Abstract. The aim of the study was to verify whether an increased supply of vitamins E and C prevents the detrimental effects of ozone on the testes. The experiment was performed on 5-monthold rats exposed to ozone (0.5 ppm) for 50 days (5 h daily). Simultaneously, the animals were injected with the vitamins in 5-day intervals and at different doses (0.5, 1.5, 4.5, 5 and 15 mg of vitamin E; 0.5, 3, 9, and 50 mg of vitamin C; or both vitamins together, respectively). Gonad sections were PAS stained. In the ozonized males, depletion of germ cells occurred. In the vitamin E groups, the testes were comparable to the controls, excluding the 0.5-mg-dose vitamin E group in which perivascular fibrosis and intertubular hyalinization were observed. In the vitamin C groups, intertubular hyalinization, partial arrested spermatogenesis, and desquamation of the seminiferous epithelium appeared proportionall to the vitamin dose. Additionally, premature spermiation was found at a vitamin C dose of 50-mg. In the rats injected with both vitamins, hyalinization and fibrosis appeared in addition to partial arrest of spermatogenesis and vacuolar degeneration. In conclusion, vitamin E protects against the detrimental effects of ozone in rat testes irrespective of the dose applied. This was not observed for vitamin C. Moreover, administration of higher doses of vitamin C intensified the damage to the testes caused by ozone.

Summary ― Three feeding groups were used: the control (SOY) was fed diets without rapeseed products, and the two experimental groups were fed with either 10% rapeseed meal (RSM) or with 12% 00 rape seeds (PFRS). Half of the boars from each group were slaughtered after I or 2 years. In RSM and PFRS boars steroid-3-beta-ol-dehydrogenase activity was high, whilst Leydig cells were not numerous after 1 year. Degeneration and necrosis of seminiferous epithelium resulting in atrophy of seminiferous tubules appeared in RSM boars after 2 years. In the PFRS group the lesions were stronger and proliferation of Leydig cells with high steroid-3-beta-ol-dehydrogenase activity was observed. In 1-year-old RSM and PFRS boars there were foci of necrosis in the epididymal epithelium. Thyroid weight in RSM boars and liver weight in PFRS boars were distinctly higher only during the first year. In these thyroid glands flattening of glandular epithelium and enlargement of colloid masses were observed, while in the livers, parenchymatic degeneration and structural transformation appeared. Testis weight increased after 2 years in RSM and PFRS boars; however, this had little effect on semen production.

Four high-yielding lactating Holstein cows fitted with duodenal cannulas were used in the experiment. Cows were divided into 2 groups -control (Control) with leucine deficiency and experimental (Leucine) with a leucine supplement. The experiment was divided into 4 periods of 7 days, each consisting of a 3-day preliminary period followed by a 4-day experimental period. In the first period, 2 cows were assigned to Control and the remaining 2 to Leucine. In the subsequent period the cows were switched to the other treatment. Cows were fed individually twice daily the basal diet based on maize silage, lucerne hay and supplemental mixture. Infusions of amino acids in Leucine consisted of methionine (12.6 g/day), lysine (20.7 g/day), histidine (10.7 g/day) and leucine (19.3 g/day). The composition of amino acid infusate in Control was the same except for leucine that was replaced with monosodium L-glutamate. The intake of dry matter was not affected by the treatment (P > 0.05). No effect of leucine infusion on milk yield and composition was observed (P > 0.05), nevertheless the concentration of protein and casein in milk tended to be higher in Leucine (38.3 and 31.3 g/kg) than in Control (37.4 and 30.4 g/kg, respectively, P < 0.1). The yield of milk components was not affected by the treatment (P > 0.05). Duodenal infusion of leucine resulted in a decreased plasma level of isoleucine in Leucine compared to Control (P < 0.01). Concentrations of leucine, cysteine and citrulline tended to be higher and the concentration of tyrosine tended to be lower in Leucine in comparison with Control (P < 0.10).

In modern cattle production systems diet optimization, in particular at the early stage of calves' life, is of primary importance for their further growth and development. This is related to the specific structure and functions of the digestive tract of calves (Kertz et al., 1998). Xu et al. (1992) demonstrated that during the first days of animals' life, stomach weight increases by 25% and hydrochloric acid secretion increases twice. At the same time, the weight, length and width of the small intestine increase by 70%, 24% and 15%, respectively, while the depth of intestinal crypts and the length of intestinal villi increase by 24% and 33%, respectively. Considerable changes are also observed over this period in the structure of intestinal mucosa, under the influence of various nutritional factors (Zhang et al., 1997;Zitnan et al., 2003).Calf performance is affected not only by the properties of liquid milk replacers, but also by the texture of solid feed particles and the feeding period