Gonadotrophin-releasing hormone treatment in cattle: a meta-analysis of the effects on conception at the time of insemination

SUMMARY Data from 40 trials described in 27 published papers were analysed by meta-analysis (pooling of data from numerous trials into a single analysis) to evaluate the effects of injecting gonadotrophin-releasing hormone (GnRH) In cattle at the time of Insemination on the risk of pregnancy. A total of 19 019 cows were involved In these studies. Analyses were stratified by trial and by the effects of dose of GnRH, type of GnRH and Insemination number (first, second or third and greater). Mantel-Haenszel analysis revealed that use of GnRH at Insemination significantly Increased the overall risk of pregnancy by 12.5% In treated cows (P < 0.05). However, Increases In risk of pregnancy were greatest (22.5%) when repeat breeders were treated. Results for use of GnRH or analogue at first service were similar, with Increased risks of pregnancy in treated cows of 5.2 and 8.0%, respectively. The risk of pregnancy tended to be higher (11.1%) when the dose of GnRH was 250 μg and when used at second Insemination (9.9%). The analyses demonstrated that while treatment at Insemination with GnRH and GnRH analogues Increased conception rates In dairy cattle, some variation In study results was attributable to the number of Inseminations after calving at which GnRH Is administered. Further efforts should be made to determine characteristics of populations of cows that have good fertility responses to GnRH and to determine the mode of action of GnRH in Increasing fertility. Meta-analysis proved to be a useful technique for evaluating the apparently conflicting results from trials and in evaluating the effect of factors such as Insemination number, dose and type of GnRH on responses to treatment.     

Hyperthyroidism due to an intrathoracic tumour in a dog with test results suggesting hyperadrenocorticism

The elevated urinary corticoid/creatinine ratios of an 11-year-old Jack Russell terrier with polyuria were suppressible in a high-dose dexamethasone suppression test, which was suggestive of pituitary-dependent hyperadrenocorticism. The absence of physical and routine-laboratory changes compatible with hyperadrenocorticism and the relatively high plasma thyroxine concentration were the impetus for additional studies of thyroid and adrenocortical functions. A high plasma thyroxine concentration (62 nmol/l; 5.0 microg/100 ml) suggested the presence of hyperthyroidism. Radiography, (99m)TcO(4) (-) scintigraphy, ultrasonography, computed tomography and cytology revealed a hyperfunctioning intrathoracic thyroid tumour. In the low-dose dexamethasone suppression test, the plasma cortisol concentration exceeded the reference value of 40 nmol/l (1.4 microg/100 ml) at eight hours after dexamethasone administration (0.01 mg/kg intravenously), a test result compatible with hyperadrenocorticism. In conclusion, this report represents the first case of a dog with an autonomously hyperfunctioning thyroid tumour in the thorax. The elevated urinary corticoid excretion and the positive low-dose dexamethasone suppression test may be explained by alterations in cortisol metabolism, the stress of the hyperthyroid state or both.     

Effects of diets with different calcium and phosphorus contents on the skeletal development and blood chemistry of growing great danes

The skeletal development of three groups of great dane dogs, fed a diet composed according to the published nutritional requirements for dogs (controls) or with increased calcium or calcium and phosphorus content, was examined radiographically, histologically and biochemically. The diets were fed from the time the dogs first began eating food in addition to their dam's milk, until they were 17 weeks old. Thereafter, the calcium and phosphorus intakes of the dogs in the high calcium groups were normalised for a further 10 weeks. The dogs fed the high calcium diet without a proportionally high phosphorus intake became hypercalcaemic and hypophosphataemic, and had severe disturbances in skeletal development, growth, and mineralisation which were typical for rickets. After their calcium intake was normalised the lesions of rickets resolved but osteochondrotic lesions became apparent. The dogs fed the high calcium and phosphorus diet became slightly hypophosphataemic, their growth was retarded, and they had disturbances in skeletal development resembling osteochondrosis, which had only partly resolved after 10 weeks on the normal calcium and phosphorus diet.     

X-ray-computed tomography, nephrotomography, and ultrasonography of the adrenal glands of healthy dogs

X-ray-computed tomography (CT), nephrotomography, and ultrasonography were performed in 10 clinically healthy dogs (weighing 14 to 33 kg) to visualize the adrenal glands. In all 10 dogs, CT enabled visualization of both adrenal glands. Cross-sectional diameter was measured accurately. The size and shape of CT sections of the adrenal glands varied widely because of individual differences in the actual size and shape of the adrenal glands and because of their position in the plane of the CT scans. In 5 dogs, nephrotomography enabled visualization of 1 or both adrenal glands as oblong craniocaudal-directed densities in the craniodorsal portion of the abdomen. In 7 dogs, transverse ultrasonography enabled visualization of 1 or both adrenal glands as round or oval hypoechoic structures in the surrounding hyperechoic fat.     

Assessment of survey radiography and comparison with x-ray computed tomography for detection of hyperfunctioning adrenocortical tumors in dogs

Results of abdominal survey radiography and x-ray computed tomography (CT) were compared in 13 dogs with hyperadrenocorticism histologically attributed to adrenocortical tumors. X-ray computed tomography enabled accurate localization of the tumor in all 13 dogs. Apart from 2 poorly demarcated irregular-shaped and mineralized carcinomas, there were no differences between adenoma (n = 3) and carcinoma (n = 10) on CT images. In 1 dog, invasion of the caudal vena cava by the tumor was suggested on CT images and was confirmed during surgery. Suspicion of adhesions between tumors of the right adrenal gland and the caudal vena cava on the basis of CT images was confirmed during surgery in only 2 of 6 dogs. Survey radiography allowed accurate localization of the tumor in 7 dogs (4 on the right side and 3 on the left). In 6 of these dogs, the tumor was visible as a well-demarcated soft tissue mass and, in the other dog, as a poorly demarcated mineralized mass. The smallest tumor visualized on survey radiographs had a diameter of 20 mm on CT images. Six tumors with diameter less than or equal to 20 mm were not visualized on survey radiographs. In 1 of these dogs, a mineralized nodule was found in the left adrenal region, without evidence of a mass. In a considerable number of cases, survey radiography can provide presurgical localization of adrenocortical tumors in dogs with hyperadrenocorticism; CT is redundant in these instances. In the absence of positive radiographic findings, CT is valuable for localization of adrenocortical tumors.     

Central Diabetes Insipidus in a Dog With a Pro-Opiomelanocortin-Producing Pituitary Tumor ot Causing Hyperadrenocorticism

Central diabetes insipidus was diagnosed by vasopressin measurements during hypertonic stimulation in a 9-year-old male giant Schnauzer with polyuria and polydipsia. The impaired release of vasopressin was believed to be caused by a large pituitary tumor, which was visualized by computed tomography. Studies of the function of the anterior lobe and the pars intermedia of the pituitary gland were conducted, and high concentrations of ACTH and α-melanotrophic hormone (α-MSH) were found without concomitant hyperadrenocorticism. Studies of the molecular size of the immunoreactive ACTH in plasma by gel filtration revealed that most of the circulating immunoreactivity was not ACTH but its precursor pro-opiomelanocortin (POMC) and low-molecular-weight POMC-derived peptides. The pituitary tumor of this dog probably originated from melanotrophic cells of the pars intermedia. The sensitivity of the pituitary-adrenocortical system for the suppressive effect of dexamethasone was unaffected.     

Congenital hypothyroidism in Scottish Deerhound puppies

Two Scottish Deerhound puppies had clinical and pathological features consistent with the diagnosis of congenital non-goitrous hypothyroidism. They were from separate litters, but were the progeny of the same sire and dam. The puppies were smaller, had shorter limbs and shorter, broader heads than their littermates. They also had histories of weakness, difficulty in walking and somnolence. A characteristic radiographic feature was the absence of epiphyseal growth centres. Both had depressed serum thyroxine (T4) levels and one did not respond to exogenous thyroid stimulating hormone. On necropsy, the thyroid glands were small, the follicles varied in size and contained little or no colloid. The adenohypophysis contained many cells with markedly vacuolated cytoplasm. It is suggested that the clinicopathological pattern is the result of a primary thyroid abnormality. Possible mechanisms include either primary thyroid hypoplasia or an unresponsiveness to thyroid stimulating hormone.     

Force plate analysis before and after dorsal decompression for treatment of degenerative lumbosacral stenosis in dogs

OBJECTIVE: Using force plate analysis (FPA), determine ground reaction forces in dogs with degenerative lumbosacral stenosis (DLS) and evaluate the effects of lumbosacral decompressive surgery. STUDY DESIGN: Prospective clinical study. ANIMALS: Twelve dogs with DLS. METHODS: DLS was diagnosed by clinical signs, radiography, computed tomography, and/or magnetic resonance imaging. FPA was performed before surgery, and 3 days, 6 weeks, and 6 months after surgery. The mean peak braking (Fy+), peak propulsive (Fy-), and peak vertical (Fz+) forces of 8 consecutive strides were determined. The ratio between the total Fy- of the pelvic limbs and the total Fy- of the thoracic limbs (P/TFy-), reflecting the distribution of Fy-, was analyzed to evaluate any changes in locomotion pattern postoperatively. Ground reaction force data for DLS dogs were compared with data derived from 24 healthy dogs (control). RESULTS: In dogs with DLS, the propulsive forces (Fy-) of the pelvic limbs were significantly smaller than those of controls. P/TFy- was significantly smaller in dogs with DLS than in control dogs, and increased during the follow-up period, reaching normal values 6 months after surgery. CONCLUSIONS: Cauda equina compression in dogs with DLS decreases the propulsive force of the pelvic limbs and surgical treatment restores the propulsive force of the pelvic limbs in a 6-month period. CLINICAL RELEVANCE: In dogs with DLS, FPA is an effective method in evaluating the response to surgical treatment. Normal propulsive force in the pelvic limbs was restored during 6 months after decompressive surgery.