Tracking the changes of carcass traits in beef animals

Shauna Mulhall, Teagasc Moorepark, discusses research work which examined data from approximately 23 million animals born between 1986 and 2020 to track the changes in carcass traits of beef and dairy animals.

The beef industry plays a vital role in the Irish economy, so it is important to focus on improving the quality of beef animals and increasing their efficiency to ensure the sustainability of the sector.

In recent years, due to the expansion of the dairy herd, over half of the animals slaughtered for beef production originate from dairy herds. Therefore, there has been particular interest in evaluating the impact of dairy cow breeding programmes on the beef merit of their offspring. A recent study examined the trends in carcass traits of different cattle genotypes: dairy, dairy-beef and suckler animals.

Using data from the national database maintained by the Irish Cattle Breeding Federation (ICBF), approximately 23 million animals born between 1986 and 2020 were used to estimate the trends for carcass traits in beef animals.

Key findings of the study

Figure 1. Genetic trends in beef merit by year of birth for the offspring of a dairy dam and a dairy sire (yellow line), the offspring of a dairy dam and a beef sire (red line), and the offspring of a beef dam and beef sire (blue line).

This study also estimated the breed composition for each genotype within the national population. Dairy animals were primarily composed of Holstein Friesian breeds (92%). The proportion of Friesian has increased from 14% in 2000 to 25% in 2018. In relation to dairy-beef animals, there are five main beef breeds, as well as the proportion of dairy breed composition. The combined proportion of Limousin, Belgium Blue and Charolais has decreased by 16 percent units in dairy-beef animals since 2002, while both Aberdeen Angus and Hereford represent a larger proportion of dairy-beef animals, with an increase of 17 percent units. Since the year 2000, there has been an increase in the proportion of Limousin (10 percent units) and a decline in Charolais (10 percent units) breed composition of beef coming from the suckler herd.

Trends for suckler animals

Suckler-bred animals showed an increase of 11kg in genetic merit for carcass weight and an increase of 0.5 units in genetic merit for carcass conformation (i.e. muscle development) from 2008 to 2018 (Figure 1). In addition, animals showed a slight declining genetic trend for fat score. Actual carcass weight and conformation score observed nationally changed similarly to the genetic trends, while also significantly reducing the age at slaughter over the 10 year period: 30 days for steers, 38 days for heifers and 53 days for young bulls.

Trends from dairy animals

 In contrast, over the same 10 year period, dairy animals showed a decrease of 4.7kg in genetic merit for carcass weight and a decrease 0.2 units in genetic merit for carcass conformation. The genetic merit for carcass weight of dairy-beef animals was relatively constant over the 10 years, while the conformation score breeding values reduced each year (0.5 units decrease over the 10 years; Figure 1).

Interestingly, within the individual breeds the carcass traits were actually improving. The decline in carcass traits was primarily due to an increased proportion of Aberdeen Angus and Hereford within the population compared to continental breeds. However, the decline in actual carcass weight was not noticeable for both dairy and dairy-beef animals, suggesting that improvements in management and nutrition have masked the genetic decline. Nevertheless, the actual carcass conformation data showed a similar decline as suggested by the genetic trend for both dairy and dairy-beef.

Conclusions

• Current breeding programmes have had a favourable impact on carcass traits for suckler animals, but unfavourable trends were observed for dairy and dairy-beef animals.
• The decline in genetic merit for carcass traits in animals of dairy origin may be attributed to the higher emphasis on other economically important traits, such as milk production and fertility, in breeding programmes for dairy cows. Addressing the declining genetic trends in carcass traits for animals of dairy origin is important while still considering the economic priorities of the dairy industry.
• The results indicate that genetic and actual observable trends for carcass weight and carcass conformation are increasing, while carcass fat is declining for suckler animals.
• Animals originating from dairy herds are declining in genetic merit for carcass weight and carcass conformation, although this was not as apparent in actual carcass data.
• If the genetic trends of dairy and dairy-beef animals continue to decline, it will have a negative impact on the overall beef merit of the national cattle population.
• The reduction in age at slaughter is beneficial, as it will help reduce the environmental impact of beef animals and improve the profitability in beef herds.
• Advancements in genomics and reproductive techniques, such as sexed semen, can contribute to more efficient selection and improved genetic gain for carcass traits in the future. These advances should also allow for greater usage of high DBI (Dairy Beef Index) beef sires to help improve the overall beef merit of beef animals produced from the dairy herd going forward.
• Continuous monitoring of trends in animals subjected to intensive genetic selection is essential to enhance carcass traits and ensure the long-term sustainability and profitability of the Irish beef industry.

As part of her PhD studies, Shauna’s work in this field was recently published in the Irish Journal of Agriculture and Food Science. Access the full scientific paper here.