In order to examine the effect of exogenous melatonin on selected biochemical variables of the blood in ruminants, dairy cows were given the pineal gland hormone in the dose of 0.1 mg/kg body weight. One and four hours after melatonin administration blood samples were collected from the cows in the control and the treated group in order to determine the levels of glucose, insulin, total cholesterol, triglycerides, free fatty acids, as well as the activities of alanine and aspartate aminotransferase. The pineal gland hormone caused a significant increase in the levels of total cholesterol and triglycerides, slight increases in glucose and insulin levels, and a significant decrease in the concentration of free fatty acids. Melatonin did not exert an effect on the activity of liver enzymes.

In order to examine the effect of exogenous melatonin on selected blood indices, dairy goats were given pineal gland hormone at a dose of 0.1 mg/kg body weight. Next, one and four hours after the melatonin had been administered, blood samples were collected from the goats in the control and treated groups in order to determine the levels of glucose, total cholesterol, triacyloglycerides, free fatty acids, as well as alanine and aspartate aminotransferase. The pineal gland hormone caused a significant increase in the levels of glucose, total cholesterol, triacyloglycerides and the activity of alanine aminotransferase. After melatonin administration a significant decrease in the FFA:TAG and FFA:Cholesterol blood ratios was observed. Moreover, no changes in the free fatty acid concentrations and the activity of aspartate aminotransferase were observed.

The experiment was designed in a bifactor model with five maize hybrids (Rasant, Dragon, LG 2252, San and Magister), mowed at two heights, i.e., 10-12 cm (A) and 50 cm (B). The average yield of dry matter of plants cut at a height of 50 cm (B) was 130.5 dt/ha and was significantly lower than the yield obtained from maize mowed at a height of 10-12 cm (A), where it amounted to 148.1 dt/ha. The percentage of ears showed the opposite trend, with 55.3 and 49.2%, respectively. Dry matter in all silages ranged from 35.9 to 42.1%. B silages contained more dry matter and starch, but less structural carbohydrate. Dry matter degradation in the rumen of these silages was increased (65.5-70.0%). Effective ruminal degradability of crude protein of all of the investigated silages (80.0-86.5%) was in the same range as that of starch (79.2-87.3%). A tendency towards reduced protein and starch degradabilities was observed in B silages. The average NDF loss after 24 h of ruminal incubation of silage samples produced from plants mowed at the traditional height (A) was 65.3-66.7%.

Studies were carried out in the two years in Trzcianka near Nowy Tomyśl, on brown soil, IIIa-IVa with pH 7.1-7.2. Plants of five maize cultivars were cut at the height of 15 cm and 55 cm. The lower parts of stems with leaves which remain on the field in case of high cutting, were characterized by a smaller content of protein and by a greater content of fibre, in comparison with the higher parts of plants. The energetic value of 1 kg of dry matter of the lower 40 cm part with leaves expressed in MJ NEL, in spite of significant differences in the chemical composition, was only insignificantly lower than the upper part. The content of dry matter, the chemical composition and the energetic value of both parts differed, depending on the cultivar.

In order to investigate the effect of melatonin on indexes of blood carbohydrate-lipid processes, cows were given melatonin intravenously in the amount of 0.1 mg/kg body weight in the morning on the second day after calving. Blood samples were collected three times: before, 1 h and 4 h after injection. The administration of the pineal gland hormone resulted in a significant (35%) increase in blood serum triglyceride (TG) concentrations and a nonsignificant (14%) increase in cholesterol concentration. At the same time in the experimental group, a lower free fatty acid (FFAs) concentration (by 13%) was observed along with lower values of FFA:TG and FFA: cholesterol ratios, while alanine aminotransferase (ALT) activity increased. The differences found in comparison with the control group were not significant. The glucose concentration and aspartate transferase (AST) activity did not change.

Kruczynska, N., Darul, K. and Nowak, W. 2002. Effect of mowing height on nutritive value of maize silage. J . Appl. Anim. Res., 22: 213-218. Iiivestigatioiis encoinpassed inaize silages prepared froin varieties: Rasaiit F A 0 200, Dragon F A 0 21 0, LG 2252, F A 0 230, Sail F A 0 240 and Magister F A 0 270. Dry matter content in case of plants inowed at the height o f 15 cin (A) ranged froin 33.4% (LG 2252) to 38.5% (Magister). Differeiices between varieties i n terms of the chemical composition of silages were slight and not unidirectional. An increase in the height of inowing froin 15 cin (A) to 55 cm (B) resulted iii sigiiificaiit iiicrease in the conceiitratioii of dry matter, decrease i n the ainouiit of structural carbohydrates (ADF, NDF) and improved N D F degradation in t h e ruineii. Variety L G 2252 w a s characterized by the lowest ruininal ,degradation o f starch. Starch digestibility i n the whole digestive tract was 99-100 per cent.

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Disappearance of cell walls, organic matter and protein were studied using the Nylon Bag technique for grass, white clover, and grasswhite clover mixture.