Ultrasonographical examination of bovine claws through the sole horn on weight-bearing claws.

Claw horn disruptions in the bovine claw are believed to be a consequence of pressure on the sole corium from the third phalanx, which may be caused by a weakening of the suspensory apparatus in the claw. We aimed to develop an ultrasonographic method that would make it possible to measure the thickness of the soft tissue between the third phalanx and the sole horn on a weight-bearing claw. A device was developed to record the sole horn and soft tissue thickness indirectly through a polyethylene plate, and 52 feet from slaughtered cows were examined using ultrasonography, both directly and indirectly. Soft tissue and sole horn thickness measurements in the apex and the plantar part of the sole were compared with anatomical measurements of transected claws. To assess the method on weight-bearing versus non-weight-bearing claws, we examined the hind claws of 10 live cattle without transection. We found a weak correlation between the soft tissue thickness measured by ultrasound and anatomical measurements. A strong correlation was observed between the direct ultrasound approach and the developed indirect method. There was a considerable difference between weight-bearing and non-weight-bearing claws, signifying a weak or nonexistent correlation. However, this part of the study was only done on 10 live cows and the results should be interpreted with caution. We concluded that it would be possible to measure the soft tissue using an indirect ultrasound approach on a weight-bearing-claw standing on a polyethylene plate. The major difference between the results of weight-bearing versus non-weight-bearing claws suggests that future studies of the suspensory apparatus could focus on weight-bearing claws.

Technical note: Effects of frozen storage on the mechanical properties of the suspensory tissue in the bovine claw.

It is proposed that a softening of the suspensory tissue in the claw is involved in the development of lameness and claw lesions in cattle. A relatively small amount of research has been carried out to verify this theory. Research in this area would be simplified if mechanical testing of the suspensory tissue could be performed on frozen and stored specimens. The current study tested whether freezing of the specimens changes the suspensory tissues' mechanical properties. Limbs from 3 freshly slaughtered Danish Holstein dairy cows and 6 nonpregnant Angus heifers, without clinical signs of lameness, were allocated to 1 of 2 treatments (frozen or nonfrozen) in such a way that each cow was represented in each treatment group with a frozen limb and a corresponding nonfrozen limb (i.e., frozen left front, fresh right front, and so on). The frozen limbs were kept at -18°C for a week before processing and the nonfrozen limbs were processed within 2h of slaughter. Two samples measuring 8 × 8 mm were cut from the abaxial side of each claw in such a way that the sample included the horn of the abaxial wall, pedal bone, and the interposed corium. The samples were kept on ice until being mounted in a large deformation rheometer with an extension testing frame, fixed by the horn and the pedal bone, and loaded to failure. During deformation force and displacement data were recorded, from which corresponding stress and strain were calculated. Young's modulus (a measure of tissue elasticity or stiffness) and a measure of physiological support (PS; force needed to displace the sample 1mm) were calculated from the data. The response variables, Young's modulus and PS, were analyzed separately by a mixed model. The explanatory variables were treatment (frozen or nonfrozen), limb (front or back), claw (medial or lateral), position of the sample (dorsal or palmar-plantar), and group (Angus or Holstein). Interactions between group and treatment and between limb, claw, and sample position were included in the model. Cow identity was included as a random effect. Model reduction was performed by stepwise backward elimination, until all remaining terms were significant at the 5% level or less. Freezing had no effect on the elasticity of the suspensory apparatus or on PS. However, PS was affected by limb (hind legs had higher PS values than front) and the position of the sample (palmar-plantar samples had higher PS values than dorsal). The Angus group had higher PS values than the Holstein group, but the groups differed in age, parity, body weight, lactation, housing, and management, as well as in breed; therefore, further studies are needed to investigate these effects. The results indicate that mechanical testing of bovine claw suspensory tissue can be performed on specimens that have been frozen, thus aiding research in the mechanical aspect of bovine lameness and claw lesions.

Biomechanics and histology of bovine claw suspensory tissue in early acute laminitis.

Weakening of the suspensory tissue supporting the pedal bone is the central issue in the theory of acute bovine laminitis, but this aspect has never been tested. The objective of this study was to investigate the effect of laminitis on the suspensory tissue. The hypothesis was that clinical and histological signs of acute laminitis are associated with decreased strength of the suspensory tissue of the bovine claw. Nonpregnant dairy heifers (n=10) received oral oligofructose overload (17 g/kg of body weight) and were killed 24 (n=4) and 72h (n=6) after overload. Control heifers (n=6) received tap water and were killed at 72 or 96h. Clinical, orthopedic, and histological examinations were carried out to confirm the occurrence of laminitis. After euthanasia, 2 adjacent tissue samples including the horn wall, lamellar layer, dermis, and pedal bone were cut from the dorso-abaxial aspect of each claw. Tissue samples were kept on ice until mounted on a mechanical testing frame, fixed by horn and bone, and loaded to failure. A stress displacement curve was generated and measurements of physiological support (force needed to displace 1mm beyond first resistance) and maximal support (force needed to break the tissue) were recorded. Heifers treated with oligofructose developed clinical signs consistent with ruminal and systemic acidosis after treatment as well as acute laminitis, characterized by weight shifting (35% of observations vs. 6% in controls), moderate lameness (100 vs. 17%, score of 3 out of 5 at 72h), and reaction to hoof testing (30 and 50% at 48 and 72h, respectively, vs. 0% in controls). Histological examination of claws from heifers killed 72h after overload showed changes consistent with acute laminitis, including stretched lamellae, wider basal cells with low chromatin density, and a thick, wavy, and blurry appearance of the basement membrane. Biomechanical results showed no effect of oligofructose overload on physiological support of the suspensory tissue at 24 and 72h after overload; in contrast, overload increased maximal support of the tissue 72h after overload. Herd of origin and location of the sample had large effects on both physiological support and maximal support (herd=547 N/cm(2); location=531 N/cm(2)) of claw suspensory tissue (herd=260 N/cm(2); location=327 N/cm(2)). Despite clinical and histological signs of laminitis, no weakening of the suspensory tissue of the bovine claw was detected at 24 and 72h after oligofructose overload. Herd factors appeared to be important for claw suspensory tissue strength.

Polysynovitis after oligofructose overload in dairy cattle.

Acute bovine laminitis is a systemic disease with local manifestations primarily affecting the claws. However, distension of the tarsocrural joints has been observed after experimental oligofructose overload in dairy heifers as a part of the complex interpreted as acute, clinical laminitis. Therefore, the aim of the present study was to study bovine synovial joints and tendon sheaths after oligofructose overload. Ten dairy heifers received oral oligofructose overload (17 g/kg body weight); four were killed 24h after overload and six after 72 h. Six control heifers received tap water and were killed after 72 or 96 h. Clinical examination included locomotion scoring and palpation of the tarsocrural joints. Ruminal fluid and blood was collected for measurements of pH and hydration status. Total protein concentrations and white blood cell (WBC) counts were determined in synovial fluid collected from tarsocrural joints after death. Synovial joints and tendon sheaths were examined and synovial membranes were studied microscopically. Swabs taken from the synovial cavities were subject to bacteriological culture. Heifers with oligofructose overload developed signs of ruminal and systemic acidosis. Lameness was observed in three of ten heifers 24h after overload and in all remaining heifers after 72 h. Distension of tarsocrural joints was observed from 18 h after overload and peaked at 30 h when all examined joints were moderately or severely distended. The synovial fluid was turbid and protein content and WBC counts were increased at both 24 and 72 h compared with controls. Bacterial culture was negative. Synovial membranes 24 and 72 h after overload had a fibrinous and neutrophil inflammatory reaction that regressed in severity between 24 and 72 h after overload. Heifers subjected to oligofructose overload therefore developed generalized sterile neutrophilic polysynovitis. Focus on this aspect of bovine laminitis may shed new light on the pathogenesis of this complex disease.

Oligofructose overload induces lameness in cattle.

The aim was to describe the clinical orthopedic implications of oligofructose overload. A group of 8 nonpregnant dairy heifers were given an oral dose of oligofructose (17 g/kg of body weight). At predefined times during a period spanning 3 d before and 9 d after oligofructose overload, the heifers underwent a clinical examination including locomotion scoring, hoof-testing, and palpation of tarso-crural joints, as well as the collection of blood and ruminal fluid samples. Locomotion sessions were videotaped; subsequently, locomotion was blind-scored. Locomotion scores increased after oligofructose overload and declined toward the end of the study period. The greatest locomotion scores were recorded on d 3 to 5 (60 to 120 h) where 12 of 42 (29%) locomotion scores were 3 and 13 of 42 (32%) were score 2. Positive reactions to hoof-testing were observed from 30 h after oligofructose overload and reached a maximum on d 7 and 9 where 12 of 28 (43%) reactions were marked positive. Distension of the tarso-crural joints was observed from 24 h after oligofructose overload, with maximum distension being observed on d 2, in which 44 of 56 (79%) of observed joints were either moderately or severely distended. The heifers developed classic signs of acute ruminal and systemic acidosis after the oligofructose overload (ruminal pH 4.3 +/- 0.07, standard base excess -10.8 +/- 2.3 at 18 h). With few exceptions, clinical and laboratory variables returned to normal within 9 d of oligofructose overload. But, good body condition and previous feeding with grass apparently predisposed the heifers to more severe systemic affection. Oligofructose overload in dairy heifers induced ruminal and systemic acidosis, diarrhea, dehydration, and, subsequently, lameness, claw pain, and joint effusion, collectively interpreted as signs of acute laminitis. Oligofructose overload at 17 g/kg of body weight represented a relatively mild laminitis model in cattle, as demonstrated by a reasonably quick recovery from systemic as well as orthopedic signs.

Short communication: rising and lying behavior of heifers before and after alimentary oligofructose overload.

The aim of this experiment was to describe the rising and lying behavior of heifers in the first 5 d after alimentary oligofructose overload to 1) acquire information about consequences of this experimental disease model in terms of animal behavior; and 2) contribute to the evaluation of the influence of disease on cattle welfare. Eight tethered Holstein-Friesian heifers were used and their behavior was observed for 10.5 +/- 2.7 hours of light per day. Occurrence of rising and lying behavior and parts thereof were recorded. Clinical and physiological examinations were conducted throughout to confirm presence of ruminal acidosis and lameness. The duration of pre-lying intention movements were increased on d 3 after oligofructose overload compared with d -1 [28 (20 to 40) vs. 13 (10 to 16) s, respectively], and the duration of the total lying sequence was increased on d 1 and 3 compared with the control day [27 (22 to 33) and 36 (25 to 48) vs. 17 (13 to 21) s, respectively]. The frequency and duration of getting up did not differ between days. These results suggest that disease induced by oligofructose overload (i.e., ruminal acidosis and lameness) can affect lying behavior in heifers as shown by increased duration of lying intentions and difficulty in lying down, which may indicate that lying motivation was thwarted, possibly by pain or discomfort.