Construction of regional breeding indices for cows of the Ayrshire population of the Russian Federation

An assessment of the Estimation Breeding Value (EBV) of Ayrshire first-calving cows was carried out using the BLUP Animal Model, followed by the modeling of breeding indices and the calculation of weight coefficients, taking into account the segmentation of animal groups by breeding regions. As a result of the assessment of breeding value, differences were established for certain economically useful traits in the studied populations of first-calving cows. In the group of cows from the Republic of Karelia (KRL), estimates for milk yield for 305 days (MY) were +263 kg, fat yield (FAT) +9.2 kg, protein yield (PROT) +8.7 kg. Animals from the Leningrad region (LO) had the most desirable reproduction scores: days open (DO) and Intercalving period (ICP) were at the level of -0.15 and +0.08 days, respectively. The fertility index (FI) turned out to be at the level of +0.19, yielding in value only to first-calving cows from the KRL, whose estimates were +0.31. A negative genetic relationship between MY and the percentage of fat and protein (rg = -0.100, rg = -0.096) and a low phenotypic relationship (rp = +0.013, rp = +0.168, respectively), were revealed. The phenotypic correlation of MY with live weight at 10 months (W10) was +0.351, which is higher compared to other signs of development. The heritability coefficients of developmental indicators, such as W10, live weight at the first insemination (W1INS) and after the first calving (W1C) had insignificant differences between themselves and amounted to: 0.17, 0.20 and 0.18, respectively.  On the basis of phenotypic and genetic correlation coefficients and heritability coefficients of the studied traits, on average for the population, a general index was used, and taking into account differences in regions, regional indices were developed. The main difference between the presented indices is the values of weight coefficients. In the Republic of Komi, in comparison with other regions, MY for 305 days (+54.94) and FI (+0.90) take more weight, in the Siberian Federal District (SFO) - FAT (+12.98), in the Southern Federal District (SFO) - PROT (+26.9), and in the index for the LO - the indicator W10 (+0.50). The values of weight coefficients for W10 differ between regions not only in terms of values, but also in direction. According to this indicator, negative weighting coefficients were noted in the Vologda (-0.30), Kirov regions (-0.10) and the Southern Federal Districts (-0.10). In the KRL, there is a greater need to work with the reproductive qualities of animals, as indicated by the weight coefficient for the fertility index equal to +0.25.