Abaxial Wall Research Articles

Concrete Floor–Bovine Claw Contact Pressures Related to Floor Roughness and Deformation of the Claw

The intention of this research was to study the impact of concrete floor surface roughness on a bovine claw model and to assess the deformation of the bovine claw model under load. The pressure distribution between the floor and the claw is the key method in this research. Monitoring foot-to-ground pressure distributions may provide insight into the relation between high local pressures and foot lesions. Concrete floor samples were made with 5 different finishing methods. Their roughness was determined by measuring the heights of the “peaks and the valleys” of the surface with a high-precision laser beam. The smoothest surface was the sample finished with a metal float (surface roughness Ra=0.062mm) and the roughest surface occurred with the heavily sandblasted sample (surface roughness Ra=0.488mm). The roughness of the concrete floor samples was related to the mean and peak contact pressures that can occur in a laboratory test bench between floor and bovine claw. It was found that the claw itself has approximately 2 times more effect on these contact pressures than the surface roughness. Peak pressures found were high enough (up to 111MPa) to cause damage to the bovine claw sole horn. The strains occurring in the horn wall were measured and related to the floor-finishing method and the load. Strain gauge measurements indicated that it is difficult to predict what kind of deformation of the claw wall will occur at a certain location. Different strains will occur for different floor-finishing methods. The corresponding stresses in the horn wall did not exceed the yield stress (14 and 11MPa for dorsal and abaxial wall horn, respectively).

Biomechanical Properties of Bovine Claw Horn

Inadequate properties of concrete floors in cattle houses seem to be the primary cause of most claw problems, resulting in economic losses and impaired animal welfare. Many claw diseases are sequels of an extreme local overload. In this paper, the mechanical strength of bovine claw horn is studied. The average Young's modulus E determined in bending and compression using a test velocity of 1 mm/min was 382 MPa for horn from the dorsal wall of the bovine claw, 261 MPa for horn from the abaxial wall and 13·6 MPa for bulb horn. There is a significant difference in Young's modulus, hence in stiffness, between dorsal and abaxial wall horn. The average yield stress was 14·3 MPa for dorsal wall horn and 10·7 MPa for abaxial wall horn in a three-point bending test, and 56·0 MPa for bulb horn in a compression test on samples with 100 mm2 surface area and 4 mm height. The registered average Poisson's ratio ν was 0·38. Histological observations could not explain the biomechanical differences between the dorsal and abaxial wall horn. The number of horn tubules per mm2 was smaller and the diameter of the tubules larger in bulb horn than in wall horn. In future research, the yield stress of the horn will be related with the maximum pressures that can occur between cattle claw and concrete floor.

Slatted Floors and Solid Floors: Stress and Strain on the Bovine Hoof Capsule Analyzed in Finite Element Analysis

An established finite element model of a bovine claw was used to compare mechanical stress levels in a loaded model claw on different types of flooring. The following situations were compared: a claw standing on a solid floor, a claw standing on the edge of a short tie stand, and claws standing on slatted floors with slats of 28 and 40mm (wide) running parallel and perpendicular to the claw axis. Finite element analysis allowed visualization of stress peaks seen predominantly in the weight-bearing border of the dorsal abaxial wall and of the bulbar region and in the proximal axial wall. Maximum stress values of 13MPa were found in the model claw loaded on the solid floor and values of 18 to 22MPa were seen in the model claw loaded on the edge of the solid floor. On slatted floors, stresses increased in the situation in which the claw was not supported under the abaxial wall. Comparison between the other slatted floors showed little difference in amounts of mechanical stress. A clear distinction was detected between the solid floor with full claw contact and the slatted floors. From the point of view of the mechanical stress seen in finite element analysis, a large contact area between claw and floor, as seen in the solid surface floor, is preferable. When use of slatted floors is unavoidable, direction of the slats should run perpendicular to the direction of the walkway to prevent even more mechanical impact in certain footing situations.

Characterisation of Claw–floor Contact Pressures for Standing Cattle and the Dependency on Concrete Roughness

Inadequate properties of concrete floors in livestock buildings seem to be an important cause of cattle lesions. High local pressures on claw tissues may contribute to damage of the claw. Monitoring of foot-to-ground pressure distributions may provide insight in the relation between high local pressures and foot lesions. In the current research, the pressure distribution of the foot-to-ground contact area was recorded using thin film tactile sensors. During the experiments, the sensor was located between previously prepared bovine claws and concrete samples with different surface roughness. The measurement procedure permitted a gradual increase in the vertical load on the claws at a test bench, while at the same time the contact area and the pressure distribution could be registered. Five different levels of surface roughness were obtained by finishing fresh concrete samples with a metal float, a wooden float or a brush, and by washing the concrete surface to two different degrees. The results showed a clear increase in contact area with increasing pressure. The abaxial wall and bulb of the claws had the major load-bearing function. The metal-floated concrete resulted in the largest contact area and the lowest pressures, while the washed concrete resulted in much smaller contact areas and higher pressures. Other finishing methods gave intermediate results. The maximum pressure under a load of 4 kN was about twice as high on a wooden-floated or lightly washed surface (around 40 MPa), compared to a metal-floated surface (around 20 MPa). On the severely washed out surface, the maximum pressure was even four to five times higher. This may indicate a higher risk on claw lesions due to local overload.

Maintenance Claw Trimming in Cattle with Special Emphasis on the Dutch Method

Application of the Dutch claw trimming method requires understanding of horn structure and function including growth and wear as well as the biomechanics of weight bearing. The shape and weight bearing surface of normal claws can be described as follows: The normal weight bearing area of the claw includes the heel, wall, and the white line as well as the sole.6 It is important to note that the abaxial wall is weight bearing along its entire length from the abaxial heel wall junction to the toe.6 The axial wall and white line is only weight bearing for a short distance up to a point where they diverge proximally in the interdigital space.6 The sole is weight bearing along its entire surface except at its innermost portion directly adjacent to the interdigital space. Here the sole is sloped for approximately one-third of the width of the sole in that area.6

Digital Characteristics in Commercial Dairy Herds Fed Metal-Specific Amino Acid Complexes

Five commercial dairy herds in Central New York fed metal-specific amino acid complexes were selected to evaluate digital characteristics. During the first year (period 1), herds were evaluated by a specific procedure by one individual. Three herds were not supplemented and two herds were supplemented with zinc methionine. During the subsequent year (period 2) all herds were switched to a combination of zinc methionine, copper lysine, manganese methionine, and cobalt glucoheptonate and evaluated in the same way as during period 1. There was no effect of period on incidence of heel erosion and interdigital dermatitis. During period 2, there was a reduced incidence of double soling, white line separation, sole hemorrhages, sole ulcers, and papillomatous digital dermatitis, and the incidence of wall ridges tended to be reduced compared with period 1. There was no effect of period on the incidence of abaxial wall lesions, digital arthritis, or foot rot, although the overall incidence of these disorders was low. During period 2, when cows were fed a combination of complexed trace minerals, there was a general reduction in the incidence of digital disorders associated with the laminitis syndrome complex compared with period 1; however, other time-related differences existed that may confound interpretation.

Corrective Trimming of Corkscrew Claw

Corkscrew claw is a hereditary condition affecting both front and hind claws, mostly outer hind claws, and result from a malalignment and twisting of the middle phalanx. The proximal and distal surfaces of the middle phalanx can be out of alignment by as much as 11 °. The distal phalanx is abnormally narrow and long. This malalignment causes increased pressure on the coronary corium of the abaxial wall resulting in accelerated horn growth with lateral to medial deviation of the lateral wall, which then curls under the sole replacing some of the normal weight bearing surface.

Physical and Ultrastructural Basis of Blue Leaf Iridescence in Four Malaysian Understory Plants

Iridescent blue leaf coloration in four Malaysian rain forest understory plants, Diplazium tomentosum Bl. (Athyriaceae), Lindsaea lucida Bl. (Lindsaeaceae), Begonia pavonina Ridl. (Begoniaceae), and Phyllagathis rotundifolia Bl. (Melastomataceae) is caused by a physical effect, constructive interference of reflected blue light. The ultrastructural basis for this in D. tomentosum and L. lucida is multiple layers of cellulose microfibrils in the uppermost cell walls of the adaxial epidermis. The helicoidal arrangement of these fibrils is analogous to that which produces a similar color in arthropods. In B. pavonina and P. rotundifolia the blue-green coloration is caused by parallel lamellae in specialized plastids adjacent to the abaxial wall of the adaxial epidermis. The selective advantage of this color production, if any, is unknown.

Physical and ultrastructural basis of blue leaf iridescence in four Malaysian understory plants

Iridescent blue leaf coloration in four Malaysian rain forest understory plants, Diplazium tomentosum Bl. (Athyriaceae), Lindsaea lucida Bl. (Lindsaeaceae), Begonia pavonina Ridl. (Begoniaceae), and Phyllagathis rotundifolia Bl. (Melastomataceae) is caused by a physical effect, constructive interference of reflected blue light. The ultrastructural basis for this in D. tomentosum and L. lucida is multiple layers of cellulose microfibrils in the uppermost cell walls of the adaxial epidermis. The helicoidal arrangement of these fibrils is analogous to that which produces a similar color in arthropods. In B. pavonina and P. rotundifolia the blue‐green coloration is caused by parallel lamellae in specialized plastids adjacent to the abaxial wall of the adaxial epidermis. The selective advantage of this color production, if any, is unknown.

A macroscopic study of the vascular system of the bovine hind limb claw

The vascular organisation of the hind limb claws from clinically normal cattle was studied using plastic corrosion casts. The proper digital artery ran dorsodistally within the interdigital space and gave off a bulbar branch to the bulb, a plantar branch to the axial aspect of the wall and sole, and a coronary artery to the coronary margin and proximal wall. The artery entered the distal phalanx at the axial foramen, coursed through the nutrient canal as the terminal arch, and emerged at the abaxial foramen to anastomose with branches of the bulbar artery. During its interosseous course, the terminal branch gave off 6-8 primary branches which provided the arterial supply to the coronary margin, axial and abaxial wall, white zone and sole. The dorsal proper digital vein and axial and abaxial proper plantar digital veins drained all venous blood from the claw. Each of these large veins arose from numerous smaller veins which joined to form the venous networks of the coronary margin, wall, sole and bulb. A large arched vein passed through the coronary cushion and formed a connection between the superficial coronary venous plexus and the intra-osseous plexus of the distal phalanx. The axial and abaxial proper plantar digital veins were connected by a vessel through the bulbar cushion. At the same level, the axial proper plantar digital veins of the lateral and medial claw were connected to each other by a large vessel through the interdigital space, situated just proximal to the distal interdigital ligaments. This resulted in the presence of a complete distal venous arch along the plantar aspects of both claws. The parietal collecting veins drained most of the venous blood from the sole, white zone and wall, and connected directly to the venous plexuses of the coronary margin and bulb. Valves occurred commonly in medium and larger calibre veins throughout the claw.

Histopathological and morphometric studies on the hooves of dairy and beef cattle in relation to overgrown sole and laminitis

In dairy cattle, histopathology of the outer hind claws with overgrown sole revealed arteriosclerosis of blood vessels at the ulcer site in the sole. The laminae did not show any hyperplasia of the epidermis and thrombi were not seen in the blood vessels. Partial or complete disappearnce of onychogenic substance was observed in the sole as well as in the wall epidermis. In beef animals, typical changes suggestive of chronic laminitis were seen: these included hyperplasia of the epidermis of the laminae, thrombus formation, arteriosclerosis in the corium of the sole, the abaxial wall and the coronary corium. Morphometric analysis quantified measurements of hooves of normal, beef and dairy cattle. It may be concluded that the changes associated with overgrowth of the sole in dairy cattle are localized to the sole without involvement of the laminae and that the term laminitis is not appropriate in the condition seen in dairy cattle.

Stigmatic constriction in pearl millet following infection by Claviceps fusiformis

Infection of pearl millet by Claviceps fusiformis under field conditions occurred through fresh receptive stigmas. Microconidia and macroconidia germinated only on the parts of the stigma protruding from the floret. Subsequent penetration and passage of hyphae down the stylodia closely followed the path taken normally by millet pollen. Thirty-six hours after inoculation concurrent with hyphal invasion of the upper ovary wall, a constricted region located in the fused stylodia, consisting of a collar of collapsed parenchymatous cells, became apparent. This response is the same as the stigatic constriction which occurs in response to pollination. Stigmas then withered and abscissed, effectively isolating the ovary from pollen. Colonization of the ovary by the fungus proceeded predominantly through the abaxial wall towards the vascular trace supplying the ovary. Hyphae remained intercellular throughout invasion of the stigma and colonization of the ovary. Honeydew exudation from the florets marked establishment of the sphacelium 4–5 days after inoculation.

In vitro penetration and absorption of chemicals into the ovine hoof

Techniques are described for testing the ability of chemicals to penetrate through ovine hoof horn. Most chemicals tested had penetration rates of less than 0.1 mm per hour and formalin, a chemical widely used for treatment of foot rot, penetrated very poorly (less than 0.02 mm per hour). Chloramphenicol in ethanol solution gave the highest penetration rate (0.21 to 2.38 mm per hour) and other penetrative chemicals were zinc sulphate (0.06 to 0.58 mm per hour), copper sulphate (less than 0.05 to 0.38 mm per hour) and sodium azide (less than 0.05 to 0.24 mm per hour) in aqueous solution. Inclusion of sodium lauryl sulphate in treatments enhanced the penetration rates of zinc and azide approximately sixfold. Ethanol and nickel ammonium hydroxide also improved the penetration of zinc and azide, particularly through the hard horn from the abaxial wall of the claw. Absorption of zinc from solutions containing 10 per cent zinc sulphate gave hoof tissue concentrations of zinc from 0.22 to 0.88 mg zinc ions per g tissue (10 to 20 times that found in normal hoof samples) and most of this zinc was retained after the horn was washed continuously in running water for 24 hours.

Floral development of Ruppia maritima var. maritima

A hyaline, unvascularized sheath envelops a portion of the inflorescence near maturity. Though resembling an appendage of the main axis, in early ontogeny it develops as a prophyll of the renewal growth apex below the inflorescence. Two flowers develop on the inflorescence axis, subopposite each other. Fertile appendages are initiated in an acropetal sequence on each floral bud. The first to form, in the median position, are the two stamens, the lower preceding the upper. Each stamen develops two bisporangiate thecae separated by a broad connective. A dorsiventral outgrowth is initiated slightly abaxially near the tip of the connective at the stage of theca differentiation. This outgrowth appears to be homologous with a similar outgrowth in Potamogeton densus, but not with the sterile appendages of the Potamogeton flower which, by some authors, have incorrectly been interpreted as connective outgrowths. Each carpel arises as a radial primordium which becomes peltate after its inception. One ovule is initiated at the adaxial portion (Querzone). The stigma becomes broad and flat, lobing at its margins. A slight outgrowth develops at the abaxial wall of the carpel. The floral apex has a two-layered tunica. The primordia of the stamens, carpels, and ovules arise by periclinal divisions in the second layer. Procambial development is acropetal following closely primordial inception. Each appendage, including the ovule, receives one procambial strand. The outgrowths of the connective and the carpel lack procambium.