Estimation of breeding value and genetic dynamics of economically useful traits of sheep of the southern meat breed

Introduction. The study of genetic dynamics of economically useful traits to improve the quality of breeding work has recently become an important task in animal husbandry [5, 6]. For this purpose, an assessment of the breeding value of animals is used based on statistical linear models. The most informative method is BLUP (Best Linear Unbiased Prediction) [3]. If animals have different information on their parents, the most accurate and effective will be the use of the BLUP Animal Model, which will increase the accuracy of the forecast for assessing the breeding value of animals, and therefore the reliability of the selection of the best individuals for herd reproduction will increase [4].

In connection with the above-mentioned relevance, the purpose of this work was to obtain estimates of breeding value using the BLUP Animal Model method for further selection of the best sheep of the southern beef breed into the breeding core of the herd.

Materials and methods. The study was carried out at the Ladozhsky breeding plant (Krasnodar region, Ust-Labinsk region, Vimovskoye rural settlement, Vimovets village) on purebred sheep of the southern meat breed (n=441). The information on measuring wool and meat productivity for 2022 and 2023 was obtained from the SELEX database and preliminary data processing was aimed at eliminating various empty records and errors.

The estimation of breeding value was carried out using the BLUP Animal Model program. For each EBV indicator, its own model was formed [1, 2, 7].

• 1)    Live weight indicator:

BW = v + ES + TY + sex + b 1 RW + a + e (1)

• 2)    Wool length indicator:

WL= v + TY + sex + b 1 WW + a + e (2)

• 3)    Wool thickness indicator:

WT = v + Sex + WL + a + e (3)

• 4)    Indicator of the amount of wool washed:

WW = v + WT_6ann + b 1 WL + b₂BW + a + e (4)

where: BW – live weight, kg; WL – wool length, cm; WT – wool thickness, µm; WW – amount of wool washed, kg; μ – population constant, ES – earliness, TY – year of valuation, sex – sex, RW – greasy wool clip, a – randomized effect of the animal under normal distribution with variation Ao ^ (A - additive kinship matrix); e - effect of unaccounted factors.

Results and discussion. When analyzing the average values, the studied indicators had the following characteristics: live weight 59.13 kg, wool length 13.04 cm, wool thickness 27.9 microns and the amount of wool washed 2.58 kg.

To obtain the reliable estimation of breeding value, we first calculated the genetic relationships between traits (table 1).

Table 1 – Genetic correlation of the studied indicators of live weight and wool quality

	BW	WL	WT	WW
BW	1
WL	-0,251	1
WT	0,112	-0,189	1
WW	-0,492	0,156	-0,002	1

Note: BW – live weight, kg; WL – wool length, cm; WT – wool thickness, µm; WW – amount of wool washed.

According to table 1, live weight and wool thickness, as well as the amount of wool washed and wool thickness have a low positive level of correlation. A low negative level of correlation was found between body weight and wool length, wool length and wool thickness, and between wool thickness and the amount of wool washed. The largest negative correlation is between live weight and the amount of wool washed (r g =-0.49).

In the course of our work, when calculating the EBV indicators for each individual: live weight, wool length, wool thickness, amount of washed wool, the best 15 sheep of the southern meat breed were selected (table 2).

Table 2 – Top 15 individuals selected according to breeding value estimates based on live weight of the southern beef sheep

№	BW	WL	WT	WW
1	+9,51	-1,82	+0,39	-0,48
2	+7,32	-0,14	+1,47	-0,05
3	+6,55	+0,04	+0,71	-0,12
4	+5,93	+1,88	+0,75	-0,16
5	+5,88	-0,85	+0,22	-0,37
6	+5,53	-1,08	+0,30	+0,03
7	+5,17	-1,35	+0,63	+0,02
8	+4,83	-1,24	+0,40	+0,02
9	+4,75	+0,62	-0,46	-0,09
10	+4,54	-0,56	-1,46	-0,26
11	+4,52	-1,78	+0,87	-0,17
12	+4,30	-1,80	+0,45	-0,47
13	+4,20	+0,89	-0,27	-0,20
14	+4,17	-0,94	+0,46	+0,08
15	+4,13	+0,08	-0,10	-0,43

Note: BW – live weight, kg; WL – wool length, cm; WT – wool thickness, µm; WW – amount of wool washed

As it can be seen from Table 2, individuals with the highest estimation of breeding value in terms of live weight have positive or negative estimates for the other three indicators, which confirms the need for selection for this trait.

Conclusion. A calculation of the genetic correlation pleiades between the studied traits was carried out, as a result of which, for the first time, the equations were modeled and results were obtained for estimating the breeding value of sheep of the southern meat breed in terms of wool quality and live weight. The selection of the best individuals was based on BW. As a result, 15 of the best animals are presented that have promising genetic modifications so that in the future it will be possible to obtain high-quality offspring from them.

Further scientific work is aimed at refining genetic estimation using the genome-BLUP (GBLUP) methodology and developing a genomic assessment in the population of southern beef breed sheep to consolidate and grow the breeding gene pool in Russia.