Effectiveness evaluation of the in vivo formation of mutton productivity and consumer properties from native breeds in the Volga region

The article assesses the production method of young native sheep in the Volga region being sold in their birth year. Scientific and industrial studies were conducted to evaluate the effectiveness of the in vivo formation of meat productivity and consumer properties of mutton from young sheep of the Bakur breed. The results of the studies showed that the average live weight of Bakur sheep at birth is 3.9 kg. In the weaning time at the age of 4 months sheep weigh 27.5 kg, that is, the weight increased 7.1 times. The average daily weight increase in Bakur rams up to a month of age was 233 g; from a month to 2 months of age - 223 g; from 2 to 4 months of age - 165 g. The best morphological composition of carcasses belonged to young animals of 12 months of age, the ratio of meat to other tissues reached 80.8% and 17.2%. The content of tryptophan in lambs and young animals significantly exceeds the amount of oxyproline, which is a representative of defective proteins. Based on the above facts, the muscle tissue of the longest back muscle has a high commercial quality due to the thinnest muscle fibers with small impregnations of fat and is considered the most tender.


Introduction
According to forecasts of the World Food Organization, the demand of the world's population for meat will increase by about 100 million tons, or 40%, by 2025. Perhaps, only Russia has serious opportunities for the extensive production growth due to natural resources (land, water, energy sources) [1]. Lamb combines a complex set of bio-and physico-chemical properties that determine its use in an exotrophic chain. However, in Russia its production is not sufficiently developed in comparison with the existing demand. Production and processing of sheep of regional breeds in the Volga region that will help to solve a problem of raw materials' deficiency and to raise economic indicators of producers can become perspective directions in expansion of the raw material base.
Improving the nutritional structure of the Russian population is largely determined by the rational use of regional raw materials for food production.
One of the main tasks of state policy in the field of healthy nutrition is the expansion of domestic production of the main types of raw materials that meet modern quality and safety requirements. The expected result will be the provision of 80-95% of domestic market resources of the main types of domestic meat raw materials and its processed products to 45-50% of the total domestic production.
Currently, lamb production is considered as the most promising and rapidly developing industry and amounts to 15 million tons per year.

Results and discussion
It is known that the growth of animals is a continuously proceeding process, manifested in an increase in the body weight through persistent formations of living matter as a result of the prevalence of synthesis over decay. And the increase in the size of a living organism occurs mainly due to the accumulation of protein substances in it. The growth of the body is greatly influenced by live weight at birth, breed characteristics, feeding conditions, etc.
The dynamics of live weight is considered one of the most objective indicators of a qualitative assessment of meat, fattening and biological productivity of animals.
Each country has its own standards for lamb carcasses. But in most of them, the optimal mass of carcasses in lamb production is considered to be 15 kg.
In Great Britain and Denmark, there are special categories for young sheep carcasses depending on their mass. According to them, slaughter of animals with a carcass weight of less than 15.5 kg is unacceptable (P. Hanrahan, J. Frederiksen, 1989).
In Germany, on the contrary, the demand for leaner meat of young animals is increasing. The need for slaughter with a live weight of 16-18 kg is growing, while animals with slaughter weight of 25-27 kg are in less demand.
The aim of scientific work was to evaluate the effectiveness of the in vivo formation of meat productivity and consumer properties of lamb of the Bakur breed produced in the Volga region.
One of the main biological features of young Bakur sheep is their ability to grow intensively at an early age. The results of the studies showed that the average live weight of Bakur sheep at birth is 3.9 kg. In the weaning time at the age of 4 months the sheep weigh 27.5 kg; that is, the weight increased 7.1 times (Table 3.1). The average daily weight increase in Bakur rams up to a month of age was 233 g; from a month to 2 months -223 g; from 2 to 4 months -165 g. 3 From 6 to 12 months of age, the rams showed insignificant growths, over this period they grew at an average rate of 71.1 g. Such a low increase in lambs can be explained by unfavorable conditions for keeping sheep in winter and, as a result, loss of live weight and fatness of sheep. Thus, the peak of the growth rate of Bakur sheep is in the suckling period, especially in the first two months of life [3].
Bakur sheep are relatively early-growing animals as they have a high rate of gain in live weight, good responsiveness to improved feeding, especially in the first year of life ( Table 2). The live weight of Bakur rams at birth in relation to the mass of one-year-old animals is 8.53%. It proves that the period of fetal growth is proceeding normally. The maturity of Bakur sheep up to 4 months of age is quite satisfactory -60.18. but from 4 to 6 months their early maturity is somewhat reduced due to a decrease in the growth rate and intensity.
For a more complete picture of the growth and development of Bakur sheep, as well as the characteristics of the exterior and type of constitution, which is closely related to the productivity of the animal, along with live weight, the data of the main body measurements, measured at birth, at the age of 1. 2. 4. 6 and 12 months are given.
The growth of various body parts in all studied groups of animals in connection with age varies with the same regularity. So, the highest growth rate was observed from birth to weaning. By 4 months of age, the value of the main measurements relative to their value at 12 months of age was: the height at the withers -95.3%, the oblique length of the body -88.7%, the chest width -63.9%, the chest depth -72.2%, the chest and metacarpals -respectively 80.0 and 75.2%.
The value of such measurements, as the height at the withers and sacrum, is due to the intensity of bone development in the mainly peripheral part of the skeleton -the tubular bones of the fore and hind limbs. Analyzing the age-related dynamics of the body, one can note a different degree of change in individual body parts in different periods of growth of young animals. Examples of such body parameters as height at the withers, oblique length of the body grow faster up to 4 months of age, while others -width, depth and girth of the chest change intensively not only until 4 months of age, but also in subsequent periods of development. In order to objectively compare the quantitative aspects of the meat productivity of young Bakur sheep, an experimental slaughter of 2-, 4-, 6-and 12-month old animals was carried out. As a result of the research, a number of patterns were revealed that reflect breed characteristics in the level and originality of the character of meat qualities of these animals (Table 3).
Live weight is an indicator of the precocity of animals, but it only indirectly reflects their meat productivity. The results of the control slaughter showed that animals at the age of 6 months produce 15.54 kg of dietary meat with a slaughter yield of 58.99%, which convincingly confirms their high meat qualities. The increase in the mass of the fat tail increased over 10 months from 0.85 to 3.7 kg, or 4.4 times (Table 3) [4,5].
It should be noted that with age, as in sheep of other breeds, the following pattern is observed: the proportion of cuts of the first grade is steadily increasing, which is associated with a high rate of muscle tissue buildup. Similarly to the varietal, the morphological composition of the carcass is also associated with the age of the animals. Assessing the meat qualities of the Bakur sheep breed of the studied age groups, it is clear that the proportion of the meat is increasing, and the bone is correspondingly decreasing. Carcasses from sheep at the age of 12 months, which amounted to 83.5%, had the largest meat yield (Table 4). As you know, an important indicator of the meat qualities of carcasses is the meatiness index (meatbone ratio). In the studied animals, this indicator increased to 12 months of age, compared with 2-monthold animals, it increased 1.4 times and amounted to 4.71. This is due to the fact that the meat increase in sheep at different age periods occurs with different intensities, therefore, feeding conditions are important. As a result of the rapid development of the meat, the area of the loin eye in Bakur rams increases from 10.0 cm 2 at 2 months of age to 17.8 cm 2 at 12 months, which is 43.8% (Table 3).
It is known that insufficient and moderate feeding in the early stages of post-natal ontogenesis slows down the development of animals and negatively affects the growth, primarily of muscle and adipose tissue and, to a lesser extent, bone growth. As a result, the yield of inedible carcass parts increases. The relative bone content at 12 months of age decreased slightly and averaged 17.2% (Table 4).
By the morphological composition of carcasses, Bakur sheep are not inferior to sheep of other breeds, and when slaughtered for meat, at different ages starting from 4 months old, they produce carcasses that exceed the quality requirements of mutton of the first category, for which the yield meat rate is 73.5 percent [6].
The decisive factor in assessing the quality of the carcass is the meat yield indicator. Of course, the feeding conditions have a great influence on the change in morphological composition of carcasses. When deboning carcasses of experimental animals, it was found that with age, the absolute mass of all tissues in rams increases (Table 4). So, for 2 months of the suckling period (from 2 to 4 months of age), the ratio of meat to other tissues increased from 76.2 to 77.7%, and bone decreased from 23.0 to 20.7%. By the age of 6 months, the ratio between the edible and inedible parts of the carcass has improved and amounted to 80.2 and 17.9%, respectively. The best morphological composition was carcasses from young animals of 12 months of age, the ratio of meat to other tissues reached 80.8% and 17.2% [7,8].
The specialization of the Bakur sheep for predominant development of meat-and-fat qualities found the most complete reflection in the breed specificity of the ratio of the anatomical carcass parts of various nutritional values (Table 5). Carcasses of young animals are distinguished by the most favorable ratio of anatomical parts highly valuable in food and nutrition. As a result of the better development of the middle and posterior third of the trunk, the heavier hip and lumbar (shortloin) parts are obtained from these animals. The morphological composition of cuts depends on the same factors as the morphological composition of the carcass of the animal as a whole.
In the carcasses of young animals, the most significant parts are the back-shoulder and hip -are developed quite proportionally, since their specific gravity is 40.0 and 27.7% at 2 months of age, 46.9 and 32.1%, respectively, at 4 x monthly, 43.9 and 32.2% at the age of 6 months, 42.9 and 32.8% at the age of 12 months. The lumbar (shortloin) portion accounts for respectively: 17.8; 11.9; 10.8 and 11.0% of the mass of the carcass. The least significant parts of the carcass have a slight development: the forearm, respectively -5.3. 2.9. 3.6 and 3.3%; shank (lamb knuckle) -4.7. 3.1. 5.7 and 6.4%; cut -4.5. 3.1. 3.7 and 3.5%. The carcasses of 12-month-old animals are characterized by an optimal proportion of tissues of different nutritional values (Table 5).
From the data of Table 7 it can be seen that the morphological composition of cuts is closely related to the age of the animals. The content of the meat in the cuts increases with age, and the specific gravity of the bones in them decreases.
So, the amount of meat in the spinal-shoulder cut from 2 to 12 months of age increases by 3 kg 570 g; in the hip (butt) -by 3 kg 30 g; in a lumbar cut (shortloin) -734 g; in the neck (scrag), forearm and shank (lamb knuckle) the increase is negligible. Consequently, such carcass parts as the back shoulder, hip and lumbar (shortloin) are characterized by the highest meat content.  Thus, different parts of the carcass grow unevenly. In all age periods, the largest proportion in the carcass is occupied by the back-shoulder cut, hip and lumbar (shortloin). Due to this, the output of meat products of the first grade is 85.18 at the 2-month age, 89.10 at the 4month age, 86.94 at the 6-month age and 86.77% at 12-month age and of the second grade is respectively -14.82. 10.90. 13.06 and 13.23%.
In view of the foregoing, it is advisable to use first-rate cuts (hip, back-shoulder, lumbar) from 12month old Bakur sheep for the production of dried sausages, neck, forearms, shanks for jelly products and first courses [9].

Nutrition value of mutton of Bakur breed
The nutritional value of meat is determined by the content in it of biologically complete and easily digestible nutrients necessary for the human body. The content of various components in meat depends on the ratio of muscle, fat and other tissues. Meat, in which adipose tissue is interspersed with the thickness of muscle tissue, is a high-calorie product. Adipose tissue is a source of vital unsaturated fatty acids.
To assess the nutritional value of lamb, as the main criterion for meat quality, the chemical composition of muscle and fat tissue of young animals from Bakur sheep, aged 2-, 4-, 6-and 12 months, was also studied. In addition, a chemical analysis of raw fat and tail fat was performed for all age categories.
As can be seen from the data in Table 8. the chemical composition of the meat of the animals studied was characterized by a general biological pattern: with increasing age, more fat accumulated in the carcasses, and the moisture content decreased. The moisture content in the edible parts of the carcass decreases from 73.18% (2 months) to 61.64% (in 12 months), or decreases by 11.5%. The protein content is quite stable, and its deviations depending on age are negligible. The amount of fat with age in carcasses of animals rises quite noticeably -from 6.44% at 2 months of age to 18.03% at one year old. The relationship between fat and protein is not so explicit, but increasing fat content will decrease protein [10]. Currently, it is considered to be the most optimal ratio of protein and fat in meat 1: 1. However, the Institute of Nutrition RAMS found that the most acceptable meat is that containing no more than 10-12% fat, that is, relatively lean, protein-rich meat.
The amount of protein and especially fat in meat depends on age, breed, gender, fatness of animals and other factors. In meat with a low fat content, for example, in young meat, there is more protein and moisture than in fatty meat, therefore its caloric content is less. Animals of early meat breeds already at a young age have the ability to early obesity. The carcasses of such animals are characterized by a high content of intramuscular fat, as a result of which the meat has good palatability and high calorie content. Lamb of 4-6 month old young animals contains the most optimal amount of fat. The ash content in meat varied slightly, since ash elements are found mainly in proteins, and not in adipose tissue. Compared with other breeds, the meat of young sheep of Bakur breed is characterized by the most optimal ratio of protein and fat (1:1).
In accordance with the fact that the amount of fat increases with age, the meat calorie content also increases. The calorie content of meat was 713.98 kJ / kg at 2 months of age, and 1178.72 kJ / kg at 12 months of age (Table 7).
To characterize the quality of meat, a very important indicator is the pH value, which allows to evaluate its properties and determine the direction of further processing. Immediately after slaughter, mutton of Bakur sheep has high pH values (6.81-6.55) (Fig. 1), which limits its use for the production of raw smoked and dried sausages.
But by 24-48 hours of storage, the decrease in pH reaches almost the minimum value (5.77-6.0) (Fig.  1), because almost all glycogen is hydrolyzed by this time to form lactic acid.
The content of tryptophan in lambs and young animals significantly exceeds the amount of oxyproline, which is a representative of defective proteins (Table 6). With age, in the meat of experimental animals, an increase in the content of these amino acids is observed, but at different rates.
Based on the above facts, the muscle tissue of the longest back muscle has a high commercial quality due to the thinnest muscle fibers with small impregnations of fat and is considered the most tender.

Сonclusion
The research results showed that the average live weight of Bakur sheep at birth is 3.9 kg, by the time of weaning from mothers at the age of 4 months -27.5 kg, that is, increased 7.1 times. The average daily increase to a month old was 233 g; from a month to a 2-month-old -223 g; from 2 to 4 months of age -165 g.
The formation features of lamb quality of Bakur sheep depending on age were established: the greatest slaughter yield of 58.99% was in sheep at the age of 6 months; the mass of the fat tail in 10 months increased 4.4 times; the meat index increased 1.4 times; an increase in the area of loin eye was 43.8%; CС increased from 3.81 to 5.24 from 2 to 12 months of age, i.e. by 27.3%. With age, the output of the first grade cuts increased from 77.68% to 89.0%, the meat content from 75.6% to 83.5% from 2 to 12 months of age, which confirms the advisability of using first-class