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Summary:

An epidemiologic study investigating the prevalence of lameness in lactating dairy cows was performed in 17 dairy herds in Minnesota and Wisconsin. The mean herd size was 50 cows. Cows from 14 herds were housed in stanchions or tie stalls, and cows from 3 herds in free stalls or dry lot. During visits to each farm in the summer and subsequent spring, 2 investigators simultaneously but independently evaluated the ambulation of lactating cows by use of a standardized scoring system. The lameness scoring system was reliable at the 2 visits, with 92.7 and 91.3% agreement between the 2 observers and κ coefficients of 0.60.

The prevalence of lameness detected by the investigators (“clinical” lameness) was 13.7% (117/853) in summer and 16.7% (134/801) in spring in lactating dairy cows. These prevalences were 2.5 times higher than those estimated by the herd managers. Parity was significantly (P ≤ 0.03) associated with lameness, with higher prevalence of clinical lameness found in cows of higher parity.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To characterize the response of equine jejunal smooth muscle to adrenergic and cholinergic mediators.

Design

Evaluation of myogenic responses, using an in vitro model.

Sample Population

Intestinal tissues were obtained from horses without gastrointestinal tract disorders or systemic disease.

Procedure

Baseline myogenic tone and amplitude and frequency of contraction were determined for suspended jejunal muscle strips. The level of adrenergic and cholinergic regulation was assessed, using atropine and adrenoceptor antagonists. The response of the muscles to norepinephrine was characterized, using adrenergic blockade and α- and β-agonists.

Results

Adrenergic and cholinergic blockade had minimal effect on baseline myogenic activity. However, α1- and β2-agonists induced significant (P < 0.05) decreases in the amplitude and frequency of contraction. Surprisingly, α2-agonists caused an increase in the contraction amplitude of longitudinal muscle fibers (neurogenic in origin). Change in circular muscle activity was not induced by α2-agonists. Norepinephrine induced a similar selective response and was inhibited by yohimbine.

Conclusions

Baseline jejunal activity appears to be myogenic in origin and can function independently of sympathetic and parasympathetic input. However, intestinal smooth muscle can be affected by adrenergic agonists and potentially by increased concentrations of circulating catecholamines. Norepinephrine may act by altering the activity of other neurotransmitters. Differing responses between circular and longitudinal muscle fibers indicates a need to evaluate both components.

Clinical Relevance

Selective α2-agonists may be potentially useful for motility modification of the equine jejunum. Therapeutic use of adrenergic blockade will be effective only in cases of increased adrenergic stimulation. (Am J Vet Res 1996;57:884–890)

Free access
in American Journal of Veterinary Research

SUMMARY

A matched case-control study design was used to assess the effects of long-term administration of a prolonged release formulation of bovine somatotropin (sometribove) on clinical lameness and limb lesions in dairy cows. Cows treated with sometribove for at least 2 lactations (cases) and nontreated dairy cows matched by herd, parity, age, and stage of lactation (controls) in 8 herds were evaluated for clinical lameness (as assessed by gait abnormality) and limb lesions by 2 observers, using a standardized scoring procedure at a single herd visit. Although a high proportion of the study cows were clinically lame (43%), an association was not detected between chronic administration of sometribove and prevalent lameness. Of 21 types of limb lesions identified, 2 were positively associated and 2 were negatively associated with long-term sometribove use. Superficial laceration of the tarsus (odds ratio [or] = 2.1) and superficial swelling of the metatarsophalangeal joint (or = 4.5) were positively associated with sometribove treatment, whereas femoral lesions (or = 0.2) and superficial lacerations of the femur (or = 0.14) were negatively associated with sometribove treatment.

Free access
in American Journal of Veterinary Research

SUMMARY

Results of an elisa, indirect fluorescent antibody (ifa) test, and immunoblot analysis (western blotting) for antibody to Borrelia burgdorferi in a sample of 216 lactating dairy cows were compared. The microscopic microtitration agglutination test for antibody to 6 serovars of Leptospira interrogans was also performed to evaluate possible cross-reactivity between B burgdorferi and L interrogans. Using western blotting as the standard test against which the elisa and ifa test were compared, the elisa had greater sensitivity (50% in summer and 38% in spring) with similar specificity (83 and 82%), compared with the ifa test (sensitivity, 6 and 5%; specificity, 90 and 83%). In addition, seropositivity to B burgdorferi, using the elisa, was not found to be associated with seropositivity to L interrogans serovars.

A matched case-control study evaluating the association between clinical lameness and antibody to B burgdorferi was performed in lactating dairy cows of 17 Minnesota and Wisconsin herds. Sera from case and control cows matched by herd, parity, and stage of lactation were evaluated, using an elisa for B burgdorferi antibody during 2 seasons. High B burgdorferi antibody values were associated with clinical lameness in dairy cows (P = 0.006 in summer and P = 0.04 in spring).

Free access
in American Journal of Veterinary Research

SUMMARY

A mucosal lesion was created in the center of each test sinus of 6 mature, healthy, nonlactating Holstein cows by resecting a circumferential band of mucosa. Each lesion was then treated by implantation of strip grafts of autogenous oral mucosa, temporary silastic tube implant, or a combination of strip grafts and temporary silastic tube implant. All teats were evaluated for patency 6 weeks after treatment, and tube implants were removed through a second thelotomy incision. All teats were reevaluated for gross and radiographic patency 12 weeks after treatment, and teats were collected for histologic evaluation of lesions. All 4 teats treated with grafts only were obstructed at 6 and 12 weeks after treatment. Incomplete coverage of the lesion with mucosa was observed in all 4 teats. The major source of obstruction was proliferation of epithelium and keratin into the lumen. All 8 teats treated with temporary silastic tube implants alone were patent at 6 weeks after treatment, but were obstructed at 12 weeks after treatment. Foci of mucosa at the lesion site were detected in only 2 of the 8 teats. Obstruction resulted from proliferation of granulation tissue into the lumen. All 12 teats treated with grafts and a temporary tube implant were patent at 6 weeks after treatment and 11 of 12 were patent at 12 weeks after treatment, although marked luminal narrowing was evident in 9 of 11 teats. Partial to complete coverage of the lesion with mucosa was seen in all teats. Proliferative granulation tissue, epithelium, and keratin contributed to luminal narrowing in 10 of 11 patent teats. Bacteriologic culture of quarters from 6 of the 11 teats patent at the final evaluation yielded pathogens.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the major neurotransmitters that regulate contractile activity in the jejunum of horses.

Sample Population

Jejunal specimens from 65 horses without gastrointestinal tract lesions.

Procedure

Jejunal smooth muscle strips, oriented in the plane of the circular or longitudinal muscular layer, were suspended isometrically in muscle baths. Neurotransmitter release was induced by electrical field stimulation (EFS) delivered at 30 and 70 V intensities and at various frequencies on muscle strips maintained at low or high muscle tone. To detect residual nonadrenergic-noncholinergic neurotransmission, the response of muscle to EFS in the presence of adrenergic and cholinergic blockade was compared with the response in the presence of tetrodotoxin.

Results

Atropine (ATR) decreased the contractile response of muscle strips to EFS under most conditions. However, ATR increased the contractile response of high-tone circular muscle. Adrenergic blockade generally increased the muscle responses to 30 V EFS and in high-tone longitudinal muscle but decreased contractile responses in high-tone circular muscle. Tetrodotoxin significantly altered the responses to EFS, compared with adrenergic and cholinergic receptor blockade.

Conclusions

Acetylcholine and norepinephrine appear to be important neurotransmitters regulating smooth muscle contractility in the equine jejunum. They induce contraction and relaxation, respectively, in most muscle preparations, although they may cause opposite effects under certain conditions. In addition, nonadrenergic-noncholinergic excitatory and inhibitory influences were detected.

Clinical Relevance

Acetylcholine or norepinephrine release within the myenteric plexus of horses may alter gastrointestinal motility. (Am J Vet Res 1999;60:898–904)

Free access
in American Journal of Veterinary Research