RESEARCH ▶▶▶
time. High prevalence of bimodality in milk flow trait may indicate poor health. In this study, the analysis showed that the bimodality of the milk flow was statistically significantly associated with the health status of cows. The prevalence of bimodality of milk flow was 23.3% for the healthy cows, whereas for the lame cows it was 56.4%. This observation was attributed to the increased stress in lame cows that affects the milking process, resulting in weaker stimulation of the milk ejection reflex.
Blood cortisol concentration Cortisol concentration in the animal can be a valuable bio- marker of chronic stress. Pain experienced from lameness could act as a stressor in dairy cattle. Adverse stressors trigger responses of the adrenal glands, which in turn increases glucocorticoid concentrations, resulting in high production
Table 1 – Milk yield (kg) traits of cows by health status.
Variable Total milk yield (kg/milking)
Milk yield during first minute (kg) Milk yield during first 2 minutes (kg) Milk yield during first 3 minutes (kg)
40
Healthy group 17.14 2.28 5.38 8.33
Lameness group 15.37 1.94 4.96 7.84
▶ DAIRY GLOBAL | Volume 8, No. 3, 2021
of cortisol. In this study, the risk of lameness was clearly in- dicated by an increase in blood cortisol concentration: if this level in cows exceeded 1 µg/dL, the likelihood of identifying lameness increased by 4.9 times. The level of blood cortisol in the healthy group was lower than that in the lameness group. The researchers emphasised that the significantly higher levels of plasma cortisol concentration in the lameness group can be associated with stress experienced by those animals and their more pronounced reactions to the milking process. They added that the negative relationship between milk yield and blood cortisol concentration in the lame cows could be attributed to the deteriorating health and welfare of the animals due to the lameness. Blood cortisol concentra- tion was positively associated with lameness as well as with bimodality of the milk flow curve.
Conclusion The researchers concluded that milk flow traits can act as bio- markers of lameness in dairy cows. When multivariable binary logistic regression analysis was conducted, it was shown that blood cortisol concentration, total milk yield and bimodal- ity of the milk flow curve can be used to predict lameness early. Of all the parameters studied, the risk of lameness was most clearly indicated by an increase in blood cortisol con- centration; if this level exceeded 1 µg/dL, the likelihood of identifying lameness increased by 4.9 times.
PHOTO: MARK PASVEER
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