Postnatal Muscle Growth and Allometry in Anatomical Regions of Russian Black-Pied Heifers and their Crosses With Hereford and Charolais Under Intensive Rearing

Crossbreeding dairy cattle with specialized beef breeds is an effective strategy to increase beef production, yet data on muscle growth patterns in crossbred heifers remain limited. This study aimed to evaluate the growth intensity and redistribution of muscle mass in anatomical regions of carcasses in Russian Black-Pied heifers and their crosses with Hereford and Charolais breeds. A scientific experiment was conducted on three groups of heifers (n = 15 per group) from birth to 18 months of age: Group 1 (control) – Russian Black-Pied; Group 2 – ½ Hereford × ½ Russian Black-Pied; Group 3 – ½ Charolais × ½ Russian Black-Pied. Live weight was recorded monthly. Control slaughters were performed at birth, 6, 12, and 18 months. Layer-by-layer dissection of half-carcasses was performed to determine the absolute and relative muscle mass of anatomical regions. Growth coefficients and relative growth rates were calculated. Charolais crossbred heifers surpassed their maternal breed contemporaries in live weight by 9.0–12.5% (P<0.01–0.001) and in absolute carcass muscle mass by 10.1–29.3%. The highest growth intensity was observed in the abdominal wall musculature, followed by the pelvic girdle and serratus ventralis muscle group (positive allometry). The lowest growth rates were recorded for the antebrachium, crus, brachium, thigh, and pectoral girdle (negative allometry). Redistribution of muscle mass was evidenced by an increase in axial musculature relative mass from 43.8% at birth to 48.9% at 18 months, with a corresponding decrease in peripheral musculature from 54.0 to 48.1%. The intensive growth of the abdominal wall musculature is attributed to constant gravitational pressure from internal organs, while the lower growth rates of locomotor muscles reflect their higher maturity at birth. These findings provide insights into muscle development patterns in crossbred heifers and support the use of Charolais genetics for beef production.