Research has shown that enhancing finishing performance in beef cows is feasible; however, any adverse impact of selection strategies for finishing performance on the performance of the maternal herd should be taken into account. The aim of this research was to examine the inheritance of growth, ultrasound and carcass traits in finishing beef cattle and to evaluate their correlations with maternal performance traits. Data were collected from a nationwide progeny test on commercial New Zealand hill country farms comprising a total of 4473 beef cows and their progeny. Most finishing traits were moderately to highly heritable (0.28–0.58) with the exception of meat or fat colour and ossification (0.00–0.12). Ultrasound scan traits had high genetic correlations with corresponding traits measured at slaughter (r_g = 0.53–0.95) and may be used as a selection tool for improved genetic merit of the beef carcass. Fat content determined via ultrasound scanning in the live animal or at slaughter in finishing cattle is positively genetically correlated with rebreeding performance (r_g = 0.22–0.39) in female herd replacements and negatively correlated with mature cow live weight (r_g = −0.40 to −0.19). Low-magnitude associations were observed between the genetic merit for carcass fat traits with body condition in mature cows.

Maternal performance is a major driver of profitability in cow-calf beef cattle enterprises. The aim of this research was to evaluate the inheritance of maternal performance traits and examine the intercorrelation among reproduction, live weight, hip height, body condition and maternal contribution to calf weaning weight in 15-month-old heifers, 2-year-old cows and mature cows in New Zealand beef herds. Data were collected on a total of 14,241 cows and their progeny on five commercial New Zealand hill country farms. Heritabilities were low for reproductive traits in heifers and mature cows (0–0.06) but were greater in 2-year-old cows (0.12–0.21). Body condition scores were lowly (0.15–0.26) and live weights (0.42–0.48) and hip heights (0.47–0.65) highly heritable in heifers, 2-year-old cows and mature cows. Results indicate that 2-year-old cows with higher genetic potential for rebreeding ability may have greater genetic merit for live weight, hip height and body condition as heifers (r_g = 0.19–0.54) but are unlikely to be larger cows at maturity (r_g = −0.27–−0.10). The maternal genetic effect on weaning weight had a heritability of 0.20 and was negatively genetically correlated with body condition score in lactating cows (r_g = −0.55–−0.40) but positively genetically correlated with rebreeding performance (r_g = 0.48).

Extensive farming systems require beef cows to cope with varying environmental conditions while repeatedly producing calves. Cows use body energy reserves as a buffer in times of feed shortage and replenish reserves under a feed surplus. The aims of the research were to (1) quantify live weight (LW) and body condition score (BCS) fluctuations among farms, years and over the production cycle (mating, weaning and calving) and to (2) quantify the relationship between LW and BCS at mating, weaning and calving, for cows of different hip heights. A total of 7,649 individual cow records from nine commercial New Zealand farms with information on LW and BCS (1–10 scale, 1 = emaciated and 10 = obese) were analysed. Analyses revealed significant ( P < 0.001) within‐year variation in mean LW (32.4–77.2 kg) and BCS (0.4–1.8 scores) profiles among farms, but profiles were not consistent from year to year. There was a quadratic relationship ( P < 0.001) between LW and BCS, such that one unit change in BCS corresponded to 15.1 kg LW increase at BCS 4–5 compared to 41.1 kg LW increase at BCS 8–9 at mating. This relationship was similar, irrespective of hip height.

The proceedings of the 12th World Congress on Genetics Applied to Livestock Production provide you with 816 papers representing the leading research in livestock genetics around the globe. This boo...