In this experiment the effect of the extensive diet (grass/grass silage and concentrate linseed supplemented) versus intensive diet (maize silage and concentrate) on the amino acid composition and mineral content of Hungarian Grey and Hungarian Holstein Friesian young bulls was analysed. In addition the relationships between fatty acid profile and amino acid composition as well as mineral content of longissimus muscle were investigated. The extensive diet caused some changes in the proportion of some amino acids including isoleucine, leucine, phenylalanine, threonine, valine, cysteine, glycine, proline, serine and ammonia. The breed influenced only the histidine concentration of longissimus muscle. In extensive groups arginine to glycine and arginine to leucine ratios were higher compared to intensive fed bulls. The mineral composition of longissimus muscle was mainly influenced by diet and there was a breed x diet interaction, whereas breed differences were detected for calcium (Ca) and sodium (Na). The phosphorus (P) and the iron (Fe) content in longissimus muscle of extensively fed animals were significantly higher, whereas Na and copper (Cu) content were lower. The beef of Hungarian Grey bulls contained less Ca and Na compared to Holstein counterparts. Cysteine and leucine concentration were positively correlated to intramuscular fat content and negatively with n-3 and n-6 fatty acids (FA). Among minerals the P and Fe content correlated negatively to intramuscular fat content. The closest correlations were determined between P and linolenic acid (C18:3n-3) as well as n-3 fatty acids (r=0.81). The lower n-6 and n-3 fatty acid ratio in extensive groups occured simultaneously with higher proline, valine, phenylalanine, P, and with lower glycine, cystine, leucine and sodium proportion in longissimus muscle.

The objective of the trial is to compare fattening performance, slaughter results and meat quality of bulls from international cattle breeds with local Hungarian breeds fattened under the same conditions. Altogether 62 growing bulls -Angus, Charolais, Holstein, Hungarian Grey, Hungarian Simmental, Charolais × Hungarian Grey -were fattened in small groups. The daily gain varied from 897 (Hungarian Grey) to 1 240 g/day (Angus). In general, the lower gain value is caused by the semi-intensive fattening system with low concentrate supplementation. The slaughter weight showed a similar tendency as final weight, there was a significant difference between Angus and Hungarian Grey. The killing out of Charolais (59.50 %), Angus (56.80 %) and Hungarian Simmental (57.84 %) was significantly higher than Hungarian Grey (55.13 %) and Holstein (55.03 %). Due to Charolais crossing the dressing percentage of Hungarian Grey was developed by about 1.5 %.The EU conformation scores of Charolais (9.50) and Hungarian Simmental (9.33) and the fatness scores of Angus (8.33) and Charolais × Hungarian Grey (7.33) were significantly higher than that of the other genotypes. The tissue composition of dissected carcass as well as ribs joint composition determined by X-ray computerised tomography method showed the lean meat of Hungarian Simmental and bone proportions of Holstein to be the highest, whilst Angus had the highest fat content. Charolais und Hungarian Simmental had significant higher longissimus muscle area in ribs joint compared to Angus, Holstein and Charolais × Hungarian Grey. Angus and Hungarian Grey had the highest intramuscular fat level of the three examined muscles.

In the past years several methods have been developed for the determination of the proportion of the nitrogen-containing substances of microbial origin passed from the rumen into the abomasum or the small intestine. Recently, on examining the D-amino acid content of foodstuffs, particularly milk and milk products, it has been observed that, in addition to D-Ala, Dglutamic acid (D-Glu) and D-aspartic acid (D-Asp) can also be detected in similar quantities, primarily in products which have links with bacterial activity. This gave rise to the idea of examining the diaminopimelic acid (DAPA), D-Glu and D-Asp content of bacteria extracted from the rumen of cattle and that of chyme from the same cattle, in order to determine the type of relation existing among these three components, and to establish whether D-Asp and D-Glu can be used in the estimation of protein of bacterial origin. On determination of the DAPA, D-Asp and D-Glu content by means of amino acid analyser and high performance liquid chromatography of duodenal chyme from five growing bulls and of ruminal bacteria from the same bulls, the following values were established. For chyme (and, in brackets, for ruminal bacteria) r value calculated by means of linear regression was 0.78 (0.76) between DAPA and D-Asp, and 0.70 (0.81) between DAPA and D-Glu. The r values between the crude protein content of ruminal bacteria and the markers examined were found to be the following: DAPA, 0.74; D-Asp, 0.73; D-Glu, 0.61. In the model experiment performed for the re-obtaining of values for protein of bacterial origin the theoretical values were determined on the basis of D-Asp and D-Glu and values approximately 10% higher than the theoretical value on the basis of DAPA. It is therefore recommended that in addition to DAPA these other two amino acids be included among the bacterial protein markers.

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