Associating mobility scores with production and reproductive performance in pasture-based dairy cows.

In some countries lameness has been identified as the third most important health-related economic loss, after fertility and mastitis. Lameness has serious negative consequences on animal welfare and the environment. Secondly, lameness may reduce the overall lifetime performance of dairy cows due to milk production loss and culling, as well as having the potential to further affect sustainability by increasing the total greenhouse gas emissions per unit of milk produced. Furthermore, lame cows are more at risk for developing future mobility issues. Clinical lameness in systems other than spring calving, pasture-based systems has been shown to be negatively associated with milk yield, reproductive performance and additional labour. Treatment costs show substantial yield losses for up to five months before a farmer diagnose a claw disorder. The consequences of lameness, especially more severe types of lameness, have been well researched for several management systems, such as year-round housing and non-seasonal calving pasture-based systems. However, relatively fewer studies have examined the effect of less severe or mild types of lameness in spring-calving, pasture-based systems. To determine the economic and environmental consequences of lameness, Dr A. H. O’Connor and colleagues in their study first needed to quantify the effect of lameness on performance. The objective of their study, therefore, was to determine the associations of various production and reproductive performance measurements including milk, fat, and protein yield, somatic cell count, calving interval, cow death, or cow slaughter, and mobility scores in spring-calving, pasture-based dairy cows. Their study was published in the Journal of Dairy Science, Volume 103 of 2020, page 9238 to 9249, the title being: Associating mobility scores with production and reproductive performance in pasture-based dairy cows. 

The researchers collected mobility scores (0 = good, 1 = imperfect, 2 = impaired, and 3 = severely impaired mobility), body condition scores, and production data for 11 116 cows from 68 pasture-based dairy herds. Linear mixed modelling was used to determine the associations between specific mobility scores and milk, fat and protein yield, and somatic cell count and calving interval. Binomial logistic regression was used to determine the association between mobility score and cow death, or slaughter. 

The results showed that yield losses of up to 1.4% of the average yield were associated with a mobility score of 2 and yield losses of up to 4.7% were associated with a mobility score of 3 during the early scoring period. Elevated somatic cell count was associated with all levels of suboptimal mobility during the late scoring period. Cows with a mobility score of 2 during the early scoring period were associated with longer calving intervals, whereas only cows with a mobility score of 3 during the late scoring period were associated with longer calving intervals. Cows with a mobility score ≥1 were more likely to be culled during both scoring periods.

In summary, the study shows that suboptimal mobility in spring calving, pasture-based systems has negative associations with production (milk, fat and protein yield, and SCC) and reproductive performance (calving interval), as well as being associated with a higher risk for premature culling. The results of the study are in agreement and comparable with other dairy management systems, such as confinement type systems and year-round calving, pasture-based systems. Spring calving, pasture-based systems are based on low inputs and low outputs where cost control is paramount to the success of the system. Therefore, preventable losses associated with sub-optimal mobility have significant economic impact, despite the prevalence of sub-optimal mobility in such systems being relatively lower than in other systems.