Page 350 - The Welfare of Cattle

CoW CoMfort daIrY housInG sYsteMs 327

be explained by the rather limited exposure of test cows to the outdoor area prior to preference
testing. There is clearly a need for much more work elucidating the myriad factors influencing cow
preferences for pasture access.
Another common leg health issue are hock lesions. The hock region is especially vulner-
able to injury because it has very little protective fatty tissue or muscle. Hock lesions can vary
in severity from mild hair loss and inflammation to severe swelling and, in extreme cases, ulcer-
ation and joint infection. Mean herd prevalence estimates of hock lesions range from 42% to 73%
(Kester et al., 2014). The relationship between hock lesions and lameness is not fully understood,
but research has found cows identified as lame in the previous month are more likely to develop
subsequent hock lesions (Lim et al., 2013). This suggests hock lesions are more often a consequence
of lameness rather than a cause. Once cows become lame they tend to lay down much longer than
normal (Ito et al., 2010), which increases the time spent in close contact with abrasive stall surfaces
that create hock lesions.
The importance of lying times is a theme found throughout the cow comfort literature.
Munksgaard et al. (2005) demonstrated cows will choose to lie down instead of feeding after being
deprived of both lying and feeding for extended periods of time (also see Metz, 1985). Cows with
restricted lying times also exhibit a greater physiological stress response than cows with an unre-
stricted ability to lie down (Munksgaard and Simonsen, 1996). Multiple investigations have moni-
tored lying/standing times to assess difference between housing systems. The results are inconsistent
with studies finding that lying times increase (Olmos et al., 2009), decrease (Roca-Fernández et al.,
2013) or are unchanged (Navarro et al., 2013).
Although a minimum daily lying time of approximately 12 hours/day is often recommended in
confinement housing systems (NFACC, 2009), studies have found grazing cattle tend to lie down
significantly less than this (Singh et al., 1993). Cows in pasture-based systems appear to have a dis-
tinct time budget paradigm where reduced lying times do not necessarily indicate obvious welfare
problems. Thus while lying times can be a useful tool for assessment purposes in some circum-
stances, caution is warranted when drawing inferences about cow welfare between different systems
based solely on lying behavior.
The close connection between lying behavior and leg health has led to a great deal of research
on the effects of specific stall design features and maintenance practices. Commonly used stall bed-
ding materials include sand, sawdust, straw, dried manure, composted materials, almond hulls and
other secondary products. Inorganic materials such as sand are generally preferred because they not
only provide excellent cushioning and traction when rising, but also are less conducive to bacterial
growth than organic alternatives (Zdanowicz et al., 2004). In an effort to minimize the costs associ-
ated with purchasing and maintaining bedding materials, some farms have installed rubber-filled
mattresses. Despite their intuitive appeal, several studies have shown that these mattresses often fail
to provide a sufficiently comfortable lying surface when used without the addition of deep bedding
(Tucker and Weary, 2004; van Gastelen et al., 2011; Barrientos et al., 2013; Chapinal et al., 2013).
One study found farms using rubber mattresses had a six fold increase in the number of cows with
swollen or ulcerated hocks (Cook et al., 2016). Farms using water-filled mattresses (aka ‘waterbeds’)
have fewer hock injuries compared to those using rubber filled mattresses. However sand-bedded
stalls and compost barns still result is fewer hock injuries than both of these mattress surfaces
(Fulwider et al., 2007).
Apart from the selection of bedding materials, it is very important that they be dry and suf-
ficiently deep to provide optimal compressibility. Several studies have shown deeper bedding leads
to longer lying times (Tucker et al., 2009; Lombard et al., 2010). To avoid concavity, routine main-
tenance is necessary to ensure bedding materials are evenly distributed across the entire lying sur-
face. Drissler et al. (2005) experimentally manipulated the evenness of bedding material and found
lying times increased linearly with bedding evenness (approximately 10 minutes of lying time was
lost for every 1-cm decrease in bedding material). The moisture content of bedding material also