184 Degradation characteristics of ruminal sustained-release vitamin/mineral boluses

Abstract Two studies were conducted to evaluate the efficacy of ruminal sustained release vitamin/mineral (VTM) prototype boluses as an alternative mineral supplement delivery method for beef cattle. In study 1, 16 cannulated cows (age & BW) were used in a complete randomized design with a 2 × 2 factorial arrangement to evaluate the effects of protein supplementation (0.23 kg CP/day, versus no CP supplementation) and the addition of a fly control bolus (Altosid IGR XRB; Central Life Sciences, Schaumburg, IL) on the degradation rates of a VTM mineral bolus over a 126-d study period grazing dormant forage (4 cows per treatment). In study 2, the same 16 cannulated cows were used in a complete randomized design to evaluate degradation rates of four VTM bolus types (Three 150-d degradation target, A, B, and D, and one 90-d degradation target, C; n = 4/bolus type) while cattle grazed 127 days from Spring through early Fall. Cattle diet quality samples were collected every 3 to 6 weeks throughout study 1 and study 2. In study 1, R was used for statistical analysis with models containing both an asymptotic interaction of day and protein supplementation and an asymptotic interaction of day and the addition of a fly bolus were supported for predicting bolus degradation rates. Protein supplementation increased the rate of bolus degradation (P = 0.05; βprotein supplementation = -3.13 ± 0.34), while the addition of a fly bolus reduced VTM bolus degradation rates (P = 0.05;βfly bolus = -1.79 ± 0.34). In study 2, degradation rate for all bolus prototypes differed, apart from boluses A and B (P = 0.52; β= -2.52 ± 1.27). Bolus prototypes C and D had increased degradation rates compared to A and B with C degrading quicker than D (P ≤ 0.05; βC = -12.15 ± 1.48 and βD = -4.95 ± 1.48). Additionally, bolus prototypes A, B, and D degraded asymptotically, while bolus C degraded linearly. Across both studies, none of the prototypes evaluated met the target release rates. Degradation characteristics of VTM Bolus prototype were influenced by protein supplementation and the addition of a secondary fly bolus.