Page 352 - The Welfare of Cattle

CoW CoMfort daIrY housInG sYsteMs 329

Cleanliness and hygiene scores are tools commonly used in mastitis prevention programs (Shook
et al., 2017). A study of 144 Dutch dairy farms found udder cleanliness scores were positively cor-
related with cow somatic cell count (SCC; Dohmen et al., 2010). Another study involving 3,554
evaluations from 545 animals on two Brazilian dairies, showed cows categorized as “very clean”
consistently had the lowest somatic cell counts, while dirtier cows had the highest scores (Sant’Anna
and Paranhos da Costa, 2011).
Exposure to pasture impacts cleanliness scores and subsequent mastitis risk. A study involving
more than 1,000 loose-housed cows found pasture access was associated with better cow clean-
liness scores (Nielsen et al., 2011). A longitudinal study of dairy cows in the United Kingdom
assessed cleanliness scores and found cows tended to be dirtier during times of the year when
they were continuously housed indoors compared to when they had pasture access (Ellis et al.,
2007). Interestingly, this study also found a correlation between herd cleanliness score and bulk
tank somatic cell count (BTSCC), but failed to detect any direct link with clinical mastitis rate.
Other studies have found pasture is associated with an overall reduction in the risk of clinical
mastitis (Barkema et al., 1999). One multiyear study comparing dairy cows in both confinement and
pasture systems found confinement housed animals experienced 1.8 times more clinical mastitis
and eight times the culling rate for mastitis compared to cows on pasture (Washburn et al., 2002).
Other research has failed to detect significant SSC differences between pasture-based and continu-
ously housed systems (Arnott et al., 2017).
The use of sand bedding is associated with lower BTSCC, whereas the use of composted manure
is associated with higher BTSCC (Wenz et al., 2007). Lower herd SCCs have also been associated
with the use of free stalls (Dufour et al., 2011); however, a study of more than 100 Canadian dairy
farms failed to detect any differences in the incidence rate of mastitis between tie stalls, free stalls,
and pasture systems (Olde Riekerink et al., 2008). These somewhat inconsistent results may be
attributable to other unmeasured differences and the sheer complexity of mastitis infections. Future
research should consider the interactions between bedding type and other management factors (e.g.,
bedding frequency, depth, dry matter, lying time, and stall design) as herd level associations likely
obscure important details about the pathogenesis of mastitis.

StOCKING DeNSItY, GrOUPING StrateGY, aND FeeDING BehaVIOr

Beyond the constraints imposed by the physical environment, management factors such as group
size, stability, and composition can also impact cow comfort. Within the dairy science literature,
there have been a number of studies exploring the impact of stocking density on different indices
of cow comfort.
An early survey of free stall barns failed to find milk production differences across a wide
range of stocking densities ranging from under capacity to >30% overcrowded (Bewley et al., 2001).
However, another study involving 47 herds fed identical diets found stall availability and mainte-
nance explained 38% of the variation in milk production (Bach et al., 2008). Subsequent inves-
tigations have identified a number of other disadvantages associated with elevated stall-stocking
density including: decreased lying times (Telezhenko et al., 2012; Charlton et al., 2014), increased
prevalence of severe lameness (King et al., 2016), decreased conception rates (Schefers et al., 2010),
and decreased feeding times, along with increased aggressive interactions at the feed bunk (Huzzey
et al., 2006). With respect to lying times, reducing the stall-stocking rate from 150% to 100%
increased mean lying time by 1.7 hours/day (Fregonesi et al., 2007).
Despite the obvious impact of overstocking, agreement on the level at which the negative impacts
occurs remains somewhat elusive. With respect to milk production, it appears overcrowding may
need to be relatively severe before production is compromised. For example, negative impacts on
lying and ruminating time were not appreciated at a stall stocking density of 113%, but were noted