The present review comments on the role of the use of zeolites as feed additives on the prevention and/or the treatment of certain farm animal diseases. Both natural and synthetic zeolites have been used in animal nutrition mainly to improve performance traits and, based on their fundamental physicochemical properties, they were also tested and found to be efficacious in the prevention of ammonia and heavy metal toxicities, poisonings as well as radioactive elements uptake and metabolic skeletal defects. During the last decade, their utilization as mycotoxin-binding adsorbents has been a topic of considerable interest and many published research data indicate their potential efficacy against different types of mycotoxins either as a primary material or after specific modifications related to their surface properties. Ingested zeolites are involved in many biochemical processes through ion exchange, adsorption and catalysis. Recent findings support their role in the prevention of certain metabolic diseases in dairy cows, as well as their shifting effect on nitrogen excretion from urine to faeces in monogastric animals, which results in lower aerial ammonia concentration in the confinement facilities. Moreover, new evidence provide insights into potential mechanisms involved in zeolites supporting effect on animals suffered from gastrointestinal disturbances, including intestinal parasite infections. All the proposed mechanisms of zeolitesÕ effects are summarized in the present review and possible focus topics for further research in selected areas are suggested.

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The aim of the present study was to determine the normal ranges of the most commonly used serum biochemical parameters of sheep reared under Greek breeding conditions, as well as to test for the effects of the age and reproductive status of the animals on the normal values of these parameters. In total, 200 clinically healthy Chios sheep from 10 farms were used in the experiment. For the determination of the effect of age 150 sheep were assigned in three groups. Group A consisting of 50 lambs aged 2-6 months (mean +/- SD: 4.15 +/- 1.08), group B of 50 non-pregnant ewes into lactation aged 1-3 years (mean +/- SD: 2.12 +/- 0.86) and group C of 50 non-pregnant ewes into lactation aged more than 3 years (mean +/- SD: 5.98 +/- 1.66). For evaluating the effect of reproductive status 50 pregnant ewes in dry period were used, 15-30 days before the expected day of lambing (group D), along with the 100 non-pregnant ewes into lactation of groups B and C (group E). Blood sampling was performed once, in dry ewes from December to January, and in lambs and lactating ewes from March to May. The results showed that of the 14 biochemical parameters determined in serum, six were significantly affected by the age and eight by the reproductive stage of the animals.

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Fifty-two clinically healthy Holstein cows were randomly assigned to one of three groups according to their age and parity. The first group (A) consisted of 17 cows that were fed a concentrate ration supplemented with 1.25 per cent clinoptilolite, the second group (B) consisted of 17 cows fed a ration supplemented with 2.5 per cent clinoptilolite, and the third group (C) consisted of 18 cows, which were fed the basal ration containing no clinoptilolite. The rations were fed from four weeks before the cows' expected parturition dates until the beginning of the next dry period. Blood samples were collected from each animal at the start of the experiment, on the day of calving and then monthly, and analysed for serum glucose, ketone bodies, liver enzymes, blood urea nitrogen (BUN) and total proteins. The milk yield of each cow was recorded monthly. The cows in group B had significantly fewer cases of clinical ketosis during the first month after calving and a higher total milk yield. Feeding the cows with clinoptilolite for a long period had no apparent adverse effects on their liver function, and did not significantly affect the concentrations of glucose, ketone bodies, BUN and total proteins in their serum.