THE EFFECTIVENESS OF THREE-BREED CROSSINGS FOR INCREASING MEAT PRODUCTIVITY IN YOUNG SHEEP
This publication presents the results on the growth, development, live weight, body indices in ram lambs and ewe lambs of three-breed crossbreeds ♀ (♀Karakul 18.7% x ♂Avassi 31.3%) x ♂Assaf 50.0% and purebred Assaf, as well as the dynamics of the live weight gain of lambs from birth to 4–4.5 months of age. Crossbreed lambs are developed better than purebred lambs. The absolute weight gain in the ram lambs ♀ (♀Karakul 18.7% x ♂ Avassi 31.3%) x ♂Assaf50.0% was 4.8 kg, which is by 0.32 kg (7.1%) higher in relation to the ram lambs of the Assaf breed, the average daily weight is also higher by 5.4 g. According to the same trend, crossbred ewe lambs had a gross weight gain of 3.72 kg or by 0.22 kg (6.3%) more than in purebred ones and the average daily weight are also higher by 3.2 g.
Of the eight body indices, crossbred ram lambs and ewe lambs have five indices that exceed the obtained indicators in purebred animals, and in purebred lambs only three body indices are superior. In ram lambs of the Assaf breed, the indicators for three indices are higher in comparison to crossbreeds: transverse by 0.78%, chest by 0.5% and robustness by 4.65%, and for three-breed crossbreeds they are higher in relation to purebred ones according to the following 5 indices: body format by 4.33%, massiveness by 1.28%, bones by 0.58%, forehead width by 3.74% and head length by 1.42%. The indices of body format, bones and head length are also higher in the purebred ewe lambs by 0.12%, 0.46% and 1.36%, and in the crossbreeds the indices of transverse, massiveness, chest, and head width are higher by 1.21%, 1.35%, 2.02%, 0.29% and 2.97%.
The slaughter qualities of crossbreeds are higher for the most indicators taken into account, with the exception of the area of sheepskins. The slaughter weight of crossbred ram lambs is higher by 1.62 kg (13.2%) compared to purebred ram lambs, and the slaughter yield of carcasses is also higher by 2.88%. After deboning chilled half-carcasses, the mass of meat was higher in crossbred animals in comparison to purebred animals by 0.59 kg or 14.8%. All this denoted an higher meat ratio characterizing the relative development of bones and muscle tissues in crossbred animals with made up 2.51 vis-a-vis 2.34 in purebred ones. The highest weight of sheepskins was in crossbred ram lambs and amounted to 3.76 kg, which is by 0.65 kg or by 20.9% more than in peers. At the same time, purebred ram lambs had the largest sheepskins area of 80.3 dm2, which are by 5.52 dm2 (8.51%) more than in crossbreeds.
The interior parameters of the internal organs, the development of the digestive organs are closely related to the constitutionally productive characteristics of sheep. The internal organs of crossbred ram lambs, which also have the greatest pre-slaughter live weight, are somewhat better developed. At the same time, they surpassed their purebred peers in the mass of the lungs, spleen and kidneys. The weight of the lungs indicates the volume of respiration and the redox processes occurring in it, on which depend the health and endurance of animals. There were no significant differences in the absolute weight of the lungs in both groups of animals and they were almost the same and ranged from 0.550 g to 0.555 g. Thus, our results indicate that there is a positive relationship between the productivity of ram lambs and the development of their internal organs.
The digestive organs and their development ensure the future productivity of the animal. Crossbreed lambs by weight of the stomach without the contents of 973.2 g exceed they peers by 1.4%. The total length of the intestine also for this group of ram lambs is 36.38 meters or more than by 2.36%. In total, all this can lead to better use of the feed, increasing its digestibility.
At the ends of the slaughter were taken from each carcass their measurements and the indices were calculated. In crossbred three-breed ram lambs, all carcass evaluation indices are higher in comparison with purebred ones, with the exception of the chest depth index. The lamb leg development index in crossbreeds is significantly higher by 22.52% (P < 0.01), and in Assaf ram lambs is significantly higher the breast depth index if compared to crossbreeds by 14.61% (P < 0.001).
According to the chemical composition of meat in the group of purebred ram lambs and in the group of crossbreeds, the content of water in meat, protein and collagen is within the normal range and almost the same.
The high fat values in three-breed crossbreeds are 6.88%, which is by 2.15% more than in purebreds.
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