ENGLISH VERSION

ZESZYT 337

Mariusz Florek
Effect of chosen factors on calf slaughter value, physicochemical parameters of meat and its nutritional quality

The main researches included a total of 265 calves fed milk (or milk replacers) with additional 25 Limousine crossbred calves reared in a pasture-based management system with their dams for up to 7–8 months and 30 young animals slaughter cattle aged 15–20 months. There were assessed the slaughter value parameters (dressing percentage, colour of carcass superficial muscles, carcass cutting yield and the round dissection)  and meat physicochemical qualities (pH, specific electrical conductivity, colour, water holding capacity, tenderness and oxidative stability) as well as meat nutritional value (basic chemical composition, energy value, macro- and microelement contents, fatty acid profile). A total of 640 samples of the muscle longissimus dorsi (lumbar section) and semitendinosus muscle collected from carcasses of cattle categories under evaluation.
It has been indicated that at similar body weight prior to slaughter, the carcasses of crossbred calves from dairy cows and beef bulls showed a significantly higher (P < 0.01) hot and cold dressing percentage (58.61 and 57.14%, respectively) compared to Black and White calves (57.28 and 55.75%, respectively). The carcasses of purebred calf groups under investigation did not differ significantly in colour parameters (CIE L*, a*, b*) of superficial muscles and subcutaneous adipose tissue. There was not demonstrated a significant impact of calf breed and sex on the weight and primal cuts percentage in carcass as well as round dissection. The round of calves slaughtered in the autumn-winter season had a significantly higher meat content (P < 0.05), while lower fat amount (P < 0.01). Calf age and body weight growth prior to slaughter (P < 0.01) affected carcass body weight (hot and cold) increase, whereas carcass dressing percentage decreased. Higher body weight of animals before slaughter had a significant effect (P < 0.01) on increased meat content in the round with concurrent bone and fat contents decline. Growth of body weight and age of calves prior to slaughter induced darker colour of their meat (lowered L* – lightness and b* – yellowness values). Factors that affected meat physicochemical properties only insignificantly proved to be calf breed and sex. The meat obtained in the autumn–winter season appeared to be significantly (P < 0.01) less tender and darker. Age and body weight of calves before slaughter had also significant influence on specific electrical conductivity and drip loss. Commonly, a rise of calf age and body weight induced significantly darker colour of their meat (lower L* value) and more red colour (higher b* value) with greater drip loss and deteriorated tenderness. There was found a significant (P < 0.01) influence of the meat conditioning period on all the evaluated physicochemical parameters of the muscle longissimus dorsi (lumbar region) and semitendinosus muscle.
Calf sex and breed did not affect significantly a content of basic chemical components of meat, except fat, whose significantly (P < 0.05) greater amount (by 0.13 percentage units) was stated in crossbred calves’ meat. Meat protein content was not affected by any of the factors under study, it averaged 22.07%. A level of water, fat, ash, collagen and its content in crude protein (C/P) as well as net energy value were significantly (P < 0.01) differentiated subject to a season of animal slaughter. A higher content of fat, ash and net energy value was found in meat obtained in the autumn–winter season, whereas a water and collagen level appeared to be lower at that period. Age and higher body weight of animals before slaughter had significantly increased a content of fat, haematin pigments and energy net value, whereas decreased a level of water, collagen and its crude protein share. Meat of the investigated male calves and heifer calves did not differ in macro- and microelement contents (except potassium). A significantly higher concentration of microelements (except zinc) and generally lower of macroelements (except potassium) were recorded in meat of calves slaughtered in the autumn–winter season. Calf age and body weight before slaughter had a similar effect on a content of the analyzed elements in calf meat. There was observed a significant declining tendency in the case of zinc and calcium, while rising for iron with progressing animal age and body weight growth. The calf meat under investigation was characterized by a similar fatty acid profile, regardless of a slaughter period, sex and animal body weight. Breed and age of calves proved to be the only determinants (yet to a very limited extent) of fatty acid profile, differentiating significantly (P < 0.05) MUFA content as well as the ratio between UFA/SFA and MUFA/SFA. However, there were indicated significant interactions (calf breed × slaughter season) for content of SFA, UFA, MUFA, UFA/SFA and MUFA/SFA in the case of the muscle longissimus dorsi (lumbar region) and for PUFA, UFA/SFA and PUFA/SFA in the case of semitendinosus muscle.
Comparison of slaughter value and quality of meat from three age categories of young cattle revealed that carcasses of beef calves left with their dams in pasture-based management system for up to 7–8 months showed the significantly (P < 0.01) highest hot dressing percentage (61.8%) and cold (60.6%) as well as the highest content of the round weight (32.84%) and meat content (83.63%). Lower values were noted for milk calf carcasses (57.9, 56.4, 30.67 and 79.06), but the lowest for young slaughter cattle (53.3, 52.4, 28.52 and 77.31%). The significantly (P < 0.01) brightest proved to be meat from milk calves. Meat from beef calves maintained with their dams at pasture treatment for up to 7–8 months showed most red colour (a*) and yellow (b*) close to that of milk calves. Meat obtained from milk calves and beef calves allowed to stay with their dams in pasture-based system up to 7–8 months was characterized with similar oxidation stability which was nearly two-fold lower as against meat of young slaughter cattle. The evaluated meat from two first groups demonstrated the significantly (P < 0.01) lowest cooking loss, more beneficial M/T ratio and similar tenderness (66.7 and 75.2 N). The latter property was notably significantly lower (P < 0.01) as compared to meat of young slaughter cattle (110.2 N). The significantly highest water content (76.11%) and crude protein (22.65%) with the concurrent lowest level of intramuscular fat (0.78%) were found in meat of beef calves that remained with their dams in the pasture for up to 7–8 months. Meat of both calf groups demonstrated significantly lower energy value (gross and net) compared to meat from young slaughter cattle. A cattle category (related to age and feeding strategy) has significantly differentiated a content of all microelements studied (Zn, Fe, Mn, Cu) in the meat under assessment as well as potassium and magnesium. Meat from milk calves and those managed with their dams in a pasture treatment for up to 7–8 months exhibited a similar level of iron and magnesium. The highest microelement contents and the lowest amount of potassium and magnesium were found in meat of young slaughter cattle. Meat from younger animals, i.e. milk calves and those staying with their dams in the pasture for up to 7–8 months contained significantly less MUFA (41.94 and 41.22%, respectively) as compared to meat of young slaughter cattle (43.72%). The significantly (P < 0.01) highest content of PUFA (8.58%) and CLA (1.12%) as well as PUFA/SFA ratio (0.18) were determined in meat of beef calves left with their dams in the pasture for up to 7–8 months. Whereas the lower values in this respect (5.98%, 0.23% and 0.12, respectively) were reported in milk calf meat and the lowest in young slaughter cattle (3.67%, 0.20% and 0.07, respectively).