Abstract
Background:
Dairy and beef cull cows contribute substantially to beef production, yet their carcass and meat quality vary with genotype and post-mortem handling.

Aim:
This study evaluated the effects of genotype and post-mortem aging on the carcass characteristics and meat quality traits of cull cows slaughtered at a commercial abattoir in South Africa.

Methods:
Eighty-one C-age class cows (>6 tooth), with an average live slaughter weight (LSW) of 593.7 ± 79.0 kg, were sampled, comprising Holstein-Friesian (n = 24), Bonsmara (n = 31), and South Devon × Aberdeen Angus (SD × AA) crossbreed (n = 26) genotypes. Beef steaks from each genotype were subjected to post-mortem aging for 2, 7, and 14 days.

Results:
The mean warm carcass weight was 292.9 ± 37.5 kg. Dressing percentage was significantly lower (p = 0.01) in Holstein-Friesian (49.1%) than in Bonsmara (51.3%) and SD × AA (51.2%) cows. Genotype was associated with fatness score (p = 0.0228) and conformation scores (χ2 = 32.17, p < 0.0001), with Bonsmara and SD × AA carcasses displaying superior muscling. Ultimate pH was higher (p < 0.001) in Bonsmara (5.56) and Holstein-Friesian (5.54) than in SD × AA crossbred cows (5.35). Holstein-Friesian beef exhibited greater drip loss (4.86%) compared to Bonsmara (2.77%) and SD × AA crossbreed (3.20%) beef (p < 0.05). The SD × AA crossbred beef demonstrated superior color stability during aging, retaining higher redness (a*) and chroma values and lower total color change (ΔE). Warner–Bratzler shear force (WBSF) declined from 97.5 to 59.3N (SD × AA), 102.1 to 63.2N (Holstein-Friesian), and 115.8 to 71.2N (Bonsmara) between days 2 and 14 post-mortem. Strong correlations were observed between LSW and carcass weight (r = 0.95, p < 0.001) and between drip loss and WBSF (r = 0.81, p < 0.05).

Conclusion:
Genotype and post-mortem aging significantly affected the carcass and meat quality traits of cull cows. The superior color stability and lower shear force values of SD × AA beef suggest its greater suitability for premium fresh beef markets. These findings provide valuable insights into the minimum expected carcass and meat quality attributes of cull cows, highlighting the importance of genotype-specific post-mortem
handling to optimize beef quality.