Comparative evaluation of dairy productivity of cows different lines in the conditions of the Orel region

Introduction. The Orel region, a producer of high-quality food products, has significant unrealized potential and many competitive assets, which include favorable natural and climatic conditions, a solid level of transport and energy infrastructure, unrestricted production capacity, and qualified personnel [1].

In order to realize these competitive advantages, it is vital to quickly modernize and advance the production of scientific proposals to increase the productivity of the dairy herd and develop the technology of milk production, which will allow the region to take its rightful place in the food market [2, 3].

Concerning the dairy subcomplex, the solution lies in recognizing the potential for productivity and quality of dairy products, including identification of the most promising lines of dairy cattle [4, 5].

Over the past decades, the genetic potential of cattle milk production has grown in the Russian Federation. This is due to the effective use of the world's genetic resources, in particular, such lines of the Holstein breed as Vis Back Ideal, Montviс Chieftain and Reflection Sovereign, which today, in the conditions of the breeding farms of the Orel region, have the highest milk yield and a set of economically useful qualities [6-8].

The purpose of this work was to study the milk productivity of the modern breeding stock of dairy cows of the main lines bred in the Orel region using the example of the breeding reproducer "ES "Streletskoye".

Materials and methods. The research was conducted in a black-and-white pedigree reproducer "ES "Streletskoye" – a branch of the Federal State Budgetary Scientific Institution "Federal Scientific Center of Legumes and Groat Crops" of the Orel District of the Orel Region. This farm is common for the Orel region in terms of housing conditions, the feeding of cows, and the technology of milk production. The rations of feeding the lactating cows on the farm were in accordance with zootechnical standards.

"ES "Streletskoye" specializes in the production of milk and pedigree cattle. The main lines of bulls bred on the farm are Vis Back Ideal 1013415, Montviс Chieftain 95679, and Reflection Sovereign 198998.

The object of research was Holsteinized black-and-white cows. The studies were carried out in accordance with the methods of zootechnical experiments [9].

The milk productivity of animals was assessed in accordance with GOST 2680986 "Milk and dairy products". Acceptance rules, sampling methods, and preparation of samples for analysis [10] with subsequent calculation of the amount of milk fat (AMF) and the amount of milk protein (AMP). The live weight of cows was determined by weighing 2-5 months after calving in accordance with the "Procedure and conditions for assessing pedigree cattle of dairy and milk-and-meat productivity" [11].

The milk yield ratio was determined by the ratio of milk yield per lactation to the live weight of a cow, showing the amount of milk produced per 100 kg of its weight.

Biometric processing of the results of the experiment was carried out using a personal computer in Microsoft Excel. The arithmetic mean, the arithmetic mean error, the correlation (r), the criteria for the reliability of the difference between the groups (t d ) according to the method of G.F. Lakin [12].

Results . The results of the analysis of the productivity of first-calf heifers of the main lines for 305 days of lactation are presented in Table 1.

Table 1 – Productivity of first-calf heifers of the main lines for 305 days of lactation

Bull line	n	Live weight, kg	Milk yield in 305 days of lactation, kg	Milk production coefficient
Vis Back Ideal	161	554±2.6	4906±48	886±11.5
Montviс Chieftain	33	546±7.2	6149±20***	1126±22.2***
Reflection Sovereign	108	555±5.2	6982±45***	1258±18.6***

Notes: *** – Р ≤ 0.001.

The data presented in Table 1 indicate that the milk yield of first-calf heifers of the Montviс Chieftain line, as well as of the Reflection Sovereign line, exceeded the milk productivity of first-calf heifers of the Vis Back Ideal line by 25.3 and 42.3%, respectively (P≤0.001). On the other hand, first-calf heifers of the Reflection Sovereign line significantly exceeded the milk yield of first-calf heifers of the Montviс Chieftain line by 13.6% (P≤0.001).

The milk production rates of first-calf heifers were generally in line with the differences found for milk yield in 305 days of the first lactation. Thus, the milk production coefficients of first-calf heifers of the Montviс Chieftain and Reflection Sovereign lines exceeded the indicator of the Vis Back Ideal line by 27.1% and 42.0% (P ≤ 0.001). In turn, Reflection Sovereign first-calf heifers also exceeded first-calf heifers of the Montviс Chieftain line by 11.7% (P ≤ 0.001).

Regarding the live weight of first-calf heifers, no significant differences were found between the studied lines.

The main regularity resulting from the materials presented in Table 1, should be considered the superiority in milk yield for 305 days of lactation of first-calf heifers of the Reflection Sovereign line over similar indicators of first-calf heifers of the Vis Back Ideal and Montviс Chieftain lines. In turn, the results of the milk yield of the Montviс Chieftain line significantly exceeded the results of the Vis Back Ideal line. Similar results were obtained with regard to the milk production coefficients of first-calf heifers of the studied lines.

As follows from the results of the studies presented in Table 2, the trends established in relation to the milk productivity of first-calf heifers, in general, were confirmed by the results of the second lactation.

Table 2 – Productivity of cows of the main lines for 305 days of second lactation

Bull line	n	Live weight, kg	Milk yield in 305 days of lactation, kg	Milk production coefficient
Vis Back Ideal	128	577±5.5	5308±68	920±10.2
Montviс Chieftain	33	588±4.3	6133±20***	1043±20.0***
Reflection Sovereign	50	580±6.8	7008±65***	1208±20.6***

Notes: *** – Р ≤ 0.001.

Thus, under the conditions of the "ES "Streletskoye" breeding farm, the milk yield in 305 days of the second lactation of cows of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the milk yield of the Vis Back Ideal cows by 15.5% and 32.0% (P≤0.001). In turn, the Reflection Sovereign cows significantly exceeded the Montviс Chieftain cows in this indicator by 14.3% (P≤0.001). Similarly, in terms of the milk production coefficient, the cows of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the Vis Back Ideal cows by 13.4% and 31.3% (P≤0.001). In addition, a significant superiority was shown in relation to the milk production coefficient of Reflection Sovereign cows over Montviс Chieftain cows by 15.8% (P≤0.001).

The live weight of cows of the main lines for the second lactation did not have significant differences.

The regularities characterizing the productivity of cows of the main lines for 305 days of the third lactation, in general, were also consistent with the results of the first and second lactations (Table 3). At the same time, the milk yield in 305 days of the third lactation of cows of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the milk yield of the Vis Back Ideal cows by 23.0% and 40.4% (P≤0.001). In turn, the Reflection Sovereign cows significantly exceeded the Montviс Chieftain cows in this indicator by 14.1% (P≤0.001). In terms of milk production, the cows of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the Vis Back Ideal cows by 18.4% and 38.7% (P≤0.001). In addition, a significant superiority was shown in relation to the milk production coefficient of Reflection Sovereign cows over Montviс Chieftain cows by 17.2% (P≤0.001).

Table 3 – Productivity of cows of the main lines for 305 days of third lactation

Bull line	n	Live weight, kg	Milk yield in 305 days of lactation, kg	Milk production coefficient
Vis Back Ideal	72	597±6.7	5027±64	842±16.1
Montviс Chieftain	21	620±8.4*	6183±24***	997±22.4***
Reflection Sovereign	33	604±5.8	7057±90***	1168±21.7***

Notes: *** – Р ≤ 0.001; * – Р ≤ 0.05.

It should be noted that the indicators of the live weight of cows of the main lines for the third lactation had some differences. Therefore, the live weight of cows of the Montviс Chieftain line for the period under review significantly exceeded that of the cows of the Vis Back Ideal line by 3.8% (P≤0.05).

At the next stage of the study, we studied the characteristics of the fat and protein composition of milk of the main lines in different periods of their productive use.

The hereditary characteristics of bulls of the main lines influenced the indicators of fat and milk content of first-calf heifers in the conditions of the breeding farm "ES "Streletskoye" (Table 4).

The live weight of cows of the main lines for the second lactation did not have significant differences.

Table 4 – Content of fat and protein in milk of first-calf heifers of the main lines for 305 days of lactation

Bull line	n	Fat content		Protein content
		%	kg	%	kg
Vis Back Ideal	161	4.40±0.02	215.8±2.31	3.09±0.01	151.4±6.47
Montviс Chieftain	33	4.30±0.06	263.6±2.61***	3.07±0.01	189.3±4.71***
Reflection Sovereign	108	4.26±0.03	297±2.37***	3.07±0.01	214.7±5.42***

Notes: *** – Р ≤ 0.001.

As follows from the results of the studies presented in Table 4, the higher milk yield in 305 days of lactation, which characterized the cows of the Montviс Chieftain and Reflection Sovereign lines, had a decisive effect on the predominant amount of milk fat and milk protein received by them in the first, second and third lactation, in comparison with cows of the Vis Back Ideal line.

Thus, first-calf heifers of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the Vis Back Ideal cows in terms of AMF and AMP by 22.137.5% and 25.0-41.8%, respectively (P≤0.001). In turn, Reflection Sovereign first-calf heifers outperformed the AMF and AMP indicators of Montviс Chieftain first-calf heifers by 12.7 and 13.4% (P≤0.001). It should be noted that the percentage of fat and protein in the milk of first-calf heifers of the main line did not reveal significant differences.

The content of fat and protein in the milk of cows of the main lines for 305 days of the second lactation are presented in Table 5.

Table 5 – Content of fat and protein in milk of cows of the main lines for 305 days of second lactation

Bull line	n	Fat content		Protein content
		%	kg	%	kg
Vis Back Ideal	128	4.21±0.04	225.9±2.77	3.09±0.01	164.4±3.11
Montviс Chieftain	33	4.22±0.05	256.7±3.48***	3.11±0.01	190.2±6.86***
Reflection Sovereign	50	3.90±0.07	276.5±2.62***	3.11±0.01	217.4±4.13***

Notes: *** – Р ≤ 0.001.

The analysis results shown in Table 5 indicate that the AMF and AMP acquired from the Montviс Chieftain and Reflection Sovereign cows for 305 days of the second lactation were significantly higher than those obtained from the Vis Back Ideal cows by 13.7-22, 4% and 15.7–32.3% (P≤0.001). At the same time, the indicators of AMF and AMP of Reflection Sovereign cows were higher than those of Montviс Chieftain cows by 7.8– 14.2% (P≤0.001). On the other hand, the percentage of fat in the milk of Montviс Chieftain heifers was significantly higher than in the milk of Reflection Sovereign cows by 8.2% (P≤0.001). As for the percentage of protein in milk, as well as in the case of first-calf heifers, no significant differences were found between the cows of the three lines.

The fat and protein content in the milk of cows of the main lines for 305 days of the third lactation, in general, confirms the results obtained for the two previous lactations (Table 6).

Table 6 – Content of fat and protein in milk of cows of the main lines for 305 days of third lactation

Bull line	n	Fat content		Protein content
		%	kg	%	kg
Vis Back Ideal	72	4.11±0.06	206.5±2.55	3.11±0.01	155.9±1.98
Montviс Chieftain	21	3.91±0.05	241.8±3.19***	3.11±0.01	192.2±0.91***
Reflection Sovereign	33	3.71±0.05	261.6±3.35***	3.11±0.01	219.8±2.89***

Notes: *** – Р ≤ 0.001.

In particular, the amount of milk fat and milk protein obtained from the Montviс Chieftain and Reflection Sovereign cows significantly exceeded those of Vis Back Ideal cows by 17.1-26.7% and 23.3-40.9% (P≤0.001).

At the same time, the percentage of fat in the milk of Vis Back Ideal cows exceeded those of the Montviс Chieftain and Reflection Sovereign cows by 5.1 and 10.8 percent, respectively (P≤0.001).

Breeding work intended for developing one trait without taking into account others can lead to a decline in productivity and a drop in the competitiveness of production. Therefore, when studying any trait, it is necessary to consider the existing correlations.

In our studies, we studied the correlation (r) between the main characteristics of productivity depending on the linearity of cows. Features of the correlation dependences between milk yield for 305 days of lactation and the mass fraction of fat and protein are presented in Table 7.

Table 7 – Correlation of productivity indicators of cows of the main lines with milk yield for 305 days of lactation

Index	Line	Lactation
		1	2	3
Live weight, kg	Vis Back Ideal	0.12	0,20	0,14
	Montviс Chieftain	0,11	0,13	0,23
	Reflection Sovereign	0,20	0,15	0,06
AMF, kg	Vis Back Ideal	0.89***	0.36*	0.90***
	Montviс Chieftain	0.32*	0.29	0.08
	Reflection Sovereign	0.63***	0.15	0.77***
AMP, kg	Vis Back Ideal	0.99***	0.45**	0.99***
	Montviс Chieftain	0.81***	0.84***	0.76***
	Reflection Sovereign	0.97***	0.99***	0.98***

Notes: *** – Р ≤ 0.001; ** – Р ≤ 0.01; * – Р ≤ 0.05.

In Holsteinized black-and-white cows of the main lines (bred in the "ES "Streletskoye"), no strong correlation was discovered between the live weight of cows and milk yield for 305 days of lactation. The range of indicators was 0.06-0.23. In other words, live weight affects the milk production of cows by 6.0-23.0 percent. The remaining percentages of influence are related to factors not considered in this study (feeding and other technological factors).

On the other hand, the indicators of the correlation between the amount of milk fat and milk protein produced in cows of all studied groups, with some exceptions, were closely correlated with milk yield over 305 days of lactation.

The highest positive correlation coefficients between the amount of milk fat and milk yield for 305 days of lactation were found in cows of the Vis Back Ideal line - from 0.36 to 0.90 (P≤0.05-0.001). Regarding the correlation between the amount of milk protein and milk yield for 305 days of lactation, cows of all studied groups showed high levels of interdependence, characterized by a high degree of reliability – from 0.45 to 0.99 (P≤0.01-0.001).

At the final stage of the study, we calculated the economic efficiency of breeding cows of the main lines (Table 8).

Table 8 – Efficiency of milk production in dairy cows of the main lines for 305 days of lactation (per 1 head)

Index	Cow line
	Vis Back Ideal, n = 161	Montviс Chieftain, n = 33	Reflection Sovereign, n = 108
First Lactation
Milk yield for 305 days with basic fat content*, kg	6347	7753	8735
Cost of milk of base fat content for 305 days of lactation, thousand rubles **	166,3	203,1	228,9
Second Lactation
Milk yield for 305 days with basic fat content*, kg	6644	7550	8132
Cost of milk of base fat content for 305 days of lactation, thousand rubles **	174,1	197,8	213,1
Third Lactation
Milk yield for 305 days with basic fat content*, kg	6074	7112	7694
Cost of milk of base fat content for 305 days of lactation, thousand rubles **	159,1	186,3	201,6
The total cost of milk of basic fat content produced in 305 days of the first three lactations, thousand rubles **	499,5	587,2	643,6

Notes:* Basic fat content of milk in the Orel region – 3.4%. ** The average purchase price of 1 kg of milk with basic fat content during the experiment was 26.2 rubles.

As seen in the materials presented in Table 8, the total cost of base fat milk produced in 305 days of the first three lactations by Montviс Chieftain and Reflection Sovereign cows (per head) exceeded the cost of milk produced by Vis Back Ideal cows, respectively, by 87,7 and 144,1 thousand rubles.

Conclusions. 1. Milk yield of first-calf heifers of the Montviс Chieftain line, as well as of the Reflection Sovereign line, surpassed the milk productivity of first-calf heifers of the Vis Back Ideal line by 25.3 and 42.3%, respectively (P≤0.001). On the other hand, first-calf heifers of the Reflection Sovereign line significantly exceeded the milk yield of first-calf heifers of the Montviс Chieftain line by 13.6% (P≤0.001). Milk production coefficient of first-calf heifers of the Montviс Chieftain and Reflection Sovereign lines outperformed those of the Vis Back Ideal line by 27.1% and 42.0% (P ≤ 0.001). In turn, Reflection Sovereign first-calf heifers also surpassed first-calf heifers of the Montviс Chieftain line by 11.7% (P ≤ 0.001).

• 2.    Milk yield for 305 days of the second lactation of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the milk yield of the Vis Back Ideal cows by 15.5% and 32.0% (P≤0.001). In turn, the Reflection Sovereign cows significantly exceeded the Montviс Chieftain cows in this regard by 14.3% (P≤0.001). Similarly, in terms of the milk production coefficient, the cows of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the Vis Back Ideal cows by 13.4% and 31.3% (P≤0.001). In addition, a significant superiority was shown in relation to the milk production coefficient of Reflection Sovereign cows over Montviс Chieftain cows by 15.8% (P≤0.001).

• 3.    The milk yield in 305 days of the third lactation of cows of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the milk yield of the Vis Back Ideal cows by 23.0% and 40.4% (P≤0.001). In turn, the Reflection Sovereign cows significantly exceeded the Montviс Chieftain cows in this indicator by 14.1% (P≤0.001). In terms of milk production, the cows of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the Vis Back Ideal cows by 18.4% and 38.7% (P≤0.001). In addition, a significant superiority was shown in relation to the milk production coefficient of Reflection Sovereign cows over Montviс Chieftain cows by 17.2% (P≤0.001).

• 4.    The live weight of cows of the main lines in the first and second lactation did not have significant variations. The live weight of cows of the Montviс Chieftain line in the third lactation significantly exceeded Vis Back Ideal by 3.8% (P≤0.05).

• 5.    First-calf heifers of the Montviс Chieftain and Reflection Sovereign lines significantly exceeded the Vis Back Ideal cows by 22.1-37.5% and 25.0-41.8%, respectively (P≤0.001). In turn, Reflection Sovereign first-calf heifers outperformed the AMF and AMP of Montviс Chieftain first-calf heifers by 12.7-13.4% (P≤0.001). The percentage of fat and protein in the milk of first-calf heifers of the main line did not show significant differences.

• 6.    AMF and AMP obtained from cows Montviс Chieftain and Reflection Sovereign for 305 days of the second lactation were significantly higher than the same indicator obtained from cows of the Vis Back Ideal line by 13.7-22.4% and 15.7-32.3% (P≤0.001). At the same time, the indicators of AMF and AMP of Reflection Sovereign cows were higher than those of Montviс Chieftain cows by 7.8 and 14.3% (P≤0.001). The percentage of fat in the milk of Montviс Chieftain first-calf heifers was significantly higher than that in the milk of Reflection Sovereign first-calf heifers by 8.2% (P≤0.001).

• 7.    The amount of milk fat and milk protein obtained from cows Montviс Chieftain and Reflection Sovereign significantly exceeded the indicators of Vis Back Ideal cows by 17.1-26.7% and 23.3-40.9% (P≤0.001). The percentage of fat in the milk of Vis Back Ideal cows exceeded those of the Montviс Chieftain and Reflection Sovereign cows by 5.1 and 10.8 percent, respectively (P≤0.001).

• 8.    The highest positive correlation coefficients between the amount of milk fat and milk yield for 305 days of lactation were found in cows of the Vis Back Ideal line - from 0.36 to 0.90 (P≤0.05-0.001). Concerning the relationship between the amount of milk protein and milk yield for 305 days of lactation, cows of all studied groups showed high levels of interdependence, characterized by a high degree of reliability – from 0.45 to 0.99 (P≤0.01-0.001).

• 9.    The total cost of base fat milk produced in 305 days of the first three lactations by Montviс Chieftain and Reflection Sovereign cows (per head) exceeded the cost of milk produced by Vis Back Ideal cows by 87.7 and 144.1 thousand rubles, respectively.