Effects of maternal bovine appeasing substance, metaphylaxis with tulathromycin, or a combination of both in high-risk, newly received feedlot heifers

Objective

Our objective was to evaluate effects of maternal bovine appeasing substance and metaphylaxis using tulathromycin on health and performance of feedlot heifers during a 63-d receiving period.

Materials and Methods

High-risk beef heifers (n = 552; initial BW = 187 ± 7 kg) were stratified by initial BW and pre-existing ranch tag and randomly assigned to 1 of 4 treatments arranged in a 2 × 2 factorial: (1) maternal bovine appeasing substance administration on d 0 and 14 (FERA), (2) metaphylaxis with tulathromycin on d 0 (META), (3) FERA and META administration (FERAMETA), and (4) no FERA or META (CON). A generalized complete block design was used, where heifers were blocked by truckload (n = 5), with each block consisting of 2 pens per treatment. Tulathromycin was administered subcutaneously in the neck at 2.5 mg/kg of BW. A total of 5.0 mL of maternal bovine appeasing substance was administered topically directly behind the poll, and 5.0 mL was administered directly above the muzzle.

Results and Discussion

Heifers administered FERA tended to have reduced morbidity from bovine respiratory disease, and the main effect of META reduced percentage of initial, secondary, and tertiary treatment for bovine respiratory disease. Total antimicrobial cost and units administered were less for META. Heifers that received META had greater ADG from d 0 to 14 and overall (d 0 to 63). An interaction existed for G:F from d 0 to 63 such that FERA was the greatest, META and FERAMETA were intermediate, and CON was least.

Implications and Applications

Health and performance of high-risk feedlot heifers was improved by META, and the combination of FERA and META may have additive benefit.