Cattle producers don’t usually have to worry too much about lameness issues in the pre-breeding beef and dairy heifer, but there are some management and environmental influences that affect a heifer’s future soundness and productivity in the herd. Lameness in pre-breeding age heifers tends not to receive much attention primarily because these animals are not convenient or easy to examine. “There is a tendency to assume that most of the lameness that occurs in these animals is due to injuries,” says Jan Shearer, DVM, MS, Iowa State University. “When the problem is of short duration and the animal does not exhibit evidence of swelling or other obvious lesions, this is likely the case. However, when the problem persists and progressively worsens, an investigation of the possible cause or causes is in order.”
Udder development at calving naturally changes rear leg posture and changes weight bearing dynamics slightly from the non-lactating to the lactating state. “Conformation and healthy development of sound foot and leg structure are absolutely critical for the future success of any bovine, but particularly so if they are to be housed primarily on concrete,” Shearer says. “In our present-day large scale operations, cows must be able to walk significant distances on a daily basis whether it’s to and from the milking parlor or to the feedbunk and back. We also know that they must be able to establish some degree of dominance in order to compete within their respective groups and they must be able to respond to normal instincts and behaviors such as estrus which requires them to mount or stand to be mounted by herdmates or a bull.”
Nutrition and foot health
Nutrition plays a large role in structural development of the claw, skeletal structures and sound foot health. Trace minerals such as copper and zinc have important roles in the formation of claw horn where they serve in critical metabolic pathways that contribute to keratin formation (an important structural component of horn cells).
“The formation of keratin within the intracellular matrix of horn cells increases their physical strength, thus making them more resistant to mechanical forces when they reach the exterior of the claw horn capsule,” Shearer explains. “Biotin has similar functions and is essential to the proper development of the intracellular cementing substance analogous to mortar between bricks in a wall.”
Concrete can lead to problems
On most large dairies, some amount of concrete is unavoidable. Confinement facilities, where cows are required to be on hard surfaces for extended periods, tend to increase rates of claw horn growth. This can lead to abnormalities in weight bearing, which Shearer says can and should be corrected by trimming. Feeding at mangers or feedbunks also increases problems with an acquired form of corkscrew claw that tends to affect the inner claw of front feet. This may also require correction during the trimming session when it becomes severe. Confinement of animals also tends to increase exposure of feet and legs to manure slurry and moisture conditions which are believed to increase problems with the infectious foot skin conditions such as digital dermatitis, interdigital dermatitis and heel erosion and foot rot.
Concrete has contrasting effects on claw horn. “In facilities that restrict exercise of animals, wear rates are low and overgrowth is acceler-ated by irritation of the corium,” Shearer says. “Similar to the formation of calluses on the soles of a person’s foot where they bear weight, the cow accelerates horn (horn is modified skin) formation on the claw that bears the most weight.” He notes that in cattle, the work of Toussaint Raven and others indicates that this is the outer claw of the rear foot and the inner claw of the front foot. Thus, overgrowth of the outer claw of the rear foot and inner claw of the front foot are most severe in these conditions.
On the other hand, when the flooring surface is abrasive or if the animals have long distances to walk, the rate of claw horn wear may outstrip the growth rate. When this happens animals may become thin-soled and severely lame with lesions occurring primarily in the outer claw of the rear foot and the inner claw of the front foot. Thin-soled heifers or cows become very lame because the sole is unable to support the weight of their body without damage to the underlying corium.
Thin soles may also progress to a break in the sole near the outer wall at the toe known as a thin-sole-toe-ulcer1. When this occurs it is not uncommon for these to progress to a toe abscess. Herds suffering lameness where most of the lesions are occurring in the toe should investigate the possibilities of this condition.
Wet and muddy conditions are conducive to infectious disorders of the foot skin. They also keep claw horn softer which increases rate of wear on abrasive surfaces. Moisture and manure slurry conditions create the conditions for infectious disorders of the foot skin (digital dermatitis, interdigital dermatitis, heel horn erosion and foot rot). “More and more data are suggesting that hard flooring surfaces coupled with poor stall design that limits resting behavior are prime causes of lameness,” Shearer states. “There is good evidence that lameness in cattle has a close association with the mechanical stresses imposed by hard floors. A comfortable stall or a lot that offers relief from these stresses is critical to optimal foot health, particularly in heifers around the time of parturition.”
Genetics and lameness
In the past, cattle producers have opted to place greater emphasis on selection for factors such as milk production or fecundity. “Pure-bred cattle breeders may have a greater concern about potential lameness conditions, but have very little specific information on how to avoid these problems since some conditions are so widespread and also complicated by other etiologic factors (i.e. corkscrew claw),” Shearer says. “When producers or breeders tend to emphasize longevity in their breeding programs they pay closer attention to conformation of feet and legs.”
As indicated above, some of the congenital defects observed in cattle have more than heritability as an underlying cause. Research suggests that the heritability of sound foot and leg structure is low, Shearer notes. “It takes a long time to correct conformational issues by improvement in breeding programs even when there is reliable information on bulls. And, while we tend to place a great deal of emphasis on bull selection, if the cow has lousy foot and leg structure, progress toward improvement will be slow. It is important to consider her contribution to the problem.”
Post-legged animals tend to have reduced longevity because many are at greater risk of degenerative joint disease (DJD) because of their conformation. “This is most surely a welfare problem and is not uncommon with certain club calf type bulls that produce great club calves, but animals that don’t fit most commercial cow-calf operations because they are prone to DJD and other lameness related problems,” Shearer says.
Spastic paresis is a neuromuscular disorder that sporadically occurs in beef, dairy and crossbred cattle. The disease is characterized by hyperextension of the limb followed by a spastic contraction of the gastrocnemius muscle. The disease is usually detected within a few months of the calf’s life and it gradually worsens over time. One or both of the rear legs may be affected. “There are methods to correct this condition surgically, but it is highly questionable if such procedures would be practical, and in addition, one should be cognizant of the hereditary implications,” Shearer says.
He adds that because of its sporadic occurrence, it is difficult to avoid reproducing some of these by searching the backgrounds of bulls or cows. In most cases, this information isn’t known or if known may not be recorded. “One reference suggests that even though the disease is known to be inherited, it shouldn’t limit bulls with high genetic merit because many believe that other environmental factors are likely to influence its occurrence,” Shearer says, “but this is indeed a controversial opinion.”
Shearer says there are a number of other congenital conditions that he would place under the heading of non-specific joint rigidity that are likely congenital defects with multi-factorial etiology.
1van Amstel and Shearer, The Bovine Practitioner, 2008, Vol. 42, No. 2, p. 189