PSXIII-29 A meta-analysis on the effect of growth-promoting implants on growth performance and carcass characteristics of feedlot beef cattle.

Abstract The objective of this meta-analysis was to assess the effect of the use of growth-promoting implants on performance and carcass characteristics compared to non-implanted beef cattle. A systematic literature search was conducted using three search engines: Google Scholar, PubMed, and Web of Science. A total of 219 publications were retrieved using the following search terms: “Implant,” “Performance,” “Beef Cattle,” “Feedlot,” and “2010 to 2024”. For inclusion into the meta-analysis, studies had to have the following (standardized criteria): 1) fully peer-reviewed and published in English; 2) a control treatment with no growth-promoting implant; 3) a treatment group with growth-promoting implant; 4) performed in a feedlot feeding system and 5) published between 2010 to 2024. Based on inclusion criteria, 36 peer-reviewed publications with 77 treatment means were included in the data set. The number of replicates, means, and variances (i.e., SE, SD) were extracted for control and treatment groups. Statistical analysis was conducted using R. The effects of growth-promoting implants (treatment) in beef cattle were evaluated by examining the weighted mean difference (WMD) between control (without growth-promoting implants) for dry matter intake (DMI), final body weight (FBW), average daily gain (ADG), gain to feed ratio (GF), hot carcass weight (HCW), dressing percentage (DP), Longissimus muscle area (LMA), and liver abscess (LA). A meta-regression analysis was conducted to identify categorical covariates effects for the genetic group, sex class, days on feed, coated implant, number of implants, implant composition (1st implant), days on 1st implant, 1st implant trenbolone acetate (TBA):estradiol (E) ratio, 2nd implant TBA:E ratio, re-implant window (2nd implant), days on 2nd implant, TBA implant, E implant, implant plus β-agonist. Significance was declared at P ≤ 0.05. The use of growth-promoting implants in beef cattle increased (P ≤ 0.02) DMI by 4.2%, FBW by 5.3%, ADG by 12%, GF by 8.7%, HCW by 6.2%, DP by 0.3%, LMA by 5.3%, and LA by 7.7%. However, growth-promoting implants reduced (P < 0.01) carcass marbling score. Other variables may be associated with the increase in FBW and HCW since the heterogeneity of the results for FBW is 83.86% and HCW is 72.31%. Thus, the effects of genetic group, coated implant, implant composition, days on 1st implant, re-implant window, days on feed, and implant plus β-Agonist can be observed, several factors in conjunction with the use of the implant may contribute to this weight increase. Although there was a reduction in marbling scores, the results reported in this meta-analysis confirm that growth-promoting implants contribute significantly to improving growth performance and carcass characteristics, highlighting their positive impact on animal performance and beef cattle sustainability.