Effects of Increasing Supplemental Zinc to Non-Implanted and Implanted Finishing Steers
Saturday, February 1, 2025
Steroidal growth implants are routinely used in the finishing phase of beef production to improve animal performance and feed efficiency. Data collected during the USDA’s National Animal Health Monitoring System’s Feedlot 2011 study showed that about 94% of heifers and steers were implanted at least once in the feedyard.1 Implants increase average daily gain (ADG) of cattle by 16% to 20%.2,3 Zinc functions as an essential component of a number important enzymes and proteins in the body and has a vital role in protein synthesis.4 Research suggest that the administration of growth implants may increase the zinc requirements of the animal to accommodate increased growth rates and greater supplementation of zinc may promote implant-induced growth.5,6 Therefore, Iowa State University researchers conducted a study to determine the effects of increasing dietary zinc supplementation within steroidal implanted and non-steroidal implanted steers on performance, carcass characteristics, liver and plasma zinc concentrations, and the expression of genes associated with growth and zinc metabolism.7
In this 59-day study, 128 Angus-crossbred steers (1,085 lb) were utilized in a complete randomized design arranged as a 2 Å~ 4 factorial resulting in 8 treatments to test the effect of zinc supplementation within steroidal implant treatment. Implant strategies included no implant (NoIMP) or Component TE-200 (IMP; Elanco, Greenfield, IN) administered on day 0. The cattle were supplemented with zinc at 0, 30, 100, or 150 ppm of zinc (dry matter basis: Zn0, Zn30, Zn100, or Zn150, respectively) from zinc sulfate starting on day 0. Zinc treatments were added to the diet through dried distiller grains with solubles-based premix. Prior to the start of the experiment, all steers received a corn silage-based growing diet supplemented with 30 ppm zinc from zinc sulfate. The steers were fed once daily (8:00 am) ad libitum and transitioned to a dry-rolled corn-based diet during the first 14 days of the experiment and remained on the finishing diet through the remainder of the 59-day study.
Steers were stratified by body weight (BW) to pens (5 or 6 steers per pen) equipped with GrowSafe bunks (GrowSafe Systems Ltd., Airdrie, AB, Canada) and assigned treatments (15, 16, or 17 steers/treatment). Cattle were weighed on days -1, 0, 18, and 59. Radio-frequency tags on each steer relayed individual steer feed disappearance data from the bunk to GrowSafe software. All cattle within a pen received the same steroidal implant and supplemental zinc treatment, and individual intake and performance data were collected for each steer. Only the performance data will be covered in this update.
The effects of zinc supplementation on the performance of non-implanted and implanted feedlot steers are shown in Table 1. Day 18 BW and days 0 to 18 ADG, and days 0 to 18 gain efficiency (G:F) linearly increased as zinc supplementation increased within the implanted cattle (P ≤ 0.02). Implanted steers also tended to have greater days 0 to 18 dry matter intake (DMI) than non-implanted steers (P = 0.09). Zinc supplementation did not influence performance of non-implanted steers. As would be expected, days 0 to 18 ADG and gain efficiency were greater for implanted steers than non-implanted steers (P ≤ 0.01).
By the end of the trial, implanted steers were 18.2 and 29.2 lb heavier than non-implanted steers for day 59 BW and carcass-adjusted final BW, respectively (P ≤ 0.002). As would be expected, implanted steers had greater days 0 to 59 and carcass-adjusted ADG and G:F (P ≤ 0.02). However, days 0 to 59 DMI was not influenced by zinc supplementation or implant treatment (P ≥ 0.15). A tendency for a linear increase due to zinc supplementation in carcass-adjusted final BW and ADG was observed in implanted steers (P ≤ 0.10),
| Item | Zn0 | Zn30 | Zn100 | Zn150 | Zn0 | Zn30 | Zn100 | Zn150 | Linear NoIMP | Linear IMP | NoIMP vs. IMP |
|---|---|---|---|---|---|---|---|---|---|---|---|
| No Implant | Implant – TE200 | Contrasts3 | |||||||||
| Steers, # | 17 | 15 | 16 | 16 | 15 | 16 | 16 | 16 | |||
| Body weight, lb | |||||||||||
| day 0 | 1080 | 1091 | 1082 | 1085 | 1091 | 1085 | 1085 | 1078 | 0.99 | 0.67 | 0.98 |
| day 18 | 1164 | 1173 | 1173 | 1171 | 1171 | 1177 | 1177 | 1190 | 0.34 | 0.002 | 0.005 |
| day 59 | 1312 | 1314 | 1329 | 1314 | 1334 | 1338 | 1340 | 1329 | 0.50 | 0.81 | 0.002 |
| days 0 to 18 | |||||||||||
| ADG, lb | 4.43 | 4.94 | 4.89 | 4.81 | 4.78 | 5.09 | 5.11 | 5.84 | 0.34 | 0.002 | 0.005 |
| DMI, lb | 25.1 | 24.7 | 24.7 | 26.7 | 25.4 | 25.1 | 25.8 | 26.5 | 0.11 | 0.09 | 0.52 |
| G:F | 0.177 | 0.192 | 0.200 | 0.181 | 0.188 | 0.203 | 0.199 | 0.222 | 0.71 | 0.02 | 0.01 |
| Carcass-adjusted overall4 | |||||||||||
| Final BW | 1310 | 1307 | 1323 | 1307 | 1332 | 1336 | 1345 | 1351 | 0.81 | 0.10 | <0.0001 |
| ADG, lb | 3.75 | 3.73 | 3.95 | 3.70 | 4.12 | 4.17 | 4.32 | 4.43 | 0.81 | 0.10 | <0.0001 |
| G:F | 0.151 | 0.152 | 0.163 | 0.145 | 0.162 | 0.168 | 0.170 | 0.174 | 0.74 | 0.12 | <0.0001 |
1Cattle were supplemented 0, 30, 100, or 150 ppm zinc (DM basis: Zn0, Zn30, Zn100, or Zn150, respectively) from zinc sulfate.
2Steroidal implant strategies included no steroidal implant (NoIMP) or a Component TE-200 (IMP; 200 mg trenbolone acetate + 20 mg estradiol; Elanco Animal Health, Greenfield, IN) on day 0.
3Contrast statements were formed to test for linear effects of Zn supplementation within non-steroidal implanted (NoIMP) or steroidal implanted (IMP) steers. A separate contrast statement was formed to test for differences between non-steroidal implanted steers and all steroidal implanted steers (NoIMP vs. IMP).
4Carcass adjusted performance was calculated using the average dressing percentage for all treatments: 62.25%. Adapted from Messersmith and Hansen.
The effects of zinc supplementation on the carcass characteristics of non-implanted and implanted feedlot steers are shown in Table 2. Hot carcass weight (HCW) tended to linearly increase (P = 0.09) while dressing percentage linearly increased (P = 0.01) with increasing zinc supplementation within implanted cattle. Implanted steers had greater HCW, dressing percentage, and ribeye area (REA: P ≤ 0.02) than non-implanted steers. Backfat thickness, marbling, and USDA Yield Grade were not linearly influenced by zinc supplementation or implant treatment (P ≥ 0.12).
| Item | Zn0 | Zn30 | Zn100 | Zn150 | Zn0 | Zn30 | Zn100 | Zn150 | Linear NoIMP | Linear IMP | NoIMP vs. IMP |
|---|---|---|---|---|---|---|---|---|---|---|---|
| No Implant | Implant – TE200 | Contrasts3 | |||||||||
| HCW, lb | 816 | 814 | 822 | 814 | 829 | 831 | 838 | 840 | 0.80 | 0.09 | <0.0001 |
| Dress, % | 62.2 | 62.0 | 61.9 | 62.0 | 62.3 | 62.1 | 62.4 | 63.2 | 0.62 | 0.01 | 0.02 |
| Ribeye area, in2 | 13.1 | 12.7 | 13.4 | 12.9 | 13.9 | 13.8 | 13.6 | 13.6 | 0.76 | 0.48 | 0.001 |
| 12th rib fat, in | 0.63 | 0.66 | 0.56 | 0.67 | 0.59 | 0.57 | 0.60 | 0.61 | 0.87 | 0.43 | 0.12 |
| Marbling4 | 491 | 470 | 483 | 495 | 472 | 460 | 452 | 472 | 0.70 | 0.96 | 0.17 |
| Yield Grade5 | 3.6 | 3.6 | 3.4 | 3.7 | 3.5 | 3.4 | 3.5 | 3.85 | 0.87 | 0.43 | 0.12 |
1Cattle were supplemented 0, 30, 100, or 150 ppm zinc (DM basis: Zn0, Zn30, Zn100, or Zn150, respectively) from zinc sulfate.
2Steroidal implant strategies included no steroidal implant (NoIMP) or a Component TE-200 (IMP; 200 mg trenbolone acetate + 20 mg estradiol; Elanco Animal Health, Greenfield, IN) on day 0.
3Contrast statements were formed to test for linear effects of Zn supplementation within non-steroidal implanted (NoIMP) or steroidal implanted (IMP) steers. A separate contrast statement was formed to test for differences between non-steroidal implanted steers and all steroidal implanted steers (NoIMP vs. IMP).
4Marbling scores: slight = 300, small = 400, modest = 500, moderate = 600, slightly abundant = 700, moderately abundant = 800.
5Yield grade was assigned by personnel of the commercial abattoir. Adapted from Messersmith and Hansen.
These researchers concluded that these results suggest that zinc supplementation can enhance the benefits of growth implants in beef cattle, leading to better performance, particularly during the initial weeks following steroidal implant administration. The benefits of zinc supplementation were most pronounced in implanted cattle, with minimal effects observed in non-implanted animals. They also noted that these findings have important implications for beef cattle management, indicating that current zinc recommendations may be insufficient for maximizing the growth potential of implanted cattle.
1 USDA-APHIS. 2013. The use of growth-promoting implants in U.S. Feedlots. USDA–APHIS–Veterinary Services, Fort Collins, CO.
2 Bartle, S. J., R. L. Preston, R. E. Brown, and R. J. Grant. 1992. Trenbolone acetate/estradiol combinations in feedlot steers: dose-response and implant carrier effects. J. Anim. Sci. 70:1326–1332.
3 Duckett, S. K. and S. L. Pratt. 2014. Meat Science and Muscle Biology Symposium—Anabolic implants and meat quality. J. Anim. Sci. 92:3–9.
4 National Academies of Sciences, Engineering, and Medicine. 2016. Nutrient Requirements of Beef Cattle, Eighth Revised Edition. Washington, DC: The National Academies Press.
5 Hufstedler, G. D., and L. W. Greene. 1995. Mineral and nitrogen balance in lambs implanted with zeranol. J. Anim. Sci. 73:3785–3788.
6 Huerta, M., R. L. Kincaid, J. D. Cronrath, J. Busboom, A. B. Johnson, and C. K. Swenson. 2002. Interaction of dietary zinc and growth implants on weight gain, carcass traits and zinc in tissues of growing beef steers and heifers. Anim. Feed Sci. Technol. 95:15–32.
7 Messersmith, E. M., and S. L. Hansen. 2024. Effects of increasing supplemental zinc to non-implanted and implanted finishing steers. J. Anim. Sci. 102. Available at: https://doi.org/10.1093/jas/skae365.