Page 307 - The Welfare of Cattle

284 the WeLfare of CattLe

DISeaSeS OF DaIrY CattLe

The primary disease conditions of dairy cows are mastitis, lameness, retained fetal mem-
branes, metritis, ketosis, milk fever, and dystocia. From an animal welfare perspective, two things
are important. First, early identification of the disease condition is important to minimize the
suffering of the animal and the production loss and improve chance of recovery. Second, it is also
important to know the incidence or prevalence of a disease. If the disease exceeds a threshold
incidence or prevalence, one should determine the reasons and address causes of excess. The
dairy needs to maintain a record system that records the disease condition, the treatment protocol
for the individual animal, and means of assessing the treatment outcome. It should be apparent
that without a method of assessing treatment outcomes, we cannot know what proportion of ani-
mals return to the herd as productive animals, what proportion have relapses, and what proportion
either die or are culled from the herd. Assessing outcomes is not only an animal welfare issue but
affects the rate of culling and profitability of the dairy. This also suggests that the veterinarian
can have critical role as the herd epidemiologist in developing the ongoing means of record evalu-
ation. Prevention of disease is certainly the desired method approach to minimize animal welfare
and improve profitability.
Lameness is a common disease condition in dairy cows and can be categorized into either
those of infectious origin or metabolic origin. The two primary causes of infectious foot lame-
ness are foot rot and digital dermatitis. The primary consequences of metabolic disorders causing
metabolic acidosis are laminitis resulting in sole ulcers, white-line disease, and abscesses. In a
large Canadian study including 28,607 cows in in 156 herds (Solano, 2016), the prevalence of
digital dermatitis was in 15% of the cows and 94% of the herds. Sole ulcers and white-line disease
are a consequence of laminitis. The conditions were detected in 6% and 4% of the cows and 92%
and 93% of herds, respectively. In a Wisconsin survey of lameness in 66 high- performing herds,
the prevalence of clinical lameness was 13% and severe lameness was 2.5% (Cook, 2016). Rations
that are low in functional fiber and/or high in readily degradable carbohydrates can contribute to
ruminal acidosis and laminitis. Heat stress is also associated with laminitis. The consequences
of lameness besides being painful to the cow are reduced milk production, poorer reproductive
performance, and increased culling. Free stall design and bedding materials have a significant
interaction with the cow and risk of lameness. For cows housed in confinement barns with free
stalls, the odds of sole ulcers and white-line disease were twice that of those housed on deep-
bedded packs (Solano et al., 2016). The prevalence of lameness can be monitored by locomotion
scoring of subsets of cows by pens and/or parity.
Mastitis is the most common infectious disease of dairy cows in most herds. The prevalence
of subclinical mastitis as measured by bulk tank somatic cell count (BTSCC) in a herd affects the
quality of milk, the risk of individual cows developing clinical mastitis and subsequent use of antibi-
otics to treat clinical cases, and the risk of cows being culled or dying, and poorer reproductive per-
formance of infected cows. The herd veterinarian should be a key participant with management in
implementing an udder health program. Items to consider in prevention of udder infections include
dry cow therapy, teat sealants, pre- and post-milking teat disinfectants, routine culture of fresh cows
for Staphyloccus aureaus and mycoplasma spp., culture of clinical cases, and recommendations on
culling chronic cases. In addition, other items that might be included in an udder health program
are treatment protocols for clinical mastitis, evaluation of milking procedure, monitoring udder
health through somatic cell counts, equipment evaluation, and environmental assessment includ-
ing bedding, cow hygiene scoring, and recommendations for cow vaccination. Some authors have
suggested that nonsteroidal anti-inflammatory drugs should be included in the treatment regime for
severe clinical mastitis for the amelioration of pain (Suojala et al., 2013).