Table 5.
Feed intake and plasma variables in rumen-cannulated heifers receiving feedlot diets containing (2 × 2 factorial arrangement): 1) monensin + tylosin (360 mg/steer daily from Rumensin 90 and 90 mg/steer daily from Tylan 40; Elanco Animal Health, Greenfield, IN) and 2) Y. schidigera extract (4 g/steer daily, as-fed basis; Micro-Aid Feed Grade Concentrate; DPI Global, Porterville, CA)1,2
| Item | Monensin + tylosin (A) | Y. schidigera extract (B) | P-values | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Yes | No | SEM | Yes | No | SEM | A | B | A × B | |
| Feed intake (dry matter),3 kg/d | 12.1 | 12.9 | 0.6 | 12.6 | 12.5 | 0.6 | 0.42 | 0.89 | 0.99 |
| Plasma variables | |||||||||
| Glucose, mg/dL | 76.8 | 77.2 | 1.4 | 78.3 | 77.7 | 1.4 | 0.76 | 0.58 | 0.33 |
| Insulin, ng/mL | 34.0 | 38.1 | 5.5 | 33.7 | 38.4 | 5.5 | 0.50 | 0.42 | 0.82 |
| Insulin-like growth factor I, ng/mL | 77.7 | 75.6 | 6.5 | 75.6 | 77.7 | 6.5 | 0.73 | 0.73 | 0.52 |
| Urea-N, mg/dL | 17.5 | 15.8 | 0.9 | 16.0 | 17.3 | 0.9 | 0.21 | 0.32 | 0.88 |
1Heifers were assigned to a 4 × 4 Latin square design, containing four periods of 21 d each and a washout interval of 14 d between periods. During each 21-d period, heifers were housed in drylot pens equipped with electronic feed bunks (GrowSafe Systems Ltd, Airdrie, AB, Canada) that measured individual feed intake.
2Individual feed intake was computed daily using the GrowSafe 6000E software (GrowSafe Systems Ltd) as described by Parsons et al. (2020). Blood was sampled prior to feeding (0700 h) on the first day of each period, and 4 h after feeding (1200 h) on the final day of each period. Results obtained on the first day of each period were used as independent covariate in each respective analysis.