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# Journal of Animal Science - Article

1. Vol. 87 No. 10, p. 3418-3426
OPEN ACCESS

Published: December 5, 2014

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doi:10.2527/jas.2009-1778

# Analysis of modern technologies commonly used in beef cattle production: Conventional beef production versus nonconventional production using meta-analysis

1. B. W. Wileman*,
2. D. U. Thomson* 1 ,
3. C. D. Reinhardt and
4. D. G. Renter*
1. College of Veterinary Medicine, and
College of Animal Sciences and Industry, Kansas State University, Manhattan 66506

## Abstract

Conventional feeding systems use pharmaceutical products not allowed in natural or organic systems for finishing cattle. This review of data compares the performance effects (ADG, G:F, DMI) of technologies used in conventional feeding programs that are prohibited in organic programs, natural programs, or both. The technologies evaluated were steroid implants, monensin, tylosin, endectocides, and metaphylaxis with any antimicrobial. For inclusion in this analysis, studies were conducted in North America, reported randomization to treatment group, used beef cattle, contained an untreated control group, and were sourced from peer-reviewed journals. Forest plots were used to examine the data visually for trends toward a uniform effect of the technology on the outcomes of interest (ADG, DMI, G:F). Technologies that displayed a uniform response on the forest plot compared with negative controls were then analyzed using mixed models. Examination of forest plots for endectocides, steroid implants, monensin, and metaphylaxis technologies appeared to show performance advantages for treated cattle relative to cattle in negative control groups. An insufficient number of studies met the inclusion criteria to conduct meta-analyses comparing endectocides, monensin, or tylosin with negative controls. Average daily gain in feeder cattle given metaphylaxis on arrival was 0.11 kg/d (P < 0.01) greater relative to cattle that did not receive metaphylaxis on arrival. Implanting heifers increased ADG by 0.08 kg/d compared with nonimplanted controls (P = 0.09). Implants had no effect on G:F (P = 0.14) in heifers or on DMI (P = 0.44) relative to nonimplanted control heifers. Implanting steers was associated with greater ADG, by 0.25 kg/d (P < 0.01), and DMI, by 0.53 kg/d (P < 0.01), relative to nonimplanted control steers. Implants also improved G:F in steers relative to nonimplanted steers, by 0.02 (0.17 vs. 0.15; implanted vs. controls, P < 0.01; n = 21 studies). When average estimated differences in ADG and G:F for implanted and nonimplanted steers were incorporated into a breakeven model, implanted steers had a $77/animal lower cost of production than nonimplanted steers and a$349/animal lower cost of production than organically raised steers. These data illustrate the importance of capturing premiums when operating natural and organic production systems to maintain economic viability.

### INTRODUCTION

There is an increasing focus on organic and natural beef production in the United States. Conventional feeding systems use pharmaceutical products not allowed in organic systems for finishing cattle and do not use certified organic feedstuffs as defined under the National Organic Program (2008). The recent USDA regulations for natural beef production prohibit the use of growth-promoting hormones and animals that have received antimicrobials. However, the new rule does allow the use of ionophores for the control of coccidiosis (USDA, AMS, 2009). Until recently, there has been no standard definition of natural beef production, which has led to inconsistencies among natural beef production systems. There is very limited research comparing an entire beef cattle production system with pharmaceutical technologies with one that excludes those technologies (Fernandez and Woodward, 1999; Sawyer et al., 2003; Berthiaume et al., 2006), thus limiting the ability to predict the performance differences accurately between cattle in the different systems. Unlike a review article, a meta-analysis provides a method of examining the existing literature critically and in a quantitative manor, accounting for within- and between-trial variance, to provide an overall estimate of effect of a given question(s) based on existing data. The aim of this study was to evaluate the performance effects (ADG, DMI, and G:F) and health effects (morbidity and mortality) of pharmaceutical technologies used in feedlot cattle that may be routinely excluded from nonconventional production systems. This report uses the techniques of forest plot analysis and meta-analysis to evaluate the technologies of steroid implants, monensin and tylosin (Elanco Animal Health, Greenfield, IN), endectocides, and metaphylaxis with any antimicrobial on arrival and their effects on the performance and health of feedlot cattle. In addition, liver abscess risks of cattle receiving tylosin vs. cattle not receiving tylosin were examined.

## MATERIALS AND METHODS

Because this report only involved the use of previously published literature, there were no animals used in this research.

### Data Gathering

The question was, “What is the difference in ADG, G:F, DMI, morbidity, mortality, and liver abscess risks in feedlot cattle with and without pharmaceutical technologies in North America?” Manuscripts were identified through the PubMed and Commonwealth Agricultural Bureau electronic databases from February 2008 through April 2008. A variety of search terms were used to identify articles that possibly contained relevant information about the review questions (Table 1). Each search contained at least one search term from each category. After retrieving the citations, each title and abstract was read by the first author and was retained for further evaluation if it mentioned at least one of the treatments and at least one of the outcomes of interest in beef cattle. Further, the Intervet Schering Plough Animal Health Database (Kenilworth, NJ) and the Texas Tech University North American TBA Implant Database (Texas Tech University Implant Database, 1999) were used to identify studies utilizing steroid implants. The information contained in the database is searchable. The manuscripts and technical bulletins from which the data were sourced are linked from the site. All articles were cross-referenced with abstracts obtained through PubMed and Commonwealth Agricultural Bureau database searches, and technical bulletins from implant database were included as well. These manuscripts and technical bulletins were assessed using the same inclusion criteria, except for being from peer-reviewed sources. Only data from studies using a single implant treatment (i.e., no reimplant) with a contemporary nonimplanted control group were considered relevant. The implant data were further subgrouped into implant studies using heifers and studies using steers to attempt to mitigate the amount of variability in the data sets.

After identifying relevant studies based on the title and abstract, the complete manuscript was obtained and critically evaluated. Studies were retained for further consideration only if the study was conducted in North America, used randomization for allocation to treatment group, used beef breed animals, and contained an untreated control group. Manuscripts that did not meet all the above criteria were excluded from further consideration. Data were then extracted from the remaining studies. Data were extracted by recording the point estimates for ADG, DMI, G:F, mortality, morbidity, the presence of liver abscess and corresponding SE for each treatment group, description of the experimental unit, number of experimental units, and sex of cattle for each of the manuscripts.

For studies that reported results for different dose concentrations (e.g., monensin at 100, 200, and 300 mg/animal) the average treatment effect was calculated via a calculated mean of the treatment responses from the data at the individual dose concentrations. This data extraction approach was required for 5 studies in which authors were not able to separate out the information and report it separately. The measure for SE of the treatment effects in these studies was a pooled SE, as reported in the manuscript. When studies reported a pooled SE, this was converted to an SD by multiplying the pooled SE of the difference in sample means by the square root of the number of experimental units. The number of experimental units depended on what was defined as the experimental unit, the animal or the pen (i.e., for a 2-arm parallel comparison with 100 animals in 10 pens/arm and treatment allocated at the pen level, then n = 20). The SD was then squared to obtain the variance, which was used in the meta-analysis.

### Data Analysis

Forest plots using the R-statistical package and the rmeta and meta packages (R Development Core Team, 2008) were used to visually assess whether the effect of the technology on the outcomes of interest (ADG, DMI, G:F) was uniform across studies. For this graphic approach, the production outcome and standard deviations were used to calculate the difference between groups, and these data were used for the forest plot. In a forest plot, each study is listed individually on the left-hand side of the graph. The horizontal line listed next to each study represents a 95% confidence interval (CI) for the difference between groups for continuous outcomes. The size of the shaded box in the middle of the horizontal line represents the relative weight of a study compared with the other studies. The weight is a reflection of the number of experimental units involved in the study (i.e., the greater the number of replicates, the greater the weight). All the studies are then oriented in relation to the large vertical line listed as the zero line or no-effect line. This line represents a situation in which the difference between the 2 treatments equals zero. Studies to the right of the null value indicate a positive value and studies to the left have a negative value. Technologies were considered by the first author to be uniform when 50% of the point estimates (boxes) on the forest plot were to one side of the null effect line.

For the continuous outcomes ADG, DMI and G:F, technologies considered to display a uniform response compared with negative controls were analyzed using general linear mixed models of the MIXED procedure (SAS Inst. Inc., Cary, NC). In brief, each model of continuous outcome variables (ADG, DMI, G:F) contained 1 fixed effect (steroid implants, monensin, tylosin, endectocides, metaphylaxis), a random intercept effect for each study, and a repeated effect to incorporate the within-study variance for each study (St-Pierre, 2001; van Houwelingen, 2002). To define the covariance parameter for the between-study variance (range: 0.01 to 1.0 by 0.01), values for the within-study variance for each study (extracted from the literature) were used to create the profile likelihood function and resultant 95% CI for the between-study variance (van Houwelingen, 2002). The only change from the form described by van Houwelingen (2002) was the addition of the least squares means command to generate model-adjusted means and SE for fixed effects and establish a single overall treatment effect for each technology that showed a statistically significant difference (α <0.10). The model-adjusted means and SE for ADG, DMI, and G:F, when statistically significant, were used to derive a 95% CI for the summary effect and were incorporated into a standardized feedlot breakeven model.

The metaphylaxis morbidity and mortality data and the tylosin liver abscess incidence data were analyzed with generalized linear mixed models with a logit link and binomial distribution using the GLIMMIX procedure of SAS. The outcome variables were modeled in an events/trial format, where the denominator represented the total number of cattle within a group and the numerator included only those with the outcome of interest (morbidity, mortality, liver abscess). A repeated statement was used to account for the multiple observations within studies, and a random intercept term was used to account for the potential correlations among groups within studies. Metaphylaxis was included in the model statement as a fixed effect, and when significant, model adjusted estimates were transformed from the logit form to generate the estimated probability of treatment or death of an animal if receiving metaphylaxis, or having liver abscesses if consuming tylosin, respectively. Therefore, the estimated probability represents a cumulative incidence or risk of these adverse health events occurring at some point during each trial.

### Breakeven Model

A standardized feedlot breakeven model commonly used by feedlot consultants and managers to assess the economics of feeding a pen of cattle with user-defined inputs was used (Thomson, 2008). The economic model assumptions are listed in Table 2. Based on an average of the ADG and G:F reported in Berthiaume et al. (2006), Fernandez and Woodward (1999), and Sawyer et al. (2003), we used an ADG of 1.30 kg/d and a G:F of 0.14 to predict the breakeven values for naturally raised calves. The model was then used to simulate implanting the natural calf, and the estimated differences in ADG and G:F from the meta-analysis were used to estimate a breakeven value. Finally, the model was used to predict feeding the natural calf an organic diet. For the organic breakeven value, the days on feed were increased by 20 d (Fernandez and Woodward, 1999) and the organic feed costs were multiplied by 1.5 (USDA, 2003) to simulate the feedlot performance and feed cost differences of organic cattle. A sensitivity analysis was performed for organic feed prices, ranging from 1.25 to 1.75 of conventional feed prices.

## RESULTS

A total of 14,311 citations were identified by the initial electronic search. After examining the titles and abstracts for possible relevance and removing duplicate citations, 140 manuscripts were retrieved for quality assessment and data extraction. After quality assessment and application of the inclusion criteria, 91 treatment to control comparisons were identified from 51 manuscripts (Table 3). The 3 most frequent reasons studies were excluded were failure to include an untreated control group, failure to report variation of the outcome either as an SD or SE, and failure to use randomization to allocate animals to treatment groups.

Based on visual assessment of the forest plots, the use of endectocides (figure not shown), steroid implants (Figures 1 and 2), monensin (figure not shown), and metaphylaxis (Figure 3) showed a performance advantage for treated cattle relative to cattle in the negative control groups (i.e., more than 50% of point estimates to the right of the null). Tylosin studies did not show a consistent advantage in treated cattle relative to control cattle with respect to ADG, G:F, and DMI. An insufficient number of studies met the inclusion criteria to conduct a meta-analysis comparing endectocides, monensin, or tylosin. Therefore, a summary effect measure was calculated only for the metaphylaxis and implant data sets.

### Meta-analysis and Breakeven

Average daily gain in feeder cattle receiving metaphylaxis and a variety of antibiotics used on arrival was 0.11 kg/d (95% CI = 0.10 to 0.13, P < 0.01) relative to cattle that did not receive metaphylaxis on arrival (Table 4). The use of implants in heifers was associated with increased ADG by 0.08 kg/d compared with nonimplanted controls (95% CI = 0.01 to 0.15, P = 0.09). The use of implants in heifers was not associated with differences in G:F (P = 0.14) or DMI (P = 0.44). The use of implants in steers was associated with 0.25 kg/d greater ADG (95% CI = 0.23 to 0.27, P < 0.01) and 0.53 kg/d greater DMI (95% CI = 0.45 to 0.61, P < 0.01) relative to nonimplanted control steers. The use of implants was also associated with increased G:F in steers relative to nonimplanted steers, by 0.02 (0.17 vs. 0.15; implanted vs. control, 95% CI = 0.018 to 0.022, P < 0.01).

Key Words