Experimental immunization of calves against Anaplasma marginale infection: observations on the use of living A. centrale and A. marginale

Groups of Bos indicus cross calves aged 6 months were immunized with Anaplasma centrale or A. marginale. All animals were challenged with 10¹⁰A. marginale 7 months later. Groups immunized with A. marginale were refractory to challenge, whereas only a portion of the animals vaccinated with A. centrale were immune. Following immunization, animals that had experienced a good primary antibody response as measured by a complement fixation test, a marked reduction in packed cell volume, and a high parasitaemia, resisted a subsequent challenge with A. marginale. Resistance was characterised by a weak secondary antibody response and the absence of A. marginale in blood films     

Clinical features and treatment of renal tubular acidosis in two horses

Two horses were admitted separately for evaluation and treatment of profound hyperchloremic metabolic acidosis without azotemia. One, an 11-year-old Quarter Horse mare, had been depressed and ataxic for 2 days. The other, a 2-year-old Quarter Horse colt, had a 6-week history of depression, anorexia, and weight loss. Both horses responded to fluid and electrolyte therapy, but required daily oral administration of sodium bicarbonate for maintenance. In each case, the diagnosis was renal tubular acidosis.     

Influence of concentration, duration and route of administration of melatonin on reproductive performance of spring-mated polypay and polypay-cross ewes

The effects of exogenous melatonin on reproductive performance of 737 Polypay and Polypay-cross ewes were evaluated during a late March and April breeding period. Different concentrations (2 or 10 mg) routes of administration (fed vs implanted) and durations of administration (20 or 40 d before breeding) were studied. Estrus was synchronized in all ewes using 60 mg medroxyprogesterone acetate (MAP) in a vaginal pessary. Number of mature ewes lambing/ewe present at lambing was increased (P less than .05) nearly 20% by implanting for 40 d with melatonin (75%) or by feeding either 2 (72%) or 10 mg (73%) melatonin for 40 d before spring breeding compared with untreated control ewes (54%) or ewes implanted for only 20 d before breeding (58%). Date of lambing, number of lambs born/ewes lambing and number of lambs born alive/ewe lambing were not altered significantly by treatments. Number of yearling ewes (n = 166 for ewes 1.5 yr old at lambing time) lambing/ewe present at lambing was lower (P less than .01; 26%) than that of mature ewes (n = 381, greater than or equal to 2.0 yr; 68%). We concluded that feeding 2 or 10 mg melatonin or implanting melatonin for 40 d enhanced reproductive performance and effectively overcame the restrictions of seasonality of breeding in mature ewes. In yearling ewes, 10 mg melatonin increased the number of ewes lambing.     

The effect of transportation on the immune status of Bos indicus steers

This study investigated the effect of 72 h of road transport on the immune status of Bos indicus steers (n = 10; age = 15 to 18 mo). Total and differential leukocyte numbers and lymphocyte function were determined at 2 d before transport (-48 h), immediately after 72 h of transport (72 h), and 6 d after transport (216 h). Phytohemagglutinin (PHA)-stimulated lymphocyte proliferation, interferon-gamma production, and tetanus-toxoid specific antibody levels were determined. Total leukocyte and eosinophil numbers showed a transient decrease at 72 h (immediately after transport; P < 0.05) and returned to baseline values by 6 d after transport. Lymphocyte numbers and antibody titers were unaffected by transportation. The PHA-stimulated lymphocyte proliferation decreased (P < 0.05) at 72 h and returned to baseline levels 6 d after transport. This study demonstrated that transportation of mature Bos indicus steers caused transient decreases in leukocyte numbers and lymphocyte function, although all measures recovered by 6 d after transport. Therefore, Bos indicus cattle may be vulnerable to infection during this period.     

Bacterial diskospondylitis associated with posterior paresis/paralysis in North American farmed mink (Mustela vison)

Posterior paresis/paralysis in farmed mink is responsible for significant morbidity and mortality, with individual farms reporting the loss of as many as 700 animals each year. Although this disease has been recognized by North American mink farmers for approximately 40 years, there are few published reports focusing on this entity. The objective of this study was to investigate the etiology and pathogenesis of the disease. Complete necropsy examinations were done on 40 clinically affected mink, ranging from 7 to 10 weeks of age, and on three normal animals in the same age range from two mink farms. Thirty-two of the 40 clinically affected animals had an isolated vertebral lesion characterized by bone lysis and proliferation that usually was centered on an intervertebral disk space in the midthoracic area. An inflammatory reaction, composed primarily of neutrophils, was present within the vertebral sections in 25 of the 40 affected animals (62.5%), and the presence of gram-positive cocci was confirmed in 8 of 10 animals (80%) in which bacterial organisms were observed histologically. Bacterial cultures from 15 affected animals yielded Streptococcus sp. from the intervertebral disk space in 13 of 15 (86.7%) animals and from heart blood in 6 of 8 (75%). A farm visit revealed no history or evidence of traumatic wounds as a source of infection in these animals, and the diet appeared to be adequate for skeletal development. We conclude that posterior paresis/paralysis in farmed mink is associated with bacterial diskospondylitis, likely occurring secondary to bacteremia/septicemia.