Zinc-responsive dermatosis in goats suggestive of hereditary malabsorption: two field cases

Two cases of zinc deficiency in dairy goats from different flocks and not associated with a zinc-deficient diet are described. Hard, dry, hyperkeratotic skin, hair loss and pruritus especially prominent on the back, legs, udder, face and ears were the most common clinical signs. Skin biopsy findings revealed a mixture of orthokeratotic and parakeratotic hyperkeratosis. On initial examination, serum zinc concentrations were low in both goats (461 microg L(-1) and 521 microg L(-1), respectively). Although mild skin lesions persisted during the early stages of zinc supplementation, skin lesions completely resolved after prolonged oral zinc supplementation. Withdrawal of zinc supplementation resulted in re-appearance of lesions in both animals. Case 2 gave birth to two kids, one of which showed mild skin lesions at 8 months of age together with a low serum zinc concentration (434 microg L(-1)), suggestive of hereditary zinc malabsorption. The other kid remained free of skin lesions and had a serum zinc concentration (530 microg L(-1)) within the normal range. On the basis of historical and clinical findings, the cases presented here more closely resemble Syndrome 1 hereditary zinc deficiency as seen in Nordic dog breeds rather than other zinc deficiency conditions seen in other species. It is suggested that zinc deficiency in these goats was due to hereditary malabsorption of dietary zinc. This is the first descriptive study of this condition in goats. Life-long zinc supplementation may be necessary in such patients.

Ultrasound imaging in determining the presence of testicular degeneration in two male goats

Physical examination and semen evaluation of two infertile goats were indicative of testicular degeneration. Ultrasonographically, the testicular parenchyma was uncharacteristically heterogeneous with foci of mineralization represented by dense hyperechoic areas, many of which showed acoustic shadowing. Histopathological examination of the testes post-mortem showed typical degenerative changes in the seminiferous tubules, with some affected tubules showing evidence of mineralization. The degree of mineralization appeared to correlate with the abundance of hyperechoic areas. It was concluded that ultrasound imaging can be used as diagnostic technique to confirm the diagnosis of testicular degeneration with mineralization.

Mechanism of recovery in esophageal epithelia of rats with severe zinc deficiency

Forty-six rats fed a Zn-deficient diet for 18 days, were divided into three groups and treated with Zn-deficient diet (GI), a normal (Zn-adequate) diet (GII) or a pharmacological Zn therapy diet (GIII) for 3 days. For light and electron microscopy, samples were taken at times 0, 8, 12, 24 and 72 h after treatment. In treatment GI, at all times, all rats had esophageal parakeratosis. With treatment GII, there was a variable progression toward normalization of the epithelium at 12 and 24 h. At 72 h there was almost complete recovery of normal epithelium. In treatment GIII at 8 h, large, light cells in the basal layer were shown to be present between dark cylindrical cells, a finding which was transitionary and disappeared at 12 h. Also, a thin keratinized layer was observed above the granular layer at 12 h. Recovery had progressed at 24 h and was complete after 72 h. The results are discussed in terms of a potential role of Zn in the sequence of cytochemical events in epithelial differentiation.

Zinc absorption, metabolism, and endogenous excretion in zinc-deficient and normal calves over an extended time

Zinc metabolism was studied in Zn-deficient and control Holstein calves over a 2-mo period following a single oral or i.v. 65Zn dose. In both orally and i.v. dosed animals, all gastrointestinal tissue sections from Zn-deficient animals contained more 65Zn than comparable tissues of controls. Contents of proximal small intestinal sections of Zn-deficient calves contained more 65Zn 8 to 10 wk after dosing than did those from controls; however, the reverse occurred in the distal small intestine, cecum, and large intestine. With both dosing methods, Zn-deficient calves retained more 65Zn throughout the study. Daily 65Zn excretion rate as a percentage of that retained declined for 6 wk after dosing, indicating a constantly increasing biological half-life. For deficient calves, the biological half-life was about 500 d in the later weeks of the experiments. In orally dosed, Zn-deficient animals, specific activity of fecal 65Zn exceeded that of serum Zn throughout the study. This shows a shortcoming in the basic assumption of measuring endogenous Zn loss from fecal and serum specific activities and total fecal stable Zn. Thus, endogenously excreted Zn is not representative of that remaining.

Recent developments in the roles of vitamins and minerals in reproduction

Vitamins and minerals affect reproductive function. Vitamin A deficiency has long been known to affect reproductive function in cattle. More recently, a role has been proposed for the vitamin A percursor, beta-carotene, in reproductive efficiency. Dietary supplementation with vitamin E and selenium may reduce the incidence of retained placenta, but these nutrients may also affect reproductive function in other ways. Calcium and phosphorus deficiencies affect reproduction in cattle, and vitamin D may directly affect reproductive function in addition to its role in calcium and phosphorus metabolism. Dietary manipulation of a number of other vitamins and minerals also influences reproductive function. However, the specific roles of nutrients in reproductive tissues are not well-defined in dairy cattle, and nutrient requirements for optimal reproductive efficiency in modern dairy cattle deserve careful reevaluation. This review provides a background of the effect of vitamins and minerals on reproduction and it attempts to provide a basis for further investigation of specific mechanisms by which reproductive function is affected. The interface between nutritional science and reproductive physiology provides considerable potential for optimizing reproductive efficiency in dairy cattle.

Trace element deficiencies and fertility in ruminants: a review

Various minerals (copper, cobalt, selenium, manganese, iodine, zinc, and iron) can influence reproductive performance of ruminants. Reproductive failure may be induced by deficiencies of single or combined trace elements and by imbalances. This review is focused on maladjustments of trace elements leading to impaired breeding performance. Opinion is diverse as to the existence of various reproductive disturbances from either a severe copper depletion or a marginal dietary copper deficiency. Field experience suggests that administration of cobalt to ruminants on cobalt-deficient diets improves their impaired breeding performance. Selenium infertility in ewes is more prevalent in some areas and in some seasons, but the actual cause of this malady and the continuing role of additional factors are unknown. Manganese is necessary for normal fertility in ruminants, and feeding low-manganese rations depresses conception rates. Lack of iodine impairs thyroid activity and also ovarian function. Reproductive failure in the female and in spermatogenesis are manifestations of zinc deficiency. Despite forages rich in iron, low availability in certain instances could affect adversely ruminant reproduction. Knowledge of biochemical dysfunctions from trace element deficiencies is essential to determine the role which trace elements play in fertility of ruminant animals.