Читать книгу Bovine Reproduction - Группа авторов - Страница 253

Seventy percent of the lameness cases observed in beef cattle practice are associated with the hoof. Fifty percent of these cases are diagnosed with chronic laminitis, the vast majority of which are the chronic subclinical form. Acute laminitis is caused by an acute metabolic or systemic illness and is characterized by reluctance to stand, arched back, and the appearance of walking as if they were on a very hot surface (Figure 16.10).

Figure 16.10 Acute laminitis in a Hereford bull on self‐feeder.

There are no outward lesions expressed or seen on the soles of the hoof, although inflammation may be observed in the coronary band and a digital pulse may be present. Subacute laminitis doesn't usually express itself until several weeks after the insult, and the symptoms observed are sole hemorrhage and discoloration of the white line and sole tissue.

Subclinical laminitis is due to periodic upsets in normal body function. A few scenarios that can predispose to chronic laminitis include:

 Mismanagement of the young growing calf

 Bulls on gain test

 Cattle being prepped for sale

 Cattle breeds involved with progressive genetic improvement

 Cattle being fitted for show

 Dairy cows being fed for maximum milk production

The general appearance of a hoof with subclinical laminitis is one that flares out at the wall with a flattened sole. Closer examination reveals white line separation with abscessation, vertical and horizontal wall fissures, heel erosion, and subsolar ulcers [2]. Horizontal lines (known as hardship lines) may be observed in a portion or the entire hoof wall. Over time, more than one hoof can be affected. Since hoof overgrowth is the number one initiator of lameness, cattle with chronic laminitis should have regular hoof trimming to maintain proper hoof health [3]. The vascular damage that occurs during episodes of subclinical laminitis can lead to a cascade of hoof problems, discussed in the following sections [4] (Figures 16.11 and 16.12).

Figure 16.11 Severe white line disease and hoof crack as a result of chronic subclinical laminitis.

Figure 16.12 Subclinical laminitis with hardship lines present as horizontal grooves in hoof wall.