Potential of Naftifine Application for Transungual Delivery

Naftifine is used to treat fungal skin infections as it inhibits dermatophytes, which are the cause of onychomycosis. However, naftifine's ability to permeate the human nail barrier has not been investigated, thus, the antimycotic potential is not clearly established. This work aims to evaluate the effect of penetration enhancing factors on the accumulation of naftifine hydrochloride through human nail clippings. Naftifine polymeric nail lacquers with Eudragit RL100 were developed as a suitable delivery system. Low penetration of naftifine into nail has been determined as less than 10% of applied drug dose accumulated in the nail layers. Incorporation of thioglycolic acid into formulations resulted in increased accumulation of antifungal agent in the nail layers by 100% compared with a control group. Salicylic acid did not effect naftifine accumulation in the human nail. The permeation of naftifine through the nail increased by threefold when the thioglycolic acid-containing formulation was applied and the nail was pretreated with a fractional CO2 laser. Structural changes of the nail barrier, induced by fractional CO2 laser, were visualized by microscopy. The results suggest, that naftifine nail penetration could be significantly increased when physical and chemical enhancing factors are applied.

Influence of dietary zinc on the claw and interdigital skin of sheep

Claw diseases like interdigital dermatitis and footrot threaten sheep health and are major welfare issues. Several studies mainly done in cattle suggested that zinc (Zn) supplementation may improve claw integrity. However, Zn supplements may differ markedly regarding Zn bioavailability. Zn bound to single amino acids has been shown to be more bioavailable than inorganic Zn sources. The aim of this study was to determine the effect of different Zn supplements on the integrity of the claw and interdigital skin of healthy sheep. At weaning 30 Merino lambs were randomly allocated to three different dietary treatments which were provided through the pelleted concentrates as follows: 1) no supplemental Zn (Zn0); 2) addition of 40 mg/kg Zn as Zn sulphate (ZnS); 3) addition of 40 mg/kg organic Zn as Zn amino acid complex (CZn). Barley straw and pelleted concentrates were given ad-libitum. The calculated Zn concentration of the total diet (roughage and concentrate) without supplemental Zn (Zn0) was 38 mg Zn/kg DM. The concentrates were formulated to meet the nutritional requirements for growing lambs and contained 207 g/kg DM crude protein and 12.4 MJ/kg DM metabolizable energy. After 8 weeks the lambs were slaughtered and the following specimens were collected: blood serum, liver, sole and coronary band of the claw, and interdigital skin. Serum and tissue Zn and copper (Cu) concentrations and claw hardness were determined. Routine pathohistology and electron microscopy were conducted. Franz diffusion cell system and Ki-67 immunostaining were used to determine the permeability of the interdigital skin and the keratinocyte proliferation in the basal layer of sole horn, coronary band and interdigital skin, respectively. The concentrations of Zn and Cu in serum and liver tissue as well as the Zn concentration in claw horn were not affected by dietary treatment. Zn0 lambs showed higher (p < 0.05) Cu concentrations in claw horn compared to both Zn supplemented groups. Routine pathohistology as well as electron microscopy did not show significant morphological differences between the three groups. Franz diffusion cell system proved to be a suitable method examining the interdigital skin permeability, but the group differences in this study were not significant. Dietary treatment did not affect keratinocyte proliferation in the coronary band. In the sole keratinocyte proliferation was significantly higher (p < 0.05) in the Zn0 group compared to CZn with ZnS being intermediate. Keratinocyte proliferation in the interdigital skin was significantly higher (p < 0.05) in the CZn group compared to the Zn0 with ZnS being intermediate. The results of the current experiment indicate that serum and tissue Zn concentrations and horn hardness are not affected by adding a moderate amount of Zn sulphate or Zn amino acid complex to a basal diet. However, supplemental Zn amino acid complex seems to affect keratinocyte proliferation of interdigital skin and sole horn of lambs. Effects on skin permeability should be retested using a higher number of animals prospectively.

Fumonisin B₁ (FB₁) Induces Lamellar Separation and Alters Sphingolipid Metabolism of In Vitro Cultured Hoof Explants

One of the most important hoof diseases is laminitis. Yet, the pathology of laminitis is not fully understood. Different bacterial toxins, e.g. endotoxins or exotoxins, seem to play an important role. Additionally, ingestion of mycotoxins, toxic secondary metabolites of fungi, might contribute to the onset of laminitis. In this respect, fumonsins are of special interest since horses are regarded as species most susceptible to this group of mycotoxins. The aim of our study was to investigate the influence of fumonisin B₁ (FB₁) on primary isolated epidermal and dermal hoof cells, as well as on the lamellar tissue integrity and sphingolipid metabolism of hoof explants in vitro. There was no effect of FB₁ at any concentration on dermal or epidermal cells. However, FB₁ significantly reduced the separation force of explants after 24 h of incubation. The Sa/So ratio was significantly increased in supernatants of explants incubated with FB₁ (2.5–10 µg/mL) after 24 h. Observed effects on Sa/So ratio were linked to significantly increased sphinganine concentrations. Our study showed that FB₁ impairs the sphingolipid metabolism of explants and reduces lamellar integrity at non-cytotoxic concentrations. FB₁ might, therefore, affect hoof health. Further in vitro and in vivo studies are necessary to elucidate the effects of FB₁ on the equine hoof in more detail.

Milk thistle extract and silymarin inhibit lipopolysaccharide induced lamellar separation of hoof explants in vitro

The pathogenesis of laminitis is not completely identified and the role of endotoxins (lipopolysaccharides, LPS) in this process remains unclear. Phytogenic substances, like milk thistle (MT) and silymarin, are known for their anti-inflammatory and antioxidant properties and might therefore have the potential to counteract endotoxin induced effects on the hoof lamellar tissue. The aim of our study was to investigate the influence of endotoxins on lamellar tissue integrity and to test if MT and silymarin are capable of inhibiting LPS-induced effects in an in vitro/ex vivo model. In preliminary tests, LPS neutralization efficiency of these phytogenics was determined in an in vitro neutralization assay. Furthermore, tissue explants gained from hooves of slaughter horses were tested for lamellar separation after incubation with different concentrations of LPS. By combined incubation of explants with LPS and either Polymyxin B (PMB; positive control), MT or silymarin, the influence of these substances on LPS-induced effects was assessed. In the in vitro neutralization assay, MT and silymarin reduced LPS concentrations by 64% and 75%, respectively, in comparison PMB reduced 98% of the LPS concentration. In hoof explants, LPS led to a concentration dependent separation. Accordantly, separation force was significantly decreased by 10 µg/mL LPS. PMB, MT and silymarin could significantly improve tissue integrity of explants incubated with 10 µg/mL LPS. This study showed that LPS had a negative influence on the structure of hoof explants in vitro. MT and silymarin reduced endotoxin activity and inhibited LPS-induced effects on the lamellar tissue. Hence, MT and silymarin might be used to support the prevention of laminitis and should be further evaluated for this application.

Effect of biotin supplementation on claw horn growth in young, clinically healthy cattle

The effects of orally administered biotin supplementation on the growth of claw horn in young, clinically healthy cattle were analyzed. Twelve, 1-year-old Girolando cattle were randomly assigned to receive either 12.5 mg of diluted powdered biotin (GI) or a control treatment (GII) for 40 consecutive days. Cattle in the GI group showed an average hoof growth of 11.3 +/- 0.72 mm, while those in GII had an average hoof growth of 7.2 +/- 0.78 mm. The results confirmed the positive effect of biotin supplementation on the growth of angle and length of the dorsal hoof wall, hoof sole length, and on resistance to wearing, in young cattle extensively managed.

Equine laminitis: loss of hemidesmosomes in hoof secondary epidermal lamellae correlates to dose in an oligofructose induction model: an ultrastructural study

REASONS FOR PERFORMING STUDY

Light microscopical studies show that the key lesion of laminitis is separation at the hoof lamellar dermal-epidermal interface. More precise knowledge of the damage occurring in the lamellar basement membrane zone may result if laminitis affected tissue is examined with the transmission electron microscope. This could lead to better understanding of the pathogenesis of lesions and the means of treatment or prevention.

OBJECTIVES

To investigate the ultrastructure of acute laminitis as disease of greater severity is induced by increasing oligofructose (OF) dosage.

METHODS

Three pairs of normal horses, dosed with OF at 7.5, 10 and 12.5 g/kg bwt via nasogastric intubation, developed laminitis 48 h later. Following euthanasia, their forefeet were processed for transmission electron microscopy. Lamellar basal cell hemidesmosome (HD) numbers and the distance between the basal cell plasmalemma and the lamina densa of the basement membrane were estimated and compared to control tissue.

RESULTS

Increasing OF dosage caused greater HD loss and more severe laminitis. The characteristic separation of the basement membrane, cytoskeleton failure and rounded basal cell nuclei results from combined HD dysassembly and anchoring filament failure.

CONCLUSIONS

Without properly assembled HDs, dysadhesion between the lamina densa of the basement membrane (BM) and epidermal basal cells occurs, emphasising the fundamental importance of HDs in maintaining attachment at the lamellar interface. Medical conditions that trigger lamellar matrix metalloproteinase (MMP) activation and/or compromise entry of glucose into lamellar basal cells appear to promote loss and failure of HDs and, therefore, laminitis development.

POTENTIAL RELEVANCE

A correlation between lameness severity and escalating loss of lamellar HDs now exists. Therapy aimed at protecting the lamellar environment from haematogenous delivery of MMP activators or from glucose deprivation may control laminitis development.

Induction of laminitis by prolonged hyperinsulinaemia in clinically normal ponies

The purpose of this study was to determine the effects of prolonged administration of insulin, whilst maintaining normal glucose concentrations, on hoof lamellar integrity in vivo on healthy ponies with no known history of laminitis or insulin resistance. Nine clinically healthy, unrelated ponies were randomly allocated to either a treatment group (n =5; 5.9+/-1.7 years) or control group (n =4; 7.0+/-2.8 years). The treatment group received insulin via a euglycaemic hyperinsulinaemic clamp technique modified and prolonged for up to 72 h. Control ponies were infused with an equivalent volume of 0.9% saline. Ponies were euthanized at the Obel grade 2 stage of clinical laminitis and hoof lamellar tissues were harvested and examined for histopathological evidence of laminitis. Basal serum insulin and blood glucose concentrations were 15.7+/-1.8 microU/mL and 5.2+/-0.1 mmol/L, respectively (mean+/-SE) and were not significantly different between groups. Mean serum insulin concentration in treatment ponies was 1036+/-55 microU/mL vs. 14.6 microU/mL in controls. All ponies in the treatment group developed clinical and histological laminitis (Obel grade 2) in all four feet within 72 h (55.4+/-5.5h), whereas none of the control ponies developed laminitis. There was no clinical evidence of gastrointestinal involvement and the ponies showed no signs of systemic illness throughout the experiment. The data show that laminitis can be induced in healthy young ponies, with no prior history of laminitis, by maintaining prolonged hyperinsulinaemia with euglycaemia. This suggests a role for insulin in the pathogenesis of laminitis, independent of hyperglycaemia, or alterations in hind-gut fermentation. For the clinician, early detection and control of hyperinsulinaemia may facilitate management of endocrinopathic laminitis.

Nail swelling as a pre-formulation screen for the selection and optimisation of ungual penetration enhancers

INTRODUCTION

Targeting drug treatment to fungal infections that reside within or below the nail plate is problematic due to the highly restrictive barrier of the human nail. To optimise topical formulations for ungual drug delivery, inclusion of an effective penetration enhancer (PE) is imperative. At present, in vitro nail permeation studies can take weeks or months in order to obtain any meaningful data because the lack of a simple in vitro model to identify and develop nail PEs makes the selection and optimisation of novel PEs an empirical and inefficient process. The aim of this study was to compare three methods for pre-formulation screening of putative ungual PEs and then to select the most suitable technique for screening candidates that may enhance the permeation of therapeutic agents through the human nail.

METHODS

Three screening techniques were evaluated; nail swelling (weight increase of human nail clippings), horse hoof swelling (weight increase of horse hoof clippings) and nail penetration of a radiolabelled permeability probe. Four test PEs were evaluated using each screening method and nail swelling was identified as a simple, rapid, economic, relevant and reliable technique. This screen was then used to evaluate 20 potential PEs. Thioglycolic acid (TA), hydrogen peroxide (H(2)O(2)) and urea H(2)O(2) produced the greatest nail weight increases; 71.0+/-4.6%, 69.2+/-6.6%, and 69.0+/-9.9 respectively. To confirm the relationship between human nail swelling and altered ungual barrier function, a permeation study was performed in human nails using caffeine as a model penetrant.

RESULTS AND DISCUSSION

Human nails pre-treated with TA in vitro had a 3.8-fold increase in caffeine flux compared to the control (TA-free solution). This study illustrated the potential to use human nail clipping swelling as a surrogate marker of PE activity for topical ungual drug delivery.

An investigation into keratinolytic enzymes to enhance ungual drug delivery

The topical therapy of nail diseases is limited by the low permeability of drugs through the nail plate. To increase drug penetration, the integrity of the nail plate must be compromised to a certain extent. We hypothesised that keratinolytic enzymes might decrease the barrier properties of the nail plate by hydrolysing the nail keratins, and thereby enhance ungual drug permeation. To determine enzyme action on nail plates, nail clippings were incubated at 35 degrees C, in the presence of keratinase at optimal pH for 48h, after which the nail plates were examined using scanning electron microscopy. It was found that the enzyme acted on the intercellular matrix which holds nail cells together, such that corneocytes on the dorsal surface separated from one another and 'lifted off' the nail plate. In addition, the surface of the corneocytes was corroded. Permeation studies using modified Franz diffusion cells and bovine hoof membranes as a model for the nail plate showed that the enzyme enhanced drug permeation through the hoof membrane. The permeability and partition coefficients, and the drug flux were found to be significantly increased in the presence of the enzyme. We can conclude that the enzyme, via its hydrolytic action on nail plate proteins, could increase ungual drug delivery.

Treatment strategies for digital dermatitis for the UK

Digital dermatitis is a worldwide disease causing lameness in cattle, especially when housed. Despite its widespread nature there are relatively few peer-reviewed articles providing experimental data concerning its treatment and control. At the risk of descending to anecdote, this review attempts to summarise the current state of knowledge. Three approaches to digital dermatitis treatment have been used: (1) systemic antibiotics, (2) individual topical treatment, and (3) mass topical therapy using a footbath. Systemic antibiotics have become a rare treatment because of their cost and perceived lack of efficacy. Individual topical treatment, mainly with antibiotic preparations, is the most commonly reported method. It is widely considered the treatment of choice by virtue of reliable information about efficacy, the advantage of precise targeting of antibiotic usage and the requirements of legislation. However, at least in the UK, mass treatment of digital dermatitis by foot bathing is commonly used on many farms. In some cases, for example with antibiotic footbath solutions, these treatments create legislative, health and safety and environmental difficulties. Despite the widespread use of many different treatments, there is a lack of good comparative data and the consequence is a very variable and somewhat anecdotal approach in the field. There is a pressing need for well-researched treatment strategies for different herd situations.

Softening of cattle hoof soles and swelling of heel horn by environmental agents

Bovine soles and shavings from the heel were used in laboratory tests that examined the softening and swelling effects of rainwater, cow slurry (faeces plus urine), urine, silage effluent, and washings from recently laid concrete. Formalin, glutaraldehyde and butyraldehyde were compared for their ability to prevent softening induced by water, urine or urea plus 2-mercaptoethanol. Exposure to rainwater, slurry or urine for 72 h softened the soles on average by 16, 13 and 14 Shore Durometer Units. Silage effluent had less softening effect on soles (7 Shore Durometer Units), and pre-treating heel shavings with silage effluent reversed the swelling effect of water. Washings and scrapings taken from 3- and 7-d-old concrete surfaces prepared from Portland cement, caused swelling in heel shavings by a factor of 1.5 and 1.3. Formaldehyde, glutaraldehyde and butyraldehyde pre-treatment reduced the sole softening effect of urea plus 2-mercaptoethanol in cow soles. Formaldehyde and glutaraldehyde pre-treatment reduced the sole softening effect of urine, and formaldehyde was effective at reducing concrete washings-induced swelling. The findings are relevant to solar bruising and ulceration in cattle.

Effects of Topical Nitroglycerine Patches and Ointment on Digital Venous Plasma Nitric Oxide Concentrations and Digital Blood Flow in Healthy Conscious Horses

OBJECTIVE

To measure and compare palmar digital venous plasma nitric oxide (NO) concentrations and digital arterial blood flow after application of topical nitroglycerine (NTG).

STUDY DESIGN

Experimental study.

ANIMALS

Healthy adult horses (n=8).

METHODS

Digital blood flow was measured by an ultrasonic Doppler flow probe surgically implanted around the medial palmar digital artery. Blood was collected from a catheter placed in the medial palmar digital vein for quantification of NO. NTG patches, NTG ointment or control patches were placed over the palmar digital vessels at the level of the fetlock. Two horses had an intra-arterial infusion of an NTG solution into the medial palmar digital artery in a pilot study.

RESULTS

Digital arterial blood flow did not change significantly with application of the NTG patches, NTG ointment, or control patches. There were no statistically significant or biologically important changes in digital venous NO concentrations across time or between treated and control horses. In the pilot study, digital arterial blood flow and palmar digital venous NO concentrations increased with intra-arterial infusion of NTG.

CONCLUSIONS

In clinically healthy horses, digital arterial blood flow and digital venous plasma NO concentrations did not change significantly with application of the NTG patches/ointment. These treatments are unlikely to have an effect on the digital vasculature of laminitic horses, however, further investigation is warranted.

CLINICAL RELEVANCE

Although NTG patches have been used as a method of decreasing vasomotor tone and improving digital blood flow in horses with laminitis, this study provides evidence in healthy conscious horses that this treatment is not effective in altering digital blood flow.

Efficacy of the Non-antibiotic Paste ProtexinR Hoof-Care for Topical Treatment of Digital Dermatitis in Dairy Cows

In this study, the efficacy of the non-antibiotic paste Protexin Hoof-Care containing metallic salts and organic acids, was tested for local treatment of 26 acute digital dermatitis lesions. The control group (26 cases) was treated with local application of oxytetracycline spray. These 52 affected limbs with digital dermatitis were diagnosed in 47 dairy cows from eight different farms with slatted floors. The therapeutic effect was evaluated using a scoring system for weightbearing at stance, lameness at walk and pain of the digital dermatitis lesions. The pre-treatment and control examination scores were documented on days 0, 4, 10 and 28. Both treatment regimens were effective, no statistical differences regarding the examined parameters was found between the group treated with the non-antibiotic Protexin Hoof-Care paste and the group treated with oxytetracycline spray. Twenty-seven digital dermatitis lesions required only one treatment with one of these products. A second topical treatment was carried out on day 4 in 13 lesions of the study group and in 12 lesions of the control group. The data of this pilot study indicate that the non-antibiotic paste Protexin Hoof-Care could be a valuable alternative to topical antibiotic treatment for digital dermatitis in dairy cattle.

Effects of biotin supplementation on serum biotin levels and physical properties of samples of solar horn of Holstein cows

Effects of dietary biotin supplementation on serum biotin levels and physical properties of sole horn of 40 Holstein cows were evaluated. The mean serum biotin level in biotin-supplemented cows after 10 mo of biotin supplementation (1163.2 +/- 76.2 pg/mL) was significantly higher (P = 0.007) than that in control cows (382.0 +/- 76.2 pg/mL). The sole horn of biotin-supplemented cows was significantly harder (P = 0.026) and had a significantly lower moisture content (P = 0.021) than that of control cows. No morphologic differences in horn tubules or intertubular horn were found between the biotin-supplemented and control cows. The total lipid content of sole horn was significantly higher (P = 0.030) in the biotin-supplemented cows than in the control cows. These results suggest that dietary biotin supplementation causes increases in serum biotin levels and changes in physical properties and fat content of sole horn.

The impact of parity and duration of biotin supplementation on white line disease lameness in dairy cattle

A field study was conducted to examine effects of oral biotin supplementation for up to 18 mo on risks of lameness in dairy cows. The study included a total of 900 cattle from five dairy farms in Gloucestershire, southwest U.K., in a within-herd randomized control trial. The data from this trial were used in this paper to investigate the impact of parity and duration of supplementation with oral biotin at 20 mg/d on white line disease (WLD) lameness. Analysis of the data indicated that WLD increased with increasing parity independent of biotin supplementation from approximately two cases per 100 cow years in primiparous cows to 15.5 cases per 100 cow years in all multiparous cows, but up to 47.7 cases per 100 cow years for cows in parities > or = 5. Supplementation with biotin reduced WLD lameness by 45% in multiparous cows down to 8.5 cases per 100 cow years, whereas the effect of biotin supplementation in primiparous cows was not significant. Although numerical reductions in WLD lameness were observed for shorter periods of supplementation, a supplementation length of at least 6 mo was required to significantly reduce the risk of WLD lameness in multiparous cows. The effect of biotin supplementation in reducing lameness has potential impact for both animal welfare and farm economics.

Diagnosis, treatment, and farriery for horses with chronic heel pain

In conclusion, horses with heel or navicular area pain vary, and no one treatment option is suitable for all horses. Each horse must be evaluated individually to determine which structure in the palmar aspect of the foot is injured, severity of disease, horse and hoof conformation, and horse use and level of performance expectation before a treatment plan can be developed. Overall, there are many treatment options to help these horses to perform their intended athletic event.

Submural histopathologic changes attributable to peracute laminitis in horses

OBJECTIVE

To describe submural histopathologic changes attributable to peracute laminitis in horses.

ANIMALS

20 adult horses.

PROCEDURE

A concurrent-control design was used to compare laminar lesions in 10 horses subjected to carbohydrate-induced laminitis with laminar characteristics of 10 sex- and aged-matched control horses with normal feet. Horses in the treatment group were administered an overload of carbohydrate. Tissues were obtained by biopsy 4 to 8 hours after onset of lameness or 72 hours after administration of the carbohydrate overload when lameness did not develop. Sections were stained with H&E, Masson's trichrome, and periodic acid-Schiff stains. Histopathologic changes were analyzed to detect differences between groups and to correlate epidermal changes with severity and duration of lameness.

RESULTS

Analysis indicated that dermal and epidermal lesions were evident despite lack of visible separation of the epidermal basement membrane, can be found in horses without detectable lameness, and were nonspecific and progressive following onset of lameness. Furthermore, severity and location of lesions were associated with severity and duration of lameness.

CONCLUSION AND CLINICAL RELEVANCE

These observations are consistent with the concept that separation of the laminar epithelial basement membrane is a delayed step in the pathogenesis of acute laminitis, digital vascular hypoperfusion is an underlying cause for laminitis, and the potential for repeated episodes of subclinical laminitis may underlie the development of structural and mechanical changes consistent with chronic laminitis despite lack of clinical signs of acute laminitis.

Evaluation of the local analgesic effect of ketamine in the palmar digital nerve block at the base of the proximal sesamoid (abaxial sesamoid block) in horses

OBJECTIVE

To evaluate the local analgesic effect of ketamine in a palmar digital nerve block at the base of the proximal sesamoid (abaxial sesamoid block) in horses.

ANIMALS

36 mature healthy Andalusian horses.

PROCEDURE

Horses were randomly assigned to 4 groups of 9 horses each and received an abaxial sesamoid block in a randomly chosen forelimb with 1 of the following: saline (0.9% NaCl) solution, 1% ketamine solution, 2% ketamine solution, or 3% ketamine solution. To determine analgesia, the radiant heat lamp-hoof withdrawal model was used as a noxious thermal stimulus. Before each nerve block, baseline hoof withdrawal reflex latency (HWRL, time between lamp illumination and withdrawal of the hoof) was determined; after the nerve block, local analgesic effects were determined by measuring HWRL at 2 and 5 minutes after injection and then every 5 minutes for a total period of 1 hour.

RESULTS

Significant differences in HWRL were found between baseline values and values at 2 to 15 minutes following a nerve block with ketamine. Significant differences were found between HWRL values at every time point from 2 to 10 minutes following a nerve block with saline solution, compared with 1 or 2% ketamine solution. Similarly, significant differences were found between HWRL values at every time point from 2 to 15 minutes following a nerve block with saline solution, compared with 3% ketamine solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Abaxial sesamoid block with ketamine ensures adequate analgesia in horses with an onset of action of 2 minutes and a maximal duration of action of 15 minutes.

Glucocorticoids and laminitis in the horse

The administration of exogenously administered GCs and syndromes associated with GC excess are both attended by increased risk for the development of laminitis in adult horses. However, there exists substantial controversy as to whether excess GCs cause laminitis de novo. If true, the pathogenesis of laminitis arising from the effects of GC excess is probably different from that associated with diseases of the gastrointestinal tract and endotoxemia. Although a satisfactory explanation for the development of laminitis as a consequence of GC action is currently lacking, numerous possible and plausible theoretical mechanisms do exist. Veterinarians must exert caution with respect to the use of GCs in adult horses. The extent to which individual horses are predisposed to laminitis as a result of GC effect cannot be predicted based on current information. However, the administration of systemic GCs to horses that have been previously affected by laminitis should be used only with extreme caution, and should be accompanied by careful monitoring for further signs of laminitis. The risk of laminitis appears to be greater during treatment using some GCs (especially dexamethasone and triamcinalone) compared with others (prednisone and prednisolone). Whenever possible, to reduce the risk of laminitis, GCs should be administered locally. For example, the risk of GC-associated laminitis is evidently considerably reduced in horses affected with chronic obstructive pulmonary disease (COPD) if GC treatment is administered via inhalation. We have hypothesized that structural changes in the equine hoof that resemble laminitis may arise as a consequence of excess GC effect. Although these changes are not painful per se, and are not associated with inflammation, they could likely predispose affected horses to the development of bona fide laminitis for other reasons. Moreover, the gross morphological appearance of the chronically GC-affected hoof resembles that of a chronically foundered hoof in some respects. Further investigation into the effect of GC on the hoof lamellar interface is clearly needed.

Thermolysin activates equine lamellar hoof matrix metalloproteinases

Cultured equine lamellar hoof explants secrete the pro-enzymes matrix metalloproteinase-2 (MMP-2, 72 kDa) and MMP-2 (92 kDa). Untreated explants remained intact when tested on a calibrated force transducer, but when treated with an MMP activator, developed "in-vitro laminitis", separating at the dermal-epidermal junction. Explants treated with the bacterial protease thermolysin separated dose-dependently; this was accompanied by activation of both MMP-2 and -9. Thermolysin-mediated MP activation did not occur in a cell-free system and was not inhibited by the addition of the MMP inhibitor and batimastat. These findings suggest that thermolysin-mediated gelatinase activation is not dependent on membrane-bound matrix metalloproteinase (MT-MMP) activation, providing further evidence that bacteria can produce potent MMP activators that probably facilitate host invasion.

A longitudinal field trial of the effect of biotin on lameness in dairy cows

A longitudinal prospective intervention study investigated the effect of biotin supplementation on the incidence (new cases per day) of visible lameness in milking cows and heifers on five commercial farms in Gloucestershire, United Kingdom. The trial lasted from June 1997 to April 1999. Each farm participated in the trial for 18 mo. Within each herd the cows were randomly allocated to either receive a supplement of 20 mg of biotin per day or not. All cows were run as one herd on each farm. When a lame cow was identified, the farmer called one of six veterinarians to examine and treat the affected animal; findings were recorded on a standard form. A veterinarian also carried out a bimonthly locomotion assessment to ensure that all lame cows were diagnosed. There were a total of 900 cows, 1120 cow years, in the trial. The overall incidence rate of lameness (per 100 cows per year) was 68.9, with a range of 31.6 to 111.5 per farm. The incidence rates of the four most frequently reported causes of lameness were sole ulcer, 13.8; white line separation, 12.7; digital dermatitis, 12.0; and interdigital necrobacillosis, 7.1 per 100 cows per year. There was a significant difference in the incidence rate of these four lesions between supplemented and unsupplemented cows on two of the five farms, with a significant decrease in lameness in the cows supplemented with biotin. When all the farms were pooled, the risk of lameness caused by white line separation in cattle supplemented with biotin was approximately halved (Cox proportional hazard survival analysis hazard ratio = 0.57).

Effect of dietary selenium source, level, and pig hair color on various selenium indices

The first experiment evaluated the effects of feeding various levels of Se, two Se sources, and hair color on selenosis responses in growing-finishing pigs. The study conducted in two replicates was a 2 x 6 x 2 factorial arrangement in a split-plot design. Sodium selenite and Se-enriched yeast added at 0.3, 1, 3, 5, 7, and 10 ppm Se served as the main plot and pig hair color as the subplot. A total of 96 crossbred pigs were allotted and fed their treatment diets for a 12-wk period. White and dark (red or black) hair samples were collected from the dorsal-midline at the 4-, 8-, and 12-wk periods from one pig of each hair color from each treatment pen. Lower pig weights (P < 0.10) and daily gains (P < 0.05) occurred as dietary Se level increased when pigs were fed either Se source. Selenosis responses were somewhat more severe, when the inorganic Se source was fed. Alopecia and hoof separation were encountered after the 8-wk period when pigs were fed inorganic rather than organic Se. Plasma Se increased as dietary level increased (P < 0.01), when organic Se was provided (P < 0.01), and was higher (P < 0.05) when pigs were white-haired. A time x hair color x dietary Se level interaction (P < 0.05) occurred, in which hair Se concentration was higher in dark- than in white-colored pigs and increased as dietary Se level increased as the experiment progressed. The correlation coefficient between dietary Se level and hair Se concentration averaged 0.90 (P < 0.01). Cysteine was the amino acid in the highest concentration in hair, but this and other amino acids were not affected by Se level, Se source, or hair color. A second experiment was a 3 x 6 factorial arrangement in a split-plot design with three 9-mo-old gilts from each of the Yorkshire, Duroc, and Hampshire breeds to determine whether hair Se concentration differed by body location and breed. Hair samples were collected from the shoulder, back, rump, front-leg, belly, and hind-leg areas. Hair Se concentration was higher in red- and white-haired pigs and lower in black-haired gilts (P < 0.01). Higher hair Se concentrations (P < 0.05) occurred from the lower than from the upper body areas. Our results suggest that selenosis occurs at dietary levels > 5 ppm and that white-haired pigs exhibit alopecia sooner than dark-haired pigs. No difference in hair Se concentration occurred when diets were < 1 ppm Se, but as dietary Se level increased dark-haired pigs retained more Se in their hair than white-haired pigs.

Comparative effects of high dietary levels of organic and inorganic selenium on selenium toxicity of growing-finishing pigs

This experiment evaluated the effect of high dietary Se levels using organic or inorganic Se on the selenosis responses in growing-finishing swine. A 2 x 4 factorial arrangement of treatments in a randomized complete block design was conducted in two replicates. Sodium selenite or Se-enriched yeast was added at 5, 10, 15, or 20 ppm Se to corn-soybean meal diets. A basal diet without added Se was a ninth treatment group. Ninety crossbred barrows initially averaging 24.7 kg BW were allotted at five pigs per pen. Pigs were bled at 3-wk intervals and plasma Se, glutathione peroxidase (GSH-Px) activity, glutamic oxalacetic transaminase (PGOT), hemoglobin, packed cell volume, and blood cell Se concentration were measured. After 12 wk, pigs were killed and various tissues and bile were collected for Se analyses. Pig body weights, daily gains, and feed intakes were similar for both Se sources when provided at < or = 5 ppm Se, but each measurement declined in a different manner for each Se source as the dietary Se level increased. The decline was more rapid when the inorganic rather than organic Se source was fed, resulting in interaction responses (P < 0.01). Hair loss (alopecia) and separation of the hoof at the coronary band site occurred at > or = 10 ppm inorganic Se but at > or = 15 ppm organic Se level. Plasma GSH-Px activity increased (P < 0.01) when high dietary Se levels of either Se source was fed. Plasma and blood cell Se increased at each period as dietary Se level increased (P < 0.01) and was greater when organic Se was provided (P < 0.05). Blood cell Se concentration reached a plateau when inorganic Se, but not when organic Se, was fed and increased as the experiment progressed. This resulted in a three-way interaction (P < 0.01). Plasma GOT activity at the 12-wk period was elevated when inorganic Se was provided at > or = 15 ppm Se but not when organic Se was fed, resulting in an interaction (P < 0.05). Tissue Se concentrations increased as dietary Se level increased and when organic Se was provided, resulting in interaction responses (P < 0.05). Bile was a yellow color when the basal diet was fed but was dark brown at > 10 ppm inorganic Se and at 20 ppm when organic Se was provided. Bile Se increased as dietary Se level increased (P < 0.01). These results suggest that dietary Se from inorganic or organic sources was toxic at > or = 5 ppm Se, but subsequent selenosis effects were more severe and occurred sooner when sodium selenite was the Se source.

Effect of sodium bisulfate on skin and hooves of horses

OBJECTIVE

To evaluate the safety of sodium bisulfate for use in horse barn environments by determining its irritant effect on skin and hooves.

ANIMALS

6 female mixed-breed ponies.

PROCEDURE

Sodium bisulfate was applied to clipped intact skin of 6 ponies to evaluate its irritant effect after single (48 hours) and repetitive (6 h/d for 10 days) applications; similar areas of skin were used as untreated control sites. In addition, sodium bisulfate was applied to the sole of both front hooves of each pony and covered with wet gauze, and the entire hoof was covered with adhesive tape for 48 hours.

RESULTS

Contact with moistened sodium bisulfate for 48 hours had no effect on pony skin. Contact with sodium bisulfate for 6 hours on 10 consecutive days did not cause gross changes but did cause mild to moderate microscopic changes including epidermal necrosis, hyperkeratosis, capillary congestion, edema, and diffuse mixed inflammatory cell infiltrate. All changes were limited to the epidermis and superficial dermis. Gross changes in hoof sole, signs of lameness, and increase in digital pulse pressure or pulse intensity were not detected.

CONCLUSIONS AND CLINICAL RELEVANCE

Duration of contact with sodium bisulfate in this study was in excess of that expected under typical husbandry conditions. Despite this fact, gross changes in skin and hooves were not detected. Microscopic lesions were confined to the epidermis and superficial dermis. Results suggest that contact with sodium bisulfate under these conditions is safe.

The influence of long-term supplementation with biotin on the prevention of lameness in pasture fed dairy cows

In a double-blind study, the influence of biotin supplementation on lameness in dairy cows was investigated over a 13-mo period. The experimental site was a tropical upland environment and involved over 2705 Holstein and Friesian cows on 20 participating farms. Cows on 10 farms received biotin at a rate of 20 mg/head per day in the concentrate, and cows on 10 other farms received feed without the biotin supplement. Premixes with or without biotin were incorporated into a grain concentrate that was fed at a constant rate to cows at milking. Farmers maintained accurate records of the nature of hoof problems and any treatment applied. Each herd was evaluated for locomotion scores at 8-wk intervals. Locomotion scores were significantly correlated with the number of days with measurable rainfall per month (r = 0.88). The biotin-supplemented herds exhibited better locomotion scores than the unsupplemented herds. In the wet summer period the number of lame cows, as observed by the farmer, were significantly fewer during the rainy period for the biotin-supplemented herds and required fewer antibiotic treatments than unsupplemented herds. Most hoof lesions were most commonly observed in the outer claws of the hind limb. Daily milk production (17.3 vs. 18.5 L) was not affected by biotin supplementation. Reduced milk fat percentage and somatic cell counts of bulk milk were recorded in the biotin supplemented herds during the wet, summer period.

Use of caryophyllene oxide as an antifungal agent in an in vitro experimental model of onychomycosis

Caryophyllene oxide, an oxygenated terpenoid, well known as preservative in food, drugs and cosmetics, has been tested in vitro as an antifungal against dermatophytes. Its antifungal activity has been compared to ciclopiroxolamine and sulconazole, commonly used in onychomycosis treatment and chosen because of their very different chemical structures. So, a new model has been tested, utilizing sheep hoof plates in order to simulate human nails, which are almost unobtainable for in vitro tests. Three protocols were utilized: pre-treatment, simultaneous treatment and post-treatment. Among these, the post-treatment method was the best to simulate antifungal therapy, as it permitted testing and comparing the efficiency of different antifungal drugs.

The role of prostanoids and nitric oxide in endotoxin-induced hyporesponsiveness of equine digital blood vessels

Endotoxin has been implicated in the pathophysiology of acute laminitis. The aim of this study was to examine the direct effects of endotoxin on isolated equine digital blood vessels. Equine digital veins (EDV), incubated in Krebs-Henseleit solution containing lipopolysaccharide (LPS) (1 microg/ml) became hyporesponsive to 5-HT after 16 h. Cycloheximide and ibuprofen blocked this effect of LPS and increased the maximum response obtained to 5-HT when compared to control vessels. L-nitroarginine methyl ester (L-NAME) reversed the hyporesponsiveness caused by LPS. Vessels maintained in culture medium containing LPS also became hyporesponsive to 5-HT, an effect which was completely prevented by ibuprofen but only partially reversed by L-NAME. Measurements were made of 6-keto PGF1alpha and nitrite production by segments of equine digital artery and vein in culture medium alone or co-cultured with peripheral blood leucocytes. LPS did not stimulate nitrite production from vessel segments but increased nitrite release from leucocytes, an effect which was inhibited by cycloheximide and L-NAME. Lipopolysaccharide increased 6-keto PGF1alpha production by blood vessels, an effect which was inhibited by cycloheximide and ibuprofen but not L-NAME. No synergistic effect on release of nitrite or 6-keto PGF1alpha was noted in co-cultures of blood vessels and leucocytes. These data suggest that induction of cyclo-oxygenase by LPS was a major cause of hyporesponsiveness of digital blood vessels to 5-HT. Release of nitric oxide was not detectable in LPS-stimulated blood vessels maintained in culture even in the presence of activated leucocytes yet L-NAME did protect against LPS-induced hyporesponsiveness indicating nitric oxide synthase induction may play some role in the effect of LPS. These findings are important in furthering our understanding of the pathophysiological mechanisms underlying the vascular changes which occur in acute laminitis.

Effect of endocrine and paracrine factors on protein synthesis and cell proliferation in bovine hoof tissue culture

Laminitis is a major cause of lameness in dairy cattle, and is widely attributed to a defect in the horny tissue that gives the hoof its mechanical strength. Defective horn is associated with, and may be preceded by, impaired keratin deposition in the hoof epidermis. The cause of abnormal keratin deposition is not easily identified but, like epidermal keratinization in other tissues, is likely to be controlled by hormones and the paracrine action of locally produced growth factors. The hormonal regulation of keratin synthesis and cell proliferation in the bovine hoof was studied using tissue explants in organ culture. As the highest incidence of laminitis is in early lactation, the study focused on insulin, cortisol and prolactin, three hormones implicated in lactogenesis and galactopoiesis. Incubation of tissue explants for 24 h in medium containing insulin (10-5000 ng/ml) stimulated protein synthesis measured by incorporation of 35S-labelled amino acids. Histochemical examination showed that insulin binding co-localized with the site of protein synthesis. Insulin also stimulated DNA synthesis, an index of cell proliferation, which was measured by incorporation of [3H]methyl thymidine. Cortisol (10-5000 ng/ml) decreased protein synthesis, whereas prolactin (10-5000 ng/ml) had no significant effect on protein or DNA synthesis. Epidermal growth factor (10-200 ng/ml), a potent inhibitor of keratinization in other tissues, stimulated protein synthesis compared with untreated controls. Epidermal growth factor binding was located microscopically to the germinal and differentiating epidermal layers. SDS-PAGE and fluorography showed that the population of proteins synthesized in the presence of any hormone or growth factor combination did not differ from that in untreated controls and included the keratins involved in horn deposition. The results show that bovine hoof keratinization is under endocrine and growth factor control, and suggest that systemic changes in lactogenic hormones may act to inhibit keratin deposition.

Batimastat (BB-94) inhibits matrix metalloproteinases of equine laminitis

A method for culturing explants of lamellar hoof was developed to investigate the process of lamellar separation that occurs in laminitis. Explants, consisting of hoof wall, dermal and epidermal lamellae and the adjacent sub-lamellar connective tissue remained intact when cultured in tissue culture medium for 2 days. However, when cultured in the presence of the matrix metalloproteinase (MMP) activator aminophenylmercuric acetate (APMA), the lamellae separated when tension was applied by pulling the hoof wall in an opposite direction to the connective tissue. The separation occurred between the epidermal basal cells and the basement membrane therefore mimicking the lesion of laminitis. Electrophoresis of culture medium from control hoof explants into gradient polyacrylamide gels co-polymerised with gelatin revealed that the explants had produced 2 gelatinases of molecular weight 92 and 72 kDa corresponding to EqMMP-9 and EqMMP-2 respectively. Minor bands of lower molecular weight were the active forms of these enzymes. The zymograms of culture medium from APMA treated explants revealed an increase in the amount of active MMPs. Equine polymorphs cultured for 2 days produced only EqMMP-9. Lamellar explant medium from horses with acute laminitis contained increased amounts of zymogen and active EqMMP-2 and EqMMP-9 particularly in explants from the fore hooves. Zymography of homogenates of normal lamellar hoof tissue revealed only EqMMP-2 and a minor active band. However, homogenates of lamellar tissue from horses with laminitis showed that EqMMP-9 was present as well as increased EqMMP-2 in both zymogen and active forms. Addition of the MMP inhibitor batimastat (BB-94) to the culture medium of APMA treated explants prevented lamellar separation. BB-94 incubated with polyacrylamide strips containing the MMPs from laminitis affected lamellar explants inhibited enzymatic activity at a concentration of 1 mmol/l. It is concluded that activation of MMPs may be responsible for the lamellar separation seen in laminitis and that MMP inhibitors may be useful clinically for preventing this process.

Effect of a supplementary dietary evening primrose oil mixture on hoof growth, hoof growth rate and hoof lipid fractions in horses: a controlled and blinded trial

The lipid chemistry of the normal equine hoof, together with the effect of oral supplementation with an evening primrose oil mixture (EPOM) on its growth, growth rate and lipid content was assessed in a controlled and blinded feeding trial at the Defence Animal Centre. Twelve horses were paired as closely as possible according to sex, age, weight, height and colour and then one from each pair was randomly allocated to treatment or control groups. The treatment group received 30 ml of oral EPOM/day, otherwise the nutrition and management regimes were the same for all horses. No significant differences (P > 0.05) were seen between treatment and control groups for hoof horn growth or growth rate. However, there was a significant difference (P < 0.05) in hoof horn growth within the treatment group only between weeks 4 and 8 after the start of supplementation. The stratum medium contained significantly higher amounts of cholesterol ester (P < 0.05), triglycerides (P < 0.001) and free fatty acids (P < 0.05) than the periople. The periople contained significantly higher levels of free cholesterol and phospholipid (P < 0.001) than the stratum medium of the hoof wall. There were no significant differences (P > 0.05) between treatment and control groups for any of the lipid fractions measured for the stratum medium from the clippings of the hoof wall. However, there were differences in perioplic lipid analysis with significant increases (P < 0.05) in cholesterol esters and partial glycerides and a significant reduction (P < 0.001) in free cholesterol in the treatment group following supplementation.

Pathology of experimentally induced chronic selenosis (alkali disease) in yearling cattle

Prolonged oral exposure of cattle to elevated dietary selenium (Se) in forage and seleniferous plants in seleniferous areas of the western United States is associated historically with 2 clinical syndromes: alkali disease and "blind staggers." The potential for Se-induced disease in cattle and other species is considerable in areas with seleniferous shales, Se-accumulating plants, arid climates, and alkaline soils. These 2 Se-associated conditions were defined in the 1930s and 1940s, and the nosology of blind staggers is questionable. Seventeen yearling steers fed 0.15, 0.28, and 0.8 mg Se/kg body weight as selenomethionine or selenite for 120 days were euthanized and examined postmortem. Significant lesions were confined to 4 steers in the medium- and high-dose selenomethionine group and to 1 steer in the high-dose selenite group. Grossly, dystrophic hoof lesions developed in 2 steers, 1 of which had extensive separation of horn from lamellar and coronary epidermis and also lost hair from the tail switch. Histologically, tubules in the stratum medium of hooves from these 5 steers were replaced by islands of parakeratotic cellular debris, separated by more normal hoof matrix. Two of the 5 steers also had hyperplasia, acanthosis, parakeratosis, and disorganized germinal epithelium of varying severity in hoof epithelium, particularly at the tips of epidermal lamellae. These changes may distinguish the hoof lesions of chronic selenosis from those of chronic laminitis in cattle, in which dermal (chorial) changes predominate. In skin from the distal part of the tail of the animal that lost its switch, most follicles were atrophic and devoid of hairshafts and displayed dyskeratosis and mild superficial follicular keratosis. No significant lesions developed in tissues other than integument. Autometallographic staining for catalytic Se bonds in various tissues, including skin, liver, and kidney, revealed no positive staining of hair shafts; the correlation between stain intensity and dose group was poor. These findings indicate that dietary exposure for 4 months to 0.28 and 0.8 mg Se/kg in the form of selenomethionine and to 0.8 mg Se/kg in the form of sodium selenite reproduces in some cattle mild (subclinical) to severe (clinical) forms of alkali disease. No significant neurological, renal, or hepatic lesions developed, supporting the contention that blind staggers is caused by factors other than excessive dietary selenium.

Hoof horn abnormalities in Lipizzaner horses and the effect of dietary biotin on macroscopic aspects of hoof horn quality

This study involved a macroscopic evaluation of hoof quality in 152 Lipizzaner horses (130 from Austria and 22 from other countries) and a controlled double blind trial of the effects of biotin on hoof horn growth and quality over 19 months in 42 stallions from the Spanish Riding School (SRS) in Vienna. Using a grading system that incorporated evaluation of horn wall, white line, sole and frog, the macroscopic study revealed the following: 90% of the Austrian Lipizzaners had soft white lines and crumbling, fissured horn at the bearing border of the walls; 39% of the stallions of the SRS, > 4-years-old, had medium to severe hoof horn changes. Daily administration of 20 mg biotin to a test group of horses (n = 26) and a placebo to a control group (n = 16) showed that after 9 months the test group had significantly improved compared to the beginning of the trial and the placebo group (P < 0.01). In the test group, further improvement was observed during the following 5 months and, subsequently, the same good level of hoof condition was maintained over 3 further years of observation. Growth rate of the horn wall was equal in the biotin and placebo group, being 7 mm/28 days, giving a wall renewal period of 11 months. Mean plasma biotin level of untreated horses was 350 ng/l; plasma levels of biotin supplemented horses were > 1000 ng/l. It was concluded that continuous dietary supplementation with biotin at a daily dose of 20 mg is indicated to improve and maintain hoof horn quality in horses with less than optimum quality hoof.

Histological and physical assessment of poor hoof horn quality in Lipizzaner horses and a therapeutic trial with biotin and a placebo

This paper represents the second part of a study searching for factors which could be responsible for an inferior hoof horn quality of the Lipizzaner horses of the Viennese Spanish Riding School (SRS) noticed in the late 1980s. It includes an evaluation of a treatment with biotin and 42 Lipizzaner horses were tested in a double blind study. The following parameters were evaluated: 1) the histology of the hoof horn in samples from the bearing border 2) the tensile strength of the coronary horn in bearing border samples and 3) the influence of biotin upon the histological changes and the tensile strength after application of 20 mg/day of biotin during 38 months. The histological alterations of bearing border specimens were assessed by use of a grading system (Grade 0 = unchanged; Grade 1 = slight changes; Grade 2 = moderate changes; Grade 3 = severe changes). Initially more than two thirds of the horses showed moderate to severe changes: microcracks visible in the transition from the middle to the inner zone of the coronary horn; separation of the sole from the coronary horn in the region within the white zone. The tensile strength of the coronary horn, with a mean of 39 N/mm2, was 13 N/mm2 lower compared with the unchanged hooves of 10 Warmblood horses, which were investigated by Küng (1991). After 19 months of biotin treatment, the horn quality showed a small but significant improvement. This could be shown by comparing the histological tissue structure before and after treatment, as well as treated animals vs. a placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)

Symmetrical lupoid onychodystrophy in dogs: a retrospective analysis of 18 cases (1989-1993)

A unique, symmetrical onychodystrophy is described in 18 dogs. A rather sudden onset of onychomadesis is followed by chronic onychodystrophy affecting all claws. Pain and lameness are recognized in half of the patients, but the dogs are healthy otherwise. Histopathologically, this disorder is characterized by hydropic and lichenoid interface dermatitis. Nine dogs were treated with a commercial, fatty-acid supplement and had good-to-excellent responses. Due to the clinicopathological characteristics of this disorder, the authors propose the name "symmetrical lupoid onychodystrophy."

Influence of the beta-agonist salbutamol on claw horn lesions and walking soundness in finishing pigs

The effects of feeding the beta-adrenergic agonist salbutamol to pigs at levels between 0.5 and 5.0 mg/kg feed for different periods were studied in six experiments. The feet and ability to walk of pigs weighing 30 to 100 kg were examined at intervals. False sand-crack, white-line and heel erosion lesions were classified as mild or severe, and corns and wall haemorrhages were also recorded. At each examination the pig was given a grade for the overall severity of its foot lesions. Salbutamol fed at 1.0 to 5.0 mg/kg feed, for as little as 21 to 28 days, increased the frequency (P < 0.05 to 0.001) and often the severity (P < 0.05) of the foot lesions, the higher doses tending to produce more severe lesions, and the overall foot grades deteriorated (P < 0.001). The effects on both sexes were similar. No changes were observed when 0.5 mg/kg was fed for 56 days. Despite the severity of many of the foot lesions, the pigs became lame in only one experiment. Electron microscopy indicated that salbutamol was interfering with horn production, but light microscopy revealed no changes in skin sections. These findings suggested that salbutamol was not directly affecting the function of keratinocytes. Supplementing the diet of the pigs with biotin and methionine did not delay, or prevent, the effects of salbutamol.

Effect of photoperiod, testosterone, and estradiol on body mass, bifid claw size, and pelage color in collared lemmings (Dicrostonyx groenlandicus)

Collared lemmings undergo several photoperiod-mediated seasonal physiological changes. When exposed to short photoperiod, lemmings increase in size, develop a bifid claw, and molt to a white pelage. Previous data indicate that body mass, claw size, and pelage color are influenced by hormones of testicular origin, suggesting that, on a seasonal basis, changes in production of, or sensitivity to, testicular hormones may play a role in the development of the phenotype characteristic of the ambient photoperiod. The present study was designed to determine if the active testicular hormone(s) is testosterone (T) and/or estradiol (E2) and if seasonally changing physiological traits in female lemmings are also influenced by gonadal status. Fifty-day-old lemmings, reared in 22L:2D (long day), 16L:8D (intermediate day), or 8L:16D (short day), were either gonadectomized or sham operated and given either empty Silastic implants or implants containing T (4 or 10 mm; castrated males), E2 (4 mm undiluted or diluted 1:4 with cholesterol; ovariectomized females), the aromatase inhibitor ATD (androsta-1,4,6-triene-3,17-dione; 2 x 20 mm; intact animals of both sexes), or ATD plus a 10-mm T implant (castrated males). After a 6-week treatment period, changes in body mass, bifid claw width, pelage color stage, and serum prolactin (PRL) were assessed. The effects of gonadectomy and steroid treatment depended upon photoperiod. Whereas gonadectomy increased mass gained by both sexes under intermediate and short day, under long day only females showed the positive mass response to gonadectomy. Treatment with T and E2 reversed the effect of gonadectomy on body mass under intermediate day and decreased the amount of mass gained under short day. Treatment with ATD (males) and E2 (females) indicated that E2 was the hormone responsible for the tonic, inhibitory effect of the gonads on body mass in both sexes. Claw size was most sensitive to steroid manipulation in animals housed in long day, in which all treatments had a negative influence. Gonadectomy under short day resulted in the development of a whiter pelage in both sexes. The effect of gonadectomy on pelage in female lemmings, and its reversal by E2 treatment, may have been partially due to alteration of serum PRL.

Effect of dietary biotin supplement on equine hoof horn growth rate and hardness

Over a 10-month period, 24 randomly selected riding horses were fed various amounts of biotin. Statistically significant improvements in growth rates and hardness of hooves were produced by biotin supplementation. Greater growth rates and hardness were achieved at a daily dose of 15 mg than at 7.5 mg. Increased hoof hardness was greatest in the hoof quarters and toe. No ring formation occurred in hooves of horses fed biotin intermittently.

Efficacy of dietary sodium selenite and calcium selenite provided in the diet at approved, marginally toxic, and toxic levels to growing swine

A 2 x 3 factorial experiment conducted in three replicates of a randomized complete block design compared the effects of calcium selenite and sodium selenite at three different levels of Se (.3, 5, or 15 ppm) in the diets of growing swine on performance and tissue Se concentrations. Ninety pigs averaging 12.5 kg of BW were given ad libitum access to corn-soybean meal diets fortified with one of the treatment Se sources and dietary levels for a 35-d experimental period. Growth and feed intake were similar in pigs fed .3 and 5 ppm of Se but were lower (P less than .01) in those fed 15 ppm from either Se source. Serum Se increased (P less than .01) as dietary Se level increased with no difference between Se sources at each dietary Se level. Liver, kidney, and longissimus muscle Se concentrations increased (P less than .01) as the dietary level of Se increased and were similar when either Se sources was provided. These results indicate that calcium selenite was as effective as sodium selenite using the measurement criteria of growth, serum, and tissue Se concentrations and glutathione peroxidase activities of growing swine when fed at approved, marginally toxic, and toxic dietary Se levels.

Effects of supplemental biotin during gestation and lactation on reproductive performance of sows: a cooperative study

A cooperative experiment to evaluate biotin addition to sow diets was conducted at three research stations using 303 litters. Primiparous and multiparous sows (overall average parity 2.8) were fed a 14% CP corn-soybean meal diet (140 micrograms/kg biotin), with or without supplemental biotin (330 micrograms added biotin per kg feed), throughout gestation and lactation. As many sows as possible were fed their respective diets through three successive parities. During gestation, sows were given from 1.82 to 2.27 kg of feed per day, depending on environmental conditions; during lactation sows had ad libitum access to feed. Supplemental biotin had no effect (P greater than .35) on sow weights at breeding, at d 109 of gestation, at farrowing or at weaning. No differences were found in litter size at birth (P greater than .18), but at d 21 of lactation, sows fed the diet containing supplemental biotin had larger litters than sows fed the unsupplemented diet (9.4 vs 8.7 pigs, respectively; P = .01). Pig weights at birth and d 21 of lactation were not affected (P greater than .20) by dietary treatment. Biotin supplementation did not affect (P greater than .28) the length of the interval from weaning to estrus. No evidence was found that feet cracks or bruises were reduced by biotin supplementation. The results indicate that biotin supplementation of a corn-soybean meal diet during gestation and lactation increased the number of pigs at d 21 of lactation, but it did not decrease the incidence of foot lesions.

Effect of dietary biotin supplementation on sow reproductive performance and soundness and pig growth and mortality

A 3-yr study was conducted to evaluate the effect of dietary biotin supplementation on the reproductive performance of 90 sows and gilts, and on the pre-weaning growth and mortality of 223 litters. Corn-soybean meal-based diets supplemented with either 0 or 440 micrograms/kg d-biotin were fed to sows throughout their reproductive cycle. Biotin supplementation had no beneficial effect (P greater than .10) on 107-d sow weight, sow weight at weaning, weaning to estrus interval, foot lesion score, hair loss score, structural soundness score, number of pigs born, number and percentage of pigs born alive or number and percentage of pigs alive at 21 d of age. Biotin supplementation had no effect (P greater than .10) on pig growth or mortality to 21 d of age. These data do not support the concept that biotin supplementation of sow diets is needed.

Rate of claw horn growth and wear in biotin-supplemented and non-supplemented pigs

The growth and wear rate of claw horn was measured in 42 commercial hybrid pigs. Half received a ration supplemented with 1 mg d-biotin/kg food daily, while the others acted as controls. The start weights of three replicates of 10 pigs averaged 25 kg and their mean finishing weight was 85 kg. Twelve pigs averaged 18 kg at the start and 118 kg at the end of the experiment. No differences in horn growth and wear rates were found between the biotin-supplemented pigs and the controls, or between the front and hind claws, although horn growth and wear both decreased with age. Claw horn grew at an average of 10 mm/28 days in the pigs taken from 25 to 85 kg bodyweight and at 11 mm/28 days in the pigs taken from 18 to 118 kg. The mean rate of wear of claw horn was 6 mm/28 days.

[Detrimental sequelae of a sodium hydroxide standing foot bath for cattle for the control of Italian interdigital dermatitis]

Eighteen cases of severe damage to digits of cattle are reported. These animals had been standing in a footbath containing sodium hydroxide and sodium hypochlorite for the treatment of digital dermatitis. The lesions on the digit and their healing are discussed in this paper.

Nail loss and footpad erosions in beagle dogs given BW 134U, a nucleoside analog

The oral administration of BW 134U to Beagle dogs in a 1-month study was associated with lameness, footpad erosions, and nail loss. Groups of dogs received 60, 120, and 240 mg/kg/day. Compound-related effects were observed in the high dose group and only during the postdose period. Light microscopy revealed prominent cell maturation or radiomimetic defects in the stratum germinativum of the distal phalanges and footpads. The mechanism by which BW 134U produced these cell maturation defects is unknown. There were no signs of adverse effects in other keratin-producing or keratin-containing tissues.

Effect of a dietary supplement of biotin on pig hoof horn strength and hardness

Supplementary biotin (1 mg d-biotin/kg feed) increased the compressive strength of the mid-abaxial sidewall region of pig's hoof from 9.3 (+/- 0.5) X 10(6) N/m2 to 12.0 (+/- 0.5) X 10(6) N/m2 (P less than 0.05). It also increased the hardness of this region, measured on the Shore A and D hardness scales (P less than 0.05). The leading edge of the hoof wall was significantly stronger than the sidewall (P less than 0.001) with a compressive strength of 14.5 (+/- 0.7) X 10(6) N/m2. This site showed no significant improvement in compressive strength or hardness in response to biotin. Biotin also produced a significant decrease in the hardness of the heel bulb on the Shore A scale (P less than 0.05). There would therefore appear to be a rational biomechanical basis for the finding by others that biotin reduces lameness. The Shore A and D hardness testers are sensitive to the improvement produced by biotin and may be useful as small, hand-held hoof testing devices for use in field conditions by the practising veterinarian.

Effect of methionine hydroxy analog supplementation on dairy cattle hoof growth and composition

Fifty lactating Holstein cows were assigned randomly to one of two treatments, control and control plus approximately 30 g methionine hydroxy analog, and confined on concrete for 11 mo. The control diet consisted of sorghum silage and concentrate fed as a blended ration. Sulfur contents of dry matter were .12% and .16% for control and methionine hydroxy analog rations. Hoof growth and hardness were measured on front and rear right abaxial claws in the dorsal and lateral regions. Hoof growth rates were measured for four periods; summer-fall, fall-winter, winter-spring, and spring-summer, each 70 to 90 days. Hooves of cows fed methionine hydroxy analog grew faster than those of control cows during spring-summer in all regions. Variations of growth rates of hooves were seasonal and tended to follow variations in daily photoperiod. Wear rates were not affected significantly by treatment. Hooves of cows fed methionine hydroxy analog were softer in the top dorsal region at the end of winter-spring and in the dorsal toe region at the end of spring-summer. All other locations were not affected significantly by treatment. The toe region was harder than the top of the hoof. Cows fed methionine hydroxy analog had less cysteine and proline in hoof than control cows and greater percentages of methionine lysine, tyrosine, and glutamic acid. These results suggest that a decrease of disulfide bonding occurred in the hoof tissue of cows fed methionine hydroxy analog. Cows fed methionine hydroxy analog produced more actual milk, milk fat, and 4% fat-corrected milk during 180 days than did control cows.