By Abigail Frazer

The inclusion of new traits, such as body condition score and locomotion, into breeding goals, is being considered as a potential solution to prevent the worsening of health and fertility in Holstein-Friesian dairy cows. Evaluation of these traits in terms of their heritability, ease of measurement and genetic correlation with health, reproduction and condition will be paramount to ensure their future implementation in breeding programmes.

It is well known that traditional selection of Holstein-Friesian dairy cows for increased milk production has inadvertently resulted in a decline in the health and fertility of such cows. In recent years, there has been increased emphasis on the inclusion of functional traits in breeding goals in an attempt to improve reproduction and health, while simultaneously reducing involuntary culling of animals. The measurement of such traits is however often difficult and extremely subjective, with many of them having low heritability and therefore little potential to ultimately improve health and fertility.

Locomotion is a trait that describes the quality of a cow’s gait and has a role in determining lameness, which is a major concern on dairy farms with severe consequences on milk yield, reproductive performance, and welfare. Diseases of the legs and feet are also highly prevalent among dairy farms, causing significant economic losses due to involuntary culling of chronically lame animals. Body condition score is a trait that measures body tissue reserves and can be used to predict the fertility, health, and welfare of cows. Body condition score is thought to have high genetic variability and is strongly correlated with breed and other conformation traits, making it ideal for use in selection indices. Overall, locomotion and body condition score are among the main traits with links to fertility and health, hence the interest to include them in breeding programme criteria.

In a recent study, data on over 300,000 Holstein-Friesian cows was collected, with evaluation of body condition score and locomotion performed by trained classifiers using 9-point scales. All cows were body condition scored from 1 being very thin to 9 being very fat – the optimum value was 5 being intermediate. 43% of cows were evaluated for locomotion from 1 being lame (severe abduction and short stride) to 9 being normal (no abduction and long stride) – the optimum value. Genetic parameters were estimated, and breeding values calculated using the same model. Genetic trends were then extrapolated.

The aims of this study were to estimate the genetic parameters for body condition score and locomotion, while assessing how such traits interact with other traits, and it did so successfully. Body condition score was found to have moderate heritability (0.19) with genetic correlation to fertility, while locomotion was found to have low heritability (0.06) and strong genetic correlation to feet and leg traits.

Overall this study demonstrated that the inclusion of body condition score and locomotion in breeding criteria could contribute to more effective cattle selection, in order to ultimately improve fertility and feet and leg traits respectively in dairy cattle.

Abigail Frazer is an Animal Science graduate from Newcastle University and undergraduate Veterinary Medicine student at the University of Nottingham.

References

Jagusiak, W., Ptak, E., Otwinowska-Mindur, A. & Zarnecki, A., 2023. Genetic relationships of body condition score and locomotion with production, type and fertility traits in Holstein-Friesian cows. Animal, 17(6)