Andrew H. Parks

Effects of diet on rumen proliferation and fecal shedding of Escherichia coli O157:H7 in calves.

Calves inoculated with Escherichia coli O157:H7 and fed either a high-roughage or high-concentrate diet were evaluated for rumen proliferation and fecal shedding of E. coli O157:H7. Calves fed the high-roughage diet had lower mean rumen volatile fatty acid concentrations and higher rumen pH values than did calves fed the high-concentrate diet. Despite these differences in rumen conditions, the calves fed the high-roughage diet did not have greater rumen populations of E. coli O157: H7 and did not exhibit increased or longer fecal shedding compared with the calves fed the high-concentrate diet. Two calves shedding the highest mean concentrations of E. coli O157:H7 were both fed the high-concentrate diet. There was a significant (P < 0.05) positive correlation between fecal shedding and rumen volatile fatty acid concentration in calves fed a high-concentrate diet. The effects of diet on E. coli O157:H7 proliferation and acid resistance were investigated using an in vitro rumen fermentation system. Rumen fluid collected from steers fed a high-roughage diet, but not from steers fed a high-concentrate diet, supported the proliferation of E. coli O157:H7. Rumen fluid from steers fed a high-concentrate diet rapidly induced acid resistance in E. coli O157:H7. The impact of diet on fecal shedding of E. coli O157:H7 is still unclear and may depend on dietary effects on fermentation in the colon and on diet-induced changes in the resident microflora. However, rapid development of acid tolerance by E. coli O157:H7 in the rumens of calves fed high-concentrate diets, allowing larger populations to survive passage through the acidic abomasum to proliferate in the colon, may be one factor that influences fecal shedding in cattle on feed.

Fecal Shedding and Rumen Growth of Escherichia coli O157:H7 in Fasted Calves

Nine weaned calves aged from 8 to 12 weeks were fitted with rumen cannulas and were inoculated by cannula with 10(10) CFU of a five-strain mixture of nalidixic acid-resistant Escherichia coli O157:H7. Six calves were fasted for 48 h on days 15 and 16 and days 22 and 23 after inoculation. Samples of rumen contents and feces were obtained daily to enumerate E. coli O157:H7 populations and to determine rumen volatile fatty acid (VFA) concentrations and rumen pH. Fasting resulted in a marked decrease in rumen VFA concentrations from a mean of 135 mmol/liter before the fast to a mean of 35 mmol/liter during the second day of the fast. However, there was no correlation between daily VFA concentration and daily rumen or fecal numbers of E. coli O157:H7 in any of the calves. Fasting generally had no significant effect on the rumen or fecal numbers of E. coli O157:H7. The exception was a single fasted calf that experienced a 3-log(10) CFU/g increase in fecal shedding during and after the first fast. Despite the consistent changes in VFA concentrations in fasted calves, the fluctuations in rumen numbers of E. coli O157:H7 in the rumen of fasted calves were minimal. At the end of the experiment, E. coli O157:H7 was detected in either the rumen or omasum in two of three control calves at necropsy and in either the rumen or reticulum in five of six fasted calves. E. coli O157:H7 was detected in the colon in two of three control calves and in six of six fasted calves at necropsy. These results suggest that in cattle already shedding E. coli O157:H7, feed withdrawal and the associated changes in rumen pH and VFA concentrations have little effect on fecal shedding and rumen proliferation of E. coli O157:H7.

Form and function of the equine digit.

The list of possible diagnoses derived from matching anatomic structures or tissues to pathologic processes is inevitably broad in nature. Understanding and observation of distal limb function, conformation, and balance is the basis of identifying where the greatest abnormal stresses within the distal limb are likely to occur. This is key to focusing the diagnostic process and, in some instances, to treating the horse when a definitive diagnosis cannot be achieved.

Chronic laminitis: current treatment strategies.

Laminitis is divided into four different phases: developmental, acute, subacute, and chronic. The focus of this article is on treating the laminitic horse after the cessation of therapy for the acute phase, that is, usually 2 to 4 weeks after the onset of clinical signs.

Treatment of Acute Laminitis: Supportive Therapy

Over the last decade, both the farriery and veterinary professions have greatly increased their collective experience and understanding of the treatment of acute laminitis. Many horses that would have not been considered candidates for treatment 10 to 15 years ago are now saved, and some progress to successful careers as athletes. Unfortunately, the difficulties over prediction of the course of the disease persist, which continues to complicate treatment decisions. By its nature, supportive therapy is designed to make the horse more comfortable and limit further laminar injury by countering adverse biomechanical forces. Therefore, the success of treatment depends on the degree of instability between the distal phalanx and the hoof when treatment is started as well as the effectiveness of medical and supportive therapy.

Therapeutic Farriery: One Veterinarian's Perspective

Therapeutic shoeing is best directed at a specific diagnosis, but in the absence of a specific diagnosis, it is frequently directed at a symptom. There are only so many ways to modify the function of the foot with trimming and shoeing. The design of a horse shoe may often be modified to improve one aspect of foot function. Modifying a horse shoe to improve one aspect of foot function almost invariably impacts another aspect of foot function. The application of horse shoes may be based on a specific diagnosis or directed at a symptom. The application of shoeing principles is best approached using theoretical reasoning based on the research data that are available and experience.

Examination of the Equine Foot

There are excellent journal articles and book chapters that describe the examination of the foot, some of which are listed as references. Reviewing them reveals that each clinician performs their examination in their own style, and they emphasize different aspects of the examination; however, they all have a method, and all describe an effective process to diagnose as effectively as possible the various conditions that affect the equine foot. This article describes the author’s approach to examination of the foot, which is a synthesis of formal education received, personal experience, and experience of others. It is a reductionist rather than procedural approach. The majority of disease processes originating in the foot that cause lameness are associated with inflammation, usually related to trauma or infection. Disease processes associated with a marked focus of inflammation, typically associated with acute onset of lameness, are most likely to be identified with a basic examination, whereas disease processes associated with subtle symptoms and longer duration may require much more extensive examination of the limb and ancillary diagnostic tests. Furthermore, even the best examination in conjunction with ancillary diagnostic tests may not always obtain a definitive diagnosis, but the information gained may suggest an approach for symptomatic treatment. The latter is particularly important when access to advanced diagnostic technology, such as magnetic resonance imaging, is limited. Therefore, the following discussion is divided into two parts, the basic examination and a more detailed examination. The detailed examination is further divided into three main sections that provide different types of information. All examinations begin by gathering the presenting complaint, signalment, and history. With most foot problems, the presenting complaint is lameness. However, presenting complaint may also be the appearance of the foot. The signalment for any horse does not give specific information about the presenting complaint, but it does contain risk factors for certain conditions, which must then be correlated with information obtained from the history and physical examination. There are three main time points of importance in history taking: the date of the examination, the date that the problem was first noticed, and the date that the owner first knew/owned the horse. The second date gives an indication of the duration of the problem, and the length of time between the second and third dates gives the clinician an indication of how much history before this problem is known; this may lead to further enquiry about this time. No two sets of questions asked during a history taking are the same, because so many questions are pred-