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 (7yr of age, n = 16; 727 kg BW) were used in a complete randomized design with a 2 x 2 factorial arrangement of treatments 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 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, Generalized Linear Mixed 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 asymptotically increased the rate of bolus degradation (P = 0.05; Beta protein supplementation = -3.13 + or - 0.34), while the addition of a fly bolus asymptotically reduced VTM bolus degradation rates (P = 0.05; Beta fly bolus = -1.79 + or - 0.34). In study 2, degradation rate for all bolus prototypes differed, apart from boluses A and B (P = 0.52; Beta = -2.52 + or - 1.27). Bolus prototypes C and D had increased degradation rates compared to A and B with C degrading quicker than D (P < or = 0.05; Beta C = -12.15 + or - 1.48 and Beta D = -4.95 + or - 1.48). Additionally, bolus prototypes A, B, C, and D degraded asymptotically. 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.