PSI-2 Spices in Free-choice Mineral Offer Gain Advantages to Cattle on Tallgrass Native Range and Promise as Fly Control

Abstract This study aims to evaluate effectiveness of two operational management systems for steer gains and fly control. The first strategy evaluated was pasture burn date of March (MAR) or April (APR). The second management strategy was fly control through feeding free-choice mineral with spices (SPICE) or without spices (CON). Eight pastures (n = 281 steers; initial weight 277.7 ± 25.2 kg) were used in a 2 x 2 factorial treatment structure. Steers were weighed individually, randomly assigned to treatment, and grazed for 85 days. Weekly 33% of steers per pasture were photographed and fly numbers counted. ADG was impacted by both burn date and mineral type (P = 0.01). Cattle on the APR-SPICE treatment had a greater ADG than MAR-SPICE and APR-CON with MAR-CON intermediate. Cattle on SPICE gained 4.5 kg (P = 0.12) more than cattle consuming CON mineral. Flies per steer were impacted by burn x mineral x week (P < 0.001). In general, APR-SPICE steers had a greater number of flies weeks 8, 10, and 11 (P < 0.05), corresponding to a time when mineral intake averaged 72% of the formulated intake. The MAR-SPICE steers consumed on average the formulated amount of mineral and through the entire grazing period had lower number of flies than APR-SPICE steers (P < 0.05). The second largest ADG observed with the MAR-CON treatment may be attributed to lower fly numbers as this treatment had one extra week below economic threshold for horn flies. These results are somewhat inconclusive on pasture burn date, but show that the addition of spices to a free-choice complete mineral shows promise as a cost-effective method to increase gains in stocker steers on tallgrass native range. As a fly control method, the spices utilized in this study may be effective if intake is at formulated level.