Survey of mortality trends over time
Recent mortality trends
Cactus Feeders’ internal data from 2001 to 2013 indicates an upward mortality trend in three weight classes of cattle: 600-weight (wt), 700-wt, and 800-wt steers (Fig. 1). Similar levels and trends are reported by USDA (2011) and Benchmark® (G Vogel 2014, personal communication, 5 June 2014). Regression analysis of Cactus Feeders’ internal data indicates that mortality is increasing at a rate of 0.10, 0.06, and 0.04% per year for 600, 700, and 800-wt steers, respectively.
Mortality by percent of animals placed for high- and low-risk steers, by weight class.
While the increasing trend is evident, careful attention must be given to variability in mortality across years and weight class of cattle. Cactus Feeders’ data indicate that mortality was observed at the highest level in 2012 (within the 13 year summary) for all three weight classes of cattle; especially evident in the 600-wt steers. This phenomenon may be explained by many factors, including: drought-related impairment in immunity, or negative nutrition, and environmental conditions at the cow–calf operation of origin. The effects of that single year had implications on the analysis of the trend data. When 2012 was removed from the regression analysis, the rate of increase for mortality across year for all three weight classes of cattle was 0.04–0.05% per year (Fig. 2). Moreover, there is no clear pattern of when mortality occurred during the feeding period across years. That is, mortality occurs throughout the feeding period and whether it occurs at the beginning, middle or end of the feeding period is variable across years and weight class of cattle.
Mortality by percent of animals placed for high- and low-risk steers, by weight class, with data for 2012 removed.
Economic impact of mortality trends
The dynamic economic impact of increasing mortality is important to understand. Analysis of closeout data (2012 through May 2014) indicates that a 1% increase in mortality has a $20.07 per head negative effect on the head marketed. Approximately 67% of the negative economic impact is accounted for in the increase in animal cost per head marketed. The remaining economic impact is reflected in the increased animal cost accrued for feed and daily charges, such as yardage and interest. The impact reflected in the increased costs per head marketed has risen approximately 98% since 2001. That is, using market prices in place in 2001, the effect of a 1% increase in mortality would increase the animal cost by $6.00 per head marketed. Using more current market prices, this same 1% increase in mortality will increase animal cost by $11.90 per head marketed. As market price increases, the economic impact of mortality is more largely explained by changes in animal cost when reported on a per-head-marketed basis. As previously discussed, mortality has increased at a rate of 0.05% per year. At this rate, this represents a 0.50% increase in mortality rate over 10 years, which would cost approximately $1.00 per-head per-year.
As death loss has increased, we should address overall productivity changes across time. Regression statistics indicate that hot carcass weight has increased 4.9 lbs per year from 2001 to 2013 (600, 700 and 800-wt steers), with initial weight and days on feed held constant at 200 days, 160 days, and 140 days for the 600, 700, and 800-wt steers, respectively.
Trend data indicate that mortality rates are increasing. Cactus Feeders’ data also show an increase in hot carcass weight across time. While the increase in mortality has increased costs for cattle marketed, overall increases in productivity have been observed. This has largely been driven by increased production of saleable carcass weight (initial weight and days on feed held constant within weight class). However, our industry is tasked with balancing both the economic benefits of productivity and the ethical considerations of animal husbandry, and therefore should strive to make improvements in both health and productivity.
The nature of BRD mortality at cactus feeders
Bovine respiratory disease (BRD) continues to have a significant economic impact during the finishing phase of feeder cattle. In 2013, input costs associated with death loss attributed to BRD is estimated to be $9.1 million, irrespective of feed costs, performance losses, and cattle realized during the feeding period. These losses accrued during the feeding period vary with risk level and placement weights, in addition to environmental conditions while on feed. Historically, from 2001 to 2011 there was a high degree of variability in our cattle in terms of risk level and arrival weight. During these years, losses attributed to BRD ranged from 65 to 70% of the total dead population. Morbidity rates of placements specific to respiratory issues varied from 6 to 8% and case fatality rates were 8–10%. In 2012, we began more consistently placing heavier cattle that had more growing time outside of the feedyard, such as in a backgrounding facility. This is evidenced by the increase in shipment numbers for 2013 (Fig. 3), and today our arrival population continues to reflect this heavier placed animal. In 2013, 1.15 million cattle were shipped and closed in our operations. Of these, 45,405 animals were identified in pen as needing therapy for respiratory disease and consequently moved to a hospital for treatment. This represents a BRD morbidity rate of 3.95% for this placement population which would be expected with this lower risk class of animals. Of these pulls, 14.7% died and were classified as respiratory deaths at necropsy. During this same time period, losses attributed to respiratory disease were 55.6% of the total death loss that occurred. Based on arrival weight and risk level, a lower than historical morbidity rate was experienced; however, case fatality rates were higher during the same time period. Also, during this time death loss trended later in the feeding period than what was experienced in years past when placement weights were lighter and BRD morbidity rates were higher.
Total number of cattle (head) shipped for harvest per year by Cactus Feeders between 2001 and 2013.
Although year-to-year comparisons of death loss are difficult to evaluate, we are experiencing an upward trend for total death loss; regardless of weight class or risk in our operations. With heavier placements today these losses tend to be distributed later in the feeding period. Over the past 25 years we have seen advancements in technologies that have provided us with a wealth of improvements in BRD prevention, control, and treatment strategies, as well as animal handling practices and laboratory diagnostics. Greater emphasis on Beef Quality Assurance has created opportunities for improvements in many areas of the production cycle. However, today we see an increase in lung lesions of varying degree at necropsy in new arrivals and a perception of reduced response to therapy in animals identified with respiratory disease. We also are experiencing death loss shifting to later in the feeding period and we struggle to identify specific areas to measure improvement in health parameters. The impact of long-standing drought also has far reaching effects. Reduced nutrition in pregnant dams potentially creates more immunocompromised animals which impacts all phases from grazing to finishing. Those animals may survive until late in the finishing phase only to succumb to new challenges, both infectious and environmental, prior to harvest. The increased number of days with high heat and dust levels in recent years also has a negative impact on convalescence from illness and the ability of cattle with longer days on feed to recover in the cooler overnight hours. The impact of these observations is difficult to analyze in the absence of appropriate controls when seeking answers for increased case fatality rates and later day mortalities in our current population.
Late day mortality
There has been a great deal of discussion and debate recently regarding what some term ‘late day mortality’. While progress in the area of BRD still suffers from challenges related to diagnosis, among other things, the state of the science is such that, in broad terms we understand enough of the etiology to know how to greatly reduce the incidence and severity of the complex and, generally speaking, have the tools to do so. It seems much of the energy around BRD discussions is, and should be, centered on understanding failures with respect to what otherwise should have been a ‘non-event’, cases where our preparatory strategies did not work.
In contrast, the study of late day mortality is at a stage where it still suffers from a lack of definition, as well as a lack of credible diagnosis, and almost certainly a lack of independence from success in the earlier stages of the feeding period. In terms of the distribution of mortality across the feeding period, the name itself compels one to compare shifts in distributions of death over time. For instance, one might consider steers fed in a feedyard for 160 days and make a simple query of which quartile of the feeding period does the mortality tend to occur, and has that distribution changed over time? A perfectly even distribution would show 25% of the total mortality occurring in each of the four quarters over time. While very informative and interesting for beginning a study of late day mortality, the approach suffers from a lack of independence from improvements in BRD mortality in the first quarter of the feeding period, for example. Improvements in one phase will be interpreted as regress in another phase.
The alternative approach of studying absolute values of late day mortality over time (instead of distribution changes) are likely also affected by successes or failures in the other stages of the feeding period, not through mathematical truism as in the distribution approach, but through complex biological and environmental relationships. Tremendous population data resources and computing power exist today for creating knowledge of both early and late day mortality, and certainly those must be used to do so. However, escaping the necessity of a control to avoid misattribution is extremely difficult. We contend that the only chance to accomplish this with utility is through the creation of the predictive model. A predictive model disciplines the scientist and brings the appropriate credibility as it displays the residual fraction of late day mortality in this case, that cannot be explained by any known X-variable.
