Growth promoting hormonal implant pellets coated with a polymeric, porous film promote weight gain by grazing beef heifers and steers for up to 200 days

Abstract

Two studies evaluated growth promoting effects of implant pellets (IP), each containing 3.5 mg estradiol benzoate (EB) and 25 mg trenbolone acetate (TBA), to which a polymeric, porous coating was applied. Trial 1 evaluated performance of heifers (n = 70/treatment, initial BW = 188 ± 2.2 kg) and steers (n = 70/treatment, initial BW = 194 ± 2.2 kg) implanted subcutaneously in the ear with 0 (SC), 2 (2IP), 4 (4IP), or 6 (6IP) pellets that delivered EB/TBA (mg/mg) doses of 0/0, 7/50, 14/100, and 21/150, respectively, over grazing periods of 202 d (heifers) or 203 d (steers). Animals received experimental treatments on d 0 and over the grazing period were managed as single groups by sex in a rotational grazing system. When pasture forage availability became limited, cattle were supplemented with preserved forage but not concentrate supplements. Weight gains by heifers treated with 2IP, 4IP, and 6IP were greater (P < 0.05) than SC heifers but not different from each other. Weight gains by steers treated with 2IP, 4IP, and 6IP were greater than SC steers (P < 0.05), and ADG by steers treated with 6IP was greater (P < 0.05) than steers given 2IP or 4IP. Trial 2 was a multisite grazing study performed with heifers and steers to compare ADG after treatment with one 6-pellet, coated implant delivering 21 mg EB and 150 mg TBA (6IP) to sham treated negative controls (SC) over a grazing period of at least 200 d. A completely random design was used at each site, with the goal to treat 70 cattle per site, treatment, and sex; data were pooled across sites. Heifers (n = 558, initial BW = 229 ± 16 kg) and steers (n = 555, initial BW = 235 ± 20 kg) grazed in rotational programs consistent with regional practices for an average of 202 d. When necessary, cattle were supplemented with preserved forage, but no concentrate supplements were fed. Over 202 d, ADG by heifers treated with 6IP was 11.3% greater (P = 0.0035) than SC heifers (0.64 ± 0.06 kg/d), and ADG by steers treated with 6IP was 17.2% greater (P = 0.0054) than SC steers (0.66 ± 0.08 kg/d). In neither study was there evidence that concurrent therapeutic treatments or abnormal health observations were influenced by experimental treatments. These studies demonstrated that a 6-pellet implant with a polymeric, porous coating that delivers 21 mg EB and 150 mg TBA improved ADG by grazing heifers and steers for at least 200 d compared to sham-implanted negative controls.

Effects of Synovex One Grass, Revalor-G, or Encore implants on performance of steers grazing for up to 200 days

“…Cleale et al (2012) showed that addition of the polymer coating to 8-pellet implants containing 28 mg of estradiol benzoate and 200 mg of trenbolone acetate effectively modified payout of estradiol benzoate and trenbolone acetate from approximately 120 d for traditional uncoated implants (Synovex Plus; Zoetis) to up to 200 d with coated implants containing the same doses of active ingredients (Synovex One Feedlot; Zoetis). Later, Cleale et al (2015) showed in pastured steers implanted with SOG that ADG increased over 200-d grazing periods by 20.5% compared with sham-implanted controls in one study and 16.7% in a second study, results that are similar to the present study. Data pooled from 4 studies conducted to evaluate product efficacy showed that over 107-to 116-d grazing periods, ADG by steers treated with REVG (0.94 kg/d) was 14.6% more than ADG by negative controls (0.82 kg/d; FDA, 1996), a result similar to the effect of REVG in the present study.…”

“…Finally, of 320 ENC steers observed on d 70, implants were located in 281, yielding a retention rate of 87.8%. The number of cattle with retained implants on d 70 was different across treat- Cleale et al (2015), where SOG implant retention rates in cattle treated by the same procedures as those used herein were 100 and 97.6%, respectively. Previous studies evaluating implant retention in cattle treated with estradiol-containing silicone implants have reported similar results to those reported here (Mathison and Stobbs, 1983).…”

“…Evidence of preexisting implants was not detected during treatment administration on d 0. Preparation of implant sites before treatment was as described by Selk et al (2006) and Cleale et al (2015). Cattle with clean and dry ears were implanted without cleaning.…”

“…Implant sites were observed when animals were weighed on d 70, and observations were documented. Implanted ears on each animal were palpated to document presence or absence of the implant (1 = present, 0 = absent) and whether local implant site reactions were evident (e.g., evidence of abscess); data were summarized as previously described (Cleale et al, 2015).…”

“…Estrogen-only products (Ferguson et al, 1988) are available for use in grazing steers, which are effective for 200 d (Compudose; Elanco, Indianapolis, IN) or 400 d [Encore (ENC); 43.9 mg of estradiol; Elanco]. Recently, Synovex One Grass (SOG; Zoetis, Parsippany, NJ), a combination product containing 21 mg of estradiol benzoate and 150 mg of trenbolone acetate per dose, was shown to be effective for growth promotion in pastured steers and heifers for up to 200 d (Cleale et al, 2015).…”