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Evaluation of meat productivity of the offsprings of ukrainian black spotted dairy breed of different live weight by EUROP and JMGA systems
Meat productivity is an attribute the studying of which has a significant scientific and practical meaning. It is evaluated according to live weight and fatness. Nevertheless they do not give precise and objective data considering meat productivity. That is why the most precise evaluation can be achieved only after slaughtering of animals. Qualitative evaluation of beef should be carried out from two standpoints, as food stuff and as materials for processing.
An example of leading countries tells us that they concentrated all their efforts on creation of modern management systems in animal science field. In Ukraine, even now, meat-packing factories use methods given in old state standards. This particular problem does not give a possibility for national manufacturers to become equal players on the world market, even though conditions for this were established. That is why studying qualitative characteristics of meat productivity of animals with different live weight before slaughtering according to EUROP and JMGA systems are essential.
Conformation of carcasses has a direct impact on the yield of cutoffs during deboning. With refinement of conformation of carcasses the yield of technologically valuable cutoffs increases. With increase of factual live weight of stirks before slaughtering the points for conformation are increased nonuniformly. The highest value of that point 9,7 (R+) is observed at the mass from 401 to 450 kilograms, the lowest 7,6 (R-) – from 350 to 400 kilograms.
Carcasses of investigated animals were characterized by “inconspicuous” subcutaneous fat regardless of live weight before slaughtering. Intramuscular fat improves sensory qualities of beef (taste, aroma, softness). The low content of intramuscular fat impairs sensory quality but optimal content gives beef desired marbling and softness. The softness of meat depends on quantity of connective tissue diameter of muscle fibers, accumulation and distribution of fat.
In the groups of animals with different factual live weight point for marbling of the longest spine muscle (m. lingissimus dorsi) fluctuates from 2,7 to 4,0. The highest value of that point can be observedat live weight of 500 kilograms before slaughtering. The color of muscular and fat tissues with the increase of factual live weight before slaughtering intensifies and enlarges according to color strip from 5,0 to 5,8 points and from 4,7 to 5,3 points.
The longest back muscle (m. longissimus dorsi) – the biggest muscle in the musculature of the spine and constitutes the basic mass of the meat of two valuable junctures – sirloin and back parts. With increase of live weight of stirks before slaughtering its area was increasing but at the mass of over 500 kilograms we observed decline down to 72,0 сm2. The thickness of subcutaneous fat on carcass is an important index and influences technological indexes of beef quality. The increase of its thickness on carcass is undesirable so as the quantity of fat cutoffs increases and the yield of eatable parts of carcass declines.
The thin layer of subcutaneous fat in the carcasses is also undesired so as it causes fast cooling which may become the reason for stiffening of beef, drydown, discoloration of muscle tissue. The thickness of subcutaneous fat on the carcass increases depending on factual live weight of animals before slaughtering from 0,7 (from 350 to 400 kilograms) to 1,3 cm (over 500 kilograms).
Coefficient of correlation between marbling and thickness of subcutaneous fat on carcass at live weight from 350 to 400 kilograms estimates 0,46 (moderate), at live weight from 401 to 450 kilograms – 0,42 (moderate), from 451 to 500 kilograms –
0,10 (low) over 500 kilograms – 0,65 (moderate). Marbling increases with theenlargement of subcutaneous fat on carcass. Received data approve the correlation between marbling and the thickness of subcutaneous fat on carcass which would allow manufacturers to forecast marbling depending on the thickness of subcutaneous fat on the carcass of slaughtered animals.
Key words: factual live weight, conformation of carcasses, the longest back muscle (m. longissimus dorsi) marbling.
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