commercially manufactured mineral supplement (LM) and loose granular salt (LS) was recorded on a single herd using mobile precision feed intake bunks (SmartFeed Pro, C-Lock Inc., Rapid City, SD). Prior to trial initiation, cows underwent a 3-wk adaptation period to train to consume supplement from bunks. During adaptation and trial periods, bunk gates were locked open to allow animals ad libitum access to supplement from 1 of 2 bunks to mimic free choice consumption from a feeder used in typical production settings. Intake was measured on 43 mature, lactating and non-lactating, beef cows of either Angus, Simmental, or Hereford breeding. Daily visits and intake were recorded across 3 trial periods, and data were analyzed using the MIXED procedure of SAS with significance declared at P ≤ 0.05. Cows were managed as a common group and individually supplemented from precision intake bunks, thus individual cow was considered the experimental unit. Period 1 was 26 d, while Period 2 and Period 3 were each 25 d in length. Intake of LM was greater than LS across all periods (P ≤ 0.05). During Period 1, intake of LM (0.08 kg per hd per d) was greater (P ≤ 0.01) than LS (0.02 kg per hd per d). For standard deviation, LM intake was 0.11 kg per hd per day while 0.02 kg per hd per day was observed for LS. The percentage of daily visits for Period 1 was higher for LM compared to LS (27.9% vs 20.3%; P = 0.04). In Period 2, intake of LM (0.07 kg per hd per d) was still greater (P ≤ 0.01) than LS (0.02 kg per hd per d). Likewise, the standard deviation of LM intake (0.09 kg per hd per d) in Period 2 was greater than LS (0.03 kg per hd per d). Daily visit rate for LM (27.4%) was higher (P = 0.05) than LS (20.74%). Following calf weaning in Period 3, LM intake appeared to decrease slightly, while LS intake appeared to remain the same. Intake of LM was 0.06 kg per hd per d which was different (P ≤ 0.01) from LS (0.02 kg per hd per d). During period 3, the daily visit percentage of LM was 20.7% which was greater (P = 0.05) than LS (14.4%). Data suggest intake and variability of loose granular supplements can be measured using precision equipment, and both measurements are greater for supplements with carrier ingredients by cows grazing Flint Hills rangeland when concurrently offered salt.
Sollors et al. (Wed,) studied this question.