Finishing Cattle in All-Natural and Conventional Production Systems

Beef cattle producers in the North America have a variety of production and marketing options and must choose the best production system for their situation. This review describes considerations involved in choosing between feeding cattle conventionally versus feeding them in programs that prohibit the use of certain technologies. Data from peer-reviewed journals, extension publications, nutritional consultants, governmental organizations, and feed companies were used to construct this review. Most cattle in North America are fed in conventional production systems. Conventional beef production systems typically use steroidal implants, ionophores, and beta-adrenergic agonists to improve animal productivity;as well as feed grade and injectable antimicrobials to control, treat or prevent disease and improve animal health. These technologies have been shown to lower the cost of production, allowing for beef to be competitive in the global protein market. Some consumers have expressed a preference for beef produced without these technologies. These “All-natural” (AN) cattle may bring a premium price in the market. The economic impact of differing productions systems can be described in relation to 1) cost of production, 2) operating costs of the feedlot, 3) price paid for feeder calves, and 4) price received for fed cattle. Conventional production provides the most favorable outcome for factors 1, 2, and 3, while AN production provides the most favorable outcome for item 4. There are also industry wide and societal aspects related to differing beef production systems related to health and safety of beef, land use, and cost of production allowing for a greater share of the global protein market. Technologies used in conventional production are critical tools to North American beef production. Differences in efficiencies between each type of non-conventional production systems must be re-captured in added premiums when cattle are marketed and sold. Premiums for AN cattle are enticing, but the true differences in the cost of production between the AN and conventional cattle must be evaluated in order for a producer to make the correct decision for their operation.

Effect of Direct-Fed Microbial Supplementation on Pathogenic <i>Escherichia coli</i>Fecal Shedding, Live Performance, and Carcass Characteristics in Feedlot Steers

Three experiments were conducted to evaluate direct-fed microbial (DFM) supplementation on live performance, carcass characteristics, and fecal shedding of E. coli in feedlot steers. In Exp. 1, 400 steers (BW = 348 kg) were assigned to treatments: CON = lactose carrier only, BOV = P. freudenreichii (NP24) + L. acidophilus (NP51), BOVD = P. freudenreichii (NP24) + L. acidophilus (NP51), and COMB = BOV fed for the first 101 d on feed, followed by BOVD for the final 28 d prior to harvest. In Exp. 2 (n = 1800;BW = 354 kg) and Exp. 3 (n = 112;BW = 397 kg), steers were utilized in a randomized complete block design and assigned to DFM treatments using low dose and high dose, respectively. Fecal samples were collected prior to harvest and analyzed for E. coli serogroups. In Exp. 1, DFM reduced (P < 0.01) the concentration of E. coli O157. Prevalence of O157 was reduced by BOVD supplementation in Exp. 2 and 3 (P < 0.01 and P = 0.08, respectively), and concentration of E. coli O157 in positive samples was reduced in both experiments where enumeration was performed (P ≤ 0.02). Weighted mean differences across the three experiments were equal to a 33% reduction in the prevalence of E. coli O157:H7 in BOVD treated cattle. A significant reduction in prevalence of O26, O45, O103, and O121 was observed in Exp. 2 (P ≤ 0.03). These results indicate that high levels of L. acidophilus (NP51) may represent an effective pre-harvest food safety intervention to reduce fecal shedding of several E. coli serogroups.

Body Weight and Steroidal Implants Impact Animal Growth Performance, Sera Metabolites, and Pulmonary Arterial Pressure in Feedlot Cattle

The study objective was to evaluate steer growth performance, sera metabolite responses, carcass characteristics, and pulmonary arterial pressure as affected by body weight at time of implantation and steroidal implant administration. Crossbred steers (n = 20) were used in a 2 × 2 factorial arrangement of treatments in a completely randomized design experiment, Factors included: body weight: light (L), or heavy (H) and implant: Non-implanted (NoIMP), or Implanted (IMP) with steer serving as the experimental unit for all analyses. Initial weights for L and H steers were 398 ± 27.6 and 547 ± 25.2 kg, respectively. Implanted steers received a terminal implant (200 mg trenbolone acetate and 20 mg estradiol-17β;Revalor-200;Merck Animal Health, Madison, NJ) on d 0. Cattle within treatments were group housed in common pens (n = 5 steers/pen). Bodyweight, blood samples, and pulmonary arterial pressure were collected on d 0, 14, 35, 70 and 104. Cattle were fed a common diet once daily to provide ad libitum access to feed. The finishing diet contained (DM basis) 13.3% CP, 2.13 Mcal/kg NEm, and 1.45 Mcal/kg NEg. Growth performance (body weight and ADG) and carcass traits were analyzed using the MIXED procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC). Sera metabolites were analyzed as repeated measures over time, with day as the repeated measure. For all analyses, α level < 0.05 determined significance. Heavy steers consumed 2.2 kg more per head of DM daily than L cattle and IMP steers consumed 1.0 kg more DM daily than NoIMP steers. Cumulative ADG did not differ between the L and H steers (1.41 vs. 1.52 ± 0.060 kg;P = 0.20). Implanting increased (P < 0.01) ADG by 39% (1.22 vs. 1.70 ± 0.060 kg). No differences (P > 0.05) in ADG were observed in NoIMP vs. IMP cattle beyond d 70 (1.21 vs. 1.01 ± 0.16 kg;P = 0.38). Sera urea-N concentrations were decreased (P < 0.01) in L cattle subjected to IMP during the study and tended to increase over time for the other treatments. Ribfat, HCW, LM, marbling score, calculated YG, and estimated EBF were greater (P ≤ 0.05) in H compared to L. Steers from IMP had heavier HCW (P < 0.01) but decreased marbling scores (P = 0.05) compared to NoIMP. Mean pulmonary arterial pressure was greater (P < 0.01) for H compared to L steers which may predispose heavier cattle to right-sided heart failure. The steroid implant had no effect on pulmonary arterial pressure (P > 0.49). The study reaffirms the effects of implanting on animal growth performance and carcass characteristics in cattle. In addition, elevated BW leads to increased pulmonary arterial pressures which may increase the risk of right-sided heart failure.