New Zealand White rabbits were used to investigate the influence of increasing dietary P concentrations on growth performance, mineral balance, kidney calcification and bone development. The minimum dietary P requirement of 0·22 % (National Research Council) is usually exceeded in commercial natural-ingredient chows, leading to undesirable kidney calcifications. In order to study the optimal dietary P level, rabbits were fed semi-purified diets with four different P levels (0·1, 0·2, 0·4, and 0·8 %; w/w) at a constant dietary Ca concentration (0·5 %) during an 8-week period. Body weight and growth were not influenced by the dietary P level. During two periods (days 20 -23 and 48 -51), faeces and urine were collected quantitatively for the analysis of Ca, Mg and P and balances were calculated. Increased dietary P intake caused increased urinary and faecal P excretion and P apparent absorption and retention. Faecal Ca excretion increased with higher dietary P levels, whereas urinary Ca excretion reacted inversely. The apparent absorption of Ca became reduced at higher dietary P concentrations, but Ca retention was unchanged. The response of Mg was in a similar direction to that of the Ca balance. Kidney mineral content increased with higher dietary P levels, indicating the presence of calcified deposits. Nephrocalcinosis became more severe in kidney cortex and medulla at increasing dietary P levels, as was confirmed by histological analysis. Femur bone length was not differentially influenced by dietary P. Bone density (g/cm 3 ) of the femur diaphysis became significantly lower at the 0·8 % dietary P level as compared with the 0·2 % P group only. The bone Mg content was significantly increased on the 0·8 % P diet, both in the diaphysis and epiphysis. Plasma P concentration increased and plasma Ca decreased with higher dietary P levels, whereas plasma Mg levels were unaffected. The present study shows that the current recommended minimum dietary P level of 0·2 % for rabbits, as advised by the National Research Council in 1977, leads to a normal growth and bone development, but also causes some degree of kidney calcifications at a dietary Ca level of 0·5 %. As the dietary P level of 0·1 % virtually prevented kidney calcification and at the same time did not give evidence for any deleterious effects on growth and bone development, this indicates that the current recommended dietary P level for rabbits should be regarded as a maximum advisable concentration, and that a lower P level may be more optimal.

The hypothesis tested was that exposure of broiler chickens to an electromagnetic field (EMF) may reduce the signs of coccidiosis infection, based on recent insights into immunology. The experiment had a 2 x 2 factorial design. An uninfected and an infected group did not receive further treatment, whereas the other uninfected and infected groups were subjected to EMF treatment. In the cages of EMF-treated birds, a field strength of 5 muT root mean square was created for a period of 30 min/d. Infected birds were given a single dose of a mixture of Eimeria species (1.76 x 10(4) sporulated oocysts of Eimeria acervulina, 1.25 x 10(4) sporulated oocysts of Eimeria maxima, and 7.5 x 10(3) sporulated oocysts of Eimeria tenella) through gavage into the crop. Infection with the Eimeria mixture induced intestinal lesions, shedding of oocysts, and a reduction in growth performance. Exposure of broiler chickens to the EMF antagonized the effects of infection. In the EMF-treated birds, the infection caused no effect on weight gain and feed intake, whereas the severity of intestinal lesions mediated by E. acervulina and E. maxima was less than in the infected controls. We suggest that EMF has anticoccidial activities and its application could serve as an alternative to the anticoccidial drugs currently used in poultry production.

A hypothesis is proposed how Low Frequency Electromagnetic Field (LF EMF) exposure can stimulate an immune response, based on recent insights in immunology. We hypothesize that the Immunent EMF treatment induces mild stress to cells, which then produce cytokines that function as alarms or so called danger signals for the immune system. In this way EMF treatment takes the place of multiplying pathogens, and the damage these cause, in the triggering of an immune response. In a first series of experiments in vitro common carp head kidney-derived phagocytes were used to determine ROS production as a measure for immune activation. Exposure to LF EMF signals (200-5,000 Hz) at 5 lT or 1.5 mT led to 42 or 33% increase in immune activity, respectively, compared to negative control values. EMF could also additionally stimulate chemically pre-stimulated samples up to 18% (5 lT) or 22% (1.5 mT). Significance of increase in ROS production in the total series was: p < 0.0001. In a second series of experiments in vitro commercial goldfish were used. Groups of fish were housed under equal conditions in at least four control tanks and 8-16 EMF-exposed tanks. Exposure was done with a predominantly vertical field at field strengths (rms) between 0.15 and 50 lT. Without treatment mortality was about 50% after 18 days, while the treatment at 5 lT reduced it to 20% on average. At field strengths 0.15, 0.5, 1.5, 5, 15 and 50 lT an equally strong effect was found. Reducing the field strength to 0.05, 0.06, 0.01 and 0.003 lT showed a gradually decreasing effect, which only at 0.003 lT is no longer statistically significant. Finally, in vitro experiments were done with 560 commercial broiler chickens exposed to infection pressure from coccidiosis. EMF exposure at 6.5 lT reduced intestinal lesions by 40% and improved feed conversion by 8%.

The effect of dietary fluoride (F) on nephrocalcinosis was studied in young, female rats. Nephrocalcinosis was induced by a diet rich in phosphorus (P). F in the diet effectively counteracted P-induced nephrocalcinosis in a dose-dependent fashion. The feeding of increasing amounts of F caused decreasing calcium (Ca) and F concentrations in kidney. This suggests that the amount of Ca in kidney determines F accumulation in this organ, rather than F intake. Increasing amounts of F in the diet caused increasing rates of urinary and fecal excretion and whole-body retention of F. Dietary F did not influence urinary and fecal excretion and plasma concentrations of Ca, magnesium (Mg), and P. The metabolic basis for the protective effect of F against the development of nephrocalcinosis remains to be established.