INTRODUCTIONModern market conditions call for highlycompetitive sheep breeding, which requires specializedmeat production of high quality. Sheep meat is the mostexpensive meat in developed countries. Its consumptiondepends on cultural factors and tends to increase withgrowing population and incomes. Major exportingcountries see a decline in their sheep stocks caused bythe shrinking wool market. Sheep meat production isexpected to be developed by small and medium-sizedfarms close to their markets [1].Today, there is an urgent need for highly productiveyoung sheep and safe lamb meat of high-quality. Theworld demand for lamb is very high, both in nutritionaland commercial terms. Therefore, lamb production is apriority in Russia and abroad [2].Many studies have shown that lamb aged 0–7 monthsis the best type of sheep meat. Russia consumes 1.0kg of lamb per capita, compared to 1.29 kg worldwide.Private farms account for 88.6–89.2% of sheep meatproduction in Russia [3].Nutrition is one of the main factors of meatproductivity alongside good maintenance conditions [4].Selective breeding of farm animals is also gainingground. It aims to produce new genotypes of wool-andmeatsheep for manufacturers of livestock products.To fully realize the genetic potential of wool-andmeatsheep genotypes, we need to improve their feedingsystems by adding new supplements of plant and186Marynich A.P. Foods and Raw Materials, 2022, vol. 10, no. 1, pp. 185–194animal origin to enhance their productivity. Adequatenutrition is the main principle of animal feeding thatcontributes to higher productivity. Diets should bedifferentiated according to production schemes andplanned productivity. Rationed feeding is one of themost important indicators of nutrition that ensuresnormal physiological state, high productivity, goodreproductive qualities, and production profitability.Nutrition enhanced with feed supplements rich inbioactive substances is the most rational way to obtainlow-cost and high-quality products [5]. Radzhabov et al.provide a good coverage of intensive sheep raisingmethods based on adequate feeding [6].By-products of starch, dairy, meat, and other industriesare increasingly used as feed supplements in animaldiets. However, it is important to study their composition,nutritional benefits, and possible side effects for theanimal organism [7, 8]. Most changes caused by feedsupplements occur at an early age, during intensive growthand development of lambs. This is a period of greatestassimilation of feed nutrients leading to the maximumincrease in live weight. Feed supplements improve animalproductivity, activate digestive metabolic processes, andultimately make sheep breeding cost-effective [9, 10].The ORGANIC supplement (patented in Russia) is ahigh-protein feed supplement obtained from collagencontainingsolid waste of leather production. It is usedto enrich feed for all types of productive animals, fish,and poultry, with a highly digestible, “protected” protein.The product has stable quality indicators, namely82–85% of crude protein and а complete compositionof essential and non-essential amino acids. It facilitatesdigestion and gastrointestinal functioning, whichimproves the digestibility and absorption of feednutrients, as well as increases the natural resistance ofthe animal’s body [11].We aimed to study the effect of the ORGANIC feedsupplement on the growth and development of sheep,meat productivity, and economic efficiency.To achieve the aim, we set a number of objectives,namely to:– formulate new starter feeds for wool-and-meat lambsaged 0–4 months based on their maintenance andfeeding conditions;– evaluate the effect of starter feeds on the growth ofyoung sheep, as well as meat productivity and quality;– assess the effect of starter feeds on the biochemical andmorphological parameters of blood and general health ofyoung sheep; and– calculate feed efficiency and economic efficiency ofusing starter feeds in young sheep breedingSTUDY OBJECTS AND METHODSWe aimed to test new starter feeds for wool-andmeatlambs aged 0–4 months of the Russian MeatMerino breed. Experimental studies were conducted atthe Vtoraya Pyatiletka Breeding Farm (Stavropol Krai,Russia).Its sheep breeding technology involves stall andpasture maintenance; weaning (at the age of 120 days);shearing (May – June); grazing (on pastures withkosher basic feeding technology); artificial insemination(September – October); and lambing (February – March).When in the stalls, sheep receive coarse, juicy, andconcentrated feeds.Diets for young sheep were determined by suchfactors as age, live weight, and productivity [9]. Weused three diets, namely: standard feed (control), starterfeed with 5% of skimmed powered milk as a whole milkreplacer (experiment), and starter feed with 3% of theORGANIC supplement (experiment). The compositionof starter feeds and their nutritional value are shown inTable 1.Compared to standard feed (Formula 1), starterfeed with the whole milk replacer (MR) (Formula2), and starter feed with the ORGANIC supplement(OS) (Formula 3) had higher values of total nutritionalvalue (by 4.7 and 6.6%, respectively), crude protein(by 19.8 and 27.3%, respectively), digestible protein(by 7.6 and 15.1%, respectively), lysine (by 23.7 and18.6%, respectively), methionine + cystine (by 32.7%),threonine (by 23.1 and 21.2%, respectively), and crudefat (by 83.4 and 82.7%, respectively) (Table 1).The formulated starter feeds (Table 1) were testedon three groups of ewes (12 heads in each) with singleram lambs (aged from 2 days to 4 months) based on theanalogous pair principle (Table 2).As we can see in Table 2, the control ram lambs(group I) received alfalfa hay and standard feed(Formula 1) based on the formulation of the All-RussianResearch Institute of Animal Husbandry. For the rams inthe experimental groups, the standard feed was replacedwith starter feed with the milk replacer and starter feedwith the ORGANIC supplement, respectively.Feed samples were analyzed at the Feed andMetabolism Laboratory, Stavropol State AgrarianUniversity. Total nitrogen (crude protein) wasdetermined on a UDK-142 protein (nitrogen) analyzer,crude fat – on a SER-148 fat analyzer, macro- andmicroelements – on a Spectroscan MAX GV universalanalyzer, vitamins – on a LCMS-10 EV liquidchromatograph, crude fiber – on a FIVE fiber analyzer,and total feed moisture – on an AD-4714 A moistureanalyzer.The guidelines by Dmitrik et al. were used todetermine the morphological composition of lambcarcasses and conduct a microstructural analysis of theLongissimus dorsi muscle [12]. The animals’ internalhomeostasis was assessed on the basis of morphologicaland biochemical blood analyses [13, 14]. The countingof erythrocytes and leukocytes was performed in theGoryaev chamber. The leukocyte formula was based ona blood smear stained using the Romanowsky-Giemsatechnique. The results were biometrically processedusing statistical methods (Microsoft Excel).187Marynich A.P. Foods and Raw Materials, 2022, vol. 10, no. 1, pp. 185–194Table 1 Feed formulations for lambs aged 0–4 months*Formula 1 – standard feed used at the Vtoraya Pyatiletka Breeding Farm** Formula 2 – starter feed with 5% of milk replacer (New Compound Feeds Company)*** Formula 3 – starter feed with 3% of ORGANIC feed supplement (New Compound Feeds Company)Indicator Feed formulationsFormula 1* Formula 2** Formula 3***Feed composition, %:Barley 29.00 14.00 15.00Oats 28.0 – –Wheat 10.00 14.00 15.93Wheat Bran 10.00 11.33 15. 0Corn – 20.00 15.00Peas 10.0 – –Sunflower cake (crude protein 34%, crude fiber 20) 10.00 19.97 20.00Alfalfa flour (crude protein 14.0 %) – 10.00 10.00ORGANIC feed supplement – – 3.00Skimmed milk powder – 5.00 –Feed yeast (crude protein 42%) – 3.00 3.00Feed chalk – 0.58 0.35Monocalcium phosphate 1.00 0.50 1.03P61-1 premix for calves 1.00 0.80 0.80Table salt 0.70 0.82 0.89Components:Energy feed units 1.06 1.11 1.13Metabolic energy, MJ 10.6 11.1 11.3Dry matter, g 880.0 891.8 890.6Crude protein, g 149.3 178.8 190.0Digestible protein, g 131.5 141.5 151.4Lysine, g 5.9 7.3 7.0Methionine + cystine, g 4.9 6.5 6.5Threonine, g 5.2 6.4 6.3Crude fat, g 28.3 51.9 51.7Crude fiber, g 79.7 90.1 93.8Sugar, g 37.7 35.6 33.4Ca, g 3.26 8.0 8.6P, g 7.21 6.7 6.9Mg, g 2.6 2.3 2.5Table salt, g 1.4 10.0 10.0Fe, mg 78 20.0 20.0Cu, mg 5.2 4.0 4.0Zn, mg 31.4 32.0 32.0Mn, mg 35.5 40.0 40.0Co, mg 2.0 2.0 2.0I, mg 1.0 1.2 1.2Se, mg 0.11 0.16 0.16Vitamins:A, thousand IU 4.8 16.0 16.0D3, thousand IU 0.01 3.20 3.20Е, mg 12.5 56.0 56.0В1, mg 3.5 2.4 2.4В2, mg 1.1 8.0 8.0В3, mg 9.3 16.0 16.0В5, mg 13.0 8.0 8.0В12, mg – 0.016 0.016188Marynich A.P. Foods and Raw Materials, 2022, vol. 10, no. 1, pp. 185–194Group Diet descriptionI (control) Normal diet (ewe milk, alfalfa hay, mineral feed) + standard farm feed (Formula 1)II (experimental) Normal diet + starter feed with whole milk replacer (Formula 2)III (experimental) Normal diet + starter feed with ORGANIC supplement (Formula 3)Table 2 Diets of suckling lambs aged 0–4 months (n = 12)Indicator GroupI(control)II(experimental)III(experimental)Alfalfa hay 0.30 0.36 0.36Standard farmfeed(Formula 1)0.41 – –Starter feedwith the wholemilk replacer(Formula 2)– 0.42 –Starter feedwith theORGANICsupplement(Formula 3)– – 0.42Table salt, g 6.0 6.0 6.0Felucenmineral salt, g5.0 5.0 5.0Disodiumphosphate, g4.9 4.9 4.9ComponentsEnergy feedunits0.64 0.72 0.72Metabolicenergy, MJ6.4 7.2 7.2Dry matter, g 0.60 0.70 0.70Crudeprotein, g98 120 123Digestibleprotein, g79 90 93Lysine, g 4.20 5.24 5.10Methionine +cystine, g2.90 3.80 3.80Crude fiber, g 112 134 134Sugar, g 23 23 23Са, g 5.2 8.0 7.9Р, g 5.8 4.6 5.1Mg, g 1.51 1.51 1.57NaCl, g 6.7 6.3 6.3Fe, mg 82.3 69.2 68.4Cu, mg 5.80 5.71 5.66Zn, mg 22.0 24.6 24.3Mn, mg 35.7 42.4 41.9Co, mg 0.9 1.0 0.9I, mg 0.41 0.52 0.52VitaminsA, mg 12 34 34D3, thousand IU 31 1376 1360Е, mg 37 62 61Table 3 Actual feed intake by sheep aged 0–4 monthsRESULTS AND DISCUSSIONAdequate feeding, especially during intensive growthand development, is highly important for the animals’productivity. In our study, the lambs’ needs for basicnutrients were determined by their health and growthindicators.Substituting the standard feed (Formula 1) for starterfeeds containing the milk replacer (Formula 2) and theORGANIC supplement (Formula 3) in the diets of sheep(Table 3) aged 0–4 months increased their metabolicenergy (by 12.5%), crude protein (by 22.4 and 25.5%,respectively), lysine (by 24.8 and 21.4%, respectively),methionine + cystine (by 31.0%), and vitamins A, D, E(1.6–44.3 times).Table 4 shows the total feed consumption by theexperimental lambs during the suckling period. Over120 days of growth, the control group consumed77.47 energy feed units and 8.62 kg of digestibleprotein. In the experimental groups, energy feed unitswere lower by 1.98 and 1.73 and digestible protein by0.279 and 1.430 kg, respectively. As we know, ewesproduce plenty of milk (1.2–1.5 liters) during lactationto meet their lambs’ nutritional needs. However, itsamount significantly reduces in the months followinglactation. For this reason, we formulated starter feedscontaining the milk replacer (WMR) and the ORGANICsupplement (OS).Feeding starter feeds to suckling lambs for fourmonths affected their live weight (Fig. 1). ComparedTable 4 Feed consumption by sheep during the sucklingperiodGroup DietEwemilkAlfalfa andlegume hayFeed TotalStandard farm feed(control):– feed weight, kg– energy feed units– digestible protein, g136.040.80448810.84.9744324.431.703684171.277.478615Starter feed withwhole milk replacer:– feed weight, kg– energy feed units– digestible protein, g136.040.80448811.25.1545925.833.503947173.079.458894Starter feedwith ORGANICsupplement:– feed weight, kg– energy feed units– digestible protein, g136.040.80448810.95.0044725.733.405110172.679.2010045189Marynich A.P. Foods and Raw Materials, 2022, vol. 10, no. 1, pp. 185–194to the control lambs, live weight of the experimentallambs aged 120 days in the groups that received starterfeeds with the WMR and OS increased by 8.8 kg, or29.63% (P ≤ 0.001), a nd 10.0 kg, or 33.67% (P ≤ 0.001),respectively. The average daily gain rose by 73.0 g,or 34.11% (P ≤ 0.001), a nd 83 g, or 38.78% (P ≤ 0.001),respectively, with 100% animal safety.Therefore, we found that the use of starter feedswith the WMR and the OS instead of standard feed waszootechnically justified. These feeds contributed to abetter palatability of the diet feed and a greater intake ofnutrients.Lamb production needs to be increased to enhancethe economic efficiency of sheep breeding. The meatfrom sheep aged up to one year is easily digestible andhas a low fat content. For this reason, it is recommendedfor dietetic diet. Scientists have also established that themost intensive weight gain occurs in the first six months.For the next stage of our study, we carried out acontrol slaughter of lambs at the age of four months.This age was due to intensive protein deposition inthe first six months. Adipose tissue accumulatingFigure 1 Live weight and live weight gain of young sheep that received: 1 – standard feed (control); 2 – starter feed with the wholemilk replacer, 3 – starter feed with the ORGANIC supplement; n = 12more intensively in the later period of life affects thebiological value of meat and the economic efficiency oflamb production.Hematological parameters show a complete pictureof the organism’s development. We found that the bloodparameters of 4-month-old lambs of the experimentaland control groups were within the physiological norms(Fig. 2).The contents of erythrocytes and hemoglobin werewithin the physiological norms, indicating the absenceof anemia (Fig. 2). Compared to the control group, theblood of the experimental lambs that received starterfeeds with the MR and the OS had a slight increasein hemoglobin, namely by 2.6 (P > 0.1) and 4.7%(P < 0.05), respectively, and in erythrocytes, by 5.6 and11.1% (P < 0.05), respectively. This contributed to amore intensive metabolism. The contents of leukocyteswere almost identical, with a difference of 2.9 and 5.9%,respectively.Higher total protein in the serum of the experimentallambs indicated more intensive protein digestionand absorption of amino acids in the intestine, as29.738.5 39.7051015202530354045Live weight after 120 days, kg1 - control 2 - experimental 3 - experimental25.6234.4 35.610510152025303540Absolute weight gain, kg1 - control 2 - experimental 3 - experimental214287 297050100150200250300350Daily weight gain, g1 - control 2 - experimental 3 - experimental4.08 4.10 4.09012345Live weight at birth, kg1 - control 2 - experimental 3 - experimental25.6234.4 35.610510152025303540Absolute weight gain, kg1 - control 2 - experimental 3 - experimental25.6234.4 35.610510152025303540Absolute weight gain, kg1 - control 2 - experimental 3 - experimental25.6234.4 35.610510152025303540Absolute weight gain, kg1 - control 2 - experimental 3 - experimental25.6234.4 35.610510152025303540Absolute weight gain, kg1 - control 2 - experimental 3 - experimental190Marynich A.P. Foods and Raw Materials, 2022, vol. 10, no. 1, pp. 185–19410.2% (P < 0.05), respectively, indicating a better supplyof body cells with energy. Similar results were reportedby Khompodoeva and Pashtetskaya et al. [15, 16].Calcium was significantly higher in the blood serumof experimental lambs, namely by 7.8 (P < 0.05) and10.5% (P < 0.05) in the groups that received the MR andthe OS, respectively. A similar trend was observed in theamount of phosphorus: it was 7.5 (P < 0.05) and 14.9%(P < 0.01) higher in the experimental groups, comparedto the control. This was indicative of better saturation ofthe bone tissue and stronger bones.The control slaughter (Fig. 3) proved a possibility ofobtaining high-quality dietetic meat from lambs aged 4months.We established (Fig. 4) that starter feeds enrichedwith the milk replacer and the ORGANIC supplement,increased the slaughter weight by 36.5 and 42.05%(P ≤ 0.001) and slaughter yield by 2.50 and 2.96 abs.%,respectively, compared to the control.Next, we studied the morphological compositionof animal carcasses to assess meat productivity. Forthis, we deboned the carcasses and analyzed variousmeat characteristics, especially the meat coefficient (theratio of the weight of meat to the weight of bones andtendons) (Fig. 5).well as protein synthesis in the liver. This findingwas confirmed by the live weight gain indicators. Inparticular, total protein in the experimental groupsthat received the MR and the OS was 8.5 and 11.6%(P < 0.05) higher in comparison with the control group.Glucose contents were higher by 6.9 (P < 0.05) andFigure 2 Hematological and biochemical parameters of young sheep that received: 1 – standard feed (control); 2 – starter feed withthe whole milk replacer, 3 – starter feed with the ORGANIC supplement7.26.87.67.08.07.26.06.57.07.58.0Erythrocytes, Т/L Leukocytes, g/L1 - control 2 - experimental 3 - experimental91.293.695.58990919293949596Hemoglobin, g/L1 - control 2 - experimental 3 - experimental2.45 2.571.742.62 2.771.872.70 2.842.0000.51.01.52.02.53.0Glucose, mmol/L Calcium, mmol/L Phosphorus,mmol/L1 - control 2 - experimental 3 - experimental61.366.568.45658606264666870Total protein, g/L1 - control 2 - experimental 3 - experimental2.45 2.571.742.62 2.771.872.70 2.842.0000.51.01.52.02.53.0Glucose, mmol/L Calcium, mmol/L Phosphorus,mmol/L1 - control 2 - experimental 3 - experimental2.45 2.571.742.62 2.771.872.70 2.842.0000.51.01.52.02.53.0Glucose, mmol/L Calcium, mmol/L Phosphorus,mmol/L1 - control 2 - experimental 3 - experimental2.45 2.571.742.62 2.771.872.70 2.842.0000.51.01.52.02.53.0Glucose, mmol/L Calcium, mmol/L Phosphorus,mmol/L1 - control 2 - experimental 3 - experimental2.45 2.571.742.62 2.771.872.70 2.842.0000.51.01.52.02.53.0Glucose, mmol/L Calcium, mmol/L Phosphorus,mmol/L1 - control 2 - experimental 3 - experimentalFigure 3 Carcasses of young sheep191Marynich A.P. Foods and Raw Materials, 2022, vol. 10, no. 1, pp. 185–194The ratio of muscle, bone, and connective tissues inthe body of sheep affects the nutritional and biologicalvalue of carcasses. However, if sheep had different liveweight, the nutritional value of their carcasses can varygreatly [17].Apparently, higher feed intake and betterassimilation of nutrients in the experimental groupscontributed to a more uniform deposition of subcutaneousfat and the formation of muscle mass.We found maximum meat weight in the carcasses oflambs that received feed with the milk replacer and theORGANIC supplement, respectively. Particularly, theirmeat weight was 40.0 and 51.9% (P ≤ 0.001) higher thanin the control group, with a meat coefficient of 3.34 and3.57, respectively. Our data were consistent with thosereported by Khayitov and Dzhuraeva [18].Histological studies of the Longissimus dorsi muscleshowed better microstructural characteristics in themeat of experimental lambs (Table 5).The meat of young sheep from the experimentalgroups that received the MR and the OS had smallermuscle bundles, but it contained more fibers than theFigure 4 Slaughter characteristics of ram lambs that received: 1 – standard feed (control); 2 – starter feed with the whole milkreplacer, 3 – starter feed with the ORGANIC supplement; n = 329.713.73 14.0338.518.45 19.1539.7019.14 19.93020406080100120Preslaughterweight, kgChilled carcassweight, kgSlaughter weight,kg1 - control 2 - experimental 3 - experimental47.2449.7450.200102030405060708090100Slaughter yield, %1 - control 2 - experimental 3 - experimental47.2449.7450.200102030405060708090100Slaughter yield, %1 - control 2 - experimental 3 - experimental47.2449.7450.200102030405060708090100Slaughter yield, %2 - experimental 3 - experimental13.736.9 5.20 1.7018.459.40 7.28 2.1219.1410.117.902.210102030405060Chilledcarcassweight, kgHalf-carcassweight, kgMeat weight,kgBone weight,kg1 - control 2 - experimental 3 - experimental3.063.343.570102030405060708090100Meat coefficient1 - control 2 - experimental 3 - experimental47.2449.7450.200102030405060708090100Slaughter yield, %1 - control 2 - experimental 3 - experimental47.2449.7450.200102030405060708090100Slaughter yield, %1 - control 2 - experimental 3 - experimentalFigure 5 Morphological composition of lamb carcasses aged 4 months that received: 1 – standard feed (control); 2 – starter feedwith the whole milk replacer, 3 – starter feed with the ORGANIC supplement; n = 3meat of the control animals, namely by 8.45 pcs./1 mm2(2.1%) and 13.34 pcs./1 mm2 (3.3%), respectively.The marbling coefficient of meat in the group thatreceived the OS exceeded that of meat in the groupsfed on standard feed and the OS feed by 11.7 and 7.9%(P ≤ 0.05), respectively.The microstructural analysis of muscle tissuesamples (Fig. 6) showed that the Longissimus dorsimuscle of lambs had a greater number of muscle fibersof a smaller diameter with fatty layers, indicative of highnutritional and commercial qualities.The biological value is the main indicator of theproduct’s nutritional value.The chemical composition of muscle tissue largelydepends on fatness and productivity type (wool-andmeator other). In our study (Fig. 7), the muscle tissue ofthe experimental lambs in the groups fed on the MR andOS feeds contained less moisture (by 4.52–6.47 abs.%(Р ≤ 0.05)), but more dry matter (by 1.47–4.52 abs.%),fat (by 0.58–0.80 abs.%), and protein (by 0.87–3.67abs.% (Р ≤ 0.05)), compared to the control. Our datawere consistent with those of Bogatirevet et al. [19].192Marynich A.P. Foods and Raw Materials, 2022, vol. 10, no. 1, pp. 185–194Table 5 Microstructural analysis of the Longissimus dorsi muscle in sheep aged 4 months that received various diets (n = 3)Indicator GroupStandard feed (control) Starter feed with whole milk replacer(experiment)Starter feed with ORGANICsupplement (experiment)Number of muscle fibers, pcs. 401.33 ± 7.22 409.78 ± 7.38 414.67 ± 7.47Muscle fiber diameter, μm 28.45 ± 0.51 25.84 ± 0.46 25.34 ± 0.35*“Marbling” assessment, score 28.95 ± 0.52 29.99 ± 0.54 32.35 ± 0.58*Connective tissue, % 8.00 ± 0.14 7.60 ± 0.13 7.20 ± 0.11**Р ≤ 0.05; **Р ≤ 0.01; ***Р ≤ 0.001 Нужно указать критерий статистического анализа. Какой критерий – знают только авторы123a bc1 – muscle fibers; 2 – connective tissue; 3 – fatty interfiber and interfascicular inclusions (“marbling”)Figure 6 Histosection of the longissimus dorsi muscle tissue of young sheep (colored with hematoxylin-eosin, magnification ×500):а) group fed on standard feed (control); b) group fed on starter feed with whole milk replacer (experiment); c) group fed on starterfeed with ORGANIC supplement (experiment)Figure 7 Chemical composition of muscle tissue of young sheep that received a) – standard feed (control); b) – starter feed with thewhole milk replacer, c) – starter feed with the ORGANIC supplement; n = 371.828.540.9418.701 - controlMoisture, % Fat, %Ash, % Protein, %70.359.120.9619.572 - experimentalMoisture, % Fat, %Ash, % Protein, %67.309.340.9922.37Moisture, % Fat, %Ash, % Protein, %a b c67.309.340.9922.37Moisture, % Fat, %Ash, % Protein, %67.309.340.9922.37Moisture, % Fat, %Ash, % Protein, %193Marynich A.P. Foods and Raw Materials, 2022, vol. 10, no. 1, pp. 185–194rubles respectively. The level of profitability of lambproduction increased by 34.7 and 42.1%, respectively.The return on one ruble of feed supplement costsamounted to 10.9 and 21.7 rubles, respectively.CONCLUSIONIncluding starter feeds enriched with 5% of skimmedpowered milk as a whole milk replacer or 3% of theORGANIC feed supplement in the diet of sheep aged upto four months enhanced their nutritional value, namelymetabolic energy (by 4.7 and 6.6%), raw protein (by 19.8and 27.3%), lysine (by 23.7 and 18.6%), methionine +cystine (by 32.7%), and threonine (by 23.1 and 21.2%).By the age of four months, the lambs had an increase inlive weight (8.8 and 10.0 kg) and average daily weightgain (73.0 and 83.0 g). The supplements also improvedthe quality of meat, as well as feed efficiency (by 0.71and 0.98 energy feed units) and the profitability of lambproduction.CONTRIBUTIONThe authors were equally involved in writing themanuscript and are equally responsible for plagiarism.CONFLICT OF INTERESTThe authors declare no conflict of interest regardingthe publication of this article.Thus, the morphological and microstructural analysesof the longissimus dorsi muscle tissue revealedhigher quality indicators in the lamb fed on the OSfeed, compared to the groups that received standardfeed and the MR feed. Particularly, it had the largestnumber of muscle fibers of a smaller diameter, a highermarbling score, and a lower content of connective tissue.Therefore, the meat in the group fed on the OS feed wascharacterized as tender and juicy. The most nutritiousand valuable were those animal carcasses which had agreater content of muscle tissue, since connective tissuecontains fatty tissue that make meat a high-calorieproduct and give it a characteristic taste, color, andaroma.The economic analysis (Table 6) proved theefficiency of using starter feeds with the high-proteinmilk replacer of the ORGANIC supplement whengrowing wool-and-meat lambs up to 4 months of age.Particularly, the absolute increase in live weight oflambs in the experimental groups that received the MRand the OS feeds amounted to 8.8 and 10.0 kg or 34.27and 38.99% (Р ≤ 0.001), respectively.The additional costs of the milk replacer and theORGANIC feed supplement for the experimentalgroups were 161.3 and 96.3 rubles, respectively. Thesame selling price of 219.0 rubles per 1 kg of liveweight allowed for an extra profit of 1761.5 and 2091.5