Mercury and mink. I. The use of mercury contaminated fish as a food for ranch mink.

Adult female and juvenile ranch mink were fed rations containing 50 and 75% of fish containing 0.44 ppm total mercury over a 145 day period. There was no clinical or pathological evidence of intoxication in these animals and mercury concentrations in tissue appeared to be at a level below that associated with toxicity.     

Dietary calcium-phosphorus ratios for growing pigs in relation to serum levels and bone development

Two experiments comprising a total of 80 Danish Landrace pigs in the period 20–90 kg live-weight were carried out to study the effect of dietary levels and ratios of Ca and P on serum values of Ca, inorg. P, and alkaline phosphatase and on the development of degenerative arthritis and atrophic rhinitis.In both experiments each kg feed (Table 1) was supplemented with 600 i. u. vitamin D₃ and 80 p. p. m. Zn.In the first experiment the Ca:P ratio was 1.2 and the amount of Ca increased from 0.48 % to 1.20 % without influencing daily gain, feed conversion, carcass performance (Table 2) or frequency of atrophic rhinitis (Table 3). The Ca:P ratio in scapula was 2.15. Only when the diet was supplemented with 1.20 % Ga and 1.00 % P the bone quality was histomorphologically adequate (Figs. 1–4).In the second experiment various Ca:P ratios (ranging from 0.1 to 3.0) were compared with the recommended level and ratio of 0.72 % Ga and 0.60 % P. Performance of pigs on the normal level was better than for the other pigs (Table 4). Clinically, various degrees of leg-weakness and -deformation occurred, most pronounced in the high Ca — low P group. Very little lameness and no convulsions were observed. Marked hypocalcemia was not found. Unilateral high Ca intake increased serum Ca significantly, and serum alkaline phosphatase slightly, and decreased serum P (Figs. 5–7). Advanced pericytic osteolysis, poor mineralization and generalized osteodystrophia fibrosa were found in the low Ca groups (Figs. 8–13). The groups showed no differences in frequency of atrophic rhinitis (Table 5), and rickets was not observed.The incidence of degenerative joint lesions was not increased in pigs on the unfavourable Ca:P ratios, and depended apparently more on litters than on diets.     

Intoxication in cattle caused by a batch of sugar beet pulp (author's transl)]

During the period from Dec. 7th 1972 to Jan. 8th 1973 76 cattle deaths were reported in 20 herds on the island of M?on and the adjacent south-eastern area of Sealand. The disease was characterized by a sudden onset and a rapid and invariably fatal course. Initially, there was a loss of appetite, depression, excessive salivation and incoordination. These symptoms progressed to paralysis and, in some animals, trmor and convulsions. Death usually ensued less than 2 hours after the first observation of symptoms. Losses in the herds varied from 1 to 12 animals. In herds with multiple incidents the majority of deaths occurred in the 24-hour-period following observation of the first case. Pathology: Gross lesions were few and inconclusive. Histology revealed marked dilatation of cerebral and maningeal blood vessels (arterioles, venoles and capillaries), with perivascular edema and haemorrhage. Adjacent neurons and glia cells showed various degrees of degeneration, apparently secondary to the vascular lesion. In all affected herds sugar beet pulp from one particular sugar mill had been used during the period preceding the outbreak. The syndrome was reproduced by feeding sugar beet pulp from this batch to two heifers. The heifers showed symptoms after 19 and 32 days' feeding, resp. and died after a few hours. Clinical and pathological features were identical with those observed in the spontaneous disease. Thus, it was proved that the particular batch of pulp was responsible for the disease. The investigation did not, however, reveal a toxic factor in this batch. Analyses for lead, arsenic, mercury, nitrite, alkyl phosphates, chlorinated insecticides and Cl. botulinum toxin were negative. Batches of the sugar beet pulp showed pronounced microbial deterioration, the flora being dominated by yeasts and filamentous fungi (moulds). Several species of fungi have been isolated but so fat their possible role in the etiology of the syndrome remains unsettled. The syndrome bears some resemblance to cerebrocortical necrosis (C.C.N.) but differs in several clinical and pathological details. It is tentatively suggested that the beet pulp may have contained one or more toxic substances that interfere with microbial activity in the rumen, resulting in a disturbance of synthesis or absorption of essential metabolites. The clinical, epidemiological and pathological findings are compatible with the hypothesis that the syndrome might be due to fungal toxins. Accordingly, the isolated fungi are now being studied in more detail.     

Poxvirus and multiple tumors in an eastern gray squirrel

A moribund juvenile gray squirrel (Sciurus carolinensis) with numerous skin fibromas was submitted to the Northeastern Research Center for Wildlife Diseases. Necropsy revealed multiple firm white nodules in the lungs. On histologic examination, in addition to the skin lesions, fibromatous proliferations were seen in the wall of the alimentary tract, in 1 mesenteric lymph node, and in the myocardium. Tubular adenomas were seen in the renal cortex, and the lung nodules were bronchoalveolar adenomas. Eosinophilic intracytoplasmic poxvirus inclusion bodies were seen in both the mesenchymal and epithelial tumors.     

Diurnal variation and the effect of feed restriction on plasma and milk metabolites in TMR-fed dairy cows

The objective was to study the diurnal variation in metabolites in plasma and milk of dairy cows fed total mixed rations (TMR) with a low-energy (LE) or high-energy content (HE) expected to give a minor and a major diurnal variation, respectively. Further, the purpose was to quantify and compare the responses in plasma and milk parameters when cows changed from ad libitum to restrictive feeding. Eight multiparous, early-lactating Danish Holstein cows were used in a cross-over design with two consecutive 14-day periods. Blood and milk samples were collected hourly on day 11 of each period and on days 12-14 of each period, the cows were fed restrictively (65% of ad libitum dry-matter intake). The concentration of beta-hydroxybutyrate (BHB) in plasma was significantly higher in the evening for cows fed the HE TMR, than for cows fed the LE TMR. There was a significant diurnal variation in BHB in milk, with the highest concentrations between milkings and the lowest concentrations at milking. Non-esterified fatty acids (NEFA) in plasma showed significant diurnal variation that was caused by high concentrations in the morning. Plasma glucose did not show any diurnal variation. It has been argued that feeding a TMR removes diurnal changes related to feeding, which is contrary to earlier diurnal studies where concentrates have been fed twice daily. Feed restriction increased (P < 0.001) NEFA and BHB in plasma by 121 and 90%, respectively, while the glucose concentration decreased (P < 0.001) by 19%. Milk concentrations of BHB, citrate and fat increased (P < 0.001) by 163, 11 and 26%, respectively, because of feed restriction, while there were no changes in milk protein and lactose. The relatively high increase in BHB during feed restriction suggests that BHB is more advantageous as a milk indicator of metabolic status in dairy cows than citrate and fat.     

Use of an immortalized bovine mammary epithelial cell line (MAC-T) to measure the mitogenic activity of extracts from heifer mammary tissue: effects of nutrition and ovariectomy

The objectives of the experiment were (1) to determine whether MAC-T cells would accurately mimic the previously observed proliferative responses of primary mammary epithelial cells (MEC) to mammary tissue extracts from high and low-fed heifers and (2) to determine whether mammary tissue extracts from ovariectomized (OVX) heifers would have lower mitogenic activity than intact controls. Addition of mammary tissue extracts to cell culture media of MAC-T cells plated on plastic or collagen-coated plastic to a range of concentrations between 1 and 8% resulted in dose-dependent increases in cell proliferation. Furthermore, mammary tissue extracts from low-fed prepubertal heifers aged 9 months, stimulated significantly more proliferation of MAC-T cells, as measured by 3H-thymidine incorporation into DNA than mammary tissue extracts from high-fed heifers (40.6 cpm x 10(3) per well versus 21.9+/-1.8 cpm x 10(3) per well). These observations suggested that MAC-T cells would be a suitable alternative to primary MECs for measuring the mitogenic activity of mammary tissue extracts. Conversely, no difference was observed in the mitogenic activity of mammary tissue extracts from OVX or control heifers. Possibly, MAC-T cells provide a good model for nutrition- but not ovarian-induced changes in mammary growth. Alternatively, that reduction of in vivo mammary development following OVX did not result in reduced mitogenic activity of the mammary tissue extracts emphasizes that heifer mammary development is the result of complex interactions between local growth factors and systemic hormones.