This study was conducted to evaluate animal performance, carcase characteristics and meat quality of young bulls and steers (Charolais  Holstein-Friesian), fattened until 15 and 18 months of age. One half of 40 young bulls were castrated at 2 or 3 weeks of age. Starting at 7 months of age, they received grass silage supplemented with concentrates. At the end of the fattening period, the animals were slaughtered, and carcase quality and the quality of meat from Musculus longissimus thoracis (MLT) were evaluated. Bulls had a higher carcase dressing percentage, and their carcases had higher lean meat content than steers. MLT from steers had higher intramuscular fat (IMF) content (by 0.89%); it was less tough, more tender and palatable. IMF from bulls had higher concentrations of polyunsaturated fatty acids (PUFAs) and a higher n-6/n-3 PUFA ratio than IMF extracted from steer meat. Older animals had higher carcase quality than those slaughtered at 15 months of age, and slaughtering at a later age had no negative influence on meat quality. ARTICLE HISTORY

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We investigated the effect of the amount of body condition loss in the dry period and early lactation in 42 high-yielding Holstein-Friesian cows on milk yield and the share of fatty acids in milk fat. Energy reserves were estimated based on the body condition scoring (BCS) and backfat thickness (BFT). Milk yield and milk composition were determined over 305-d lactation. From d 6 to 60 of lactation, the concentrations of 43 fatty acids in milk fat were determined by gas chromatography. Cows were categorized based on body condition loss from the beginning of the dry period to the lowest point of the BCS curve in early lactation into three groups: low condition loss group (L) ≤0.5 points (n = 14); moderate condition loss group (M) 0.75 to 1.0 points (n = 16) and high condition loss group (H) >1.0 points (n = 12). Cows whose body energy reserves were mobilized at 0.8 BCS and 11 mm BFT, produced 12,987 kg ECM over 305-d lactation, i.e. 1,429 kg ECM more than cows whose BCS and BFT decreased by 0.3 and 5 mm, respectively. In group H, milk yield reached 12,818 kg ECM at body fat reserve mobilization of 1.3 BCS and 17 mm BFT. High mobilization of body fat reserves led to a significant (approx. 5%) increase in the concentrations of monounsaturated fatty acids-MUFA (mostly C18:1 cis-9, followed by C18:1 trans-11), a significant decrease in the levels of fatty acids adversely affecting human health, and a drop in the content of linoleic acid, arachidonic acid and docosahexaenoic acid in milk fat. In successive weeks of lactation, an improved energy balance contributed to a decrease in the concentrations of unsaturated fatty acids (UFA) and an increase in the conjugated linoleic acid (CLA) content of milk fat.

The objective of this study was to determine the effect of body weight (BW) at slaughter and fattening intensity on carcass fatness and meat fatty acid profile in young Holstein-Friesian bulls. One-hundred bulls fattened on two levels of intensity a semi-intensive (SI) and an intensive (I) were used. Fattening was carried out to BW of 500, 550, 600, 650 and 700 kg. Live ultrasound measurements were performed to determine back fat thickness. Carcass dressing percentage, carcass conformation and fatness, intramuscular fat content of m. longissimus dorsi and fatty acid profile (by gas chromatography) were determined after slaughter. Intensively fattened bulls were characterised by a greater carcass dressing percentage -by 1.17% on average, greater carcass conformation scores, greater external fat thickness and a greater intramuscular fat content than bulls SI fattened. Fat from intensively fattened bulls contained higher levels of polyunsaturated fatty acids (PUFAs) -by 0.96/100 g on average. Semi-intensive fattening contributed to a decrease in the n-6/n-3 PUFA ratio and to a significant increase in the concentrations of C18:2 and C20:4 fatty acids. Regardless of the fattening intensity, the n-6/n-3 ratio was greater in heavier animals. The best results were achieved when young Holstein-Friesian bulls were fattened intensively to BW of 650 kg.