Page 244 - The Welfare of Cattle

WeLfare Issues In feedLot CattLe 221

the amount of grain in the diet over a 3–4 week period (Aschenbach et al., 2011, Penner et al., 2011).
One study found that most cattle can be rapidly adapted to high-grain diets in just a few incremen-
tal diet steps. However, the study concluded that reducing acidosis in the most susceptible cattle
ultimately means increasing the time that the transition occurs for the entire group (Bevans et al.,
2005).
Other approaches to reducing acidosis include feeding diets containing sufficient fiber (Nagaraja
and Lechtenberg, 2007), adding ionophores (agents that moderate feed consumption) (González
et al., 2009; 2012a) or buffers to the feed (i.e., sodium bicarbonate, seaweed) (Enemark, 2008).
Although all of the approaches discussed above are reported to control acidosis to some degree,
none of them have completely eliminated it.
Even though there are many anecdotal reports that cattle on low-fiber diets have been observed
consuming straw or wood chip bedding, dirt or wooden fence boards, there are no published studies
documenting what level of fiber deprivation triggers these behaviors or how important is the moti-
vation to consume fiber and ruminate. Overall few studies have focused on the welfare aspects of
feeding high-concentrate diets and therefore more work needs to done in this area.

Growth Promoting agents and Cattle Welfare

One of the main goals of the feedlot industry is to grow and fatten cattle as efficiently as pos-
sible. In North America, this has been achieved, in large part, by the use of growth promoting
agents including growth implants (Synovex-S, progesterone and estradiol benzoate and Revalor-S,
trenbolone acetate and estradiol) and β-agonist compounds (Zilpaterol, Optaflexx, or ractopamine).
Growth implants have been used in the feedlot industry for more than 40 years (commercially avail-
able in 1975), while β-agonists have only been commercially available since 2004 (Radunz, 2010).
The majority of feedlot cattle are implanted in the ear at least once and often twice which is
largely dependent upon the animal weight, sex, and product used (USDA, 2013). Implants contain
natural and synthetic hormones that alter the hormone status of the animal which increases average
daily gain (10%–16%) and improves feed efficiency (Jones et al., 2016) with reported use in 84% of
feedlot cattle (USDA, 2011; Stewart, 2013). β-Agonists are nonsteroid agents administered in the
feed in the last 28–35 days before slaughter and work by altering growth at the cellular level by redi-
recting energy to protein rather than fat synthesis, resulting in increased weight gain, ribeye area,
and total red meat yield (Lean et al., 2014). Reported use of β-agonist in US feedlot cattle was 57%
(USDA, 2011); however, the actual use today is likely much greater than indicated in the 2011 report.
The effects of implants on cattle welfare have been poorly studied although research focusing
on their production effects suggested that implanted cattle may be more susceptible to heat stress,
especially in summer months which is late in the feeding period when the cattle are also heavier
(Gaughan et al., 2005). Their use has also been implicated in triggering the onset of the buller steer
syndrome (Blackshaw et al., 1997) but this has not substantiated. Some implants have been reported
to increase mounting and aggressive behavior, (Lesmeister and Ellington, 1977; Stackhouse-Lawson
et al., 2015) which has the potential to increase animal injury. However, this was not a consistent
observation as other studies reported that implants had no effect on behavior (Baker and Gonyou,
1986; Godfrey et al., 1992).
The most recent welfare concerns regarding growth promoters have centered on β-agonist.
These concerns were prompted by increasing anecdotal reports that cattle being fed one of the most
potent β-agonist on the market (Zilmax) were arriving to some slaughter facilities with hoof (slough-
ing) and lameness issues and were slow and difficult to move (Thomson et al., 2015). Although the
exact cause could not be substantiated, some slaughter facilities and industry stake holders refused
to accept cattle fed the product and, in 2013 it was removed from the market (Centner et al., 2014).
Some research has reported negative welfare outcomes from feeding β-agonist such as significantly
increased odds of death (Loneragan et al., 2014); increased lateral lying and aggressive behavior