Recipient Organization
SOUTH DAKOTA STATE UNIVERSITY
PO BOX 2275A
BROOKINGS,SD 57007
Performing Department
Animal Science
Non Technical Summary
For more than 60 years, beef cattle producers have safely used various types of growth-enhancing technology (GET) to improve carcass leanness, increase average daily gain (ADG), and alter dry matter intake (DMI). Generally, the use of a GET increases ADG and only moderately affects DMI. Consequently, this enhances the rate of live weight gain relative to the amount of feed needed to achieve that gain, which is referred to as gain to feed ratio (G:F) or gain efficiency. When a producer chooses to utilize a GET, improvements in treated cattle over non-treated cattle are typically in the range of 10-30% for ADG and 5-20% for G:F ratio (Johnson and Beckett, 2015).The most common and widely used type of GET available to producers are steroidal implants with anabolic activity. It has been reported by APHIS (2013) that more than 90% of cattle entering feedlots are administered an anabolic implant at least once, and that 79.8% of steers and 98.5% of heifers weighing less than 318 kg receive 2 or more anabolic implants. There are over 30 commercially-available implants marketed in the U. S. for beef cattle production. These are classified into low, medium, or high potency implants (Johnson and Beckett, 2015) based on the differing amounts and ratios of anabolic compounds contained in the implant. The active ingredients contained in steroidal implants belong to one of three major categories of hormones: androgens (e.g. trenbolone acetate; TBA), estrogens (e.g. estradiol-17β; E2), and progestins (e.g. progesterone; P4). Once an implant is correctly administered in the back of the ear, the anabolic compound is slowly released into blood circulation from the excipient for 60 to 120 days (Mader et al. 1998). The appropriate term used to describe this is "payout". In recent years, implant technologies have improved, and now can extend the payout period to almost 200 days post-implantation.Steroidal implants with anabolic activity are critical tools for efficient U.S. beef production and the use of steroidal compounds is widely accepted by beef cattle producers. Historically, the use of implants are antagonistic to the development of economically relevant tissue depots (i.e. intramuscular fat). Implants increase frame size and delay fattening. This shift in frame size requires implanted cattle be fed to a greater final shrunk body weight (FSBW) in order to reach similar empty body fat (EBF) percentage (i.e. chemical maturity) as compared to non-implanted cattle. Implanted cattle have decreased quality grades if cattle are not harvested at similar EBF%. No other technology is available to producers that can match improvements in live or carcass-adjusted performance and hot carcass weight (HCW) achieved via implants at equal back fat (BF) thickness (Reinhardt, 2007).The optimized used of implant technologies suited to the genetic merit or plane of nutrition of the animal being fed warrants investigation moving forward. It has been demonstrated (Black et al., 2015) that genetic propensity for gain and marbling can impact the relative influence that implants can have on carcass gain and USDA Quality Grade. Pritchard et al. (2015) demonstrated that cattle grown at different ADG rates from 50-65% of FSBW and subjected to identical anabolic stimulation had different marbling score when cattle were harvested at equal BF accumulation.Multiple experiments will be conducted over several years to make production scale feedlot nutrition/feed management comparisons. The replication in these studies (5 to 10 pens/treatment, with 8 animals/pen; depending on cattle source, or 16 individually fed animals/treatment) should be sensitive enough to detect a 5-10% change in average daily gain, dry matter intake, and feed efficiency. (alpha = 0.05; beta = 0.80). These experiments should provide information to more strategically use growth enhancing technologies in beef cattle production. These data will also prove useful in the development of improved prediction equations for growth and intake in confinement feed beef cattle. This will ultimately improve feed formulation and utilization when various types of cattle and growth enhancing technologies are utilized.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
Characterize the molecular mechanisms controlling skeletal muscle tissue growth, development and composition.
Project Methods
Objective 1: Characterize the molecular mechanisms controlling skeletal muscle tissue growth, development, and composition.A series of experiments will be conducted to help better understand how altered doses (low, medium, or high potency) and types (coated or non-coated) of steroidal implants alter biological responses and payout characteristics in feedlot cattle. Biological responses of interest include animal growth performance, carcass trait responses, and sera metabolite responses following implantation. Studies have demonstrated that feedlot animals can have equal live growth performance but decreased muscling when implanted with a lower dose coated implant compared to a greater dose of steroids when subjected to an initial and re-implant program using non-coated implants in heifers (Smith et al., 2019). By having a better understanding of in-vivo responses to steroidal implants and impacts on growth performance, carcass trait, and sera metabolite responses (sera urea-N and insulin-like growth factor) I can provide insight into judicious and precise use of growth management technologies.Research trials will involve production scale feedlot management comparisons that are appropriately powered to detect a 10% difference in dry matter feed conversion. All processes to be used in these experiments are commonly used management practices in commercial feedlots. The Ruminant Nutrition Center (RNC) at SDSU is equipped with commercial scale individual cattle management facilities and pen housing (50 pens) on an open feedlot with concrete surfacing. Pens will serve as the experimental units (approximately 8 steers or heifers/pen) for all analyses, and typical sentinel animals (n= 2 animals/pen) will be subjected to further biological sampling (i.e. blood collection to harvest sera).Two hundred and forty steers (Continental × British) will be allotted to 3 treatments into 30 pens (10 pens of 8 steers/treatment) and fed for approximately120 d following implanting. Treatments will include: No implant (NI), 100 mg trenbolone acetate and 14 mg estradiol benzoate (100TE), and 200 mg trenbolone acetate and 28 mg estradiol benzoate (200TE). The cattle will be fed growing-finishing diets using ingredients common to the upper Midwest cattle feeding region. Blood will be collected (~ 10 mL from sentinel steers (n = 2 steers/ pen) during the weighing process, approximately every 28 d and harvested as sera following a 24 h clot at 4°C. All sera will be stored at -80° C and shipped on dry ice. Sera will be sent to Texas Tech University Station where a collaborator will use it as a growth medium in muscle cell cultures to evaluate the effects of increasing doses of TE on bovine satellite cell proliferation and gene expression. Sera will also be used to quantify insulin like growth factor-I via RIA and urea-N by colorimetric analysis. All data will be analyzed according to a randomized complete block design and subjected to repeated measures analyses when applicable.Another experiment will evaluate how varying types of steroidal implants (coated vs. non-coated) and dietary inclusion of corn silage in finishing diets affect animal growth performance and carcass traits. Our working hypothesis is that altered dietary substrate and implant payout might influence cattle marbling scores. Additionally, extra days on feed for the greater silage inclusion diet might alter carcass composition. The experiment will utilize 160 crossbred beef steers allotted to one of 20 pens. Treatments structure will be a 2 × 2 factorial arrangement. Factors include corn silage inclusion (DM basis) of 15% or 30% and implant type (coated or non-coated) containing 200 mg trenbolone acetate and 28 mg of estradiol benzoate. Pens will serve as the experimental units for all analyses and data will be analyzed as a two-way ANOVA, appropriate for a randomized complete block design. All steers will be tracked through the slaughter facility and carcass traits will be used to estimate body composition.