Locusta migratoria extruded meal in young steers diet: evaluation of growth performance, blood indices and meat traits of Calves Kasakh white-headed breed

ABSTRACT

The article presented the data that confirm the efficiency of the extruded Locusta migratoria (ELM) meal used in feeding steers. The experiment was based on collecting locust, feeding steers and calculation of economic efficiency. One hundred steers of Kasakh white-headed breed were equally divided to 2 treatment groups, and fed either a basal ration (BR, Control group), or a ration containing complete feed supplemented with ELM at 10% (Test group). In the population under study, the live weight dynamics was observed, and the physiological state and haematological status were controlled. The steers’ meat productivity and meat quality were studied on the results of the control slaughter. Partial replacement of the feed with locust reduced the feed costs and contributed to an increase in profits per animal in Test group compared to the control animals, as well as in the beef production profitability.

KEYWORDS:

• Animal welfare
• beef
• cattle breeding
• insects
• profitability

Introduction

The increased population of our planet causes an enhanced demand for better food and will result in competition for arable land and other non-renewable resources in the future (Singh et al. 2017). Proteins of animal origin contained in milk, meat, fish, eggs and insects are very valuable sources of essential amino acids, but their production consumes a sufficient amount of non-renewable resources, including arable land, and has a negative impact on agroecology, for example, due to a considerable amount of harmful emissions (Flachowsky et al. 2017).

The competition for food is a major concern, as well as ongoing climate change, land degradation and water deficiency for creating sustainable food production systems (Heumesser et al. 2013). The growth in food demand will mainly occur in developing countries that have already faced many food safety challenges. However, additional feed needed for the predicted increase in demand for animal products, if they are provided with food grains and legumes, will further aggravate the food security in these countries (Makkar 2018).

So, due to different ways to use soybean and its by-products, the growing global demand for soybeans, including in the diet of several types of livestock, is forcing the industry to look for alternative protein sources (Allegretti et al. 2017). Based on numerous studies, the meal from insects belonging to the orders of Diptera (black soldier fly and house fly), Coleoptera (mealworms), Megadrilacea (earthworms), Lepidoptera (silk worm and cirinaforda) and Orthoptera (grasshoppers, locusts and crickets) can be fruitfully used as a high-protein ingredient in feed production (Al-Qazzaz and Ismail 2016; Bovera et al. 2016; Jin et al. 2016; Khan et al. 2016; Poelaert et al. 2016; Jayanegara et al. 2017; Brede et al. 2018; Cullere et al. 2018; Fanatico et al. 2018; Hall et al. 2018; Kim et al. 2018; Mancini et al. 2018; Secci et al. 2018; Spranghers et al. 2018; Biasato et al. 2018, 2019; Gasco et al. 2019). To date, information on their nutritional composition and biological assessment has been collected, and the data obtained has been compared with similar characteristics of soybean meal and fish meal (Makkar et al. 2014; Jozefiak et al. 2016; Jozefiak and Engberg 2017; Khan 2018).

Seasonal locust plague in warm regions of Russia, Uzbekistan and Kazakhstan yield billions of losses not only because of the destroyed crops and pastures, but also due to the investment of huge funds to fight it, i.e. the agricultural aircrafts, purchase and rent of special equipment, human resources etc. All these are carried out in order to save crops for fattening livestock for obtaining animal proteins of meat, dairy and poultry products (Flachowsky et al. 2018). However, attention is missing the fact that locusts themselves are far superior in nutrition to traditional sources of protein. Every year, to meet the needs of fodder production, protein in the form of fish meal is produced and consumed worldwide (in Argentina, Peru, Chile, China and many other countries) for millions of dollars (van Huis 2013). The current catastrophic shortage of protein in fodder does not allow obtaining high-quality animal products. A paradoxical situation arises, i.e. destroying an excellent source of protein by treating water bodies, soil, and vegetation with toxic substance causes irreversible damage to the environment and leads to their accumulation in the environment. Recently, due to global climate change on the planet, the number of locusts has been increasing and its habitat has been expanding (Cressman 2013; Popova et al. 2016).

It should be noted that, on the basis of a research study conducted by Verbeke et al. (2015), agricultural enterprises of various forms of ownership are generally positively inclined to implement such an unconventional approach to the use of insects as a fodder ingredient for animals. So, according to monitoring conducted by Verbeke et al. (2015), the perceived benefits of using insects in animal feed are mainly due to a decrease in dependence on protein imports and better valorization of organic waste. To date, around the world there have been established more than 25 enterprises that produce and sell feeds from Black soldier fly (Hermetiaillucens), Housefly (Muscadomestica), Mealworm (Tenebriomolitor), Housecricket (Achetadomesticus) and Lessermealworm (Alphitobiusdiaperinus) (Colombia, South Africa, the Netherlands, Spain, Canada, Vietnam, Malaysia, France, USA, Ireland, Chile, Sweden, Thailand, Germany, Poland, Lithuania, Norway, Great Britain, Bulgaria, Tunisia, Belgium, Singapore and China).

Locusta migratoria(LM) is considered to be a seasonal disaster of the southern territories of the Eurasian continent, so, the study of its efficiency in feeding farm animals can be a real way out not only for the production of cheap high-protein feed, but also for agroecology as a whole. Given the relevance of the topic chosen in connection with the vastness of the habitats of this insect species and high annual cost of their destruction, the purpose of the scientific research was a comparative study of the efficiency of LM insects of the Acrididae family being used in fattening steers. To reduce the risks above, the authors proposed the extrusion method for processing LM, which will not only ensure its microbiological safety, eliminate specific aromas and neutralize the potential presence of allergens, but also increase the availability of nutrients for the animal's body and thereby the degree of feed conversion in meat products. In accordance with the purpose set, the following tasks were solved:

• study the chemical composition and nutritional value of LM and ELM;

• identify the ELM effect on the digestibility and nutrient use of the diet;

• analyse the dynamics of morphological and biochemical blood parameters under the influence of the ELM;

• study the ELM effect on the linear and weight growth of Test steers;

• identify the features of the meat production development; assess the slaughter parameters of steers and beef quality, with the ELM being included into their diet; and

• give an economic assessment of the ELM effectiveness in steers raising.

Materials and methods

Development of an ELM Test Batch

Locusts were collected using a Raptor unit (Russia) mounted on an MTZ type tractor (Belarus). The vacuum obtained during the rotation of the unit’s blades was directed to special rollers with slots that rolled along the surface of the soil contaminated with locusts. Locusts were pressed into the slots of the rolls and sent for laying in sacks by vacuum. The locust packers (for 12 sacks) on the Raptor were mounted on a transport cart that clings to the same tractor. Getting into the compartment, locusts were crushed, dried and processed under pressure at high temperature. So any microbes were destroyed. The performance of the unit depended on the density of locusts landing on 1m² and speed of the unit. So, at a speed of 10 km/h, 5–7 tons of environmentally friendly meal was obtained per shift. The locust is known to go to plantings in collective flocks in the cross section of 1.5–2 km; the weight of such a flock can reach 30 thousand tons. The technology developed by Abramovskikh et al. (2018) allows catching it exactly at that moment, while it is just walking across the field, and is not suitable for the locust that has already taken wing; the collection should be started when the insects are 2–3 weeks old. Then the insect meal obtained was extruded. Extrusion processing makes it possible to increase the nutritional value of the supplement and neutralize harmful impurities (Martins et al. 2018; Ottoboni et al. 2018). The chemical composition and nutritional value of the feed extruded was studied using standard methods for analysing feed for farm animals. The amino acid composition was determined by capillary electrophoresis on the system ‘Capel-105M’ (Lumeks, Russia).

Experimental livestock, the experiment

The experiment on fattening steers was conducted on young Kazakh white-headed breed in the conditions of the Open Joint-Stock Company (OJSC) Shurupovskoe industrial complex, the Volgograd region. Since 2009, OJSC Shurupovskoye has had the status of a pedigree reproducer for this breed of beef cattle. The production capacity of the enterprise enables having up to 10,000 animals at the fattening site. Currently, about 5,000 animals are served by farm specialists, 750 of them are highly valued breeding cows. The company’s land is more than 8,000 hectares in area, which makes it possible to fully provide livestock with high-quality fodder. In feeding animals, only natural food of their own production is used. To conduct the analog experiment, 2 groups of steers aged 12 months were formed, 50 animals each. The analog principle for animals meant similar origin, breed, age and live weight taken into account. The duration of the scientific and business experiment was 120 days from 12 to 15 months of age. The steers in Control group received the basic ration (BR), and the test steers were fed with the ration, containing complete feed supplemented with ELM at 10%. The keeping and feeding procedures for all the experimental steers were similar. The feeding rations were made up taking into account the age, body weight and average daily gains. In order to determine the feed consumption, on a monthly basis for 2 adjacent days, control feedings were carried out considering the residues. The energy nutritional value of 1 kg of feed consumed was calculated in the physiological experiment (by the direct method) that involved the following procedure: during the experiment, Test animals received accurately counted amount of feed, whose composition was previously analysed. Then, the amount of feces excreted for the experiment was accurately taken into account, and its chemical composition was determined. The amounts of consumed and excreted nutrients were calculated based on the data on the weight and chemical composition of the feed consumed and feces excreted. The amount of digested substances was identified by their difference. The digestibility coefficient was found by the formula$DC={\displaystyle \frac{n-v}{n}\times 100}$, where n is the amount of the nutrients consumed, and v is the amount of the nutrients excreted.

The steers were kept in the premises in groups with free access to the walking yards on bed being not changed. Feeding and watering of animals was carried out in walking yards from feeding troughs and drinking bowls placed along the perimeter of the courtyards (Figure 1).

Figure 1. Experimental steers in a walking yard.

The dynamics of the body weight was registered in individual weighing when setting on the experiment at 12 months of age, and then at 13, 14 and 15 months in the morning before feeding. Based on the data obtained, the overall and average daily weight gains were calculated. The linear growth of young stock was studied by measuring exterior parameters; their values served as a basis for the indices of the body built being calculated.

Monitoring the physiological state of the experimental steers was carried out by measuring body temperature, pulse and respiration rates and studying hematological parameters. The body temperature was measured rectally with a veterinary thermometer made of whole glass. The pulse rate was counted by the imposition of a finger on the femoral artery, the frequency of breathing in terms of the movement of the chest by the pushes of exhaled air felt by the palm located at the nostrils.

Blood for the study was taken from the jugular vein in the morning before feeding. The morphological composition and biochemical blood parameters were performed on an automatic hematology analyser URIT-3020 Vet Plus and on a semi-automatic biochemical analyser URIT-800Vet (China). The ethological features that are the daily rhythm of the basic behavioural features of an animal were determined by the method of timekeeping and visual observations using individual and group registration methods.

Experiments were performed in accordance with the Guide for the care and use of laboratory animals (Committee for the Update of the Guide for the Care and Use of Laboratory Animals et al. 2011). And the use of experimental animals completely observed the local animal welfare laws and policies. The current study is compliance with ethical standards. The authors confirm that the cattle owner (Maksim Vyacheslavovich Shkarupin, Managing Director of OJSC Shurupovskoye) provided written consent for the use of his animals in this study.

Control slaughter and meat quality analysis

The meat production of steers and meat quality were studied on the results of control slaughter of 15 animals at 15 months of age from each group. The control slaughter and boning of carcasses were conducted in industrial conditions at the Volgograd meat processing plant. The pre-slaughter live weight, weight of hot and chilled carcasses, internal slaughter fat, internal organs (lungs, heart, kidneys, liver and spleen) and suet, slaughter weight and slaughter yield were determined; the total and relative carcass yield were calculated. The morphological composition of the carcasses was studied by cutting them into cuts according to the GOST 31797–2012 ‘Meat. Dressing of beef into cuts. Specifications.’ To determine the quality traits, average samples of flesh and longissimus muscle were selected. The study was conducted according to the methods approved, i.e. moisture content according to the GOST R 51479-99; protein content by the total Kjeldahl nitrogen method (GOST 25011-81); fat content by the Soxhlet extraction of an ether-dried sample (GOST 23042-86); mineral content (ash) by the dry mineralization of samples in a muffle furnace (GOST 31727-2012); the content of hydroxyproline according to the Neumann and Logan method (GOST 23041-2015); tryptophan content according to the Grahame-Smith method; moisture binding capacity by planimetric press method (Grau& Hamm) in the Volovinskaya-Kelman modification (1962); ability to cook down by determining the weight of meat samples before and after cooking; pH value by potentiometric method using a pH meter; and organoleptic evaluation according to the GOST 9959-2015. The protein-quality parameter (PQP) was calculated as the ratio between tryptophan and hydroxyproline, i.e. the ratio between amino acids, reflecting the content of high-grade proteins in meat, and the amino acid that characterizes the amount of connective tissue.

Calculation of economic efficiency

The cost-effectiveness of the beef production was counted based on the annual actual and intrafarm economic effect and according to Minakov (2014) using the following formulas:(1) $\mathrm{Prime}\mathrm{cost}\mathrm{of}1\mathrm{kg}\mathrm{of}\mathrm{gain},\text{€}={\displaystyle \frac{\mathrm{Farm}\mathrm{inputs},\text{€}\mathrm{per}\mathrm{animal}}{\mathrm{Total}\mathrm{gain},\mathrm{kg}}}$(1) (2) $\mathrm{Beef}\mathrm{sales}\mathrm{proceeds},\text{€}=\mathrm{Total}\mathrm{gain},\mathrm{kg}\times \mathrm{Market}\mathrm{value}\mathrm{of}\mathrm{beef},\text{€}\mathrm{per}\mathrm{kg}$(2) (3) $\mathrm{Profit},\text{€}=\mathrm{Beef}\mathrm{sales}\mathrm{proceeds},\text{€}\text{-}\mathrm{Farm}\mathrm{inputs},\text{€}\mathrm{per}\mathrm{animal}$(3) (4) $\mathrm{Profitability}\mathrm{level},\text{\%}={\displaystyle \frac{\mathrm{Profit},\text{€}}{\mathrm{Farm}\mathrm{inputs},\text{€}\mathrm{per}\mathrm{animal}}\times 100\text{\%}}$(4)

The mean values were calculated as economic parameters in spring of 2019, the RUR/EUR exchange rate was 73.0.

Statistical analysis

The data on different variables, obtained from the experiment, were statistically analysed by Statistica 10 package (StatSoft Inc.). The significance of differences between the indices was determined using the criteria of nonparametric statistics for the linked populations (differences with P<0.05 were considered significant: ***P<0.001; **P<0.01; *P<0.05; ns = not significant at P>0.05). Student's t-test was applied for the statistical analysis(Johnson and Bhattacharyya 2010). The mean of a set of measurements was calculated according to the formula:(5) $\overline{x}={\displaystyle \frac{\sum _{i=1}^n{x}_i}{n},}$(5) where $\overline{x}$ is a mean value; $\sum _{i=1}^n{x}_i$ is the sum of all x_i withi ranging from 1 to n, n is the number of measurements. The residual variation is expressed as a root mean square error (r.m.s.e.):(6) $\sigma =\sqrt{{\displaystyle \frac{\sum _{i=1}^n{(x_i-\overline{x})}^2}{n-1}}}.$(6)

The standard error of mean (s.e.m.) was calculated using the formula:(7) $s.e.m.(\overline{x})={\displaystyle \frac{\sigma }{\sqrt{n}}.}$(7) The reliability of a sample difference (Student’s t-distribution) was estimated by the test of the difference validity, which is the ratio between the sample difference and the non-sampling error. The test of the difference validity was determined by the formula:(8) $t={\displaystyle \frac{\overline{x_1}-\overline{x_2}}{\sqrt{s.e.m{.}_1^2+s.e.m{.}_2^2}}\ge t_{st.}(d.f.=n_1+n_2-2),}$(8) where t is a Student’s t-distribution; $\overline{x_1}-\overline{x_2}$ is the difference of the sample mean measurements; $\sqrt{s.e.m{.}_1^2+s.e.m{.}_2^2}$ is the sample difference error; s.e.m.₁and s.e.m.₂ are the a nonsampling errors of the compared sample statistics; t_st is the standard criterion according to the t-Table for the probability threshold preset depending on degrees of freedom; n₁ and n₂ are the numbers of measurements in the samples compared; d.f. is the degrees of freedom for the difference of two mean measurements.

Results and discussion

The composition of the Locusta migratoria that lives in the collection area

As reported earlier (Clarkson et al. 2018), compositional data concerning locusts is scarce and exact values are highly variable depending on species, habitat, diet, metamorphic stage, and processing method. Orthopteran species contain high amounts of fat averaging around 13% (dry weight basis). Moreover, insects are particularly noted for their high protein content. Orthopteran species can range from 50% to 65% protein for Locusta migratoria. So, locusts sourced from Dunedin, New Zealand, contained a high amount of protein (50.79% dry weight). In our study the content of protein in the collected locusts averaged 57.2% and fat 14.3% (dry weight). Meal was dried to a moisture content of 4%. So, the locust protein content was several times higher than in raw meat. In order to study the full-value of proteins in meal from insects, an amino acid analysis of the samples was carried out; its results are in Figure 2.

Figure 2. Amino acid composition of locust meal (ELM = extruded Locusta migratoria, LM = Locusta migratoria), mg per 100 g.

However, some insects are rich in protein and minerals, but cannot be used directly because they secrete toxins or harmful minerals (Al-Qazzaz and Ismail 2016). To reduce the risks above, we propose the extrusion method for processing LM, which will not only ensure its microbiological safety, eliminate specific aromas and neutralize the potential presence of allergens, but also increase the availability of nutrients for the animal's body and thereby the degree of feed conversion in meat products. We also analyzsed the chemical composition of the ELM. The protein content averaged 53.5% and fat 11.4%. After extrusion, the moisture content decreased to 2%.

Feed nutrients Intake and animal growth rates

As Jayanegara et al. (2017) showed, insects are among potential protein sources for feeding of livestock. We have established similar results. So, for the entire period of the experiment (in the total amount of feed), steers in Test group consumed more dry matter by 12.97% (P<0.001), crude fat by 12.61% (P<0.05), raw protein by 13.42% (P<0.01) and crude fibre by 13.00% (P<0.01), compared with their peers in Control group. More energy feed units were also consumed by the steers in Test group by 314.4 ECU (P<0.001) and the exchange energy by 3144 MJ (P<0.001). Similar results found by Jin et al. (2016): as dried mealworm level was increased, nitrogen retention and digestibility of dry matter as well as crude protein were linearly increased (in piglets’ diet).

At the age of 13 months, the live weight values of the steers in Test group were higher than those of their peers in Control group by 4.1 kg or 1.11% (P<0.05), 14 months by 4.4 kg or 1.10% (P<0.01) and 15 months by 6.8 kg or 1.58% (P<0.01). In order to more accurately characterize the changes in the magnitude of the growing weight of Test animals at various age periods, the average daily gains were determined (Figure 3(A,B)). Test steers in comparison with their peers in Control group, the average daily gain at the age of 13–14 months was higher by 78.4 g or 7.57% (P<0.01) and 14–15 months by 107.3 g or 10.94% (P<0.01). The highest rates were observed in the livestock aged 13–14 months in both groups. Over the entire period of the experiment, the parameter under study was high and ranged from 908.4–1141.7 g in animals of all groups. At the same time, by the age of 14 months, the steers in both groups had reached 400 kg in live weight.

Figure 3. Growth rates of Test steers: (A) is the live weight, kg; (B) is the average daily gain, g.

At the age of 15 months, the steers in Test group surpassed their peers in Control one in terms of almost all measurements. So, their advantage was the following: height at withers by 1.76%, height at hips by 0.08%, width of chest by 4.5%, chest depth by 3.57%, chest girth by 1.21%, oblique body length by 0.26% and pastern girth by 11.70%. The calculated body indices of Test animals are presented in Figure 4.

Figure 4. Indices of body built of Test steers at 15 months of age, %.

As seen from the data above, animals fed with the ELM were distinguished by a wider and deeper body, had higher indices of blockiness, thorax and pelvis-thorax, which characterized good development of the meat traits of animals. However, in accordance with Jayanegara et al. (2017), insect’s digestibility is rather low and may limit their utilization. Certain treatments or processing methods to remove the exoskeleton fraction or chitin may be required to elevate the feeding values of insect meals. Thus, the extrusion method may be considered as method to resolve this trouble (Ottoboni et al. 2018).

Morphological and biochemical blood parameters of animals

Jin et al. (2016) reported that addition of dried mealworm in weaning pigs’ diet showed improvements in the blood indices. In our study, the animals in Test group were noted for a more intensive metabolism, which was confirmed by the data on the content of red blood cells, haemoglobin and protein in their blood compared to Control group (Table 1). So, there were registered more red blood cells by 12.6% (P<0.001), haemoglobin by 3.8% (P<0.01) and total protein by 3.3% (P<0.01), including albumin by 2.7% (P<0.05).

Table 1. Hematological blood parameters of steers at the age of 15 months, n=50 (mean ± s.e.m.).

Parameter	Control	Test
Red blood cells, 10^12 per L	6.42 ± 0.14	7.23 ± 0.19***
White blood cells, 10^9 per L	7.15 ± 0.63	7.08 ± 0.72
Haemoglobin, g per L	115.3 ± 1.1	119.7 ± 0.9**
Total protein, g per L	77.9 ± 0.7	80.5 ± 0.6**
Albumin, g per L	37.2 ± 0.4	38.2 ± 0.2*
Globulin, g per L	40.7 ± 0.6	42.3 ± 0.4*

*** = P< 0.001; ** = P< 0.01; * = P< 0.05 compared with data on the Control group.

Indices of Control slaughter and beef quality

Makkar et al. (2014) have described the most popular fields of using black soldier fly larvae, housefly maggots, mealworms, locusts, grasshoppers and crickets (as animal feed in pig breeding, poultry, fish breeding as well as in other species). However, for ruminants they have written: ‘To the best of our knowledge no studies are available’. They also wrote that ‘future higher availability of insect meals would provide impetus to the studies on evaluation of these alternate feed resources in ruminant livestock as well’. The situation has changed only slightly in the recent five years (Gasco et al. 2019).

In our study, the control slaughter (Table 2) found that the steers in Test group were characterized by higher slaughter indices. So, their carcasses were heavier in comparison with ones from their peers in Control group. The superiority in terms of the pre-slaughter live weight was 5.8 kg or 1.41% (P<0.05) and weight of hot carcass 5.6 kg or 2.75% (P<0.05). With respect to the slaughter weight, the steers in Test group exceeded the Control young stock by 5.4 kg or 2.53% (P<0.05). The weight of the internal fat was higher in animals of Control group by 0.5 or 5.05% (P<0.05).

Table 2. Results of the control slaughter of steers at the age of 15 months, n=15 (mean ± s.e.m.).

Parameter	Control	Test
Pre-slaughter live weight, kg	411.2 ± 1.8	417.0 ± 1.6*
Weight of hot carcass, kg	203.5 ± 1.7	209.1 ± 1.9*
Fresh carcass yield, %	49.5	50.1
Weight of internal fat, kg	9.9 ± 0.2	9.4 ± 0.1*
Internalfatyield, %	2.4	2.3
Slaughter weight, kg	213.3 ± 2.0	218.7 ± 1.6*
Slaughter yield, %	51.9	52.4
Weight of chilled carcass, kg	201.9 ± 1.5	207.1 ± 1.9*
Flesh weight, kg	157.8 ± 2.5	165.5 ± 2.2*
Flesh yield, %	78.2	79.9
Weight of bones, kg	33.3 ± 0.4	31.7 ± 0.6*
Bone yield, %	16.5	15.3
Weight of tendons and cartilage, kg	11.1 ± 0.5	9.9 ± 0.3*
Tendons and cartilage yield, %	5.5	4.8
Fleshing index	4.7	5.2

*** = P< 0.001; ** = P< 0.01; * = P< 0.05 compared with data on the Control group.

Boning of the carcasses of Test steers (Figure 5) carried out in a boning shop of the meat processing plant showed that the weight of flesh from Test group steers was higher than in Control group by 7.7 kg or 4.88% (P<0.05), weight of bones by 1.6 kg or 4.80% (P<0.05), weight of cartilage and tendons by 1.2 kg or 10.81% (P<0.05) and fleshing index by 10.64%.

Figure 5. Morphological composition of the carcasses: (A) Control and (B) Test.

The internal organs are also an element of the cattle meat production. Their competent utilization for culinary purposes can increase the economic efficiency and profitability of the industry as a whole. In this regard, the internal organs of Test steers were weighed after slaughtering at the meat processing plant. Their study showed that the internal organs of both groups were well developed. Despite the positive trend established in steers of Test group in comparison with the Control, the level of differences was unreliable. The highest superiority of the steers of Test group over the Control peers was observed in terms of the weight of liver by 0.10 kg or 1.96%, spleen by 0.07 kg or 6.73% and tongue by 0.08 kg or 4.30%. The veterinary and sanitary examinations of the internal organs from Test steers showed that no pathological changes, signs of infectious or invasive diseases were found; all by-products were recognized as suitable for sale without any restrictions.

The results of the chemical analysis of the average sample of meat and minced meat presented in Table 3 indicate that, in general, the meat obtained was physiologically mature both in Control and Test groups. This was evidenced by the ratio between the dry matter and moisture in it that averaged 0.45–0.47:1. Despite the higher moisture content (by 1.28%, P<0.001) in meat of Test group steers, it contained less fat (by 1.65%, P<0.001); the beef was leaner; and there was found superiority in protein (by 0.38%, P<0.05). Different fat content in Test carcass flesh affected the energy value of the beef produced. According to this parameter, Control steers exceeded their peers in Test group by 5.94%. The PQP of meat from Test steers was higher than from Control ones (6.32 against 5.80, respectively) by 8.97%.

Table 3. Chemical composition of the average sample of carcass flesh (n=15), % (mean ± s.e.m.).

Parameter	Control	Test
Moisture	67.80 ± 0.21	69.08 ± 0.27***
Dry matter	32.20 ± 0.19	30.92 ± 0.28***
incl. protein	18.04 ± 0.14	18.42 ± 0.11*
fat	13.10 ± 0.11	11.45 ± 0.16***
ash	1.06 ± 0.04	1.05 ± 0.05^ns
Fat and protein ratio	0.73:1	0.62:1
Energy value of 1 kg of flesh, MJ	9.42	8.86

*** = P< 0.001; ** = P< 0.01; * = P< 0.05 compared with data on the Control group.

Cost effectiveness

Le Gall et al. (2019) showed that the red locust can compete with livestock for forage. In South Africa from 1933 to 1935, red locust damage to grazing areas for sheep and cattle, and to maize and sugar cane was valued at £20, 000 (over a million USD today); an additional £40,000 was lost due to decrease in animal product outputs through arsenic poisoning used for locust control. Northern and northeastern China is one of the most important grassland-based animal husbandry areas for the country (Li et al. 2008) and O. asiaticus and other grasshoppers compete with sheep and cattle for forage Accordingly, locusts are ranked as one of the most serious pests due to its capacity to devastate grassland productivity (China Ministry of Agriculture 2012) and the country has implemented an ongoing management programme including pesticides, biopesticides, and chickens as locust predators (Xu et al. 2014; Zhang and Hunter 2017). However, inclusion of ELM instead of a part of the feed in the rations of steers of the Kazakh white-headed breed contributed to an increase in profits per animal compared to animals in Control group by 8.3EUR for the whole period of the experiment. The profitability level of the beef production was higher in Test group compared to Control one by 9.5%. Thus, economic calculations showed that the use of ELM for fattening steers is expedient (Table 4).

Table 4. Economic efficiency of beef production.

Parameter	Control	Test
Live weight at the beginning of the experiment, kg	340.5 ± 1.47	340.2 ± 1.95^ns
Live weight at the end of the experiment, kg	429.6 ± 1.88	436.4 ± 0.96**
Total gain, kg	89.1 ± 1.42	96.2 ± 1.13***
Farm inputs for growing of eachanimal for the experiment, EUR	87.0	87.0
Prime cost of 1 kg of total gain, EUR	0.98	0.90
Beef sales proceeds, EUR	103.7	112.0
Profit,EUR	16.7	25.0
Profitability level, %	19.2	28.7

*** = P< 0.001; ** = P< 0.01; * = P< 0.05 compared with data on the Control group.

The average values calculated as economic indicators up to spring 2019.

The RUR/EUR exchange rate of 73.0.

Conclusion

So, locust management matters for food security for a substantial number of people globally. Although understanding the grassland–locust–livestock system can inform solutions to pressing food security and livelihood issues, it also provides a heuristic framework for dissecting the pathways that connect human and ecological systems over large spatial distances (Cease et al. 2015). Based on the study of the chemical composition and nutritional value of ELM, its effect on the digestibility and nutrient utilization of the diet, dynamics of morphological and biochemical blood parameters, linear and weight growth of Test steers, characteristics of meat production development, assessment of slaughter parameters of steers and beef quality, the ELM feasibility in fattening steers was justified, and in conclusion, the economic ELM effectiveness was assessed. Humans are not passive players in their relationship with locusts. To effectively integrate land-use into management programmes, important data on locust biology, such as nutritional preference and thermobiology, remain to be collected, particularly for non-model locust species, for which the expressions of density-dependent phase polyphenism in not well-understood (Song 2011).

Animal welfare statement

The authors confirm that they have followed EU standards for the protection of animals used for scientific purposes and feed legislation.

Experiments were performed in accordance with the Guide for the care and use of laboratory animals (Committee for the Update of the Guide for the Care and Use of Laboratory Animals et al. 2011). And the use of experimental animals completely observed the local animal welfare laws and policies. The authors confirm that the cattle owner (Maksim Vyacheslavovich Shkarupin, Managing Director of OJSC Shurupovskoye) provided written consent for the use of his animals in this study.

Author contributions

Study conception and design was done by IFG, MIS, and NIM; Methodology was done by YuVS; Measurements and Acquisition was done by VSG, AAM, and EYuB; Analysis of data was done by EYuA and SAB; and Interpretation of data and drafting of manuscript was done by IFG, EYuA, and PSAC.

Acknowledgements

The authors are grateful to the Ministry of Science and Higher Education of the Russian Federation for the financial support in the implementation of this research according to the state assignment of NIIMMP.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability

All data generated or analysed during this study are included in this published article. The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

Additional information

Funding

This work was supported by the Ministry of Education and Science of the Russian Federation.