Individual intake of mineral and molasses supplements by cows, heifers and calves

In two pastures, two multiplex radio frequency (RF) mineral feeders (GrowSafe Systems Ltd.) equipped with load cells were used to monitor feeder attendance and individual intake of mineral by 33 and 36 cow-calf pairs individually identified by RF transponders. A visit was defined as a return to the feeder after a 5-min absence. In exp. 1, attendance of cows and calves at the feeder and intake of mineral were monitored over 13 d. Sodium chloride was included in the mineral at 9.8% (low salt, LS) on days 1 to 6, and at 22.5% thigh salt, HS) on days 7 to 13. Percentages of cows and calves that visited the feeder were similar between LS (60.9% and 21.7% respectively) and HS (62.3% and 24.6%). Number of visits (P > 0.05) and daily mineral intake (P < 0.1) were reduced in cows fed HS as compared with LS. Cows had more visits (P < 0.001) and consumed more mineral (P < 0.001) than did calves. In exp. 2, HS as is (control, C) or formulated to contain 0.468% fenbendazole (FB) was provided far 6 d to 36 and 32 cow-calf pairs in adjacent pastures. All of the cows and 93.8% of the calves attended the FB feeder, whereas only 77.8% of the cows and 33.3% of the calves attended the feeder containing C. Fenbendazole increased visits per day (P < 0.05) by both cows and calves. Intakes of FB and C did not differ, but cows consumed more (P < 0.001) mineral than did calves. In exp. 3, variability in intake of protein-molasses blocks by cows and heifers was examined. Intake differed by animal (P < 0.01), but was similar between cows and heifers. Individual average intake was 445 g d(-1) with a range of 0 to 1650 g d(-1). These experiments demonstrate that universal and uniform consumption of an additive in mineral or molasses supplements by individuals in a herd cannot be assumed.