losses of crude protein during ensiling of herbages, in contrast to carbohydrates, do not affect the reduction of its content; their form is changed into greater solubility non-protein compounds and also highly degraded forms, which lower the efficiency of the microbial protein synthesis in the rumen. these processes are accompanied by a change of amino acid composition of herbage protein and decrease in intestinal digestibility of protein from feeds as a result of the formation of indigestible complexes with carbohydrates (adin). reduction of protein degradation in silages is achieved by accelerated acidity through addition of acids or dominance of homofermentative bacteria. the positive effects of fermentation inhibitors or sorbents use, as well as the wilting of raw material on the level and rate of protein degradation were demonstrated by many researchers. a greater contribution of protein nitrogen and reduction of deamination in silages can also be obtained by using bacteria inoculants. increasing the proportion of protein nitrogen is accompanied by the improved efficiency of microbial protein synthesis. Key words: silage, legumes, proteolysis, crude protein, nitrogen fractionsCurrent interest in the excessive nitrogen emission to the environment, in the form of ammonia to the atmosphere and nitrates into groundwater, in animal production primarily concerns ruminants, and results from low utilization of nitrogen (Huhtanen, 2010). The quantity of the nitrogen pool leaving the animal body depends on the efficiency of nitrogen conversion which in milk production is 18-30%, and in meat production 10-20%, which is far below the potential of cattle, which exceeds 40% (Dewhurst et al., 1996; Frank et al., 2002). These losses result from the low efficiency of microbial protein synthesis in the rumen, caused on the one hand by rapid and excessive degradation of plant protein,

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Studies were carried out on lipid and lipoprotein fractions in the serum of cows during summer and winter feeding. The experimental group comprised 32 Black-and-White cows in the final stage of pregnancy (2-3 weeks before calving) or in the 6th week of lactation. Total serum lipid (2.51 g/1) and cholesterol (2.51 mmol/1) concentrations were significantly lower (P<0.01) in cows subjected to drying than in lactating animals (3.29 g/1 and 3.86 mmol/1, respectively), irrespective of the feeding period. In contrast, the serum triglycerides concentration was 0.34 mmol/1 in cows before calving and twice as high than during lactation. It was also shown that HDL constituted the main fraction, and that HDL in cows prior to calving represented about 74% of serum lipids, increasing to about 80-85% during lactation. The LDL concentration was lower, representing, on average, 22% in dry cows, and 13-15% in the 6th week of lactation. Prior to calving, triglycerides represented over 40% of LDL, 32% was represented by cholesterol. In the peak of lactation the TG fraction in LDL decreased to 14-19%, while that of cholesterol increased to over 45%.

The aim of this study was to determine the composition of nitrogen fractions in alfalfa and red clover, which differ in proteolytic activity, and to evaluate the effect of wilting on changes in nitrogen fractions in alfalfa and red clover herbage. Total nitrogen was divided into protein and non-protein nitrogen, and the amino acid profile of protein was analyzed. Buffer-soluble nitrogen (BSN), including buffer-soluble protein nitrogen (BSPN) and non-protein buffer-soluble nitrogen (NPBSN), was determined. The NPBSN fraction was further subdivided into peptide nitrogen, amino acid nitrogen, neutral detergent-insoluble nitrogen (NDIN) and acid detergent-insoluble nitrogen (ADIN). Wilting in the field to 40% dry matter content (the swath was tedded once) did not reduce the total nitrogen content of alfalfa and red clover herbage, although it affected the concentration of the BSNfraction, in particular NPBSN, and free amino acid nitrogen. During alfalfa wilting, the soluble protein content decreased and the concentrations of non-protein nitrogen compounds increased, mostly due to an increase in free amino acid nitrogen. A reverse trend was observed during red clover wilting -the concentrations of non-protein nitrogen compounds decreased and soluble protein content increased. A decrease was also noted in peptide nitrogen, NDIN and ADIN. Wilting of alfalfa and red clover had no adverse effect on the amino acid profile of protein. The concentrations of essential amino acids that limit milk protein synthesis, i.e. Lys, Met, His and Arg, did not decrease. Legume wilting in the field contributes to an increase in the concentrations of soluble nitrogen in the plant material intended for ensiling.Key words: alfalfa, red clover, nitrogen fractions, amino acids, wilting. 724 ZAWARTOŚĆ fRAKCJI AZOTOWYCH ORAZ AMINOKWASÓW W ZIELONKACH Z LUCERNY I KONICZYNY CZERWONEJ BEZPOŚREDNIO PO SKOSZENIU ORAZ PO PODSUSZENIU NA POKOSACH AbstraktCelem pracy była charakterystyka składu frakcji azotowych w zielonkach z lucerny i koniczyny czerwonej, surowcach roślinnych różniących się potencjałem proteolitycznym, oraz ocena wpływu podsuszania na skład frakcji azotowych w tych zielonkach. Rozdzielono azot ogólny na azot białkowy i azot niebiałkowy oraz określono skład aminokwasowy białka. Ponadto określono związki azotowe rozpuszczalne w buforze (BSN), rozdzielono je na białkowe związki azotowe rozpuszczalne w buforze (BSPN) i niebiałkowe związki azotowe rozpuszczalne w buforze (NPBSN). We frakcji NPBSN wyodrębniono azot peptydowy oraz azot aminokwasowy, wydzielono także związki azotowe o niskiej rozpuszczalności (azot nierozpuszczalny w neutralnym detergencie -NDIN) i całkowicie nierozpuszczalne (azot nierozpuszczalny w kwaśnym detergencie-ADIN). Podsuszenie na pokosach do 40% suchej masy z zastosowaniem jednokrotnego zabiegu przetrzą-sania nie spowodowało ubytku azotu ogólnego w zielonkach z lucerny i koniczyny czerwonej, natomiast wpłynęło na koncentrację całej frakcji rozpuszczalnej w buforze, szczególnie jej części niebiałkowej, ora...

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