Intake behaviors of yearling steers grazing irrigated pasture and receiving either a free-choice salt-based mineral or a low-moisture molasses-based tub mineral

Abstract

Abstract Mineral intake in grazing cattle is highly variable and research evaluating behavioral aspects of intake are minimal. Development of the GrowSafe System to monitor feed intake allows researchers to record individual feeding behaviors of cattle 24 h per day. In the current experiment conducted during June and July, the GrowSafe System was utilized to evaluate intake behaviors of grazing steers during a short-term free-choice supplementation of either salt-based loose minerals (LM; n = 24; 408 ± 57 kg) or low-moisture molasses-based tub minerals (TUB; n = 24; 396 ± 64 kg). Each treatment was randomized to two of the four irrigated pastures (~5 ha each) consisting of orchard grass (Dactylis glomerat L.), red clover (Trifolium pretense L.), and smooth brome (Bromus inermis). Individual intake was evaluated over three 7-d periods: d – 7 to 0 (adaptation period; AP), d 1 to 7 (period 1; P1), and d 15 to 22 (period 2; P2) of the experiment. The LM mineral mix contained 28% salt during the AP and more salt was added at the initiation of P1 to prevent excessive mineral intake observed during the AP. The LM mineral mix contained 38% salt during P1 and P2. Daily bunk attendance was greater (P < 0.001) for LM (93%) than TUB (67%) steers for the AP. Whereas there was a treatment × period effect (P < 0.001) on daily bunk attendance across P1 (LM: 92%; TUB: 64%) and P2 (LM: 91%; TUB: 82%). Daily mineral intake (as-fed) was greater (P < 0.001) for LM (568 g) than TUB (283 g) during the AP. For P1 and P2, there were no treatment (P = 0.46) and period (P = 0.77) effects on daily mineral intake (LM, 370 g vs. TUB, 343 g), but LM (3.1 visits) had more (P < 0.001) bunk visits per day than TUB (2.0 visits). During the AP, LM (8.5 min) had a greater (P = 0.04) duration of mineral intake per day than TUB (5.6 min); whereas during P1 and P2, TUB (P1 = 8.6; P2 = 12.8 min) had a greater (P ≤ 0.05) duration of mineral intake per day than LM (P1 = 4.9; P2 = 5.7 min). In conclusion, mineral delivery method significantly affected bunk attendance, number of bunk visits per day, and time spent consuming mineral. These results provide additional evidence that mineral type and associated feeding behaviors contribute to the significant variation observed in daily mineral intake in grazing cattle.